Numerical analysis of defect formation during fabrication of high temperature polymer electrolyte membrane solutions

Previous studies have shown that defects like pin‐holes and air entrainment are common during polymer electrolyte membrane (PEM) manufacturing. For mass production of defect‐free membranes, an optimized manufacturing process is required. The objective of this work is to understand the nature of defect generation during the manufacturing process of high‐temperature PEM membranes and the factors influencing them. An extrusion process is simulated using a multiphase, laminar model using computational fluid dynamics (CFD) techniques. The effects of processing conditions on quality of the cast and pressure drop are analyzed. The results showed that for a constant inlet to substrate velocity ratio, both the substrate velocity and temperature will have an insignificant effect on the entrained air height. However, their effect on pressure drop is found to be substantial. Further, it is shown that the inlet velocity and slot gap width have significant effect on the entrained air height and pressure drop. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers.     

Synthesis and structure of undoped and indium-doped thermoelectric lead telluride nanoparticles

Undoped and indium (In)-doped lead telluride (PbTe) nanostructures were synthesized via solvothermal/hydrothermal route. The crystalline structure of the as-prepared undoped and In-doped PbTe samples was examined by X-ray diffraction (XRD) which indicated the formation of face-centered single-phase cubic crystal. A first principle calculation on indium doping shows that the indium atoms are more likely to replace lead (Pb) rather than to take the interstitial sites. Laser-induced breakdown spectroscopy (LIBS) analysis confirms that indium is incorporated into the PbTe matrix of the indium-doped PbTe samples. The effects of surfactant and synthesis temperature on the structure and morphology of the undoped PbTe were also investigated; it was found that PbTe nanostructures synthesized with the addition of surfactants exhibited uniform shapes and their size increased with the synthesis temperature.     

Performance Analysis of all Optical 4*2 and 8*3 Encoder Using Two Dimensional Photonic Crystals Waveguides

Silicon - In this paper, Two Dimensional Photonic Crystal (2DPC) based 4*2 and 8*3 encoders are devised using Y shaped waveguides. The proposed encoder operates at 1550 nm. In this...     

Red lesion in fundus image with hexagonal pattern feature and two-level segmentation

Multimedia Tools and Applications - Red lesion identification at its early stage is very essential for the treatment of diabetic retinopathy to prevent loss of vision. This work proposes a red...     

Phototherapeutic keratectomy versus alcohol epitheliectomy with mechanical debridement for superficial variant of granular dystrophy: A paired eye comparison

PurposeTo compare outcome of phototherapeutic keratectomy (PTK) and alcohol epitheliectomy with mechanical debridement for superficial variant of granular dystrophy.MethodCase report. A 7 year old girl with superficial variant of granular dystrophy with an visual acuity of 20/70 both eyes, underwent a simultaneous PTK in right eye (OD) and alcohol epitheliectomy with mechanical debridement in left eye (OS). Post operatively the visual acuity, refraction and corneal clarity were assessed.ResultsOn the first post-operative day uncorrected visual acuity was 20/50 in both eyes. At 2 weeks, vision improved to 20/40 with +2.50 ?2.00 × 180 in OD and +1.50 ?1.50 × 180 in OS. At 2 years, vision and refraction were 20/25 with +2.50 ?2.00 × 180 in OD and 20/25 with +1.25 ?1.50 × 170 OS respectively. There was early recurrence of the granular dystrophy.ConclusionThe visual outcomes of both PTK and alcohol epitheliectomy are similar for superficial variant of granular dystrophy. The hyperopic shift with PTK is a matter of concern. Alcohol epitheliectomy can be used in treatment of superficial corneal dystrophies where PTK is unavailable.     

