科研成果

In China, three major rangeland management policies have caused dramatic social, economic, and ecological changes for pastoral regions in the past 30 yr: the Rangeland Household Contract Policy (RHCP), Rangeland Ecological Construction Projects (RECPs), and the Nomad Settlement Policy (NSP). The impacts of these policies are greatly debated. In this paper, we conduct a systematic review of academic perspectives on the impacts of the three policies and the causes of ineffective and negative effects. The findings demonstrate that academics increasingly report negative impacts of RHCP on the ecosystem, animal husbandry, pastoralist livelihoods, and pastoral society. An increasing number of scholars, although not the majority, attribute the negative impacts to improper policy itself rather than incomplete implementation. Regarding the RECPs, most academics believe that policies have improved the rangeland ecosystem but with obvious negative impacts on pastoralist livelihoods and pastoral society; they attribute the problems to incomplete policy implementation. For the NSP, most academics report positive impacts on pastoralist livelihoods and animal husbandry, although recent researchers have identified negative impacts on pastoral society and the ecosystem. Although they are not in the mainstream, more and more academics attribute the negative impacts to improper policy. Finally, we apply the concept of coupled social-ecological systems (SES) to further analyze the outcomes of these three policies and propose a more flexible and inclusive land tenure policy that recognizes the diverse local institutional arrangements; an integrated RECP framework that considers coadaptation between social and ecological systems; and facilitating voluntary choice in nomad settlement and developing innovative approaches to provide social services for pastoralists who would like to remain in pastoral areas. As these three policy approaches are applied in rangeland management and pastoral development worldwide, this paper may provide useful implications for future policy development in pastoral regions on a global scale. (C) 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.;ABSTRACT In China, three major rangeland management policies have caused dramatic social, economic, and ecological changes for pastoral regions in the past 30 yr: the Rangeland Household Contract Policy (RHCP), Rangeland Ecological Construction Projects (RECPs), and the Nomad Settlement Policy (NSP). The impacts of these policies are greatly debated. In this paper, we conduct a systematic review of academic perspectives on the impacts of the three policies and the causes of ineffective and negative effects. The findings demonstrate that academics increasingly report negative impacts of RHCP on the ecosystem, animal husbandry, pastoralist livelihoods, and pastoral society. An increasing number of scholars, although not the majority, attribute the negative impacts to improper policy itself rather than incomplete implementation. Regarding the RECPs, most academics believe that policies have improved the rangeland ecosystem but with obvious negative impacts on pastoralist livelihoods and pastoral society; the.;  In China, three major rangeland management policies have caused dramatic social, economic, and ecological changes for pastoral regions in the past 30yr: the Rangeland Household Contract Policy (RHCP), Rangeland Ecological Construction Projects (RECPs), and the Nomad Settlement Policy (NSP). The impacts of these policies are greatly debated. In this paper, we conduct a systematic review of academic perspectives on the impacts of the three policies and the causes of ineffective and negative effects. The findings demonstrate that academics increasingly report negative impacts of RHCP on the ecosystem, animal husbandry, pastoralist livelihoods, and pastoral society. An increasing number of scholars, although not the majority, attribute the negative impacts to improper policy itself rather than incomplete implementation. Regarding the RECPs, most academics believe that policies have improved the rangeland ecosystem but with obvious negative impacts on pastoralist livelihoods and pastoral society; they attribute the problems to incomplete policy implementation. For the NSP, most academics report positive impacts on pastoralist livelihoods and animal husbandry, although recent researchers have identified negative impacts on pastoral society and the ecosystem. Although they are not in the mainstream, more and more academics attribute the negative impacts to improper policy. Finally, we apply the concept of coupled social-ecological systems (SES) to further analyze the outcomes of these three policies and propose a more flexible and inclusive land tenure policy that recognizes the diverse local institutional arrangements; an integrated RECP framework that considers coadaptation between social and ecological systems; and facilitating voluntary choice in nomad settlement and developing innovative approaches to provide social services for pastoralists who would like to remain in pastoral areas. As these three policy approaches are applied in rangeland management and pastoral development worldwide, this paper may provide useful implications for future policy development in pastoral regions on a global scale.;In China, three major rangeland management policies have caused dramatic social, economic, and ecological changes for pastoral regions in the past 30yr: the Rangeland Household Contract Policy (RHCP), Rangeland Ecological Construction Projects (RECPs), and the Nomad Settlement Policy (NSP). The impacts of these policies are greatly debated. In this paper, we conduct a systematic review of academic perspectives on the impacts of the three policies and the causes of ineffective and negative effects. The findings demonstrate that academics increasingly report negative impacts of RHCP on the ecosystem, animal husbandry, pastoralist livelihoods, and pastoral society. An increasing number of scholars, although not the majority, attribute the negative impacts to improper policy itself rather than incomplete implementation. Regarding the RECPs, most academics believe that policies have improved the rangeland ecosystem but with obvious negative impacts on pastoralist livelihoods and pastoral society; they attribute the problems to incomplete policy implementation. For the NSP, most academics report positive impacts on pastoralist livelihoods and animal husbandry, although recent researchers have identified negative impacts on pastoral society and the ecosystem. Although they are not in the mainstream, more and more academics attribute the negative impacts to improper policy. Finally, we apply the concept of coupled social-ecological systems (SES) to further analyze the outcomes of these three policies and propose a more flexible and inclusive land tenure policy that recognizes the diverse local institutional arrangements; an integrated RECP framework that considers coadaptation between social and ecological systems; and facilitating voluntary choice in nomad settlement and developing innovative approaches to provide social services for pastoralists who would like to remain in pastoral areas. As these three policy approaches are applied in rangeland management and pastoral development worldwide, this paper may provide useful implications for future policy development in pastoral regions on a global scale.;  In China, three major rangeland management policies have caused dramatic social, economic, and ecological changes for pastoral regions in the past 30yr: the Rangeland Household Contract Policy (RHCP), Rangeland Ecological Construction Projects (RECPs), and the Nomad Settlement Policy (NSP). The impacts of these policies are greatly debated. In this paper, we conduct a systematic review of academic perspectives on the impacts of the three policies and the causes of ineffective and negative effects. The findings demonstrate that academics increasingly report negative impacts of RHCP on the ecosystem, animal husbandry, pastoralist livelihoods, and pastoral society. An increasing number of scholars, although not the majority, attribute the negative impacts to improper policy itself rather than incomplete implementation. Regarding the RECPs, most academics believe that policies have improved the rangeland ecosystem but with obvious negative impacts on pastoralist livelihoods and pastoral society; they attribute the problems to incomplete policy implementation. For the NSP, most academics report positive impacts on pastoralist livelihoods and animal husbandry, although recent researchers have identified negative impacts on pastoral society and the ecosystem. Although they are not in the mainstream, more and more academics attribute the negative impacts to improper policy. Finally, we apply the concept of coupled social-ecological systems (SES) to further analyze the outcomes of these three policies and propose a more flexible and inclusive land tenure policy that recognizes the diverse local institutional arrangements; an integrated RECP framework that considers coadaptation between social and ecological systems; and facilitating voluntary choice in nomad settlement and developing innovative approaches to provide social services for pastoralists who would like to remain in pastoral areas. As these three policy approaches are applied in rangeland management and pastoral development worldwide, this paper may provide useful implications for future policy development in pastoral regions on a global scale.;

