•The landscape was characterized by fragmented patches, complex shapes, diversified types and uniform distribution over time.•Habitat quality (HQ) showed a declining trend during 1990–2020.•There is ...significant correlation between habitat quality and land use changes.•Areas with human-dominated land-use modifies like urban sprawl tended to have low HQ.
Landscape patterns have a large impact on biodiversity in ecosystems. As a proxy for biodiversity research, assessing changes in habitat quality (HQ) induced by land-use/land-cover (LULC) changes will provide a scientific foundation for ecological protection and land resource management, especially in the ecologically fragile regions such as mountainous areas. Based on land-use data covering the period from 1990 to 2020 from the Taihang Mountains of Hebei Province, this paper selected 10 landscape metrics at the class and landscape levels to examine the dynamics of LULC. Then, this study evaluated HQ by employing the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model and quantitatively analyzed the impact of land use changes on HQ using a geographically weighted regression (GWR) model. The results showed that arable land, grassland and forestland were the main land categories in the study area, and the major changes were the conversion of arable land and grassland to construction land during 1990–2020. During the research period, landscape patches tended to fragment, shape complexity and varied and were evenly distributed. Overall, the region had a high HQ, but the average HQ has exhibited a declining trend in the past 30 years. In addition, changes in HQ were significantly related to land-use changes, and the areas dominated by construction land or arable land, which were closely related to anthropogenic activities, had a relatively low HQ. To balance the tradeoff between economic development and ecological integrity, a social-ecological systems perspective is needed in the design of political-economic policies. This research could improve our understanding of the effects of land-use pattern dynamics on HQ, which has important significance in preserving biodiversity, safeguarding ecological security, and achieving the sustainability of the ecological environment.
The urban-rural transformation from dichotomy to integration is a gradual process. Like rural areas in many countries, Chinese rural society is experiencing a decline in all spheres due to ...depopulation, aging, lack of economic opportunity, and so on. Aiming at solving the serious rural issues, China proposed the implementation of a rural revitalization strategy and the promotion of an integrated urban-rural development for the first time in 2017. This proposal marks the transformation of the urban-rural relationship, and the integrated urban-rural development reflects a significant conceptual change. Researches on issues of rural decline are urgently needed to determine the most effective method for rural revitalization and development from the perspective of the urban-rural dynamics. In this context, this paper focuses on studying the theory, technology and management of rural revitalization and development. We construct a theoretical framework for urban-rural integration based on population-land-industry-right between the urban and rural systems, regarding land engineering for land capacity building as the technical support and the rural land system reform and reconstruction as the policy support for management. This research will provide theoretical support for the implementation of China’s rural revitalization strategy.
•The identification and intensity diagnosis model of land use function conflict is built.•The spatial characteristic of ecological, production and living function land are different.•The conflict ...zone is divided into 8 types, and conflict intensity is divided into 4 stages.•The whole study area is basically at risk of potential land use conflicts.
The rapid advancement of urbanization and industrialization has led to the continuous strengthening of multi-functionality of land use. The overlapping, crowding, agglomeration and transformation of various land use functions suggested that there would be fierce competition and conflicts. Based on the widely recognized “ecological-production-living” perspective of sustainable development in the world, we constructed the spatial identification and intensity diagnosis model of potential land use function conflicts (LUFCs), and selected Nan’an City, a typical coastal city in southeast China, as an empirical analysis. On the level of theoretical building, the LUFCs were divided into eight types, the conflict intensity was divided into four stages, and a land use conflict risk index (LUCRI) was constructed to characterize the possibility of potential conflict, which was divided into four ranks. Empirical research showed that the spatial concentration characteristic of ecological function of land use in Nan’an City was not significant and was poor spatial connectivity, while the gradient and band feature of production function was significant and was good spatial connectivity, and living function have formed three core clusters. The controllable conflict zones gathered and formed cold spots in high altitude forest areas, as well as the out-of-control conflict zones gathering and forming hot spots in concentrated areas of social and economic activities. The area proportions of different conflict types respectively were 1.79%, 18.07%, 23.17%, 13.49%, 8.00%, 13.66%, 20.34% and 1.49%. The whole study area was basically at risk of potential conflicts, with the area proportions accounting for 55.28%, 30.19%, 12.30% and 2.23%. Different governance strategies should be adopted according to the spatial distribution, manifestation and conflict degree. The model and index constructed in this paper could accurately reflect the actual situation of land use in fast-growing areas, which would provide reference for land space planning and management.
