Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studi...Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.展开更多
This study investigates the impact of corruption on corporate cash holdings in China. The political extraction argument predicts that firms might shelter liquid assets to avoid extraction by corrupt officials. Using d...This study investigates the impact of corruption on corporate cash holdings in China. The political extraction argument predicts that firms might shelter liquid assets to avoid extraction by corrupt officials. Using data on A-shared listed firms between 2007 and 2012, we find that firms located in more corrupt regions hold less cash, supporting this hypothesis. Political resources help to diminish the risk of exploitation, reducing the extent to which liquid assets are sheltered. We find that the negative association between corruption and cash holding is more significant for non-state-owned enterprises(Non-SOEs)than for state-owned enterprises(SOEs). Moreover, the cash holdings of Non-SOEs without political connections are more sensitive to corruption than those of Non-SOEs with political connections. These findings demonstrate that expropriation by corrupt officials is an important factor driving firms to manage liquidity.展开更多
Based on the dynamic and thermodynamic equations in the SBL,the protection characteristics and mech- anism of shelterbelts are numerically studied in this paper.The results are in consistent with those ob- served in f...Based on the dynamic and thermodynamic equations in the SBL,the protection characteristics and mech- anism of shelterbelts are numerically studied in this paper.The results are in consistent with those ob- served in fields and wind-tunnels.Research shows that the belts with a permeability of 0.3—0.4 have the maximum sheltering effects.The distance where wind speed reduces at least by 20% is at 18—19 times of tree height(H)behind belts.The protection distance reduces fast with the increase of the permeability and slowly with its decrease.The belts have weaker sheltering effects in upstream,generally beyond 6H in front of belts there are no sheltering effects.In addition,the belts with low permeability at top and high permeability at bottom have much better sheltering effects than the belts with high permeability at top and low permeability at bottom.The belts with 50% overall permeability reduce wind speed at least,by 20% at the distance of 5H on the leeward side and by 10% at 11H.When the air is unstable,the protecting effects will be reduced.For the uniform belts with a permeability of 0.35,the distance where wind speed reduces at least by 20% is 15H under the unstable air and 13H under very unstable air.The belts reduce the turbulent diffusion coefficient at the bottom of belts,but increase it at the top.展开更多
The resettlement of millions of destitute earthquake victims is the government’s next priority One of the first tasks of central and local governments after the col- lapse of infrastructure following the May 12 quake...The resettlement of millions of destitute earthquake victims is the government’s next priority One of the first tasks of central and local governments after the col- lapse of infrastructure following the May 12 quake has been to devise a plan to settle the victims by mobilizing all resources and setting up relief centers展开更多
A decline in tree growth has occurred in numerous regions over recent decades and is associated with enhanced water deficits driven by climate warming.This phenomenon may be more noticeable at lower latitudes with hig...A decline in tree growth has occurred in numerous regions over recent decades and is associated with enhanced water deficits driven by climate warming.This phenomenon may be more noticeable at lower latitudes with higher temperatures.However,the process by which these elevated temperatures alter growth performance is not well understood.In this study,by combining tree-ring data(including 340 increment cores)and remotely sensed vegetation index data,we investigated the long-term growth performance of Pinus sylvestris var.mongolica Litv.(Mongolian pine),an important species for afforestation in northern China,in response to environmental factors in an area of introduction(lower latitude)and its native range(higher latitude).More notable decreases in both tree-ring width index(RWI)and basal area increment at breast height coincided with lower values and larger variations in the satellite-derived vegetation index in the area of introduction.The RWI showed stronger negative correlations with temperature and positive correlations with the self-calibrating Palmer drought severity index during most months in the introduction area.These results indicate that enhanced drought stress caused by elevated temperatures in lower latitudes might be a key factor for the growth decline in Mongolian pine plantations.The negative impact of increased temperatures on tree growth through exacerbating drought stress at lower latitudes with water deficit highlights the need to reduce water stress in forest management in such areas under climate warming-driven aridification.展开更多
Fangcang shelter hospitals are modular,rapidly deployable facilities that play a vital role in pandemic response by providing centralized isolation and basic medical care for large patient populations.Artificial intel...Fangcang shelter hospitals are modular,rapidly deployable facilities that play a vital role in pandemic response by providing centralized isolation and basic medical care for large patient populations.Artificial intelligence(AI)has the potential to transform Fangcang shelter hospitals into intelligent,responsive systems that are capable of significantly improving emergency preparedness,operational efficiency,and patient outcomes.Key application areas include site selection and design optimization,clinical decision support,AI-assisted clinical documentation and patient engagement,intelligent robotics,and operational management.However,realizing AI's full potential requires overcoming several challenges,including limited data accessibility,privacy and governance concerns,inadequate algorithmic adaptability in dynamic emergency settings,insufficient transparency and accountability in AI-driven decisions,fragmented system architectures due to proprietary formats,high costs disproportionate to the temporary nature of Fangcang shelter hospitals,and hardware reliability in austere environments.Addressing these challenges demands standardized data-sharing frameworks,development of explainable and robust AI algorithms,clear ethical and legal oversight,interoperable modular system designs,and active collaboration among multidisciplinary stakeholders.展开更多
