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Accurate information on farmland soil heavy metal elements is needed for pollution management and strategic decision making at the national level. In this paper, we review the Chinese literature on soil heavy metal elements (i.e., arsenic, cadmium, chromium, copper, lead, mercury, and zinc) over the past 20 years using meta-analysis. The overall pollution status, spatiotemporal distribution patterns and driving factors of heavy metals in China's farmland soil are explored by using the geoaccumulation index, the standard deviation ellipse method and the PCA/APCS model, respectively. The results show that most heavy metals in farmland soil from the study cases are similar to the world average. Seven types of elements have increased compared with background values. Cd and Hg have become the top polluting elements in China and industrial and agricultural activities are the main sources of current heavy metal element enrichment. Regional natural-social-economic differences have led to significant spatial heterogeneity of heavy metal pollution, showing an intensity pattern unfavourable to national food security. In the time period, the overall distribution range gradually increased with the accelerated growth of regional industrial output, and there was a tendency for the gravity centre of the pollution studies to migrate inland to the northwest and southwest. Regionally differentiated environmental regulation and pollution remediation measures should be developed for pollution prevention and control in the future.

The low sulfur utilization, cycling instability, and sluggish kinetics are the critical obstructions to practical applications of lithium-sulfur batteries (LSBs). Constructing sulfur hosts with high conductivity, suppressed shuttle effect, and rapid kinetics is essential for their practical application in LSBs. Here, we synthetically utilized the merits of ZnSe quantum dots (QDs) and layered Ni(OH)

Described here are tandem photoelectrocyclization and [l,5]-hydride shift reactions of heteroaryl-containing bis-aryl cyclohexenone derivatives that give heteroaryl-substituted dihydrophenanthrenes. This Letter demonstrates that electrocyclization intermediates can be trapped with acid when the [l,5]-hydride shift is relatively slow. From a practical perspective, the observation that the acid-mediated reaction gives a divergent stereochemical outcome when compared with the reaction run under neutral conditions makes these transformations powerful.

The Heihe River Basin is located in the arid and semi-arid regions of Northwest China. Here, the terrestrial ecosystem is vulnerable, making it necessary to identify the factors that could affect the ecosystem. In this study, MODIS-NDVI data with a 250-m resolution were used as a proxy for the terrestrial ecosystem. By combining these with environmental factors, we were able to explore the spatial features of NDVI and identify the factors influencing the NDVI distribution in the Heihe River Basin during the period of 2000–2016. A geographical detector (Geodetector) was employed to examine the spatial heterogeneity of the NDVI and to explore the factors that could potentially influence the NDVI distribution. The results indicate that: (1) the NDVI in the Heihe River Basin appeared high in the southeast while being low in the north, showing spatial heterogeneity with a q-statistic of 0.38. The spatial trend of the vegetation in the three sub-basins generally increased in the growing seasons from 2000 to 2016; (2) The results obtained by the Geodetector (as denoted by the q-statistic as well as the degree of spatial association between the NDVI and environmental factors) showed spatial heterogeneity in the associations between the NDVI and the environmental factors for the overall basin as well as the sub-basins. Precipitation was the dominant factor for the overall basin. In the upper basin, elevation was found to be the dominant factor. The dominant factor in the middle basin was precipitation, closely followed by the soil type. In the lower basin, the dominant factor was soil type with a lower q-statistic of 0.13, and the dominant interaction between the elevation and soil type was nonlinearly enhanced (q-statistic = 0.22).

Earthquakes exhibit clear clustering on the earth. It is important to explore the spatial-temporal characteristics of seismicity clusters and their spatial heterogeneity. We analyze effects of plate space, tectonic style, and their interaction on characteristic of cluster. Based on data of earthquakes not less than moment magnitude (MW) 5.6 from 1960 to 2014, this study used the spatial-temporal scan method to identify earthquake clusters. The results indicate that seismic spatial-temporal clusters can be classified into two types based on duration: persistent clusters and burst clusters. Finally, we analysed the spatial heterogeneity of the two types. The main conclusions are as follows: 1) Ninety percent of the persistent clusters last for 22–38 yr and show a high clustering likelihood; ninety percent of the burst clusters last for 1–1.78 yr and show a high relative risk. 2) The persistent clusters are mainly distributed in interplate zones, especially along the western margin of the Pacific Ocean. The burst clusters are distributed in both intraplate and interplate zones, slightly concentrated in the India-Eurasia interaction zone. 3) For the persistent type, plate interaction plays an important role in the distribution of the clusters’ likelihood and relative risk. In addition, the tectonic style further enhances the spatial heterogeneity. 4) For the burst type, neither plate activity nor tectonic style has an obvious effect on the distribution of the clusters’ likelihood and relative risk. Nevertheless, interaction between these two spatial factors enhances the spatial heterogeneity, especially in terms of relative risk.

Schlieren visualizations of flowfield structures of supersonic film cooling in a backward-facing step were conducted in a Mach 2.95 suction wind tunnel with the film coolant tangentially ejected th...

