Potentiostatic study of reinforcing steel in chloride contaminated concrete powder solution extracts

This paper presents the findings of an experimental investigation of potentiostatic study on reinforcing steel in chloride contaminated concrete powder solution extracts. Various zones of corrosion for the steel reinforcement at various chloride levels have been identified. In addition the chloride concentration and pH value of these solutions were also measured. The major test variables include steel type, w/c ratio, cement content, and admixed chloride content.     

Novel Analog Calibration Technique for Current-Steering DACs’ Dynamic Performance

This paper reports the post-layout dynamic performance of a novel calibration technique for current-steering digital-to-analog converter that was proposed previously. This technique not only improves the linearity, but it does so with low power as well as a very low area. It uses an analog feedback loop consisting of four transistors to calibrate each bit of the DAC, and the same feedback circuit is used for all the bits, thus significantly saving the chip area. Layout of the 10-bit calibrated CS DAC circuit was done in a 180-nm technology; the total area of the DAC and the calibration circuit together was 0.16 \(\hbox {mm}^{2}\). Simulation results show that the spurious free dynamic range is 62 dB for signals of 1 MHz at a sampling frequency of 100 MS/s.     

Characterization and modeling of hardware imperfections in Schottky diode based six‐port modulator

This article presents digital correction for hardware imperfection in mixer‐less six‐port modulator. A passive six‐port network correlates radio frequency carrier reflected from its different ports. If the reflection coefficients at these ports are controlled by in‐phase and quadrature‐phase baseband data, the modulated information is translated directly over the radio frequency carrier without any mixing action. However, the six‐port modulator has several hardware impairments resulting into linear and nonlinear distortion. This article presents a digital characterization and distortion mitigation scheme for six‐port modulator using new quadrature interference memory polynomial model and its variant. As a proof of concept, a prototype of digitally assisted six‐port modulator is designed to modulate QAM data to radio frequency carrier at 2.0 GHz. The measurement results show the capability of modulating 16 and 64 QAM data with very low EVM less than 1.2% after employing proposed digital correction scheme.     

Information-sharing and decision-making in networks of radiation detectors

A network of sensors observes a time-inhomo-geneous Poisson signal and within a fixed time interval has to decide between two hypotheses regarding the signal’s intensity. The paper reveals an interplay between network topology, essentially determining the quantity of information available to different sensors, and the quality of individual sensor information as captured by the sensor’s likelihood ratio. Armed with analytic expressions of bounds on the error probabilities associated with the binary hypothesis test regarding the intensity of the observed signal, the insight into the interplay between sensor communication and data quality helps in deciding which sensor is better positioned to make a decision on behalf of the network, and links the analysis to network centrality concepts. The analysis is illustrated on networked radiation detection examples, first in simulation and then on cases utilizing field measurement data available through a U.S. Domestic Nuclear Detection Office (dndo) database.     

Cellulose acetate microspheres as floating depot systems to increase gastric retention of antidiabetic drug: formulation, characterization and in vitro-in vivo evaluation

Gastric emptying is a complex process that is highly variable and makes the in vivo performance of drug delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug delivery systems for more than 12 hours utilizing floating or hydrodynamically controlled drug delivery systems. The objective of this investigation was to develop a floating, depot-forming drug delivery system for an antidiabetic drug based on microparticulate technology to maintain constant plasma drug concentrations over a prolonged period of time for effective control of blood sugar levels. Formulations were optimized using cellulose acetate as the polymer and evaluated in vitro for physicochemical characteristics and drug release in phosphate buffered saline (pH 7.4), and evaluated in vivo in healthy male albino mice. The shape and the surface morphology of the prepared microspheres were characterized by optical microscopy and scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics were calculated using the linear regression method. Effects of stirring rate during preparation and polymer concentration on the size of microspheres and drug release were observed. The prepared microspheres exhibited prolonged drug release (more than 10 hours) and remained buoyant for over 10 hours. Spherical and smooth-surfaced microspheres with encapsulation efficiency ranging from 73% to 98% were obtained. The release rate decreased and the mean particle size increased at higher polymer concentrations. Stirring speed affected the morphology of the microspheres. This investigation revealed that upon administration, the biocompatible depot-forming polymeric microspheres controlled the drug release and plasma sugar levels more efficiently than plain orally given drug. These formulations, with their reduced frequency of administration and better control over drug disposition, may provide an economic benefit to the user compared with products currently available for diabetes control.     