With the sustainable and efficient development of aqueous zinc ion batteries(AZIBs),the research on addressing the issues of the adaptability and durability of zinc anodes has been hot-topic and is still of great chal...With the sustainable and efficient development of aqueous zinc ion batteries(AZIBs),the research on addressing the issues of the adaptability and durability of zinc anodes has been hot-topic and is still of great challenge.In this work,inspired by the sand treatment and afforestation of the Gobi Beach in Northwest China to ameliorate the problem of wind and sand encroachment,we propose a material with a morphology similar to that of a“shelter forest”,CuSiO_(3)nanoneedles arrays grown on both sides of reduced graphene oxide(rGO@CuSi),as a coating layer on the zinc metal surface to guide Zn gradient deposition.The presence of rGO improves the electrical conductivity of CuSiO_(3),and the finite element simulation of the electric field and Zn^(2+)concentration proves that the electric field distribution can be effectively homogenized and the local current density can be reduced for the rGO@CuSi-Zn electrode with the surface presenting the shape of a protective forest.This is due to the abundant pores between the nano-needle array structures on the surface of the electrode,which provide high electron and ion transport paths,and are conducive to achieving uniform Zn deposition,like the principle of wind-sand stabilization by protective forest.Both electrochemical experiments and density functional theory calculations show that the negatively charged surface of r GO@CuSi with good Zn affinity is more capable of guiding Zn^(2+)transport.Thanks to its inherent material and structural characteristics,the r GO@CuSi-Zn anode has a high specific capacity and good cycling stability.This study provides insight for interface engineering like protective forest to accelerate the commercialization of high-performance Zn-based batteries.展开更多
Sphere packing is an attractive way to generate high quality mesh. Several algorithms have been proposed in this topic, however these algorithms are not sufficiently fast for large scale problems. The paper presents a...Sphere packing is an attractive way to generate high quality mesh. Several algorithms have been proposed in this topic, however these algorithms are not sufficiently fast for large scale problems. The paper presents an efficient sphere packing algorithm which is much faster and appears to be the most practical among all sphere packing methods presented so far for mesh generation. The algorithm packs spheres inside a domain using advancing front method. High efficiency has resulted from a concept of 4R measure, which localizes all the computations involved in the whole sphere packing process.展开更多
This work presents a new analytical method to analyze the influence of reaction piles on the test pile response in a static load test.In our method,the interactive effect between soil and pile is simulated using indep...This work presents a new analytical method to analyze the influence of reaction piles on the test pile response in a static load test.In our method,the interactive effect between soil and pile is simulated using independent springs and the shear displacement method is adopted to analyze the influence of reaction piles on test pile response.Moreover,the influence of the sheltering effect between reaction piles and test pile on the test pile response is taken into account.Two cases are analyzed to verify the rationality and efficiency of the present method.This method can be easily extended to a nonlinear response of an influenced test pile embedded in a multilayered soil,and the validity is also demonstrated using centrifuge model tests and a computer program presented in the literature.The present analyses indicate that the proposed method will lead to an underestimation of the test pile settlement in a static load test if the influence of the presence of reaction piles on the test pile response is neglected.展开更多
A numerical wave flume with fully nonlinear free surface boundary conditions is adopted to investigate the temporal characteristics of extreme waves in the presence of wind at various speeds. Incident wave trains are ...A numerical wave flume with fully nonlinear free surface boundary conditions is adopted to investigate the temporal characteristics of extreme waves in the presence of wind at various speeds. Incident wave trains are numerically generated by a piston-type wave maker, and the wind-excited pressure is introduced into dynamic boundary conditions using a pressure distribution over steep crests, as defined by Jeffreys＇ sheltering mechanism.A boundary value problem is solved by a higher-order boundary element method（HOBEM） and a mixed Eulerian-Lagrangian time marching scheme. The proposed model is validated through comparison with published experimental data from a focused wave group. The influence of wind on extreme wave properties,including maximum extreme wave crest, focal position shift, and spectrum evolution, is also studied. To consider the effects of the wind-driven currents on a wave evolution, the simulations assume a uniform current over varying water depth. The results show that wind causes weak increases in the extreme wave crest, and makes the nonlinear energy transfer non-reversible in the focusing and defocusing processes. The numerical results also provide a comparison to demonstrate the shifts at focal points, considering the combined effects of the winds and the wind-driven currents.展开更多
