This paper introduces the general process of the search algorithm Structure through the knight problem. According to the characteristics of the problem, we detailed discuss the DFS（Depth First Search） algorithm and ...This paper introduces the general process of the search algorithm Structure through the knight problem. According to the characteristics of the problem, we detailed discuss the DFS（Depth First Search） algorithm and BFS（Breadth First Search） algorithm, and combine the two algorithms together to solve the knights coverage problem. This article has a good reference for the mixed-use scenarios which requires a variety of search algorithms.展开更多
In the upcoming exa-scale era, the exploitation of data locality in parallel programs is very important because it benefits both program performance and energy efficiency. However, this is a hard topic for graph algor...In the upcoming exa-scale era, the exploitation of data locality in parallel programs is very important because it benefits both program performance and energy efficiency. However, this is a hard topic for graph algorithms such as the Breadth First Search （BFS） due to the irregular data access patterns. This study analyzes the exploitation of data locality in the BFS and its impact on the energy efficiency with the Codelet fine-grain dataflow-inspired execution model. The Codelet Model more efficiently exploits data locality than the OpenMP-like execution models which traditionally focus on coarse-grain parallelism inside loops. A BFS algorithm is then given to exploit the locality between two loop iterations that belong to two different loops （inter-loop locality）. This kind of locality can be exploited by the Codelet Model but not by traditional coarse-grain execution models like OpenMR Tests were performed on fsim which is a simulation platform developed by Intel for the Ubiquitous High Performance Computing （UHPC） project to design future exa-scale architectures. The results show that this BFS algorithm saves up to 7% of the dynamic energy for memory accesses compared to a BFS implementation based on OpenMP loop scheduling.展开更多
The advantage of Chinese-as-a-heritage-language(CHL)learners in acquiring Chinese has been widely recognized.However,it is still unclear whether the effect of CHL background on Chinese receptive vocabulary breadth var...The advantage of Chinese-as-a-heritage-language(CHL)learners in acquiring Chinese has been widely recognized.However,it is still unclear whether the effect of CHL background on Chinese receptive vocabulary breadth varies across different countries.To address this gap,the present study recruited 232 Chinese language learners(half were CHL learners)from Indonesia and Thailand and administered a Chinese vocabulary proficiency test.The results of regression analysis revealed an interaction effect between country and CHL background on vocabulary breadth,with the contribution of CHL background to vocabulary breadth more robust in the Indonesian group than that in the Thai group.Interviews were then conducted to explore the factors that might influence such an interaction effect.Analysis of the interview data found that the influencing factors could be categorized into four themes,including individual differences,family background,Chinese language education and socio-cultural factors.The overall results were discussed within the framework of ecological system theory,and pedagogical implications for CHL learners were proposed.展开更多
We obtai ned geo-refere need occurre nee and climatic data from in dividual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cla...We obtai ned geo-refere need occurre nee and climatic data from in dividual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cladistic patter ns of variation in climatic niche breadths, and compared patter ns within and across regions and clades to see if they parallel or differ from each other. Specifically, we test (1) whether a species' climatic niche breadth on a given niche axis relates to its position along that axis, and to its climatic niche breadth on another niche axis, and (2) whether variation in niche breadths among species is explained by within-locality variation in climatic conditions or by among-locality variation. We found that:(1) there is an overall global patter n, and patter ns in individual regi ons or clades gen erally parallel each other and global patter ns;(2) species in wanner environments have narrower temperature niche breadths (TNBs);(3) precipitation niche breadth (PNB) and position are positively related;⑷ TNB and PNB are not related;and ⑸ within-locality variation in climatic conditions explains most variation in TNBs, whereas among-locality variation explains most variation in PNBs. Our results are consistent with those reported for lizards of the families Phrynosomatidae and Varanidae, con firm the importance of withi n-locality n iche breadth to species n iche breadth, and show a more im porta nt role of amon g-locality n iche breadth in affecting species niche breadth in terrestrial elapids than in lizards.展开更多