Use of Case Studies in Engineering Education: Assessment of Changes in Cognitive Skills

Industry, educational institutions, government bodies, and academic accreditation entities have all stressed the need to incorporate sound assessment techniques into educational programs. However, many of the items listed in the Accreditation Board for Engineering and Technology 3(a–k) criteria are not commonly addressed in engineering programs. Literature has shown that case study methodology is an effective way to bridge this gap, particularly with regard to improving higher-cognitive skills. In this paper we discuss the various approaches to assessing cognitive improvements when case study methods are implemented in classrooms, along with a literature review, and the various methods are illustrated with examples. The limitations of these methods are examined and the paper concludes by stressing the need to conduct further research to identify the optimum way to assess the effectiveness of the case study methodology in engineering classrooms.     

Direct impregnation method for preparing sulfated zirconia supported on mesoporous silica

A new method has been developed to prepare sulfated zirconia (S–ZrO₂) supported on mesoporous silica. With direct exchange of metal containing precursors for the surfactants in the as-synthesized MCM-41 materials, the problem of fill-up of the mesoporous structure was avoided and high sulfur content was achieved. By using this method, the composite of S–ZrO₂/MCM-41 with ZrO₂ content higher than 60 wt.% can be easily obtained without serious blockage of the pore structure of MCM-41. Nevertheless, the pore size and pore volume of the resultant S–ZrO₂/MCM-41 composites were found to vary markedly with the loading of ZrO₂. The strong acidic character of the obtained composites was examined by using them as catalysts in n-butane isomerization. Introduction of other metals such as aluminum as promoter into S–ZrO₂/MCM-41 can be easily conducted by the direct impregnation method.     

Structure–property correlation of silicone hydrogels based on 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate monomer

We have investigated silicone-based hydrogels highlighting the effect of silyl comonomer, method of polymerization and nature of cross-linker on their bulk as well as surface properties. Transmission electron microscopy results showed that solution thermal polymerization mitigated phase segregation of hydrophobic siloxane components over bulk thermal polymerization. 2-hydroxyethyl methacrylate cannot provide transparent hydrogels with 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate alone and requires equal weight percent of N, N-dimethylacrylamide to compatibilize the comonomers to yield a silicone hydrogel network showing no microphase separation. The differentiated surface properties of silicone hydrogels containing varying amount of siloxane comonomers were also unraveled and rationally supported by surface infrared spectroscopic results. Different molecular states of water entrapped within hydrogel network were identified to understand the nature of gel-mesh functionality. The effect of silicone pendant groups on the gel elasticity was also explored.     

Importance of not skipping breakfast: a review

Breakfast is most important meal of the day and usually taken after night fast or after a long gap. Various health surveys and cross-sectional studies reported morning meal positive effect on memory recall, children performance, mood, work performance, cognitive function, women health like irregular mensuration and reduction in obesity and effect on body mass index. Still people skip breakfast throughout the world due to several reasons like lack of time, family environment, single-parent family, not feeling hunger in morning or having several misconceptions like thinking of being obese. Skipping morning meal has an adverse effect on health. This review focuses on awareness of breakfast and its positive impact on health as the breakfast skipping trend is increasing around the world and also drawing the attention of researchers to develop convenient, nutritious breakfast options and awareness programmes for significance of breakfast.     

Predictive topography model for shape adaptive grinding of metal matrix composites

Compliant finishing (e.g. shape adaptive grinding) can routinely achieve nanoscale roughness on diverse metal and ceramic materials. However, when processing multiphase materials consisting of distinct phases with different mechanical properties, non-uniform material removal often occurs and the inherent mechanism remains unclear. Here, a deterministic and stochastic model to predict processed surface topography is derived from the different material removal behaviours across phases. Experimental topographies, profiles and roughness on three selected Si-SiC samples show high consistency with theoretical predictions. Both model and experiments indicate that improved and stable surface finish can be achieved on metal matrix composites with small grain size.