Heatline method for the visualization of natural convection in a complicated cavity

In this paper, natural convection inside a two-dimensional cavity with a wavy right vertical wall has been carried out. The bottom wall is heated by a spatially varying temperature and other three walls are kept at constant lower temperature. The integral forms of the governing equations are solved numerically using finite-volume method in non-orthogonal body-fitted coordinate system. SIMPLE algorithm with higher-order upwinding scheme are used. The method of numerical visualization of heat transport for convective heat transfer by heatlines is studied. The heatfunction equation in the transformed plane is solved in terms of dimensionless variables. Results are presented in the form of streamlines, isotherms, heatlines, local and average Nusselt number distribution for a selected range of Rayleigh number (10⁰–10⁶). The results are presented for three different undulations (1–3) with different wave amplitude (0.00–0.10) and a fluid having Prandtl number 0.71.     

Experimental investigations and CFD modeling for flow of highly concentrated iron ore slurry through horizontal pipeline

Considering a large number of higher solids concentration iron ore slurry pipelines operating across the world and their associated problems, the present study aims to generate an extensive experimental dataset from the pilot plant test facility and to carry out computational fluid dynamics (CFD) simulations for better understanding of the flow behavior in such pipelines. The paper has presented experimental data of 12?µm iron-ore slurry flow cases through 105?mm pipe with flow velocity range 1.35–5.11?m/s and efflux concentration range 2.63–31%. The obtained results are validated using CFD using appropriate model. In addition, qualitative analysis of iron-ore slurry flow cases using simulated results has been presented.     

Lipids of Haloferax alexandrinus strain TM(T): an extremely halophilic canthaxanthin-producing archaeon

The core lipids, polar and non polar lipids, of the novel canthaxanthin-producing archaeon, Haloferax alexandrinus strain TM(T), were investigated using thin-layer chromatography (TLC), spectrophotometry, electron ionization-mass spectroscopy (EI-MS), fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic response spectrometry (13C-NMR) and high performance liquid chromatography (HPLC). This archaeon appeared to contain diphytanyl diether lipids (C20-C20) as core lipids. The major phospholipids were found to be phosphatidylglycero-phosphate-methyl ester (PGP-Me) and phosphatidylglycerol (PG), but no phosphatidylglycero-sulfate was detected. The strain contained two glycolipids, sulfated diglycosyl diether (S-DGD-1) and unsulfated diglycosyl diether (DGD). Analysis of the non polar lipids revealed the presence of beta-carotene, 3-hydroxyechinenone, gamma-carotene, cis-astaxanthin, lycopene, trisanhydro-bacterioruberin,monanhydro-bacterioruberin, bacterioruberin isomer, bacterioruberin and canthaxanthin. Although the polar lipids profile of Hfx. alexandrinus strain TM(T) was similar to those of other species of the genus Haloferax, the non polar lipid (carotenoids) profile was markedly different. Further experiments on the influence of NaCl concentration on the lipids composition of Hfx. alexandrinus strain TM(T) demonstrated the dependence of the proportion of each of bacterioruberin, beta-carotene and canthaxanthin on the NaCl concentration in the growth media.     

A parametric study of dispersed laminar gas-particle flows through vertical and horizontal channels

Particle diameter, particle phase material density and inlet particle volume fraction are three important parameters governing the flow physics of dispersed gas-particle flows. In this work, an inhouse numerical solver is developed to investigate the effects of particle diameter (Stokes number), particle phase material density, inlet particle volume fraction and inlet phase velocities in the flow characteristics of gas-particle flows through vertical and horizontal channels and also in open domains. It is found that, for a constant inlet particle volume fraction, lower diameter particles attain a higher steady state velocity at any section inside the channel than the higher diameter particles; while the corresponding steady state gas velocity at any section increases with increase in particle diameter. On the other hand, for a constant particle diameter, the steady state gas phase velocity at any section decreases with increase in inlet particle volume fraction. Significant changes in both gas and particle velocity and volume fraction profiles have also been observed with inlet slip, i.e., when the velocities of both the phases at inlet are distinct as opposed to being equal, keeping all other flow and physical parameters invariant.     

Determination of particle number and brightness using a laser scanning confocal microscope operating in the analog mode

We describe a method to obtain the brightness and number of molecules at each pixel of an image stack obtained with a laser scanning microscope. The method is based on intensity fluctuations due to the diffusion of molecules in a pixel. For a detector operating in the analog mode, the variance must be proportional to the intensity. Once this constant has been calibrated, we use the ratio between the variance and the intensity to derive the particle brightness. Then, from the ratio of the intensity to the brightness we obtain the average number of particles in the pixel. We show that the method works with molecules in solution and that the results are comparable to those obtained with fluctuation correlation spectroscopy. We compare the results obtained with the detector operating in the analog and photon counting mode. Although the dynamic range of the detector operating in the photon counting mode is superior, the performance of the analog detector is acceptable under common experimental conditions. Since most commercial laser scanning microscopes operate in the analog mode, the calculation of brightness and number of particles can be applied to data obtained with these instruments, provided that the variance is proportional to the intensity. We demonstrate that the recovered brightness of mEGFP, independent of concentration, is similar whether measured in solution or in two different cell types. Furthermore, we distinguish between mobile and immobile components, and introduce a method to correct for slow variations in intensity.     

