A high-performance power generator has been successfully fabricated based on a superhydrophilic three-dimensional assembly of graphene oxide. The open framework of this specially designed graphene ...oxide assembly largely facilitated the diffusion of water molecules to produce the dissociated charged ions as free carriers. Meanwhile, its asymmetrical oxygen-containing groups enabled an ionic gradient to accelerate the directed transport of the ionic charge carriers. A high power density of ca.1 mW cm super(-2) and an energy-conversion efficiency of ca.52% were achieved and its potential as a practical power source was evidenced by a simple pendulum-based chemical potential energy harvesting system.
Rapid environmental degradation is a well-publicized issue, particularly in rapidly developing countries. This study examines the impact of air pollution and green coverage on people's subjective ...well-being (SWB) in China using self-reported life satisfaction (LS) from survey data combined with the city-level air quality index (AQI) and green coverage data. The results show that air pollution and green coverage are significantly negatively and positively correlated with LS, respectively. The total effect of green coverage on life satisfaction constitute of a direct effect of green space itself and indirect effects through improving air pollution and health. The implicit monetary valuations of a 1-unit reduction in the AQI and a 1% increase in green coverage according to the respondent's annual gross individual income are approximately 239–280 USD (1.7%–2.0%) and 420–444 USD (3.0%–3.2%), respectively. The results also indicate that the average benefit from a 1% change in green coverage for people with a poor subjective health evaluation is almost 2 times higher than that for their counterparts.
The particle-to-particle heterogeneity in aerosol hygroscopicity is crucial for understanding aerosol climatic and environmental effects. The hygroscopic parameter κ, widely applied to describe the ...hygroscopicity for aerosols both in models and observations, is a probability distribution highly related to aerosol heterogeneity due to the complex sources and aging processes. However, the heterogeneity in aerosol hygroscopicity is not adequately represented in observations and model simulations, leading to challenges in accurately estimating aerosol climatic and environmental effects. Here, we propose an algorithm for quantifying the particle-to-particle heterogeneity in aerosol hygroscopicity, based on information-theoretic entropy measures, by using the data that come only from the in situ measurement of the hygroscopicity tandem differential mobility analyzer (H-TDMA). Aerosols in this algorithm are assumed to be simple binary systems consisting of the less hygroscopic and more hygroscopic components, which are commonly used in H-TDMA measurement. Three indices, including the average per-particle species diversity Dα, the bulk population species diversity Dγ, and their affine ratio χ are calculated from the probability distribution of κ to describe aerosol heterogeneity. This algorithm can efficiently characterize the evolution of aerosol heterogeneity with time in the real atmosphere. Our results show that the heterogeneity varies much with aerosol particle size, and large discrepancies exist in the width and peak value of particle number size distribution (PNSD) with varied heterogeneity after hygroscopic growth, especially for conditions with high relative humidity. This reveals a vital role of the heterogeneity in ambient PNSD and significant uncertainties in calculating the climate-relevant properties if the population-averaged hygroscopicity is applied by neglecting its heterogeneity. This work points the way toward a better understanding of the role of hygroscopicity in evaluating aerosol climatic and environmental impacts.
This paper provides further elaborations on discrete variable topology optimization via sequential integer programming and Canonical relaxation algorithm. Firstly, discrete variable topology ...optimization problem for minimum compliance subject to a material volume constraint is formulated and approximated by a sequence of discrete variable sub-programming with the discrete variable sensitivity. The differences between continuous variable sensitivity and discrete variable sensitivity are discussed. Secondly, the Canonical relaxation algorithm designed to solve this sub-programming is presented with a discussion on the move limit strategy. Based on the discussion above, a compact 128-line MATLAB code to implement the new method is included in Appendix
1
. As shown by numerical experiments, the 128-line code can maintain black-white solutions during the optimization process. The code can be treated as the foundation for other problems with multiple constraints.
The main objective of this paper is to use a novel finite-time control method to solve the global finite-time convergence problem of image-based visual servoing of a quadrotor Unmanned Aerial Vehicle ...(QUAV). The effects of external wind resistance and system uncertainty are considered in the QUAV dynamics, and a disturbance observer is used to compensate for these effects. For the problem of obtaining target feature depth information, a novel nonlinear finite-time linear velocity observer is proposed by using the backstepping method. Based on the above two observers, we use the backstepping method to design the global finite-time controller of the system. The system is proved global finite-time stable using the Lyapunov method. Finally, numerical simulation and ROS gazebo simulation results demonstrate the effectiveness of the proposed control scheme.
A new nanocomposite consisting of ZnO nanowire turf‐coated Bi2O3 plates was synthesized using a method combining a chemical bath and hydrothermal crystal growth through sputtering ZnO seed ...layer‐assisted growth. Structural analysis revealed that highly crystalline, high‐density, one‐dimensional (1D) ZnO crystals were uniformly coated on the organized two‐dimensional (2D) Bi2O3 plates with a single β phase or dual α/β polymorphic phases. The Bi2O3–ZnO composites exhibited enhanced absorption properties in the ultraviolet and visible regions compared with pristine Bi2O3 and ZnO. Furthermore, the Bi2O3–ZnO composites exhibited higher photoactive performance than that of the pristine Bi2O3 and ZnO because of the low recombination rate of photoinduced electron−hole pairs caused by the vectorial transfer of electrons and holes between ZnO and Bi2O3 and the substantially increased surface area of the unique composite morphology. The ZnO nanowire turf‐coated Bi2O3 plates with a α/β‐Bi2O3 matrix exhibited photoelectrochemical and photocatalytic properties superior to those of the composite with a single β‐Bi2O3 matrix. The coexistence of α/β homojunction in the Bi2O3 matrix and the abundant heterojunctions between the ZnO nanowires and Bi2O3 plates substantially enhanced photoexcited charge separation efficiency. Growing high‐density 1D ZnO on 2D Bi2O3 via a combination methodology and crystallographic phase control provided a promising material design route for nanocomposite systems with high photoactivity for photoexcited device applications.