The resonant motion of the fluid inside a narrow gap between two fixed boxes induced by incident regular waves with various wave heights is investigated by adopting a two-dimensional numerical wave flume based on an o...The resonant motion of the fluid inside a narrow gap between two fixed boxes induced by incident regular waves with various wave heights is investigated by adopting a two-dimensional numerical wave flume based on an opensourced CFD package,OpenFOAM.The two boxes have identical draft and height,but the upstream box has a variable breadth.This article focuses on the influences of the breadth ratio,defined as the ratio of the breadth of the upstream box to that of the downstream box,on the following three aspects of hydrodynamic characteristics of gap resonance:(1)the wave height amplifications inside the gap,and in front and at the rear of the structure system,(2)the reflection,transmission,and energy loss coefficients of the structure system,and(3)the response and damping time of the fluid resonance.It is found that the fluid resonant frequency,the amplification factor of the resonant wave height inside the gap and the maximum energy loss coefficient of the structure system are shown to gradually decrease with the increase of the breadth ratio.The response time of gap resonance is shown to first increase and then decrease with the breadth ratio overall,regardless of the incident wave height,and the configuration that the two boxes have the same breadth would bring the largest response time of gap resonance.展开更多
Measuring climatic niche position and breadth may help to determine where species can occur over space and time. Using GIS-based and phylogenetic comparative methods, we investigated global patterns of variation in cl...Measuring climatic niche position and breadth may help to determine where species can occur over space and time. Using GIS-based and phylogenetic comparative methods, we investigated global patterns of variation in climatic niche breadth in lacertid lizards to test the following three hypotheses about climatic niche widths. First, does a species' temperature or precipitation niche breadth relate to its temperature or precipitation niche position(the mean value of annual mean temperature or annual precipitation across sampled localities in the range of each species)? Second, are there trade-offs between a species' temperature niche breadth and precipitation niche breadth? Third, does a species' temperature or precipitation niche breadth relate to altitude or latitude? We expect that:(1) species distributed in cold regions are specialized for low-temperature environments(i.e. narrow niche breadth center around low temperatures);(2) a negative relationship between species niche breadth on temperature and precipitation axes according to the tradeoff hypothesis(i.e. species that tolerate a broad range of precipitation regimes cannot also tolerate a broad range of temperatures);(3) precipitation niche breadth decreases with altitude or latitude, whereas temperature climatic niche breadth increases with altitude or latitude. Based on the analytical results we found that:(1) temperature niche breadth and position are negatively related, while precipitation niche breadth and position are positively related;(2) there is no trade-off between temperature and precipitation niche breadths; and (3) temperature niche breadth and latitude/altitude are positively related, but precipitation niche breadth and latitude/altitude are not significantly related. Our results show many similarities with previous studies on climatic niche widths reported for amphibians and lizards, which provide further evidence that such macroecological patterns of variation in climatic niche breadths may be widespread.展开更多
The design solutions for breadth cam mechanism was presented. The main topics of the shape design for breadth cam was to calculate the coordinate at each contact point to determine the cam profile. The proposed method...The design solutions for breadth cam mechanism was presented. The main topics of the shape design for breadth cam was to calculate the coordinate at each contact point to determine the cam profile. The proposed method according to velocity and geometric relationships of instant velocity centers can easily determine each contact point at any instant moment. The cam profile was defined by contouring of the contact points. And also a program was developed by using Microsoft Visual C++ program,which can quickly and easily draw a 2D cam profile through the displacement diagram. Finally,the program was used to confirm the accuracy on the breadth cam profile design by computer animation graphically.展开更多
