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Land resources are fundamentally important to human society, and their transition from one macroscopic state to another is a vital driving force of environment and climate change locally and globally. Thus, many efforts have been devoted to the simulations of land changes. Among all spatially explicit simulation models, CLUMondo is the only one that simulates land changes by incorporating the multifunctionality of a land system and allows the establishment of many-to-many demand–supply relationships. In this study, we first investigated the source code of CLUMondo, providing a complete, detailed mechanism of this model. We found that the featured function of CLUMondo—balancing demands and supplies in a many-to-many mode—relies on a parameter called conversion order. The setting of this parameter is a manual process and requires expert knowledge, which is not feasible for users without an understanding of the whole, detailed mechanism. Therefore, the second contribution of this study is the development of an automatic method for adaptively determining conversion orders. Comparative experiments demonstrated the validity and effectiveness of the proposed automated method. We revised the source code of CLUMondo to incorporate the proposed automated method, resulting in CLUMondo-BNU v1.0. This study facilitates the application of CLUMondo and helps to exploit its full potential.

To protect military broadcasting against both hostile interference and eavesdropping, an artificial noise (AN) sheltered frequency hopping (FH) broadcasting (ANS-FHB) architecture is proposed in this paper, and the secrecy capacity is employed to measure its secrecy performance. Besides, considering the inevitable frequency mismatch after synchronization will degrade system secrecy in practical applications, the optimal transmitting power allocation (PA) for the confidential information (CI) and AN is provided to maximize secrecy capacity in presence of frequency mismatch. Moreover, to be adapted to various application scenarios, the proposed optimal PA scheme is further simplified according to the frequency synchronization ability and relative channel quality. The analysis and simulations show that the proposed ANS-FHB system can achieve a non-negative secrecy rate even when existing multiple eavesdroppers. In addition, the optimal power ratio of AN to CI shows a downward trend from one to zero as frequency mismatch increases to mitigate the secrecy loss.

Here, we built a setup that can optically trap single microcrystals (MCs) in solution, and determine the time-resolved multiband upconversion luminescence at a nanosecond timescale.

In the flame spray pyrolysis process, 2-ethylhexanoic acid manipulates morphology of Yb3+/Ho3+ co-doped Y2O3 upconversion nanoparticles towards homogeneous and ultrafine but causing upconversion luminescence quenching and thermal sensitivity lowering.

Sandwich-type CoSe2-CNWs@rGO/S cathodes were constructed to maximize sulfur utilization, limit sulfur agglomeration, and endure volume expansion during cycling.

The evaluation of the arable land ecosystem services capacity and arable land use intensity is important for recognizing regional key factors that impact the change of arable land attributes. A chronic lack of cooperation persists between these two fields of study, which makes providing sufficient information to support developing arable land use management and control policies difficult. In this study, the clustering characteristics of four arable land quality indexes have been assessed using the K-means algorithm to indicate the regional coordination between arable land resource protection and arable land use. The clustering results have been visualized using circular cartogram. This study can contribute to the identification of key regional challenges in China's arable land use and help to build the framework of other countries’ arable land protection policies.

In this work, we demonstrate that readily available conjugated bis-aryl cyclobutenones undergo photoelectrocyclization reactions to give the corresponding dihydrophenanthrene cyclobutanones when exposed to 350 nm light, TFA, and TMSCl. We have also found that cyclobutenone electrocyclizations and cycloreversions are in equilibrium.

Sustainable development is the theme of the 21st century. To monitor the progress of sustainable development, the United Nations launched Sustainable Development Goals (SDGs) in 2015. Subsequently, nations of the world have drawn up a list of localized indicators regarding the United Nations SDGs as a paradigm. We established a database including SDGs indicator systems of 11 economies by collecting and determining a large number of materials. Based on this database, we analyzed SDGs indicators by designing a conceptual framework of comparative analysis that included three views. We found that the SDGs indicator systems of 11 economies are different between the number of indicators, the proportion of different categories, and the connotation of indicators. Although the SDGs indicator systems among economies regarded the United Nations SDGs as a framework and included the major social problems related to sustainability, the inconsistency between SDGs indicator systems is large. It is a major reason why scholars lack the systematic method for developing indicators. There are challenges faced in data accessibility. The framework for comparative analysis could be applied to different economies.