Tuning the crystal structure of Bi2O3 crystals from a single β-phase, dual β/γ-phase, and γ-phase can be realized through time-dependent phase evolution through a one-pot hydrothermal method. The ...β/γ-Bi2O3 heterophase hybrids were formed by adequately controlling the crystal growth conditions. The morphology of the dual-phased Bi2O3 hybrids presents γ-Bi2O3 micro tetrahedra scattered on massive two-dimensional β-Bi2O3 triangular nanosheets. In comparison with single β-phase or γ-phase Bi2O3 crystals, the β/γ-Bi2O3 heterophase hybrids enhance the visible-light absorption capacity, promote the separation of photoinduced carriers, and display minor interfacial resistance. A possible Z-scheme mechanism facilitates photoinduced carrier separation efficiently through the built-in field at the interface. It yields adequate reactive species to stimulate photocatalytic capability towards Rhodamine B degradation. The result herein sheds light on the characteristics of dual-phase Bi2O3 crystals and provides an innovative option for the design of self-evolving and highly efficient heterophase photocatalysts.
•COVID-19 reduces the implicit price of metro accessibility.•The price elasticity of distance to the metro is −0.024 before COVID-19 but turns to −0.018 during the pandemic.•COVID-19 does not harm ...property prices in Chengdu.•This study points out an innovative and interesting research direction.
The metro (or underground railways) has become a backbone in the transit systems of many cities. It has numerous externalities, such as ameliorating traffic congestion and enhancing nearby property prices. Previous studies extensively focused on the relationship between metro accessibility and property prices and obtained various interesting findings and enriched practical implications. However, this relationship in the era of the coronavirus disease 2019 (COVID-19) and other epidemic shocks has not been investigated. Based on a unique property transaction dataset (including tens of thousands of transactions stretching from 2018 to 2020) in Chengdu, China, this study develops a battery of hedonic pricing models and difference-in-differences models to decipher the time-varying relationship between metro accessibility and residential property prices. The results show that the implicit price of metro accessibility modestly decreases in COVID-19, which can be explained by the declining role of the metro. In other words, the price gap between proximate and distant properties is narrowed, and the property price gradient is flattened. Specifically, the price elasticity of distance to the metro is − 0.024 before COVID-19, but it turns to − 0.018 during the pandemic. The relative price of properties within 500 m from metro stations to those farther away (500 m − 3 km) decreases by 15.4% during the pandemic. Additionally, COVID-19 does not jeopardize property prices in Chengdu. Furthermore, the decrease in metro access premiums may be short-lived and only persisted for several months or years. The plausibility and robustness of the core findings have been confirmed through alternative treatment groups, alternative model specifications, and placebo tests.
In contrast with the well-developed C-C and C-N axial chirality, research focusing on the catalytically asymmetric synthesis of N-N axially chiral compounds is still limited. As a privileged subunit ...of many antibiotics, the synthesis of N-N axially chiral 3,3′-bisquinazolinones has not been updated with atroposelective construction. Herein, we firstly report a chiral phosphoric acid-catalyzed dual-ring formation strategy leading to the aforementioned compounds with good chemical yields and enantioselectivities. Notably, metal-free reaction conditions are another advantage of this procedure.
An efficient, CPA-catalyzed, dual-ring formation strategy to construct a class of N-N axially chiral 3,3′-bisquinazolinones is reported for the first time. Notably, metal-free reaction conditions were also involved in this procedure.
The Ag2S crystallites–decorated ZnS composite sheets were synthesized by combinational methodology. Two types of ZnS sheet templates were obtained through the vulcanization of ZnO sheets with sulfur ...precursors of thiourea and Na2S, and then ZnS–Ag2S heterogeneous sheets were obtained with sputtering Ag crystallites and post‐annealing procedures. The ZnS sheets have rugged and smooth surfaces formed with sulfur precursors of thiourea and Na2S, respectively. Both the initial microstructures of ZnS sheet templates and Ag2S decoration content affect the photoactivity of the ZnS–Ag2S composite sheets. Compared with the pristine ZnS, the ZnS–Ag2S composite sheets with a suitable Ag2S loading content (Ag at% = 3.6–3.8) are beneficial to improve the photoactivity, which could be explained by the combination of narrow bandgap; Ag2S crystallites would enhance photon absorption and separation efficiency of photoinduced charge carriers. The scavenger tests and photodegradation mechanism show that hydroxyl radicals and holes were the main active species for the ZnS–Ag2S composite sheets to photodegrade methyl orange solution. The experimental results herein provide a novel synthesis approach to decorate Ag2S crystallites onto ZnS with tunable contents and present important design guidelines for the resultant ZnS–Ag2S composite sheets to demonstrate marked improvement in photoactivity.
