The COVID-19 pandemic and the ensuing socioeconomic crisis has impeded progress towards the UN Sustainable Development Goals (UN-SDGs). This paper investigates the impact of COVID 19 on the progress ...of the SDGs and provides insight into how green recovery stimulus, driven by circular economy (CE)-based solid waste management (SWM) could assist in attaining the intended targets of UN-SDG. It was understood in this review that the guiding principles of the UN-SDGs such as, public health, environmental concerns, resource value and economic development are similar to those that have driven the growth of waste management activities; thus, in order to achieve the goals of UN-SDG, a circular economy approach in solid waste management system should be prioritized in the post-COVID economic agenda. However, policy, technology and public involvement issues may hinder the shift to the CE model; therefore, niche growth might come from developing distinctive waste management-driven green jobs, formalizing informal waste pickers and by focusing in education and training of informal worker. The review also emphasized in creating green jobs by investing in recycling infrastructure which would enable us to address the climate change related concerns which is one of the key target of UN- SDG. The CE-based product designs and business models would emphasize multifunctional goods, extending the lifespan of products and their parts, and intelligent manufacturing to help the public and private sectors maximise product utility (thus reducing waste generation) while providing long-term economic and environmental benefits. The study also recommended strong policies that prioritized investments in decentralization of solid waste systems, localization of supply chains, recycling and green recovery, information sharing, and international collaboration in order to achieve the UN-SDGs.
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•The Paper investigated the impact of COVID-19 on the progress of the UN-SDGs.•The guiding principles of UN-SDGs are analogous to that of circular economy (CE) based solid waste management (SWM).•The CE based SWM have potential to create green jobs apart from bringing socio-economic benefits.•To achieve UN-SDGs, CE based SWM should be treated as a priority.•The COVID response fund should also be used to facilitate the transition to full adoption of circular economy model.
Zinc oxide nanorods were grown employing a low cost hydrothermal method on microslide glass substrates pre-coated with ZnO seed layer. The as grown nanorods were annealed in air at 350°C, 450°C and ...550°C. The effect of annealing at different temperatures on morphology, structural, optical and electrical properties was investigated using field emission scanning electron microscopic, X-ray diffraction, UV–vis spectral, photoluminescence and electrical studies. The X-ray diffraction pattern of all the samples showed wurtzite structure preferentially oriented along the c-axis (0 0 2) direction. It was found that diameter of the nanorods increased with increasing of annealing temperature. The UV–vis absorption spectra showed a red shift from which it was inferred that the optical bandgap of the material decreases from 3.33eV to 3.28eV with increase in annealing temperature. Photoluminescence measurements showed increase in the UV emission intensity with respect to annealing temperature and also produced additional peaks attributed to defects and impurities. Annealing the ZnO nanorod structures at various temperatures evidently showed that the sample annealed at 550°C acquired the lowest resistivity about 1.62×10−4Ωcm.
•ZnO nanorods were synthesized by hydrothermal method on microslide glass substrates.•Pre-deposited ZnO seeds were used.•Structural, optical and electrical properties of ZnO nanorods were studied.•Crystalline structure of ZnO nanorods was improved with increase in annealing temperature.•Resistivity decrease was observed with increase in the annealing temperature.
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•ZnO nanorods, Silver-doped ZnO nanoflower and nanoellipsoids were successfully synthesized.•SZO nanoellipsoids had wider optical absorption region than ZnO nanorods.•Silver-doped ZnO ...showed fast gas response and recovery time at 10ppm of ammonia concentration.•Silver-doped ZnO (6%) showed maximum response of 29 for 100ppm at 150°C.
