A system dynamics approach for water resources policy analysis in arid land:a model for Manas River Basin

The Manas River Basin in Xinjiang Uygur autonomous region, similar to other arid regions, is facing water constraints which challenge decision-makers as to how to rationally allocate the available water resources to meet the demands from industries and natural ecosystems. Policies which integrate the supply and demand are needed to address the water stress issues. An object-oriented system dynamics model was developed to capture the interrelationships between water availability and increasing water demands from the growth of industries, agri- cultural production and the population through modeling the decision-making process of the water exploration ex- plicitly, in which water stress is used as a major indicator. The model is composed of four sectors： 1 ） natural surface and groundwater resources; 2） water demand; 3） the water exploitation process, including the decision to build reservoirs, canals and pumps; 4） water stress to which political and social systems respond through increasing the supply, limiting the growth or improving the water use efficiency. The model was calibrated using data from 1949 to 2009 for population growth, irrigated land area, industry output, perceived water stress, groundwater resources availability and the drying-out process of Manas River; and simulations were carried out from 2010 to 2050 on an annual time step. The comparison of results from calibration and observation showed that the model corresponds to observed behavior, and the simulated values fit the observed data and trends accurately. Sensitivity analysis showed that the model is robust to changes in model parameters related to population growth, land reclamation, pumping capacity and capital contribution to industry development capacity. Six scenarios were designed to inves- tigate the effectiveness of policy options in the area of reservoir relocation, urban water recycling, water demand control and groundwater pumping control. The simulation runs demonstrated that the technical solutions for im- proving water availability and water use efficiency are not sustainable. Acknowledging the carrying capacity of water resources and eliminating a growth-orientated value system are crucial for the sustainability of the Manas River Basin.

RESEARCH ON SYSTEM DYNAMICS MODEL OF CONVEYANCE CAPACITY IN SYMMETRIC COMPOUND CHANNELS

Stage-discharge curves are particularly important in river basin management. For a compound channel, the stage-discharge curve is often difficult to be extrapolated to yield estimates of level for a given frequency of flow. By analyzing a large number of experimental data from Science and Engineering Research Council Flood Channel Facility (SERC-FCF) and applying system dynamics method, the authors established system dynamics model of conveyance capacity when rivers flow in an overbank mode, spilling onto the adjoining flood plain. The model was applied to a compound channel. And the corresponding simulated results are shown to attain high accurcy.

Adaptation Decision Support: An Application of System Dynamics Modeling in Coastal Communities

This research develops and applies a system dynamics(SD) model for the strategic evaluation of environmental adaptation options for coastal communities. The article defines and estimates asset-based measures for community vulnerability, resilience, and adaptive capacity with respect to the environmental, economic, social, and cultural pillars of the coastal community under threat. The SD model simulates the annual multidimensional dynamic impacts of severe coastal storms and storm surges on the community pillars under alternative adaptation strategies.The calculation of the quantitative measures provides valuable information for decision makers for evaluating the alternative strategies. The adaptation strategies are designed model results illustrated for the specific context of the coastal community of Charlottetown, Prince Edward Island, Canada. The dynamic trend of the measures and model sensitivity analyses for Charlottetown—facing increased frequency of severe storms, storm surges, and sea-level rise—provide impetus for enhanced community strategic planning for the changing coastal environment.This research is presented as part of the International Community-University Research Alliance C-Change project ‘‘Managing Adaptation to Environmental Change in Coastal Communities: Canada and the Caribbean'' sponsored by the Social Science and Humanities Research Council of Canada and the International Development Resource Centre.

Influence of Human Activity Intensity on Habitat Quality in Hainan Tropical Rainforest National Park,China

Due to long-term human activity interference,the Hainan Tropical Rainforest National Park(HTRNP)of China has experienced ecological problems such as habitat fragmentation and biodiversity loss,and with the expanding scope and intensity of human activity impact,the regional ecological security is facing serious challenges.A scientific assessment of the interrelationship between human activity intensity and habitat quality in the HTRNP is a prerequisite for achieving effective management of ecological disturbances caused by human activities and can also provide scientific strategies for the sustainable development of the region.Based on the land use change data in 2000,2010,and 2020,the spatial and temporal variations and the relationship between habitat quality(HQ)and human activity intensity(HAI)in the HTRNP were explored using the integrated valuation of ecosystem services and trade-offs(InVEST)model.System dynamics and land use simulation models were also combined to conduct multi-scenario simulations of their relationships.The results showed that during 2000–2020,the habitat quality of the HTRNP improved,the intensity of human activities decreased each year,and there was a negative correlation between the two.Second,the system dynamic model could be well coupled with the land use simulation model by combining socio-economic and natural factors.The simulation scenarios of the coupling model showed that the harmonious development(HD)scenario is effective in curbing the increasing trend of human activity intensity and decreasing trend of habitat quality,with a weaker trade-off between the two compared with the baseline development(BD)and investment priority oriented(IPO)scenarios.To maintain the authenticity and integrity of the HTRNP,effective measures such as ecological corridor construction,ecological restoration,and the implementation of ecological compensation policies need to be strengthened.