Although lithium-sulfur batteries (LSBs) are very promising in energy storage devices, their low conductivity, shuttle effect, and volume expansion unfavorably lead to sluggish kinetics and worsening electrochemical performance. To address these problems, we firstly prepared conductive carbon nanowires embedded with lithiophilic CoSe

To further protect frequency-hopping (FH) systems against severe wiretapping, an architecture of artificial noise (AN) shielded FH systems (ANS-FH) is proposed, wherein an AN cancellation architecture is utilized at the authorized receiver, and the secrecy performance is analyzed in the presence of an eavesdropper. First, an inter-frequency interference (IFI) model is employed to depict the residual AN after AN cancellation. Then, the tolerable range of frequency deviation is given, and the signal to AN plus noise ratio (SANR) is provided to measure the AN cancellation performance. Finally, the secrecy performance is analyzed using secrecy capacity under the assumption that frequency deviation is uniformly distributed within frequency synchronization accuracy. Theoretical and simulation results confirm that frequency deviation in practical FH systems will degrade both AN cancellation and system secrecy performance, and shorter hop length or proper power allocation for secret data and AN can mitigate the negative impact of frequency deviation, which in turn guides the practical transceiver design.

Quantitative assessment and visual analysis of the multidimensional features of international bilateral product trade are crucial for global trade research. However, current methods face poor salience and expression issues when analysing the characteristics of China—Australia bilateral trade from 1998 to 2019. To address this, we propose a new perspective that involves period division, feature extraction, construction of product space, and spatiotemporal analysis by selecting the display competitive advantage index using the digital trade feature map (DTFM) method. Our results reveal that the distribution of product importance in China—Australia bilateral trade is heavy-tailed, and that the number of essential products has decreased by 68% over time. The proportion of products in which China dominates increased from 71% to 77%. Furthermore, Australia consistently maintains dominance in the most crucial development in trade, and the supremacy of the head product is becoming stronger. Based on these findings, the stability of bilateral trade between Australia and China is declining, and the pattern of polarisation in the importance of traded products is worsening. This paper proposes a novel method for studying Sino—Australian trade support. The analytical approach presented can be extended to analyse the features of bilateral trade between other countries.

In physical layer security, imperfect time synchronization results in random mismatch between the received cooperative jamming (CJ) and the reconstructed CJ, leading to performance degradation of CJ cancellation at the authorized receiver. In this letter, the CJ cancellation performance with imperfect time synchronization is analyzed and evaluated by jamming cancellation ratio (JCR). Then, by assuming that the timing error is uniformly distributed within the synchronization accuracy, the expectation and cumulative distribution function (CDF) of JCR are provided. Experimental results confirm the theoretical analysis that imperfect time synchronization causes dramatic performance degradation of CJ cancellation, especially for high jamming-to-noise ratio (JNR).

Exploiting the optical/magnetic bifunctional upconversion nanoparticles (UCNPs) with small size has become a trend in the high-resolution biological imaging. Here, we report the simultaneous size manipulation and color tuning in Er3+-sensitized perovskite KZnF3 UCNPs via Mn2+ doping. It was found that the introduction of Mn2+ into the KZnF3 host matrix facilitates the reduction of the nanoparticle size (from 1 μm to 50 nm). Under the excitation of both 980 and 808 nm continuous wave (CW) laser, these KZnF3:Er3+/Mn2+ (1/x mol%) UCNPs can efficiently generate tunable upconversion luminescence (UCL) and achieve pure red UCL as the Mn2+ concentration reaches 30 mol%. It is suggested that the energy transfer (ET) processes between Er3+ and Mn2+ ions contribute to the single-band red UC emission, which was well supported by investigating the dependence of UCL intensity on the pump power and the decay lifetimes of 4S3/2 and 4F9/2 states of Er3+ ions. In addition, the KZnF3:Er3+/Mn2+ UCNPs have been used as the T1-weighted magnetic resonance imaging (MRI) agents, which exhibits a high optical contrast with the background. These features make the KZnF3:Er3+/Mn2+ UCNPs promising for excellent dual-modal agents in UCL imaging and MRI.

The development of trade research plays an important role in enhancing the understanding of the trade relationship structure, evolution and relevant driving factors. While there is little research on analyzing and visualizing bilateral trade patterns and the evolution of numerous kinds of commodities. In this paper, we respectively calculate revealed comparative advantage index (RCAI) of each traded commodity of China and USA in 2017. Then the RCAI of thousands of commodities have been mapped to a two-dimensional space and visualized in a grid system by using digital trade feature map method. On that basis, bivariate local spatial auto-correlation features between China – USA have been comprehensively depicted.

In single-input multi-output (SIMO) systems, imperfect time alignments result in random mismatch among the signals at receiving antennas, leading to performance degradation of maximum ratio combining (MRC). In this letter, by considering the timing errors at each receiving antenna, the closed-form expression of output signal-to-noise ratio (SNR) after performing MRC is calculated, and its statistical properties are investigated. Theoretical and simulation results show that the imperfect time alignment significantly degrades the output SNR, especially for high input SNR and large-scale receiving antennas. In addition, the system outage probability increases as the timing error increases or the number of receiving antennas decreases.

