Civil Engineering

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Shiv Nadar University

The effect of microfabric on the mechanical behaviour of clays has been explored previously based on the response of dispersed and flocculated microfabrics only. However, the natural clays often have the geometric arrangement of particles between these two extreme cases which can be termed as intermediate microfabric. This paper explores the formation of intermediate microfabric of kaolin clay and its impact on soil's consolidation behaviour by performing self-weight consolidation, slurry consolidation and 1-D consolidation tests. The effect of calgon content (dispersing agent) on geometric arrangement of the particles has been evaluated through cluster size distribution by performing double hydrometer tests. Then these clay slurries have been used to perform the AFM (Atomic Force Microscopy) test to obtain the variation in average angle of particle orientation with respect to the calgon content present in the slurry. AFM technique provides 3D image of the clay sample and 2D image with Z-information with the potential of measuring intermediate microfabric of clayey soil quantitatively including dispersed and flocculated microfabrics. Other traditional techniques such as SEM, TEM & XRD are limited to only qualitative analysis of soil's microfabric, thus, having no capability to measure intermediate microfabric of clay. A methodology of preparing bulk specimens of clay with intermediate microfabric has been developed using slurry consolidation technique; and then these specimens have been consolidated under 1-D loading to evaluate the effect of intermediate microfabric on compressibility and permeability of clay. In this study, all the experiments reports that the dispersed type geometric arrangement increases with the increase in calgon content in soil up to 2 % and then the reverse behaviour is observed at 3 %; which may depend on the required amount of sodium cations to neutralize the negatively charged faces of the clay platelets present in the slurry. © 2012 Springer Science+Business Media Dordrecht.

World University root node

(SoE) School of Engineering

Geotechnical and Geological Engineering

Development of Intermediate Microfabric in Kaolin Clay and Its Consolidation Behaviour

During the last two decades, active research has gone into the theoretical and the practical aspects of the electro-mechanical impedance (EMI) technique for structural health monitoring (SHM). This paper reviews the theoretical developments in modelling the force transfer mechanism between the piezoelectric-ceramic (PZT) patch and the host structure pertinent to the EMI technique. The review covers the modelling efforts spanning about last one and a half decades. The models reviewed include the shear lag based model, simplified shear lag model, the refined shear lag model and the continuum shear lag model. The first three listed models ignored the inertia term. The last model, that is the continuum based model, takes care of all the piezo, structural and adhesive effects rigorously and simultaneously. Typical comparisons between the outcomes resulting from the models are discussed. © (2013) Trans Tech Publications.

Key Engineering Materials

Modelling of piezo-bond structure system for structural health monitoring using EMI technique

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3. © 2013 Springer-Verlag Berlin Heidelberg.

Environmental Science and Pollution Research

Ammonia in the atmosphere: A review on emission sources, atmospheric chemistry and deposition on terrestrial bodies

Physical, mechanical and chemical aging of polyurea nanocomposites

The performance (sensing/actuating) of a piezotransducer highly depends upon the ability of the bond layer to transfer the stress and strain (through shear lag mechanism) between the transducer and the structure. Therefore, the coupled electromechanical response of the piezotransducer should consider the effect of dynamic behaviour, geometry and composition of the adhesive layer used to bond the transducer patch on the structure. This article presents a new refined analytical model for inclusion of the shear lag effect in modelling of adhesively bonded piezoelectric ceramic (lead zirconate titanate) patches for consideration in the electromechanical impedance technique. The previous models neglected the inertial term in shear lag formulations for simplicity. The present refined model, on the other hand, considers the inertial and the shear lag effects simultaneously, and is therefore more rigorous and complete. In this article, the formulations are first derived for one-dimensional case, and then extended to two-dimensional lead zirconate titanate-structure interaction. The overall results are found to be in better proximity to experimental observations. The refined formulations are employed for a detailed stress analysis of the bond layer. The article concludes with a parametric study on the influence of various sensor parameters on the electromechanical impedance signatures. © The Author(s) 2012.