Developing untethered millirobots that can adapt to harsh environments with high locomotion efficiency is of interest for emerging applications in various industrial and biomedical settings. Despite ...recent success in exploiting soft materials to impart sophisticated functions which are not available in conventional rigid robotics, it remains challenging to achieve superior performances in both wet and dry conditions. Inspired by the flexible, soft, and elastic leg/foot structures of many living organisms, here we report an untethered soft millirobot decorated with multiple tapered soft feet architecture. Such robot design yields superior adaptivity to various harsh environments with ultrafast locomotion speed (>40 limb length/s), ultra-strong carrying capacity (>100 own weight), and excellent obstacle-crossing ability (stand up 90° and across obstacle >10 body height). Our work represents an important advance in the emerging area of bio-inspired robotics and will find a wide spectrum of applications.
•An indicator system was established to measure urban-rural transformation from the perspective of population-land-industry.•Urban-rural transformation development was divided into four ...categories.•Spatio-temporal variations and internal mechanisms of BTH’s urban-rural coordinated transformation were captured.
Since the turn of the new millennium, urban-rural transformation has entered a critical period. Ever-widening gaps between urban and rural areas are common in most parts of China. The Beijing-Tianjin-Hebei (BTH) region, as the capital circle of China, has experienced significant urban-rural transformation with accelerated urbanization. On the basis of space analytic geometry, this study measures BTH’s urban-rural transformation by establishing an indicator system from the population-land-industry perspective to capture spatio-temporal variations and explore the internal mechanisms of BTH's urban-rural transformation. The results indicate that the urban-rural system in the BTH region has undergone an intensive and dramatic transformation during 2000–2015. Evolving from basic to advanced and from disorder to order, urban districts in Beijing and Tianjin have always had levels of coordinated transformation degrees (CTD) higher than those of the surrounding high-level counties while the overall coordinated deviation degree (CDD) has exhibited a decreasing trend over time. Four functional zones, which are dominant transition area, key transition area, potential transition area and restricted transition area, of urban-rural transformation were established by adopting the trajectory computing method. This research could track the development process of regional urban-rural change from the essence of an urban-rural system itself. When this indicator system that measures urban-rural transformation is applied in other countries, national differences such as differences in urban-rural structures, as well as the limitations, should be noted.
Mobile cloud computing (MCC) as an emerging and prospective computing paradigm, can significantly enhance computation capability and save energy of smart mobile devices (SMDs) by offloading ...computation-intensive tasks from resource-constrained SMDs onto the resource-rich cloud. However, how to achieve energy-efficient computation offloading under the hard constraint for application completion time remains a challenge issue. To address such a challenge, in this paper, we provide an energy-efficient dynamic offloading and resource scheduling (eDors) policy to reduce energy consumption and shorten application completion time. We first formulate the eDors problem into the energy-efficiency cost (EEC) minimization problem while satisfying the task-dependency requirements and the completion time deadline constraint. To solve the optimization problem, we then propose a distributed eDors algorithm consisting of three subalgorithms of computation offloading selection, clock frequency control and transmission power allocation. More importantly, we find that the computation offloading selection depends on not only the computing workload of a task, but also the maximum completion time of its immediate predecessors and the clock frequency and transmission power of the mobile device. Finally, our experimental results in a real testbed demonstrate that the eDors algorithm can effectively reduce the EEC by optimally adjusting the CPU clock frequency of SMDs based on the dynamic voltage and frequency scaling (DVFS) technique in local computing, and adapting the transmission power for the wireless channel conditions in cloud computing.