High sensitivity ammonia gas sensor based on Ag/ZnO composite (SZO) nanostructures and their structural, optical, morphological and gas sensing properties were investigated. Field- emission scanning electron microscopy and high- resolution transmission electron microscopy revealed that pure ZnO flower-like nanorods transformed into nanoellipsoids upon adding of silver (Ag). Scanning transmission electron microscopy (STEM) analysis showed clear flower-like morphology of Ag/ZnO composite. STEM-mapping measurement showed that Zn, Ag and O were homogeneously distributed. The ammonia gas sensing analysis revealed that the Ag/ZnO (6wt%) showed higher gas response compared with other content of Ag wt%. Ag/ZnO (6wt%) exhibited the highest response of 29.5 when exposed to 100ppm ammonia gas. Interestingly, Ag/ZnO (6wt%) possessed good response and recovery property of 13 and 20s at low concentration of ammonia at 10ppm, respectively. The mechanism of gas sensing and enhanced gas response of pure ZnO and Ag/ZnO composite was discussed.
We consider transmit beamforming and reflection pattern design in reconfigurable intelligent surface (RIS)-assisted integrated sensing and communication (ISAC) systems to jointly precode ...communication symbols and radar waveforms. We treat two settings of multiple users and targets. In the first, we use a single RIS to enhance the communication performance of the ISAC system and design beams with good cross-correlation properties to match a desired beampattern while guaranteeing a desired signal-to-interference-plus-noise ratio (SINR) for each user. In the second setting, we use two dedicated RISs to aid the ISAC system, wherein the beams are designed to maximize the worst-case target illumination power while guaranteeing a desired SINR for each user. We propose solvers based on alternating optimization as the design problems in both cases are non-convex optimization problems. Through numerical simulations, we demonstrate the advantages of RIS-assisted ISAC systems. In particular, we show that the proposed single-RIS assisted ISAC system improves the minimum user SINR while suffering from a moderate loss in radar target illumination power. On the other hand, the dual-RIS assisted ISAC system improves both minimum user SINR as well as worst-case target illumination power at the targets, especially when the users and targets are not directly visible to the ISAC transmitter.
Acknowledging the ever-increasing demand for composites in the engineering industry, this paper focuses on the failure of composites at the microscale and augmenting the use of multiscale modelling ...techniques to make them better for various applications. This work aims to increase the representativeness of the volume element by attenuating the mesh and size sensitivities in representative volume element (RVE) modelling. A technique to alleviate mesh sensitivity in RVE modelling is proposed, which equalises the fracture energy observed from computational analysis with the real phenomenon, thereby keeping the response independent of the bandwidth of strain localisation. Based on the hypothesis that ensuring periodicity of strain, in addition to displacement periodicity across the domain boundary and supplementing the capability of periodic boundary conditions (PBCs) to attenuate the size dependency in RVE modelling, a set of modified PBCs (MPBCs) are formulated. One thousand two hundred RVE samples falling into combinations of five fibre volume fractions and four RVE sizes are analysed under transverse loading, and the ability of MPBCs to attenuate the effect of RVE size on the precision of material response, particularly in the softening regime, is verified. This work also focuses on various factors affecting damage initiation in 2D composite RVEs. The arrangement of a pair of fibres with their members placed close to each other, such that the angle between the direction of loading and an imaginary line drawn between their centres is less, is observed to make the region between them more favourable to damage.
•A technique to alleviate FE mesh sensitivity in RVE modelling for cracked heterogeneous medium.•Effects of RVE size, fibre volume fraction, and heterogeneity distribution on softening response.•A set of modified periodic boundary conditions to mitigate RVE size sensitivity on microscale damage analysis.•A study of minimum freepath and change in angle between direction of loading and orientation of fibres on RVE response.
We investigate the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom which is strongly coupled to a coplanar transmission line. The ...interaction between the fields and atom produces an effective cross-Kerr coupling. We demonstrate average cross-Kerr phase shifts of up to 20 degrees per photon with both coherent microwave fields at the single-photon level. Our results provide an important step toward quantum applications with propagating microwave photons.
In topological crystalline insulators (TCIs), topology and crystal symmetry intertwine to create surface states with distinct characteristics. The breaking of crystal symmetry in TCIs is predicted to ...impart mass to the massless Dirac fermions. Here, we report high-resolution scanning tunneling microscopy studies of a TCI, Pb 1-x Sn x Se that reveal the coexistence of zero-mass Dirac fermions protected by crystal symmetry with massive Dirac fermions consistent with crystal symmetry breaking. In addition, we show two distinct regimes of the Fermi surface topology separated by a Van-Hove singularity at the Lifshitz transition point. Our work paves the way for engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.
