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The aim of this review paper is to critically analyze the existing studies on waste electric and electronic equipment (WEEE), which is one of the most increasing solid waste streams. This complex solid waste stream has pushed many scientific communities to develop novel technologies with minimum ecological disturbance. Noteworthy amount of valuable metals makes e-waste to a core of "urban mining"; therefore, it warrants special attention. Present study is focused on all the basic conceptual knowledge of WEEE ranging from compositional analysis, global statistics of e-waste generation, and metallurgical processes applied for metals extraction from e-waste. This review critically analyses the existing studies to emphasize on the heterogeneity nature of e-waste, which has not been focused much in any of the existing review articles. Comprehensive analysis of conventional approaches such as pyrometallurgy and hydrometallurgy reveals that high costs and secondary pollution possibilities limit the industrial feasibilities of these processes. Therefore biohydrometallurgy, a green technology, has been attracting researchers to focus on this novel technique to implement it for metal extraction from WEEE.

This paper presents an integrated microcavity optical fiber pressure sensor using exfoliated ultrathin graphene atomic layers as a reflective surface to form a Fabry–Perot (F-P) interferometric structure. The fabrication was based on the focused-ion-beam (FIB) micromachining and dry exfoliated graphene transfer method, where the sensor was fabricated directly on a facet of a standard SMF-28 single-mode fiber with the core diameter of $8~\mu \mathrm {m}$ and the cladding diameter of $125~\mu \text{m}$ . The air leakage from the cavity was negligibly small during the 30-min measurement time. The responsivity of pressure sensors, defined as the spectral shift of F-P fringes in response to the air pressure change, was achieved as large as 1.28 nm/mmHg at 1300-nm wavelength when using a diaphragm diameter of $20~\mu \text{m}$ . Demonstrated responsivity and compactness makes the sensor suitable for medical, environmental, and other applications. An analytical model was presented describing responsivity of an F-P pressure sensor with a thin diaphragm. It has predicted that reducing the diaphragm thickness below some critical value leads to the highest possible responsivity that no longer depends on the elastic properties or thickness of the diaphragm. This upper limit for the responsivity can be increased using the cavity shape other than a simple cylinder, while residual strength of the diaphragm results in reduced responsivity.

In the present study, the momentum and heat transfer aspects from an isothermally rotating cylinder immersed in a power-law fluid, confined symmetrically and asymmetrically between two parallel walls are considered. The governing equations are solved numerically for the rotational Reynolds number ( 10 − 3 ≤ R e ≤ 40 ) , Prandtl number ( 1 ≤ P r ≤ 100 ) , power-law index ( 0.02 ≤ n ≤ 1 ) , blockage ratio ( 10 − 3 ≤ β ≤ 0.9999 ) and asymmetry ratio ( 10 − 4 ≤ γ ≤ 1 ) to elucidate the role of these parameters on the momentum and heat transfer characteristics. The results reported herein pertain to the two dimensional, steady, incompressible power-law fluid in the laminar flow region. The numerical strategy and method used here are validated by comparing the present results with some of the available experimental and numerical studies, showing good agreements. As far as can be ascertained, it is the first systematic numerical study of a rotating cylinder immersed in power-law fluids elucidating the complex interplay between the rheological and kinematic parameters. The flow field is visualized by plotting the streamlines and, hydrodynamic forces and torque acting on the rotating cylinder are computed. The numerical results are supplemented by a lubrication approximation analysis relevant to highly confined cases, i.e., large values of β. In this case, when confinement increases, the asymptotic scaling of the torque is given by e − 1 / 2 where e denotes the non-dimensional gap between the cylinder surface and the nearest wall. The heat transfer characteristics are presented in terms of the isotherm contours, and the local and average Nusselt numbers as functions of the aforementioned governing parameters. The rate of heat transfer exhibits a positive dependence on the Reynolds number, Prandtl number, confinement and the degree of asymmetry while the shear-thinning behavior decreases the rate of heat transfer above the corresponding value in Newtonian fluids. Finally, the present results are consolidated by fitting them in the form of a predictive correlation for the average Nusselt number for different blockage ratios studied herein.

In this study, a rotating cylinder is placed in a stream of shear-thinning fluids, flowing with a uniform velocity. Detailed investigations are performed for the following range of conditions: Reynolds number 100≤Re≤500, power-law index 0.2≤n≤1 and rotational velocity 0≤α≤5. Flow transitions are observed from steady to unsteady at critical values of the Reynolds number, the rotational velocity, and the power-law index. Critical values of the Reynolds number Rec have been obtained for varying levels of the rotational velocity, and the power-law index. Rec varies nonmonotonically with the rotational velocity. At a particular Reynolds number, an increase of the rotational velocity acts as a vortex suppression technique. For shear-thinning fluids considered here, the vortex suppression occurs at a larger value of the critical rotational velocity αc, relative to Newtonian fluids. For the unsteady flow, the lift coefficient versus time curve exhibits oscillatory behavior, and this has been used to delineate the flow regime as steady or unsteady flow. For unsteady flow regimes, both the amplitude of the lift coefficient and the Strouhal number increase with increasing Reynolds numbers. The results presented in this work for such high Reynolds numbers elucidate the possible complex interplay between the kinematic and rheological parameters of non-Newtonian fluids. This investigation also complements the currently available low Reynolds number results up to ∼ Re=140.

