Search

Water covers most of the Earth’s surface and is nowhere near a good ecological or recreational state in many areas of the world. Moreover, only a small fraction of the water is potable. As climate change-induced extreme weather events become ever more prevalent, more and more issues arise, such as worsening water quality problems. Therefore, protecting invaluable and useable drinking water is critical. Environmental agencies must continuously check water sources to determine whether they are in a good or healthy state regarding pollutant levels and ecological status. The currently available tools are better suited for stationary laboratory use, and domain specialists lack suitable tools for on-site visualisation and interactive exploration of environmental data. Meanwhile, data collection for laboratory analysis requires substantial time and significant effort. We, therefore, developed an augmented reality system with a Microsoft HoloLens 2 device to explore the visualisation of water quality and status in situ. The developed prototype visualises geo-referenced sensor measurements incorporated into the perspective of the surroundings. Any users interested in water bodies’ conditions can quickly examine and retrieve an overview of water body status using augmented reality and then take necessary steps to address the current situation.

Green development is an inevitable choice for sustainable development under the constraints of environmental resources. This paper attempts to explore the connotation of urban land green utilization efficiency (LGUE) and reveal its spatial differentiation characteristics. This study adopts the super-SBM model to measure LGUE from 2009 to 2022 and analyzes the spatiotemporal variation rules. Then, the study reveals the spatial influencing factors of LGUE, drawing the following conclusions: (1) the average efficiency value of LGUE at the national level is still at a low level, but it is on an upward trend. There are significant differences in LGUE among the eastern, central, and western regions, with the highest LGUE in the eastern region and the lowest in the western region. (2) The spatial distribution of LGUE in various cities across the country is not entirely random but shows significant spatial autocorrelation characteristics. The improvement in LGUE in a region can improve the surrounding region’s LGUE. (3) Economic development level promotes the improvement of local city LGUE, but its impact on LGUE of surrounding neighboring cities is not significant; local city industrial structure upgrading can improve LGUE in both local and neighboring cities; foreign investment in local cities can promote LGUE in both local and neighboring cities; the increase in population density will hinder LGUE in local cities but improve surrounding cities LGUE. The intervention degree of local city government will suppress the improvement of LGUE in both local and neighboring cities.

The Doppler scatterometer is an instrument used in real aperture radar in conjunction with a circular scanning antenna and has wide swath and multiangle characteristics. Many scholars have studied sea surface current vector field based on the use of the Doppler scatterometer. However, the existing methods directly use the phase difference of the spectrometer's echo to obtain the current vector field, and the resolution can be improved. This study proposes a high-resolution inversion method for ocean surface current fields based on circular scanning synthetic aperture radar (SAR). The current field is estimated by the proposed method based on the Doppler spectrum of the single complex image to realize high-resolution current vector field inversion. The current field inversion of circular scanning SAR is very sensitive to attitude and wind field errors. Accordingly, a model is established to study the influences of the main errors on Doppler shift estimation, and a global optimization method is proposed to realize high-precision current velocity inversion and synchronous error estimation. The effectiveness of this method is verified by using airborne circular scanning SAR data.

Abstract The target scattering characteristics in microwave band are necessary to be researched for Orbital‐Angular‐Momentum (OAM) wave‐based radar applications. A theoretical description of electromagnetic (EM) scattering from a typical target by OAM waves is proposed in this paper. First, OAM waves are decomposed into plane waves in the spectral domain with different elevation and azimuth angles. Then, the scattering form of each decomposed plane wave is determined through coordinate system transformation and physical optics approximation. Formulas and numerical results are presented for OAM‐based radar scattering cross section of a perfect electric conductor and dielectric plate and a cylinder. Unlike the conventional results of EM plane wave scattering, the scattering properties of OAM waves from plate and cylinder are analysed with particular emphasis on OAM mode influence. The results provide insights into OAM wave‐matter interactions and may find important applications in wave propagation and OAM wave‐based radar detection and imaging.

Semiconducting polymers (SPs) have shown great feasibility as candidates for near-infrared-II (NIR-II) fluorescence imaging-navigated photothermal therapy due to their strong light-harvesting ability and flexible tunability. However, the fluorescence signal of traditional SPs tends to quench in their aggregate states owing to the strong π–π stacking, which can lead to the radiative decay pathway shutting down. To address this issue, aggregation-induced emission effect has been used as a rational tactic to boost the aggregate-state fluorescence of NIR-II emitters. In this contribution, we developed a precise molecular engineering tactic based on the block copolymerizations that integrate planar and twisted segments into one conjugated polymer backbone, providing great flexibility in tuning the photophysical properties and photothermal conversion capacity of SPs. Two monomers featured with twisted and planar architectures, respectively, were tactfully incorporated via a ternary copolymerization approach to produce a series of new SPs. The optimal copolymer (SP2) synchronously shows desirable absorption ability and good NIR-II quantum yield on the premise of maintaining typical aggregation-induced emission characteristics, resulting in balanced NIR-II fluorescence brightness and photothermal property. Water-dispersible nanoparticles fabricated from the optimal SP2 show efficient photothermal therapeutic effects both in vitro and in vivo. The in vivo investigation reveals the distinguished NIR-II fluorescence imaging performance of SP2 nanoparticles and their photothermal ablation toward tumor with prominent tumor accumulation ability and excellent biocompatibility.