Facile synthesis of carbon coated NiS2 composite through one-step hydrothermal process was demonstrated. Three different composites were synthesized (NCC1, NCC2, and NCC3) by changing the ...stoichiometric ratio of nickel, sulphur and carbon precursor. The particle size and its distribution depend on the amount of carbon precursor and metal sulphides ratio. The carbon coating on metal sulphides significantly augmented the electrochemical properties of the supercapacitor electrodes. It was found that in an optimum ratio of carbon precursor and metal sulphide, the particles were formed uniformly as seen in the NCC2 composites and exhibited the specific capacitance of 2212 F g−1 at a specific current of 2 A g−1 in a three-electrode system. An asymmetric supercapacitor (ASC) device was fabricated with NCC2 as positive electrode and thermally reduced graphene oxide as negative electrode. The ASC device showed high specific capacitance of 184.9 F g−1 at 3 A g−1 and specific energy of 50.35 Wh Kg−1 at a specific power of ~2.26 kW kg−1. It showed ~83% retention in specific capacitance after 6000 charge-discharge cycles. High specific capacitance, specific energy and specific power of the ASC device confirmed that the NCC2 composite could be used as energy storage electrode materials for supercapacitor applications.
The commercial success of hydrothermal carbonization (HTC) is contingent on seeking solutions for the downstream wastewater (process water) generated during the process which is still regarded ...largely as a nuisance. In the present study, the reusability and valorization strategy of process wastewater generated during co-HTC of organic fraction of municipal solid waste (food and yard waste) at 220 °C for 1 h was established. The process wastewater was anaerobically digested in the first part to determine its methane-generating capacity; and in the second part, it was recirculated up to five times to understand the evolution of physicochemical and fuel characteristics of hydrochar. The process water was characterized by the presence of high total organic carbon (up to 40 g/L) and chemical oxygen demand (up to 96 g/L). The decreasing trend of heavy metals with increasing recirculation suggested possible adsorption/immobilization mechanism taking place to the hydrochar surface. The process water generated from co-HTC condition has anaerobic biodegradability of 72% while experimental and theoretical methane yield observed were 224 mL/g COD and 308 mL/g COD, respectively. The presence of high organic and ionic species in recirculated process water promoted the overall carbonization process which was evident from the increased energy yield (86 to 92%), carbon content (68 to 71%) and calorific value (20 to 27 MJ/kg). The recirculation also enhanced overall combustion characteristics of hydrochar as analyzed by thermogravimetric analysis. The recirculation strategy enhanced fuel properties of hydrochar while making sure upstream and downstream water related burden is reduced (as illustrated by life cycle analysis) to create a cleaner production system for renewable solid biofuels production.
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•Process water (PW) from co-HTC of food and yard waste is reused and valorized.•The PW generated from co-HTC condition has high anaerobic biodegradability.•High organic and ionic species in recirculated PW promoted the carbonization process.•Recirculation also enhanced overall combustion characteristics of hydrochar.•Recirculation strategy would reduce upstream and downstream water related burden.
A topological insulator protected by time-reversal symmetry is realized via spin-orbit interaction-driven band inversion. The topological phase in the Bi1-x Sbx system is due to an odd number of band ...inversions. A related spin-orbit system, the Pb1-x Snx Te, has long been known to contain an even number of inversions based on band theory. Here we experimentally investigate the possibility of a mirror symmetry-protected topological crystalline insulator phase in the Pb1-x Snx Te class of materials that has been theoretically predicted to exist in its end compound SnTe. Our experimental results show that at a finite Pb composition above the topological inversion phase transition, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order distinct from that observed in Bi1-x Sbx . Our observation of the spin-polarized Dirac surface states in the inverted Pb1-x Snx Te and their absence in the non-inverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.
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