Computational study on the influence of number of threads on the performance of single screw pump at high angular velocities

Fluid flow in a screw pump which rotates at very high angular velocity is numerically analyzed. In the present study, fluid flow in screw pumps under high Reynolds number, of the order of 10⁵, is considered. Screw pump has two major elements, a plain shroud which is a stationary element and a rotating hub with helical grooves contained within the shroud. In this paper, three variants of hubs with different number of thread starts numbering six, eight and twelve in combination with a plain shroud is studied. Each of the three possible combinations are analyzed on the basis of pressure rise developed, efficiency and shaft power. It was seen that pressure rise, efficiency and shaft power increases as the number of threads increases in the range of mass flow rates studied.     

Metrology and the linear canonical transform

It is shown experimentally that both surface tilt and in-plane translation motion can be independently estimated using the speckle photographic correlation technique by capturing consecutive images in two linear canonical transform domains (using two different quadratic phase systems). A geometric interpretation, based on use of the Wigner distribution function is presented to describe the method and a simple matrix approach, based on the ABCD matrix, is used to quantify it. It is shown that the sensitivity and dynamic range of measurement of both tilt and translation are both variable and depend on the parameters of the ABCD matrix.     

A tunable waveguide to cavity coupler for high power accelerator cavities

The end iris ridge waveguide couplers are used to couple power to accelerator cavities through a reduced size coupling port. However, higher electric and magnetic fields due to reduced size lead to strict requirements on dimensional tolerances during coupler fabrication process. It is shown by detailed parametric analysis that even small dimensional changes during manufacturing or operation can lead to undesired shift in design frequency and deterioration of return loss. Hence, transmitted power testing of two couplers connected back to back without an intermediate cavity cannot be carried out. Here, we propose cylindrical static tuners on impedance matching section to relax the dimensional tolerance requirements. It is also shown that an iris coupled coupler-cavity system is more tolerant towards coupler dimensional changes than a stand-alone coupler. However, same tuners can find use for tuning the coupling coefficient of coupler-cavity system. The proposed tuning scheme is expected to reduce the coupler manufacturing costs and provide an useful alternative for coupling coefficient tuning over iris machining.     

Preparation and Evaluation of Polyuretham Foam/Rubber Membrane-Based Samplers for use in Isocyanate Sampling

In order to collect isocyanate in both aerosol and vapor forms, we have developed a dual-membrane sampler which features a moist porous bed, backed up by an impermeable membrane. A polyester-polyurethane foam (PUF) was selected to function as the porous bed, and it was evaluated for its ability to resist solvent degradation and swelling while permitting rapid air penetration. Natural rubber (NR) and styrene-butadience rubber (SBR) membranes were prepared to serve as backup membranes. These were also evaluated for their solvent compatibility and air-penetration characteristics. A polyester-polyurethane foam backed up by a NR membrane prepared by an efficient vulcanization procedure was selected as the best combination for development of the isocyanate sampler. Recovery studies using the hexamethylene-based polyisocyanate, biuret, indicate better than 80% recovery of polyisocyanate after application to the PUF.     

A time of day analysis of crashes involving large trucks in urban areas

Previous studies have looked at different factors that contribute to large truck-involved crashes, however a detailed analysis considering the specific effects of time of day is lacking. Using the Crash Records Information System (CRIS) database in Texas, large truck-involved crashes occurring on urban freeways between 2006 and 2010 were separated into five time periods (i.e., early morning, morning, mid-day, afternoon and evening). A series of log likelihood ratio tests were conducted to validate that five separate random parameters logit models by time of day were warranted. The outcomes of each time of day model show major differences in both the combination of variables included in each model and the magnitude of impact of those variables. These differences show that the different time periods do in fact have different contributing factors to each injury severity further highlighting the importance of examining crashes based on time of day. Traffic flow, light conditions, surface conditions, time of year and percentage of trucks on the road were found as key differences between the time periods.     

Engineered polymer-based scaffold as an implantable therapeutic vaccine against melanoma

