Distribution Of Scatterers Research Articles

Coherent Spatially Varying Bidirectional Scattering Distribution Function of Rough Surface

High-resolution synthetic aperture radar (SAR) as an imaging device becomes more and more like a “camera” at the microwave frequency band. How different objects or object surfaces may visually appear in SAR images becomes an interesting research topic. Inspired by the bidirectional reflectance distribution function (BRDF) models employed in computer graphics (CGs), this article proposes the coherent spatially varying bidirectional scattering distribution function (CSVBSDF) for characterizing the electromagnetic scattering and SAR imaging behavior of surfaces. The CSVBSDF establishes a mapping function from observation parameters and surface local parameters to multidimensional measurements. In this article, CSVBSDF of the randomly rough surface is derived via adapting the integral equation method (IEM) to finite-size pixel cells under the plane wave and tapered wave incidence, respectively. It is then validated against the numerical beam simulation method (BSM) in the SAR image domain. A ground-based rail SAR and a 3-D laser scanner are used to measure the SAR image and the corresponding 3-D geometry of a real ground surface. Surface-local parameters, such as the local slope and roughness, are estimated from the measured 3-D geometry and then fed into the CSVBSDF model to produce a synthetic SAR image. Comparison against the real SAR image preliminarily demonstrates the efficacy of the proposed CSVBSDF model.

城市扩张与水污染物排放的伴生效应与交互机理——基于2011-2015年长三角地区的实证检验

PDF HTML阅读 XML下载 导出引用 引用提醒 城市扩张与水污染物排放的伴生效应与交互机理——基于2011-2015年长三角地区的实证检验 DOI: 10.5846/stxb202102230498 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项（A类）（XDA23020101）；国家自然科学基金项目（41971164） Associated effects and interaction mechanism of urban expansion and water pollutant emissions: A case study of the Yangtze River Delta from 2011 to 2015 Author: Affiliation: Fund Project: The Major Program of the Chinese Academy of Sciences, 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:揭示城市扩张与水污染物排放之间的伴生效应与空间交互机理是城市化水环境效应研究的重要议题。以长三角地区为例，选取COD和NH3-N两项特征污染物指标，在2011-2015年快速城市化时期的水污染物排放格局分析基础上，优选空间杜宾模型估计城市扩张与水污染物排放的伴生效应，采用直接效应和间接效应分解定量测度二者的空间交互机理。研究结果表明：2011-2015年长三角地区水污染物排放规模显著下降，县域排放强度等级整体降低，高强度排放格局由连片式分布收缩为零散式分布；城市扩张与水污染物排放的伴生效应显著而稳定，高扩张-高排放型县域在上海及其周边、苏北地区集中分布，沿海和沿江区位是城市扩张通常会选择的布局指向，在排污距离成本和环境规制强度双重作用下，距海岸线和长江干流距离越远，水污染物排放强度越呈对数曲线式降低；城市扩张与水污染物排放的空间交互作用具有两面性，城市扩张规模每提升1%，使本地COD、NH3-N排放分别增加0.274%、0.368%的同时，还会造成邻近县域排放降低1.017%、0.650%。因此，为缓解城市扩张与水污染物排放的伴生效应和交互作用，既要划定城市扩张边界、严格抑制扩张规模，还需注重城市水污染物处理设施配套及管网建设，通过区域环境承载力提升缓解城市化造成的环境胁迫过程。 Abstract:Revealing the associated effect and spatial interaction mechanism between urban expansion and water pollutant emissions is an important issue for studying the water environmental effects of urbanization. The Yangtze River Delta (YRD) has been experiencing rapid urbanization at an annual rate of nearly 1 percent from 2011 to 2015. Rapid urbanization not only increased the impervious surface of a city and changes the structure of the regional ecological environment but also introduced high-density industrial production and urban living activities that accelerated the emission of pollutants. Taking the YRD as an example and selecting COD and NH3-N as two characteristic pollutants, this study described the temporal and spatial characteristics of water pollutant emissions at the county level from 2011 to 2015, optimized the spatial Durbin model (SDM) to estimate the associated effect of urban expansion and water pollutant emissions, and quantitatively measured the spatial interaction between them through direct and indirect effects. The results show that (1) the water pollutant emissions in the YRD have decreased significantly from 2011 to 2015, and the high-intensity emission pattern changed from a contiguous to a scattered distribution, which were concentrated in urban periphery counties and coastal and riverside counties. (2) The associated effect of urban expansion and water pollutant emissions was significant and stable. In 2011, every 1% increase of urban expansion led to 0.293% and 0.319% increase in COD and NH3-N emissions in the YRD, respectively. By 2015, the increase rates of COD and NH3-N emissions reached 0.300% and 0.380%, respectively. The counties with high expansion and high emissions were concentrated in Shanghai and its surrounding areas and northern Jiangsu. (3) The coastal and riverside areas were the layout directions that urban expansion usually chose. Under the control of pollution distance cost and environmental regulation intensity, the farther the distance from the coastline and the Yangtze River, the lower the water pollutant emission intensity. (4) The spatial interaction between urban expansion and water pollutant emissions had two sides. Due to the siphon effect, every 1% increase in the scale of urban expansion resulted in 0.274% and 0.368% increases in local COD and NH3-N emissions, respectively, while emissions in the adjacent counties synchronously decreased by 1.017% and 0.650%, respectively. (5) To break the association and spatial interaction between urban expansion and water pollutant emission and alleviate the environmental stress on the YRD, in addition to delimiting an urban expansion boundary and strictly restraining the scale of expansion, improvement in the regional environmental carrying capacity through urban water pollutant treatment facilities and pipe network construction is urgently needed. 参考文献 相似文献 引证文献

