A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However...A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However,current studies primarily focus on short-term grain provision services while neglecting the spatiotemporal variations in grain flows across different scales.This gap limits the identification of dynamic matching relationships and the formulation of optimization strategies for balancing grain flows.This study examined the spatiotemporal evolution of grain supply and demand in the Beijing-Tianjin-Hebei(BTH)region from 1980 to 2020.Using the Enhanced TwoStep Floating Catchment Area method,the grain provision ecosystem service flows were quantified,the changes in supply–demand matching under different grain flow scenarios were analyzed and the optimal distance threshold for grain flows was investigated.The results revealed that grain production follows a spatial distribution pattern characterized by high levels in the southeast and low levels in the northwest.A significant mismatch exists between supply and demand,and it shows a scale effect.Deficit areas are mainly concentrated in the northwest,while surplus areas are mainly located in the central and southern regions.As the spatial scale increases,the ecosystem service supply–demand ratio(SDR)classification becomes more clustered,while it exhibits greater spatial SDR heterogeneity at smaller scales.This study examined two distinct scenarios of grain provision ecosystem service flow dynamics based on 100 and 200 km distance thresholds.The flow increased significantly,from 2.17 to 11.81million tons in the first scenario and from 2.41 to 12.37 million tons in the second scenario over nearly 40 years,forming a spatial movement pattern from the central and southern regions to the surrounding areas.Large flows were mainly concentrated in the interior of urban centers,with significant outflows between cities such as Baoding,Shijiazhuang,Xingtai,and Hengshui.At the county scale,supply–demand matching patterns remained consistent between the grain flows in the two scenarios.Notably,incorporating grain flow dynamics significantly reduced the number of grain-deficit areas compared to scenarios without grain flow.In 2020,grain-deficit counties decreased by28.79 and 37.88%,and cities by 12.50 and 25.0%under the two scenarios,respectively.Furthermore,the distance threshold for achieving optimal supply and demand matching at the county scale was longer than at the city scale in both grain flow scenarios.This study provides valuable insights into the dynamic relationships and heterogeneous patterns of grain matching,and expands the research perspective on grain and ecosystem service flows across various spatiotemporal scales.展开更多
Although wind energy is volatile,the output of a wind-storage plant is partially dispatchable,making it a promising paradigm on the generation side.A grid-friendly wind-storage plant ought to be able to continuously o...Although wind energy is volatile,the output of a wind-storage plant is partially dispatchable,making it a promising paradigm on the generation side.A grid-friendly wind-storage plant ought to be able to continuously output the desired power over a certain period of time.This paper proposes a dependable dynamic capacity provision scheme of a wind-storage plant over a daily horizon.It stipulates a minimum number of periods during which the committed capacity must be fulfilled and a maximum mismatch during the remaining periods when the desired power output is not achievable.In the general case,the day-ahead piecewise constant capacity provision results in a two-stage stochastic program formulated as a mixed-integer linear program.Specifically,for constant capacity provision,a decomposition algorithm is developed to determine the global optimal solution,and the complexity grows linearly with the number of scenarios.Given the committed capacity trajectory,the real-time operation problem is modeled as a four-state stochastic dynamic program.The discrete state-action values are derived recursively via the principle of optimality.Real-time dispatch actions are generated by using the action-value tabular leveraging inexact ultra-short-term forecasts.Numerical tests over one year demonstrate that the proposed method successfully fulfills reliable operation on 355 days and achieve an optimality gap of 9.47%compared with the ex-post optimum,which is comparable to model predictive control using exact 2–3-hour-ahead wind power forecasts.展开更多
Multiple-input multiple-output (MIMO) wireless communication systems can significantly improve the spectrum efficiency or transmission reliability through spatial multiplexing or diversity respectively.Most of previou...Multiple-input multiple-output (MIMO) wireless communication systems can significantly improve the spectrum efficiency or transmission reliability through spatial multiplexing or diversity respectively.Most of previous works mainly have focused on the multiplexing-diversity tradeoff or switching between multiplexing and diversity without considering the property of heterogeneous QoS provisioning.In this paper,switching between multiplexing and diversity in MIMO system with the heterogeneous QoS provisioning is studied.Firstly the QoS provisioning for users are classified into two classes:users with real time service requirement and users with non-real time service requirement respectively.Then based on the heterogeneous QoS Provisioning for users,two different switching criterions are proposed,switching based on the Euclidean distance for users with real time service to minimize the probability of symbol error and capacity-based switching criterion for users with non-real time service to maximize the transmission capacity respectively.Finally,numerical simulation results are illustrated to demonstrate the performance of proposed scheme.展开更多