The defense in depth methodology was popularized in the early 2000’s amid growing concerns for information security;this paper will address the shortcomings of early implementations. In the last two years, many suppo...The defense in depth methodology was popularized in the early 2000’s amid growing concerns for information security;this paper will address the shortcomings of early implementations. In the last two years, many supporters of the defense in depth security methodology have changed their allegiance to an offshoot method dubbed the defense in breadth methodology. A substantial portion of this paper’s body will be devoted to comparing real-world usage scenarios and discussing the flaws in each method. A major goal of this publication will be to assist readers in selecting a method that will best benefit their personal environment. Scenarios certainly exist where one method may be clearly favored;this article will help identify the factors that make one method a clear choice over another. This paper will strive not only to highlight key strengths and weaknesses for the two strategies listed, but also provide the evaluation techniques necessary for readers to apply to other popular methodologies in order to make the most appropriate personal determinations.展开更多
Accurate information on the thermal preference and specialization of species is needed to understand and predict spe- cies geographical range size and vulnerability to climate change. Here we estimate the position and...Accurate information on the thermal preference and specialization of species is needed to understand and predict spe- cies geographical range size and vulnerability to climate change. Here we estimate the position and breadth of species within thermal gradients based on the shape of the response curve of species abundance to temperature. The objective of the study is to compare the measurements of this approach based on abundance data with those of the classical approach using species＇ occur- rence data. The relationship between species＇ relative abundance and minimum winter temperature of 106 bird species wintering in the Iberian Peninsula is modeled at 100 Km2 resolution with quadratic logistic regressions. From these models we calculated the preferred temperature of species as the temperature at which the abundance is maximized, and the thermal breadth of species as the relative area under the temperature-abundance curve. We also estimated the thermal preferences and breadth of species as the average temperature and temperature range of the UTM cells in which the species are present. The abundance-temperature response curves reveal that birds prefer higher temperatures to overwinter, and are more thermally selective, than is measured by the classical approach. Moreover, response curves detect a higher inter-specific variability in both thermal preferences and ther- mal breadth of species. As occurrence data gives the same weight to cells with one or many individuals, the average temperature of the cells in which the species is present roughly reflects the average temperature in the region of study and not the environ- mental preferences of species .展开更多
China's rapid economic development leads to a series of environmental problems in the long run,such as air pollution.Environmental pollution has become a bottleneck restricting the sustainable development of China...China's rapid economic development leads to a series of environmental problems in the long run,such as air pollution.Environmental pollution has become a bottleneck restricting the sustainable development of China's economy.As such,pollution has become a key issue for China as让tries to continuously improve environmental quality and establish a harmonious coexistence between man and nature.This paper uses spatial econometric analysis to empirically test the existence of the Environmental Kuznets Curve(EKC)in China while also examining the impact of financial development on its inflection point by applying Air Quality Index and PM_(2.5) data of 283 prefecture-level cities in China from 2015 to 2017.Findings from this study indicate that the EKC of air pollution in the whole country presents an inverted U-shape based on both the traditional and new EKC models.After testing the sub-sample in different areas,the EKC still presents an inverted U-shape based on the new EKC model in the eastern and central areas,though not in the western area.In considering the moderating role of financial development based on the new EKC model,we find that the increase of financial depth will cause the EKC inflection point to shift to the left on the national scale and in the eastern region,while the effect of the financial breadth will be largely insignificant.With regard to the central area,both the breadth and the depth of financial development will significantly shift the inflection point to the right,delaying the arrival of the EKC inflection point.Therefore,the local authority of each area should formulate differentiated financial development policies to promote the early arrival of the EKC inflection point.展开更多
