Synthesis, Densification, and Phase Evolution Studies of Al2O3–Al2TiO5–TiO2 Nanocomposites and Measurement of Their Electrical Properties

Alumina–aluminum titanate–titania (Al₂O₃–Al₂TiO₅–TiO₂) nanocomposites were synthesized using alkoxide precursor solutions. Thermal analysis provided information on phase evolution from the as-synthesized gel with an increase in temperature. Calcination at 700°C led to the formation of an Al₂O₃–TiO₂ nanocomposite, while at a higher temperature (1300°C) an Al₂O₃–Al₂TiO₅–TiO₂ nanocomposite was formed. The nanocomposites were uniaxially compacted and sintered in a pressureless environment in air to study the densification behavior, grain growth, and phase evolution. The effects of nanosize particles on the crystal structure and densification of the nanocomposite have been discussed. The sintered nanocomposite structures were also characterized for dielectric properties.     

Effect of graphene concentration on performance of MEH:PPV/graphene nanocomposite based devices

Herein, we explore the effect of graphene concentration on performance of poly [2-methoxy-5-2-ethylhexoxy-p-phenylene vinylene] (MEH:PPV)/graphene nanocomposite based devices. The surface morphology of the nanocomposites analyzed through emission scanning electron microscopy suggest that increase in graphene concentration results in the formation of aggregation. Optical and structural properties of the nanocomposites examined through UV–Vis absorption and Raman spectra revealed that the addition of graphene has no affect on the conjugation length and structure of the MEH:PPV. The electrical characteristics of devices have been investigated by I–V measurement under dark and illumination at room temperature. The devices show increase in the current value and reduction on turn-on voltage with increase in the graphene concentration up to 5 wt%. However, increase in graphene concentration above 5 wt% leads to the performance degradation of the devices. Moreover, charge transport mechanisms of the devices have been explained through Ohmic behavior at lower voltages and trap charge limited conduction at higher voltages.     

<Emphasis Type="Italic">k–µ</Emphasis> fading channels: a finite state Markov modelling approach

Finite state Markov channel (FSMC) is the automatic choice for accurate modelling of slow fading channels with memory. FSMC model for a k–µ fading channel is investigated in this paper. Small-scale variations of the fading signal under Line-Of-Sight conditions are represented by k–µ fading distributions. Here, FSMC is constructed by partitioning the fading amplitude into several regions. Each region corresponds to a particular state in the Markov model. The transition among these channel states characterizes the physical fading process. Performance measures such as steady-state probability, state-transition probability, level crossing rate and state-time duration corresponding to the k–µ fading channel are derived, plotted and analysed. Finally, numerical results prove that FSMC modelling provides an effective way to reflect the nature of the k–µ fading channel.     

Analysis of full reference quality metrics for image transmission over a MIMO OWC channel under varying turbulent conditions

The integrated OWC-PON architecture has a potential to overcome the limitations of existent RF technology and eliminate the last mile bottleneck in geographically constrained access networks thus providing real sense broadband from core to user. However, phenomenon such as atmospheric turbulence causes performance degradation in such systems. In the dissemination of multimedia services, the performance is the ultimate quality as perceived by end user's visual senses. To ascertain this quality in quantitative terms, full reference quality metrics are employed for communication purposes. This paper deals with classification, evaluation and analysis of various image quality assessment metrics for image transmission over OWC channel under varying turbulent conditions. The performance enhancement in terms of these metrics is investigated by deploying MIMO diversity reception. Moreover, a prediction model for SSIM is developed and compared for both SISO and MIMO links. The results show an improvement in IQA metrics with diversity reception. SSIM can be predicted in terms of log of refractive index structure parameter by a fourth order polynomial model for both SISO and MIMO receptions under all regimes of turbulence. The goodness of the fit statistics is presented along with the models to provide for their accuracy and reliability.     

Touchy feely vectors: A compensatory design approach to support model-based reasoning in developing country classrooms

Educational technology designs in developing countries mostly focus on making knowledge resources widely available, through MOOCs, repositories and computer-based tutoring. The use of digital media for cognitive augmentation, particularly interactive designs that help learners understand modelling topics in STEM, is underexplored. We report a 3-year design study examining this potential in the Indian context, testing two iterations of an interactive system, Touchy-Feely Vectors (TFV). The design supports learning vectors, a modelling topic pre-university students struggle with. Virtual lesson-plans were co-designed with teachers to augment — but not replace — their existing practices, and to address classroom and resource constraints. Pre-post testing of TFV-1 (a computer-based prototype) showed that it helped students develop a more integrated vector concept, and improved their reasoning. Field-implementation of TFV-2 (a textbook-linked touch-screen based design) in 6-classrooms (3-Control, N=135; 3-Experimental, N=131) showed that it fostered cognitive engagement in average-students and geometry-algebra integration (model-based reasoning) in good-students. These results, along with a requirements analysis based on textbooks, indicate that the interaction possibilities supported by different representational media critically shape student reasoning. The study also illustrates a systematic approach to design and test digital media systems that support cognitive augmentation in developing countries.     