Rhesus macaques(Macaca mulatta)have demonstrated a potent capability of adapting to human-disturbed environment.In China,they have become popular attractions in ecotourism areas and receive substantial food from touri...Rhesus macaques(Macaca mulatta)have demonstrated a potent capability of adapting to human-disturbed environment.In China,they have become popular attractions in ecotourism areas and receive substantial food from tourists,resulting in local booming populations.Previous studies have highlighted human-macaque conflicts and yet ignored their impact on local natural ecosystems.Through reviewing previous researches,we summarized the contributing factors to the thriving populations of rhesus macaque and expounded upon the potential impacts of them on other local organisms.Booming populations of rhesus macaque caused by provisioning could present potential risks to local plant and animal community through lesser seed dispersal and greater predation and competition pressures on other sympatric species,ultimately impacting the diversity and stability of local ecosystems.Thus,it is imperative to draft the relevant laws to strictly control human provisioning for wild rhesus macaques and conduct further studies to elucidate their interspecies relationships.And a higher priority should be devoted to monitoring these potentially overabundant populations and formulating optimal management strategies to achieve harmonious coexistence between humans and rhesus macaques.展开更多
Human well-being and livelihoods depend on natural ecosystem services(ESs).Following the increment of population,ESs have been deteriorated over time.Ultimately,land use/land cover(LULC)changes have a profound impact ...Human well-being and livelihoods depend on natural ecosystem services(ESs).Following the increment of population,ESs have been deteriorated over time.Ultimately,land use/land cover(LULC)changes have a profound impact on the change of ecosystem.The primary goal of this study is to determine the impacts of LULC changes on ecosystem service values(ESVs)in the upper Gilgel Abbay watershed,Ethiopia.Changes in LULC types were studied using three Landsat images representing 1986,2003,and 2021.The Landsat images were classified using a supervised image classification technique in Earth Resources Data Analysis System(ERDAS)Imagine 2014.We classified ESs in this study into four categories(including provisioning,regulating,supporting,and cultural services)based on global ES classification scheme.The adjusted ESV coefficient benefit approach was employed to measure the impacts of LULC changes on ESVs.Five LULC types were identified in this study,including cultivated land,forest,shrubland,grassland,and water body.The result revealed that the area of cultivated land accounted for 64.50%,71.50%,and 61.50%of the total area in 1986,2003,and 2021,respectively.The percentage of the total area covered by forest was 9.50%,5.90%,and 14.80%in 1986,2003,and 2021,respectively.Result revealed that the total ESV decreased from 7.42×10^(7) to 6.44×10^(7) USD between 1986 and 2003.This is due to the expansion of cultivated land at the expense of forest and shrubland.However,the total ESV increased from 6.44×10^(7) to 7.76×10^(7) USD during 2003-2021,because of the increment of forest and shrubland.The expansion of cultivated land and the reductions of forest and shrubland reduced most individual ESs during 1986-2003.Nevertheless,the increase in forest and shrubland at the expense of cultivated land enhanced many ESs during 2003-2021.Therefore,the findings suggest that appropriate land use practices should be scaled-up to sustainably maintain ESs.展开更多
Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountai...Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountainous landscapes remain poorly understood.Taking the Chinese Loess Plateau(LP)as an example,this study conducted multitemporal mapping of terraces and sloping croplands over three decades(1990-2020),systematically assessing their impacts on food output through terrain gradient analysis.The results indicated that:(1)the terraced area expanded in the past 30 years,particularly across steeper terrain gradients(third to fifth gradients);(2)sloping croplands predominantly occupied gentle slopes(first to second gradients),exhibiting area reduction correlating with urbanization processes;(3)the food provision increased extensively,with yield decreasing from southeast to northwest and regions of high yielding mainly in terraced fields;(4)over time,the variation of food provision correlated positively with the area of sloping cropland at low gradients,while at higher gradients,the expansion of terraces dominated the increase in food provision;(5)spatial clustering analysis revealed significant food productivity associated with high-density terrace distribution across steeper slope gradients.Low yields could be attributed to improper terrace management.This study clarified the impact of long-term terrace patterns on food provision and offered large-scale perspectives for terrace-based agriculture to enhance food security.Furthermore,the findings underscore the imperative of integrated land management in topographically complex regions,informing evidence-based policymaking for rational allocation and optimal utilization of terrace resources.展开更多
As the cornerstone of future information security,quantum key distribution(QKD)is evolving towards large-scale hybrid discrete-variable/continuous-variable(DV/CV)multi-domain quantum networks.Meanwhile,multicast-orien...As the cornerstone of future information security,quantum key distribution(QKD)is evolving towards large-scale hybrid discrete-variable/continuous-variable(DV/CV)multi-domain quantum networks.Meanwhile,multicast-oriented multi-party key negotiation is attracting increasing attention in quantum networks.However,the efficient key provision for multicast services over hybrid DV/CV multi-domain quantum networks remains challenging,due to the limited probability of service success and the inefficient utilization of key resources.Targeting these challenges,this study proposes two key-resource-aware multicast-oriented key provision strategies,namely the link distance-resource balanced key provision strategy and the maximum shared link key provision strategy.The proposed strategies are applicable to hybrid DV/CV multi-domain quantum networks,which are typically implemented by GG02-based intra-domain connections and BB84-based inter-domain connections.Furthermore,the multicast-oriented key provision model is formulated,based on which two heuristic algorithms are designed,i.e.,the shared link distance-resource(SLDR)dependent and the maximum shared link distance-resource(MSLDR)dependent multicast-oriented key provision algorithms.Simulation results verify the applicability of the designed algorithms across different multi-domain quantum networks,and demonstrate their superiority over the benchmark algorithms in terms of the success probability of multicast service requests,the number of shared links,and the key resource utilization.展开更多