This paper presents the development of autonomy capability for an unmanned surface vehicle (USV). The development mainly focuses on the high-level autonomy on perception, path planning, guidance and control to achieve real sea applications of the USV. First, visual recognition and point cloud data processing techniques are utilized to achieve a real-time perception of the object in the sea environment. Second, detailed path planning strategies are illustrated to plan the easily reachable path for different missions, and the classic guidance and heading controller are adopted to implement the path following algorithm. Subsequently, these autonomy algorithms run in the high-level computer and render the actuator commands for the low-level embedded control system. Finally, sea trials of the USV are conducted by attending the 2020 Zhuhai Wanshan International Intelligent Vessel Competition (IIVC) in Dong Ao Island of South China Sea. The USV accomplish three missions: 1) path following, 2) navigating around the obstacle, and 3) rescuing the drowning. Sea trial results verify the autonomy of the USV in terms of the achieved performances.

The propagation and scattering of vortex light beams in complex media have significant implications in the fields of laser imaging, optical manipulation, and communication. This paper investigates the scattering characteristics of vortex light beams from a random rough surface. Firstly, a two-dimensional Gaussian rough surface is generated using the Monte Carlo method combined with the linear filtering method. Subsequently, the vortex beams are decomposed into the superposition of infinite plane waves, and the scattering of each plane wave from the rough surface is calculated using the Kirchhoff Approximation method. Numerical results of the angle distribution and spatial distribution of OAM scattering Laser Radar Cross Section (LRCS) are presented, varying with different surface roughness parameters for a rough aluminum surface and the beam’s parameters. The results demonstrate that the scattering of vortex beams is influenced by the beam’s parameters, such as Orbital Angular Momentum (OAM) mode number and elevation angle, which may bring new insights into vortex wave-matter interactions and their applications in high resolution imaging.

This paper offers a holistic review of the role of big data analytics in sharing economy (SE). Academic literature in this field is analyzed to show the theoretical foundation, important papers, and key themes underlying the field by using various bibliometric analysis tools. We conduct a citation and co-citation analysis on literature concerning big data analytics in sharing economy, which published in the 12-year period from 2010–2021. A total of 205 papers were screened from Web of Science (WoS) database for our analysis. In the citation analysis, we depend on the degree centrality and betweenness centrality to identify 48 important papers. In the co-citation analysis, four major research themes are identified: sustainable business model, efficient match-making, trust building and innovation and value cocreation. The research also highlights future research directions and critical areas for the application of big data analytics in the SE context, which may help to produce in-depth studies.

When a radar detects marine targets, the radar echo is influenced by the shape, size and dielectric properties of the targets, as well as the sea surface under different sea conditions and the coupling scattering between them. This paper presents a composite backscattering model of the sea surface and conductive and dielectric ships under different sea conditions. The ship scattering is calculated using the equivalent edge electromagnetic current (EEC) theory. The scattering of the sea surface with wedge-like breaking waves is calculated using the capillary wave phase perturbation method combined with the multi-path scattering method. The coupling scattering between ship and sea surface is obtained using the modified four-path model. The results reveal that the backscattering RCS of the dielectric target is significantly reduced compared with the conducting target. Furthermore, the composite backscattering of the sea surface and ship increases significantly in both HH and VV polarizations when considering the effect of breaking waves under high sea conditions at low grazing angles in the upwind direction, especially for HH polarization. This research offers valuable insights into optimizing radar detection of marine targets in varying sea conditions.