This paper analysed the evolution of landslide research and research foci in different countries. The data comprise 3105 landslide SCI articles published between January 1977 and June 2015 from the Web of Science. The data are extracted under interaction constraints of the journal title, category, and keywords. The complex network method is used for the analysis. First, from the perspective of topics and methods, the evolution is systematically assessed by generating a co-citation network of the articles and a semantic cluster analysis. Second, from the perspective of topics and landslide-related disasters, the focus in different countries is discussed by generating co-occurrence networks. These networks are the co-occurrence of the countries and keywords, and the co-occurrence of countries and landslide-related disaster phrases. The main conclusions are as follows: (1) landslide susceptibility analysis and methods of machine learning are popular research topics and methods, respectively. The topics change through time, and the article output is influenced by increasing landslide-related disasters, increasing economic losses and casualties, a desire for a more complete and accurate landslide inventory, and the use of effective methods, such as geographical information Science (GIS) and machine learning. (2) The research focus in each country is related with the country-specific disasters or economic costs caused by landslides to some degree. In addition to Italy and the USA, China is the country most commonly affected by landslides, and it should develop its own landslide database and complete in-depth studies of disaster mitigation.

Agricultural drought is related to meteorological and hydrologic conditions and the resilience vegetation to water deficit that have negative impacts on agricultural production. In this study, an integrated drought condition index (IDCI) was developed by integrating precipitation, potential evapotranspiration, temperature, soil moisture, and vegetation conditions. The performance of IDCI in agricultural drought monitoring was evaluated by comparing with standing drought indices, such as sc-PDSI (self-calibrated Palmer Drought Severity Index), SMCI (Soil Moisture Condition Index), and SCYI (Scaled Crop Yields Index). Then, IDCI was used to characterize the spatiotemporal pattern of agricultural drought across Inner Mongolia, China. Results indicated that: (1) IDCI performed as well in drought monitoring as did sc-PDSI and SCYI. However, IDCI performed better than did SPEI3 (standardized precipitation evapotranspiration index at a time scale of 3 months), SMCI (Soil Moisture Condition Index) and VCI (Vegetation Condition Index) with respect to reliable and stable drought monitoring, detection of soil moisture and reflection of agricultural loss; (2) during the growing season (May-September), the frequency of droughts with higher than moderate drought intensity tended to be diminishing from May to August, and was amplifying again from August to September; (3) during 2000 to 2014, the drought severity was subject to regular variability with consecutive droughts during transitions between drought conditions; (4) compared to SMCI, VCI and SPEI3, IDCI is highly related to SCYI for maize with correlation coefficient of up to 0.788; the correlation coefficients between IDCI and SCYI for soybean and potato are larger than 0.5, while the SCYI for wheat is related to droughts with severe and even higher severity based on IDCI. The idea behind the development of IDCI can be referenced for drought monitoring in other regions of the globe.

The Himalayan-Tibetan Plateau (HTP), often known as the “Third Pole” and the “Asian Water Tower”, is the source of water resources for many Asian rivers and in turn for hundreds of millions of people living downstream. The HTP has direct impacts on the establishment and maintenance of Asian monsoon, and therefore on the climate of its surrounding areas. Besides, soil moisture plays a critical role in the hydrological cycle and is a critical link between land surface and atmosphere. Hence, soil moisture was greatly emphasized by Global Climate Observing System Programme as an Essential Climate Variable. However, little is known about soil moisture changes on the HTP from a long-term perspective. By comparing remotely sensed and modelled soil moisture datasets against in-situ observations from 100 observation stations, here we find that Noah performed better than other soil moisture datasets. In past years, soil moisture first decreased and then increased obviously. In most regions on HTP, precipitation changes can be taken as the major cause behind soil moisture variations. In future, there is persistently decreasing soil moisture trend since ~2010 with a decreasing rate of −0.044 kg/m2/10a, −0.031 kg/m2/10a and −0.0p 88 kg/m2/10a under RCP2.6, RCP4.5 and RCP8.5 scenarios, respectively, in CMIP5 (Coupled Model Intercomparision Project Phase 5). Specifically, a sudden decrease of soil moisture with a rate of −0.372 kg/m2/10a can be expected after ~2080 under RCP8.5 scenario. Amplifying terrestrial aridity due to increasing precipitation but more significant increasing potential evapotranspiration potentially results in drying HTP. Potential water deficiency for Asian rivers due to drying HTP should arouse considerable concerns.

Human-induced impacts, such as urbanization, on regional climate changes and precipitation changes in particular have been attracting increasing international interests. However, there are different evaluations of urban effects on precipitation changes in both space and time. In this study, taking Beijing Municipality (BJM) as a case study, the hourly precipitation data from 20 automatic weather stations for a period of 2011–2015 were analyzed using the circular statistical analysis and grange causality test technique. Changes in precipitation intensity, amount, duration, and timing were investigated, and extreme precipitation indices were defined by percentiles and consecutive precipitation processes. Results indicated that impacts on precipitation varied with the type of urbanization. Urban areas with the highest population density were dominated by the slightly longer precipitation duration, higher precipitation intensity and larger precipitation amount with lengthening consecutive dry days. Therefore, urbanization has the potential to intensify precipitation processes. In addition, due to varying topographical features in the vicinity of BJM, complicated precipitation changes can be identified along two sides of the urban area. Larger precipitation amount and higher precipitation intensity can be found along the western side than along the eastern flank of the BJM. Further, higher precipitation amount can be observed in the downwind areas. High-level urban heat island can trigger more pronounced urban precipitation islands which lags behind the UHI. What's more, urban high buildings can benefit slowing down air mass, hence lengthening precipitation events. These results provide useful information for management of urban activities, and offer a new viewpoint for further understanding of the urban precipitation island (UPI) effect.