Efficient resource provisioning,allocation,and computation offloading are critical to realizing lowlatency,scalable,and energy-efficient applications in cloud,fog,and edge computing.Despite its importance,integrating ...Efficient resource provisioning,allocation,and computation offloading are critical to realizing lowlatency,scalable,and energy-efficient applications in cloud,fog,and edge computing.Despite its importance,integrating Software Defined Networks(SDN)for enhancing resource orchestration,task scheduling,and traffic management remains a relatively underexplored area with significant innovation potential.This paper provides a comprehensive review of existing mechanisms,categorizing resource provisioning approaches into static,dynamic,and user-centric models,while examining applications across domains such as IoT,healthcare,and autonomous systems.The survey highlights challenges such as scalability,interoperability,and security in managing dynamic and heterogeneous infrastructures.This exclusive research evaluates how SDN enables adaptive policy-based handling of distributed resources through advanced orchestration processes.Furthermore,proposes future directions,including AI-driven optimization techniques and hybrid orchestrationmodels.By addressing these emerging opportunities,thiswork serves as a foundational reference for advancing resource management strategies in next-generation cloud,fog,and edge computing ecosystems.This survey concludes that SDN-enabled computing environments find essential guidance in addressing upcoming management opportunities.展开更多
笛卡尔在《谈谈方法》一书的第三部分中提出了一套道德准则,即morale par provision。最近,一些笛卡尔哲学的研究者们对这一概念提出了三种不同的解读。第一种解读是传统且主流的解读,主张将morale par provision理解为"临时的道德...笛卡尔在《谈谈方法》一书的第三部分中提出了一套道德准则,即morale par provision。最近,一些笛卡尔哲学的研究者们对这一概念提出了三种不同的解读。第一种解读是传统且主流的解读,主张将morale par provision理解为"临时的道德",它是笛卡尔为了保障自己或他人在贯彻"普遍的方法"的第一步"怀疑的方法"或"方法论怀疑"时所采取的一种权宜之计。第二种解读是将morale par provision理解为"先决的道德",强调这种道德的先决性与无条件性。第三种对morale par provision的解读是将之理解为"完美道德的一阶近似"。笛卡尔在《谈谈方法》一书中所做的"建筑的比喻"十分清楚地表明了他提出morale par provision的用意及其真正的含义,他将morale par provision比作为了实施房子重建计划而预先准备的临时的房子。因此,Morale par provision其实是笛卡尔为了保障自己或他人在贯彻"普遍的方法"的第一条准则时仍能够不影响日常生活所采纳的一种策略。在这个意义来说,将morale par provision译作"临时的道德"是合适的,换句话说,三种解读中的第一种解读有其合理的依据。《谈谈方法》是morale par provision的出处,因此它无疑是对这一表述进行解释所要依据的最重要的文本。另外两种解读尽管有其合理的地方且具有创新性,但是,只要它们无法强力地否定《谈谈方法》的文本证据,那么它们就无法真正地驳倒第一种解读。此外,关于morale par provision的另外两种解读的支持理由与证据也并非无懈可击。展开更多
Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or...Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or in segregated controlled airspace. As the industry progresses, both operational and technological capabilities have matured to the point where UASs are expected to gain greater freedom of access to both controlled and uncontrolled airspace. Extensive technical and regulatory surveys have been conducted to enable the expanded operations. However, most surveys are derived from the perspective of UAS own operating mechanism and barely consider interactions of their non-segregated activities with the Air Traffic Management(ATM) system. Hence, to fill the gap, this paper presents a survey conducted from the perspective of Air Navigation Service Provider(ANSP), which serves to accommodate these new entrants to the overall national airspace while continuing flight safety and efficiency. The primary objectives of this paper are to:(A) describe what typical ANSP-supplied UAS Traffic Management(UTM) architecture is required to facilitate all types of civil UAS operations;(B) identify three major ANSP considerations on how UAS can be accommodated safely in civil airspace;(C) outline future directions and challenges related with UAS operations for the ANSP.展开更多
With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircr...With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.展开更多
Global climate change and increased human consumption have aggravated the uneven spatiotemporal distribution of watershed water resources, affecting the water provision supply and demand state. However, this problem h...Global climate change and increased human consumption have aggravated the uneven spatiotemporal distribution of watershed water resources, affecting the water provision supply and demand state. However, this problem has often been ignored. The present study used the Xiangjiang River basin(XRB) as the study area, and the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST) model, demand quantification model,supply–demand ratio, and water flow formula were applied to explore the spatial heterogeneity, flow, and equilibrium between water supply and demand. The results demonstrated significant spatial heterogeneity in the upstream, midstream, and downstream regions.The areas of water shortage were mainly located the downstream of the Changsha–Zhuzhou–Xiangtan urban agglomeration, and the Hengyang basin was the most scarcity area. Affected by terrain gradients and human needs, water flow varied from-16.33 × 10^(8) m^(3) to 13.69 × 10^(8) m^(3)from the upstream to the downstream area, which provided a possibility to reduce spatial heterogeneity. In the future, measures such as strengthening water resource system control,sponge city construction, and dynamic monitoring technology should be taken to balance the supply and demand of water in different river sections of the basin. This study can provide references for regulating water resources allocation in different reaches of the basin.展开更多
The aim of this study was to revise the provisions for aluminum-containing food additives in GB 2760-2011 （The National Food Safety Standard for Use of Food Additives）, in order to reduce aluminum exposure among the...The aim of this study was to revise the provisions for aluminum-containing food additives in GB 2760-2011 （The National Food Safety Standard for Use of Food Additives）, in order to reduce aluminum exposure among the Chinese population. According to the latest risk assessment results of JECFA and China on aluminum and the actual use of aluminum-containing food additives in certain products, the aluminum-containing food additive-related provisions in GB 2760-2011 were revised. Those revisions included narrowing down the applicable food categories and adjusting the maximum use level of aluminum potassium sulfate and aluminum ammonium sulfate, repealing nine aluminum-containing food additives in puffed food and repealing the use of sodium aluminum phosphate, sodium aluminosilicate and starch aluminum octenylsuccinate in all food.展开更多