The need for reforestation in cork oak （Quercus suber L.） areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings....The need for reforestation in cork oak （Quercus suber L.） areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings. We evaluated the early development of cork oak seedlings treated using tree shelters and mulching in northwestern Tunisia. We tested three tree shelter treatments （non-vented, vented, and control） to shield seedlings from animal damage and five mulch types to control competing vegetation （Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk （organic mulches）, gravel （inorganic mulch） and no mulch）. At the end of the two-year experiment, sheltered seedlings were 89-99% taller than unshelteredseedlings and had higher numbers and lengths of shoot growth flushes. In contrast, both stem diameter growth and dry weight biomass （from samples extracted after two years） were significantly reduced inside tree shelters. Root-to-shoot ratio was not significantly different in sheltered vs. unsheltered seedlings, suggesting that tree shelters do not adversely affect this parameter. Mulching alone did not favour growth, but could be beneficial when combined with tree shelters. The combination of vented tree shelters and gravel mulch was the most effective treatment for promoting diameter, height and stem volume growth.展开更多
Ecological shelter zones reconstruction is an ecosystem restoration and conservation project aimed to the ecological safety of nations, regions and basins. Reconstruction of ecological shelter zones of the upper reach...Ecological shelter zones reconstruction is an ecosystem restoration and conservation project aimed to the ecological safety of nations, regions and basins. Reconstruction of ecological shelter zones of the upper reaches of the Yangtze River became one of the most important tasks of Western Development strategy. This article, taking Zhaotong as an example, studies the functional regionalization of ecological shelter zones. The study supplies a case for functional regionalization of small and medium regions whose main tasks are environment reservation. With the guidance of theories of functional regionalization, and based on the analysis of Zhaotong＇s natural, ecological and socioeconomic factors, the paper suggests five principles for factors selection. These principles include： （1） reversing order evaluation; （2） selecting main factors; （3） keeping the integrality of administrative regions of towns; and （4） making the products acceptable by local government. To analyze spatial status of selected factors, LUCC data in 2002, 1：50,000 relief maps and town-unit socioeconomic statistical data in 2004 are used. RS and GIS tools are also applied to melt traditional and modern geographical methods. This would be useful to functional regionalization research in mountainous areas. As a conclusion, the leading functional regions of ecological conservation or economic development are suggested, respectively. Zhaotong city is divided into two-level functional regions. The first-level includes three leading functional regions and they will lead developing direction of sub-regions. The second-level includes eight sub-regions, which are policy implemented regions, and will supply guidance to Zhaotong＇s ecological shelter zones reconstruction.展开更多
Following the Chichi Earthquake （ML=7.3） in 1999, sediment-related disasters, such as landslides and debris flows, have become more frequent in Taiwan. Because engineering structures cannot be fully and rapidly empl...Following the Chichi Earthquake （ML=7.3） in 1999, sediment-related disasters, such as landslides and debris flows, have become more frequent in Taiwan. Because engineering structures cannot be fully and rapidly emplaeed, the government has initiated non-structural hazard mitigation programs. Initially, community debris flow evacuation drills were promoted in 2000. Typhoon Toraji caused numerous debris flow events in July 2001, and some communities evacuated according to the drills, significantly reducing the numbers of possible casualties. Based on that result, the government expanded the program for evacuation drills. Secondly, the early warning system created after the Chichi Earthquake will prevent many potential future casualties. Rainfall threshold values for debris flow warnings in different areas are determined from information received from local weather stations and modified for local geomorphologic situations. Real- time information is gradually being integrated to create a debris flow disaster warning system, the goal of which is to provide warnings to zones in which debris flows are likely. The warning system was launched in 2005 and has two levels of alarms： yellow and red. The final, red alarm triggers enforced evacuation. Overall, the decrease in casualties from debris flows during the decade after the Chichi Earthquake is not the result of a decrease in number or severity of sediment related disasters, but is more directly related to the gradually improved early warning and evacuation system. However, the compound hazards resulting from Typhoon Morakotin 2009 remind us of the ongoing need for improving the existing mitigation system.展开更多
Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by...Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by surface erosion that may occur after the construction of the solar PVpower station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary toinvestigate the characteristics of wind-sand movement under the interference of solar PV array. The studywas undertaken by measuring sediment transport of different wind directions above shifting dunes andthree observation sites around the PV panels in the Hobq Desert, China. The results showed that the twoparameterexponential function provides better fit for the measured flux density profiles to the near-surfaceof solar PV array. However, the saltation height of sand particles changes with the intersection anglebetween the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting duneswas always the greatest, while that around the test PV panels varied accordingly to the wind direction.Moreover, the aeolian sediment transport on the solar PV array was significantly affected by wind direction.The value of sand inhibition rate ranged from 35.46% to 88.51% at different wind directions. When theintersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reducesto 82.58% compared with the shifting dunes. The results of our study expand our understanding of theformation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the designand control engineering plans for solar PV array in sandy areas that operate according to the wind regime.展开更多