Fulltext

Journal of Intelligent Material Systems and Structures

A refined shear lag model for adhesively bonded piezo-impedance transducers

Aerosol acidity is one of the most important parameters that can influence atmospheric visibility, climate change and human health. Based on continuous field measurements of inorganic aerosol species and their thermodynamic modeling on a time resolution of 1h, this study has investigated the acidic properties of PM2.5 and their relation with the formation of secondary inorganic aerosols (SIA). The study was conducted by taking into account the prevailing ambient temperature (T) and relative humidity (RH) in a tropical urban atmosphere. The in-situ aerosol pH (pHIS) on a 12h basis ranged from -0.20 to 1.46 during daytime with an average value of 0.48 and 0.23 to 1.53 during nighttime with an average value of 0.72. These diurnal variations suggest that the daytime aerosol was more acidic than that caused by the nighttime aerosol. The hourly values of pHIS showed a reverse trend as compared to that of in-situ aerosol acidity ([H+]Ins). The pHIS had its maximum values at 3:00 and at 20:00 and its minimum during 11:00 to 12:00. Correlation analyses revealed that the molar concentration ratio of ammonium to sulfate (RN/S), equivalent concentration ratio of cations to anions (RC/A), T and RH can be used as independent variables for prediction of pHIS. A multi-linear regression model consisting of RN/S, RC/A, T and RH was developed to estimate aerosol pHIS.. © 2013 Elsevier B.V.

Science of the Total Environment

A study of diurnal variations of PM2.5 acidity and related chemical species using a new thermodynamic equilibrium model

This study has investigated the chemical association among acidic gases, ammonia and secondary inorganic aerosols based on hourly measurements in a tropical urban atmosphere. The 24 hr average concentrations of SO2, NH3, HONO, HNO3 and HCl were 21.77, 2.47, 1.73, 3.00 and 0.08 μg/m3, respectively while those of SO42-, NO3-, Cl-, Na+, K+, NH4+, Ca2+ and Mg2+ in PM2.5 were 4.41, 1.29, 0.28, 0.30, 0.32, 1.76, 0.14 and 0.07 μg/m3, respectively. The results of this study for SO2, NH3, HONO, HCl, SO42- and Cl- showed significant diurnal variations, whereas there was a lack of significant diurnal variations for HNO3, NO3-, Na+, NH4+, Ca2+ and Mg2+. Analysis of the charge balance of ionic species indicated that sufficient NH3 was present most of the time to neutralize both H2SO4 and HNO3 to form (NH4)2SO4 and NH4NO3. The conversion of SO2 into SO42- and HNO3 into NO3- was observed to be sensitive to changes in temperature and relative humidity, respectively. The study area experienced ambient relative humidity, which was higher than the estimated deliquescence relative humidity of NH4NO3 most of the time during the measurement period. As a result, the NH4NO3 formation was thermodynamically favorable during both daytime and nighttime. However, NH4Cl formation was not favored under ammonia-poor conditions. It was observed that biomass burning could trigger nitrate and chloride formation in the ambient air. © Taiwan Association for Aerosol Research.

Aerosol and Air Quality Research

Insights into chemical coupling among acidic gases, ammonia and secondary inorganic aerosols

The piezoelectric patches have started to play an important role in continuous online health monitoring of structures in recent years because of their diminutive shape, cost effectiveness and easy installation process. The research for structural identification and force transfer phenomena has recently become an area of interest researchers working in PZT related structural health monitoring. The PZT patch allow the systems and structures to monitor their own structural integrity while in operation and throughout their life, and are useful not only to improve reliability but also to reduce maintenance and inspection cost of systems and structures specifically, in the electro-mechanical impedance (EMI) technique based SHM, the PZT patches are either embedded or bonded with adhesive to the host structure to be monitored. When bonded on the surface of the structure, the adhesive bond forms an interfacial layer of finite thickness between the patch and host structure. The performance (sensing/actuating) of piezo transducer depends upon the ability of the bond layer to transfer the stresses and strains between the active PZT patch and the host structures. The mechanical and geometrical properties of the adhesive bond layer change the overall performance of the PZT-structure interaction model. The main objective of this paper to review the shear lags models developed so far and discuss their effective applicability EMI technique.

