The Caohai Nature Reserve is one of the three major plateau freshwater lakes in China.Since the 1950s,human activities such as land reclamation and population relocation have greatly damaged Caohai.A rapid evaluation ...The Caohai Nature Reserve is one of the three major plateau freshwater lakes in China.Since the 1950s,human activities such as land reclamation and population relocation have greatly damaged Caohai.A rapid evaluation of the spatiotemporal evolution trend of the ecological quality of the Caohai Nature Reserve is significant for the maintenance and construction of the ecosystem in this area.The research is based on the Google Earth Engine(GEE)remote sensing cloud computing platform.Landsat TM/OLI images from May to October in five time periods:2000-2002,2004-2006,2009-2011,2014-2016,and 2019-2021 were obtained to reconstruct the optimal cloud image set by averaging the images in each time period.By constructing four ecological indicators:Greenness(NDVI),Wetness(Wet),Hotness(LST),and Dryness(NDBSI),and using Principal Component Analysis(PCA)method to obtain the Remote Sensing Ecological Index(RSEI)for the corresponding years,the spatiotemporal variation of ecological quality in the Caohai Nature Reserve over 20 years was analyzed.The results indicate:①the mean value of RSEI increased from 0.460 in 2000-2002 to 0.772 in 2019-2021,a 67.83%increase,indicating a significant improvement in the ecological quality of the reserve over the 20 years;②from the perspective of functional zoning of the Caohai Nature Reserve,the ecological quality of the core area showed a degrading trend,while the ecological quality of the buffer zone and experimental zone significantly improved;③with the implementation of ecological restoration projects,the ecological quality of the reserve gradually recovered and improved from 2014 to 2021.The trend of RSEI value changes is well correlated with human interventions,indicating that the PCA-based RSEI model can be effectively used for ecological quality assessment in lake areas.展开更多
After an international contest announced by the City of Abu Dhabi “Cool Abu Dhabi Challenge”<sup>1</sup> and the article published as a digest of a paper titled A Nature-based Solution [1], the decision ...After an international contest announced by the City of Abu Dhabi “Cool Abu Dhabi Challenge”<sup>1</sup> and the article published as a digest of a paper titled A Nature-based Solution [1], the decision has been made to take part in improving thermal comfort in public spaces by mitigating the impact of the effect of Urban Heat Islands (UHI)<sup>2</sup> in the city of the Belgrade. The basic research aims at achieving the balance between the conflicting impacts when the buildings with their infrastructure and water-green surrounding area are in such correlation that it fulfils acceptable living and heating standards and reduces the use of fossil fuels for cooling the urban areas (buildings). By implementing the remote detection it is possible to analyze and quantify the impact of over-building on the temperature rise in urban areas as well as the disturbance of the heating comfort and the increased demand for additional cooling. Now it is possible to create virtual models that will incorporate this newly-added urban vegetation into urban plans, depending on the evaporation potential that will affect the microclimate of the urban area. Such natural cooling can be measured and adapted and hence aimed at a potential decrease in areas with UHI emissions [2]. Suitable greenery in the summer season can be a useful improvement which concurrently enables and complements several cooling mechanisms—evaporative cooling and evapotranspiration, i.e. natural cooling systems. The remote detection shall establish and map the “healthy” and “unhealthy” greenery zones—that is the vegetation zones with the highest evaporative potential with the “cooling by evaporation” effect and also, by implementing the urban prediction model, it shall propose green infrastructure corridors aimed at a potential decrease in the Urban Heat Island Emission.展开更多
This paper establishes a risk assessment index system for the natural gas industrial chain. China's natural gas industrial chain is entering a stage of rapid growth. In order to guarantee healthy development of the n...This paper establishes a risk assessment index system for the natural gas industrial chain. China's natural gas industrial chain is entering a stage of rapid growth. In order to guarantee healthy development of the natural gas industrial chain, it is urgent to establish a risk alert system, which is based on a risk assessment index system. First of all, the risks of the natural gas industrial chain are defined in the paper; then the risk factors are analyzed according to the present status of the natural gas industrial chain, and five categories of risk factors are summarized: resource risk, transport risk, marketing risk, risk of unbalanced chain links, and environment risk. The paper presents the principles of the risk assessment index system. The natural gas industrial chain risk assessment index system is established with four levels and forty-six risk indices.展开更多
Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ...Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ope were obtained. By using comprehensive index method, the normalized environmental factors were weighted and superimposed, and the fi nal evaluation results of ecological environment in Guangzhou City were obtained. The results showed that overall situation of natural ecological environment in Guangzhou was not optimistic, that is, the area of land with bad, moderate, good and superior environment accounted for 59.70%, 35.79%, 4.50% and around 0.01% of total area of land in Guangzhou City respectively. Ecological environment was generally poor in the central urban districts in the south of Guangzhou City, while it was relatively better in the north and northeast. Attaching importance to the constr uction of greenbelts and greenways is an effective way to improve regional environmental quality and natural ecological e nvironment level.展开更多
The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger elect...The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis.展开更多
The spatial and temporal changes of landscape pattern and their driving forces in each functional zone of Nanling National Nature Reserve were analyzed based on the GIS and RS platform. The results showed that from 19...The spatial and temporal changes of landscape pattern and their driving forces in each functional zone of Nanling National Nature Reserve were analyzed based on the GIS and RS platform. The results showed that from 1988 to 2009, in respect of changes of Jandscape area, the main forest landscape accounted about 95% of the total area, of which evergreen broad-leaved forest had the largest area, accounting for more than 50% of the total area. The dominant landscape was coniferous forest. In respect of landscape fragmentation, the density index of land- scape in the whole area increased, and the degree of landscape fragmentation also increased. In the core area, the patch density decreased slightly, and the average patch area of each type of landscape increased; the degree of landscape fragmen- tation increased slightly. In the buffer area and the experimental area, the degree of landscape fragmentation increased. In terms of landscape diversity, the landscape pattern in the whole area became complex, and the diversity index of landscape in- creased and the degree of heterogeneity increased. In the core area, the diversity index of landscape increased slightly. In the buffer area, it increased significantly. In the experiment area, the diversity index reduced, and the degree of landscape het- erogeneity reduced. In the whole study area, the landscape tended to be diversified. The landscape pattern of the experimental area was consistent with that of the whole study area, and there was no obvious change in the buffer zone, while the landscape pattern in the core area developed towards the single direction.展开更多
Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central is...Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central issue.The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes.Taking Ni and NiFe catalysts supported over g-Al_(2)O_(3) oxide as reference materials,this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO_(2) methanation.The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface.Displaying lower Turn Over Frequencies than Ni/Al catalyst,the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances.For NiFe catalysts,analogous Ni_(5)Fe_(1) alloys were constituted over both alumina and biochar supports.The highest specific activity of the catalyst series,exhibited by the NiFe/C catalyst,was related to the development of surface basic sites along with weaker NiFe-C interactions,which resulted in increased Ni0:NiO surface populations under reaction conditions.In summary,the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.展开更多
This work illustrates the steady state, two dimensional natural convective flow and heat transfer features in square enclosure containing heated hexagonal block maintained either at constant wall temperature(CWT) or u...This work illustrates the steady state, two dimensional natural convective flow and heat transfer features in square enclosure containing heated hexagonal block maintained either at constant wall temperature(CWT) or uniform heat flux(UHF) thermal conditions. Governing equations(mass, momentum and energy) are solved by using finite volume method(FVM) with 3rd order accurate QUICK discretization scheme and SIMPLE algorithm for range of field pertinent parameters such as, Grashof number(10~3≤ Gr ≤ 10~6), Prandtl number(1 ≤ Pr ≤ 100) and power law index(0.5 ≤ n ≤ 1.5). The analysis of momentum and heat transfer characteristics are delineated by evolution of streamlines, isotherms, variation of average Nusselt number value and Colburn factor for natural convection(j_(nH)). A remarkable change is observed on fluid flow and thermal distribution pattern in cavity for both thermal conditions. Nusselt number shows linear variation with Grashof and Prandtl numbers; while rate of heat transfer by convection decreases for power law index value. Higher heat transfer rate can be achieved by using uniform heat flux condition. A Nusselt number correlation is developed for possible utilization in engineering/scientific design purpose.展开更多