Dynamics of nanotechnology patenting: An Indian scenario

Nanotechnology reflects the combination/interaction of knowledge which is interdisciplinary in nature. Exclusive monopoly over patents on nano-scale materials, devices and processes is a much sought after concept among technology based industries today. According to many scientists and theorists, this science can lead to solutions of some of the toughest problems faced by mankind and the list of patents on nano-scale materials, tools and processes is expanding at a phenomenal pace. Even India is among the top 20 nations in nanotechnology research as is evident by the number of patents filed each year. Trade regime of the world has brought into focus the ability to generate and secure IPR. The transformation has been rapid and in such a dynamic landscape it is vital to protect the intellectual property. With increasing private sector involvement in nanotechnology R&D, the need for a comprehensive framework for regulating nanotechnology IPRs will be pivotal to the commercial success of the technology. Hence, it becomes increasingly more and more important to learn the various issues in patenting of nanotechnology inventions and address these issues now so as to avoid any problems later. This paper discusses the various methodologies used in the developing countries and what can be done in India to protect the same keeping in mind the interests of various partners in the value chain of nanotech patent from lab to market.     

Main-chain sulphur containing water soluble poly(N-isopropylacrylamide-co-N,N′-dimethylacrylamide sulphide) copolymers via interfacial polycondensation

Here, we report the first synthesis of water soluble poly(N-isopropylacrylamide-co-N,N′-dimethylacrylamide sulfide) copolymers via conventional interfacial polycondensation method using phase transfer catalyst (PTC). The effect of various kinds of PTC having different aliphatic chain length and counter ion were employed to examine the kinetics of polysulfide polymer formation. The reactivity ratios, determined employing extended Kelene–Tüdös method using feed composition obtained from ¹H NMR analysis, suggest that N-isopropylacrylamide (NIPAM) is more reactive than N,N′-dimethylacrylamide (DMA) in both mono- and di-sulfide polymers. Thermal transition behavior investigated by differential scanning calorimetry (DSC) demonstrated that as the sulphur rank of the sulfide main chain linkages increased, the flexibility of the polymers increased reflected by lower glass transition temperature (T_g) values. The thermal degradation behavior and the major degradation products have been characterized by thermogravimetric analysis (TGA) and electron-impact mass spectroscopy (EI-MS), respectively. Both the studies reveal that the degradation takes place due to weak-link scission of the polymeric main chain. Solubility in water and in most of the common organic solvents even after the sulphur rank increased from 1 to 2 in the main chain, is expected to render potential applications in biological field as well as in industry for these interesting new class of polymers.     

Effect of titanium on the creep deformation behaviour of 14Cr-15Ni-Ti stainless steel

14Cr-15Ni-Ti modified stainless steel alloyed with additions of phosphorus and silicon is a potential candidate material for the future cores of Prototype Fast Breeder Reactor. In order to optimise the titanium content in this steel, creep tests have been conducted on the heats with different titanium contents of 0.18, 0.23, 0.25 and 0.36 wt.% at 973 K at various stress levels. The stress exponents indicated that the rate controlling deformation mechanism was dislocation creep. A peak in the variation of rupture life with titanium content was observed around 0.23 wt.% titanium and the peak was more pronounced at lower stresses. The variation in creep strength with titanium content was correlated with transmission electron microscopic investigations. The peak in creep strength exhibited by the material with 0.23 wt.% titanium is attributed to the higher volume fraction of fine secondary titanium carbide (TiC) precipitates.     

Treatment of wastewater from synthetic textile industry by electrocoagulation–electrooxidation

Treatment of wastewater from a textile industry that produces synthetic polyester cloths was studied employing electrochemical techniques. The sample was initially subjected to electrocoagulation to remove suspended solids. Mild steel and aluminum electrodes were tried as anodes; and aluminum was found to be effective for the removal of suspended solids. Using aluminum as anode, the chemical oxygen demand (COD) concentration of the effluent which was initially at the level of 1316 mg L⁻¹ could be reduced to 429 mg L⁻¹ by electrocoagulation. After electrocoagulation, the effluent was further subjected to electrooxidation using graphite and RuO₂/IrO₂/TaO₂ coated titanium as anodes. During the electrooxidation tests, both COD and chloride ion were simultaneously estimated; and the effect of Cl⁻ ion is discussed. The measurements have revealed the depletion of Cl⁻ ion concentration implying the generation of free chlorine during electrooxidation. The depletion of Cl⁻ ion concentration and the COD removal were observed to be comparatively high in the presence of graphite electrode. The effects of electrode materials and current density on COD removal are discussed. The instantaneous current efficiency (ICE), mass transfer coefficient and energy consumption were estimated.