通过改进转换器设计来降低能耗

全球正越来越关注能耗问题。降低能耗有两种方式，其中，节能需要个人/社会有意识的制定相关策略，而改进能效则是一种纯技术性的方式，对于终端用户是透明的。     

Applicability of four recent models to the discharge behaviour of different phases of MnO2 in alkaline and acidic/neutral electrolytes

Manganese dioxides belonging to different crystalline phases were discharged in 9 M KOH and 5 M NH₄Cl+2 M ZnCl₂ at a constant current of 1 mA 0.1 g. These phases were characterized by X-ray diffractometry and chemical analysis. Four different models were tried for their applicability to the discharge behaviour of these phases. Almost all the four models successfully predict the values of the oxyhydroxides in the first half of the reduction range 0<r<0.5, but fail to do so in the secon half i.e. 0.5<r<1. The only exception to this is the model (Model 2) of Maskell, Shaw and Tye. This model yields, by far, the best match with the experimental data in acidic/neutral electrolyte. In alkaline electrolyte, however, even this model fails to account satisfactorily for the observed potentials in the lower half of the reduction. This failure could perhaps be explained as due to the formation of a new phase at about MnO_1.6 (r0.8). The cation vacancy model of Ruetschi predicts most of the physical properties rather well but the match of the theoretical potentials with the experimental values is poor, specially in the lower half.     

Biological indicators in relation to coastal pollution along Karnataka coast, India

Marine pollutants in relation to planktonic and benthic organisms were examined at two locations along Karnataka coast, one at Kulai (74 degrees 47.74'E and 12 degrees 55.16'N) receiving huge amount of industrial effluents from fertilizer, petroleum and chemical plants along with the sewage discharges. The other site Padubidri (74 degrees 45'E and 13 degrees 10'N) is located 20 km away, which is a typically agricultural and fishing village having no stress of industrial discharges. Although the concentrations of dissolved oxygen (DO), nutrients and trace metals in water and sediment showed marginal differences at these two locations, the concentration of petroleum hydrocarbon (PHC) remained exceptionally high with a maximum of 1523 microg/l at Kulai which is 10 times higher than that at Padubidri (144 microg/l). Biomass and population of phytoplankton and zooplankton showed that the seasonal differences were more conspicuous rather than the regional changes. Macro and meiobenthic population remained high at both the locations during the two seasons. Phytoplankton species indicated that centric diatoms such as Rhizosolenia, Leptocylindricus, Chaetoceros, Thalassiosira and Coscinodiscus contributed to > 90% of population in May and > 70% in January at Kulai. While mixed population of centric, pennate, cyanophycean and dinoflagellates prevailed at Padubidri in January. Lower species diversity and richness accompanied with dominance of fast growing centric diatoms over pennates observed at Kulai act as an index for detection of organic pollution and nutrient enrichment. Similarly, proliferation of benthic bivalves > 54% at Kulai relative to Padubidri suggests that these organisms could sustain organic and industrial pollutants. The results suggest that although Kulai receives large quantities of industrial and sewage effluents responsible for alteration of the ecosystem structure, the excellent wind-driven mixing and tidal flushing keep the waters well aerated thus reducing the severe pollution stress by dispersing the organic and other pollutants. Direct relationship of PHC with Cd and Pb as contaminants, NO3 and PO4 as oxidants of excess PHC and species diversity as promoters of phytoplankton (centric diatoms) and benthic bivalves shown by multiple regression analysis further suggest that these biological parameters could serve as indicators for detecting moderately high environmental stress at Kulai, compared to Padubidri.     

Studies on dissolution kinetics of dolime in electrothermal magnesium slag

The electrothermal process of magnesium metal production is a promising route, where large sized internally heated reactor is used for magnesium production resulting in less energy and labour intensive and high space-time yield process. However, the dissolution behavior of dolime in the electrothermal slag has been found critical for the process optimization. In this paper, the dissolution kinetics of the dolime in the slag was discussed. Quaternary slag (CaO-Al₂O₃-SiO₂-MgO) was prepared having basicity CaO/SiO₂ ≥ 1.8 and Al₂O₃/SiO₂ ≥ 0.26 for dolime dissolution studies by static hot dip method. Prior to the experiments, FactSage calculations were carried out varying temperatures and slag compositions. In the kinetic studies, dolime particles 10–15 mm size was added in slag melted at 1450, 1500 and 1550°C and samples were taken at various time intervals. The chemical analysis of slag sample was carried out to investigate the dissolution kinetics to establish the rate expression. The activation energy for the process was calculated for different models used in study and was found to be in the range of 130–270 kJ/mol. SEM analysis was done for surface analysis of reacted particles. This study would be helpful in optimizing the dolime charging rate during pilot scale trials for electrothermal magnesium production at CSIR-NML, Jamshedpur.