COMPARISON AND CROSS-VALIDATION OF OPTICAL TECHNIQUES IN DIFFERENT SWIRL SPRAY REGIMES

This paper deals with an experimental study of pressure-swirl hydraulic injector nozzles using non-intrusive optical techniques. Experiments were conducted to study atomization characteristics using two nozzles with different orifice diameters, 0.3 mm and 0.5 mm, and injection pressures, 0.3-3.5 Mpa, which correspond to Reynolds number (Re-p) = 7,000-45,000, depending on nozzle utilized. Three laser diagnostic techniques were utilized: Shadowgraph, PIV (Particle Image Velocimetry), and PDPA (Phase Doppler Particle Anemometry). Measurements made in the spray in both axial and radial directions indicate that velocity, average droplet diameter profiles, and spray dynamics are highly dependent on the nozzle characteristics and injection pressure. Limitations of these techniques in the different flow regimes, related to the primary and secondary breakups as well as coalescence, are provided. Results indicate that all three techniques provide similar results throughout the different regimes. Shadowgraph and PDPA were possible in the secondary atomization and coalescence regimes while PIV measurements could be made only at the end of secondary atomization and coalescence.

Forming limit investigation of friction stir welded sheets: influence of shoulder diameter and plunge depth

The main aim of the present work is to analyze the influence of shoulder diameter and plunge depth on the formability of friction stir welded sheets. The base material used for welding and forming was AA6061-T6. Formability evaluation was performed through limiting dome height tests. The forming limit curve, FLC (only in the stretching region), thickness distribution, and strain hardening exponent of the weld region were monitored during formability studies. It is found from the work that the forming limit of friction stir welded sheets is better than unwelded sheets. In general, with an increase in shoulder diameter and plunge depth, the forming limit is found to improve considerably. With a decrease in thickness gradient severity and an increase in strain hardening exponent (n) of the weld region, the forming limit is found to increase. The increase in n value of the weld region is believed to occur because of the reduction in dislocation density. The maximum thickness difference is higher in the retreating side, rather than in the advancing side, of the weld. This is due to the differential straining and hardness levels attained by both sides during friction stir welding.

Growth of AgInS2 thin films by ultrasonic spray pyrolysis technique

Silver Indium Di-sulfide (AgInS2) thin films are deposited using ultrasonic spray pyrolysis technique and the effect of substrate temperature (T-s) on film growth is studied by varying the temperature from 250 to 400 degrees C. From the structural analysis, orthorhombic AgInS2 phase is identified with preferential orientation along (002) plane. Further analysis with Raman revealed the coexistence of Cu-Au ordered and chalcopyrite structures in the films. Stoichiometric films are obtained at T-s of 300 degrees C. Above 300 degrees C, the film conductivity changed from p to n-type and the grain size decreased. The band gap of AgInS2 films varied from 1.55 to 1.89 eV and absorption coefficient is found to be >10(4) cm(-1). The films have sheet resistance in the range of 0.05 to 1300 Omega/square Both p and n type films are prepared through this technique without any external doping. (C) 2013 Elsevier B.V. All rights reserved.

Lysis dynamics and membrane oligomerization pathways for Cytolysin A (ClyA) pore-forming toxin

Pore-forming toxins are known for their ability to efficiently form transmembrane pores which eventually leads to cell lysis. The dynamics of lysis and underlying self-assembly or oligomerization pathways leading to pore formation are incompletely understood. In this manuscript the pore-forming kinetics and lysis dynamics of Cytolysin-A (ClyA) toxins on red blood cells (RBCs) are quantified and compared with experimental lysis data. Lysis experiments are carried out on a fixed mass of RBCs, under isotonic conditions in phosphate-buffered saline, for different initial toxin concentrations ranging from 2.94-14.7 nM. Kinetic models which account for monomer binding, conformation and oligomerization to form the dodecameric ClyA pore complex are developed and lysis is assumed to occur when the number of pores per RBC (n(p)) exceeds a critical number, n(pc). By analysing the model in a sublytic regime (n(p) < n(pc)) the number of pores per RBC to initiate lysis is found to lie between 392 and 768 for the sequential oligomerization mechanism and between 5300 and 6300 for the non-sequential mechanism. Rupture rates which are first order in the number of RBCs are seen to provide the best agreement with the lysis experiments. The time constants for pore formation are estimated to lie between 1 and 20 s and monomer conformation time scales were found to be 2-4 times greater than the oligomerization times. Cell rupture takes places in 100s of seconds, and occurs predominantly with a steady number of pores ranging from 515 to 11 000 on the RBC surface for the sequential mechanism. Both the sequential irreversible and non-sequential kinetics provide similar predictions of the hemoglobin release dynamics, however the hemoglobin released as a function of the toxin concentration was accurately captured only with the sequential model. Each mechanism develops a distinct distribution of mers on the surface, providing a unique experimentally observable fingerprint to identify the underlying oligomerization pathways. Our study offers a method to quantify the extent and dynamics of lysis which is an important aspect of developing novel drug and gene delivery strategies based on pore-forming toxins.

