To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ...To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ＂Home of Vegetables＂. The N2O fluxes were observed in four experimental treatments, as follows： none N fertilizer （CK）, single organic fertilizer （OM）, conventional fertilization （FP） and opti- mized and reduced nitrogen fertilization （OPT）, by a close chamber-gas chromato- graph method. The effects of different fertilization treatments on N2O emission and tomato yield were analyzed. The results showed that following the fertilization and ir- rigation, the pulsed emissions of N2O were measured. The N2O emission peak ap- peared after basal fertilizer application and irrigation and could be maintained for about 20 days. While the N2O emission peak caused by topdressing was smaller and last only 3-5 days. The statistical analysis showed that the N2O fluxes were affected by air temperature, soil temperature and WFPS at soil depth of 3 cm. The total contents of soil N2O fluxes had significant differences among experimental groups. The total content orderly was FP of 14. 77 kg/hm^2, OPT of 9. 73 kg/hm^2, OM of 6.84 kg/hm^2 and CK of 2.37 kg/hm^2. The N~：~ emission coefficient ranged from 0.83%-1.10%,which was close to or more than the recommended value （1.0%） by IPCC. Compared with the FP treatment, the tomato yield in OPT treatment, whose application rate of chemical N fertilizer decreased by about 60%, increased by 2.2%. Under the current management measures, the reasonable reduction on ap- plicaUon rate of organic manure and chemical nitrogen fertilizer could effectively re- duce the N=O emissions in greenhouse vegetable fields.展开更多
This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum...This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum plate（180×120×3 nm^2）, which was covered by a transparent plate. The working fluid employed was ethanol. As the results, the influence parameters of thermal performance were investigated, such as filling ratio, heat load and operational orientations etc. Filling ratio was found to be a critical parameter, and its effect was rather complicated. According to its values the PHP plate could have four distinct working zones with different operational characteristics and heat transfer performance. The effect of heat load on thermal performance was found to be positive, and in general, iucrcasing the heat load would improve heat transfer performance. In order to analyze the effect of gravity on thermal performance, three different heat modes and total seven tilt angles were tested and compared. Successful operation at all orientations with respect to gravity was also achieved.展开更多
Based on the analysis of its basic characteristics, this article investigated the disparities of Chinese service industry among the three regions （the eastern China, the western China and the middle China） and inter...Based on the analysis of its basic characteristics, this article investigated the disparities of Chinese service industry among the three regions （the eastern China, the western China and the middle China） and inter-provincial disparities of that in the three regions by Theil coefficient and cluster analysis. Then, major factors influencing its spatial disparity were explored by correlation analysis and regression analysis. The conclusions could be drawn as follows. 1） The development of Chinese service industry experienced three phases since the 1980s： rapid growth period, slow growth period, and recovery period. From the proportion of value-added and employment, its development was obviously on the low level. From the composition of industrial structure, traditional service sectors were dominant, but modem service sectors were lagged. Moreover, its spatial disparity was distinct. 2） The level of Chinese service industry was divided into five basic regional ranks： well-developed, developed, relatively-developed, underdeveloped and undeveloped regions, As a whole, the overall structure of spatial disparity was steady in 1990-2005. But there was notable gradient disparity in the interior structure of service industry among different provinces. Furthermore, the overall disparity expanded rapidly in 1990-2005. The inter-provincial disparity of service industry in the three regions, especially in the eastern China, was bigger than the disparity among the three regions. And 3） the level of economic development, the level of urban development, the scale of market capacity, the level of transportation and telecommunication, and the abundance of human resources were major factors influencing the development of Chinese service industry.展开更多
[Objective] The morphological characters of C.lasiocarpa were studied to find its morphological responses to different water regimes and growth stretagies through different water experiences.[Method] A seeding transpl...[Objective] The morphological characters of C.lasiocarpa were studied to find its morphological responses to different water regimes and growth stretagies through different water experiences.[Method] A seeding transplanting experiment with controlled water levels was set up,and the water level was changed at the middle of the season to compare water influence at the seeding stage and later growing period.C.lasiocarpa height,leaf length,leaf number,rhizome and adventitious roots length were measured at certain time througth the growing season.[Result] Results at the thriving season indicated that C.lasiocarpa height and leaf length in the experiment were similar to that in the field,but leaf number was higher under-5 cm water level and dry-wet alternate conditions than that in the field.At later growth period,height and leaf length under constant flooding(15cm) was significantly higher than that under other culture conditions,and also that of the field investigation;while the leaf number had a trend as-5 cm water level treatment>constant flooding>dry-wet alternate>field investigation.The height and leaf length were sensitive to seeding stage water effects,and leaf number sensitive to later influences.[Conclusion] Changes of water regimes in the growing season disturbed the growth of C.lasiocarpa,could accelerate or suspend its wilt,and modified the length of life history.展开更多
