Civil Engineering

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In this study, two-dimensional (plane-stress and plane-strain) theoretical models are presented for the stress analysis of adhesively bonded single-lap composite joints subjected to thermal, mechanical loads and a combination thereof. The joints consist of similar/dissimilar orthotropic or isotropic adherends and an isotropic adhesive interlayer. The governing diffierential equations of the problem are obtained using a variational method which minimizes the complementary strain energy in the bonded assembly. In this formulation, through-thickness variation of shear and peel stresses in the interlayer is considered. All the traction free boundary conditions are exactly satisfied. Peel and shear stresses obtained from plane-strain analytical models considering mono-modulus adhesive interlayer are in good agreement with the finite element predictions. A systematic parametric study is conducted to identify an ideal set of geometrical and material properties for the optimal design of joints.

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(SoE) School of Engineering

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

A variational approach for stress analysis of single-lap composite joints under mechanical and thermal loads

This article deals with the analysis of the power consumption in the piezoelectric ceramic patch of lead zirconate titanate and the losses arising from the adhesive bonding with the host structure. When a lead zirconate titanate patch is utilized as an impedance transducer in the electromechanical impedance technique, it acts both as a sensor and as an actuator (dual effect) for the range of frequency. Power consumption occurs in two forms. First part of the energy is used to actuate the lead zirconate titanate patch and produce deformations. The other part of the energy is dissipated within the piezo-mechanical system due to the internal mechanical loss and the associated heat generation. The determination of the power consumption characteristics for an active piezo-system is very important for designing an efficient intelligent structure with optimized mass and energy combination. Adhesive bond itself acts as an added stiffness, mass and damper and plays an important role in mechanical and electrical energy conversion. Hence, a detailed investigation is needed to characterize the power consumption and energy issues associated with bond layer driven by lead zirconate titanate patch, which is the main aim of this article. © The Author(s) 2014.

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Journal of Intelligent Material Systems and Structures

Influence of adhesive bond layer on power and energy transduction efficiency of piezo-impedance transducer

The severe winter haze episode that occurred in Shanghai from December 2013 to January 2014, characterized by elevated levels of particulate matter (PM), received considerable international attention because of its impacts on public health and disruption of day-to-day activities. To examine the characteristics of PM during this haze episode and to assess the chemistry behind formation of secondary inorganic aerosols (SIA) and associated health impacts due to exposure of toxic elements, we characterized eight water soluble inorganic (WSI) ions and twenty four trace elements in twelve size-fractionated PM (10 nm-9.9 μm). The average mass concentrations of coarse (1.8 μm &lt; Dp &lt; 9.9 μm), fine (Dp &lt; 2.5 μm), ultrafine (0.01 μm &lt; Dp &lt; 0.10 μm) and nano (0.01 μm &lt; Dp &lt; 0.056 μm) particles during hazy days were 2.8, 5.2, 5.3 and 5.1 times higher than those during non-hazy days, respectively. The in-situ pH (pHIS), as predicted by the Aerosol Inorganic Model (AIM-IV) in all sizes of PM, was observed to be lower during hazy days (average of -0.64) than that during non-hazy days (average of -0.29); there was an increased acidity in haze aerosols. Based on the measured concentrations of particulate-bound toxic elements, health risk assessment was conducted, which revealed that the excess lifetime carcinogenic risk to individuals exposed to fine particles under haze events increased significantly (P &lt; 0.05) to 69 ± 18 × 10-6 compared to non-hazy days (34 ± 10 × 10-6). The qualitative source attribution analysis suggested that the occurrence of haze could be due to a combination of increased emissions of PM from multiple anthropogenic sources followed by its accumulation under unfavourable meteorological conditions with lower mixing heights and less wind speeds and the formation of secondary aerosols. © 2015 Elsevier Ltd.