Optical, Electrochemical, and Structural Properties of Spray Coated Dihexyl Substituted Poly (3,4 propylene dioxythiophene) Film for Optoelectronics Devices

The dihexyl substituted poly (3,4-propylenedioxythiophene) (PProDOT-Hx(2)) thin films uniformly deposited by cost effective spray coating technique on transparent conducting oxide coated substrates. The electro-optical properties of PProDOT-Hx(2) films were studied by UV-Vis spectroscopy that shows the color contrast about 45% with coloration efficiency of approximate to 185cm(2)/C. The electrochemical properties of PProDOT-Hx(2) films were studied by cyclic voltammetry and AC impedance techniques. The cyclic voltammogram shows that redox reaction of films are diffusion controlled and ions transportation will be faster on the polymer film at higher scan rate. Impedance spectra indicate that polymer films are showing interface charge transfer process as well as capacitive behavior between the electrode and electrolyte. The XRD of the PProDOT-Hx(2) thin films revealed that the films are in amorphous nature, which accelerates the transportation of ions during redox process.

Experimental investigation of forming limit, void coalescence and crystallographic textures of aluminum alloy 8011 sheet annealed at various temperatures

In this work, a combined forming and fracture limit diagram, fractured void coalescence and texture analysis have been experimentally evaluated for the commercially available aluminum alloy Al 8011 sheet annealed at different temperatures viz. 200 degrees C, 250 degrees C, 300 degrees C and 350 degrees C. The sheets were examined at different annealing temperatures on microstructure, tensile properties, formability and void coalescence. The fractured surfaces of the formed samples were examined using scanning electron microscope (SEM) and these images were correlated with fracture behavior and formability of sheet metals. Formability of Al 8011 was studied and examined at various annealing temperatures using their bulk X-ray crystallographic textures and ODF plots. Forming limit diagrams, void coalescence parameters and crystallographic textures were correlated with normal anisotropy of the sheet metals annealed at different temperatures. (C) 2013 Politechnika Wroclawska. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Growing Length Scales and Their Relation to Timescales in Glass-Forming Liquids

The question of whether the dramatic slowing down of the dynamics of glass-forming liquids near the structural glass transition is caused by the growth of one or more correlation lengths has received much attention in recent years. Several proposals have been made for both static and dynamic length scales that may be responsible for the growth of timescales as the glass transition is approached. These proposals are critically examined with emphasis on the dynamic length scale associated with spatial heterogeneity of local dynamics and the static point-to-set or mosaic length scale of the random first order transition theory of equilibrium glass transition. Available results for these length scales, obtained mostly from simulations, are summarized, and the relation of the growth of timescales near the glass transition with the growth of these length scales is examined. Some of the outstanding questions about length scales in glass-forming liquids are discussed, and studies in which these questions may be addressed are suggested.

