Numerical Analysis of Thermal Stress for a Stack of Planar Solid Oxide Fuel Cells

In this work, a 3D multi-physics coupled model was developed to analyze the temperature and thermal stress distribution in a planar solid oxide fuel cell (SOFC) stack, and then the effects of different flow channels (co-flow, counter-flow and cross-flow) and electrolyte thickness were investigated. The simulation results indicate that the generated power is higher while the thermal stress is lower in the co-flow mode than those in the cross-flow mode. In the cross-flow mode, a gas inlet and outlet arrangement is proposed to increase current density by about 10%. The generated power of the stack increases with a thin electrolyte layer, but the temperature and its gradient of the stack also increase with increase of heat generation. The thermal stress for two typical sealing materials is also studied. The predicted results can be used for design and optimization of the stack structure to achieve lower stress and longer life.

Mechanical Study of Some Polystyrene composites modified with adding inorganic fillers

Polystyrene-Zinc oxide microcomposites have been prepared for Mechanical study. The Zinc oxide micro particles were added to polystyrene by different concentrations that are (3, 5, and 7) by weight percent of the pure polymeric matrix. Solution casting method is used for preparing such composites. Different Mechanical properties of (PS-ZnO) microcomposites have been measured. Stress strain Curve is investigated for both pure Polystyrene and its composites with zinc oxide. The results showed that the Tensile Strength varies with the increase of ZnO in a specific way. Elongation at break of (PS-ZnO) micro composites increase with increase the content of (ZnO). An explanation of such behavior in tensile strength as well as Elongation at break has been discussed.

A study on in vitro antioxidant activity of aqueous seed extract of sesbania sesban (l) merr.

The present study was done to investigate the in vitro antioxidant activity of aqueous extract of Sesbania sesban seeds. The assays such as DPPH, Chelation, ferrous ion, ABTS, Superoxide radical, hydroxyl radical assay, FRAP assay and total antioxidant activity were done to assess the antioxidant potential of the seed extract. The extract was tested at a concentration range of 100 – 500 μg/ml for all the assays and the values were compared with a standard. The results obtained showed that the radical scavenging activity was in a dose dependent manner and found to increase with increase in concentration of the extract. The IC50 value was calculated for the assays and tabulated for inference. Different assays revealed different levels of radical scavenging potential of the extract and exhibited as a better antioxidant source for therapeutic applications.

Naturally Occurring Exudates Gums as Ecofriendly Inhibitors for Mild Steel Corrosion in Acidic Medium

The corrosion inhibition potentials of gum exudates from Daniella oliveri (DO) and Commiphora Africana (CA) for the corrosion of mild steel in H2 SO4 have been studied using weight loss and thermometric methods at 303 and 333K. Results show that the exudates gum actually reduced the rates of corrosion of mild steel. Increase in the concentrations of the exudate’s gums increased their percentage inhibition efficiencies. Corrosion rate was found to increase with increase in temperature in the presence and absence of the gum exudates, though the corrosion rate was slower in the presence of the exudates gums. Both DO and CA exudates gums were found to obey Temkin and Langmuir adsorption models at all concentrations and temperatures studied. Physical adsorption mechanism was proposed from the adsorption parameters. Kinetic and thermodynamic parameters revealed that the adsorption process is spontaneous, exothermic and no significant difference was found between the inhibition efficiencies of DO and CA.

Characterization of Eggshell: A Heterogeneous Catalyst in Transesterification of Sand Apple (Parinari polyandra) Seed Oil

The objective of this study was to characterize a low cost heterogeneous catalyst from the transesterification of sand apple (Parinari polyandra B.) biodiesel. Sand apple fruits were processed and oil was extracted using solvent extraction method. Raw eggshells were calcined at 800°C for 120 min in the muffle furnace. Surface properties of the raw and calcined eggshell were characterized using Fourier Transformed Infrared Radiation (FTIR) and X-Ray Fluorescence (XRF). Transesterification of the Sand Apple Oil (SASO) with ethanol in the presence of the calcined catalyst to produce ethyl ester and glycerol were optimized using Central Composite Design at different temperatures and time. Reactants for the transesterification process were the raw SASO and anhydrous ethanol. The study shows that raw eggshell was more stable with hydrogen bond form at 2,724 cm-1an while oil yield of 53.13 % was obtained from sand apple kernels. Ethyl ester yield of 90% was obtained from SASO. The results of transesterification shows the maximum biodiesel yield of 90% was obtained at reaction temperature of 65°C and time of 120 min, while the minimum yield of 70% was obtained at temperature of 55°C and time of 60 min; indicating that biodiesel increase with increase in time. Similarly, yield of ethyl ester of SASO also increased when the reaction temperature increased. The percentages of biodiesel yield obtained from SASO transesterification in this study showed that sand apple is promising oil for biodiesel production as compared with other vegetable oil crop obtained in previous studies

