Construction waste: source identification, quantification and its management in housing projects

Waste in construction is important not only from the perspective of productivity but also from the environmental considerations. Many times actual percentage of waste generation is much higher than envisaged initially causing needless utilization of resources. It means there is a plenty of scope for enhancing project productivity simply by taking waste out of construction. Disposing of waste is not the right solution. Many countries are facing the problem of scarcity of dumping yards and exhaust of landfill spaces forcing researchers to look for an alternate and efficient waste management system. The literature review is carried out to identify construction waste management techniques being used in the construction industry. An attempt is made in this paper to quantify concrete waste and locate causes of its generation in housing projects. Research study observations are derived from the data analysis of five building projects located in different cities of Maharashtra state in India. The average level of concrete waste is 4.7 % of the estimated quantity that is more than double the permissible standard of 2 %. Three approaches of waste minimization - waste as project management function, ARRRD and value chain are discussed giving the guideline to design waste management plan

All-optically induced ultrafast photocurrents: Beyond the instantaneous coherent response

It is demonstrated that the non-instantaneous response of the optically induced coherent polarization tremendously influences the real-space shift of electronic charges in semiconductors. The possibility to coherently control this real-space shift with temporally non-overlapping excitation pulses allows for the observation of a new type of shift current, which only exists for certain polarization-shaped excitation pulses and vanishes in the continuous-wave limit. In contrast to previously studied shift currents, the new current requires a phase mismatch between two orthogonal transition dipole moments and leads, within a nonlinear second-order description, to a tensor which is antisymmetric with respect to the order of the two exciting electric field amplitudes. These observations, which can even be made at room temperature and are expected to occur in a variety of semiconductor crystal classes, contribute to a better understanding of light-matter interaction involving degenerate bands. Thus, they are expected to prove important for future studies of coherent and nonlinear optical effects in semiconductors

Towards a Hybrid Public Key Infrastructure (PKI): A Review

Traditional Certificate-based public key infrastructure (PKI) suffers from the problem of certificate overhead like its storage, verification, revocation etc. To overcome these problems, the idea of certificate less identity-based public key cryptography (ID-PKC) was proposed by Shamir. This is suitable for closed trusted group only. Also, this concept has some inherent problems like key escrow problem, secure key channel problem, identity management overhead etc. Later on, there had been several works which tried to combine both the cryptographic techniques such that the resulting hybrid PKI framework is built upon the best features of both the cryptographic techniques. It had been shown that this approach solves many problems associated with an individual cryptosystem. In this paper, we have reviewed and compared such hybrid schemes which tried to combine both the certificate based PKC and ID-based PKC. Also, the summary of the comparison, based on various features, is presented in a table

Dual frequency ultrasonic liquid phase exfoliation method for the production of few layer graphene in green solvents

In this work, we implement a dual frequency (24 kHz and 1174 kHz) ultrasonic assisted liquid phase exfoliation (ULPE) technique in deionized water (DIW) and other eco-friendly solvents, to produce a variety of high-quality few-layer graphene (FLG) solutions under controlled ultrasonication conditions. The resulting FLG dispersions of variable sizes (∼0.2–1.5 μm2) confirmed by characterisation techniques comprising UV–Vis spectroscopy, Raman spectroscopy and high-resolution transmission electron microscopy (HR-TEM). For the first time we demonstrate that high yield of FLG flakes with minimal defects, stable for 6 + months in a solution (stability ∼ 70 %), can be obtained in less than 1-hour of treatment in either water/ethanol (DIW:EtOH) or water/isopropyl alcohol (DIW:IPA) eco-friendly mixtures. We also scrutinized the underlying mechanisms of cavitation using high-speed imaging synchronized with acoustic pressure measurements. The addition of ethanol or IPA to deionized water is proposed to play a central role in exfoliation as it regulates the extend of the cavitation zone, the intensity of the ultrasonic field and, thus, the cavitation effectiveness. Our study revealed that lateral sizes of the obtained FLG depend on the choice of exfoliating media and the diameter of a sonotrode used. This variability offers flexibility in producing FLG of different sizes, applicable in a wide spectrum of size-specific applications