Recently, environmental pressures along coasts have increased substantially. Classification of estuaries according to their susceptibility to eutrophication nutrient load is a useful method to determine priority management objects and to enforce control measures. Using historical monitoring data from 2007 to 2012, from 65 estuaries, including 101 estuarine monitoring sections and 260 coastal monitoring stations, a nutrient-driven phytoplankton dynamic model was developed based on the relationship among phytoplankton biomass, Total Nitrogen (TN) load and physical features of estuaries. The ecological filter effect of estuaries was quantified by introducing conversion efficiency parameter values into the model. Markov Chain Monte Carlo algorithm of Bayesian inference was then employed to estimate parameters in the model. The developed model fitted well to the observed chlorophyll, primary production, grazing, and sinking rates. The analysis suggests that an estuary with Q/V (the ratio of river flow to estuarine volume) greater than 2.0 per year and E > (conversion efficiency ratio) less than 1.0 g C/g N can be classified as less susceptible to TN load, Q/V between 0.7 to 2.0 per year and E > between 1.0 to 3.0 g C/g N as moderately susceptible, and E > greater than 3.0 g C/g N as very susceptible. The estuaries with Q/V less than 0.7 per year vary greatly in their susceptibility. The estuaries with high and moderate susceptibility accounted for 67% of all the analyzed estuaries. They have relatively high eutrophication risks and should be the focus of environmental supervision and pollution prevention.

