Stakeholders' willingness to pay for enhanced construction waste management: a Hong Kong study

Based on the polluter pays principle, construction waste disposal charging schemes (CWDCS) have been deployed by various economies as one of the most effective ways of managing construction waste. Nevertheless, a means of rationalizing these schemes has not been well documented. Using the economic technique of contingent valuation method (CVM), this study aims to investigate stakeholders’ willingness to pay (WTP) for enhanced construction waste management (CWM) with a view to providing a scientific foundation for CWDCS rationalization. In considering this WTP in light of repeated exhortations that all stakeholders play a role in the management of construction waste, the study is unique. To ascertain stakeholders’ WTP, a payment card-style questionnaire survey was designed and administered to Hong Kong’s major CWM stakeholders in February 2014. Interestingly, the results show that there is no statistically significant variation in the WTP of different stakeholder groups. The average maximum WTP is around HK232/t for landfill disposal of C&D waste, HK186/t for off-site sorting facility (OSF) disposal, and HK$120/t for public fill reception facility (PFRF) disposal. These values are higher than the existing CWDCS charges (HK$125/t for landfilling, HK$100/t for OSF disposal, and HK$27/t for PFRF disposal) but much lower than the charges proposed to the government. This research provides not only a scientific foundation for the ongoing debate on changes to Hong Kong’s CWDCS, but also a valuable reference for other economies facing the challenge of developing charging schemes to deal with construction waste.postprin

Accelerating Cathode Material Discovery through Ab Initio Random Structure Searching

The choice of cathode material in Li-ion batteries underpins their overall performance. Discovering new cathode materials is a slow process, and all major commercial cathode materials are still based on those identified in the 1990s. Discovery of materials using high-throughput calculations has attracted great research interest; however, reliance on databases of existing materials begs the question of whether these approaches are applicable for finding truly novel materials. In this work, we demonstrate that ab initio random structure searching (AIRSS), a first-principles structure prediction method that does not rely on any pre-existing data, can locate low energy structures of complex cathode materials efficiently based only on chemical composition. We use AIRSS to explore three Fe-containing polyanion compounds as low-cost cathodes. Using known quaternary LiFePO4 and quinary LiFeSO4F cathodes as examples, we easily reproduce the known polymorphs, in addition to predicting other, hitherto unknown, low energy polymorphs and even finding a new polymorph of LiFeSO4F that is more stable than the known ones. We then explore the phase space for Fe-containing fluoroxalates, predicting a range of redox-active phases that are yet to be experimentally synthesized, demonstrating the suitability of AIRSS as a tool for accelerating the discovery of novel cathode materials

Designing durable and flexible superhydrophobic coatings and its application in oil purification

Lotus-inspired superhydrophobic coatings are usually mechanically weak and lack durability, this hinders their practical applications. A suspension that can be treated on various materials in any size and shape to form a mechanically durable superhydrophobic coating is developed, which retains water repellent properties after multiple cycles of abrasion, blade scratching, tape-peeling, repeated deformation, a series of environmental tests and recycling. Based on its superhydrophobicity under oil, two highly efficient systems were developed for oil purification – stirring and inverted cone systems. Small water drops converge on the coated surface that was immersed in oil through velocity-controlled stirring, or designing an inverted cone superhydrophobic surface under oil to collect water drops spontaneously. This coating can be readily used for practical applications to make a durable superhydrophobic coating that functions either in air or oils

Estimating and calibrating the amount of building-related construction and demolition waste in urban China

One side effect of the unprecedented urbanization in China is the large amount of building-related construction and demolition (C&D) waste generated during the process. It is an enigma why such statistics as C&D waste generation are absent from the literature in spite of their importance to devising sensible interventions to deal with the C&D waste related problems. This paper aims to estimate the amount of C&D waste at the country level. It does so by adopting a methodology utilizing national statistical data and the average amounts of waste generated at job sites. Furthermore, the estimation is undergone a thorough calibration against various independent sources before it can be accepted confidently. It is finally estimated that approximately 1.13 billion tons of C&D materials were generated in China during 2014, which has declined from a plateau of building activities and C&D waste generation in the early 2010s. The paper provides some useful references for devising appropriate C&D waste reduction, reuse, or recycling strategies. The paper also offers useful commentary on methodology to estimate C&D waste generation at an urban level, particularly in situations where data availability is erratic.postprin