The application of knowledge is a primary source of growth in the knowledge economy. The World Bank Group has developed a rigorous assessment methodology for assessing a country's ability to access and use knowledge ...The application of knowledge is a primary source of growth in the knowledge economy. The World Bank Group has developed a rigorous assessment methodology for assessing a country's ability to access and use knowledge to become more competitive in the knowledge economy of the 21st century. The World Bank's annual knowledge economy index is grounded on a four-pillar model: (1) economic incentives and institutional regime; (2) education and skills; (3) information and communication infrastructure; and (4) innovation systems. An argument can be made that the model lacks coverage of some key factors that pertain to intellectual capital and the production and consumption of knowledge. The model's heavy focus on economic incentives and open institutional regimes comes at a societal cost. This paper proposes an alternative knowledge economy index which is grounded in a more holistic and balanced view of a knowledge society. Adopting the perspective of triple bottom line shifts the purpose and design of a knowledge economy from one of aggregation and reporting to action and involvement. The World Bank's scorecard and indexing methodology are adaptable to this new perspective and a new set of indicators.展开更多
Background: China has a long tradition of managing planted forests. Different species of Populus, Eucalyptus, Larix, Cunninghamia and Pinus are planted to satisfy the local demand for wood products and provide ecologi...Background: China has a long tradition of managing planted forests. Different species of Populus, Eucalyptus, Larix, Cunninghamia and Pinus are planted to satisfy the local demand for wood products and provide ecological services at the same time. Evidence of the greater resilience of natural forests provides the motivation to develop asymmetric planting patterns, which is the focus of this study. We present a new method for designing plantation patterns that follow those observed in natural ecosystems and to maintain some regularity for operational convenience. Methods: Based on the uniform angle index, we analyzed the spatial structure of six natural forests in different regions of China. The uniform angle index describes the degree of spatial uniformity of the n nearest neighbors of a given reference tree. Accordingly, we identified all possible patterns of a neighborhood group within a regular planting pattern and developed a method to optimize planting point arrangements that contain some randomness as well as a minimum degree of regularity. Results:(1) There are 13 types of structural units in a regular planting, including seven random units, five even units and one cluster unit;(2) Five near-natural arrangements are presented with a minimum proportion of 50% of random units. These five arrangements represent a combination of regularity for operational convenience and asymmetry. Conclusions: The new planting patterns developed in this study are expected to increase the asymmetric competition and resilience of these important ecosystems. Some experimental plantings, based on our findings, have already been established, e.g., in Pinus tabulaeformis plantations in Tianshui, Gansu Province, and in a Populus deltoides plantation in Fangshan near Beijing.展开更多
Background: Nowadays, though more attention is being paid to oral and dental hygiene all over the world, dental caries and periodontal diseases are increasing daily. We decided to study the effectiveness of natural to...Background: Nowadays, though more attention is being paid to oral and dental hygiene all over the world, dental caries and periodontal diseases are increasing daily. We decided to study the effectiveness of natural toothbrush in prevention of dental caries and plaque formation. Methods: This analytic, semi-experimental clinical trial included 390 individuals. Subjects were divided into 3 groups: using natural toothbrush, using artificial toothbrush and using both natural and artificial toothbrush. The plaque index and DMFT was assessed at the beginning of the study until 1 year. ANOVA, Kruskal Wallis, LSD, Paired t-test, chi square, Fisher exact and Mc-Nemar tests were used for data analysis. Results: The plaque index in all three groups showed a mean reduction of 0.71. The mean DMFT in the samples before intervention was 8.38 ± 4.14 and increased to 9.1 ± 4.56. At the end of the study, the lowest plaque index was observed in the group using both the natural and artificial methods. During one year follow-up, the plaque index decreased 1.16, 0.83, and 0.21 degrees in the first, second and third groups. Conclusion: The increase in DMFT in the group that used artificial toothbrush was more than other groups. Thus, use of natural toothbrush leads to a decrease in growth rate of DMFT. Therefore natural toothbrush can be used for the cleaning of teeth and prevention of dental caries.展开更多
Nanling National Nature Reserve is established on the basis of 5 provincial nature reserves, and the original functional zoning is maintained. This paper explored problems of the reserve in division range and function...Nanling National Nature Reserve is established on the basis of 5 provincial nature reserves, and the original functional zoning is maintained. This paper explored problems of the reserve in division range and functional zoning, and gavea pertinent adjustment scheme. The adjustment results are(1) cutting out the scattered areas in neighborhood, and fi lling in the internal split parts;(2) establishing corridors between the reserve and neighboring nature reserves;(3) redividing the functional zones.展开更多