Plant species like the Venus flytrap possess unique abilities to intelligently respond to various external stimuli, ensuring successful prey capture. Their nerve-devoided structure provides valuable ...insights for exploring natural intelligence and constructing intelligent systems solely from materials, but limited knowledge is currently available and the engineering realization of such concept remains a significant challenge. Drawing upon the flytrap's action potential resulting from ion diffusion, we propose a signal accumulation/attenuation model and a corresponding liquid metal-based logic module, which operates on the basis of the shape change of liquid metal within a sodium hydroxide buffer solution. The module itself exhibits memory and counting properties without involving any other electronic components, intelligently responding to various stimulus sequences, and reproducing the flytrap's most logical function. We also demonstrate and forecast its potential as a moving window integration-based high-pass filter, artificial synapse in neural networks, and other related applications. This research provides a fresh perspective on comprehending the intelligence inherent in nature and its realization through physical structures, which is expected to inspire logic device development in a broad engineering field.
In this paper, we present a novel sensor deployment algorithm, called the adaptive triangular deployment (ATRI) algorithm, for large-scale unattended mobile sensor networks. The ATRI algorithm aims ...at maximizing coverage area and minimizing coverage gaps and overlaps by adjusting the deployment layout of nodes close to equilateral triangulation, which is proven to be the optimal layout to provide the maximum no-gap coverage. The algorithm only needs the location information of nearby nodes, thereby avoiding communication cost for exchanging global information. By dividing the transmission range into six sectors, each node adjusts the relative distance to its one-hop neighbors in each sector separately. The distance threshold strategy and the movement state diagram strategy are adopted to avoid the oscillation of nodes. The simulation results show that the ATRI algorithm achieves a much larger coverage area and smaller average moving distance of nodes than existing algorithms. We also show that the ATRI algorithm is applicable to practical environments and tasks such as working in both bounded and unbounded areas and avoiding irregularly shaped obstacles. In addition, the density of nodes can be adjusted adaptively to different requirements of tasks.
This paper considers applying simultaneous wireless information and power transfer (SWIPT) technique to cooperative clustered wireless sensor networks, where energy-constrained relay nodes harvest ...the ambient radio-frequency (RF) signal and use the harvested energy to forward the packets from sources to destinations. To this end, we first formulate the energy-efficient cooperative transmission (eCotrans) problem for SWIPT in clustered wireless sensor networks as a non-convex constrained optimization problem. Then, by exploiting fractional programming and dual decomposition, we develop a distributed iteration algorithm for power allocation, power splitting and relay selection to solve the non-convex optimization problem. We find that power splitting ratio plays an imperative role in relay selection. Our simulation results illustrate that the proposed algorithm can converge within a few iterations and the numerical analysis provides practical insights into the effect of various system parameters, such as the number of relay nodes, the inter-cluster distance and the maximum transmission power allowance, on energy efficiency and average harvested power.
In this paper, we propose a new data-gathering mechanism for large-scale wireless sensor networks by introducing mobility into the network. A mobile data collector, for convenience called an ...M-collector in this paper, could be a mobile robot or a vehicle equipped with a powerful transceiver and battery, working like a mobile base station and gathering data while moving through the field. An M-collector starts the data-gathering tour periodically from the static data sink, polls each sensor while traversing its transmission range, then directly collects data from the sensor in single-hop communications, and finally transports the data to the static sink. Since data packets are directly gathered without relays and collisions, the lifetime of sensors is expected to be prolonged. In this paper, we mainly focus on the problem of minimizing the length of each data-gathering tour and refer to this as the single-hop data-gathering problem (SHDGP). We first formalize the SHDGP into a mixed-integer program and then present a heuristic tour-planning algorithm for the case where a single M-collector is employed. For the applications with strict distance/time constraints, we consider utilizing multiple M-collectors and propose a data-gathering algorithm where multiple M-collectors traverse through several shorter subtours concurrently to satisfy the distance/time constraints. Our single-hop mobile data-gathering scheme can improve the scalability and balance the energy consumption among sensors. It can be used in both connected and disconnected networks. Simulation results demonstrate that the proposed data-gathering algorithm can greatly shorten the moving distance of the collectors compared with the covering line approximation algorithm and is close to the optimal algorithm for small networks. In addition, the proposed data-gathering scheme can significantly prolong the network lifetime compared with a network with static data sink or a network in which the mobile collector can only move along straight lines.
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