Impact of spray flux density and vacuum annealing on the transparent conducting properties of doubly doped (Sn plus F) zinc oxide films deposited using a simplified spray technique

In this investigation transparent conducting properties of as-deposited and annealed ZnO:Sn:F films deposited using different spray flux density by changing the solvent volume (10 mL, 20 mL ... 50 mL) of the starting solutions have been studied and reported. The structural analyses of the films indicate that all the films have hexagonal wurtzite structure of ZnO with preferential orientation along (002) plane irrespective of the solvent volume and annealing treatment whereas, the overall crystalline quality of the films is found to be enhanced with the increase in solvent volume as well as with annealing. This observed enhancement is strongly supported by the optical and surface morphological results. From the measurements of electrical parameters, it is seen that, the annealed films exhibit better electrical properties compared to the as-deposited ones. Annealing has caused agglomeration of grains as confirmed by the surface morphological studies. Also, the annealing process has led to an improvement in the optical transparency as well as band gap. It is found from the analyses of the characteristics of the as- deposited and annealed films that the annealed film deposited from starting solution having solvent volume of 50 mL is optimal in all respects, as it possesses all the desirable characteristics including the quality factor (1.60 x 10(-4) (Omega/sq.)(-1)). (C) 2014 Elsevier Ltd. All rights reserved.

Breakup processes of pressure swirl spray in gaseous cross-flow

Injection of liquid fuel in cross flowing air has been a strategy for future aircraft engines in order to control the emissions. In this context, breakup of a pressure swirl spray in gaseous cross-flow is investigated experimentally. The atomizer discharges a conical swirling sheet of liquid that interacts with cross-flowing air. This complex interaction and the resulting spray structures at various flow conditions are studied through flow visualization using still as well as high speed photography. Experiments are performed over a wide range of aerodynamic Weber number (2-300) and liquid-to-air momentum flux ratio (5-150). Various breakup regimes exhibiting different breakup processes are mapped on a parameter space based on flow conditions. This map shows significant variations from breakup regime map for a plain liquid jet in cross-flow. It is observed that the breakup of leeward side of the sheet is dominated by bag breakup and the windward side of the sheet undergoes breakup through surface waves. Similarities and differences between bag breakup present in plain liquid jet in cross-flow and swirl spray in cross-flow are explained. Multimodal drop size distribution from bag breakup, frequency of bag breakup, wavelength of surface waves and trajectory of spray in cross-flow are measured by analyzing the spray images and parametric study of their variations is also presented. (C) 2014 Elsevier Ltd. All rights reserved.

Tin-Incorporation Induced Changes in the Microstructural, Optical, and Electrical Behavior of Tungsten Oxide Nanocrystalline Thin Films Grown Via Spray Pyrolysis

Undoped and Sn-doped WO3 thin films were grown on cleaned glass substrates by chemical spray pyrolysis, using ammonium tungstate (NH4)(2)WO4 as the host precursor and tin chloride (SnCl4 center dot 5H(2)O) as the source of dopant. The XRD spectra confirm the monoclinic structure with a sharp narrow peak along (200) direction along with other peaks of low relative intensities for all the samples. On Sn doping, the films exhibit reduced crystallinity relative to the undoped film. The standard deviation for relative peak intensity with dopant concentration shows enhancement in heterogeneous nucleation growth. As evident from SEM images, on Sn doping, appearance of island-like structure (i.e., cluster of primary crystallites at few places) takes place. The transmittance has been found to decrease in all the Sn-doped films. The optical band gap has been calculated for both direct and indirect transitions. On Sn doping, the direct band gap shows a red shift and becomes 2.89 eV at 2 at.% doping. Two distinct peaks, one blue emission at 408 nm and other green emission at 533 nm, have been found in the PL spectra. Electrical conductivity has been found to increase with Sn doping.

Fragility correlates thermodynamic and kinetic properties of glass forming liquids

In our earlier communication we proposed a simple fragility determining function, (NBO]/(VmTg)-T-3), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, Delta C-p/C-p(1), introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both Delta C-p and Delta T and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters Delta C-p, C-p(1), T-g and T-m. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam-Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the Delta C-p versus In(T-r) curves and hence the configurational entropy. (C) 2014 Elsevier Ltd. All rights reserved.

Fragility correlates thermodynamic and kinetic properties of glass forming liquids

In our earlier communication we proposed a simple fragility determining function, (NBO]/(VmTg)-T-3), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, Delta C-p/C-p(1), introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both Delta C-p and Delta T and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters Delta C-p, C-p(1), T-g and T-m. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam-Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the Delta C-p versus In(T-r) curves and hence the configurational entropy. (C) 2014 Elsevier Ltd. All rights reserved.