New records of the genus Eilicrinia Hübner, 1823 (Lepidoptera: Geometridae) in Croatia

New records of the genus Eilicrinia Hübner, 1823 in Croatia are presented and the previous literature records are summarized. Eilicrinia cordiaria (Hübner, 1790) has been recorded in Croatia after an apparent absence of 36 years at six new localities. The species has a scattered distribution in the country, with historical records originating from both Mediterranean and Continental regions while recent reports are limited to northern Croatia, mostly around the rivers Drava and Mura. For Eilicrinia trinotata (Metzner, 1845) the first record from Croatia is presented, from Bansko hill in Baranja region. Both species can be considered as scarce in Croatia and further studies are needed in order to assess their status and distribution.

Investigation and optimization of a two-stage cascade ORC system for medium and low-grade waste heat recovery using liquefied natural gas cold energy

This study proposed a two-stage cascade organic Rankine cycle (ORC) to harvest the medium and low-temperature discharged heat from internal combustion engine (ICE), and a liquefied natural gas (LNG) cold energy system is integrated into the proposed cycle in order to realize the cascade utilization of ICE multi-grade waste heat more efficiently. The thermodynamic and economic models are developed to investigate the proposed system performance under steady-state conditions. The influence of the important thermodynamic parameters, e.g. the ORC turbine inlet temperature, the high pressure of first-stage ORC and the outlet temperature of condenser are investigated. The calculated results indicated that the thermal efficiency and the exergy efficiency achieved 27.31% and 33.73%, respectively. In addition, it was found that the total sum unit cost of system product was decreased by increasing turbine Ⅰ inlet pressure. Furthermore, to reach the conflicting compromise between the two aspects of thermodynamic and economic, the Non-dominated Sorting Genetic Algorithm (NSGA-II) is employed to carry out the multi-objective optimization study by which the external investment cost and the thermal efficiency are selected as the objective function. At the same time, the influence region of decision variables related to the optimization is determined according to the scatter distribution of decision variables. Moreover, the exergy destruction and the investment cost ratio of each component under the optimization conditions are analyzed to obtain the preferred performance of the key components. The findings could provide references for the ORC system design and operation driven by multi-grade waste heat.

