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Sustainability assessment of a single-use plastics ban
No full textGovernments around the world are introducing single-use plastics bans to alleviate plastic marine pollution. This paper investigates whether banning single-use plastic items is an appropriate strategy to protect the environment. Product life cycle assessment was conducted for single-use plastic and single-use non-plastic alternatives. The life cycle impacts of the two product categories were compared and scaled according to EU consumption of 2016. The results show that a single-use plastics ban would decrease plastic marine pollution in the EU by 5.5% which equates to a 0.06% decrease globally. However, such a ban would increase emissions contributing to marine aquatic toxicity in the EU by 1.4%. This paper concludes that single-use items are harmful to the environment regardless of their material. Therefore, banning or imposing a premium price on single-use items in general and not only single-use plastic items is a more effective method of reducing consumption and thereby pollution. The plastics ban only leads to a small reduction of global plastic marine pollution and thus provides only a partial solution to the problem it intends to solve
Zero-net energy management for the monitoring and control of dynamically-partitioned smart water systems
No full text© 2019 Elsevier Ltd The optimal and sustainable management of water distribution systems still represent an arduous task. In many instances, especially in aging water net-works, pressure management is imperative for reducing breakages and leakages. Therefore, optimal District Metered Areas represent an effective solution to decreasing the overall energy input without performance compromise. Within this context, this paper proposes a novel adaptive management framework for water distribution systems by reconfiguring the original network layout into (dynamic) district metered areas. It utilises a multiscale clustering algorithm to schedule district aggregation/desegregation, whilst delivering energy and supply management goals. The resulting framework was tested in a water utility network for the simultaneously production of energy during the day (by means of the installation of micro-hydropower systems) and for the reduction of water leakage during the night. From computational viewpoint, this was found to significantly reduce the time and complexity during the clustering and the dividing phase. In addition, in this case, a recovered energy potential of 19 MWh per year and leakage reduction of up to 16% was found. The addition of pump-as-turbines was also found to reduce investment and maintenance costs, giving improved reliability to the monitoring stations. The financial analyses to define the optimal period in which to invest also showed the economic feasibility of the proposed solution, which assures, in the analysed case study, a positive annual net income in just five years. This study demonstrates that the combined optimisation, energy recovery and creation of optimized multiple-task district stations lead to an efficient, resilient, sustainable, and low-cost management strategy for water distribution networks
Associations between voxel-level accumulated dose and rectal toxicity in prostate radiotherapy
No full textBackground and Purpose: Associations between dose and rectal toxicity in prostate radiotherapy are generally poorly understood. Evaluating spatial dose distributions to the rectal wall (RW) may lead to improvements in dose-toxicity modelling by incorporating geometric information, masked by dose-volume histograms. Furthermore, predictive power may be strengthened by incorporating the effects of interfraction motion into delivered dose calculations. Here we interrogate 3D dose distributions for patients with and without toxicity to identify rectal subregions at risk (SRR), and compare the discriminatory ability of planned and delivered dose. Material and Methods: Daily delivered dose to the rectum was calculated using image guidance scans, and accumulated at the voxel level using biomechanical finite element modelling. SRRs were statistically determined for rectal bleeding, proctitis, faecal incontinence and stool frequency from a training set (n = 139), and tested on a validation set (n = 47). Results: SRR patterns differed per endpoint. Analysing dose to SRRs improved discriminative ability with respect to the full RW for three of four endpoints. Training set AUC and OR analysis produced stronger toxicity associations from accumulated dose than planned dose. For rectal bleeding in particular, accumulated dose to the SRR (AUC 0.76) improved upon dose-toxicity associations derived from planned dose to the RW (AUC 0.63). However, validation results could not be considered significant. Conclusions: Voxel-level analysis of dose to the RW revealed SRRs associated with rectal toxicity, suggesting non-homogeneous intra-organ radiosensitivity. Incorporating spatial features of accumulated delivered dose improved dose-toxicity associations. This may be an important tool for adaptive radiotherapy in the future
Optimized performance of an all-REBaCuO hybrid trapped field magnet lens (HTFML) with liquid nitrogen cooling
No full textThe hybrid trapped field magnet lens (HTFML), proposed by the authors in 2018, is a promising device that is able to concentrate a magnetic field higher than the applied field continuously, even after removing the external applied field. In this study, we have investigated the optimized performance of the HTFML consisting of a GdBaCuO magnetic lens and a hollow, cylindrical EuBaCuO trapped field magnet (TFM) for various applied fields, Bapp, at 77 K using liquid nitrogen. A maximum concentrated magnetic field of Bc = 1.83 T was obtained experimentally in the central bore of the HTFML for Bapp = 1.80 T. For Bapp higher than 1.80 T, the Bc value decreased, and was lower than the trapped field, Bt, in the single EuBaCuO TFM cylinder from field cooled magnetization. We have individually analyzed the electromagnetic behavior of the HTFML, single TFM hollow cylinder, and single magnetic lens during the magnetizing process using experimental and numerical simulation results. When the Bc value in the HTFML is lower than the Bt value of the single TFM cylinder for an identical Bapp, the magnetic lens in the HTFML becomes partially magnetized, resulting in the generation of a negative magnetic field in the opposite direction. As a result, the concentrated field in the HTFML is reduced after the magnetizing process. The optimum applied field, Bapp, which is the same magnitude as the maximum trapped field ability of the single TFM cylinder, provides the best performance. The maximum Bc value, and the Bapp value that results in this Bc value, are determined by the critical current density, Jc(B), characteristics of the bulk superconducting material used in the magnetic lens and TFM hollow cylinder in the HTFML
Flexible optoelectronic devices based on metal halide perovskites
No full text© 2020, Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature. The unique physical and chemical properties of metal halide perovskites predestine the devices to achieve high performance in optoelectronic field. Among the numerous high qualities of perovskites, their different low-temperature synthesis methods and preparation processes make them impressive and popular materials for flexible optoelectronic devices. Mainstream perovskite devices, for instance, solar cells, photodetectors and light-emitting diodes, have been fabricated on flexible substrates and show outstanding flexibility as well as high performance. For soft wearable electronic systems, mechanical flexibility is the premier condition. Compared to common devices based on rigid substrates, flexible perovskite devices are more practical and see widespread applications in energy, detection, display, and other fields. This review summarizes the recent progress of flexible perovskite solar cells, photodetectors and light-emitting diodes. The design and fabrication of different high-performance flexible perovskite devices are introduced. Various low-dimensional perovskite materials and configurations for flexible perovskite devices are presented. In addition, the limitations and challenges for further application are also briefly discussed. [Figure not available: see fulltext.]