A mobile edge cloud provides a platform to accommodate the offloaded traffic workload generated by mobile devices.It can significantly reduce the access delay for mobile application users.However,the high user mobilit...A mobile edge cloud provides a platform to accommodate the offloaded traffic workload generated by mobile devices.It can significantly reduce the access delay for mobile application users.However,the high user mobility brings significant challenges to the service provisioning for mobile users,especially to delay-sensitive mobile applications.With the objective to maximize a profit,which positively associates with the overall admitted traffic served by the local edge cloud,and negatively associates with the access delay as well as virtual machine migration delay,we study a fundamental problem in this paper:how to update the service provisioning solution for a given group of mobile users.Such a profit-maximization problem is formulated as a nonlinear integer linear programming and linearized by absolute value manipulation techniques.Then,we propose a framework of heuristic algorithms to solve this Nondeterministic Polynomial(NP)-hard problem.The numerical simulation results demonstrate the efficiency of the devised algorithms.Some useful summaries are concluded via the analysis of evaluation results.展开更多
We propose an eco-service provision unit method for estimating the benefit and spatial differences of forests in controlling soil erosion.A total of 197 eco-service provision units were grouped on 1424.43 km2 of fores...We propose an eco-service provision unit method for estimating the benefit and spatial differences of forests in controlling soil erosion.A total of 197 eco-service provision units were grouped on 1424.43 km2 of forest according to differences in vegetation,slope,soil,and rainfall.The amount of soil conservation and its economic value were estimated.The forests in Anji County prevent4.08 9 105 tons of soil from eroding annually,thereby avoiding 1.36 9 104 tons of nutrient loss（on-site cost） and preventing 149 tons of nutritive elements from entering water systems（off-site cost）.From an economic perspective,the soil nutrient conservation in the forests of Anji County generated an annual benefit of 43.37 million RMB（Chinese Currency,6.20 RMB = US$1）.On average,each hectare of ecological forest contributed up to 436 RMB annually because of soil conservation.Ecological complexes with higher rainfall intensity,such as broadleaf forest and red soil on slope gradients [25°,contributed the highest soil conservation benefits.This study identified and quantified the dominant contributors and magnitudes of soil conservation provided by forests.This information can benefit decision making regarding differentiated ecological compensation policies.展开更多
In-network caching and Interest packets aggregation are two important features of Content-Centric Networking(CCN).CCN routers can directly respond to the Interest request by Content Store(CS)and aggregate the same Int...In-network caching and Interest packets aggregation are two important features of Content-Centric Networking(CCN).CCN routers can directly respond to the Interest request by Content Store(CS)and aggregate the same Interest packets by Pending Interest Table(PIT).In this way,most popular content requests will not reach the origin content server.Thus,content providers will be unaware of the actual usages of their contents in network.This new network paradigm presents content providers with unprecedented challenge.It will bring a great impact on existing mature business model of content providers,such as advertising revenue model based on hits amount.To leverage the advantages of CCN and the realistic business needs of content providers,we explore the hits-based content provisioning mechanism in CCN.The proposed approaches can avoid the unprecedented impact on content providers' existing business model and promote content providers to embrace the real deployment of CCN network.展开更多
The Baltic Sea is essential for marine ecosystem services(MES)provision and the region’s socio-economic dy-namics.It is considered one of the busiest and most polluted regional seas in Europe.In recent years a collec...The Baltic Sea is essential for marine ecosystem services(MES)provision and the region’s socio-economic dy-namics.It is considered one of the busiest and most polluted regional seas in Europe.In recent years a collective effort in enforcing European and regional environmental policies and directives(e.g.Water Framework Direc-tive 2000/60/EC,2000;Marine Strategy Framework Directive 2008/56/EC,2008;Maritime Spatial Planning Directive 2014/89/EU,2014)has been carried out.Ecosystem Services assessment and mapping is integrated into these directives.An increasing number of scientific studies,projects,and other works were developed in this context,generating a vast body of knowledge.Despite all efforts to improve the Baltic Sea’s environmental status,the targets established were not fulfilled.It is also important to analyze if current methodological approaches for assessing and mapping MES are robust enough to provide the needed results.This perspective paper analyses the status of assessment and mapping methodologies.The results showed that most of the studies were focused on qualitative assessments,with limited validation and reliability.Although the number of robust and quantitative works is increasing,more are needed.It is vital to carry out quantitative assessments to inform decision-makers better and standardize MES practices across the Baltic Sea.展开更多
基金supported by the National Natural Science Foundation of China(42471336,52379021 and 42201278)the Hebei Province Backbone Talent Program,China(Returnee Platform for Overseas Study)(A20240028)+2 种基金the Hebei Province Statistical Science Research Project,China(2024HZ04)the Hebei Province Graduate Education and Teaching Reform Research Project,China(YJG2024046)the Innovation Ability Training Program for Postgraduate Students of Hebei Provincial Department of Education,China(CXZZSS2025048)。