The Second Belt and Road Forum of International Cooperation was held in Beijing in late April. Thousands of representatives from more than 100 countries around the world discussed new strategies for achieving high-qua...The Second Belt and Road Forum of International Cooperation was held in Beijing in late April. Thousands of representatives from more than 100 countries around the world discussed new strategies for achieving high-quality development of the Belt and Road Initiative (BRI) and shared cooperation experience.展开更多
Many small Parks inKenyaare being fenced to control human-wildlife conflict. Some of these Parks have a diversity of large herbivores which might increase in density in the wake of fencing and subsequent compression o...Many small Parks inKenyaare being fenced to control human-wildlife conflict. Some of these Parks have a diversity of large herbivores which might increase in density in the wake of fencing and subsequent compression of their home ranges due to closure of their migratory routes. It is important to understand the consequences of such an increase on the structuring of insularised herbivore assemblages in such Parks. We studied seasonal resource segregation and niche breadth variation as mechanisms of coexistence in a high density grazer assemblage inLakeNakuruNational Parkwhich is small and completely fenced. Diet composition and habitat use were considered as variables of resource use. We predicted that overlap in resource use and niche breadth would be the smallest among grazers with similar body weights in the dry season which is the most resource limiting for grazers in East Africa. Our results were contrary to the predictions because of lack of seasonal differentiation in the overlap of diet composition and habitat use, and in niche breadth. Overlaps in resource use were consistently high during both the wet and dry seasons, and niche breadth contraction during the dry season was not possible probably because of lack of species-specific niches during the dry season. Our results suggest that there might be competitive interactions in this grazer assemblage which is an important parameter to consider in the management of the Park.展开更多
图是一种非常重要的数据结构形式,被广泛用于社交网络、交通网络和搜索引擎等领域。随着图数据规模爆发式增长,存储容量受限,分布式图计算成为处理大规模图数据的焦点。宽度优先搜索(breadth first search,BFS)算法是图遍历和许多图分...图是一种非常重要的数据结构形式,被广泛用于社交网络、交通网络和搜索引擎等领域。随着图数据规模爆发式增长,存储容量受限,分布式图计算成为处理大规模图数据的焦点。宽度优先搜索(breadth first search,BFS)算法是图遍历和许多图分析算法的基础,而在分布式图计算过程中存在严重的通信开销。针对上述问题,本文提出了一种综合的数据压缩编码优化方案,结合位图和变长压缩数组,通过更高的压缩率来降低数据通信开销;此外,还提出了一种点对点异步环形通信策略,进一步降低分布式图计算中计算-通信的同步开销。通过这些优化手段,本文在8节点的分布式集群上对优化后BFS算法的性能进行了系统评估,结果表明,当图数据规模为28时,优化后的BFS算法平均性能为46.79亿条边每秒遍历(giga-traversed edges per second,GTEPS),性能比优化前提升了接近7.82%。展开更多
针对当前CATIA软件存在三维公差标注功能操作繁琐、费时费力的问题,提出基于MBD(Model Based Definition)模型的三维尺寸公差自动标注方法。采用改进的广度优先搜索算法完整地遍历三维零件的结构树信息,分层访问所有的特征结构,获取包...针对当前CATIA软件存在三维公差标注功能操作繁琐、费时费力的问题,提出基于MBD(Model Based Definition)模型的三维尺寸公差自动标注方法。采用改进的广度优先搜索算法完整地遍历三维零件的结构树信息,分层访问所有的特征结构,获取包含于技术产品规范特征中的三维标注信息模块,通过筛选过滤提取尺寸标注信息;根据DT(Dimension-Tolerance)特征匹配公差信息,构建尺寸公差模型;通过CAA的二次开发接口,开发相应的功能模块,实现三维零件尺寸公差的自动标注。通过实例证明,该方法可以在三维零件设计时快速高效地提取所有三维尺寸标注信息,并实现三维环境下尺寸公差的自动标注。展开更多
文摘This paper introduces the general process of the search algorithm Structure through the knight problem. According to the characteristics of the problem, we detailed discuss the DFS（Depth First Search） algorithm and BFS（Breadth First Search） algorithm, and combine the two algorithms together to solve the knights coverage problem. This article has a good reference for the mixed-use scenarios which requires a variety of search algorithms.
基金National Science Foundation of USA(Nos.CCF-0833122,CCF-0925863,CCF-0937907,CNS-0720531,and OCI-0904534)supported by the Department of Energy(National Nuclear Security Administration)under the Award Number DE-SC0008717.Moreoverpartly supported by European FP7 project TERAFLUX,id.249013
文摘In the upcoming exa-scale era, the exploitation of data locality in parallel programs is very important because it benefits both program performance and energy efficiency. However, this is a hard topic for graph algorithms such as the Breadth First Search （BFS） due to the irregular data access patterns. This study analyzes the exploitation of data locality in the BFS and its impact on the energy efficiency with the Codelet fine-grain dataflow-inspired execution model. The Codelet Model more efficiently exploits data locality than the OpenMP-like execution models which traditionally focus on coarse-grain parallelism inside loops. A BFS algorithm is then given to exploit the locality between two loop iterations that belong to two different loops （inter-loop locality）. This kind of locality can be exploited by the Codelet Model but not by traditional coarse-grain execution models like OpenMR Tests were performed on fsim which is a simulation platform developed by Intel for the Ubiquitous High Performance Computing （UHPC） project to design future exa-scale architectures. The results show that this BFS algorithm saves up to 7% of the dynamic energy for memory accesses compared to a BFS implementation based on OpenMP loop scheduling.