Towards Environmental RF-EMF Assessment of mmWave High-Node Density Complex Heterogeneous Environments.

The densification of multiple wireless communication systems that coexist nowadays, as well as the 5G new generation cellular systems advent towards the millimeter wave (mmWave) frequency range, give rise to complex context-aware scenarios with high-node density heterogeneous networks. In this work, a radiofrequency electromagnetic field (RF-EMF) exposure assessment from an empirical and modeling approach for a large, complex indoor setting with high node density and traffic is presented. For that purpose, an intensive and comprehensive in-depth RF-EMF E-field characterization study is provided in a public library study case, considering dense personal mobile communications (5G FR2 @28 GHz) and wireless 802.11ay (@60 GHz) data access services on the mmWave frequency range. By means of an enhanced in-house deterministic 3D ray launching (3D-RL) simulation tool for RF-EMF exposure assessment, different complex heterogenous scenarios of high complexity are assessed in realistic operation conditions, considering different user distributions and densities. The use of directive antennas and MIMO beamforming techniques, as well as all the corresponding features in terms of radio wave propagation, such as the body shielding effect, dispersive material properties of obstacles, the impact of the distribution of scatterers and the associated electromagnetic propagation phenomena, are considered for simulation. Discussion regarding the contribution and impact of the coexistence of multiple heterogeneous networks and services is presented, verifying compliance with the current established international regulation limits with exposure levels far below the aforementioned limits. Finally, the proposed simulation technique is validated with a complete empirical campaign of measurements, showing good agreement. In consequence, the obtained datasets and simulation estimations, along with the proposed RF-EMF simulation tool, could be a reference approach for the design, deployment and exposure assessment of the current and future wireless communication technologies on the mmWave spectrum, where massive high-node density heterogeneous networks are expected.

Comparison of deep learning-based emission-only attenuation correction methods for positron emission tomography.

This study aims to compare two approaches using only emission PET data and a convolution neural network (CNN) to correct the attenuation (μ) of the annihilation photons in PET. One of the approaches uses a CNN to generate μ-maps from the non-attenuation-corrected (NAC) PET images (μ-CNNNAC). In the other method, CNN is used to improve the accuracy of μ-maps generated using maximum likelihood estimation of activity and attenuation (MLAA) reconstruction (μ-CNNMLAA). We investigated the improvement in the CNN performance by combining the two methods (μ-CNNMLAA+NAC) and the suitability of μ-CNNNAC for providing the scatter distribution required for MLAA reconstruction. Image data from 18F-FDG (n = 100) or 68Ga-DOTATOC (n = 50) PET/CT scans were used for neural network training and testing. The error of the attenuation correction factors estimated using μ-CT and μ-CNNNAC was over 7%, but that of scatter estimates was only 2.5%, indicating the validity of the scatter estimation from μ-CNNNAC. However, CNNNAC provided less accurate bone structures in the μ-maps, while the best results in recovering the fine bone structures were obtained by applying CNNMLAA+NAC. Additionally, the μ-values in the lungs were overestimated by CNNNAC. Activity images (λ) corrected for attenuation using μ-CNNMLAA and μ-CNNMLAA+NAC were superior to those corrected using μ-CNNNAC, in terms of their similarity to λ-CT. However, the improvement in the similarity with λ-CT by combining the CNNNAC and CNNMLAA approaches was insignificant (percent error for lung cancer lesions, λ-CNNNAC = 5.45% ± 7.88%; λ-CNNMLAA = 1.21% ± 5.74%; λ-CNNMLAA+NAC = 1.91% ± 4.78%; percent error for bone cancer lesions, λ-CNNNAC = 1.37% ± 5.16%; λ-CNNMLAA = 0.23% ± 3.81%; λ-CNNMLAA+NAC = 0.05% ± 3.49%). The use of CNNNAC was feasible for scatter estimation to address the chicken-egg dilemma in MLAA reconstruction, but CNNMLAA outperformed CNNNAC.