Effect of sodium chloride on the evolution of size, mixing state, and light absorption of soot particles from a smoking laminar diffusion flame
No full textIn this study, the effect of sodium chloride (NaCl) on the evolution of size, mixing state, and optical properties of particle emissions was investigated. A smoking laminar diffusion flame of methane with flame length of ~100 mm was used, with and without NaCl particles introduced into the fuel stream. Extractive probe sampling with high dilution was used to sample particles and characterize their size and mixing state. Particle size distribution results showed that for the methane-only flame, the soot particles underwent typical processes of formation and coagulation in the flame, partial oxidation near the flame tip, and further coagulation in the post-flame region. In the case of the methane–NaCl flame, the coagulation rate between soot particles decreased in the agglomeration region of the flame, resulting in smaller soot particles with higher number concentration. Near the open tip of the flame, the NaCl inhibited soot oxidation, leading to larger particles compared to the methane-only flame due to continued coagulation and reduced oxidation of soot particles. In the post-flame region, where the temperature was sufficiently low, NaCl particles nucleated from its vapour phase, which was a distinct mode from that of soot in the particle size distributions. Electron microscopy images showed that these nucleated NaCl particles were mostly externally mixed and occasionally internally mixed with soot particles. Thermal-optical analysis of emissions sampled from post-flame region showed that the mass concentration of elemental carbon increased by a factor of ~3 when NaCl was added to the flame. However, addition of NaCl did not affect the mass-specific absorption coefficient of particle emissions, which was within previously reported values in the literature
Soot particle size distribution measurements in a turbulent ethylene swirl flame
No full textThere is a need to better understand particle size distributions (PSDs) from turbulent flames from a theoretical, practical and even regulatory perspective. Experiments were conducted on a sooting turbulent non-premixed swirled ethylene flame with secondary (dilution) air injection to investigate exhaust and in-burner PSDs measured with a Scanning Mobility Particle Sizer (SMPS) and soot volume fractions (fv) using extinction measurements. The focus was to understand the effect of systematically changing the amount and location of dilution air injection on the PSDs and fv inside the burner and at the exhaust. The PSDs were also compared with planar Laser Induced Incandescence (LII) calibrated against the average fv. LII provides some supplemental information on the relative soot amounts and spatial distribution among the various flow conditions that helps interpret the results. For the flame with no air dilution, fv drops gradually along the centreline of the burner towards the exhaust and the PSD shows a shift from larger particles to smaller. However, with dilution air fv reduces sharply where the dilution jets meet the burner axis. Downstream of the dilution jets fv reduces gradually and the PSDs remain unchanged until the exhaust. At the exhaust, the flame with no air dilution shows significantly more particles with an fv one to two orders of magnitude greater compared to the Cases with dilution. This dataset provides insights into soot spatial and particle size distributions within turbulent flames of relevance to gas turbine combustion with differing dilution parameters and the effect dilution has on the particle size. Additionally, this work measures fv using both ex situ and in situ techniques, and highlights the difficulties associated with comparing results across the two. The results are useful for validating advanced models for turbulent combustion
DNS of inhomogeneous turbulence under rotation
No full textRotating turbulent flow is routinely encountered in geophysical environment, such as in cyclones and tornadoes. The number of investigations on inhomogeneous rotating turbulence is relatively sparse as compared to its homogeneous counterpart although they are more common in nature. The present study involves Direct Numerical Simulation (DNS) of a 'cloud' of turbulence with quiescent fluid on either side, under background rotation. The motivation behind the study is to understand the role of inertial waves in inhomogeneous rotating turbulence. In the results obtained, helicity - a quantity representative of the degree of entanglement of the vortices, is found to propagate in a way typical of inertial waves. The thickness of the growing cloud is found to scale linearly with time