High Precision SAR ADC Using CNTFET for Internet of Things

A high precision 10-bit successive approximation register analog to digital converter (ADC) designed and implemented in 32nm CNTFET process technology at the supply of 0.6V, with 73.24 dB SNDR at a sampling rate of 640 MS/s with the average power consumption of 120.2 μW for the Internet of things node. The key components in CNTFET SAR ADCs are binary scaled charge redistribution digital to analog converter using MOS capacitors, CNTFET based dynamic latch comparator and simple SAR digital code error correction logic. These techniques are used to increase the sampling rate and precision while ensuring the linearity, power consumption and noise level are within the limit. The proposed architecture has high scalability to CNTFET technology and also has higher energy efficiency. We compared the results of CNTFET based SAR ADC with other known architectures and confirm that this proposed SAR ADC can provide higher precision, power efficiency to the Internet of things node.     

Gaussian Support Vector Machine Algorithm Based Air Pollution Prediction

Air pollution is one of the major concerns considering detriments to human health. This type of pollution leads to several health problems for humans, such as asthma, heart issues, skin diseases, bronchitis, lung cancer, and throat and eye infections. Air pollution also poses serious issues to the planet. Pollution from the vehicle industry is the cause of greenhouse effect and CO2 emissions. Thus, real-time monitoring of air pollution in these areas will help local authorities to analyze the current situation of the city and take necessary actions. The monitoring process has become efficient and dynamic with the advancement of the Internet of things and wireless sensor networks. Localization is the main issue in WSNs; if the sensor node location is unknown, then coverage and power and routing are not optimal. This study concentrates on localization-based air pollution prediction systems for real-time monitoring of smart cities. These systems comprise two phases considering the prediction as heavy or light traffic area using the Gaussian support vector machine algorithm based on the air pollutants, such as PM2.5 particulate matter, PM10, nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and sulfur dioxide (SO2). The sensor nodes are localized on the basis of the predicted area using the meta-heuristic algorithms called fast correlation-based elephant herding optimization. The dataset is divided into training and testing parts based on 10 cross-validations. The evaluation on predicting the air pollutant for localization is performed with the training dataset. Mean error prediction in localizing nodes is 9.83 which is lesser than existing solutions and accuracy is 95%.     

Dielectric and conductivity studies on cobalt phthalocyanine tetramers

Electrically conductive organic and metalloorganic polymers are of great interest and they have applications in electronic, optical, photonic, photoelectric, electrochemical, and dielectric devices. Tetrameric cobalt phthalocyanine was prepared by conventional chemical method. The dielectric permittivity of the tetrameric cobalt phthalocyanine sample was evaluated from the observed capacitance values in the frequency range 100 KHz to 5 MHz and in the temperature range of 300 to 383°K. It is found that the system obeys the Maxwell Wagner relaxation of space charge phenomenon. Further, from the permittivity studies AC conductivity was evaluated. The values of AC conductivity and DC conductivity were compared. Activation energy was calculated. To understand the conduction mechanism Mott's variable range hopping model was applied to the system. The T^?1/4 behavior of the DC conductivity along with the values of Mott's Temperature (T₀), density of states at the Fermi energy N (E_F), and range of hopping R and hopping energy W indicate that the transport of charge carriers are by three‐dimensional variable range hopping. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2529–2535, 2004     

Causes of seepage water in drainage and grouting galleries of the Pandoh Dam, Central Himalaya

At the Pandoh Dam in the Central Himalaya, a reddish brown material was observed seeping through drainage holes in three of the galleries. Initially considered to be phyllitic oxide, this was chemically analysed and found to be sulphate radicals. A sulphate concentration of 861.50 ppm was recorded in the seepage water. Petrography of the bedrocks and X-ray analysis of the suspended reddish brown powder as well as chemical analysis of the seepage water revealed the presence of chalcopyrite, pyrrhotite and the conversion of monosulphate phases into ettringite phases as the major cause of expansion and seepage. This process is accompanied by a significant volume increase which it was concluded was responsible for the internal stresses causing the cracking through which the seepage water entered the drainage and grouting galleries.     

Poly(amino acid)-facilitated electrochemical growth of metal nanoparticles

Poly(amino acids) are natural chelating agents for various metal ions. Zinc ions were encapsulated in situ in a conductive polypyrrole film using polyglutamic acid as a localized complexing agent within the film. The subsequent electrochemical reduction of the metal ions to zero-valent metal leads to the formation of the nanoparticles. The electrochemical approach demonstrated in this report provides facile regeneration of the particles and also prevents aggregation of nanoparticles in the conductive polymeric film. The correlation of the amount of zinc with the thickness of the film indicates that the zinc resides largely in the outer layer of the film. TEM and EDS data show that the nanoparticles formed are composed of zinc and are 18 +/- 7 nm in diameter. The nanoparticle/ polymer composite was used to reduce halogenated organics, indicating its potential usefulness in remediation applications.     