Sustainable livelihood theory provides a comprehensive framework for understanding the interactions between livelihoods of peasant households and regional environment change in low-income areas. Based on field survey ...Sustainable livelihood theory provides a comprehensive framework for understanding the interactions between livelihoods of peasant households and regional environment change in low-income areas. Based on field survey and 946 questionnaires from peasant household conducted in the case study area of Zhaotong, Yunnan Province, the paper has analyzed the basic characteristics of the rural livelihoods, including the asset base status, the income-generating activities, the energy consumption pattern, and the fertility behavior, in the upper reaches of the Changjiang (Yangtze) River. The micro-level findings show the conflicts among extensive agricultural development models, rural energy consumption structures heavily relying on biomass and the environment protection. The conversion of cropland to forest and grass program(CCFGP) has exerted an important influence on the livelihoods of the peasant households, but its design has given little considerations to their long-term livelihood sources, which will affect its sustainability to a great extent. From the perspective of sustainable livelihoods framework, the objectives that must be addressed in the ecological shelter construction in the upper reaches of the Changjiang River should include, first, facilitating access of peasant households to credit, technology and public services, second, encouraging the peasant households to adopt agricultural technology with environmental benefits and strengthen resources-conserving investments, and third, paying close attention to the rural energy problems and the long-term livelihood sources of the households with CCFGP. Given the weak asset base and difficulties of livelihood strategies shift, ecological shelter construction in the upper reaches of the Changjiang River will take a long time.展开更多
Porosity is the most important parameter determining the shelter efficiency of fences. Wind measurements were made around fence models with different porosities in a wind tunnel. The optimal fence porosity is evaluate...Porosity is the most important parameter determining the shelter efficiency of fences. Wind measurements were made around fence models with different porosities in a wind tunnel. The optimal fence porosity is evaluated by means of Gandemer＇s method that combines the effects of wind reduction and turbulence fields on the shelter efficiency for abating wind erosion. Defining the optimal porosity must take into account of its own purposes, required shelter degree and area to be sheltered. Turbulence has profound impacts on the shelter efficiency of high degree. Two concepts： absolute optimal porosity and practical optimal porosity concerning optimal porosity are proposed. Choosing the practical optimal porosity means reducing cost without significant expense of shelter efficiency. According to the evaluation in present study, the absolute optimal porosity for providing high degree of shelter to abate wind erosion is 0.20 while the practical optimal porosity is around 0.40. Ifa less shelter degree but over wider area is required, the absolute optimal porosity ranges from 0.05 to 0.10 and the practical optimal porosity is 0.10. For any degree of shelter for abating wind erosion effectively, the fence porosity must be less than or equal 0.40.展开更多
Rock crevices are important retreat sites for many reptiles.Unlike lizards and snakes,crevicedwelling turtles have rigid shells which severely limit the size and shape of crevices they are able to use.Few studies have...Rock crevices are important retreat sites for many reptiles.Unlike lizards and snakes,crevicedwelling turtles have rigid shells which severely limit the size and shape of crevices they are able to use.Few studies have addressed the relationship between turtle's shell morphology,behavior,and crevice size.Here,we investigate the relationship between morphology and crevice size selection in the Keeled box turtle(Cuora mouhotii).We radio tracked turtles in the field to document crevice dimensions and turtle behavior associated with crevices,and we conducted a controlled experiment in the lab to understand how a turtle's morphology influences its decision to select crevices with different dimensions.Both laboratory and field experiments demonstrate that turtles select deep and moderately wide crevices that are low enough to barely accommodate the carapace.Crevices used by turtles tend to be about 2 times as wide,1.2 times as high,and 3 times longer than the turtle's shell.Moreover,turtles tended to prefer crevices with horizontal openings in the field and position themselves head first in the crevice.We conclude that morphology,especially carapace height,influences the Keeled box turtles' decision to select specific sizes of crevice.We argue that the tendency for turtles to select crevices that come into contact with their carapace contributes to successful defense against predators,as it would be more difficult for a predator to remove a turtle when the crevice is nearly touching the turtles shell.展开更多
In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healt...In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.展开更多
Carbon monoxide （CO） is an odorless, colorless gas produced by incomplete combustion of carbonbased compounds. Exposure to CO can cause various adverse health effects ranging from headache and fatigue to coma and de...Carbon monoxide （CO） is an odorless, colorless gas produced by incomplete combustion of carbonbased compounds. Exposure to CO can cause various adverse health effects ranging from headache and fatigue to coma and death. Thousands of illnesses and deaths have been documented through CO poisoning surveillance systems and accident investigations each year.展开更多
基金This research was funded by the Fellowship of the China Postdoctoral Science Foundation(2021M703466)the Basic Research Innovation Group Project of Gansu Province,China(21JR7RA347)the Natural Science Foundation of Gansu Province,China(20JR10RA231).