To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in Apr...To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness (MA), species diversity (H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance (D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels (R = 0.55, p < 0.05), soil moisture (R = 0.53, p < 0.05), soil salinity (R = 0.43, p < 0.05) and reclamation time (R = 0.40, p < 0.05).展开更多
Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged p...Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged positions of drainage wells are mainly located at the thick clay layer in the low alluvium and the lithological interface in the upper section of bedrock in west mining area.The failure depth of casing is 244-670 m and concentrates at about 270-460 m deep.These damaged positions are mainly located in the bending zone according to three zones of rock layers in the vertical section above the roof divided. Generally,the casing begins to deform or damage before the face line about 30-150 m.Special formation structure and rock mass properties are the direct causes of the casing failure,high mining height and fast advancing speed are fundamental reasons for rock mass damage.However,the borehole configuration and spacing to the casing failure are not very clear.展开更多
Through the research on stress metamorphism character of the II1 coal seam in Ludian gliding structure, the stress effecting factors of metamorphism and hydrocarbon generation process of tectonic coal were studied. It...Through the research on stress metamorphism character of the II1 coal seam in Ludian gliding structure, the stress effecting factors of metamorphism and hydrocarbon generation process of tectonic coal were studied. It is shown that different tectonic stress has different coal evolution effects. Compared with tensional stress, compressive stress, which has apparent anisotropic characteristics, has greater stimulative effect against the increase of coal metamorphic degree, the abscission of functional group and side chains of basic structural unit, and the formation of gas primarily composed of methane.展开更多
Actual sandstone micromodel was used in this work to conduct the microscopic waterflooding experiment of ultra-low sandstone reservoir,since the inside seepage characteristics of microscopic waterflooding process of C...Actual sandstone micromodel was used in this work to conduct the microscopic waterflooding experiment of ultra-low sandstone reservoir,since the inside seepage characteristics of microscopic waterflooding process of Chang 8 ultra-low permeability sandstone reservoir of Upper Triassic Yanchang formation in Huaqing region of the Ordos Basin,China is difficult to observe directly.Combined with physical property,casting thin sections,constant-rate mercury injection capillary pressure and nuclear magnetic resonance,the influence of reservoir property on the waterflooding characteristics in pores were analyzed and evaluated.Seepage paths of waterflooding characteristics were divided into four types:homogeneous seepage,reticular-homogeneous seepage,finger-reticular seepage and finger-like seepage,the waterflooding efficiency of which decreases in turn.More than 70%of residual oil occurs as flowing-around seepage and oil film.Physical property,pore structure and movable fluid characteristics are all controlled by digenesis and their impacts on waterflooding efficiency are in accordance.Generally,the pore throat radius size and distribution and movable fluid percentage are closely related to waterflooding law.展开更多
Rockfall poses a great threat to buildings and personal security. To understand the dynamic characteristics of rockfalls is a prerequisite for disaster prevention and assessment. Models for rockfalls in different form...Rockfall poses a great threat to buildings and personal security. To understand the dynamic characteristics of rockfalls is a prerequisite for disaster prevention and assessment. Models for rockfalls in different forms are established based on the theory of rigid body motion. The equivalent velocity considering the rotational effect is determined by the energy ratio. Besides, considering plastic deformation and nonlinear hardening, the maximum impact force is estimated based on the Hertz contact theory. Then, a case study is carried out to illustrate the applicability of the model and sensitive analyses on some affecting parameters are also made. Calculation results show that the maximum impact force increases with the increasing of incident velocity, angle and slope gradient reflected by the changing of energy ratio. Moreover, the model for the estimation of maximum impact force is validated by two different scales of experiments and compared with other theoretical models. Simulated maximum impact forces agree well with the experiments.展开更多
Analysis of the climatic characteristics of the tropical cyclones that affect China yields several interesting features. The frequency of these tropical cyclones tended to decrease from 1951 to 2005, with the lowest f...Analysis of the climatic characteristics of the tropical cyclones that affect China yields several interesting features. The frequency of these tropical cyclones tended to decrease from 1951 to 2005, with the lowest frequency in the past ten years. The decrease in the frequency of super typhoons is particularly significant. The main season of tropical cyclone activities is from May to November, with an active period from July to September. There are three obvious sources of these tropical cyclones and they vary with seasons and decades. Their movement has also changed with seasons. On average, these tropical cyclones affect China for 5.6 months annually and the period of influence decreases in the past decades. An analysis of daily data indicates that the days of typhoon influence are shorter in winter and spring and longer in summer. The frequency of tropical cyclones is the largest over southeastern China, decreasing northwestward. Taiwan is the region that is affected by tropical cyclones most frequently. The average annual precipitation associated with tropical cyclones has also decreased gradually northwestward from southeastern China.展开更多