Although tumor-antigen-based therapeutic cancer vaccines are a potential cancer immunotherapy strategy, recent clinical trials show low efficacy for multiple reasons. One method that has been recently investigated to improve the efficacy of therapeutic cancer vaccines is the development of implantable vaccines for sustained delivery of antigens and CD8 T cell activation. Here, we optimized the composition for an implantable vaccine scaffold composed of alginate, polyvinyl alcohol, and poly(methyl vinyl ether- alt-maleic anhydride) loaded with tumor antigens. Considering the adjuvant property of aluminum compounds, aluminum ion was used to crosslink alginate in the scaffold. The scaffold showed an effective antigen incorporation efficiency of 90.34 ± 0.55% using ovalbumin as the model antigen and 89.67 ± 2.8% using B16-F10 cell lysate. SEM analysis of the scaffold showed pore size ranging from 5 to 10 μm. Cell viability analysis using mouse RAW 264.7 macrophages proved the cytocompatibility of the scaffold. In vitro antigen release studies using ovalbumin showed 8.42% release for a period of 14 days. In vivo antitumor analysis carried out in subcutaneous mouse B16-F10 melanoma model demonstrated that the scaffold vaccine reduced the rate of tumor growth and improved survival in tested animals. The median survival time increased from 29 days in untreated animals to 58 days in scaffold vaccine-implanted animals.     

Antidiabetic effect of Ficus racemosa Linn. stem bark in high-fat diet and low-dose streptozotocin-induced type 2 diabetic rats: A mechanistic study

The present study was designed to investigate the effects of the ethanol extract of Ficus racemosa (FRE) on biochemical parameters in type 2-like diabetes, induced by a combination of standardised high-fat diet and low-dose streptozotocin (25 mg kg⁻¹, i.p.) in rats. To elucidate the mode of action of FRE, its effects on a battery of targets involved in glucose homeostasis was evaluated. FRE (200 and 400 mg kg⁻¹, p.o.), in a dose-dependent manner, altered the biochemical parameters and significantly improved glucose tolerance and HDL-c levels. In different bioassays, FRE showed inhibition of PTP-1B (IC₅₀ 12.1 μg/mL) and DPP-IV (42.5%). FRE exhibited 82.6% binding to PPAR-γ. Furthermore FRE exhibited stimulation of glucose uptake by skeletal muscles (hemi-diaphragm). Bergenin was quantified in bioactive-FRE by high-performance liquid chromatography (0.15% w/w). This is the first report demonstrating the effectiveness of F. racemosa stem bark in type 2 diabetes and targets involved in it.     

Synthesis of polytitanates by carbonate-gel precipitation route

Polytitanates in the TiO₂-rich side of the phase diagram of BaO-TiO₂ system play a major role as microwave dielectric ceramics. The present study aims at synthesis of polytitanates through carbonate-gel route and to re-look at the formation mechanism of Ba₂Ti₉O₂₀ (2:9). Apart from 2:9, closely related materials such as BaTi₄O₉ (1:4), BaTi₅O₁₁ (1:5), Ba₄Ti₁₃O₃₀ (4:13) and Ba₆Ti₁₇O₄₀ (6:17) were also synthesized. Besides 2:9, phases that are richer in TiO₂ as well as those richer in barium form as single-phase. These results point to the fact that nucleation and surface energy are the critical factor for the formation of 2:9 materials as single-phase ceramic, rather than diffusion.     

Sensorless variable-speed controller for existing fixed-speed wind power generator with unity-power-factor operation

A variable-speed controller, for an existing 225 kW fixed-speed wind power generator, is presented in this paper. A sensorless direct torque control algorithm-based controller is proposed for the squirrel-cage induction generator. Generator torque reference is derived based on sensorless maximum power tracking mode algorithm, up to the base speed of the generator. A three-phase front-end converter is used here to deliver the generated power to the grid with unity-power-factor operation at all wind speeds. This algorithm is based on direct active and reactive power control. The experimental waveforms from the actual installation site are presented in this paper with a comparison of the existing fixed-speed system. An interpretation of the results is also presented here.     

Comparison of Liquid and Gas-Phase Photooxidation of MTBE: Synthetic and Field Samples

The feasibility of photooxidation treatment of methyl tert-butyl ether (MTBE) in water was investigated using two systems: (1) a slurry falling film photoreactor and (2) an integrated air stripping with gas phase photooxidation system. Methyl tert-butyl ether-contaminated synthetic water and field samples from contaminated sites were used for these studies. Using a TiO2 slurry (0.1 g/L; Degussa P25) flowing down at a rate of up to 0.26 L/min over the inner surface of a glass tube surrounding a 1-kW medium pressure mercury lamp, more than 99% of MTBE in the synthetic samples, initially at 1 mg/L, was degraded within 90 min. The major degradation products from MTBE were tert-butyl alcohol, tert-butyl formate, and small amounts of acetone. However, the degradation of MTBE and its byproducts in contaminated groundwater samples was hindered significantly by dissolved metals such as Fe2+, chloride ions, and aromatic organic species. Integrating air stripping with gas-phase photocatalysis is an an effective alternative that would not be affected by the water chemistry. The reaction rates for MTBE degradation in the gas phase are orders of magnitude faster than in aqueous solution.