Improving the mechanical properties of 2024 Al alloy by cryo rolling

Ultra fine grained (1 micron size) materials usually exhibit more strength. Most of the approaches to refine microstructure lead to decrease in ductility. Cryo rolling is a successful technique; samples are rolled at cryogenic temperature, to improve strength of an age hardenable alloy with minimum loss in ductility. Aging after cryo rolling ensures good strength and ductility due to bimodal structure and nano sized precipitation of S’ phase. Al 2024 alloy are partially solutionised to retain some T-phase particles, which are very effective in accumulating dislocations during cryo-rolling, and in turn promoted the precipitation of Al₂CuMg precipitates with a size of 10–40 nm. The nano sized Al₂CuMg precipitates and bimodal grain structure leads to simultaneous increases in strength and ductility.     

Synthesis and evaluation of trimethylolpropane triacrylate crosslinked superabsorbent polymers for conserving water and fertilizers

A series of superabsorbent polymers (SAP) were synthesized by free radical thermal copolymerization of acrylic acid and N‐isopropyl acrylamide monomers using trimethylolpropane triacrylate as crosslinker. They were characterized by FT‐IR and thermal stability (TGA/DTG), and evaluated for their water and fertilizer uptake and release characteristics under different crosslinker levels, temperature, pressure, and pH. The observed maximum absorption of water by the SAP was 1130 g/g of polymer. The release was modeled which showed a non‐Fickian mechanism. The water uptake of SAP was correlated with the average molecular weight between the crosslinks and crosslink density. Analysis of the weight loss data from TG in air revealed a zero order kinetics for the initial degradation step with an activation energy (AE) of 70.8 kJ/mol. The AEs for water uptake and release for thermal degradation were also determined through Arrhenius plots. The results inferred that the synthesized SAP can be exploited for commercial agricultural applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

CuInxGa1−xSe2 thin films prepared by electron beam evaporation

CuIn_xGa_1−xSe₂ bulk compound of three different compositions x=0.75, 0.80 and 0.85 have been prepared using individual elements of copper, indium, gallium and selenium. Thin films of CuIn_xGa_1−xSe₂ have been deposited using the prepared bulk by electron beam evaporation method. The structural studies carried on the deposited films revealed that films annealed at 400 °C are crystalline in nature exhibiting chalcopyrite phase. The position of the (1 1 2) peak in the X-ray diffractogram corresponding to the chalcopyrite phase has been found to be dependent on the percentage of gallium in the films. The composition of the prepared bulk and thin films has been identified using energy dispersive X-ray analysis. The photoluminescence spectra of the CuIn_xGa_1−xSe₂ films exhibited sharp luminescence peaks corresponding to the band gap of the material.     

Poly(m‐phenylenediamine)‐coated 316L SS: A promising material for bipolar plates in PEMFC environment

The applicability of conducting polymer coatings to enhance corrosion resistance of bipolar plates in proton exchange membrane fuel cells (PEMFC) is gaining greater significance as electrical conductivity is as important as corrosion resistance. Metaphenylenediamine (mPD) monomer was electropolymerized to poly(m‐phenylenediamine) (PmPD) conducting polymer over 316L SS and characterized by attenuated total reflectance infrared spectroscopy to confirm the formation of P mPD polymer. Scanning electron microscopy was used to study the surface morphology of the polymer. Open‐circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies were conducted to assess the corrosion protection performance of the PmPD polymer coating in PEMFC environment. The charge‐transfer resistance measured from EIS for the coated substrates was higher than the uncoated substrate. Potentiodynamic polarization studies showed lower corrosion current density for the PmPD‐coated substrates. All the results proved that the PmPD‐coated substrates could exhibit enhanced corrosion resistance in PEMFC environment.     

Sea urchin shaped ZnO coupled with MoS2 and polyaniline as highly efficient photocatalysts for organic pollutant decomposition and hydrogen evolution

In this work, an attempt has been made to fabricate multifunctional composite photocatalysts by coupling sea urchin shaped ZnO with MoS₂ and polyaniline (PANI) sheets, and a significant improvement in photocatalytic activity was perceived with composites in comparison to pristine components. It was found that the ternary ZnO–MoS₂-PANI photocatalyst showed excellent adsorptive decomposition of organic pollutants natural sunlight irradiation. In addition, enhanced photocatalytic hydrogen evolution was also evidenced, which revealed the multifunctional nature of the photocatalysts. In the case of organic pollutant decomposition, the presence of MoS₂ in ZnO–MoS₂-PANI offers abundant catalytic active sites which result in adsorption of the pollutants and boost the photocatalytic activity. While for the photocatalytic hydrogen evolution, the binary ZnO-PANI composite showed the utmost activity in comparison to the pristine components and ZnO–MoS₂-PANI, which is due to the fact that the higher loading of MoS₂ in the composite increases the number of S atoms on the basal planes, which are inactive for H₂ evolution, and hence results in decreased photocatalytic activity. The results discussed in this work may pave the approach for the design and development of ZnO based multifunctional materials for diverse photocatalytic applications.