An Upper Ediacaran Glacial Period in Cadomia: the Granville tillite (Armorican Massif) – sedimentology, geochronology and provenance

AbstractIn the Cadomian orogenic belt a package of glacigenic sedimentary deposits have been recently described in the Armorican Massif (Normandy, France). The Granville Tillite Member, the middle part of the upper Granville Formation, is late Ediacaran in age. Maximum depositional ages of the pre- and syn-glacial sedimentary deposits obtained by LA-ICP-MS U–Pb detrital zircon dating indicate a maximum age of 561 ± 3 Ma. Combined with geochronological data on the previously described glacial deposits in Cadomia, West Africa, Arabia and Iran, the Granville Tillite Member appears to represent an Upper Ediacaran Glacial Period in northern peri-Gondwana, clearly younger than the c. 580 Ma old Gaskiers glaciation. Detailed mapping and analysis of the depositional regime of two sections near the city of Granville are indicative of two independent glaciomarine lower and upper tillite deposits separated by a distinct conglomeratic marker horizon, evidently a massive gravel beach horizon deposited during an interglacial stage. Age spectra of detrital zircon U–Pb ages constrain the palaeogeographical position of the upper Granville Formation to the periphery of the West African Craton. Post-Gaskiers aged glaciations in Cadomia and in West Africa should be grouped into an Upper Ediacaran Glacial Period dated at c. 565 Ma. This glacial period seems not to be related to the negative δ13C Shuram–Wonoka anomaly. Sedimentary deposits formed during the Upper Ediacaran Glacial Period show a scattered distribution along the marginal orogens of the Gondwana supercontinent independent of palaeolatitude and are coupled most likely to contemporaneous orogenic processes and uplift.

Flow cytometric analysis reveals culture condition dependent variations in phenotypic heterogeneity of Limosilactobacillus reuteri

Optimisation of cultivation conditions in the industrial production of probiotics is crucial to reach a high-quality product with retained probiotic functionality. Flow cytometry-based descriptors of bacterial morphology may be used as markers to estimate physiological fitness during cultivation, and can be applied for online monitoring to avoid suboptimal growth. In the current study, the effects of temperature, initial pH and oxygen levels on cell growth and cell size distributions of Limosilactobacillus reuteri DSM 17938 were measured using multivariate flow cytometry. A pleomorphic behaviour was evident from the measurements of light scatter and pulse width distributions. A pattern of high growth yielding smaller cells and less heterogeneous populations could be observed. Analysis of pulse width distributions revealed significant morphological heterogeneities within the bacterial cell population under non-optimal growth conditions, and pointed towards low temperature, high initial pH, and high oxygen levels all being triggers for changes in morphology towards cell chain formation. However, cell size did not correlate to survivability after freeze-thaw or freeze-drying stress, indicating that it is not a key determinant for physical stress tolerance. The fact that L. reuteri morphology varies depending on cultivation conditions suggests that it can be used as marker for estimating physiological fitness and responses to its environment.

Distribution of seismic scatterers in the San Jacinto Fault Zone, southeast of Anza, California, based on passive matrix imaging