Atmospheric Environment

Chemical composition and acidity of size-fractionated inorganic aerosols of 2013-14 winter haze in Shanghai and associated health risk of toxic elements

An optimized protocol for induction and establishment of Agrobacterium rhizogenes-mediated hairy root cultures of Plumbago zeylanica L. was developed through selection of suitable explant type and the bacterial strain. The infection of internodal explants from an in vivo plant and leaves of in vitro origin with the A4 strain resulted in the emergence of hairy roots at a transformation frequency of 86.33 and 42.33 %, respectively. Independent transformed root somaclones (rhizoclones) capable of sustained growth were maintained under a low illumination in auxin-free agar-solidified Murashige and Skoog (MS) medium through subcultures at periodic intervals. The presence of pRi TL-DNA rolB or rolC genes and pRi TR-DNA mas2 gene in the transformed rhizoclone genome was ascertained by PCR amplification. Concentrations and type of carbon source, auxin and media strength were optimized for root biomass growth. Five independent rhizoclones each from A4- and LBA9402-transformed root lines were studied for their plumbagin accumulation at different growth phases, using HPLC analysis. The potential for plumbagin biosynthesis was expressed in all the tested rhizoclones, although distinct inter-clonal variations were noted. It was evident that maturation of hairy roots was more important for plumbagin accumulation; slow-growing and early-maturing rhizoclones accumulated more plumbagin compared to fast-growing and late-maturing rhizoclones. A4-induced rhizoclone HRA2B5 was identified as the most superior clone with a higher plumbagin yield potential in comparison with other tested hairy root clones, in vitro-grown non-transformed roots and in vivo roots of naturally occurring P. zeylanica. © 2014, Springer Science+Business Media New York.

Applied Biochemistry and Biotechnology

High-Performance Liquid Chromatographic Quantification of Plumbagin from Transformed Rhizoclones of Plumbago zeylanica L.: Inter-Clonal Variation in Biomass Growth and Plumbagin Production

Toxic elements present in airborne particulate matter (PM) are associated with human health effects; however, their toxic characteristics depend on the source of their origins and their concentrations in ambient air. Twenty four elements (Al, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Na, Ni, Pb, Se, Sr, Te, Tl, and Zn) in 12 different size fractions of PM ranging from 10 nm to 10 μm were characterized in Singapore during two different atmospheric conditions (smoke haze and non-haze periods) in 2012 for the first time. In addition, their possible sources were identified based on backward air trajectory analysis and principal component analysis (PCA). The health implications of inhalable particles were assessed using a human airway deposition model, the Multiple-Path Particle Dosimetry model (MPPD). The results concerning particle-bound trace elements are interpreted in terms of coarse (PM2.5−10), fine (PM2.5), ultrafine (PM0.01−0.1, 0.01 μm &lt; Dp &lt; 0.10 μm), and nano (PM0.01−0.056, 0.01 μm &lt; Dp &lt; 0.056 μm) particles. The ratios of elemental concentrations measured between the smoke haze episode and the non-haze period in coarse, fine, ultrafine, and nano particles varied from 1.2 (Bi) to 6.6 (Co). Both the PCA and backward trajectory analysis revealed that trans-boundary biomass-burning emissions from Indonesia were primarily responsible for enhanced concentrations of particulate-bound elements during the smoke haze episode. The particle depositions in the respiratory system were higher during the smoke haze episode compared to the non-haze period. The study finds that ultrafine and nano particles present in the atmosphere have higher tendencies to be deposited into the deeper parts of the respiratory system, compared to coarse and fine particles. © 2014, Springer-Verlag Berlin Heidelberg.

Environmental Science and Pollution Research

Characterization and estimation of human airway deposition of size-resolved particulate-bound trace elements during a recent haze episode in Southeast Asia

The characterization of aerosol acidity has received increased attention in recent years due to its influence on atmospheric visibility, climate change and human health. Distribution of water soluble inorganic (WSI) ions in 12 different size fractions of aerosols was investigated under two different atmospheric conditions (smoke-haze and non-haze periods) in 2012 using the Micro-Orifice Uniform Deposit Impactor (MOUDI) and nano-MOUDI for the first time in Singapore. To estimate the in situ acidity ([H+]Ins) and in situ aerosol pH (pHIS), the Aerosol Inorganic Model version-IV under deliquescent mode of airborne particles was used at prevailing ambient temperature and relative humidity. The study revealed an increase in the levels of airborne particulate matter (PM) mass and concentrations of WSI ions for all size fractions during the smoke-haze period, which was caused by the trans-boundary transport of biomass burning-impacted air masses from Indonesia. A bimodal distribution was observed for concentrations of SO42−, NO3−, Cl−, K+ and Na+, whereas concentrations of NH4+, Ca2+ and Mg2+ showed a single mode distribution. The concentration of WSI ions in PM1.8 during the smoke-haze period increased by 3.8 (for SO42−) to 10.5 (for K+) times more than those observed during the non-haze period. The pHIS were observed to be lower during the smoke-haze period than that during the non-haze period for all size fractions of PM, indicating that atmospheric aerosols were more acidic due to the influence of biomass burning emissions. The particles in the accumulation mode were more acidic than those in the coarse mode. © 2014, Springer Science+Business Media Dordrecht.