United Nations outlined 17 Sustainable Development Goals (SDGs), but at the current rate of progress most will not be achieved within the desired timeframe. Since a third of SDGs are directly related to land resources, it is crucial to improve the effectiveness and efficiency of land-use planning. In that regard, there is particular value in algorithmically optimizing land-use planning to better support sustainability. An ideal tool for such optimizations is the nondominated sorting genetic algorithm II (NSGA-II). Improved versions of NSGA-II have been actively developed for land-use problems, but no thorough evaluations and very few comparative studies have been performed. Thus, the objective is to conduct a thorough evaluation of and a systematic comparison between improved NSGA-II algorithms for sustainable land-use optimization. We identified both the most popular and the latest improved algorithms. A theoretical comparison was first made between them in terms of initialization, crossover, mutation, and archiving strategy. Then, a framework consisting of four hierarchal levels (principle, macro-criteria, micro-criteria, and indicators) was developed and applied to make a comprehensive comparison through experiments. The most popular algorithm was demonstrated to produce high-quality results and be computationally efficient, whereas the other performs better in the diversity of results, space efficiency, and the degree of optimization. Both algorithms exhibited excellent performance in handling constraints. Possible approaches to further improve the algorithms include borrowing ideas of scale optimization and gene flow. The proposed framework is capable of guiding further improvement by developers and algorithm selection by users.

Large amounts of data accumulated in ecology and related environmental sciences arouses urgent need to explore useful patterns and information in it. Here we propose coclustering-based methods and a temperatures-photoperiod driven phenological model to explore spatio-temporal differentiation in long-term spring phenology in China. First, we created the first bloom date (FBD) dataset in China from 1979 to 2018 using the extended spring indices and China Meteorological Forcing Dataset. Then we analyzed the dataset using Bregman block average co-clustering algorithm with I-divergence (BBAC_I) and kmeans algorithm. Such analysis delineated the spatially-continuous phenoregions in China for the first time. Results showed three spatial patterns of FBD in China and their temporal dynamics for 40 years (1979–2018). More specifically, overall late spring onsets occur in 1979–1996, in which areas located in Jiangxi, northern Xinjiang and middle Inner Mongolia experienced constant changing spring onsets. Overall increasingly earlier spring onsets occur in 1997–2012, in which areas located in Fujian, Hunan and eastern Heilongjiang experienced the most variable spring onsets. Stable early spring onsets over China occur after 2012. Results also showed 15 temporal patterns of spring phenology over the study period and their spatial delineation in China. More specifically, most areas in China have the same FBD category for 40 years while northern Guizhou, Hunan and southern Hubei have the same category in 1979–1997 and then fluctuate between different categories. Finally, our results have certain directive significance on the design of existing observational sites in Chinese Phenological Network.

Outlined here are studies exploring the scope of the sequential photoelectrocyclization, [1,5]-hydride shift of conjugated bis-aryl cycloalkenone substrates. We have found not only that the cyclization precursors can be synthesized in a modular fashion but also that the cyclization is efficient and amenable to the presence of a range of cycloalkenones and aromatic systems. Among the interesting discoveries from this work is that the electrocyclization intermediate can be competitively captured with protons and that the nature of the excited state (singlet vs triplet) is dependent on aromatic substitution.

Even though many studies have shown the usefulness of clustering for the exploration of spatio-temporal patterns, until now there is no systematic description of clustering methods for geo-referenced time series (GTS) classified as one-way clustering, co-clustering and tri-clustering methods. Moreover, the selection of a suitable clustering method for a given dataset and task remains to be a challenge. Therefore, we present an overview of existing clustering methods for GTS, using the aforementioned classification, and compare different methods to provide suggestions for the selection of appropriate methods. For this purpose, we define a taxonomy of clustering-related geographical questions and compare the clustering methods by using representative algorithms and a case study dataset. Our results indicate that tri-clustering methods are more powerful in exploring complex patterns at the cost of additional computational effort, whereas one-way clustering and co-clustering methods yield less complex patterns and require less running time. However, the selection of the most suitable method should depend on the data type, research questions, computational complexity, and the availability of the methods. Finally, the described classification can include novel clustering methods, thereby enabling the exploration of more complex spatio-temporal patterns.

In this article, a segmented self-interference cancellation (SSIC) method is proposed for frequency-modulated continuous-wave phased-array radar for canceling wideband multipath self-interference (SI) signals. A radio frequency canceller based on the SSIC method that uses the time-frequency segmentation equivalence of the linear frequency-modulated (LFM) signal is designed that can convert wideband SI cancellation (SIC) into several narrowband SICs. Numerical and simulation results show that the proposed method can achieve better cancellation performance with lower hardware complexity than the conventional multi-tap SI cancellation (MTSIC) method. Furthermore, the superior performance of the SSIC method is verified by experiments with a 250 MHz LFM signal.

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.