In the communication systems employing cooperative jamming (CJ), frequency mismatch will degrade its jamming suppression performance. This paper aims to investigate the suppression performance degradation of the CJ sheltered frequency hopping (FH) systems under unknown frequency mismatch. First, the system transceiver architecture is detailed illustrated. Then, the residual CJ after suppression is mathematically depicted, and the closed-form expression for the CJ suppression ratio (CJSR) is provided. Finally, the expectation and cumulative distribution function (CDF) of CJSR are derived to measure the degradation of suppression performance for unknown frequency mismatch. Theoretical and simulation results confirm that frequency mismatch in actual FH systems will degrade its CJ suppression performance, and this degradation will get worse for longer hop length or larger CJ power, which guides the actual transceiver design.

Spatiotemporal fusion (STF) is considered a feasible and cost-effective way to deal with the trade-off between the spatial and temporal resolution of satellite sensors, and to generate satellite images with high spatial and high temporal resolutions. This is achieved by fusing two types of satellite images, i.e., images with fine temporal but rough spatial resolution, and images with fine spatial but rough temporal resolution. Numerous STF methods have been proposed, however, it is still a challenge to predict both abrupt landcover change, and phenological change, accurately. Meanwhile, robustness to radiation differences between multi-source satellite images is crucial for the effective application of STF methods. Aiming to solve the abovementioned problems, in this paper we propose a hybrid deep learning-based STF method (HDLSFM). The method formulates a hybrid framework for robust fusion with phenological and landcover change information with minimal input requirements, and in which a nonlinear deep learning-based relative radiometric normalization, a deep learning-based superresolution, and a linear-based fusion are combined to address radiation differences between different types of satellite images, landcover, and phenological change prediction. Four comparative experiments using three popular STF methods, i.e., spatial and temporal adaptive reflectance fusion model (STARFM), flexible spatiotemporal data fusion (FSDAF), and Fit-FC, as benchmarks demonstrated the effectiveness of the HDLSFM in predicting phenological and landcover change. Meanwhile, HDLSFM is robust for radiation differences between different types of satellite images and the time interval between the prediction and base dates, which ensures its effectiveness in the generation of fused time-series data.

Extreme high temperature (EHT) events have caused serious impact on society. In previous research, EHT indices seldom consider spatial aggregation. To conduct the comprehensive evaluation, the global EHT days from 1979 to 2017 have been evaluated in terms of high temperature duration, accumulative temperature intensities and magnitude of spatial aggregation based on ERA‐Interim 2 m air temperature data set. In addition, abnormal warming of polar and ocean surfaces has rarely been addressed in global‐scale studies. To address this deficiency, the indices of EHT days are normalized by maximum in history for each location. To solve the time discontinuity problem on EHT spatiotemporal distribution in previous studies, we utilized spatiotemporal scan statistics to detect EHT spatiotemporal clusters (EHT‐STCs), and clusters correspond to a certain spatiotemporal extent where the EHT events are aggregated. This method actualizes time‐continuous and spatiotemporal integral detection. The results show the following: 1. There are apparent changes in EHT‐STC spatial distribution after 1999, so 1999 can be recognized as the critical time node of EHT‐STC spatial transformation. 2. After 1999, the EHT‐STC number gradually increased, and the duration and spatial coverage of EHT‐STC gradually expanded. Overall, EHT‐STCs display a significant northward migration, with an average northward movement of 7.03° for each transition from 1979 to 2017. 3. There are differences in the extremity and transformation process in different regions. EHT‐STCs in Antarctica are concentrated before 1992, with the strongest EHT extremity; EHT‐STCs in the Arctic and middle‐low latitude continents are concentrated after 2010 and 1999 respectively, both with a strong EHT extremity. There is a similar EHT‐STC number in the middle‐low latitude ocean before and after 1999 with the weakest extremity. These results contribute to determining EHT causes and future trends in global climate change.

The vulnerability of vegetation ecosystems and hydrological systems in high-altitude areas makes their phenology more sensitive and their response to climate change more intense. The Qilian Mountains, an important geographic unit located in the northeastern Tibetan Plateau (TP), has experienced the more significant increases in temperature and precipitation in the past few decades than most areas of the TP. However, under such intense climate change, the temporal and spatial differences in phenology in the Qilian Mountains are not clear. This study explored the spatial and temporal heterogeneity of phenology in the Qilian Mountains from 1982 to 2014 and its response to three temperature indicators, including the mean daily temperature (Tmean), mean daily daytime temperature (Tmax), and mean daily nighttime temperature (Tmin). The results showed that (1) as the altitude rose from southeast to northwest, the multiyear mean of the start of the growing season (SOS) was gradually delayed mainly from 120 to 190 days, the multiyear mean of the end of the growing season (EOS) as a whole was advanced (from 290 to 260 days), and the multiyear mean of the length of the growing season (LGS) was gradually shortened (from 150 to 80 days). (2) In general, there was an advanced trend in the annual average SOS (0.2 days per decade), a delayed trend in the annual average EOS (0.15 days per decade), and an extended trend in the annual average LGS (0.36 days per decade) over the study period. However, there has been no significant phenological trend in recent years, especially for the SOS after 2000 and the EOS and LGS after 2003. (3) Higher preseason temperatures led to an advanced SOS and a delayed EOS at the regional scale. Moreover, the SOS and EOS were more triggered by Tmax than Tmin and Tmean. The LGS was significantly positively correlated with annual mean temperature (r = −0.82, p < 0.01).