Temperature as a key parameter for graphene sono-exfoliation in water

Graphene dispersions in water are highly desirable for a range of applications such as biomedicines, separation membranes, coatings, inkjet printing and more. Recent novel research has been focussed on developing a green approach for scalable production of graphene. However, one important parameter, which is often neglected is the bulk temperature of the processing liquid. This paper follows our earlier work where optimal sono-exfoliation parameters of graphite in aqueous solutions were determined based on the measured acoustic pressure fields at various temperatures and input powers. Here, we take the next step forward and demonstrate using systematic characterisation techniques and acoustic pressure measurements that sonication-assisted liquid phase exfoliation (LPE) of graphite powder can indeed produce high quality few layer graphene flakes in pure water at a specific temperature, i.e. 40 °C, and at an optimised input generator power of 50%, within 2-h of processing. UV–vis analysis also revealed that the exfoliation, stability and uniformity of dispersions were improved with increasing temperature. We further confirmed the successful exfoliation of graphene sheets with minimal level of defects in the optimized sample with the help of Raman microscopy and transmission electron microscopy. This study demonstrated that understanding and controlling processing temperature is one of the key parameters for graphene exfoliation in water which offers a potential pathway for its large-scale production

An eco-friendly solution for liquid phase exfoliation of graphite under optimised ultrasonication conditions

Ultrasonic assisted liquid phase exfoliation (ULPE) is a promising method for the large scale production of 2D materials. Currently, toxic solvents such as N-Methyl-2-pyrrolidone (NMP) are commonly used for the production of graphene. In this paper four solvents; three green solvents (water, ethanol and water/ethanol) plus NMP for comparison, were sonicated and examined in terms of their bubble dynamics and acoustic emissions. Advanced fundamental analysis was conducted using high-speed imaging synchronised with acoustic pressure measurements complemented by shadowgraphic photography of the emitted shockwaves, in order to determine a suitable eco-friendly solvent medium from a cavitation bubbles dynamics perspective. Thereafter, ULPE of graphite in the optimum solvent took place for 2 h under controlled ultrasonication parameters. The produced graphene samples were characterised by employing a series of techniques consisting of Ultraviolet–visible (UV–Vis) and Raman spectroscopy as well as transmission electron microscopy (TEM). A mixture of deionised water and ethanol was shown to produce a yield twice that of pure water, comprising of high quality few layer graphene (3–5 Ls) with an average area of ∼1.15 (μm)2 and stability of ∼78% for the duration of six months. This combination is a promising eco-friendly substitute for future commercial manufacturing of graphene

Ssr-based molecular profiling of selected donors of wide compatibility, elongated uppermost internode, stigma exsertion and submergence tolerance traits and parental lines of commercial rice (o. Sativa l.) Hybrids

Molecular breeding plays an important role in sustainable agriculture development. Hybrid rice technology aims to increase the yield potential of rice beyond the level of inbred high-yielding varieties (HYVs) by exploiting the phenomenon of hybrid vigour or heterosis. Improvement of hybrid rice parental line is necessary to meet the food security problem. Parental polymorphism was carried with 215 SSR markers between five recurrents and ten donors. During the foreground selection, both reported markers (S5-Indel and BF-S5) were validated for wide compatibility, 2 out of 14 (ART5 and SC3) validates for submergence tolerance, one out of two (RM5) validate for stigma exsertion, whereas 2 of 3 markers (RM5970, RM3476) validated for elongated uppermost internode traits between recurrents and donors. For background selection, maximum polymorphic markers (112) between IR58025eB i.e improved maintainer line with elongated uppermost internode and Oryza meridionalis and minimum polymorphic markers (42) between IR79156B and IR91-1591-3 were found. Marker-assisted backcrossing accelerate, the transfer of gene of interest in desirable genetic background. Genotypes IR58025B and IR58025eB emerged as genetically most similar with a value of 97%. The genotypes IR64 Sub1 and Oryza meridionalis were found most divergent showing 33% genetic similarity. Dissimilarity coefficient of the generated information obtained on genetic relatedness would be supportive in further rice breeding program

Temperature as a key parameter for graphene sono-exfoliation in water

Graphene dispersions in water are highly desirable for a range of applications such as biomedicines, separation membranes, coatings, inkjet printing and more. Recent novel research has been focussed on developing a green approach for scalable production of graphene. However, one important parameter, which is often neglected is the bulk temperature of the processing liquid. This paper follows our earlier work where optimal sono-exfoliation parameters of graphite in aqueous solutions were determined based on the measured acoustic pressure fields at various temperatures and input powers. Here, we take the next step forward and demonstrate using systematic characterisation techniques and acoustic pressure measurements that sonication-assisted liquid phase exfoliation (LPE) of graphite powder can indeed produce high quality few layer graphene flakes in pure water at a specific temperature, i.e. 40 °C, and at an optimised input generator power of 50%, within 2-h of processing. UV–vis analysis also revealed that the exfoliation, stability and uniformity of dispersions were improved with increasing temperature. We further confirmed the successful exfoliation of graphene sheets with minimal level of defects in the optimized sample with the help of Raman microscopy and transmission electron microscopy. This study demonstrated that understanding and controlling processing temperature is one of the key parameters for graphene exfoliation in water which offers a potential pathway for its large-scale production