Recovery of Acrylic Acid Using Calcium Peroxide Nanoparticles: Thermodynamics and Continuous Column Study

The thermodynamic parameters (DGº, DHº, and DSº) for adsorption of acrylic acid on CaO2 nanoparticle were estimated in the temperature range of 300.15 – 313.15 K, which helps to evaluate the feasibility of adsorption process, nature of adsorption process, and affinity of adsorbent toward solute molecule. A dynamic adsorption study in a fixed-bed column was performed using CaO2 nanoparticle for the recovery of acrylic acid from aqueous stream. The breakthrough curves of adsorption system were obtained for different process variables, such as initial acrylic acid concentration (2882–7206 mg L–1), flow rate (5–9 mL min–1), and bed height (10–20 cm). The bed-depth service time model, Thomas model, Yoon-Nelson model, and deactivation kinetic model were applied to the experimental data to predict the column performance. The data were in good agreement with the deactivation kinetic model. The presented results may be useful for the design of adsorption system using nanoparticles, which can be further extended to other systems. This work is licensed under a Creative Commons Attribution 4.0 International License

Recovery of Acrylic Acid Using Calcium Peroxide Nanoparticles: Synthesis, Characterisation, Batch Study, Equilibrium, and Kinetics

Recovery of acrylic acid from aqueous solution using low-cost CaO2 nanoparticles was investigated. CaO2 nanoparticles were synthesized by co-precipitation technique and characterised using XRD and FTIR. A mechanism was proposed for adsorption of acrylic acid onto CaO2 nanoparticles based on FTIR analysis. Acrylic acid recovery is highly dependent on contact time, CaO2 nanoparticle dosage, initial acrylic concentration, and temperature. Langmuir, Freundlich, Dubinin-Radushkevich, Tempkin, Hill, Redlich-Peterson, Sips and Toth isotherms were used and well represented by Redlich-Peterson isotherm (R2 = 0.9998) as compared to other isotherms. Kinetic studies revealed pseudo-second-order kinetics (k2 = 1.962·10–4 g mg–1 min–1) for adsorption of acrylic acid onto CaO2 nanoparticles. CaO2 nanoparticles exhibited high acrylic acid recovery over varied concentration ranges. The acrylic acid can be regenerated by desorption from the surface of adsorbent and utilised for numerous applications. The presented results may be useful for the design of adsorption system using nanoparticles, which can be extended to other systems. This work is licensed under a Creative Commons Attribution 4.0 International License

Changing trends in circulating rotavirus strains in Pune, western India in 2009–2012: Emergence of a rare G9P[4] rotavirus strain

AbstractBackgroundA vast diversity in rotaviruses at inter- and intra-genotypic level underscores the need for monitoring of circulating rotavirus strains. The aim of this study was to update the data on rotavirus disease and strains for the period from January 2009 to December 2012 in Pune, western India which has been one of the sites of the Indian Rotavirus Strain Surveillance Network since November 2005.MethodsChildren aged <5 years admitted for acute gastroenteritis in three different hospitals from Pune city were included in the study. The stool specimens were collected and tested for rotavirus antigen by a commercial enzyme immunoassay. The rotavirus strains were genotyped by multiplex reverse transcription polymerase chain reaction.ResultsDuring the study period, we found 35.1% of 685 stool specimens contained rotavirus antigen. Frequency of rotavirus detection was greatest (58.5%) among children aged 7–12 months. The G1P[8] (31.4%), G2P[4] (20.2%) and G9P[8] (11.8%) strains were the most common types. We noted predominance of G1P[8] strains (39.6%-46.1%) in all the years of study except 2009 wherein G9P[8] strains scored highest level (15.3%). Subsequent to this, we identified G9P[8] strains at the second highest position in 2010, their sudden decline and rise in G9P[4] strains in 2011–2012. We detected G12 strains in combination with P[6] and P[8] at variable rates (0–10.2%) and highest level (27.1%) of mixed rotavirus infections in 2009 as compared to 2010–2012 (0–3.8%).ConclusionThe study highlights the huge burden of rotavirus disease and changing profile of circulating rotavirus strains displaying emergence of G9P[4] reassortant strains in Pune, western India and emphasizes the need to analyze the entire genomic constellation of rotavirus strains for better evaluation of the impact of rotavirus