Fault zones are associated with multi-scale heterogeneities of rock properties. Large scale variations may be imaged with conventional seismic reflection methods that detect offsets in geological units, and tomographic techniques that provide average seismic velocities in resolved volumes. However, characterizing elementary localized inhomogeneities of fault zones, such as cracks and fractures, constitutes a challenge for conventional techniques. Resolving these small-scale heterogeneities can provide detailed information for structural and mechanical models of fault zones. Recently, the reflection matrix approach utilizing body wave reflections in ambient noise cross-correlations was extended with the introduction of aberration corrections to handle the actual lateral velocity variations in the fault zone (Touma et al., 2021). Here this method is applied further to analyze the distribution of scatterers in the first few kilometers of the crust in the San Jacinto Fault Zone at the Sage Brush Flat (SGB) site, southeast of Anza, California. The matrix approach allows us to image not only specular reflectors but also to resolve the presence, location and reflectivity of scatterers for seismic waves starting with a simple homogeneous background velocity model of the medium. The derived three-dimensional image of the fault zone resolves lateral variations of scattering properties in the region within and around the surface fault traces, as well as differences between the Northwest (NW) and the Southeast (SE) parts of the study area. A localized intense damage zone at depth is observed in the SE section, suggesting that a geometrical complexity of the fault zone at depth induces ongoing generation of rock damage.

Thoughts and Explorations on the "Separation of Three Rights" System of Rural Homestead

When the separation of the management and ownership right was implemented, famers were entitled to basic residential benefits and the stable development of rural society was maintained. With the rapid development of social urbanization, problems gradually arose concerning the use, management, and transfer of rural homesteads: a large number of idle homesteads, failure in large-scale planting as a result of scattered distribution, and the waste of homesteads, etc. In order to reuse the idle homesteads, increase farmers' income from property, and promote rural revitalization, the central government has proposed the "separation of three rights" system. Combined the policy background with rural development, the paper analyzed the significance of the policy on rural development, the potential risks and principles in implementation from the perspective of historical evolution, policy-making background and policy connotation.

Detecting Rock Glacier Displacement in the Central Himalayas Using Multi-Temporal InSAR

Rock glaciers represent typical periglacial landscapes and are distributed widely in alpine mountain environments. Rock glacier activity represents a critical indicator of water reserves state, permafrost distribution, and landslide disaster susceptibility. The dynamics of rock glacier activity in alpine periglacial environments are poorly quantified, especially in the central Himalayas. Multi-temporal Interferometric Synthetic Aperture Radar (MT-InSAR) has been shown to be a useful technique for rock glacier deformation detection. In this study, we developed a multi-baseline persistent scatterer (PS) and distributed scatterer (DS) combined MT-InSAR method to monitor the activity of rock glaciers in the central Himalayas. In periglacial landforms, the application of the PS interferometry (PSI) method is restricted by insufficient PS due to large temporal baseline intervals and temporal decorrelation, which hinder comprehensive measurements of rock glaciers. Thus, we first evaluated the rock glacier interferometric coherence of all possible interferometric combinations and determined a multi-baseline network based on rock glacier coherence; then, we constructed a Delaunay triangulation network (DTN) by exploiting both PS and DS points. To improve the robustness of deformation parameters estimation in the DTN, we combined the Nelder–Mead algorithm with the M-estimator method to estimate the deformation rate variation at the arcs of the DTN and introduced a ridge-estimator-based weighted least square (WLR) method for the inversion of the deformation rate from the deformation rate variation. We applied our method to Sentinel-1A ascending and descending geometry data (May 2018 to January 2019) and obtained measurements of rock glacier deformation for 4327 rock glaciers over the central Himalayas, at least more than 15% detecting with single geometry data. The line-of-sight (LOS) deformation of rock glaciers in the central Himalayas ranged from −150 mm to 150 mm. We classified the active deformation area (ADA) of all individual rock glaciers with the threshold determined by the standard deviation of the deformation map. The results show that 49% of the detected rock glaciers (monitoring rate greater than 30%) are highly active, with an ADA ratio greater than 10%. After projecting the LOS deformation to the steep slope direction and classifying the rock glacier activity following the IPA Action Group guideline, 12% of the identified rock glaciers were classified as active and 86% were classified as transitional. This research is the first multi-baseline, PS, and DS network-based MT-InSAR method applied to detecting large-scale rock glaciers activity.