The middle class in metropolitan Chinese cities has become an important social group. With the rapid development of urbanization and constant advancement of suburbanization, the middle class has increasingly come to i...The middle class in metropolitan Chinese cities has become an important social group. With the rapid development of urbanization and constant advancement of suburbanization, the middle class has increasingly come to influence city traffic. Research into middle-class commuting activities thus has practical significance for improving traffic congestion and reducing the commuting burden in metropolitan cities. Based on a dataset formed by 816 completed surveys, this paper analyzes the commuting mode, time and distance of middle-class residents in Guangzhou City using the descriptive statistical method. The results indicate that private cars are the main commuting mode, followed by public transport. Meanwhile, middle-class residents mainly undertake medium-short time and medium-short distance commuting. The study subsequently uses multilevel logistic regression and multiple linear regression models to analyze the factors that influence commuting mode choice, time and distance. The gender, age, number of family cars, housing source and jobs-housing balance are the most important factors influencing commuting mode choice; housing, population density, jobs-housing balance and commuting mode significantly affect commuting time; and transport accessibility, jobs-housing balance and commuting mode are the notable factors affecting commuting distance. Finally, this paper analyzes what is affecting the commuting activities of middle-class residents and determines the differences in commuting activity characteristics and influence factors between middle-class and ordinary residents. Policy suggestions to improve urban planning and urban management are also proposed.展开更多
Based on the UCG(underground coal gasification) theory, the “three zones” which are oxidization zone, reduction zone, and drying zone, were divided; physical and chemical properties of each zone were analyzed. Facto...Based on the UCG(underground coal gasification) theory, the “three zones” which are oxidization zone, reduction zone, and drying zone, were divided; physical and chemical properties of each zone were analyzed. Factors, such as temperature, rate of water pouring, quantity of air blast, thickness of coal seam, and the operation pressure were discussed. Among the influencing factors, the temperature is the most important one.展开更多
Wetlands are sensitive to climate change, in the same time, wetlands can influence climate. This study analyzed the spa- rio-temporal characteristics of wetland change in the semi-arid zone of Northeast China from 198...Wetlands are sensitive to climate change, in the same time, wetlands can influence climate. This study analyzed the spa- rio-temporal characteristics of wetland change in the semi-arid zone of Northeast China from 1985 to 2010, and investigated the impact of large area of wetland change on local climate. Results showed that the total area of wetlands was on a rise in the study area. Although natural wetlands （marshes, riparians and lakes） decreased, constructed wetlands （rice fields） increased significantly, and the highest in- crease rate in many places exceeded 30%. Anthropogenic activities are major driving factors for wetland change. Wetland change pro- duced an impact on local climate, mainly on maximum temperature and precipitation during the period of May-September. The increase （or decrease） of wetland area could reduce （or increase） the increment of maximum temperature and the decrement of precipitation. The changes in both maximum temperature and precipitation corresponded with wetland change in spatial distribution. Wetland change played a more important role in moderating local climate compared to the contribution of woodland and grassland changes in the study area. Cold-humid effect of wetlands was main way to moderating local climate as well as alleviating climatic wanning and drying in the study area, and heterogeneity of underlying surface broadened the cold-humid effect of wetlands.展开更多
This paper expounded in detail the principle of energy spectrum analysis based on discrete wavelet transformation and multiresolution analysis. In the aspect of feature extraction method study, with investigating the ...This paper expounded in detail the principle of energy spectrum analysis based on discrete wavelet transformation and multiresolution analysis. In the aspect of feature extraction method study, with investigating the feature of impact factor in vibration signals and considering the non-placidity and non-linear of vibration diagnosis signals, the authors import wavelet analysis and fractal theory as the tools of faulty signal feature description. Experimental results proved the validity of this method. To some extent, this method provides a good approach of resolving the wholesome problem of fault feature symptom description.展开更多
Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the pa...Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and lO m wide （0.5 ha） line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.展开更多
In this study, a number of typical precursory anomalies recorded by stations in Qinghai, Gansu, Sichuan, Xinjiang, Ningxia, Hebei and Shaanxi provinces and autonomous regions before the Ms8.1 earthquake in the west of...In this study, a number of typical precursory anomalies recorded by stations in Qinghai, Gansu, Sichuan, Xinjiang, Ningxia, Hebei and Shaanxi provinces and autonomous regions before the Ms8.1 earthquake in the west of Kunlun Mountains Pass are collected and checked. According to the standards of earthquake cases in China, the criteria of the precursory anomalies are determined, and 53 distinguished. The characteristics of these anomalies before the Ms S. 1 earthquake are analyzed, with results showing a very large earthquake affected area. The precursory anomalies recorded by instruments were 2900 km away from the epicenter, and according to the study in this paper, reached 2100 km away. The results also show that the anomalies present characteristics of long duration, multi-measurement items and large-amplitude variation. The authors believe that in large earthquake monitoring, attention should be paid to the variation of data over a large area, ranging up to thousands kilometers, with much denser earthquake observation networks.展开更多