Cropland redistribution to marginal land has been reported worldwide; however, the resulting impacts on environmental sustainability have not been investigated sufficiently. Here we investigated the environmental impacts of cropland redistribution in China. As a result of urbanization-induced loss of high-quality croplands in south China (∼8.5 t ha–1), croplands expanded to marginal lands in northeast (∼4.5 t ha–1) and northwest China (∼2.9 t ha–1) during 1990–2015 to pursue food security. However, the reclamation in these low-yield and ecologically vulnerable zones considerably undermined local environmental sustainability, for example increasing wind erosion (+3.47%), irrigation water consumption (+34.42%), fertilizer use (+20.02%) and decreasing natural habitats (−3.11%). Forecasts show that further reclamation in marginal lands per current policies would exacerbate environmental costs by 2050. The future cropland security risk will be remarkably intensified because of the conflict between food production and environmental sustainability. Our research suggests that globally emerging reclamation of marginal lands should be restricted and crop yield boost should be encouraged for both food security and environmental benefits., Widespread loss of high-quality cropland induced by urbanization and increasing shift of crop production to low-quality marginal land threaten food security and environmental sustainability.

Coronavirus disease 2019 (COVID‐19) has spread around the world and requires effective control measures. Like the human‐to‐human transmission of the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2), the distribution of COVID‐19 was driven by population flow and required emergency response measures to slow down its spread and degrade the epidemic risk. The local epidemic risk of COVID‐19 is a combination of emergency response measures and population flow. Because of the spatial heterogeneity, the different impacts of coupled emergency responses and population flow on the COVID‐19 epidemic during the outbreak period and a control period are unclear. We examined and compared the impact of emergency response measures and population flow on China's epidemic risk after the Wuhan lockdown during the outbreak period and a control period. We found that the population flow out of Wuhan had a long‐term impact on the epidemic's spread. In the outbreak period, a large population flow out of Wuhan led to nationwide migration mobility, which directly increased the epidemic in each province. Meanwhile, quick emergency responses mitigated the spread. Although low population flow to provinces far from Hubei delayed the outbreak in those provinces, relatively delayed emergency response increased the epidemic in the control period. Consequently, due to the strong transmission ability of the SARS‐CoV‐2 virus, no region correctly estimated the epidemic, and the relaxed emergency response raised the epidemic risks in the context of the outbreak., Key Points Population outflow from Wuhan had a long‐term impact on the spread of COVID‐19Areas with low population inflow lacked awareness of prevention, started emergency response later, and failed to prevent the COVID‐19 caused by population mobilityThe degree to which population mobility and emergency measures affected the development of the epidemic exists spatial heterogeneity in China

This study demonstrates manipulation of luminance from CaF2: Yb3+, Er3+ up-conversion (UC) micronano particles emissions and the fluorescence intensity improvement by using various surface plasmon resonance substrates which consist of SiO2, gold thin film, and nano cones from bottom to the top in the view of side structure. When they are applied, the optimum enhancement of the intensity of red up-conversion luminescence (UCL) peaked at 653 nm shows up to 189-fold. The distance dependent intensities of two UC micro-nano particles manipulated by holographic optical tweezers (HOT) are also illustrated in this article. The fluorescence intensities decrease when two UC micro-nano particles become near to the each other due to the inter-system transition at the much short distance.

It is difficult to cut through a transparent material such as polyethylene (PE) film with a continuous-wave (CW) laser of the near-infrared wavelength, because of the low absorption of laser energy. The plasma induced by a pulsed laser, however, can damage the surface of a film, which can change the transparency of the material. In this study, a transparent PE film with a thickness of 0.6 mm was irradiated by various combinations of focused laser pulses and a CW laser. The test conditions and the processes were recorded visually by a Schlieren optics system on the side surface of the film and by a high-speed camera on the front surface. From the results, it can be concluded that, though it is difficult to cut through a transparent material such as PE film with only a pulsed or CW laser alone, once the transparency of the surface has been modified by multiple focused laser pulses, the PE film can be cut through easily by a CW laser with a near-infrared wavelength.

To further enhance the security of the wireless communication systems, an architecture of the cooperative jamming (CJ) assisted slow frequency-hopping (FH) systems is proposed in this paper. Then, after the CJ cancellation operation, the residual CJ raised from synchronization error is analyzed, where the inter-symbol interference (ISI) is employed to depict the time misalignment between the received signal and the local reference CJ at the receiver, and the inter-hop interference (IHI) is introduced to describe the frequency misalignment. In addition, the closed-form expression of the jamming cancellation ratio (JCR) is derived to evaluate the CJ cancellation performance. Theoretical analyses and simulation results show that in the slow FH systems, both the proportions of the ISI and IHI components in the residual CJ are jointly determined by the synchronization error and the hop length. Besides, the JCR increases with the increase of the hop length and the jamming-to-noise ratio (JNR), and decreases with the increase of the synchronization error.