3S technology was applied to analyze spatio-temporal changes of landscape pattern in Nanling National Nature Reserve and the driving forces. The results showed that the study area was dominated by forest landscape fro...3S technology was applied to analyze spatio-temporal changes of landscape pattern in Nanling National Nature Reserve and the driving forces. The results showed that the study area was dominated by forest landscape from 1988 to 2009, accounting for 95% of the total area, among all forest landscapes, evergreen broadleaved forest accounted for the largest ratio(>50%). In terms of landscape fragmentation, landscape density index of the study area increased, landscape fragmentation was aggravated; patch density of core zone declined slightly, mean patch area of all landscape types increased, landscape fragmentation decreased slightly; buffer zone and experimental zone witnessed the aggravation of fragmentation. In terms of landscape diversity, landscape pattern of the study area became increasingly complex, diversity index increased, landscape heterogenization was enhanced; landscape diversity of the core zone increased slightly, that of the buffer zone increased greatly, but that of the experimental zone declined and landscape heterogenization reduced. Landscapes in the whole area grew more diversified, while landscape pattern of the core zone was simplified, that of the buffer zone witnessed slight changes, and that of the experimental zone kept consistent with that of the study area. In terms of driving forces of landscape pattern change, natural factors have contributed to the landscape changes in the study area, but human factors such as forest management, forest tourism, local residents an economic factors played a dominant role. With the increasing external interventions to the landscape pattern change, the contradiction between landscape eco-environment protection and resource development and utilization in Nanling National Nature Reserve will be increasingly sharpened.展开更多
Maghnite clay obtained from Tlemcen, Algeria was investigated to remove heavy metal ion from wastewater. Thus, the present study includes the adsorption of Ni(II) in aqueous solution on maghnite clay through the proce...Maghnite clay obtained from Tlemcen, Algeria was investigated to remove heavy metal ion from wastewater. Thus, the present study includes the adsorption of Ni(II) in aqueous solution on maghnite clay through the process of adsorption under various conditions (with variable concentration of metal ion, temperature, pH and mixing time). Increasing pH favours the removal of metal ions till they are precipitated as the insoluble hydroxides. The uptake is rapid with maximum adsorption being observed within 10 min for Ni(II). In addition, the results obtained from adsorption isotherm indicated that these data can be better fitted with the Langmuir and Freundlich equations than the Dubinin-Radushke- vich (D-R) equation.展开更多
基金Supported by Joint Project between Bijie Science and Technology Bureau and Guizhou University of Engineering Science (Bike Lianhe Zi (Guigongcheng)[2021]03)Guizhou Provincial Key Technology R&D Program (Qiankehe[2023]General 211).
文摘The Caohai Nature Reserve is one of the three major plateau freshwater lakes in China.Since the 1950s,human activities such as land reclamation and population relocation have greatly damaged Caohai.A rapid evaluation of the spatiotemporal evolution trend of the ecological quality of the Caohai Nature Reserve is significant for the maintenance and construction of the ecosystem in this area.The research is based on the Google Earth Engine(GEE)remote sensing cloud computing platform.Landsat TM/OLI images from May to October in five time periods:2000-2002,2004-2006,2009-2011,2014-2016,and 2019-2021 were obtained to reconstruct the optimal cloud image set by averaging the images in each time period.By constructing four ecological indicators:Greenness(NDVI),Wetness(Wet),Hotness(LST),and Dryness(NDBSI),and using Principal Component Analysis(PCA)method to obtain the Remote Sensing Ecological Index(RSEI)for the corresponding years,the spatiotemporal variation of ecological quality in the Caohai Nature Reserve over 20 years was analyzed.The results indicate:①the mean value of RSEI increased from 0.460 in 2000-2002 to 0.772 in 2019-2021,a 67.83%increase,indicating a significant improvement in the ecological quality of the reserve over the 20 years;②from the perspective of functional zoning of the Caohai Nature Reserve,the ecological quality of the core area showed a degrading trend,while the ecological quality of the buffer zone and experimental zone significantly improved;③with the implementation of ecological restoration projects,the ecological quality of the reserve gradually recovered and improved from 2014 to 2021.The trend of RSEI value changes is well correlated with human interventions,indicating that the PCA-based RSEI model can be effectively used for ecological quality assessment in lake areas.