COVID-19 has tremendously impacted the travel habits of urban residents.This study used the“node-line segment-network”hierarchy and about:blank migration big data to conduct a comparative analysis of the travel network pa...COVID-19 has tremendously impacted the travel habits of urban residents.This study used the“node-line segment-network”hierarchy and about:blank migration big data to conduct a comparative analysis of the travel network patterns of urban people on China’s National Day holiday before and during the COVID-19 outbreak(i.e.,2019 and 2021).The results revealed four interesting patterns:(1)In 2021,there was an increase in the aggregation coefficient and access to the intra-provincial linkage network,indicating a higher degree of the travel agglomeration of residents under the pandemic.(2)In 2021,the“hub-and-spoke”pattern on the national scale,the“core-edge”pattern of the intra-provincial scale and the“rhomboidal”structure of the extra-provincial scale were more contracted,aggregated,and low-value.(3)The coverage of the urban advantageous association decreased while the total numbers of urban clusters and single provincial clusters increased,reaching 25 and 16,respectively.This indicates that the pandemic intensified the effect of administrative boundaries as a barrier.(4)The primary determinants of movement during the pandemic were urban competition,policy control,administrative boundary barriers,and the travel intentions of residents.展开更多
As an effective way to transform the model of rural economic development and upgrade the industrialstructure in the new era,the integration of agriculture and tourism can provide powerful support for expandingfarmers&...As an effective way to transform the model of rural economic development and upgrade the industrialstructure in the new era,the integration of agriculture and tourism can provide powerful support for expandingfarmers'income sources and narrowing the gap between urban and rural areas.It is also an important path forpromoting the rural economy and common prosperity of people.Based on 2008−2019 panel data covering 30provinces and regions in China,the dynamic spatial Durbin model and threshold effect model are used to empirically analyse the effects and characteristics of the integrated development of agriculture and tourism on commonprosperity.The results show the following:(1)The level of common prosperity and the integration of agriculture andtourism increased steadily during the study period and showed obvious spatial agglomeration characteristics.(2)The level of common prosperity was affected by the previous state,showing strong path dependence and dynamicpersistence.(3)The integrated development of agriculture and tourism had a significant direct effect and spillovereffect on the level of common prosperity.The integrated development of agriculture and tourism in neighbouringareas also promoted an improvement in the common prosperity of the local region.The direct effect was thestrongest in the central region,and the spillover effect was the largest in the eastern region.(4)The influence of theintegration of agriculture and tourism on the level of common prosperity presented certain threshold characteristics,and there was a typical stage and economic environment dependence.Overall,with the improvement in the integration of agriculture and tourism and the economic development level,the impact of the integration of agricultureand tourism on common prosperity was enhanced,but this disequilibrium effect also had typical regional heterogeneity.The conclusions can provide useful implications for promoting the high-quality development of the integration of agriculture and tourism to better promote common prosperity.展开更多
Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot poi...Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.展开更多
基金Supported by Special Fund for Agro-scientific Research in the Public Interest(201103039)Shandong Provincial Natural Science Foundation,China(ZR2013DQ023)+1 种基金Science and Technology Development Plan Project of Shandong Province(2013GNC11204)Major Agricultural Application Technology Innovation Project of Shandong Province(Study on Environmental Regulation and Fertilizer Application Techniques for High Yield and High Efficiency Utilization of Greenhouse Tomato)~~
文摘To make clear the emission characteristics of soil N20 from typical green- house vegetable fields in North China, an experiment was conducted in greenhouse tomato field in Shouguang city, Shandong province, China＇s ＂Home of Vegetables＂. The N2O fluxes were observed in four experimental treatments, as follows： none N fertilizer （CK）, single organic fertilizer （OM）, conventional fertilization （FP） and opti- mized and reduced nitrogen fertilization （OPT）, by a close chamber-gas chromato- graph method. The effects of different fertilization treatments on N2O emission and tomato yield were analyzed. The results showed that following the fertilization and ir- rigation, the pulsed emissions of N2O were measured. The N2O emission peak ap- peared after basal fertilizer application and irrigation and could be maintained for about 20 days. While the N2O emission peak caused by topdressing was smaller and last only 3-5 days. The statistical analysis showed that the N2O fluxes were affected by air temperature, soil temperature and WFPS at soil depth of 3 cm. The total contents of soil N2O fluxes had significant differences among experimental groups. The total content orderly was FP of 14. 77 kg/hm^2, OPT of 9. 73 kg/hm^2, OM of 6.84 kg/hm^2 and CK of 2.37 kg/hm^2. The N~：~ emission coefficient ranged from 0.83%-1.10%,which was close to or more than the recommended value （1.0%） by IPCC. Compared with the FP treatment, the tomato yield in OPT treatment, whose application rate of chemical N fertilizer decreased by about 60%, increased by 2.2%. Under the current management measures, the reasonable reduction on ap- plicaUon rate of organic manure and chemical nitrogen fertilizer could effectively re- duce the N=O emissions in greenhouse vegetable fields.