The disordered packings of tetrahedra often show no obvious macroscopic orientational or positional order for a wide range of packing densities, and it has been found that the local order in particle clusters is the main order form of tetrahedron packings. Therefore, a cluster analysis is carried out to investigate the local structures and properties of tetrahedron packings in this work. We obtain a cluster distribution of differently sized clusters, and peaks are observed at two special clusters, i.e., dimer and wagon wheel. We then calculate the amounts of dimers and wagon wheels, which are observed to have linear or approximate linear correlations with packing density. Following our previous work, the amount of particles participating in dimers is used as an order metric to evaluate the order degree of the hierarchical packing structure of tetrahedra, and an order map is consequently depicted. Furthermore, a constraint analysis is performed to determine the isostatic or hyperstatic region in the order map. We employ a Monte Carlo algorithm to test jamming and then suggest a new maximally random jammed packing of hard tetrahedra from the order map with a packing density of 0.6337.

Exposure to fine and ultrafine particles as well as particulate polycyclic aromatic hydrocarbons (PAHs) by commuters in three transportation modes (walking, subway and bus) were examined in December 2011 in Beijing, China. During the study period, real-time measured median PM2.5 mass concentration (PMC) for walking, riding buses and taking the subway were 26.7, 32.9 and 56.9 mu g m(-3), respectively, and particle number concentrations (PNC) were 1.1 x 10(4), 1.0 x 10(4) and 2.2 x 10(4) cm(-3). Commuters were exposed to higher PNC in air-conditioned buses and aboveground-railway, but higher PMC in underground-subway compared to aboveground-railway. PNC in roadway modes (bus and walking) peaked at noon, but was lower during traffic rush hours, negatively correlated with PMC. Toxic potential of particulate-PAHs estimated based on benzo(a)pyrene toxic equivalents (BaP TEQs) showed that walking pedestrians were subjected to higher BaP TEQs than bus (2.7-fold) and subway (3.6-fold) commuters, though the highest PMC and PNC were observed in subway. (C) 2015 Elsevier Ltd. All rights reserved.

Serious air pollution in China now has great influence and threat on air quality, visibility, and human health. Accurate identification and quantification of sources play an important role in establishing relative policies, laws and control measures. This study briefly introduces development history and characteristics of three main methods to apportion sources of particles(emission inventory, sourceoriented model and receptor model). Based on data platform of PM2.5 and chemical components conducted in Atlanta, USA, this study summarizes characteristics of major source apportionment methods of source-oriented model and receptor model and their performance towards different sources(i.e. vehicle emission, coal combustion, biomass burning, dust and secondary sources), points out the differences of various methods and potential reasons and analyzes their weakness and strength in application, suggesting that developing ensemble method should be an important direction for future source apportionment research.

Recently a Monte Carlo method based on signed particles for time-dependent simulations of the Wigner equation has been proposed. While it has been thoroughly validated against physical benchmarks, no technical study about its numerical accuracy has been performed. To this end, this paper presents the first step towards the construction of firm mathematical foundations for the signed particle Wigner Monte Carlo method. An initial investigation is performed by means of comparisons with a cell average spectral element method, which is a highly accurate deterministic method and utilized to provide reference solutions. Several different numerical tests involving the time-dependent evolution of a quantum wave-packet are performed and discussed in deep details. In particular, this allows us to depict a set of crucial criteria for the signed particle Wigner Monte Carlo method to achieve a satisfactory accuracy.  

The occurrence of polycyclic aromatic hydrocarbons (PAHs) and nitrated derivatives (NPAHs), as well as their transformation may have significant health impacts on humans. To investigate the level, spatial distribution and the transformation process of PAHs and NPAHs in North China, we performed a gridded field passive air sampling campaign in summer of 2011. The median concentration of 25 PAH congeners and 13 NPAHs was 294 ng m−3 (or 26.7 μg sample−1) and 203 ng sample−1, respectively. Relative higher level of PAHs in Shanxi Province and NPAHs in megacities was observed. In North China, coal/biomass combustion and photochemical formation was the predominant source of PAHs and NPAHs, respectively. To investigate the relationship between these pollutants, a model incorporating NPAHs, PAHs and NO2 was established, and the result indicated that NO2 will promote the transformation processes from PAHs to NPAHs, which may increase the total toxicity of PAH–NPAH mixtures.