Nanomaterials with a broadband photon absorption capability are essential for better performing solar cells. Plasmonic nanostructures and Quantum Dots, often fabricated via complex time intensive methods, have a narrow absorption spectrum. In this paper, we report a plasmon hybridised self-assembled 3D nano network of multiphase titanium oxide, which was synthesised via a single step bottoms-up method, and is structurally both multi-layered and three dimensional in nature. The surface plasmonic effect was induced on the self-assembled nanomaterial through its hybridisation with Au and Au/palladium alloy that resulted in the achievement of an enhanced and broadened absorption spectrum extending over the entire visible as well as the near infrared region of the solar spectrum. Further studies were also carried out to examine the impact of various factors like the size, composition and degree of hybridisation of the self-assembled 3D multiphase nano titanium oxide network on its photon absorption capability.

The information theoretic concepts are crucial to study the quantum mechanical systems. In this paper, the information densities of [Formula: see text]-symmetric potential have been demonstrated and their properties deeply analyzed. The position space and momentum space information entropy is obtained and Bialynicki-Birula–Mycielski inequality is saturated for different parameters of the potential. Some interesting features of information entropy have been discussed. The variation in these entropies is described which gets saturated for specific values of the parameter. These have also been analyzed for the [Formula: see text]-symmetry breaking case. Further, the entropy squeezing phenomenon has been investigated in position space as well as momentum space. Interestingly, [Formula: see text] phase transition conjectures the entropy squeezing in position space and momentum space.

We compute the configurational complexity (CC) for discrete soliton and rogue waves traveling along an Ablowitz-Ladik-Hirota (ALH) waveguide and modeled by a discrete nonlinear Schrodinger equation. We show that for a specific range of the soliton transverse direction κ propagating along the parametric time ζ ( t ) , CC reaches an evolving series of global minima. These minima represent maximum compressibility of information in the momentum modes along the Ablowitz-Ladik-Hirota waveguide. Computing the CC for rogue waves as a function of background amplitude modulation μ, we show that it displays two essential features: a maximum representing the optimal value for the rogue wave inception (the “gradient catastrophe”) and saturation representing the rogue wave dispersion into constituent wave modes. We show that saturation is achieved earlier for higher values of modulation amplitude as the discrete rogue wave evolves along time ζ ( t ) .

In this work, two-dimensional, steady flow of incompressible Bingham plastic fluids past a rotating circular cylinder has been studied. The continuity and momentum equations have been solved numerically over the range of conditions as follows: 0.1 ≤ Re ≤ 40; Bingham number, 0 ≤ Bn ≤ 103 and non-dimensional rotational velocity 0 ≤ α ≤ 5. The objective of the detailed numerical study is to elucidate the effects of Reynolds number, Bingham number and rotational velocity on the yield surfaces, the drag and lift coefficients, and torque acting on the rotating cylinder. The present drag results have been correlated with the modified Reynolds number and rotational velocity to interpolate the intermediate values of Bingham number. In additional, shear rate and yielded/unyielded contours, and streamlines in the vicinity of the cylinder are also presented for detailed visualization of the flow field. The critical Bingham number, denoting the cessation of the flow detachment from the surface of the rotating cylinder, has been plotted as a function of the Reynolds number, and the rotational velocity is shown to suppress the propensity for flow separation.

Nanomaterials based on titanium di-oxide (titania) are intensively being studied for their incorporation in the next generation photovoltaic devices due to titania׳s excellent photocatalytic properties. Inefficient utilisation of deeper visible and near infra-red region (NIR) photons has however limited the exploitation of such materials. In this paper, we report a unique titanium oxide nanomaterial that is sensitive to photons of wavelength even longer than 600 nm and is composed of not one but multiple phases of titanium oxide. It has exhibited enhanced absorption that is three times greater in visible region and six times greater in NIR than base titanium. Synthesised by a phenomenon created via the interaction of ultrashort pulses with a titanium substrate, this photoabsorptive nanomaterial is dopant free and is structurally formed as a dense three dimensional network. Further effective tuning of the optical properties of the synthesised multiphase titanium oxide nanomaterial can make it a potential absorber material in photovoltaic devices.

Prior research has demonstrated the importance of government policy in fostering innovation in sectors that face market failures, such as renewable energy. We examine the impact of policy on renewable energy innovations in emerging economies, which face market as well as institutional failures. We investigate how differences in the focus of policies may drive technology development efforts in different directions. Specifically, we propose that demand pull policies foster innovations in mature technologies by encouraging exploitation of readily available technologies, while supply push policies foster innovations in novel technologies by encouraging exploration and alleviating resource constraints in research and development. Using information on policy initiatives and renewable energy patents, we develop comparative case studies of four emerging economies over the years 2000–2015 in the renewable energy sector – Turkey, India, Brazil, and China. Our case findings illustrate that countries with a focus on pull policies innovate primarily in mature technologies, whereas ones with a focus on push policies have substantial innovations in novel technologies. We present a typology of policy and innovation focus, informed by our conceptual framework and case studies.