文摘Sand fences made of punched steel plate(PSP)have recently been applied to control wind-blown sand in desertified and Gobi areas due to their strong wind resistance and convenient in situ construction.However,few studies have assessed the protective effect of PSP sand fences,especially through field observations.This study analyzes the effects of double-row PSP sand fences on wind and sand resistance using field observations and a computational fluid dynamics(CFD)numerical simulation.The results of field observations showed that the average windproof efficiencies of the first-row and second-row sand fences were 79.8%and 70.8%,respectively.Moreover,the average windproof efficiencies of the numerical simulation behind the first-row and second-row sand fences were 89.8%and 81.1%,respectively.The sand-resistance efficiency of the double-row PSP sand fences was 65.4%.Sand deposition occurred close to the first-row sand fence;however,there was relatively little sand on the leeward side of the second-row sand fence.The length of sand accumulation near PSP sand fences obtained by numerical simulation was basically consistent with that through field observations,indicating that field observations combined with numerical simulation can provide insight into the complex wind-blown sand field over PSP sand fences.This study indicates that the protection efficiency of the double-row PSP sand fences is sufficient for effective control of sand hazards associated with extremely strong wind in the Gobi areas.The output of this work is expected to improve the future application of PSP sand fences.
基金supported by the National Natural Science Foundation of China [Grant No.71572019]Graduate Scientific Research and Innovation Foundation of Chongqing,China [Grant No.CYB16001]+2 种基金National Natural Science Foundation of China [Grant Nos.71602013,71772019]The Humanities and Social Sciences Foundation of the Ministry of Education [Grant No.17YJA630017]Fundamental Research Funds for Central Universities [Grant No.2017CDJSK02 PT01]
文摘This study investigates the impact of corruption on corporate cash holdings in China. The political extraction argument predicts that firms might shelter liquid assets to avoid extraction by corrupt officials. Using data on A-shared listed firms between 2007 and 2012, we find that firms located in more corrupt regions hold less cash, supporting this hypothesis. Political resources help to diminish the risk of exploitation, reducing the extent to which liquid assets are sheltered. We find that the negative association between corruption and cash holding is more significant for non-state-owned enterprises(Non-SOEs)than for state-owned enterprises(SOEs). Moreover, the cash holdings of Non-SOEs without political connections are more sensitive to corruption than those of Non-SOEs with political connections. These findings demonstrate that expropriation by corrupt officials is an important factor driving firms to manage liquidity.
文摘Based on the dynamic and thermodynamic equations in the SBL,the protection characteristics and mech- anism of shelterbelts are numerically studied in this paper.The results are in consistent with those ob- served in fields and wind-tunnels.Research shows that the belts with a permeability of 0.3—0.4 have the maximum sheltering effects.The distance where wind speed reduces at least by 20% is at 18—19 times of tree height(H)behind belts.The protection distance reduces fast with the increase of the permeability and slowly with its decrease.The belts have weaker sheltering effects in upstream,generally beyond 6H in front of belts there are no sheltering effects.In addition,the belts with low permeability at top and high permeability at bottom have much better sheltering effects than the belts with high permeability at top and low permeability at bottom.The belts with 50% overall permeability reduce wind speed at least,by 20% at the distance of 5H on the leeward side and by 10% at 11H.When the air is unstable,the protecting effects will be reduced.For the uniform belts with a permeability of 0.35,the distance where wind speed reduces at least by 20% is 15H under the unstable air and 13H under very unstable air.The belts reduce the turbulent diffusion coefficient at the bottom of belts,but increase it at the top.
文摘The resettlement of millions of destitute earthquake victims is the government’s next priority One of the first tasks of central and local governments after the col- lapse of infrastructure following the May 12 quake has been to devise a plan to settle the victims by mobilizing all resources and setting up relief centers
基金supported by the National Natural Science Foundation of China(grants number 32220103010,32192431,31722013,32101587,32271571)the National Key R&D Program of China(2020YFA0608100)+1 种基金the Major Program of Institute of Applied Ecology,Chinese Academy of Sciences(IAEMP202201)Liaoning Provincial Science and Technology Major Project(2023JH1/10400001).
文摘A decline in tree growth has occurred in numerous regions over recent decades and is associated with enhanced water deficits driven by climate warming.This phenomenon may be more noticeable at lower latitudes with higher temperatures.However,the process by which these elevated temperatures alter growth performance is not well understood.In this study,by combining tree-ring data(including 340 increment cores)and remotely sensed vegetation index data,we investigated the long-term growth performance of Pinus sylvestris var.mongolica Litv.(Mongolian pine),an important species for afforestation in northern China,in response to environmental factors in an area of introduction(lower latitude)and its native range(higher latitude).More notable decreases in both tree-ring width index(RWI)and basal area increment at breast height coincided with lower values and larger variations in the satellite-derived vegetation index in the area of introduction.The RWI showed stronger negative correlations with temperature and positive correlations with the self-calibrating Palmer drought severity index during most months in the introduction area.These results indicate that enhanced drought stress caused by elevated temperatures in lower latitudes might be a key factor for the growth decline in Mongolian pine plantations.The negative impact of increased temperatures on tree growth through exacerbating drought stress at lower latitudes with water deficit highlights the need to reduce water stress in forest management in such areas under climate warming-driven aridification.