基金supported by National Social Science Fund of China(No.24BYY048)International Chinese Language Education Research Program(No.23YH17B)Fundamental Research Funds for the Central Universities(No.23JNLH10)。
文摘The advantage of Chinese-as-a-heritage-language(CHL)learners in acquiring Chinese has been widely recognized.However,it is still unclear whether the effect of CHL background on Chinese receptive vocabulary breadth varies across different countries.To address this gap,the present study recruited 232 Chinese language learners(half were CHL learners)from Indonesia and Thailand and administered a Chinese vocabulary proficiency test.The results of regression analysis revealed an interaction effect between country and CHL background on vocabulary breadth,with the contribution of CHL background to vocabulary breadth more robust in the Indonesian group than that in the Thai group.Interviews were then conducted to explore the factors that might influence such an interaction effect.Analysis of the interview data found that the influencing factors could be categorized into four themes,including individual differences,family background,Chinese language education and socio-cultural factors.The overall results were discussed within the framework of ecological system theory,and pedagogical implications for CHL learners were proposed.
基金the Natural Science Foundation of Zhejiang Province to L.-H.L.(LY17C030003)National Natural Science Foundation of China to X.J.(31272294 and 30770378).
文摘We obtai ned geo-refere need occurre nee and climatic data from in dividual localities for 59 species of terrestrial elapid snakes, used phylogenetic generalized least squares regression to investigate spatial and cladistic patter ns of variation in climatic niche breadths, and compared patter ns within and across regions and clades to see if they parallel or differ from each other. Specifically, we test (1) whether a species' climatic niche breadth on a given niche axis relates to its position along that axis, and to its climatic niche breadth on another niche axis, and (2) whether variation in niche breadths among species is explained by within-locality variation in climatic conditions or by among-locality variation. We found that:(1) there is an overall global patter n, and patter ns in individual regi ons or clades gen erally parallel each other and global patter ns;(2) species in wanner environments have narrower temperature niche breadths (TNBs);(3) precipitation niche breadth (PNB) and position are positively related;⑷ TNB and PNB are not related;and ⑸ within-locality variation in climatic conditions explains most variation in TNBs, whereas among-locality variation explains most variation in PNBs. Our results are consistent with those reported for lizards of the families Phrynosomatidae and Varanidae, con firm the importance of withi n-locality n iche breadth to species n iche breadth, and show a more im porta nt role of amon g-locality n iche breadth in affecting species niche breadth in terrestrial elapids than in lizards.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.52371277 and 52001071)the State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation (Tianjin University) (Grant No.HESS-2323)+1 种基金the Postgraduate Research&Practice Innovation Program of Jiangsu Province (Grant No.KYCX23_3902)the Guangdong Basic and Applied Basic Research Foundation (Grant No.:2023A1515010890)。
文摘The resonant motion of the fluid inside a narrow gap between two fixed boxes induced by incident regular waves with various wave heights is investigated by adopting a two-dimensional numerical wave flume based on an opensourced CFD package,OpenFOAM.The two boxes have identical draft and height,but the upstream box has a variable breadth.This article focuses on the influences of the breadth ratio,defined as the ratio of the breadth of the upstream box to that of the downstream box,on the following three aspects of hydrodynamic characteristics of gap resonance:(1)the wave height amplifications inside the gap,and in front and at the rear of the structure system,(2)the reflection,transmission,and energy loss coefficients of the structure system,and(3)the response and damping time of the fluid resonance.It is found that the fluid resonant frequency,the amplification factor of the resonant wave height inside the gap and the maximum energy loss coefficient of the structure system are shown to gradually decrease with the increase of the breadth ratio.The response time of gap resonance is shown to first increase and then decrease with the breadth ratio overall,regardless of the incident wave height,and the configuration that the two boxes have the same breadth would bring the largest response time of gap resonance.