Er3+-sensitized upconversion nanoparticles (UCNPs) have attracted great attention due to their tunable upconversion (UC) emissions, low cytotoxicity, high resistance to photobleaching and especially multiple effective excitation wavelengths. However, detailed energy conversion between Er3+ and Tm3+ ions in Y2O3 UCNPs is still a problem, especially under multi-wavelength and variable pulse width excitation. In this work, we successfully fabricated a series of Er3+-sensitized Y2O3 nanocrystals by a spray flame synthesis method with a production rate of 40.5 g h&minus, 1. The as-prepared UCNPs are a pure cubic phase with a mean size of 14 nm. Excited by both 980 and 808 nm lasers, the tunable upconversion luminescence (UCL) from Er3+ ions was achieved by increasing the Er3+ doping concentration, co-doping Tm3+ ions and extending excitation pulse-width. The investigations of the lifetimes and the laser power dependence of UC emissions further support the proposed mechanism, which provides guidance for achieving effective color control in anticounterfeiting and multiplexed labeling applications. In addition, the red UC emission at about 5 mm beneath the tissue surface was observed in an ex vivo imaging experiment under the excitation of 808 nm laser, indicating that the Y2O3:Er3+/Tm3+ UCNPs have great prospects in further biological applications.

Authenticity is a controversial concept in heritage studies. This is particularly the case where the reconstruction of heritage spaces is carried out to facilitate multiple objectives, namely, preservation, tourism development and improving the quality of life of local residents. Based on a qualitative methodology with a case study approach, this paper uses participant observation, in-depth interviews and textual analysis to explore the varying perceptions of authenticity for a reconstructed heritage site from the point of view of heritage experts, tourists and local residents. We identify a form of &lsquo, relational authenticity&rsquo, Using the Dingding Gate, part of the Luoyang World Heritage section of the Silk Road, this paper highlights the phenomenon of &lsquo, reconstructed heritage space&rsquo, with the relational authenticity of different actors in the Chinese context. We argue that relational authenticity is embedded in the networks between people, place, and (re)materialized space, which is the assemblage of excavated original objects and reconstructed buildings and spaces. Relational authenticity is acquired through a rematerializing process engaged by actors, who focus on the material qualities, instead of material authenticity and originality, of the original excavated objects and later reconstructed space.

Sustainable development appears to be the theme of our time. To assess the progress of sustainable development, a simple but comprehensive index is of great use. To this end, a multivariate index of sustainable development was developed in this study based on indicators of the United Nations Sustainable Development Goals (SDGs). To demonstrate the usability of this developed index, we applied it to Fujian Province, China. According to the China SDGs indicators and the Fujian situation, we divided the SDGs into three dimensions and selected indicators based on these dimensions. We calculated the weights and two indices with the entropy weight coefficient method based on collecting and processing of data from 2007 to 2017. We assessed and analyzed the sustainable development of Fujian with two indices and we drew three main conclusions. From 2007 to 2017, the development index of Fujian showed an increasing trend and the coordination index of Fujian showed a fluctuating trend. It is difficult to smoothly improve the coordination index of Fujian because the development speeds of Goal 3 (Good Health and Well-being) and Goal 16 (Peace, Justice, and Strong Institutions) were low. The coordination index of Fujian changed from strong coordination to medium coordination from 2011 to 2012 because the development speed of the environmental dimension suddenly improved. It changed from strong coordination to medium coordination from 2015 to 2016 because the values of the development index of the social dimension were decreasing. To the best of our knowledge, these are the first SDGs-based multivariate indices of sustainable development for a region of China. These indices are applicable to different regions.

Evaluation of arable land ecosystem services capacity and arable land-use intensity (ALUI) is important for recognising key regional factors that impact arable land attributes changes, which is crucial for planning sustainable patterns of arable land use. The chronic lack of coordination between these two types of evaluation studies has made it hard to provide enough information for developing arable land-use management and control policies. Here, we generated a 1-km-grid map of arable land potential yield and county-level arable land productive-capacity. The impact of land-use and land-cover change on county-level total arable land productive-capacity during 1990–2010 had been estimated. Then we determined the aggregation–distribution characteristics of four indexes (i.e. average arable land potential yield, average ALUI, total arable land area and arable land productive-capacity reserves) at the county-level by the k-means algorithm to assess the regional coordination between arable land productive-capacity protection and arable land use. The results show that during 1990–2010, land-use change led to arable land productive-capacity decreases in 2007 of China’s 2733 counties (nearly 73.5% of the total counties’ count). Most of these counties are in central and southern China, and their corresponding arable land productive-capacity decrement rates are generally 6.15% are mainly in the Yangtze and Pearl River delta regions. The geographical detector shows that county-level arable land-area change is a primary factor that drives county-level arable land productive-capacity increase. Its determinant power can be quantified as 74.154%. In contrast, its determinant power to county-level arable land productive-capacity decrease is only 38.542%, which demonstrates that occupy high-capacity arable land and supplement low-capacity arable land have a greater role in causing reduction of county arable land productive-capacity. Total arable land productive-capacity and use intensity show only slight determinant power to county-level arable land productive-capacity decrease. It indicates that insufficient attention has been paid to the protection of arable land productive-capacity and the farmers’ willingness in the implementation of China requisition-compensation balance policy. The aggregation–distribution characteristics show that arable land productive-capacity protection is in coordination with arable land use for most of the provinces in China. Arable land with high or medium potential yield tends to be used at high or medium intensity. A lack of coordination is most evident in the insufficient ALUI, particularly in seven of the thirteen major grain-producing provinces. Other evidence of weak coordination is in the low potential yield versus high farming conditions and willingness, where unsuited planting modes should be prevented. Lastly, challenges for exploring sustainable arable land use path have been discussed. This study is greatly instructive for recognising interrelations between natural conditions and arable land-use patterns and for exploring shortcomings that impede regionally sustainable arable land use.