Ab initio random structure searching for battery cathode materials

Cathodes are critical components of rechargeable batteries. Conventionally, the search for cathode materials relies on experimental trial-and-error and a traversing of existing computational/experimental databases. While these methods have led to the discovery of several commercially viable cathode materials, the chemical space explored so far is limited and many phases will have been overlooked, in particular, those that are metastable. We describe a computational framework for battery cathode exploration based on ab initio random structure searching (AIRSS), an approach that samples local minima on the potential energy surface to identify new crystal structures. We show that by delimiting the search space using a number of constraints, including chemically aware minimum interatomic separations, cell volumes, and space group symmetries, AIRSS can efficiently predict both thermodynamically stable and metastable cathode materials. Specifically, we investigate LiCoO2, LiFePO4, and LixCuyFz to demonstrate the efficiency of the method by rediscovering the known crystal structures of these cathode materials. The effect of parameters, such as minimum separations and symmetries, on the efficiency of the sampling is discussed in detail. The adaptation of the minimum interatomic distances on a species-pair basis, from low-energy optimized structures to efficiently capture the local coordination environment of atoms, is explored. A family of novel cathode materials based on the transition-metal oxalates is proposed. They demonstrate superb energy density, oxygen-redox stability, and lithium diffusion properties. This article serves both as an introduction to the computational framework and as a guide to battery cathode material discovery using AIRSS

Determining interface structures in vertically aligned nanocomposite films

Vertically aligned nanocomposite (VAN) films have self-assembled pillar-matrix nanostructures. Owing to their large area-to-volume ratios, interfaces in VAN films are expected to play key roles in inducing functional properties, but our understanding is hindered by limited knowledge about their structures. Motivated by the lack of definitive explanation for the experimentally found enhanced ionic conductivity in Sm-doped-CeO2/SrTiO3 VAN films, we determine the structure at vertical interfaces using random structure searching and explore how it can affect ionic conduction. Interatomic potentials are used to perform the initial searching, followed by first-principles calculations for refinement. Previously unknown structures are found, with lower energy than that of an optimized hand-built model. We find a strongly distorted oxygen sublattice which gives a complex landscape of vacancy energies. The cation lattice remains similar to the bulk phase, but has a localized strain field. The excess energy of the interface is similar to that of high angle grain boundaries in SrTiO3.China Scholarship Council Cambridge Commonwealth, European and International Trus

Low-Cost One-Step Fabrication of Highly Conductive ZnO:Cl Transparent Thin Films with Tunable Photocatalytic Properties via Aerosol-Assisted Chemical Vapor Deposition

Low-cost, high-efficiency, and high quality Cl-doped ZnO (ZnO:Cl) thin films that can simultaneously function as transparent conducting oxides (TCOs) and photocatalysts are described. The films have been fabricated by a facile and inexpensive solution-source aerosol-assisted chemical vapor deposition technique using NH4Cl as an effective, cheap, and abundant source of Cl. Successful ClO substitutional doping in the ZnO films was evident from powder X-ray diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry results, while scanning electron microscopy reveals the impact of Cl doping on the ZnO thin film morphology. All ZnO:Cl films deposited were transparent and uncolored; optical transmittance in the visible region (400−700 nm) exceeded 80% for depositions using 5−20 mol % Cl. Optimal electrical properties were achieved when using 5 mol % Cl with a minimum measured resistivity of (2.72 ± 0.04) × 10−3 Ω·cm, in which the charge carrier concentration and mobility were measured at (8.58 ± 0.16) × 1019 cm−3 and 26.7 ± 0.1 cm2 V−1 s −1 respectively, corresponding to a sheet resistance (Rsh) of 41.9 Ω□−1 at a thickness of 650 nm. In addition to transparent conducting properties, photocatalytic behavior of stearic acid degradation in the ZnO:Cl films was also observed with an optimal Cl concentration of 7 mol % Cl, with the highest formal quantum efficiency (ξ) measured at (1.63 ± 0.03) × 10−4 molecule/photon, while retaining a visible transparency of 80% and resistivity ρ = (9.23 ± 0.13) × 10−3 Ω·cm. The dual functionality of ZnO:Cl as both a transparent conductor and an efficient photocatalyst is a unique combination of properties making this a particularly unusual material

