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• A framework for analyzing the urban LWE nexus based on modified SWF is posed. • Changes of SWF and contributions of final demand to local SWF are assessed. • North China is the primary net scare LWE exporter to Beijing. • Water-Energy emerge as the most frequent nodes in the identified local nexus. • Three-node (LWE) nexus becomes stronger and more common in tele-connected systems. Urbanization and economic growth together exacerbate land, water and energy (LWE) resource scarcities and demand-supply conflicts in global cities. In highly urbanized regions like the megacity Beijing, these challenges induce changes of the cross-regional LWE nexus in key resource nodes and strength. This study presents an integrated model that combines the multi-regional input-output model with modified scarcity-weighted and nexus node-strength indicators to better understand this phenomenon. The results highlight the central role water plays within the urban LWE nexus, despite a 61.3 % decrease in its scarcity-weighted footprint from 2007 to 2017. In the local context, over half of economic sectors exhibit a two-node nexus pattern, with the water-energy nexus being particularly prominent. Regarding the tele-connection pattern, the three-node nexus is the most common type with higher strength. The spatial distribution of provinces with three-node nexus has shifted from the northeast and neighboring provinces of Beijing in 2007 to the central region in 2017. Moving forward, prioritizing changes in consumption patterns, diversifying supply sources, improving resource use efficiency, and optimizing industrial and regional trade structures are crucial for regional sustainable development. These findings provide valuable insights for formulating effective solutions to address demand-supply conflicts for cities from a broader nexus perspective. [Display omitted] [ABSTRACT FROM AUTHOR]

• ENA was employed to study urban resilience based on an integrated FEW network model;. • Features of FEW network in topological structure and system function were analyzed;. • FEW metabolize in the chain-form, tree-form and loop-form organization respectively;. • Water network presents higher stability and better adaptability to disturbances;. • Megacities like Beijing should look upon FEW heterogeneities in resilience building;. Increasing resource crises force cities to scrutinize resilience status of urban food-energy-water (FEW) nexus system, which is highly depend on their metabolic processes. Taking Megacity Beijing as the case, we developed an ecological network model to explore structural and functional characteristics of urban FEW metabolic systems, with consideration of local availability, cross-region supply and resource nexus. The results show that the metabolism of food, energy and water exhibits different topological structures, and water presents typical loop network structure with APL and FCI values of 3.02 and 0.08 respectively, while food metabolizes in a loose topology and energy suffers dissipative losses in a uniflow form. This makes water metabolic network a robust organization with greater circulation, higher stability index (1.81) and better adaptive capacity to counter to vulnerability, yet energy network performs poorly for lacking redundancy and food network is more sensitive to changing conditions. Our findings enable decision-makers to find opportunities to build a more resilient city via improving FEW metabolic network synergistically, such as strengthening local resource reserves to provide buffering capacity when external supplies fail, as well as enhancing utilization efficiency of dominant industries and promoting treatment and reuse to make continuous survival and prosperity possible. [ABSTRACT FROM AUTHOR]

To ensure food, energy, and water (FEW) security in urban areas with high-density populations and concentrated social economic activities, it is imperative to build a better understanding of the dynamics of urban FEW systems. Using the STELLA platform, a system dynamics model named the BJ-FEW was developed by incorporating both the production and consumption sides of FEW systems into a single system-of-system model that considered the interactions between the FEW sectors within and beyond the urban economic system. This model was run for the megacity of Beijing over the period from 2000 to 2050 to simulate changes in the FEW demand and supply. Results showed that Beijing City will face an increasing challenge of FEW resource security with regard to the enlarging gap between the total demands and the local provision capability. Under the baseline scenario without policy intervention, the total demand for food, energy, and water in Beijing will incredibly reach 10 Mt, 129 Mtce, and 6.4 Bm3 in 2050. In such case, it was estimated that 75% of food, 88% of energy, and 48% of water will depend on trans-boundary imports. The implement of Xiong'an New Area Plan will be the indispensable development pathway to alleviate resource pressure in Beijing. The scenario analysis verified the positive effect of such program, which will improve the status of the resource system by reducing 15%, 29%, and 34% of the supply-demand gap for food, energy, and water. The results highlighted the necessity of a regional coordinated management strategy to build a more resilient FEW provision system. [Display omitted] • BJ-FEW model was developed to simulate dynamics of urban FEW resource security. • Interactions between the FEW sectors within and beyond the city were considered. • Megacities like Beijing will face an increasing challenge of FEW resource supply. • Urban nexus network is reorganizing to a larger scale and showing more trade-offs. • Integrated management strategy is needed to build a resilient FEW provision system. [ABSTRACT FROM AUTHOR]

This work integrates functional gradient constraint into multi-material topology optimization for transient heat conduction structure, taking into account the use of ordered rational approximation of material properties to represent the multi-material interpolation model. The optimization objectives modeled by the aggregation function are to minimize the maximum responses of the transient heat conduction structure during the whole working time. Furthermore, the functional gradient layers are achieved by dividing the design domain into several periodic sub-domains and redistributing the average element response. A numerical example is illustrated to verify the validity and applicability of the proposed method. The results demonstrate that the functional gradient of multi-material topology optimization design can be obtained with various combinations of sub-regions numbers. Simultaneously, different types of optimization functions exhibit distinct topologies under additional heat loading times. [ABSTRACT FROM AUTHOR]