文摘After an international contest announced by the City of Abu Dhabi “Cool Abu Dhabi Challenge”<sup>1</sup> and the article published as a digest of a paper titled A Nature-based Solution [1], the decision has been made to take part in improving thermal comfort in public spaces by mitigating the impact of the effect of Urban Heat Islands (UHI)<sup>2</sup> in the city of the Belgrade. The basic research aims at achieving the balance between the conflicting impacts when the buildings with their infrastructure and water-green surrounding area are in such correlation that it fulfils acceptable living and heating standards and reduces the use of fossil fuels for cooling the urban areas (buildings). By implementing the remote detection it is possible to analyze and quantify the impact of over-building on the temperature rise in urban areas as well as the disturbance of the heating comfort and the increased demand for additional cooling. Now it is possible to create virtual models that will incorporate this newly-added urban vegetation into urban plans, depending on the evaporation potential that will affect the microclimate of the urban area. Such natural cooling can be measured and adapted and hence aimed at a potential decrease in areas with UHI emissions [2]. Suitable greenery in the summer season can be a useful improvement which concurrently enables and complements several cooling mechanisms—evaporative cooling and evapotranspiration, i.e. natural cooling systems. The remote detection shall establish and map the “healthy” and “unhealthy” greenery zones—that is the vegetation zones with the highest evaporative potential with the “cooling by evaporation” effect and also, by implementing the urban prediction model, it shall propose green infrastructure corridors aimed at a potential decrease in the Urban Heat Island Emission.
基金This research is supported by CNPC Innovation Foundation.
文摘This paper establishes a risk assessment index system for the natural gas industrial chain. China's natural gas industrial chain is entering a stage of rapid growth. In order to guarantee healthy development of the natural gas industrial chain, it is urgent to establish a risk alert system, which is based on a risk assessment index system. First of all, the risks of the natural gas industrial chain are defined in the paper; then the risk factors are analyzed according to the present status of the natural gas industrial chain, and five categories of risk factors are summarized: resource risk, transport risk, marketing risk, risk of unbalanced chain links, and environment risk. The paper presents the principles of the risk assessment index system. The natural gas industrial chain risk assessment index system is established with four levels and forty-six risk indices.
基金Sponsored by National Natural Science Foundation of China(41271060)
文摘Based on the ETM remote sensing images of Guangzhou City in 2014, the spatial distribution results o f three environmental factors including vegetation coverage(NDVI), soil index(vegetation index of bare soil) and sl ope were obtained. By using comprehensive index method, the normalized environmental factors were weighted and superimposed, and the fi nal evaluation results of ecological environment in Guangzhou City were obtained. The results showed that overall situation of natural ecological environment in Guangzhou was not optimistic, that is, the area of land with bad, moderate, good and superior environment accounted for 59.70%, 35.79%, 4.50% and around 0.01% of total area of land in Guangzhou City respectively. Ecological environment was generally poor in the central urban districts in the south of Guangzhou City, while it was relatively better in the north and northeast. Attaching importance to the constr uction of greenbelts and greenways is an effective way to improve regional environmental quality and natural ecological e nvironment level.
文摘The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis.
文摘The spatial and temporal changes of landscape pattern and their driving forces in each functional zone of Nanling National Nature Reserve were analyzed based on the GIS and RS platform. The results showed that from 1988 to 2009, in respect of changes of Jandscape area, the main forest landscape accounted about 95% of the total area, of which evergreen broad-leaved forest had the largest area, accounting for more than 50% of the total area. The dominant landscape was coniferous forest. In respect of landscape fragmentation, the density index of land- scape in the whole area increased, and the degree of landscape fragmentation also increased. In the core area, the patch density decreased slightly, and the average patch area of each type of landscape increased; the degree of landscape fragmen- tation increased slightly. In the buffer area and the experimental area, the degree of landscape fragmentation increased. In terms of landscape diversity, the landscape pattern in the whole area became complex, and the diversity index of landscape in- creased and the degree of heterogeneity increased. In the core area, the diversity index of landscape increased slightly. In the buffer area, it increased significantly. In the experiment area, the diversity index reduced, and the degree of landscape het- erogeneity reduced. In the whole study area, the landscape tended to be diversified. The landscape pattern of the experimental area was consistent with that of the whole study area, and there was no obvious change in the buffer zone, while the landscape pattern in the core area developed towards the single direction.