Poyang Lake basin is one of the most biodiversity areas in China. Fluctuation of water level is an important factor of hydrological process which is a guarantee of ecosystem health and biodiversity conservation. To measure its spatial-temporal variation, classical statistical methods and permutation entropy were employed: 1) Variation of water level downstream of Poyang Lake during one year follows a periodical pattern, while it is random in upper reaches. That is, the range of water level in upper reaches is much less than that in downstream. 2) Fluctuation of water level in winter and spring is more complicated, more irregular and more random than that in other seasons. This is because in winter and spring, precipitation directly causes rising in water level rather than generating surface runoff, while it is reversed in summer. 3) The ranges, standard deviation, coefficient of variation and fluctuation of water level decrease with rising in elevation. 4) In sub-basin scale, fluctuation of water level in upper reaches is more complicated than that in downstream, e specially along one river. Mechanically, catchment size and confluence process may be the main factors influencing fluctuation of water level over Poyang Lake basin.

Remote sensing can provide near real-time and dynamic monitoring of drought. The drought severity index (DSI), based on the normalized difference vegetation index (NDVI) and evapotranspiration/potential evapotranspiration (ET/PET), has been used for drought monitoring. This study examined the relationship between the DSI and winter wheat yield for prefecture-level cities in five provinces of eastern China during 2001–2016. We first analyzed the spatial and temporal distribution of droughts in the study area. Then the correlation coefficient between drought-affected area and detrended yield of winter wheat was quantified and the impact of droughts of different intensities on winter wheat yield during different growth stages was investigated. The results show that incipient drought during the wintering period has no significant impact on the yield of winter wheat, while moderate drought in the same period can reduce yield. Drought affects winter wheat yield significantly during the flowering and filling stages. Droughts of higher intensity have more significant negative effects on the yield of winter wheat. Monitoring of droughts and irrigation is critical during these periods to ensure normal yield of winter wheat. This study has important practical implications for the planning of irrigation and food security.

Schlieren and shadowgraph visualizations of flowfields in a typical configuration of supersonic film cooling in a backward-facing slot were conducted in a Mach 2.95 continuous-suction wind tunnel, ...

Develop circular agriculture is an effective way to reduce pollution and achieve sustainable agricultural development. At present, both the government and scholars have stressed employing agricultural wastes at multiple levels and extending the industrial chain as much as possible. However, whether the abovementioned strategy is environmentally friendly is worth consideration. To address this issue, by using the evaluation method of Life Cycle Assessment (LCA) and taking the circular agriculture industry company of Xingyuan, Fuqing, Fujian as an example, this paper analyzes different circular agriculture models and explores the environmental loads and environmental benefits of each sub-industrial chain from the environmental and economic-environmental viewpoints. The results show that, from the LCA perspective, a longer industrial chain of circular agriculture is not better and at different evaluation angles, different optimal combinations of the industrial chain models of circular agriculture can achieve the minimum environmental load or the highest environmental benefit. This study will be useful for newly built enterprises or sector-integrated park to design new recycling networks from the life cycle and economic-environmental impact perspectives.

Understanding the spatial distribution patterns (SDPs) of natural disasters plays an essential role in reducing and minimizing natural disaster risks. An integrated discussion on the SDPs of multiple global disasters is still lacking. In addition, due to their high quantity and complexity, natural disasters constitute high-dimensional data that represent a challenge for an analysis of SDPs. This paper analyzed the SDPs of global disasters from 1980 to 2016 through biclustering. The results indicate that the SDPs of fatality rates are more uneven than those of occurrence rates. Based on the occurrence rates, the selected countries were clustered into four classes. (1) The major disasters along the northern Pacific and in the Caribbean Sea and Madagascar are storms, followed by floods. (2) Most of Africa is mainly affected by floods, epidemics, and droughts. (3) The primary disaster types in the Alpine-Himalayan belt and the western Andes are floods and earthquakes. (4) Europe, America, Oceania, and South and Southeast Asia are predominantly influenced by floods. In addition, according to the fatality rates, the selected countries were clustered into eight classes. (1) Extreme high temperatures mostly result in high fatality rates (HFRs) in developed countries. (2) Epidemics lead to HFRs in parts of Africa. (3) Droughts produce HFRs in East Africa. (4) Earthquakes result in HFRs along the eastern Pacific coastline and the Alpine-Himalayan belt. (5) Tsunamis mainly cause HFRs in Thailand, Indonesia, and Japan. (6) Storms result in scattered but distinct HFRs along the coastal regions of the Pacific and Indian Oceans. (7) Floods cause concentrated HFRs in South Asia and northeastern South America. (8) Finally, volcanoes cause HFRs in Colombia, while extreme low temperatures cause HFRs in Ukraine and Poland.