基金Supported by the Ger man National Science Foundation (DFG)(No. GR412/33)
文摘This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section （2 × 2 mm^2, 165 mm long） machined directly on an aluminum plate（180×120×3 nm^2）, which was covered by a transparent plate. The working fluid employed was ethanol. As the results, the influence parameters of thermal performance were investigated, such as filling ratio, heat load and operational orientations etc. Filling ratio was found to be a critical parameter, and its effect was rather complicated. According to its values the PHP plate could have four distinct working zones with different operational characteristics and heat transfer performance. The effect of heat load on thermal performance was found to be positive, and in general, iucrcasing the heat load would improve heat transfer performance. In order to analyze the effect of gravity on thermal performance, three different heat modes and total seven tilt angles were tested and compared. Successful operation at all orientations with respect to gravity was also achieved.
基金Under the auspices of National Natural Science Foundation of China (No 40871069)Megaproject of Science and Technology Research for the 11th Five-Year Plan of China (No 2006BAJ05A06)Natural Science Foundation of Beijing City (No 9072002)
文摘Based on the analysis of its basic characteristics, this article investigated the disparities of Chinese service industry among the three regions （the eastern China, the western China and the middle China） and inter-provincial disparities of that in the three regions by Theil coefficient and cluster analysis. Then, major factors influencing its spatial disparity were explored by correlation analysis and regression analysis. The conclusions could be drawn as follows. 1） The development of Chinese service industry experienced three phases since the 1980s： rapid growth period, slow growth period, and recovery period. From the proportion of value-added and employment, its development was obviously on the low level. From the composition of industrial structure, traditional service sectors were dominant, but modem service sectors were lagged. Moreover, its spatial disparity was distinct. 2） The level of Chinese service industry was divided into five basic regional ranks： well-developed, developed, relatively-developed, underdeveloped and undeveloped regions, As a whole, the overall structure of spatial disparity was steady in 1990-2005. But there was notable gradient disparity in the interior structure of service industry among different provinces. Furthermore, the overall disparity expanded rapidly in 1990-2005. The inter-provincial disparity of service industry in the three regions, especially in the eastern China, was bigger than the disparity among the three regions. And 3） the level of economic development, the level of urban development, the scale of market capacity, the level of transportation and telecommunication, and the abundance of human resources were major factors influencing the development of Chinese service industry.
基金Supported by the National Natural Science Foundation of China(41001030)the Natural Science Basic Research Plan in Shaanxi Province of China(2014JQ5194,2014JM7206)+1 种基金the Education Department of Shaanxi Province Special Research Project(12JK048415JK1386)
文摘[Objective] The morphological characters of C.lasiocarpa were studied to find its morphological responses to different water regimes and growth stretagies through different water experiences.[Method] A seeding transplanting experiment with controlled water levels was set up,and the water level was changed at the middle of the season to compare water influence at the seeding stage and later growing period.C.lasiocarpa height,leaf length,leaf number,rhizome and adventitious roots length were measured at certain time througth the growing season.[Result] Results at the thriving season indicated that C.lasiocarpa height and leaf length in the experiment were similar to that in the field,but leaf number was higher under-5 cm water level and dry-wet alternate conditions than that in the field.At later growth period,height and leaf length under constant flooding(15cm) was significantly higher than that under other culture conditions,and also that of the field investigation;while the leaf number had a trend as-5 cm water level treatment>constant flooding>dry-wet alternate>field investigation.The height and leaf length were sensitive to seeding stage water effects,and leaf number sensitive to later influences.[Conclusion] Changes of water regimes in the growing season disturbed the growth of C.lasiocarpa,could accelerate or suspend its wilt,and modified the length of life history.
基金Under the auspices of Ministry of Education, China (No. 108148)State Key Laboratory of Urban and Regional Ecology (No. SKLURE2010-2-2)+1 种基金National Basic Research Program of China (No. 2010CB951203)Key Research Program of Shanghai Science & Technology (No. 08231200700, 08231200702)
文摘To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness (MA), species diversity (H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance (D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels (R = 0.55, p < 0.05), soil moisture (R = 0.53, p < 0.05), soil salinity (R = 0.43, p < 0.05) and reclamation time (R = 0.40, p < 0.05).