文摘Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central issue.The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes.Taking Ni and NiFe catalysts supported over g-Al_(2)O_(3) oxide as reference materials,this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO_(2) methanation.The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface.Displaying lower Turn Over Frequencies than Ni/Al catalyst,the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances.For NiFe catalysts,analogous Ni_(5)Fe_(1) alloys were constituted over both alumina and biochar supports.The highest specific activity of the catalyst series,exhibited by the NiFe/C catalyst,was related to the development of surface basic sites along with weaker NiFe-C interactions,which resulted in increased Ni0:NiO surface populations under reaction conditions.In summary,the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.
文摘This work illustrates the steady state, two dimensional natural convective flow and heat transfer features in square enclosure containing heated hexagonal block maintained either at constant wall temperature(CWT) or uniform heat flux(UHF) thermal conditions. Governing equations(mass, momentum and energy) are solved by using finite volume method(FVM) with 3rd order accurate QUICK discretization scheme and SIMPLE algorithm for range of field pertinent parameters such as, Grashof number(10~3≤ Gr ≤ 10~6), Prandtl number(1 ≤ Pr ≤ 100) and power law index(0.5 ≤ n ≤ 1.5). The analysis of momentum and heat transfer characteristics are delineated by evolution of streamlines, isotherms, variation of average Nusselt number value and Colburn factor for natural convection(j_(nH)). A remarkable change is observed on fluid flow and thermal distribution pattern in cavity for both thermal conditions. Nusselt number shows linear variation with Grashof and Prandtl numbers; while rate of heat transfer by convection decreases for power law index value. Higher heat transfer rate can be achieved by using uniform heat flux condition. A Nusselt number correlation is developed for possible utilization in engineering/scientific design purpose.
文摘The application of knowledge is a primary source of growth in the knowledge economy. The World Bank Group has developed a rigorous assessment methodology for assessing a country's ability to access and use knowledge to become more competitive in the knowledge economy of the 21st century. The World Bank's annual knowledge economy index is grounded on a four-pillar model: (1) economic incentives and institutional regime; (2) education and skills; (3) information and communication infrastructure; and (4) innovation systems. An argument can be made that the model lacks coverage of some key factors that pertain to intellectual capital and the production and consumption of knowledge. The model's heavy focus on economic incentives and open institutional regimes comes at a societal cost. This paper proposes an alternative knowledge economy index which is grounded in a more holistic and balanced view of a knowledge society. Adopting the perspective of triple bottom line shifts the purpose and design of a knowledge economy from one of aggregation and reporting to action and involvement. The World Bank's scorecard and indexing methodology are adaptable to this new perspective and a new set of indicators.
基金supported by the National Key Research and Development Program of China(2016YFD0600203)
文摘Background: China has a long tradition of managing planted forests. Different species of Populus, Eucalyptus, Larix, Cunninghamia and Pinus are planted to satisfy the local demand for wood products and provide ecological services at the same time. Evidence of the greater resilience of natural forests provides the motivation to develop asymmetric planting patterns, which is the focus of this study. We present a new method for designing plantation patterns that follow those observed in natural ecosystems and to maintain some regularity for operational convenience. Methods: Based on the uniform angle index, we analyzed the spatial structure of six natural forests in different regions of China. The uniform angle index describes the degree of spatial uniformity of the n nearest neighbors of a given reference tree. Accordingly, we identified all possible patterns of a neighborhood group within a regular planting pattern and developed a method to optimize planting point arrangements that contain some randomness as well as a minimum degree of regularity. Results:(1) There are 13 types of structural units in a regular planting, including seven random units, five even units and one cluster unit;(2) Five near-natural arrangements are presented with a minimum proportion of 50% of random units. These five arrangements represent a combination of regularity for operational convenience and asymmetry. Conclusions: The new planting patterns developed in this study are expected to increase the asymmetric competition and resilience of these important ecosystems. Some experimental plantings, based on our findings, have already been established, e.g., in Pinus tabulaeformis plantations in Tianshui, Gansu Province, and in a Populus deltoides plantation in Fangshan near Beijing.