Two days National Conference -VISHWATECH 2014 Fingerprint Identification System Based On Neural Network

Abstract : The purpose of this project is to design and develop a pattern recognition system with using Artificial Neural Network (ANN) that can recognize the type of image based on the features extracted from the choose image. Also I am comparing any two methods of neural network. This system which can fully recognizing the types of the data had been add in the data storage or called as training data. The Graphic User Interface in Neural Network toolbox is used. This is the alternative way to change the common usage of the MATLAB which are use the command insert at command window. From this kind of system, we just need to insert the features data or training data. The recognition done after we insert the test data. The system will recognize whether the output is match with the training data. Then output will produce a kind of graph that describes the feature of the data which is same as the training data

Heavily doped n++ GaN cap layer AlN/GaN metal oxide semiconductor high electron mobility transistor

In this work, we report on the processing and device characteristics of n++ GaN/AlN/GaN metal oxide semiconductor high electron mobility transistors (MOSHEMTs). The AlN/GaN structure is capped with a highly doped n++ GaN layer which provides more free electrons in the cap layer thus helps in reducing the Ohmic contact resistance. However, this layer in the gate region needs to be removed prior to gate metal deposition to avoid a conducting path between gate metal and the cap layer. A conducting path between the gate metal and GaN cap layer creates gate to source and gate to drain short circuit. A selective etching recipe was developed between n++ GaN and AlN layers. The gas used is a mixture of SF6 and O2. A 5 nm SiO2 is used as a gate dielectric and surface passivation to the device. The fabricated device shows a maximum drain current density of 800 mA/mm and a maximum peak transconductance of 135 mS/mm. The breakdown voltage of the device is 73 V. The measured contact resistance for the non-annealed and annealed Ohmic contact is between 5 to 10 Ω.mm and 0.4 to 0.6 Ω.mm, respectively. This indicates that the usage of heavily doped 5 nm n++ GaN cap layer helps in reducing the contact resistance. The results show the potential of the AlN/GaN MOSHEMT structure with a n++ GaN cap layer for future high frequency power application

High performance of n++GaN/AlN/GaN high electron mobility transistor

In this work, we report the processing and DC performance of n++GaN/AlN/GaN high electron mobility transistors with a recessed gate structure. The n++GaN cap layer is selectively removed under the gate region using SF6/O2. The fabricated device shows a maximum drain current density of over 1000 mA/mm at VGS=+3 V and a maximum peak transconductance of 240 mS/mm at VDS=5 V. The breakdown voltage of the device is over 95 V. The measured contact resistance between 0.4 to 0.6 Ω.mm is obtained using circular TLM. These results indicate the potential of n++GaN/AlN/GaN HEMT structure to be used for future high frequency power application

Investigation of plasma induced etch damage/changes in AlGaN/GaN HEMTs

In this work, we report on the processing and device characteristics of AlGaN/GaN HEMT devices to investigate the effects of silicon dioxide (SiO2) etching using Fluoroform (CHF3) gas prior to gate metal deposition. Three different GaN device structures were fabricated: (a) device #1 in which the device passivation (using SiO2) and gate metallisation are done in one lithography step, (b) device #2 in which the device passivation and gate metallization are done in 2 separate steps, (c) device #3, in which the gate metallization is deposited prior to passivation. 100 nm of plasma enhanced chemical vapor deposition (PECVD) SiO2 was deposited for surface passivation to the devices. As fabricated, devices #1 and #2 exhibited very poor device characteristics with very low output currents which we attribute to surface plasma induced damage or changes on the gate region after the SiO2 etching. A two-step post gate annealing step was performed on the devices to recover this damage. The highest maximum drain current of over 1100 mA/mm was observed on device #3 after the first anneal step compared to other devices which showed higher maximum drain current after the second anneal step. All three devices show an improvement in self-heating behavior after the second anneal step along with more stable transfer characteristics. The highest maximum peak transconductance of over 250 mS/mm was observed on devices #2 and #3 after the first anneal step. This reduces slightly for all devices but with more stable characteristics. The measured threshold voltage values (VTH) are also consistent and stable after performing the second anneal step. These results indicate that avoiding exposing the active region of GaN devices is important in achieving expected and stable characteristics. It also observed that further device improvement can be done by performing a two-step post gate annealing process