基金sponsored by the National High-Tech Research and Development Program of China(No.2007AA06Z220)the Key Science and Technology Program of Ministry of Education(No. 307014)the Research Program of Huainan Mining Group.
文摘Based on data from through-hole and logging,we studied the failure characteristics of surface drainage wells for relieved coal gas in Huainan mining area and its influencing factors.The results show that the damaged positions of drainage wells are mainly located at the thick clay layer in the low alluvium and the lithological interface in the upper section of bedrock in west mining area.The failure depth of casing is 244-670 m and concentrates at about 270-460 m deep.These damaged positions are mainly located in the bending zone according to three zones of rock layers in the vertical section above the roof divided. Generally,the casing begins to deform or damage before the face line about 30-150 m.Special formation structure and rock mass properties are the direct causes of the casing failure,high mining height and fast advancing speed are fundamental reasons for rock mass damage.However,the borehole configuration and spacing to the casing failure are not very clear.
文摘Through the research on stress metamorphism character of the II1 coal seam in Ludian gliding structure, the stress effecting factors of metamorphism and hydrocarbon generation process of tectonic coal were studied. It is shown that different tectonic stress has different coal evolution effects. Compared with tensional stress, compressive stress, which has apparent anisotropic characteristics, has greater stimulative effect against the increase of coal metamorphic degree, the abscission of functional group and side chains of basic structural unit, and the formation of gas primarily composed of methane.
基金Project(2015KTCL01-09)supported by the Innovation Project of Science and Technology of Shaanxi Province,ChinaProject(2015M582699)supported by the China Postdoctoral Science Foundation+1 种基金Project(2016JQ4022)supported by the Natural Science Foundation Research Project of Shaanxi Province,ChinaProject(41702146)supported by the National Natural Science Foundation of China
文摘Actual sandstone micromodel was used in this work to conduct the microscopic waterflooding experiment of ultra-low sandstone reservoir,since the inside seepage characteristics of microscopic waterflooding process of Chang 8 ultra-low permeability sandstone reservoir of Upper Triassic Yanchang formation in Huaqing region of the Ordos Basin,China is difficult to observe directly.Combined with physical property,casting thin sections,constant-rate mercury injection capillary pressure and nuclear magnetic resonance,the influence of reservoir property on the waterflooding characteristics in pores were analyzed and evaluated.Seepage paths of waterflooding characteristics were divided into four types:homogeneous seepage,reticular-homogeneous seepage,finger-reticular seepage and finger-like seepage,the waterflooding efficiency of which decreases in turn.More than 70%of residual oil occurs as flowing-around seepage and oil film.Physical property,pore structure and movable fluid characteristics are all controlled by digenesis and their impacts on waterflooding efficiency are in accordance.Generally,the pore throat radius size and distribution and movable fluid percentage are closely related to waterflooding law.
基金supported by the National Natural Science Foundation of China (41472272)the Youth Science and Technology Fund of Sichuan Province (2016JQ0011)
文摘Rockfall poses a great threat to buildings and personal security. To understand the dynamic characteristics of rockfalls is a prerequisite for disaster prevention and assessment. Models for rockfalls in different forms are established based on the theory of rigid body motion. The equivalent velocity considering the rotational effect is determined by the energy ratio. Besides, considering plastic deformation and nonlinear hardening, the maximum impact force is estimated based on the Hertz contact theory. Then, a case study is carried out to illustrate the applicability of the model and sensitive analyses on some affecting parameters are also made. Calculation results show that the maximum impact force increases with the increasing of incident velocity, angle and slope gradient reflected by the changing of energy ratio. Moreover, the model for the estimation of maximum impact force is validated by two different scales of experiments and compared with other theoretical models. Simulated maximum impact forces agree well with the experiments.
基金National Natural Science Foundation of China (41005051)Applicability of various multi-model ensemble approaches in seasonal precipitation prediction
文摘Analysis of the climatic characteristics of the tropical cyclones that affect China yields several interesting features. The frequency of these tropical cyclones tended to decrease from 1951 to 2005, with the lowest frequency in the past ten years. The decrease in the frequency of super typhoons is particularly significant. The main season of tropical cyclone activities is from May to November, with an active period from July to September. There are three obvious sources of these tropical cyclones and they vary with seasons and decades. Their movement has also changed with seasons. On average, these tropical cyclones affect China for 5.6 months annually and the period of influence decreases in the past decades. An analysis of daily data indicates that the days of typhoon influence are shorter in winter and spring and longer in summer. The frequency of tropical cyclones is the largest over southeastern China, decreasing northwestward. Taiwan is the region that is affected by tropical cyclones most frequently. The average annual precipitation associated with tropical cyclones has also decreased gradually northwestward from southeastern China.