文摘Background: Nowadays, though more attention is being paid to oral and dental hygiene all over the world, dental caries and periodontal diseases are increasing daily. We decided to study the effectiveness of natural toothbrush in prevention of dental caries and plaque formation. Methods: This analytic, semi-experimental clinical trial included 390 individuals. Subjects were divided into 3 groups: using natural toothbrush, using artificial toothbrush and using both natural and artificial toothbrush. The plaque index and DMFT was assessed at the beginning of the study until 1 year. ANOVA, Kruskal Wallis, LSD, Paired t-test, chi square, Fisher exact and Mc-Nemar tests were used for data analysis. Results: The plaque index in all three groups showed a mean reduction of 0.71. The mean DMFT in the samples before intervention was 8.38 ± 4.14 and increased to 9.1 ± 4.56. At the end of the study, the lowest plaque index was observed in the group using both the natural and artificial methods. During one year follow-up, the plaque index decreased 1.16, 0.83, and 0.21 degrees in the first, second and third groups. Conclusion: The increase in DMFT in the group that used artificial toothbrush was more than other groups. Thus, use of natural toothbrush leads to a decrease in growth rate of DMFT. Therefore natural toothbrush can be used for the cleaning of teeth and prevention of dental caries.
基金Sponsored by Digital Monitoring and Maintenance Platform Program of Nanling National Nature Reserve(GDHS13SGHG05025)
文摘Nanling National Nature Reserve is established on the basis of 5 provincial nature reserves, and the original functional zoning is maintained. This paper explored problems of the reserve in division range and functional zoning, and gavea pertinent adjustment scheme. The adjustment results are(1) cutting out the scattered areas in neighborhood, and fi lling in the internal split parts;(2) establishing corridors between the reserve and neighboring nature reserves;(3) redividing the functional zones.
基金Sponsored by Digital Monitoring,Management and Protection Program of Nanling National Nature Reserve(GDHS13SGHG05025)
文摘3S technology was applied to analyze spatio-temporal changes of landscape pattern in Nanling National Nature Reserve and the driving forces. The results showed that the study area was dominated by forest landscape from 1988 to 2009, accounting for 95% of the total area, among all forest landscapes, evergreen broadleaved forest accounted for the largest ratio(>50%). In terms of landscape fragmentation, landscape density index of the study area increased, landscape fragmentation was aggravated; patch density of core zone declined slightly, mean patch area of all landscape types increased, landscape fragmentation decreased slightly; buffer zone and experimental zone witnessed the aggravation of fragmentation. In terms of landscape diversity, landscape pattern of the study area became increasingly complex, diversity index increased, landscape heterogenization was enhanced; landscape diversity of the core zone increased slightly, that of the buffer zone increased greatly, but that of the experimental zone declined and landscape heterogenization reduced. Landscapes in the whole area grew more diversified, while landscape pattern of the core zone was simplified, that of the buffer zone witnessed slight changes, and that of the experimental zone kept consistent with that of the study area. In terms of driving forces of landscape pattern change, natural factors have contributed to the landscape changes in the study area, but human factors such as forest management, forest tourism, local residents an economic factors played a dominant role. With the increasing external interventions to the landscape pattern change, the contradiction between landscape eco-environment protection and resource development and utilization in Nanling National Nature Reserve will be increasingly sharpened.
文摘Maghnite clay obtained from Tlemcen, Algeria was investigated to remove heavy metal ion from wastewater. Thus, the present study includes the adsorption of Ni(II) in aqueous solution on maghnite clay through the process of adsorption under various conditions (with variable concentration of metal ion, temperature, pH and mixing time). Increasing pH favours the removal of metal ions till they are precipitated as the insoluble hydroxides. The uptake is rapid with maximum adsorption being observed within 10 min for Ni(II). In addition, the results obtained from adsorption isotherm indicated that these data can be better fitted with the Langmuir and Freundlich equations than the Dubinin-Radushke- vich (D-R) equation.