文摘Fangcang shelter hospitals are modular,rapidly deployable facilities that play a vital role in pandemic response by providing centralized isolation and basic medical care for large patient populations.Artificial intelligence(AI)has the potential to transform Fangcang shelter hospitals into intelligent,responsive systems that are capable of significantly improving emergency preparedness,operational efficiency,and patient outcomes.Key application areas include site selection and design optimization,clinical decision support,AI-assisted clinical documentation and patient engagement,intelligent robotics,and operational management.However,realizing AI's full potential requires overcoming several challenges,including limited data accessibility,privacy and governance concerns,inadequate algorithmic adaptability in dynamic emergency settings,insufficient transparency and accountability in AI-driven decisions,fragmented system architectures due to proprietary formats,high costs disproportionate to the temporary nature of Fangcang shelter hospitals,and hardware reliability in austere environments.Addressing these challenges demands standardized data-sharing frameworks,development of explainable and robust AI algorithms,clear ethical and legal oversight,interoperable modular system designs,and active collaboration among multidisciplinary stakeholders.
基金the Natural Science Foundation of Liaoning Province(2023-MS-115)National Natural Science Foundation of China(52173206)CNPC Innovation Found(2020D-5007-0406)。
文摘With the sustainable and efficient development of aqueous zinc ion batteries(AZIBs),the research on addressing the issues of the adaptability and durability of zinc anodes has been hot-topic and is still of great challenge.In this work,inspired by the sand treatment and afforestation of the Gobi Beach in Northwest China to ameliorate the problem of wind and sand encroachment,we propose a material with a morphology similar to that of a“shelter forest”,CuSiO_(3)nanoneedles arrays grown on both sides of reduced graphene oxide(rGO@CuSi),as a coating layer on the zinc metal surface to guide Zn gradient deposition.The presence of rGO improves the electrical conductivity of CuSiO_(3),and the finite element simulation of the electric field and Zn^(2+)concentration proves that the electric field distribution can be effectively homogenized and the local current density can be reduced for the rGO@CuSi-Zn electrode with the surface presenting the shape of a protective forest.This is due to the abundant pores between the nano-needle array structures on the surface of the electrode,which provide high electron and ion transport paths,and are conducive to achieving uniform Zn deposition,like the principle of wind-sand stabilization by protective forest.Both electrochemical experiments and density functional theory calculations show that the negatively charged surface of r GO@CuSi with good Zn affinity is more capable of guiding Zn^(2+)transport.Thanks to its inherent material and structural characteristics,the r GO@CuSi-Zn anode has a high specific capacity and good cycling stability.This study provides insight for interface engineering like protective forest to accelerate the commercialization of high-performance Zn-based batteries.
基金the National Natural Science Foundation of China (10602002 and 10772005)
文摘Sphere packing is an attractive way to generate high quality mesh. Several algorithms have been proposed in this topic, however these algorithms are not sufficiently fast for large scale problems. The paper presents an efficient sphere packing algorithm which is much faster and appears to be the most practical among all sphere packing methods presented so far for mesh generation. The algorithm packs spheres inside a domain using advancing front method. High efficiency has resulted from a concept of 4R measure, which localizes all the computations involved in the whole sphere packing process.
基金Project supported by the China Postdoctoral Science Foundation (No. 2012M521339)the Independent Innovation Foundation of Shandong University (No. 2012GN012),China
文摘This work presents a new analytical method to analyze the influence of reaction piles on the test pile response in a static load test.In our method,the interactive effect between soil and pile is simulated using independent springs and the shear displacement method is adopted to analyze the influence of reaction piles on test pile response.Moreover,the influence of the sheltering effect between reaction piles and test pile on the test pile response is taken into account.Two cases are analyzed to verify the rationality and efficiency of the present method.This method can be easily extended to a nonlinear response of an influenced test pile embedded in a multilayered soil,and the validity is also demonstrated using centrifuge model tests and a computer program presented in the literature.The present analyses indicate that the proposed method will lead to an underestimation of the test pile settlement in a static load test if the influence of the presence of reaction piles on the test pile response is neglected.
基金The National Natural Science Foundation of China under contract Nos 51679036,51490672 and 51709038the Fundamental Research Funds for the Central Universities under contract Nos DUT17GJ202 and DUT16RC(3)113the Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering under contract No.2016490111
文摘A numerical wave flume with fully nonlinear free surface boundary conditions is adopted to investigate the temporal characteristics of extreme waves in the presence of wind at various speeds. Incident wave trains are numerically generated by a piston-type wave maker, and the wind-excited pressure is introduced into dynamic boundary conditions using a pressure distribution over steep crests, as defined by Jeffreys＇ sheltering mechanism.A boundary value problem is solved by a higher-order boundary element method（HOBEM） and a mixed Eulerian-Lagrangian time marching scheme. The proposed model is validated through comparison with published experimental data from a focused wave group. The influence of wind on extreme wave properties,including maximum extreme wave crest, focal position shift, and spectrum evolution, is also studied. To consider the effects of the wind-driven currents on a wave evolution, the simulations assume a uniform current over varying water depth. The results show that wind causes weak increases in the extreme wave crest, and makes the nonlinear energy transfer non-reversible in the focusing and defocusing processes. The numerical results also provide a comparison to demonstrate the shifts at focal points, considering the combined effects of the winds and the wind-driven currents.