Design, exergy analysis, and optimization of a hydrogen generation/storage energy system with solar heliostat fields and absorption-ejector refrigeration system

In the current work, a solar-based energy plant that includes an organic Rankine cycle, an NH3−LiNO3 operated refrigeration system, reverse osmosis desalination, and hydrogen production device are integrated, modeled, and optimized. A parametric examination is designed with Matlab software to show the impact of varying primary system variables on outputs like system total energy, exergy efficiency, and total exergy output. All processes have been carried out for different working fluids, namely iso-butane, Propane, n-octane, and the results are compared. Parametric analysis reveals that at solar radiation of 800 W/m2, which is reasonable for the sun in most of the Middle East, selecting n-Octane as a working media results in an increase in the hydrogen production rate of about 150%. This also confirms the importance of selecting the right working fluid for the ORC unit. Moreover, the influence of substantial decision variables on the hydrogen production, net out pout power, exergy efficiency indicated that multi-criteria optimization is necessary. The multi-objective optimization strategy suggests the TIP = 1753 kPa, Toil = 99°C, ηistur = 0.9, ηispump = 0.87, and AHeliostat = 2800 m2, for the optimum state of the studied system. Additionally, the scatter distribution and sensitivity analysis for optimum point introduced by multi-criteria optimization utilized for better understanding the optimization process.

Using deconvolution to suppress range sidelobes for MIMO sonar imaging

A multiple- input multiple-output (MIMO) sonar can produce a large-aperture virtual array with the use of a small size array and a limited number of elements, which is very useful when applied to underwater acoustic imaging. However, the range sidelobes (SLs) in the MIMO sonar imaging result is high due to the non-ideal orthogonality of transmitting waveforms. In this paper, we propose a deconvolution method to suppress the range SLs. We consider that the range SLs in the imaging result are composed of cross-correlation functions (CCFs) and SLs of auto-correlation functions (ACFs) of transmitting waveforms. And they can be treated as the “noise” term in the output of the convolution between the original distributions of scatterers and a Dirac-like point spread function (PSF). Accordingly, we use the deconvolution method (i.e., the Richardson-Lucy algorithm) to suppress these range SLs. We give the basic processing procedure of the proposed deconvolution method. Simultaneously, we give a simple searching method to find the best PSF corresponding to the lowest range SL level after deconvolution. Numerical simulations and a tank experiment show the proposed deconvolution method can suppress the range SLs effectively.

Study on the Changes of Urban Green Space with Remote Sensing Data: a Comparison of Nanjing and Greater Manchester

Green space effectively maintains urban ecological environment, improves life quality, and promotes sustainable development. Taking Nanjing and Greater Manchester as study cases, based on the land use data from remote sensing interpretation, this study used a combination of mathematical statistics and GIS spatial analysis methods to analyze the evolution of green spatial patterns in terms of general characteristics, gradient characteristics and evolution characteristics, in order to provide scientific reference for the protection of green space and sustainable urban development in Nanjing. Results showed that the green space has increasingly decreased from 2000 to 2010 in Nanjing, and in Greater Manchester, decreased first, then increased from 2000 to 2011. The area of green space gradually increased from the central area to the suburbs and the suburbs in both cities, and in Nanjing it significantly changed in the suburbs and outer suburbs, while in Greater Manchester the changes were mainly in central and suburban areas. We also found that the new towns were the main transfer areas of cold spots while the central areas are mainly the hot spots transfer areas in Nanjing, and outspread shrinkage was the main evolution model; meanwhile, in Greater Manchester, green space had a lower changing intensity as well as smaller cold & hot spots numbers and more scattered distribution, and the evolution model was dominated by endocytosis-type in construction land. This study argued that Nanjing should improve the compactness of the city and regulate the relationship between construction land and green space through land redevelopment and functional replacement within construction land.