Photon upconversion (UC) based on self-sensitization of lanthanide-doped nanocrystals is of great importance for biological and photonic applications. Here, we report tunable multicolor display and sensitive temperature sensing in the erbium-doped CaF2 upconversion nanocrystals (UCNCs) codoped with Tm3+ ions. Under the excitation of 980, 808 and 1532 nm lasers, the upconversion luminescence (UCL) color of these self-sensitized UCNCs can be manipulated from green to red efficiently and the red-to-green (R/G) UC intensity ratio is promoted remarkably as the doping Tm3+ ions vary from 0 to 4 mol%. Especially, we have successfully demonstrated the multicolor modulation of these UCNCs by changing the pulse width and repetition frequency under multi-wavelength excitation. The power dependence and decay lifetimes measurements of Er3+ ions under multi-wavelength excitation were carried out to clarify the UC color manipulation. In addition, the optical temperature sensing properties of CaF2:Er3+/Tm3+ (10/0.125 mol%) UCNCs are also studied thoroughly under 980, 808 and 1532 nm lasers excitation, and the results show that the UCNCs possess outstanding thermal sensitivity. The features enable these UCNCs to act as promising candidates for high-resolution biological imaging, multicolor display and nanoscale thermometer fields.

Watershed system models are important tools for understanding complex watershed systems and integrated river basin management. However, there are very few models that can represent the coevolution of water, ecology and socioeconomic system at the river basin scale. In this study, a watershed system model was developed using the case of the Heihe River basin (HRB), a typical endorheic river basin in Northwest China. The model is mainly composed of an integrated ecohydrological model, a socioeconomic model, and two interface models. It has been embedded into a decision support system using the surrogate modeling technique. The watershed system model proved to be reliable in simulating multiple eco-hydrological processes, and showed good abilities in exploring the trajectories and interactions of water, ecology and socioeconomy. This study advances our understanding of the water-land-air-plant-human nexus at the watershed scale, and has great implications for sustainable developments in endorheic river basins.

Purpose The purpose of this study is to propose a method to retrieve data on an event based on a preliminary collection of event-specific hashtags. Design/methodology/approach Extra knowledge, or a list of events with recorded features that can be used to characterize an event and separate it from other simultaneously occurring social phenomena, is employed. The first step involves the estimation and use of the impact area to retrieve messages from Twitter. This is followed by an extraction of hashtags from these messages. After that, the noisy hashtags would be filtered out by some heuristic rules. Finally, hashtags are used to collect relevant messages from not only Twitter but also other social media platforms. Findings The proposed method has high selectivity and is able to collect distinct sets of hashtags even for similar simultaneous events. In addition, spatial and temporal features are sufficient to improve collecting information of disaster events. Originality/value This work discusses a method of information retrieval of an event from cross-platform social media. The proposed method can be applied to other studies of geographically related events.

Ecohydrology, aiming to study the interactions between terrestrial ecological systems and hydrological cycles as well as their impacts on water management, has been an emerging interdisciplinary research field since the 20th century. It hosts both natural and human regulated processes that are potentially coupled in complex ways. Understanding the ecological-hydrological processes, the fundamental mechanisms and the connections between them is critical since these processes are not isolated but integrated to impact basin- scale hydrological and biogeochemical functioning of a larger river system, especially in arid environment where water resources are considered to be the source of life. Thus, research on ecological-hydrological processes in arid environment is not only a scientific focus area but also important to sustainable development. Research projects and initiatives involved in observation, measurement, modeling and data assimilation have been well-developed for those purposes over the past 20 years. This review summarizes the historical development of ecohydrology science in China and the state-of-the-art tools available in the research framework. Five grand scientific challenges are listed as prospects and exciting opportunities for the scientific community. To advance the current ecological-hydrological processes research, scientists from multidisciplinary backgrounds (such as geography, geology, geomorphology, hydrology, geochemistry and ecology), need to unite to tackle the many open problems in new dimensions.

Flexible and high-performance electromagnetic absorbing materials of three-dimensional (3D) hierarchical reduced graphene oxide (RGO) foams decorated with in-situ grown ZnO nanowires (ZnO nws ) were realized by a direct freeze-drying and hydrothermal process. The unique structure not only effectively reduces agglomeration of RGO and the density of composites, but also makes great contributions to impedance match, dielectric loss and inner scattering, achieving enhanced microwave absorption performance. When RGO foam is 0.8 mg/mL, the ZnO nws /RGO foam/PDMS composite with 3.3 wt% absorber loading attains a minimum reflection loss value of −27.8 dB at 9.57 GHz with a thickness of 4.8 mm, and a wide effective absorption bandwidth of 4.2 GHz covering the whole X band (8.2–12.4 GHz). The fundamental microwave absorption mechanism of the composites is discussed. These results demonstrate a promising method to fabricate an economical, lightweight, broadband and highly efficient microwave absorption material.