基金Financial support was provided by grants from Zhejiang Provincial Natural Science Foundation (LY17C030003)Natural Science Foundation of China (31270571)Science and Technology Bureau of Sanya (2013YD08)
文摘Measuring climatic niche position and breadth may help to determine where species can occur over space and time. Using GIS-based and phylogenetic comparative methods, we investigated global patterns of variation in climatic niche breadth in lacertid lizards to test the following three hypotheses about climatic niche widths. First, does a species' temperature or precipitation niche breadth relate to its temperature or precipitation niche position(the mean value of annual mean temperature or annual precipitation across sampled localities in the range of each species)? Second, are there trade-offs between a species' temperature niche breadth and precipitation niche breadth? Third, does a species' temperature or precipitation niche breadth relate to altitude or latitude? We expect that:(1) species distributed in cold regions are specialized for low-temperature environments(i.e. narrow niche breadth center around low temperatures);(2) a negative relationship between species niche breadth on temperature and precipitation axes according to the tradeoff hypothesis(i.e. species that tolerate a broad range of precipitation regimes cannot also tolerate a broad range of temperatures);(3) precipitation niche breadth decreases with altitude or latitude, whereas temperature climatic niche breadth increases with altitude or latitude. Based on the analytical results we found that:(1) temperature niche breadth and position are negatively related, while precipitation niche breadth and position are positively related;(2) there is no trade-off between temperature and precipitation niche breadths; and (3) temperature niche breadth and latitude/altitude are positively related, but precipitation niche breadth and latitude/altitude are not significantly related. Our results show many similarities with previous studies on climatic niche widths reported for amphibians and lizards, which provide further evidence that such macroecological patterns of variation in climatic niche breadths may be widespread.
基金Work supported by the Second Stage of Brain Korea 21 Projects
文摘The design solutions for breadth cam mechanism was presented. The main topics of the shape design for breadth cam was to calculate the coordinate at each contact point to determine the cam profile. The proposed method according to velocity and geometric relationships of instant velocity centers can easily determine each contact point at any instant moment. The cam profile was defined by contouring of the contact points. And also a program was developed by using Microsoft Visual C++ program,which can quickly and easily draw a 2D cam profile through the displacement diagram. Finally,the program was used to confirm the accuracy on the breadth cam profile design by computer animation graphically.
文摘The defense in depth methodology was popularized in the early 2000’s amid growing concerns for information security;this paper will address the shortcomings of early implementations. In the last two years, many supporters of the defense in depth security methodology have changed their allegiance to an offshoot method dubbed the defense in breadth methodology. A substantial portion of this paper’s body will be devoted to comparing real-world usage scenarios and discussing the flaws in each method. A major goal of this publication will be to assist readers in selecting a method that will best benefit their personal environment. Scenarios certainly exist where one method may be clearly favored;this article will help identify the factors that make one method a clear choice over another. This paper will strive not only to highlight key strengths and weaknesses for the two strategies listed, but also provide the evaluation techniques necessary for readers to apply to other popular methodologies in order to make the most appropriate personal determinations.
文摘Accurate information on the thermal preference and specialization of species is needed to understand and predict spe- cies geographical range size and vulnerability to climate change. Here we estimate the position and breadth of species within thermal gradients based on the shape of the response curve of species abundance to temperature. The objective of the study is to compare the measurements of this approach based on abundance data with those of the classical approach using species＇ occur- rence data. The relationship between species＇ relative abundance and minimum winter temperature of 106 bird species wintering in the Iberian Peninsula is modeled at 100 Km2 resolution with quadratic logistic regressions. From these models we calculated the preferred temperature of species as the temperature at which the abundance is maximized, and the thermal breadth of species as the relative area under the temperature-abundance curve. We also estimated the thermal preferences and breadth of species as the average temperature and temperature range of the UTM cells in which the species are present. The abundance-temperature response curves reveal that birds prefer higher temperatures to overwinter, and are more thermally selective, than is measured by the classical approach. Moreover, response curves detect a higher inter-specific variability in both thermal preferences and ther- mal breadth of species. As occurrence data gives the same weight to cells with one or many individuals, the average temperature of the cells in which the species is present roughly reflects the average temperature in the region of study and not the environ- mental preferences of species .
基金the financial support of the Humanities and Social Science Foundation of the Chinese Ministry of Education[Grant num-ber.20YJC630104]the National Natural Science Foundation of China[Grant number.71403120,Grant number.72003157]+1 种基金the National Social Science Foundation of China[Grant number.18ZDA052,Grant number.19ZDA074)the Fundamental Research Funds for the Central Universities[Grant number.JBK2002017].