Structural Health Monitoring 2013: A Roadmap to Intelligent Structures - Proceedings of the 9th International Workshop on Structural Health Monitoring, IWSHM 2013

Investigation of shear force mechanism in electro-mechanical impedance (EMI) technique for structural health monitoring

Introduction: The kinetics of the transformation of ammonia and acid gases into components of PM2.5 has been examined. The interactions of existing aerosols and meteorology with the transformation mechanism have also been investigated. The specific objective was to discern the kinetics for the gas-to-particle conversion processes where the reactions of NH3 with H2SO4, HNO3, and HCl take place to form (NH4)2SO4, NH4NO3, and NH4Cl, respectively, in PM2.5. Materials and methods: A Teflon-based outdoor environmental chamber facility (volume of 12.5 m3) with state-of-the-art instrumentation to monitor the concentration-time profiles of precursor gases, ozone, and aerosol and meteorological parameters was built to simulate photochemical reactions. Results and discussion: The reaction rate constants of NH3 with H2SO4, HNO3, and HCl (i. e., kS, kN, and kCl) were estimated as (1) kS = 2.68 × 10-4 (±1.38 × 10-4) m3/μmol/s, (2) kN = 1.59 × 10-4 (±8. 97 × 10-5) m3/μmol/s, and (3) kCl = 5.16 × 10-5 (±3.50 × 10-5) m3/μmol/s. The rate constants kS and kN showed significant day-night variations, whereas kCl did not show any significant variation. The D/N (i. e., daytime/nighttime values) ratio was 1.3 for kS and 0.33 for kN. The significant role of temperature, solar radiation, and O3 concentration in the formation of (NH4)2SO4 was recognized from the correlation analysis of kS with these factors. The negative correlations of temperature with kN and kCl indicate that the reactions for the formation of NH4NO3 and NH4Cl seem to be reversible under higher temperature due to their semivolatile nature. It was observed that the rate constants (kS, kN, and kCl) showed a positive correlation with the initial PM2.5 levels in the chamber, suggesting that the existing surface of the aerosol could play a significant role in the formation of (NH4)2SO4, NH4NO3, and NH4Cl. Conclusions: Therefore, this study recommends an intelligent control of primary aerosols and precursor gases (NOx, SO2, and NH3) for achieving reduction in PM2.5 levels. © 2011 Springer-Verlag.

Transformation of atmospheric ammonia and acid gases into components of PM2.5: An environmental chamber study

The rapid increase in anthropogenic nitrogen emissions to the atmosphere is matter of concern for the environment, as these may lead to photochemical air pollution, reduced visibility, eutrophication of surface waters, changes in biodiversity, acid rain, stratospheric ozone depletion, and global warming. In this study, ambient emissions of reactive nitrogen (ammonia and nitrous oxide) from animal and crop farming are analyzed for the base year 2003. This objective was achieved by the systematic development of a spatially resolved emissions inventory on a Geographic Information System (GIS) platform. Emissions of ammonia (NH 3) and nitrous oxide (N 2O) were estimated: (i) from livestock; 1705-Gg/yr and 214-Gg-yr -1 and (ii) fertilizer applications; 2697-Gg-yr -1 and 326-Gg-yr -1. These estimated emissions were compared and contrasted with global, U.S., and European emissions of reactive nitrogen; emissions from India were second only to China. From the spatially resolved emission inventory, it was observed that the state of Uttar Pradesh has the highest NH 3 emission (522-Gg-yr -1) followed by the state of Maharashtra (425-Gg-yr -1) both from animal and crop farming. Similarly the State of Uttar Pradesh has the highest N 2O emission (70-Gg-yr -1) followed by the state of Maharashtra (47-Gg-yr -1). © 2011 Elsevier Ltd.