Environmental Geochemistry and Health

In situ acidity and pH of size-fractionated aerosols during a recent smoke-haze episode in Southeast Asia

The impedance based structural health monitoring (SHM) techniques have utilized the electro-mechanical coupling property of piezoelectric materials (piezo-impedance transducers), due to their self-sensing nature (ability to act both as actuators and sensors), and its diminutive in shape and size, cost effectiveness and ease of installation. The adhesive bond acts as an elastic medium which facilitates the transfer of stresses and strains developed due to piezo displacement and also couples the impedance of PZT patch with that of the host structure. The sensitivity of the electro-mechanical impedance (EMI) technique can be enhanced by understanding shear mechanism phenomena of the adhesive layer. This paper reviews the existing shear lag models and discuss the recent advances in impedance based coupled piezo-structural model duly considering the shear lag effect with all responsible piezo-mechanical parameters. © 2015 SPIE.

Proceedings of SPIE - The International Society for Optical Engineering

Modelling of shear lag effect for piezo-elstodynamic structure for electro-mechanical imedance technique

The most reliable method used to estimate deep percolation is using Lysimeter which proves to be expensive and time consuming as well. In this study, deep percolation has been estimated by using water balance method. The experimental setup consisted of two lysimeters in the Hydraulic Engineering field lab, I.I.T., Roorkee in which maize crop was grown. Regular measurements of soil moisture were made at the depths 0-20 cm, 20-40 cm, 40- 60 cm, 60-80 cm and 80-100 cm using gravimetric method. The evapotranspiration estimates were determined using Penman-Moneith equation. The deep percolation is calculated using the water-balance approach. The deep percolation calculated using the water-balance approach is comparable to the observed values of deep percolation which are obtained from the lysimeters.

Irrigation & Drainage Systems Engineering

Estimation of Deep Percolation in Sandy-Loam Soil using Water-balance Approach

An analysis of fatal crashes involving pedestrians in Delhi, India, from 2006 to 2009 that used a geographic information system showed clusters of crashes at certain locations. An evaluation of the characteristics of the built environment around the high crash location clusters was necessary. This paper presents an analysis of the built environment factors that influenced the safety of pedestrians. Locations surveyed included roads around the fatal crash clusters of pedestrians. Factors that influenced the number of fatal crashes of pedestrians were analyzed with negative binomial regression. Types of locations were categorized into locations with a flyover and without a flyover. Results showed that an increase in traffic volume by 1% would increase pedestrian fatal crashes by 1.6% at locations with a flyover and by 0.9% at locations without a flyover. Arterial roads with more traffic volume, more road lanes, and higher speed tended to have more fatal crashes. Locations where medians were fenced or raised in height to prevent pedestrians from crossing were also found to be associated with a greater number of crashes. These findings are useful for improving the safety of pedestrians around specific road infrastructure.

Transportation Research Record

Association between built environment and pedestrian fatal crash risk in Delhi, India

The long-term performance of any novel material in its working environment is an intriguing area of research. The combined effect of the moisture content (relative humidity) and temperature of the environment degrades the mechanical properties of polymer composites. In the first part of this manuscript, polyurea–polyhedral oligomeric silsesquioxane (POSS) nanocomposites are subjected to continuous hygrothermal cycling. The effects of prolonged hygrothermal aging on the mechanical performance of the composites are evaluated in terms of the change in tensile strength and elongation at failure. Aged composites are subjected to FTIR spectroscopy to study the chemical changes resulting from the hydrolysis of polyurea. In the second part, attempts are made to study the effect of the addition of POSS nanoreinforcement on the mechanical properties of the resulting composite materials using molecular dynamics (MD) simulations. Results obtained here show poor agreement between MD simulation results and results obtained using dynamic mechanical analysis studies. However, qualitatively, both simulation and experimental results exhibit similar effects due to addition of POSS nanoparticles on the mechanical properties of polyurea–POSS nanocomposites.