基金supported by the laboratory of silvopastoral resources (Silvopastoral Institute-Tabarka)
文摘The need for reforestation in cork oak （Quercus suber L.） areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings. We evaluated the early development of cork oak seedlings treated using tree shelters and mulching in northwestern Tunisia. We tested three tree shelter treatments （non-vented, vented, and control） to shield seedlings from animal damage and five mulch types to control competing vegetation （Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk （organic mulches）, gravel （inorganic mulch） and no mulch）. At the end of the two-year experiment, sheltered seedlings were 89-99% taller than unshelteredseedlings and had higher numbers and lengths of shoot growth flushes. In contrast, both stem diameter growth and dry weight biomass （from samples extracted after two years） were significantly reduced inside tree shelters. Root-to-shoot ratio was not significantly different in sheltered vs. unsheltered seedlings, suggesting that tree shelters do not adversely affect this parameter. Mulching alone did not favour growth, but could be beneficial when combined with tree shelters. The combination of vented tree shelters and gravel mulch was the most effective treatment for promoting diameter, height and stem volume growth.
基金National Natural＇Science Foundation of China, No.40401016
文摘Ecological shelter zones reconstruction is an ecosystem restoration and conservation project aimed to the ecological safety of nations, regions and basins. Reconstruction of ecological shelter zones of the upper reaches of the Yangtze River became one of the most important tasks of Western Development strategy. This article, taking Zhaotong as an example, studies the functional regionalization of ecological shelter zones. The study supplies a case for functional regionalization of small and medium regions whose main tasks are environment reservation. With the guidance of theories of functional regionalization, and based on the analysis of Zhaotong＇s natural, ecological and socioeconomic factors, the paper suggests five principles for factors selection. These principles include： （1） reversing order evaluation; （2） selecting main factors; （3） keeping the integrality of administrative regions of towns; and （4） making the products acceptable by local government. To analyze spatial status of selected factors, LUCC data in 2002, 1：50,000 relief maps and town-unit socioeconomic statistical data in 2004 are used. RS and GIS tools are also applied to melt traditional and modern geographical methods. This would be useful to functional regionalization research in mountainous areas. As a conclusion, the leading functional regions of ecological conservation or economic development are suggested, respectively. Zhaotong city is divided into two-level functional regions. The first-level includes three leading functional regions and they will lead developing direction of sub-regions. The second-level includes eight sub-regions, which are policy implemented regions, and will supply guidance to Zhaotong＇s ecological shelter zones reconstruction.
基金supported by the Soil and Water Conservation Bureau,Council of Agriculture,and National Basic Research Program of China (2008CB425802)
文摘Following the Chichi Earthquake （ML=7.3） in 1999, sediment-related disasters, such as landslides and debris flows, have become more frequent in Taiwan. Because engineering structures cannot be fully and rapidly emplaeed, the government has initiated non-structural hazard mitigation programs. Initially, community debris flow evacuation drills were promoted in 2000. Typhoon Toraji caused numerous debris flow events in July 2001, and some communities evacuated according to the drills, significantly reducing the numbers of possible casualties. Based on that result, the government expanded the program for evacuation drills. Secondly, the early warning system created after the Chichi Earthquake will prevent many potential future casualties. Rainfall threshold values for debris flow warnings in different areas are determined from information received from local weather stations and modified for local geomorphologic situations. Real- time information is gradually being integrated to create a debris flow disaster warning system, the goal of which is to provide warnings to zones in which debris flows are likely. The warning system was launched in 2005 and has two levels of alarms： yellow and red. The final, red alarm triggers enforced evacuation. Overall, the decrease in casualties from debris flows during the decade after the Chichi Earthquake is not the result of a decrease in number or severity of sediment related disasters, but is more directly related to the gradually improved early warning and evacuation system. However, the compound hazards resulting from Typhoon Morakotin 2009 remind us of the ongoing need for improving the existing mitigation system.
基金This research was supported by the Major Science and Technology Projects of Inner Mongolia Autonomous Region of China(zdzx2018058-3)the National Key Research and Development Project of China(2016YFC0500906-3)the Scientific and Technological Innovation Guiding Fund Project of Inner Mongolia Autonomous Region of China(R&D and Demonstration of Ecological Deserticulture Technology of Solar Photovoltaic Power Station in Sand Area)and the Scientific Research Project of Universities in Inner Mongolia Autonomous Region of China(NJZY19052).
文摘Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by surface erosion that may occur after the construction of the solar PVpower station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary toinvestigate the characteristics of wind-sand movement under the interference of solar PV array. The studywas undertaken by measuring sediment transport of different wind directions above shifting dunes andthree observation sites around the PV panels in the Hobq Desert, China. The results showed that the twoparameterexponential function provides better fit for the measured flux density profiles to the near-surfaceof solar PV array. However, the saltation height of sand particles changes with the intersection anglebetween the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting duneswas always the greatest, while that around the test PV panels varied accordingly to the wind direction.Moreover, the aeolian sediment transport on the solar PV array was significantly affected by wind direction.The value of sand inhibition rate ranged from 35.46% to 88.51% at different wind directions. When theintersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reducesto 82.58% compared with the shifting dunes. The results of our study expand our understanding of theformation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the designand control engineering plans for solar PV array in sandy areas that operate according to the wind regime.