文摘A comprehensive assessment of grain supply,demand,and ecosystem service flows is essential for identifying grain movement pathways,ensuring regional grain security,and guiding sustainable management strategies.However,current studies primarily focus on short-term grain provision services while neglecting the spatiotemporal variations in grain flows across different scales.This gap limits the identification of dynamic matching relationships and the formulation of optimization strategies for balancing grain flows.This study examined the spatiotemporal evolution of grain supply and demand in the Beijing-Tianjin-Hebei(BTH)region from 1980 to 2020.Using the Enhanced TwoStep Floating Catchment Area method,the grain provision ecosystem service flows were quantified,the changes in supply–demand matching under different grain flow scenarios were analyzed and the optimal distance threshold for grain flows was investigated.The results revealed that grain production follows a spatial distribution pattern characterized by high levels in the southeast and low levels in the northwest.A significant mismatch exists between supply and demand,and it shows a scale effect.Deficit areas are mainly concentrated in the northwest,while surplus areas are mainly located in the central and southern regions.As the spatial scale increases,the ecosystem service supply–demand ratio(SDR)classification becomes more clustered,while it exhibits greater spatial SDR heterogeneity at smaller scales.This study examined two distinct scenarios of grain provision ecosystem service flow dynamics based on 100 and 200 km distance thresholds.The flow increased significantly,from 2.17 to 11.81million tons in the first scenario and from 2.41 to 12.37 million tons in the second scenario over nearly 40 years,forming a spatial movement pattern from the central and southern regions to the surrounding areas.Large flows were mainly concentrated in the interior of urban centers,with significant outflows between cities such as Baoding,Shijiazhuang,Xingtai,and Hengshui.At the county scale,supply–demand matching patterns remained consistent between the grain flows in the two scenarios.Notably,incorporating grain flow dynamics significantly reduced the number of grain-deficit areas compared to scenarios without grain flow.In 2020,grain-deficit counties decreased by28.79 and 37.88%,and cities by 12.50 and 25.0%under the two scenarios,respectively.Furthermore,the distance threshold for achieving optimal supply and demand matching at the county scale was longer than at the city scale in both grain flow scenarios.This study provides valuable insights into the dynamic relationships and heterogeneous patterns of grain matching,and expands the research perspective on grain and ecosystem service flows across various spatiotemporal scales.
基金supported by the Smart Grid-National Science and Technology Major Project of China(2024ZD0802000).
文摘Although wind energy is volatile,the output of a wind-storage plant is partially dispatchable,making it a promising paradigm on the generation side.A grid-friendly wind-storage plant ought to be able to continuously output the desired power over a certain period of time.This paper proposes a dependable dynamic capacity provision scheme of a wind-storage plant over a daily horizon.It stipulates a minimum number of periods during which the committed capacity must be fulfilled and a maximum mismatch during the remaining periods when the desired power output is not achievable.In the general case,the day-ahead piecewise constant capacity provision results in a two-stage stochastic program formulated as a mixed-integer linear program.Specifically,for constant capacity provision,a decomposition algorithm is developed to determine the global optimal solution,and the complexity grows linearly with the number of scenarios.Given the committed capacity trajectory,the real-time operation problem is modeled as a four-state stochastic dynamic program.The discrete state-action values are derived recursively via the principle of optimality.Real-time dispatch actions are generated by using the action-value tabular leveraging inexact ultra-short-term forecasts.Numerical tests over one year demonstrate that the proposed method successfully fulfills reliable operation on 355 days and achieve an optimality gap of 9.47%compared with the ex-post optimum,which is comparable to model predictive control using exact 2–3-hour-ahead wind power forecasts.
基金Sponsored by the Major Projects of National Science and Technology(Grant No.2009ZX03003-003-01)the National Science Fund Young Scholars(Grant No.61001115)the Natural Science Foundation of Beijing,China(Grant No.4102044)
文摘Multiple-input multiple-output (MIMO) wireless communication systems can significantly improve the spectrum efficiency or transmission reliability through spatial multiplexing or diversity respectively.Most of previous works mainly have focused on the multiplexing-diversity tradeoff or switching between multiplexing and diversity without considering the property of heterogeneous QoS provisioning.In this paper,switching between multiplexing and diversity in MIMO system with the heterogeneous QoS provisioning is studied.Firstly the QoS provisioning for users are classified into two classes:users with real time service requirement and users with non-real time service requirement respectively.Then based on the heterogeneous QoS Provisioning for users,two different switching criterions are proposed,switching based on the Euclidean distance for users with real time service to minimize the probability of symbol error and capacity-based switching criterion for users with non-real time service to maximize the transmission capacity respectively.Finally,numerical simulation results are illustrated to demonstrate the performance of proposed scheme.
基金Fundamental Research Funds for the Central Universities,Sun Yat-sen University(23lgzy002)Forestry Administration of Guangdong Province(33000-42090019)+1 种基金Shenzhen Park Service(33000-71020177)Neilingding-Futian National Nature Reserve(33000-71020200)。
文摘Rhesus macaques(Macaca mulatta)have demonstrated a potent capability of adapting to human-disturbed environment.In China,they have become popular attractions in ecotourism areas and receive substantial food from tourists,resulting in local booming populations.Previous studies have highlighted human-macaque conflicts and yet ignored their impact on local natural ecosystems.Through reviewing previous researches,we summarized the contributing factors to the thriving populations of rhesus macaque and expounded upon the potential impacts of them on other local organisms.Booming populations of rhesus macaque caused by provisioning could present potential risks to local plant and animal community through lesser seed dispersal and greater predation and competition pressures on other sympatric species,ultimately impacting the diversity and stability of local ecosystems.Thus,it is imperative to draft the relevant laws to strictly control human provisioning for wild rhesus macaques and conduct further studies to elucidate their interspecies relationships.And a higher priority should be devoted to monitoring these potentially overabundant populations and formulating optimal management strategies to achieve harmonious coexistence between humans and rhesus macaques.