基金Under the auspices of National Natural Science Foundation of China(No.41271182)
文摘The middle class in metropolitan Chinese cities has become an important social group. With the rapid development of urbanization and constant advancement of suburbanization, the middle class has increasingly come to influence city traffic. Research into middle-class commuting activities thus has practical significance for improving traffic congestion and reducing the commuting burden in metropolitan cities. Based on a dataset formed by 816 completed surveys, this paper analyzes the commuting mode, time and distance of middle-class residents in Guangzhou City using the descriptive statistical method. The results indicate that private cars are the main commuting mode, followed by public transport. Meanwhile, middle-class residents mainly undertake medium-short time and medium-short distance commuting. The study subsequently uses multilevel logistic regression and multiple linear regression models to analyze the factors that influence commuting mode choice, time and distance. The gender, age, number of family cars, housing source and jobs-housing balance are the most important factors influencing commuting mode choice; housing, population density, jobs-housing balance and commuting mode significantly affect commuting time; and transport accessibility, jobs-housing balance and commuting mode are the notable factors affecting commuting distance. Finally, this paper analyzes what is affecting the commuting activities of middle-class residents and determines the differences in commuting activity characteristics and influence factors between middle-class and ordinary residents. Policy suggestions to improve urban planning and urban management are also proposed.
文摘Based on the UCG(underground coal gasification) theory, the “three zones” which are oxidization zone, reduction zone, and drying zone, were divided; physical and chemical properties of each zone were analyzed. Factors, such as temperature, rate of water pouring, quantity of air blast, thickness of coal seam, and the operation pressure were discussed. Among the influencing factors, the temperature is the most important one.
基金Under the auspices of National Environmental Protection Public Welfare Industry Research Fund(No.2011467032)
文摘Wetlands are sensitive to climate change, in the same time, wetlands can influence climate. This study analyzed the spa- rio-temporal characteristics of wetland change in the semi-arid zone of Northeast China from 1985 to 2010, and investigated the impact of large area of wetland change on local climate. Results showed that the total area of wetlands was on a rise in the study area. Although natural wetlands （marshes, riparians and lakes） decreased, constructed wetlands （rice fields） increased significantly, and the highest in- crease rate in many places exceeded 30%. Anthropogenic activities are major driving factors for wetland change. Wetland change pro- duced an impact on local climate, mainly on maximum temperature and precipitation during the period of May-September. The increase （or decrease） of wetland area could reduce （or increase） the increment of maximum temperature and the decrement of precipitation. The changes in both maximum temperature and precipitation corresponded with wetland change in spatial distribution. Wetland change played a more important role in moderating local climate compared to the contribution of woodland and grassland changes in the study area. Cold-humid effect of wetlands was main way to moderating local climate as well as alleviating climatic wanning and drying in the study area, and heterogeneity of underlying surface broadened the cold-humid effect of wetlands.
文摘This paper expounded in detail the principle of energy spectrum analysis based on discrete wavelet transformation and multiresolution analysis. In the aspect of feature extraction method study, with investigating the feature of impact factor in vibration signals and considering the non-placidity and non-linear of vibration diagnosis signals, the authors import wavelet analysis and fractal theory as the tools of faulty signal feature description. Experimental results proved the validity of this method. To some extent, this method provides a good approach of resolving the wholesome problem of fault feature symptom description.
基金funded by the Department of Biotechnology (DBT), Govt. of India (Grant No. BT/ PR7928/NDB/52/ 9/2006] through BDT Network Project
文摘Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and lO m wide （0.5 ha） line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.
基金funded by National Joint Foundation of Earthquake of China under Grant No.106086
文摘In this study, a number of typical precursory anomalies recorded by stations in Qinghai, Gansu, Sichuan, Xinjiang, Ningxia, Hebei and Shaanxi provinces and autonomous regions before the Ms8.1 earthquake in the west of Kunlun Mountains Pass are collected and checked. According to the standards of earthquake cases in China, the criteria of the precursory anomalies are determined, and 53 distinguished. The characteristics of these anomalies before the Ms S. 1 earthquake are analyzed, with results showing a very large earthquake affected area. The precursory anomalies recorded by instruments were 2900 km away from the epicenter, and according to the study in this paper, reached 2100 km away. The results also show that the anomalies present characteristics of long duration, multi-measurement items and large-amplitude variation. The authors believe that in large earthquake monitoring, attention should be paid to the variation of data over a large area, ranging up to thousands kilometers, with much denser earthquake observation networks.