Landfast ice is an important component of the Antarctic sea ice regime. It affects the Antarctic climate and ecological system. In this study, the first high-resolution, long time series of the landfast ice edge from 2006 to 2011 and 2016 to 2017 is presented. The dataset was produced based on the improved net gradient difference algorithm using 2470 SAR scenes from ENVISAT and Sentinel-1A/B as well as manual analysis of MODIS imagery to fill in SAR data gaps. The study results show that the landfast ice area in November for all studied years was approximately 49.49 ± 3.25 × 104 km2, accounting for about 3%–4% of the total Antarctic sea ice area. The maximum area was 55.70 × 104 km2 in November 2007, compared to the minimum area 44.01 × 104 km2 in 2011. The area in West Antarctica was about 40% of that in East Antarctica. The distribution of landfast ice in Antarctica has significant regional differences. The extent in the Indian Ocean sector is the maximum with a mean value of 16.49 ± 1.1 × 104 km2; however, the ratio of the landfast ice area to the sea ice area in the Pacific Ocean sector is the highest. Twenty-four landfast ice zones with groups of small, grounded icebergs were identified, most of which were located in East Antarctica, particularly along the Wilkes Land and Oates Land. Two cases are presented to illustrate how giant, grounded icebergs affected landfast ice. Results from this study are well suited to underpin the Antarctic climate or ecological system studies. • The first long time series and high-resolution circumpolar mapping of the landfast ice in Antarctica • The spatio-temporal patterns of the landfast ice in Antarctica have been revealed. • The interactions between landfast ice and giant icebergs are analyzed in two specific cases. [ABSTRACT FROM AUTHOR]

• A fail-safe topology optimization is presented for multiscale structures. • The damage in both the macroscale and microscale is considered. • Simplified damage models for truss-like microstructures are utilized. • The use of Heaviside projection speeds up convergence and obtains better results. • Multiscale fail-safe structures are more damage-resistant and self-supporting. This paper presents a novel fail-safe topology optimization method for multiscale structures. The partial damage of both macroscopic and microscopic scales is considered for structural design. To ensure precision, the effective elasticity tensor obtained by the homogenization method is fitted as a high-order polynomial function. Meanwhile, the simplified models of partially damaged truss-like microstructure are employed to reduce the computational cost and the difficulty of fitting. Moreover, Heaviside projection is applied to speed up the convergence and yield a relatively clear configuration. Three numerical examples are tested to demonstrate that the optimized multiscale structures successfully obtain comprehensive performances than optimized solid structures when appropriate microstructure configurations are chosen. Besides, multiscale structures are more self-supporting than solid structures and thus more suitable for additive manufacturing due to the large number of gray elements diffused. [ABSTRACT FROM AUTHOR]

The geographical mismatch between water availability and demand further exacerbates the challenge of the water-energy-food nexus in China. This study characterizes competing water uses for crops and energy to reveal their resulting impacts on regional inequality by integrating the modified Gini coefficient and unbalanced index with respect to water scarcity and water surplus. From 2000–2019, China's food production decreased by 2.3 % in the blue water footprint (ranging from −90.3 % to 71.7 % for specific provinces), while the energy sector increased by 111.9 % (varying from −69.9 % to 692.4 %). The energy sector showed greater inequality in blue water consumption verses available water, with the Gini coefficient ranged from 0.43 to 0.62, while the food-water nexus maintained a relatively stable value of approximately 0.35. Spatially, there was consistent water scarcity inequality in the north and water surplus inequality in the south for both the food-water and the energy-water nexus. Overall, the energy-water nexus exhibited larger variations in provincial inequalities. This divergent evolving inequality was primarily caused by a combination of factors that included resource endowments, regional economic disparities, and government interventions. These findings can inform policy makers towards optimizing the management of water-energy-food resources. • Water-energy-food nexus is assessed based on water scarcity-surplus. • Energy-water nexus shows greater inequality and spatio-temporal variations. • Inequalities of water scarcity and surplus occur in North and South, respectively. • The inequality is a result of resource endowments, economic disparities, and policies. [ABSTRACT FROM AUTHOR]

• The land use of Xixi wetland region has experienced substantial changes during 1984–2018. • While CS presented an increasing trend, the changes of other services illustrated the overall degradation. • Redundancy analysis revealed the detrimental impacts of impervious cover on the provision of ESs. • Much more efforts need to be taken to enhance the overall services capability of Xixi wetland region. Although extensive studies have investigated changes in regional ecosystem services (ESs) under rapid urbanization, few analyses have used high-resolution image data to investigate urban wetlands. Taking the Xixi wetland region as a case area, this study aimed to investigate the temporal and spatial variation and influencing factors of typical ESs during 1984–2018 using high-resolution images. The results showed that the Xixi wetland region underwent substantial changes of land use as well as in different ESs. While carbon storage presented an increasing trend from 223.25 t/ha to 368.11 t/ha from 1984 to 2018, the changes of other services illustrated an overall degradation in this important urban wetland. Evident trade-off and synergy effects were observed between water yield and carbon storage and between biodiversity protection and recreation and cultural services. Redundancy analysis revealed the detrimental impacts of impervious cover on the provision of ESs in this urban wetland area. The results obtained in this study highlight the great challenges that urban wetland parks face in balancing wetland conservation and sustainable use. [ABSTRACT FROM AUTHOR]