Parametric design of an additively manufactured building facade for bespoke response to solar radiation

The building construction industry is adapting Additive Manufacturing (AM) and robotic fabrication techniques to, among other efficiency and cost benefits, reduce the lifecycle Green House Gas (GHG) emissions of new buildings. This research aims to fabricate a low- GHG emission façade by encoding environmental performance using a combination of material selection, AM techniques, and bespoke geometry. This paper presents the design methodology, specifically the response to solar radiation (i.e. shading and daylight transmission). The key contribution of this publication is establishing the digital fabrication process of AM facades: beginning with performative parametric design, using empirical Bi-directional Scattering Distribution Function (BSDF) data of AM thermoplastic elements for daylight simulation to assess performance, and finally optimising the topology for a specific context (location and orientation).

Comfort and efficiency-based improvements to the control of residential Venetian blinds

This study focuses on the control of movable Venetian blinds. Multiple improvements to an existing on/off open-loop control strategy in a case-study apartment have been simulated in TRNSYS 18, thanks to the detailed optical and thermal modelling allowed by the Bidirectional Scattering Distribution Function (BSDF) used as input to the Type56_CFS. The control strategy improvements include the combination of rule-based, closed-loop and discrete state control, in addition to four control strategy activation methods (three use a schedule, and one measures the external temperature). Simulated control inputs include internal temperature, external temperature and vertical irradiance. The results show reductions in overheating, achieved without completely blocking natural illumination or compromising heating demand. While on/off control in winter often leads to increased heating energy consumption, the space sees regular overheating when on/off control is inactive over winter. Conversely, discrete state control is able to more precisely control solar gains in winter to maintain an adequate temperature without utilising the heating system, all the while allowing some level of natural illumination. Ultimately, it is concluded that the choice of the control strategy depends on which objective (minimisation of heating energy consumption, maximisation of daylight harvesting, reduction of overheating risk, etc.) is prioritised.

In-Situ LA-ICP-MS Uraninite U–Pb Dating and Genesis of the Datian Migmatite-Hosted Uranium Deposit, South China

The Datian uranium deposit is a migmatite-hosted, high temperature, hydrothermal deposit in the Kangdian region. Detailed information on the chemical composition and formation age of the uraninite remains lacking, which impedes our understanding of uraninite genesis. Two phases of uraninite have been identified according to their relationships with other minerals and their field relationships. The phase 1 (Ur1) uraninite is characterized by local development of microfractures and pores in the crystal of uraninite, a scattered distribution, and irregular crystal shapes, and it is associated with ilmenite, biotite, and rare earth element (REE) minerals (monazite and xenotime). The phase 2 uraninite (Ur2) has anhedral crystal shapes with well-developed microfractures and pores and is associated with pyrite, albite, pyrrhotite, molybdenite, zircon, and chlorite. X-ray element mapping revealed that the distributions of U, Th, and Pb in the Ur1 uraninite are homogeneous, whereas those in the Ur2 uraninite are heterogeneous. The results of the electron microprobe analysis (EMPA) show that the UO2 and PbO contents of the Ur1 and Ur2 uraninite do not vary significantly. The high ThO2 contents of the Ur1 (1.08–1.68 wt %) and Ur2 uraninite (3.41–4.83 wt %) indicate that they formed at different temperatures. The laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis results show that the ∑REE of the Ur1 uraninite (3747.5–7032.3 ppm) is lower than that of the Ur2 uraninite (8369.2–11,484.3 ppm), and the REE patterns of the Ur1 and Ur2 uraninite are sickle-shaped with large negative Eu anomalies. The LA-ICP-MS U–Pb dating results revealed that the ages of the Ur1 (841.4 ± 4.0 Ma) and Ur2 (834.5 ± 4.1 Ma–837.2 ± 4.5 Ma) uraninite are in consistent with that of the migmatite. Thus, the Datian uranium deposit underwent at least two hydrothermal events, and the uraninite was formed due to the migmatization.