文摘Human well-being and livelihoods depend on natural ecosystem services(ESs).Following the increment of population,ESs have been deteriorated over time.Ultimately,land use/land cover(LULC)changes have a profound impact on the change of ecosystem.The primary goal of this study is to determine the impacts of LULC changes on ecosystem service values(ESVs)in the upper Gilgel Abbay watershed,Ethiopia.Changes in LULC types were studied using three Landsat images representing 1986,2003,and 2021.The Landsat images were classified using a supervised image classification technique in Earth Resources Data Analysis System(ERDAS)Imagine 2014.We classified ESs in this study into four categories(including provisioning,regulating,supporting,and cultural services)based on global ES classification scheme.The adjusted ESV coefficient benefit approach was employed to measure the impacts of LULC changes on ESVs.Five LULC types were identified in this study,including cultivated land,forest,shrubland,grassland,and water body.The result revealed that the area of cultivated land accounted for 64.50%,71.50%,and 61.50%of the total area in 1986,2003,and 2021,respectively.The percentage of the total area covered by forest was 9.50%,5.90%,and 14.80%in 1986,2003,and 2021,respectively.Result revealed that the total ESV decreased from 7.42×10^(7) to 6.44×10^(7) USD between 1986 and 2003.This is due to the expansion of cultivated land at the expense of forest and shrubland.However,the total ESV increased from 6.44×10^(7) to 7.76×10^(7) USD during 2003-2021,because of the increment of forest and shrubland.The expansion of cultivated land and the reductions of forest and shrubland reduced most individual ESs during 1986-2003.Nevertheless,the increase in forest and shrubland at the expense of cultivated land enhanced many ESs during 2003-2021.Therefore,the findings suggest that appropriate land use practices should be scaled-up to sustainably maintain ESs.
基金supported by the National Natural Science Foundation of China(Grants No.U21A2011,41971129)the National Key Research and Development Program of China(Grant No.2022YFF1300403)the Distinguished Membership Project of the Youth Innovation Promotion Association of CAS(Grant No.Y201812)。
文摘Agricultural terraces are significant for food provision,environmental stability and sustainable resource management.However,the spatiotemporal evolution of terraces and their influence on food productivity in mountainous landscapes remain poorly understood.Taking the Chinese Loess Plateau(LP)as an example,this study conducted multitemporal mapping of terraces and sloping croplands over three decades(1990-2020),systematically assessing their impacts on food output through terrain gradient analysis.The results indicated that:(1)the terraced area expanded in the past 30 years,particularly across steeper terrain gradients(third to fifth gradients);(2)sloping croplands predominantly occupied gentle slopes(first to second gradients),exhibiting area reduction correlating with urbanization processes;(3)the food provision increased extensively,with yield decreasing from southeast to northwest and regions of high yielding mainly in terraced fields;(4)over time,the variation of food provision correlated positively with the area of sloping cropland at low gradients,while at higher gradients,the expansion of terraces dominated the increase in food provision;(5)spatial clustering analysis revealed significant food productivity associated with high-density terrace distribution across steeper slope gradients.Low yields could be attributed to improper terrace management.This study clarified the impact of long-term terrace patterns on food provision and offered large-scale perspectives for terrace-based agriculture to enhance food security.Furthermore,the findings underscore the imperative of integrated land management in topographically complex regions,informing evidence-based policymaking for rational allocation and optimal utilization of terrace resources.
基金supported by the National Natural Science Foundation of China(Grant Nos.62201276,62350001,U22B2026,and 62425105)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300701)the Key R&D Program(Industry Foresight and Key Core Technologies)of Jiangsu Province(Grant No.BE2022071)。
文摘As the cornerstone of future information security,quantum key distribution(QKD)is evolving towards large-scale hybrid discrete-variable/continuous-variable(DV/CV)multi-domain quantum networks.Meanwhile,multicast-oriented multi-party key negotiation is attracting increasing attention in quantum networks.However,the efficient key provision for multicast services over hybrid DV/CV multi-domain quantum networks remains challenging,due to the limited probability of service success and the inefficient utilization of key resources.Targeting these challenges,this study proposes two key-resource-aware multicast-oriented key provision strategies,namely the link distance-resource balanced key provision strategy and the maximum shared link key provision strategy.The proposed strategies are applicable to hybrid DV/CV multi-domain quantum networks,which are typically implemented by GG02-based intra-domain connections and BB84-based inter-domain connections.Furthermore,the multicast-oriented key provision model is formulated,based on which two heuristic algorithms are designed,i.e.,the shared link distance-resource(SLDR)dependent and the maximum shared link distance-resource(MSLDR)dependent multicast-oriented key provision algorithms.Simulation results verify the applicability of the designed algorithms across different multi-domain quantum networks,and demonstrate their superiority over the benchmark algorithms in terms of the success probability of multicast service requests,the number of shared links,and the key resource utilization.