The Alkaline solvolysis of allyl bromide in alcohol-water solvents

<p>The rate of the alkaline solvolysis of allyl bromide has been measured in various ethanol-water and methanol-water mixtures. This has been found to increase with increase in solvent polarity. An attempt was made to explain this behaviour in terms of partial ionisation of the substrate. It has been suggested that in nucleophilic substitution the individual specific rate constants for attack by alkoxide or hydroxide ions are a better indication of solvent effects than the apparent overall rate constant.</p>

The Alkaline solvolysis of allyl bromide in alcohol-water solvents

<p>The rate of the alkaline solvolysis of allyl bromide has been measured in various ethanol-water and methanol-water mixtures. This has been found to increase with increase in solvent polarity. An attempt was made to explain this behaviour in terms of partial ionisation of the substrate. It has been suggested that in nucleophilic substitution the individual specific rate constants for attack by alkoxide or hydroxide ions are a better indication of solvent effects than the apparent overall rate constant.</p>

Investigation of the mathematical model of the knife of geokhod executive body interaction with the bottomhole rock

The article presents the relevance of the research. The features of the work of the executive body of geokhod are given. A previously developed mathematical model for determining the power and energy parameters of the interaction of the knife executive body of the geokhod with the face rock is presented. On the basis of the model, a study was carried out of the influence of the pitch of the external mover on the power and energy parameters of the interaction of the knife executive body of the geokhod with the bottomhole rock. As a result of the study, it was found that the power parameters increase with increase in the step of the external mover, and the energy parameters decrease.

Density and Viscosity of LiCl, LiBr, LiI and Kcl in Aqueous Methanol at 313.15K

The densities and viscosities of electrolytes are essential to understand many physicochemical processes that are taking place in the solution. In the present research, the densities and viscosities of lithium halides, LiX (X = Cl, Br, I ) and KCl in (0, 20, 40, 50, 60, 80 and 100) mass % of methanol + water at 313.15K were calculated employing experimental densities (ρ), the apparent molar volumes( ϕv) and limiting apparent molar volumes (0v) of the electrolytes. The (0v) of electrolyte offer insights into solute-solution interactions. In terms of the Jones-Dole equation for strong electrolyte solution, the experimental data of viscosity were explored. Viscosity coefficients A and B have been interpreted and discussed. The B-coefficient values in these systems increase with increase of methanol in the solvents mixtures. This implied that when the dielectric constant of the solvent decreases, so do the solvent-solvent interactions in these systems.

Intraoperative surgical difficulties encountered during repeat caesarean section in a tertiary care centre in Northeast India

Background: Caesarean section is the commonest obstetric operative procedure worldwide. The potential perioperative problems in repeat caesarean section include adhesions, increased blood loss, prolonged operative time, injuries to adjacent structures, hysterectomy etc. These increase with increase in caesarean section number.Methods: Hospital based observational study, conducted at Dept. of Obstetrics and Gynaecology, Assam Medical College, from July 2019 to June 2020 with the aim to study intraoperative difficulties encountered during repeat caesarean section. Cases were grouped into two main groups based on number of prior caesarean sections. A detailed history, clinical and intraoperative findings of all pregnant women undergoing repeat caesarean section were noted. Results were tabulated and analysed.Results: Out of 400 women with prior caesarean section who underwent repeat caesarean. 321 had 1 prior caesarean and rest had 2. Among the cases cephalopelvic disproportion was the commonest (43.25%) indication and obstructed labour was the least common (0.25%). Common complications were adhesions (38.25%), thinned lower uterine segment (27%), advance bladder (19.50%), uterine dehiscence (14.75%), excess blood loss (12.75%), extension of uterine incision (8.25%), uterine rupture (1%), placenta accrete (0.75%), and bladder injury (0.5%). Intraoperative complications like adhesions, uterine dehiscence, delivery and operating time were significantly higher in women with 2 prior caesarean section compared to 1 prior caesarean section (p<0.001).Conclusions: Women with caesarean scar are at high risk in subsequent pregnancies particularly in a country like India where antenatal care is often neglected. Best technique to reduce multiple potential complications of repeat caesarean section is to reduce the rates of primary and repeat caesarean sections whenever possible.