Ti3C2Tx MXenes modified with in situ grown carbon nanotubes (CNTs) are fabricated via a simple catalytic chemical vapor deposition (CVD) process. The as-prepared Ti3C2Tx/CNT nanocomposites show that one-dimensional (1D) carbon nanotubes are uniformly distributed in the interlayers of two-dimensional (2D) Ti3C2Tx MXene flakes. Compared with the pristine Ti3C2Tx MXenes, the hierarchical sandwich microstructure makes a contribution to the excellent electromagnetic wave absorption performance in the frequency range of 2–18 GHz, including higher absorption intensity (the minimum reflection coefficient reaches −52.9 dB, ∼99.999% absorption), broader effective absorption bandwidth (4.46 GHz), lower filler loading (35 wt%) and thinner thickness (only 1.55 mm). In addition, with the adjustment of thickness from 1.55 to 5 mm, the effective absorption bandwidth can reach up to 14.54 GHz (3.46–18 GHz). Different absorption mechanisms mainly based on polarization behaviors and conductivity loss are discussed. This work not only proposes the design of a novel electromagnetic wave absorber, but also provides an effective route for extending further the applications of 2D MXene materials in the field of electromagnetic wave absorption.

Herein, Ti2CTx MXene and its derivatives with various heterogeneous structures were constructed via etching and a facile oxidation treatment. The effect of different oxidation conditions on their structural evolution and phase composition was studied in detail. Compared with that of pristine Ti2CTx MXene, the improvement in the electromagnetic wave absorption capability of the as-prepared Ti2CTx/TiO2 and C/TiO2 nanocomposites was attributed to their enhanced polarization loss and stronger conductivity loss. The enhanced polarization loss is caused by the generated heterogeneous interfaces and higher specific surface area, and the stronger conductivity loss is due to the completely exfoliated carbon layers. Additionally, the remaining multilayered structure after exfoliation of the carbon layers favors energy dissipation. The C/TiO2 nanocomposites attain a minimum reflection coefficient of −50.3 dB at 7.1 and 14.2 GHz, and an effective absorption bandwidth of 4.7 GHz (covering the whole X-band) with a matching thickness of 2.1 mm; this indicates their excellent electromagnetic wave absorption properties. We believe that these nanocomposites with a heterogeneous structure also hold great promise for application in the fields of photocatalysis, lithium batteries, water purification, etc.

Clinical experience suggests increased incidences of neonatal jaundice when air quality worsens, yet no studies have quantified this relationship. Here we reports investigations in 25,782 newborns showing an increase in newborn’s bilirubin levels, the indicator of neonatal jaundice risk, by 0.076 (95% CI: 0.027–0.125), 0.029 (0.014–0.044) and 0.009 (95% CI: 0.002–0.016) mg/dL per μg/m3 for PM2.5 exposure in the concentration ranges of 10–35, 35–75 and 75–200 μg/m3, respectively. The response is 0.094 (0.077–0.111) and 0.161 (0.07–0.252) mg/dL per μg/m3 for SO2 exposure at 10–15 and above 15 μg/m3, respectively, and 0.351 (0.314–0.388) mg/dL per mg/m3 for CO exposure. Bilirubin levels increase linearly with exposure time between 0 and 48 h. Positive relationship between maternal exposure and newborn bilirubin level is also quantitated. The jaundice−pollution relationship is not affected by top-of-atmosphere incident solar irradiance and atmospheric visibility. Improving air quality may therefore be key to lowering the neonatal jaundice risk., Air pollution has become a major health risk in China. Here Zhang et al. report that maternal and neonatal exposure to particulate matter increases the risk of neonatal jaundice based on the study of 25,782 newborns born in China between 2014 and 2017.

Recently, debates on authenticity in the West and China have attracted attention of critical heritage studies. This paper aims to better understand how Western Authorized Heritage Discourse (AHD) influences local heritage practice in China. This paper employs observation, semi-structured interviews and textual analysis to examine how authenticity criteria in Western AHD has shaped perceptions on the spatial consequences of what is &ldquo, authentic&rdquo, by different agents in regards to the cultural heritage of the Shaolin Temple. It is argued that the implementation of authenticity criteria found in Western AHD influences Shaolin heritage practice both in hegemonic and negotiated ways, in which a Chinese AHD is formed through the creation of a Western AHD with Chinese characteristics. The understandings on authenticity criteria derived from Western AHD by Chinese heritage experts dominates Shaolin heritage practice, whilst the perceptions on &ldquo, Shaolin Temple cultural heritage attached closely to their emotions and experiences by local residents are neglected and excluded. The religiously based authenticity claims of the Shaolin monks which competes with those of the heritage experts and local residents are also considered. Furthermore, the managerial structure was changed in 2010 from a government-directed institution to a joint-venture partnership. The impacts of these managerial changes are also considered. The final outcome of these competing heritage claims was that local residents were relocated far from their original community. Without the residential community in situ, and in conjunction with the further commercialization of local culture, the Shaolin Temple heritage site takes on the features of a pseudo-classic theme park.