Effects of precipitation changes on the dynamics of sparse elm woodland in Northeastern China

Elm(Ulmus pumila L.)is the dominant tree species in the sparse elm woodland,the original vegetation in the Horqin Sandy Land.The effects of changes in precipitation on U.pumila trees have not been fully studied.We determined a dynamic model by considering the five stages in the U.pumila life cycle,i.e.seed,seedling,and juvenile,mature and over-mature tree stages.The effects of changes in precipitation on population density and age structure were then evaluated.Population density,after averaging all study developmental morphology stages,ranged from 16.67 individuals/m2 to 25.01 individuals/m2 under a mean annual precipitation(MAP)of 80%to 120%,respectively.This suggests that population density could increase as MAP also increased.The proportion of seedlings,and juvenile,mature and over-mature trees were 95.23%,4.58%,0.19%and 0.01%,respectively,under all precipitation levels.This indicates that precipitation had little effects on the developmental stages of the studied U.pumila populations in the Horqin Sandy Land.Additional water supply might be provided in addition to the natural rainfall that occurs in the region,for contributing to maintain U.pumila population density in the Horqin Sandy Land.

Study on the driving factors and regulation mode for coal production capacity

Coal production capacity regulation is a complex system involving economic growth,structural optimization,high-efficiency mining,and environmental protection.Based on its driving factors,this paper forms four regulation modes representing different control orientations,establishes a system dynamics model,and predicts the regulation effects of single-factor and combined control mode.The result shows:(1) Except for the mechanization degree and recovery rate,the other nine individual production capacity control policies are all conducive to reducing coal production capacity and restraining the excessive growth of coal production capacity.(2) The effect of combined regulation mode on slowing down the growth of coal demand,regulating the excessive growth of coal production capacity and new capacity investment are obviously better than that of single policy.(3) The combined control modes have obvious differences in the suppression effect on coal production capacity:transformational development mode > technology-driven mode > structural optimization mode > efficiency improvement mode.Therefore,in the process of achieving optimal regulation of coal production capacity,attention should be paid to the preferential use of transformational development and technology-driven mode.At the same time,the comprehensive use of regulation and control methods should also be considered to improve the regulation effect and the regulation efficiency of coal production capacity.

Control performance simulation and tests for Microgravity Active vibration Isolation System onboard the Tianzhou-1 cargo spacecraft

The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g for specific scientific experiments.MAIS is mainly composed of a stator and a floater,and payloads are mounted on the floater.Sensing relative motion with respect to the stator fixed on the spacecraft,the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators.This isolation results in a high-level microgravity environment.Before MAIS was launched into space,its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight.This article first presents an overview of the MAIS’s hardware system,particularly system structure,measurement sensors,and control actuators.Its system dynamics,state estimation,and control laws are then discussed,followed by the results of computer simulation and engineering tests,including the test of the six-degree-of-freedom motion by aircraft parabolic flight.Simulation and test results verify the accuracy of the control strategy design,effectiveness of the control algorithms,and performance of the entire control system,paving the way for operation of MAIS in space.This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices.These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.

Evaluation and Dynamics Mechanism of the Smart Specialization Level in China's Regional Manufacturing Industry

Smart specialization,as an important concept in regional policy,has presented greater vitality in both theory and practice.To assess smart specialization at three different levels—smart level,specialization level,and coupling level—this paper develops an index system.We statically evaluate the level of smart specialization in the manufacturing industry in the 30 provinces and municipalities on China’s mainland using the entropy weight-TOPSIS method and then use a system dynamics model to examine the dynamic development characteristics of the level of smart specialization in each region.The findings indicate that there are considerable regional differences in the development level and speed of smart specialization among provinces and municipalities.The development of the smart specialization level of manufacturing follows a“logarithmic index”curve in terms of its shape.The level of industrial smart specialization is positively impacted by the level of industrial smartness,specialization and coupling;however,this effect is critical in scale and nature.To achieve the best effects from the development of manufacturing smart specialization,a continuous,dynamic,and integrated intervention mix should be established.

可持续发展情景下丝绸之路沿线国家土地利用及其对陆地碳库影响

可持续发展目标(SDGs)呼吁全世界共同采取行动,促进繁荣并保护地球.本研究面向SDGs构建了环境、粮食和经济等可持续发展情景,预测2020~2030年丝绸之路沿线国家的土地利用变化,并分析其对陆地碳库的影响。研究表明:未来土地利用变化及其对陆地碳库的影响在不同情景下存在显著差异。在可持续环境情景下,林地得到了有效保护,相较于2020年中国林地碳储量增加了约0.60%;在可持续粮食情景下,耕地流失得到了缓解,尤其在南亚及东南亚地区的耕地面积呈现上升趋势:在可持续经济情景下,城市扩张速度加快,引起的碳损失量最多这项研究有助于推进丝绸之路沿线甚至全球可持续发展进程,为探寻可持续发展路径提供了科学依据。

A ONE-STOP LOGISTIC SERVICES FRAMEWORK SUPPORTING GLOBAL SUPPLY CHAIN COLLABORATION

A global enterprise must continuously improve the efficiency of logistic operations between supply chain collaborators. Integrating logistic services, resources, and necessary information flows in the supply chain to ensure efficiency and efficacy is critically important to these companies. Global logistic service companies face challenges from their clients to provide logistic services that are cost effective, accurate, and seamlessly integrate material, information and cash flows. In this research, an improved framework for one-stop logistic services is systematically designed, analyzed, and evaluated. The one-stop logistic service framework, defmed in four models, is developed to provide enterprises with integrated and comprehensive services within the global supply chain context. The levels of service importance are assessed using a four categories questionnaire. This research provides a case study of the implementation of one-stop logistic services in the distribution industry and demonstrates the framework operating under different demand conditions. Finally, system dynamics causal evaluation is used to evaluate the advantages of the logistic service framework.