The phylogenetically-related pattern recognition receptors EFR and XA21 recruit similar immune signaling components in monocots and dicots

During plant immunity, surface-localized pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs). The transfer of PRRs between plant species is a promising strategy for engineering broad-spectrum disease resistance. Thus, there is a great interest in understanding the mechanisms of PRR-mediated resistance across different plant species. Two well-characterized plant PRRs are the leucine-rich repeat receptor kinases (LRR-RKs) EFR and XA21 from Arabidopsis thaliana (Arabidopsis) and rice, respectively. Interestingly, despite being evolutionary distant, EFR and XA21 are phylogenetically closely related and are both members of the sub-family XII of LRR-RKs that contains numerous potential PRRs. Here, we compared the ability of these related PRRs to engage immune signaling across the monocots-dicots taxonomic divide. Using chimera between Arabidopsis EFR and rice XA21, we show that the kinase domain of the rice XA21 is functional in triggering elf18-induced signaling and quantitative immunity to the bacteria Pseudomonas syringae pv. tomato (Pto) DC3000 and Agrobacterium tumefaciens in Arabidopsis. Furthermore, the EFR:XA21 chimera associates dynamically in a ligand-dependent manner with known components of the EFR complex. Conversely, EFR associates with Arabidopsis orthologues of rice XA21-interacting proteins, which appear to be involved in EFR-mediated signaling and immunity in Arabidopsis. Our work indicates the overall functional conservation of immune components acting downstream of distinct LRR-RK-type PRRs between monocots and dicots

Superoleophobic surfaces on stainless steel substrates obtained by chemical bath deposition

Superhydrophobic surfaces have shown great potential in domestic and industrial applications. However, these surfaces lose their superhydrophobic functions once being contaminated by oily liquids. In this work a simple chemical bath deposition method is reported to fabricate superoleophobic surfaces on steel substrates that repel both water and oil. The synthesis of superoleophobic surfaces involves the fabrication of the micro/nanometre-scale origami-ball-like structures on steel substrates, followed by the modification of low surface energy material. The fabricated surfaces have glycerol, peanut oil and hexadecane contact angles larger than 150° and roll-off angles smaller than 10°. This method is highly efficient because it takes only 5 min to create the surface re-entrant structures that are required by superoleophobicity. The prepared surfaces showed remarkable durability and retained superoleophobicity even after exposure to high and low temperatures (−30 and 100°C), and UV irradiation. This work will enrich the processing methods of the superoleophobic surfaces on stainless steel substrates

Creating robust superamphiphobic coatings for both hard and soft materials

Most superhydrophobic surfaces lose their water-repellency when either contaminated by oily liquids or by being mechanically damaged. Superamphiphobic surfaces are ones that repel both oil and water. However, to date such surfaces are hampered by being mechanically weak. Robust superamphiphobic surfaces with highly water and oil repellent properties are desired for a wide range of environments. Reported herein is a superamphiphobic coatings fabricated by a facile deposition method and followed by a low surface energy materials modification. These coatings can be applied on both hard and soft materials to repel water, glycerol, peanut-oil droplets and some organic solvents. Falling sand abrasion, UV irradiation and aqueous media immersion were used to test the mechanical robustness and durability of the superamphiphobic coatings. A multi-cycle stretch/release test was developed to characterize the robustness of the self-cleaning soft materials. A coated rubber-bond retained both water and oil repellency even after 50 stretch/release cycles. These tests show that the superamphiphobic coatings have remarkable mechanical robustness and UV/aqueous media resistance and can be readily applied to a wide variety of materials to form self-cleaning surfaces that are extremely robust and durable even under intense strains