文摘Efficient resource provisioning,allocation,and computation offloading are critical to realizing lowlatency,scalable,and energy-efficient applications in cloud,fog,and edge computing.Despite its importance,integrating Software Defined Networks(SDN)for enhancing resource orchestration,task scheduling,and traffic management remains a relatively underexplored area with significant innovation potential.This paper provides a comprehensive review of existing mechanisms,categorizing resource provisioning approaches into static,dynamic,and user-centric models,while examining applications across domains such as IoT,healthcare,and autonomous systems.The survey highlights challenges such as scalability,interoperability,and security in managing dynamic and heterogeneous infrastructures.This exclusive research evaluates how SDN enables adaptive policy-based handling of distributed resources through advanced orchestration processes.Furthermore,proposes future directions,including AI-driven optimization techniques and hybrid orchestrationmodels.By addressing these emerging opportunities,thiswork serves as a foundational reference for advancing resource management strategies in next-generation cloud,fog,and edge computing ecosystems.This survey concludes that SDN-enabled computing environments find essential guidance in addressing upcoming management opportunities.
文摘笛卡尔在《谈谈方法》一书的第三部分中提出了一套道德准则,即morale par provision。最近,一些笛卡尔哲学的研究者们对这一概念提出了三种不同的解读。第一种解读是传统且主流的解读,主张将morale par provision理解为"临时的道德",它是笛卡尔为了保障自己或他人在贯彻"普遍的方法"的第一步"怀疑的方法"或"方法论怀疑"时所采取的一种权宜之计。第二种解读是将morale par provision理解为"先决的道德",强调这种道德的先决性与无条件性。第三种对morale par provision的解读是将之理解为"完美道德的一阶近似"。笛卡尔在《谈谈方法》一书中所做的"建筑的比喻"十分清楚地表明了他提出morale par provision的用意及其真正的含义,他将morale par provision比作为了实施房子重建计划而预先准备的临时的房子。因此,Morale par provision其实是笛卡尔为了保障自己或他人在贯彻"普遍的方法"的第一条准则时仍能够不影响日常生活所采纳的一种策略。在这个意义来说,将morale par provision译作"临时的道德"是合适的,换句话说,三种解读中的第一种解读有其合理的依据。《谈谈方法》是morale par provision的出处,因此它无疑是对这一表述进行解释所要依据的最重要的文本。另外两种解读尽管有其合理的地方且具有创新性,但是,只要它们无法强力地否定《谈谈方法》的文本证据,那么它们就无法真正地驳倒第一种解读。此外,关于morale par provision的另外两种解读的支持理由与证据也并非无懈可击。
基金co-supported by the Outstanding Youth Fund of the National Natural Science Foundation of China (No. 61822102)the MIIT Technological Base Program (No. JSZL2016601B003)the National Key Research and Development Program (No. 2018YFB0505105)。
文摘Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or in segregated controlled airspace. As the industry progresses, both operational and technological capabilities have matured to the point where UASs are expected to gain greater freedom of access to both controlled and uncontrolled airspace. Extensive technical and regulatory surveys have been conducted to enable the expanded operations. However, most surveys are derived from the perspective of UAS own operating mechanism and barely consider interactions of their non-segregated activities with the Air Traffic Management(ATM) system. Hence, to fill the gap, this paper presents a survey conducted from the perspective of Air Navigation Service Provider(ANSP), which serves to accommodate these new entrants to the overall national airspace while continuing flight safety and efficiency. The primary objectives of this paper are to:(A) describe what typical ANSP-supplied UAS Traffic Management(UTM) architecture is required to facilitate all types of civil UAS operations;(B) identify three major ANSP considerations on how UAS can be accommodated safely in civil airspace;(C) outline future directions and challenges related with UAS operations for the ANSP.
基金supported by the Fundamental Research Funds for the Central Universities(NS2015072)
文摘With the wide application of condition based maintenance(CBM) in aircraft maintenance practice, the joint optimization of maintenance and inventory management, which can take full advantage of CBM and reduce the aircraft operational cost, is receiving increasing attention. In order to optimize the inspection interval, maintenance decision and spare provisioning together for aircraft deteriorating parts, firstly, a joint inventory management strategy is presented, then, a joint optimization of maintenance inspection and spare provisioning for aircraft parts subject to the Wiener degradation process is proposed based on the strategy.Secondly, a combination of the genetic algorithm(GA) and the Monte Carol method is developed to minimize the total cost rate.Finally, a case study is conducted and the proposed joint optimization model is compared with the existing optimization model and the airline real case. The results demonstrate that the proposed model is more beneficial and effective. In addition, the sensitivity analysis of the proposed model shows that the lead time has higher influence on the optimal results than the urgent order cost and the corrective maintenance cost, which is consistent with the actual situation of aircraft maintenance practices and inventory management.
基金supported by National Natural Science Foundation of China(grant number 42171258,41877084)Natural Science Foundation of Hunan Province(grant number 2021JJ30448)。
文摘Global climate change and increased human consumption have aggravated the uneven spatiotemporal distribution of watershed water resources, affecting the water provision supply and demand state. However, this problem has often been ignored. The present study used the Xiangjiang River basin(XRB) as the study area, and the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST) model, demand quantification model,supply–demand ratio, and water flow formula were applied to explore the spatial heterogeneity, flow, and equilibrium between water supply and demand. The results demonstrated significant spatial heterogeneity in the upstream, midstream, and downstream regions.The areas of water shortage were mainly located the downstream of the Changsha–Zhuzhou–Xiangtan urban agglomeration, and the Hengyang basin was the most scarcity area. Affected by terrain gradients and human needs, water flow varied from-16.33 × 10^(8) m^(3) to 13.69 × 10^(8) m^(3)from the upstream to the downstream area, which provided a possibility to reduce spatial heterogeneity. In the future, measures such as strengthening water resource system control,sponge city construction, and dynamic monitoring technology should be taken to balance the supply and demand of water in different river sections of the basin. This study can provide references for regulating water resources allocation in different reaches of the basin.