基金The National Natural Science Foundation of China(42271252,42230510,42371253)The Theme Academic Activities of National Social Science Foundation Academic Societies(22STA021)。
文摘COVID-19 has tremendously impacted the travel habits of urban residents.This study used the“node-line segment-network”hierarchy and about:blank migration big data to conduct a comparative analysis of the travel network patterns of urban people on China’s National Day holiday before and during the COVID-19 outbreak(i.e.,2019 and 2021).The results revealed four interesting patterns:(1)In 2021,there was an increase in the aggregation coefficient and access to the intra-provincial linkage network,indicating a higher degree of the travel agglomeration of residents under the pandemic.(2)In 2021,the“hub-and-spoke”pattern on the national scale,the“core-edge”pattern of the intra-provincial scale and the“rhomboidal”structure of the extra-provincial scale were more contracted,aggregated,and low-value.(3)The coverage of the urban advantageous association decreased while the total numbers of urban clusters and single provincial clusters increased,reaching 25 and 16,respectively.This indicates that the pandemic intensified the effect of administrative boundaries as a barrier.(4)The primary determinants of movement during the pandemic were urban competition,policy control,administrative boundary barriers,and the travel intentions of residents.
基金The Key Research Project of the Hunan Provincial Department of Education(22A611)The Hunan Province Applied Characteristic Discipline“Applied Economics”Funding Project(XiangJiaotong[2018]No.469)+1 种基金The Loudi Philosophy and Social Sciences Evaluation Committee Project(202302B)The Graduate Teaching Reform Project of the Hunan Provincial Department of Education(2022JGYB216)。
文摘As an effective way to transform the model of rural economic development and upgrade the industrialstructure in the new era,the integration of agriculture and tourism can provide powerful support for expandingfarmers'income sources and narrowing the gap between urban and rural areas.It is also an important path forpromoting the rural economy and common prosperity of people.Based on 2008−2019 panel data covering 30provinces and regions in China,the dynamic spatial Durbin model and threshold effect model are used to empirically analyse the effects and characteristics of the integrated development of agriculture and tourism on commonprosperity.The results show the following:(1)The level of common prosperity and the integration of agriculture andtourism increased steadily during the study period and showed obvious spatial agglomeration characteristics.(2)The level of common prosperity was affected by the previous state,showing strong path dependence and dynamicpersistence.(3)The integrated development of agriculture and tourism had a significant direct effect and spillovereffect on the level of common prosperity.The integrated development of agriculture and tourism in neighbouringareas also promoted an improvement in the common prosperity of the local region.The direct effect was thestrongest in the central region,and the spillover effect was the largest in the eastern region.(4)The influence of theintegration of agriculture and tourism on the level of common prosperity presented certain threshold characteristics,and there was a typical stage and economic environment dependence.Overall,with the improvement in the integration of agriculture and tourism and the economic development level,the impact of the integration of agricultureand tourism on common prosperity was enhanced,but this disequilibrium effect also had typical regional heterogeneity.The conclusions can provide useful implications for promoting the high-quality development of the integration of agriculture and tourism to better promote common prosperity.
基金supported by Public Science and Technology Research Funds Project of Ocean(Grant No.201105001)Fundamental Project of Science and Technology(Grant No.2013FY112900)National Natural Science Foundation of China(Grant Nos.40506017,41206046)
文摘Based on multiple types of data, the topographical features of the Okinawa Trough(OT) have been characterized and a computation method has been proposed to determine the break point of continental shelf(BOS), foot point of the continental slope(FOS), the central axial point, and the maximum depth point. A total of 48 topographical profiles that crosscut the continental slope have been used to determine the trends of the BOS and FOS(the BOS and FOS lines) in the East China Sea(ECS). The trend of central axial points in the OT has been similarly determined by analyzing 39 topographical profiles across the axis of the trough. The BOS line forms the boundary between the continental shelf and slope. In the ECS, the BOS line roughly follows the 200 m isobath, continuously in the northern and middle parts of the OT, but jumping about somewhat in the south. The FOS line is the boundary between the continental slope and the bottom of the trough. The depth of the FOS increases gradually from north to south in the OT. Intense incisions by canyons into the slope in the southern part of the trough have led to the complex distribution of FOS. Topographical profiles crosscutting the northern, middle, and southern parts of the OT exhibit features that include: a single W-shape, a composite W-shape, and a U-shape, respectively, which suggests that in the middle and northern parts of the trough the central axial points are always located on seamount peaks or ridges associated with linear seamounts, whereas in the south they are found in the center of en echelon depressions. The line formed by the central axial points is the east-west dividing line of the OT, which indicates that the trough is a natural gap that prevents the extension of ECS continental shelf to the east. The distributions of the BOS and FOS lines are influenced by fluctuation of sea levels and submarine canyons, whereas the distribution of axis lines is controlled by tectonics and deposition.
