Factorial Design Approach to Investigate the Effects of Groundwater Cooccurring Solutes on Arsenic Removal by Electrocoagulation

Effects of groundwater cooccurring solutes such as phosphate (PO4), silicate (SiO3), bicarbonate (HCO3), calcium (Ca), and iron (Fe) on arsenic removal were investigated in this study. Investigation by two-level full-factorial designed experiments revealed that PO4 and SiO3 have negative effect on arsenic removal, whereas HCO3 has negligible positive effect. The effects of Ca and Fe present in groundwater have positive effect on arsenic removal by electrocoagulation (EC). Hypothesis testing at 5% significance level suggests that alkalinity (HCO3) is not an important parameter in arsenic removal by EC in naturally occurring pH range of water.     

Prediction of Arsenic Removal by Electrocoagulation: Model Development by Factorial Design

Model was developed by two-level five-factor full-factorial designed-experiment to predict arsenic removal from contaminated water by electrocoagulation. Five factors, namely arsenic concentration (As), solution volume (V); current (I), electrode area (A), and current processing time (t) were investigated. Among the factors, arsenic concentration (As) and volume (V) have negative effect, and area (A), time (t), and current (I) have positive effect on arsenic removal. Within the studied levels of the factors, variance analysis at 5% significance level indicated that electrode area is not significant in arsenic removal by electrocoagulation. The model predicted reasonably good arsenic removal (error<2%) from low (0.288 mg/L) and high (0.882 mg/L) initial arsenic concentrations in presence of naturally cooccurring solutes in the groundwater. For the range of operating variables studied, optimum removal of arsenic (98.56%) is obtained at higher arsenic concentration (1.18 mg/L), lower volume (1 L), higher current (3 A), and higher current processing time (120 s).     

Intersubband transitions and ultrafast all-optical modulation usingmultiple InGaAs-AlAsSb-InP coupled double-quantum-well structures

InP-based InGaAs-AlAs-AlAsSb coupled double-quantum-well structures have been optimized using wave-function engineering techniques to achieve near-infrared intersubband (ISB) transitions. Intersubband transitions at communication wavelengths of 1.3 and 1.55 μm can be achieved in both near-symmetric and asymmetric coupled quantum-well structures by tailoring the well width, the central barrier width, and the carrier population in the conduction subband states by controlling either the doping level or the carrier temperature. We demonstrate ultrafast all-optical modulation of interband-resonant light at 1.3 μm using intersubband-resonant light pulses at 1.55 μm. An ultrafast absorption recovery time of 1.3 ps has been observed at 1.3 μm, which can be reduced to 800 fs by probing at a higher energy above the Fermi level in the conduction band     

Use of a novel set of features based on texture anisotropy for identification of liver steatosis from ultrasound images: a simple method

Multimedia Tools and Applications - Detection of fatty liver disease (steatosis) from the ultra sound (US) images using pattern recognition techniques is attempted by many authors. Different...     

A 4 bit highly energy and area efficient SC SAR ADC based on a combinational technique with reduced reset energy

A combinational method, based on hybrid and junction splitting techniques, is used to realize a 4 bit high energy efficient SC SAR ADC. The hybrid switching scheme is very energy efficient in which the first three comparison cycles do not consume any energy. In junction split technique, the total value of capacitors does not remain constant. Rather capacitors are appended as bits are being determined successively. The present method combines the features of these two methods to realize an even more energy efficient SC SAR ADC. Reset energy, in some cases, can seriously impact the overall efficiency of a SC SAR ADC. A study has been made about the normal reset energy and two step reset energy for the different cases. A table has been drawn to show the overall energy efficiency for normal conversion, conversion with single step reset and lastly conversion with two step reset for all the architectures.

     

Sorption of methylene chloride in polyethylene terephthalate

Sorption of methylene chloride in polyethylene terephthalate has been performed at three different temperatures: 21, 34, and 48°C. The solubility data are explained through dual sorption. The diffusivities are more difficult to explain since some anomalous effects were present.     

Performance improvement of PI controllers through dynamic set-point weighting

Responses of high-order systems under Ziegler-Nichols tuned PI controllers (ZNPIs) are characterized by excessive oscillation with a large overshoot. Although, a fixed set-point weighting based PI controller (FSWPI) may decrease the overshoot considerably, it fails to reduce the oscillation in the set-point response. Moreover, both FSWPI and ZNPI exhibit equally poor load regulation. Keeping in mind an overall improved performance, we propose an online dynamic set-point weighting technique for ZNPIs. The dynamic set-point weighting factor (β_d) is heuristically derived from the instantaneous process trend. Performance of the proposed dynamic set-point weighting based PI controller (DSWPI) for various second- and third-order processes including a pH process shows a significant improvement during both the set-point and load disturbance responses over other methods. Stability and robustness of the proposed DSWPI are addressed. Effectiveness of the DSWPI is demonstrated through the real-time implementation on a practical DC position control system.     

A multiscale model for quantifying helium diffusion in porous unsintered glass

Helium‐aided sintering of porous unsintered glass is a complex multiscale process, characterised by three different timescales, namely, that of helium diffusion, heat conduction, and radial shrinkage of the glass core. This work presents a multiscale model for quantifying heat and helium diffusion in a shrinking core system by decoupling the timescales based on their orders of magnitude. We obtain analytical solutions of our model, which allow us to quantify the spatio‐temporal profiles of temperature and helium concentration in the glass during the sintering process. Our results show that the introduction of helium increases the sintering rate of glass, and we conclude that pre‐sintering heating followed by helium‐aided sintering is better than simultaneous heating and helium diffusion. We also show that the pre‐sintering heating process for a standard glass sample should not be longer than an hour for the sake of heat economy, following which we may switch to the helium‐aided sintering process, where the sintering should occur under isothermal conditions for approximately 6 h. We perform dynamic simulations using glass porosity as a parameter, and find the sintering rate to be directly proportional to the initial porosity of the glass sample.     

Preparation and characterization of thin films of the poly(p‐phenylene vinylene) semiconducting polymer

Conjugated polymers have been the subject of many studies because of their widespread applications in electronic and optoelectronic devices. Poly(p‐phenylene vinylene) is a leading semiconducting polymer in optical applications. This work is focused on the development of thin films of poly(p‐phenylene vinylene) by spin coating and their characterization with Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy to understand their changes. An empirical model has been developed to show the effect of the variables—the spin speed, polymer concentration, and spin time—on the film thickness. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009