基金Under the auspices of the Fund Project of Ministry of Science and Technology of the People's Republic of China (No.2005BA807B05)
文摘Sustainable livelihood theory provides a comprehensive framework for understanding the interactions between livelihoods of peasant households and regional environment change in low-income areas. Based on field survey and 946 questionnaires from peasant household conducted in the case study area of Zhaotong, Yunnan Province, the paper has analyzed the basic characteristics of the rural livelihoods, including the asset base status, the income-generating activities, the energy consumption pattern, and the fertility behavior, in the upper reaches of the Changjiang (Yangtze) River. The micro-level findings show the conflicts among extensive agricultural development models, rural energy consumption structures heavily relying on biomass and the environment protection. The conversion of cropland to forest and grass program(CCFGP) has exerted an important influence on the livelihoods of the peasant households, but its design has given little considerations to their long-term livelihood sources, which will affect its sustainability to a great extent. From the perspective of sustainable livelihoods framework, the objectives that must be addressed in the ecological shelter construction in the upper reaches of the Changjiang River should include, first, facilitating access of peasant households to credit, technology and public services, second, encouraging the peasant households to adopt agricultural technology with environmental benefits and strengthen resources-conserving investments, and third, paying close attention to the rural energy problems and the long-term livelihood sources of the households with CCFGP. Given the weak asset base and difficulties of livelihood strategies shift, ecological shelter construction in the upper reaches of the Changjiang River will take a long time.
基金funding from the Knowledge Innovation Project of the Chinese Academy of Science(KZCX2-YW-329)the National Natural Science Foundation of China (40638038)
文摘Porosity is the most important parameter determining the shelter efficiency of fences. Wind measurements were made around fence models with different porosities in a wind tunnel. The optimal fence porosity is evaluated by means of Gandemer＇s method that combines the effects of wind reduction and turbulence fields on the shelter efficiency for abating wind erosion. Defining the optimal porosity must take into account of its own purposes, required shelter degree and area to be sheltered. Turbulence has profound impacts on the shelter efficiency of high degree. Two concepts： absolute optimal porosity and practical optimal porosity concerning optimal porosity are proposed. Choosing the practical optimal porosity means reducing cost without significant expense of shelter efficiency. According to the evaluation in present study, the absolute optimal porosity for providing high degree of shelter to abate wind erosion is 0.20 while the practical optimal porosity is around 0.40. Ifa less shelter degree but over wider area is required, the absolute optimal porosity ranges from 0.05 to 0.10 and the practical optimal porosity is 0.10. For any degree of shelter for abating wind erosion effectively, the fence porosity must be less than or equal 0.40.
基金provided by the National Natural Science Foundation of China(No.31772486)the Hainan Provincial Natural Science Foundation of China (No.319MS047)。
文摘Rock crevices are important retreat sites for many reptiles.Unlike lizards and snakes,crevicedwelling turtles have rigid shells which severely limit the size and shape of crevices they are able to use.Few studies have addressed the relationship between turtle's shell morphology,behavior,and crevice size.Here,we investigate the relationship between morphology and crevice size selection in the Keeled box turtle(Cuora mouhotii).We radio tracked turtles in the field to document crevice dimensions and turtle behavior associated with crevices,and we conducted a controlled experiment in the lab to understand how a turtle's morphology influences its decision to select crevices with different dimensions.Both laboratory and field experiments demonstrate that turtles select deep and moderately wide crevices that are low enough to barely accommodate the carapace.Crevices used by turtles tend to be about 2 times as wide,1.2 times as high,and 3 times longer than the turtle's shell.Moreover,turtles tended to prefer crevices with horizontal openings in the field and position themselves head first in the crevice.We conclude that morphology,especially carapace height,influences the Keeled box turtles' decision to select specific sizes of crevice.We argue that the tendency for turtles to select crevices that come into contact with their carapace contributes to successful defense against predators,as it would be more difficult for a predator to remove a turtle when the crevice is nearly touching the turtles shell.
基金supported by the National Natural Science Foundation of China(Nos.32271846,31400613)the Key Program of Education Department of Liaoning Province(No.LJKZZ20220050).
文摘In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.
基金supported by the Medicine and Technology Development Plan Project of Shandong Province(2016WS0119)
文摘Carbon monoxide （CO） is an odorless, colorless gas produced by incomplete combustion of carbonbased compounds. Exposure to CO can cause various adverse health effects ranging from headache and fatigue to coma and death. Thousands of illnesses and deaths have been documented through CO poisoning surveillance systems and accident investigations each year.