浅层排水系统降雨过程氮磷垂直迁移数值仿真

浅层排水系统是一种快速排出农田积水的有效设施,但其同时也改变了水分及面源污染物如氮磷在农田系统迁移的速度和途径.为了对浅层排水农田系统中的氮磷垂直迁移过程有全面了解,利用有限元分析技术对已监测的浅层排水系统单元土壤柱进行数值仿真.结果表明,在5 h 4 mm/h降雨结束后,降雨量没有达到使地表到排水管道之间土壤层完全饱和,从而使随之溶解的氮磷污染物不足以渗透到排水管,导致没有氮磷的流失.降雨时间延长至10 h后,降雨量使土壤层达到饱和,从而使溶解的污染物产生流失,其中硝酸盐的流失量明显大于磷酸盐,硝酸盐流失量为9~10 mg/L,磷酸盐流失量为0.05~0.1 mg/L.在24 h降雨事件后,排水管中硝酸盐质量分数达最大值.在降雨时间不断增加的过程中,硝酸盐流失呈指数增长,而磷酸盐只是线性增长,形成该现象的原因与污染物的本身性质有关.     

Structural and Mechanical Analysis of APCVD Deposited Diamond-Like Carbon Thin Films

Silicon - In this study, diamond-like Carbon (DLC) thin film coatings are deposited by atmospheric pressure chemical vapour deposition (APCVD) process by using C2H2 and H2 as precursor gases on...     

Production of thermostable alkaline lipase on vegetable oils from a thermophilic Bacillus sp. DH4, characterization and its potential applications as detergent additive

BACKGROUND: The alkaline lipase production on vegetable oils as sole carbon source, its characterization and effect of different commercial detergents and surfactants on enzymatic activity from thermophilic Bacillus sp. DH4 was investigated. RESULTS: The organism grew on mannose, but the amount of lipase secreted was significantly less than on vegetable oils. This study identified a simple substrate for lipase production and established the utility of groundnut oil for increasing the lipase yield. The enzyme was compatible with various ionic and non‐ionic surfactants as well as commercial detergents. Lipase activity was strongly inhibited by sodium dodecyl sulfate (SDS), but not by Triton X‐100 or Triton X‐114. The best assay conditions observed for this lipase was found to be pH 9.0 and 50 °C. The enzyme was stable at alkaline pH and considerable activity was observed at pH 10 and it retained 93% of the residual activity at 60 °C. The lipase showed a novel property of marked activation at alkaline pH. Wash performance analysis of commercial detergent for removal of fatty stains improved upon addition of lipase. CONCLUSION: The production on cheap vegetable oils, novel properties and resistance towards various surfactants and tolerance to commercial detergents make this lipase a potential additive for detergent formulations. Significance and impact of the study: Bacillus sp. produces alkaline and thermostable lipase on cheap vegetable oils and its compatibility can find use in the detergent industry. Copyright © 2008 Society of Chemical Industry     

Antimalarial drug artesunate aff ords protection against carrageenan induced acute infl ammation in rat

Artesunate, an antimalarial drug, has been shown to inhibit the release of inflammatory mediators in various disease conditions. The present study was carried out to evaluate the anti-edematogenic effect of artesunate in the rat paw edema model. Inflammation was induced in the hind paw of rat by sub-plantar injection of 0.1 mL of 0.5% carrageenan and the paw volume was measured up to a fixed mark just before the injection and then after 3 h. The difference in two volumes gave a measure of edema formation. At 3h the level of TNF-α, PGE2 and myeloperoxidase were estimated in the inflamed paw tissue. Treatment of rats with single dose of artesunate at 50 and 150 mg/kg produced a dose-dependent inhibition in paw inflammation where a significant reduction in edema volume and mediator release was observed. Our study shows that by inhibiting the release of inflammatory mediators artesunate affords protection against acute inflammation induced in the rat paw and suggests that it has a potential to be used in the treatment of inflammatory disease conditions.