Wave transport in 1D stealthy hyperuniform phononic materials made of non-resonant and resonant scatterers

Stealthy hyperuniform point patterns are characterized by a vanishing spatial Fourier transform around the origin of the reciprocal vector space. The long-range point density fluctuations are suppressed as well in materials consisting of such distribution of scatterers, opening up opportunities to control waves. Beside wave transport in such structured materials are driven by several elements, such as the acoustic properties of the host material, the scatterer characteristics, i.e., dimensions or resonant features, and the scatterer distribution patterns. The effects of these three basic elements on the wave transport properties are usually hard to discriminate. In this work, we analyze the transport properties of acoustic waves in one-dimensional phononic materials constituted of either non-resonant or resonant scatterers distributed along stealthy hyperuniform patterns in air. The pattern is controlled by the stealthiness, allowing us to continuously vary from random phononic materials to phononic crystals. The properties of the scatterers are controlled by their size and/or the resonant frequencies. The properties of the host material are controlled by the viscothermal losses. Transport properties of stealthy hyperuniform materials are found to be robust to both the scatterer dimensions and inherent viscothermal losses, while strongly affected by the scatterer resonances, which introduce sharp dips in the transmission coefficient.

Genotypic variability of Sorbus domestica in Central Europe revealed by the SSR markers

The service tree (Sorbus domestica) is a rare tree species with a scarce distribution across Europe. In Central Europe, where it occurs at northern distribution limits, it is confined to several areas with a very scattered distribution affected by the human impact on the landscape. In this study, we aimed to understand the genetic diversity of its Central European population in a fragmented landscape and its relationship to the origin of different populations. We used 5 microsatellite loci to analyse 189 individuals from 13 populations, mainly from Central Europe with additional sampling from other parts of Europe and Asia. Standard population genetic characteristics and investigation on population structure revealed relatively high genetic diversity within populations, suggesting long-distance pollen dispersal and/or dispersion influenced by humans. All populations showed weak to moderate genetic differentiation, revealing that the marginal Central European population forms clusters that are linked to other Pannonian or Mediterranean populations, whereas Bohemian ones are linked to German populations, suggesting different origins for the populations in the eastern vs. western parts of Central Europe. Genetic variation suggests a natural continuum with neighbouring populations; however, relatively high genetic variation, the character of localities and population structure suggest an anthropogenic origin.

Spatiotemporal Evolution and Trend Prediction of Tourism Economic Vulnerability in China’s Major Tourist Cities

The evaluation and trend prediction of tourism economic vulnerability (TEV) in major tourist cities are necessary for formulating tourism economic strategies scientifically and promoting the sustainable development of regional tourism. In this study, 58 major tourist cities in China were taken as the research object, and an evaluation index system of TEV was constructed from two aspects of sensitivity and adaptive capacity. On the basis of the entropy weight method, TOPSIS model, obstacle diagnosis model, and BP neural network model, this study analyzed the spatiotemporal patterns, obstacle factors, and future trends of TEV in major tourist cities in China from 2004 to 2019. The results show three key findings: (1) In terms of spatiotemporal patterns, the TEV index of most of China’s tourist cities has been on the rise from 2004 to 2019. Cities throughout the coast of China’s Yangtze River Delta and the Pearl River Delta urban agglomeration show high vulnerability, whereas low vulnerability has a scattered distribution in China’s northeast, central, and western regions. (2) The proportion of international tourists out of total tourists, tourism output density, urban industrial sulfur dioxide emissions per unit area, urban industrial smoke and dust emission per unit area, and discharge of urban industrial wastewater per unit area are the five major obstacles affecting the vulnerability degree of the tourism economy. (3) According to the prediction results of TEV from 2021 to 2030, although the TEV of many tourist cities in China is increasing year by year, cities with low TEV levels occupy the dominant position. Research results can provide reference for tourist cities to prevent tourism crises from occurring and to reasonably improve the resilience of the tourism economic system.