In order to enhance the high-temperature mechanical performance to meet service requirements, the microstructures and tensile properties of heat-treated Al-8.4Cu-2.3Ce-1.0Mn-0.2Zr-xNi (x = 0, 0.5, 1.0, 2.0, 4.0 wt.%) were investigated. The metallographic analysis techniques have been used to examine the microstructural changes with different Ni contents. Results show that after adding 0.5% Ni to the Al-8.4Cu-2.3Ce-1.0Mn-0.2Zr alloy, the spheroidized Al7Cu4Ni phase is formed. With Ni content further increasing, the Al8CeCu4 and Al24MnCu8Ce3 phases disappear, and the nano-sized Al20Cu2Mn3 and Al2Cu phases decrease gradually. When Ni content reaches 4.0%, the Al3CuNi phase appears. It turns out that the addition of 0.5% Ni has significantly improved the tensile properties at 400 °C. The ultimate tensile strength, yield strength, and elongation of Al-8.4Cu-2.3Ce-1.0Mn-0.2Zr-0.5Ni alloy at 400 °C reach 103 MPa, 93 Mpa, and 18.0%, respectively, which makes the alloy possible to be employed at 400 °C. The intermetallic micro-skeleton, composed of thermostable Al8CeCu4, Al24MnCu8Ce3, Al16Cu4Mn2Ce, and Al7Cu4Ni phases at the grain boundaries as well as nano-sized Al20Cu2Mn3 and Al2Cu precipitates in the grains, contributes to the good elevated-temperature tensile strength. The fracture mechanism is changed from quasi-cleavage at ambient temperature to coexistence of quasi-cleavage and dimple at 400 °C.

This paper adopts the super-efficient DEA (data envelopment analysis) model to measure the forestry eco-efficiency (FECO) of 30 Chinese provinces and cities from 2008 to 2021, and then introduces the Tobit model to explore the influencing factors of FECO to better understand the sustainable development level of forestry. It draws the following conclusions: (1) The average value of FECO in China is 0.504, which is still at a low level, and the FECO of each region has significant regional heterogeneity; the provinces with higher FECO are mainly concentrated in the eastern region, while the FECO of the central and western regions is lower; (2) In terms of the main factors affecting FECO in China, the regression coefficients of market-based environmental regulations are significantly positive in the national, eastern and central regions, while they are significantly negative in the western region. The coefficient of impact of scientific research funding investment on forestry industry eco-efficiency is negative and shows a significant promotion effect in the eastern region, but the elasticity coefficient in the central and western regions is negative but not significant. Economic development has a positive but insignificant effect on FECO, with the eastern region showing a positive correlation, while the central and western regions are insignificant. Industrial structure has a significant negative effect on FECO in the national, eastern and central regions, but the effect of industrial structure on FECO in the western region is not significant. The effect of foreign direct investment on FECO was negative for the national, central and western regions, but the central region did not pass the significance test, while the eastern region reflected a significant promotion effect.

To further determine the brittle-to-ductile transition temperature, the microstructures and mechanical properties of typical forged β-solidifying Ti-42Al-5Mn (TiAlMn) and Ti-43Al-4Nb-1Mo-0.5B (TNM) alloys were studied. The results show that the microstructures of both heat-treated alloys consist of γ/α2 lamellar colony, equiaxed γ phase, and β0 phase. In addition, the globular α2 phase appears in the TNM alloy. The yield strength of TiAlMn alloy increases gradually with the testing temperature, whereas a significant drop from 605 MPa to 469 MPa occurs between 650 °C and 700 °C. In contrast, the TNM alloy exhibits a declining trend with the increasing testing temperature, and a remarkable reduction is observed in the temperature range of 700 °C–750 °C. Moreover, the fracture mode transition from transcrystalline cleavage to intercrystalline with increasing testing temperature was applied to the auxiliary judgment of brittle-to-ductile transition. As a result, the brittle-to-ductile transition temperatures of TiAlMn alloy and TNM alloy are about 650 °C–700 °C and 700 °C–750 °C, which may provide a reference for service temperature range of both alloys.

Ammonia (NH3) is an easy to store, zero-carbon emission hydrogen carrier. The current primary challenges in enhancing the yield and faradaic efficiency of the electrocatalytic nitrogen reduction reaction (NRR) for ammonia synthesis are widely recognized to be the inhibition of the competing hydrogen evolution reaction (HER) and the activation of N≡N to facilitate its cleavage. Here we select perovskite oxide materials La0.6Sr0.4Co0.2Fe0.8+xO3−δ (LSCF0.8+x, x = 0–0.1) as the NRR electrode for the proton-conducting solid oxide electrolyzer cells (PCECs). We construct a more effective metal oxide interface via in situ exsolution of CoFe alloy nanoparticles (NPs), which promotes N≡N activation and cleavage by applying a certain voltage at 500 °C, thereby accelerating the gradual synthesis of NH3 with proton H+. At 500 °C and 0.8 V, the maximum NH3 synthesis rate is 3.75 × 10−9 mol s−1 cm−2 while the highest faradaic efficiency is 3.05%, and there is no damage to the microstructure after continuously working for 100 h, indicating that this material as the electrode is beneficial to the electrocatalytic synthesis of ammonia in PCECs. [ABSTRACT FROM AUTHOR]