文摘The aim of this study was to revise the provisions for aluminum-containing food additives in GB 2760-2011 （The National Food Safety Standard for Use of Food Additives）, in order to reduce aluminum exposure among the Chinese population. According to the latest risk assessment results of JECFA and China on aluminum and the actual use of aluminum-containing food additives in certain products, the aluminum-containing food additive-related provisions in GB 2760-2011 were revised. Those revisions included narrowing down the applicable food categories and adjusting the maximum use level of aluminum potassium sulfate and aluminum ammonium sulfate, repealing nine aluminum-containing food additives in puffed food and repealing the use of sodium aluminum phosphate, sodium aluminosilicate and starch aluminum octenylsuccinate in all food.
基金partially supported by JSPS KAKENHI under Grant Number JP16J07062
文摘A mobile edge cloud provides a platform to accommodate the offloaded traffic workload generated by mobile devices.It can significantly reduce the access delay for mobile application users.However,the high user mobility brings significant challenges to the service provisioning for mobile users,especially to delay-sensitive mobile applications.With the objective to maximize a profit,which positively associates with the overall admitted traffic served by the local edge cloud,and negatively associates with the access delay as well as virtual machine migration delay,we study a fundamental problem in this paper:how to update the service provisioning solution for a given group of mobile users.Such a profit-maximization problem is formulated as a nonlinear integer linear programming and linearized by absolute value manipulation techniques.Then,we propose a framework of heuristic algorithms to solve this Nondeterministic Polynomial(NP)-hard problem.The numerical simulation results demonstrate the efficiency of the devised algorithms.Some useful summaries are concluded via the analysis of evaluation results.
基金supported by the National Natural Science Foundation (No.31200531)National Science and Technology Support Program (No.2012BAC01B08)the National Environmental Protection Public Welfare Industry Targeted Research (No.201209027)
文摘We propose an eco-service provision unit method for estimating the benefit and spatial differences of forests in controlling soil erosion.A total of 197 eco-service provision units were grouped on 1424.43 km2 of forest according to differences in vegetation,slope,soil,and rainfall.The amount of soil conservation and its economic value were estimated.The forests in Anji County prevent4.08 9 105 tons of soil from eroding annually,thereby avoiding 1.36 9 104 tons of nutrient loss（on-site cost） and preventing 149 tons of nutritive elements from entering water systems（off-site cost）.From an economic perspective,the soil nutrient conservation in the forests of Anji County generated an annual benefit of 43.37 million RMB（Chinese Currency,6.20 RMB = US$1）.On average,each hectare of ecological forest contributed up to 436 RMB annually because of soil conservation.Ecological complexes with higher rainfall intensity,such as broadleaf forest and red soil on slope gradients [25°,contributed the highest soil conservation benefits.This study identified and quantified the dominant contributors and magnitudes of soil conservation provided by forests.This information can benefit decision making regarding differentiated ecological compensation policies.
基金This work was supported by National Key Basic Research Program of China （973 Program） under Grant No. 2012CB315802 National Natural Science Foundation of China under Grant No. 61171102 and No. 61132001 Prospective Research on Future Networks of Jiangsu Future Networks Innovation institute under Grant No. BY2013095-4-01. Beijing Nova Program under Grant No.2008B50 and Beijing Higher Education Young Elite Teacher Project under Grant No.YETP0478.
文摘In-network caching and Interest packets aggregation are two important features of Content-Centric Networking(CCN).CCN routers can directly respond to the Interest request by Content Store(CS)and aggregate the same Interest packets by Pending Interest Table(PIT).In this way,most popular content requests will not reach the origin content server.Thus,content providers will be unaware of the actual usages of their contents in network.This new network paradigm presents content providers with unprecedented challenge.It will bring a great impact on existing mature business model of content providers,such as advertising revenue model based on hits amount.To leverage the advantages of CCN and the realistic business needs of content providers,we explore the hits-based content provisioning mechanism in CCN.The proposed approaches can avoid the unprecedented impact on content providers' existing business model and promote content providers to embrace the real deployment of CCN network.
基金“Lithuanian National Ecosystem Services Assessment and Mapping(LINESAM)”No.09.3.3-LMT-K-712-01-0104 is funded by the European Social Fund according to the activity“Improvement of researchers’qual-ification by implementing world-class R&D projects”of Measure No.09.3.3-LMT-K-712.
文摘The Baltic Sea is essential for marine ecosystem services(MES)provision and the region’s socio-economic dy-namics.It is considered one of the busiest and most polluted regional seas in Europe.In recent years a collective effort in enforcing European and regional environmental policies and directives(e.g.Water Framework Direc-tive 2000/60/EC,2000;Marine Strategy Framework Directive 2008/56/EC,2008;Maritime Spatial Planning Directive 2014/89/EU,2014)has been carried out.Ecosystem Services assessment and mapping is integrated into these directives.An increasing number of scientific studies,projects,and other works were developed in this context,generating a vast body of knowledge.Despite all efforts to improve the Baltic Sea’s environmental status,the targets established were not fulfilled.It is also important to analyze if current methodological approaches for assessing and mapping MES are robust enough to provide the needed results.This perspective paper analyses the status of assessment and mapping methodologies.The results showed that most of the studies were focused on qualitative assessments,with limited validation and reliability.Although the number of robust and quantitative works is increasing,more are needed.It is vital to carry out quantitative assessments to inform decision-makers better and standardize MES practices across the Baltic Sea.