文摘China's rapid economic development leads to a series of environmental problems in the long run,such as air pollution.Environmental pollution has become a bottleneck restricting the sustainable development of China's economy.As such,pollution has become a key issue for China as让tries to continuously improve environmental quality and establish a harmonious coexistence between man and nature.This paper uses spatial econometric analysis to empirically test the existence of the Environmental Kuznets Curve(EKC)in China while also examining the impact of financial development on its inflection point by applying Air Quality Index and PM_(2.5) data of 283 prefecture-level cities in China from 2015 to 2017.Findings from this study indicate that the EKC of air pollution in the whole country presents an inverted U-shape based on both the traditional and new EKC models.After testing the sub-sample in different areas,the EKC still presents an inverted U-shape based on the new EKC model in the eastern and central areas,though not in the western area.In considering the moderating role of financial development based on the new EKC model,we find that the increase of financial depth will cause the EKC inflection point to shift to the left on the national scale and in the eastern region,while the effect of the financial breadth will be largely insignificant.With regard to the central area,both the breadth and the depth of financial development will significantly shift the inflection point to the right,delaying the arrival of the EKC inflection point.Therefore,the local authority of each area should formulate differentiated financial development policies to promote the early arrival of the EKC inflection point.
文摘The Second Belt and Road Forum of International Cooperation was held in Beijing in late April. Thousands of representatives from more than 100 countries around the world discussed new strategies for achieving high-quality development of the Belt and Road Initiative (BRI) and shared cooperation experience.
基金Kenya Wildlife Service for giving permission to conduct this study in Lake Nakuru National Park,and to the Netherlands Organisation for International Cooperation in Higher Education(NUFFIC)for funding the study
文摘Many small Parks inKenyaare being fenced to control human-wildlife conflict. Some of these Parks have a diversity of large herbivores which might increase in density in the wake of fencing and subsequent compression of their home ranges due to closure of their migratory routes. It is important to understand the consequences of such an increase on the structuring of insularised herbivore assemblages in such Parks. We studied seasonal resource segregation and niche breadth variation as mechanisms of coexistence in a high density grazer assemblage inLakeNakuruNational Parkwhich is small and completely fenced. Diet composition and habitat use were considered as variables of resource use. We predicted that overlap in resource use and niche breadth would be the smallest among grazers with similar body weights in the dry season which is the most resource limiting for grazers in East Africa. Our results were contrary to the predictions because of lack of seasonal differentiation in the overlap of diet composition and habitat use, and in niche breadth. Overlaps in resource use were consistently high during both the wet and dry seasons, and niche breadth contraction during the dry season was not possible probably because of lack of species-specific niches during the dry season. Our results suggest that there might be competitive interactions in this grazer assemblage which is an important parameter to consider in the management of the Park.
文摘图是一种非常重要的数据结构形式,被广泛用于社交网络、交通网络和搜索引擎等领域。随着图数据规模爆发式增长,存储容量受限,分布式图计算成为处理大规模图数据的焦点。宽度优先搜索(breadth first search,BFS)算法是图遍历和许多图分析算法的基础,而在分布式图计算过程中存在严重的通信开销。针对上述问题,本文提出了一种综合的数据压缩编码优化方案,结合位图和变长压缩数组,通过更高的压缩率来降低数据通信开销;此外,还提出了一种点对点异步环形通信策略,进一步降低分布式图计算中计算-通信的同步开销。通过这些优化手段,本文在8节点的分布式集群上对优化后BFS算法的性能进行了系统评估,结果表明,当图数据规模为28时,优化后的BFS算法平均性能为46.79亿条边每秒遍历(giga-traversed edges per second,GTEPS),性能比优化前提升了接近7.82%。
文摘针对当前CATIA软件存在三维公差标注功能操作繁琐、费时费力的问题,提出基于MBD(Model Based Definition)模型的三维尺寸公差自动标注方法。采用改进的广度优先搜索算法完整地遍历三维零件的结构树信息,分层访问所有的特征结构,获取包含于技术产品规范特征中的三维标注信息模块,通过筛选过滤提取尺寸标注信息;根据DT(Dimension-Tolerance)特征匹配公差信息,构建尺寸公差模型;通过CAA的二次开发接口,开发相应的功能模块,实现三维零件尺寸公差的自动标注。通过实例证明,该方法可以在三维零件设计时快速高效地提取所有三维尺寸标注信息,并实现三维环境下尺寸公差的自动标注。
