This study examines the development and trends of China’s alfalfa market and imports, identifies key factors for the rapid increase in China’s alfalfa imports, and discusses potential impacts of the U.S.-China trade...This study examines the development and trends of China’s alfalfa market and imports, identifies key factors for the rapid increase in China’s alfalfa imports, and discusses potential impacts of the U.S.-China trade dispute and retaliations on the alfalfa markets and trade in both nations. China’s rapid transition toward larger-scale commercial dairy production, with enhanced feed and cost management as well as quality and safety control, and its limited resources for high-quality alfalfa production are key factors for the dramatic increase in its alfalfa imports, from 19 601 metric tons in 2008 to 1.38 million metric tons(mmt) in 2018. While the United States dominated China’s alfalfa imports with an average share of 97.01% from 2007 to 2017, the share dropped to 83.76% in 2018 and 63.28% in January 2019 due to the trade dispute and retaliations started in 2018. China will likely remain a large importer of alfalfa because of both its growing demand and the comparative advantages of imported alfalfa in quality and price, but the imports from the United States will be highly affected by the ongoing trade dispute and negotiations. China is also expected to make more efforts to reduce its dependence on U.S. alfalfa through increased investment in domestic alfalfa production and identification of alternative sources of alfalfa and other hay imports.展开更多
语言作为人类精神的产物和文明的载体应具有审美价值,而演讲作为一种特殊的语言表现形式,它的审美价值在于能够使受众在愉悦中自觉地去接受或容纳演讲的主旨。Speech on Hitler’s Invasion of the U.S.S.R.是丘吉尔政治生涯中重要的演...语言作为人类精神的产物和文明的载体应具有审美价值,而演讲作为一种特殊的语言表现形式,它的审美价值在于能够使受众在愉悦中自觉地去接受或容纳演讲的主旨。Speech on Hitler’s Invasion of the U.S.S.R.是丘吉尔政治生涯中重要的演讲作品之一,既具有时效性和实效性,又具有历久弥新的语言审美价值。展开更多
The United States passed the Better Utilization of Investment Leading to Development(BUILD Act),as a counterweight to China’s overseas development activities.Under the Act,the US established a new federal agency,the ...The United States passed the Better Utilization of Investment Leading to Development(BUILD Act),as a counterweight to China’s overseas development activities.Under the Act,the US established a new federal agency,the U.S.International Development Finance Corporation(DFC),to enhance U.S.development financing capabilities.To better understand the impact of the DFC on China’s development finance,this article analyzes the DFC’s purpose,functions,structure,and funding.Then it focuses on the purpose of establishing the DFC,providing a preliminary analysis of the potential motivation for its establishment.It also compares the China Development Bank(CDB)and the DFC based on their focused sectors.Finally,through an in-depth analysis of financial frictions in China-U.S.relations,this article argues that the DFC competes with China’s overseas development financing activities in the context of broader strategic competition between China and the U.S.展开更多
The global community has prepared for the withdrawal of the U.S. from the Paris Agreement since Donald Trump was elected as the president of the U.S. However, Trump's formal declaration of withdrawal still caused ...The global community has prepared for the withdrawal of the U.S. from the Paris Agreement since Donald Trump was elected as the president of the U.S. However, Trump's formal declaration of withdrawal still caused worldwide reaction. Trump will use the withdrawal to build his political reputation and to renegotiate the Paris Agreement despite its negative effects on the political credibility, international relationships, and potential long-term economic growth of the U.S. In general, the withdrawal of the U.S. from the Paris Agreement will not change the development of low-carbon technologies and the transformation trend of the global climate governance regime. However, the long-term goals and international cooperation on climate change will be affected by budget cuts in American climate change research and the cancelation of donations from the multilateral environmental fund of the U.S. If the Paris Agreement is renegotiated, the common but differentiated principle of responsibility of the United Nations Framework Convention on Climate Change will be challenged again. Nevertheless, climate change governance remains a main theme of future sustainable development. Instead of national governments, local governments and non-governmental organizations will develop strategies for technical innovation and emphasize pragmatic cooperation, thus expanding their roles in climate change governance. The capacity building on climate change research and public awareness should be enhanced as a long-term objective of global climate change governance.展开更多
Based on the Computable General Equilibrium (CGE) model and scenario analysis, the impacts of the U.S. withdrawal from the Paris Agreement on the carbon emission space and mitigation cost in China, European Union (EU)...Based on the Computable General Equilibrium (CGE) model and scenario analysis, the impacts of the U.S. withdrawal from the Paris Agreement on the carbon emission space and mitigation cost in China, European Union (EU), and Japan are assessed under Nationally Determined Contributions (NDCs) and 2 C scenarios due to the changed emission pathway of the U.S. The results show that, under the condition of constant global cumulative carbon emissions and a fixed burden-sharing scheme among countries, the failure of the U.S. to honor its NDC commitment to different degrees will increase the U.S. carbon emission space and decrease its mitigation cost. However, the carbon emission space of other parties, including China, EU, and Japan, will be reduced and their mitigation costs will be increased. In 2030, under the 2 C target, the carbon price will increase by 4.4e14.6 US$ t1 in China, by 9.7e35.4 US$ t1 in the EU, and by 16.0e53.5 US$ t1 in Japan. In addition, China, EU, and Japan will incur additional Gross Domestic Production (GDP) loss. Under the 2 C target, the GDP loss of China would increase by US$22.0e71.1 billion (equivalent to 16.4e53.1 US$ per capita), the EU's GDP loss would increase by US$9.4e32.1 billion (equivalent to 20.7e71.1 US$ per capita), and Japan's GDP loss will increase by US$4.1e13.5 billion (equivalent to 34.3e111.6 US$ per capita).展开更多
The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the ...The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.展开更多
Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visit...Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visitation and accessibility.First,the global and local accessibility indexes of each park unit are computed based on an accessibility model that takes into account the surrounding population and its proximity to the park unit.Integrated in the model is a distance decay coefficient that is derived from U.S.national park visitor surveys and therefore pertinent to the case of study.Then correlation analysis is performed between park visitation and accessibility based on park types,regions,and visitation types.Results show that total visitation is positively related to accessibility in National Memorials,Military Parks and Battlefield Parks/Sites but negatively related to accessibility in national parks and national monuments.However,recreational overnight stay visits are commonly negatively correlated to accessibility for almost all park types.Moreover,local accessibility index displays enhanced correlation coefficients with improved significance levels in many categories of analysis.Results suggest that historical/cultural national parks which often show positive correlations tend to attract more local visitors,but nature-based parks which mainly show negative correlations tend to attract more distant visitors.展开更多
Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of...Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of waste were landfilled in 2017.In total,these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG(Landfill Gas)generation accurately,or collect most of the LFG generated.This study was based on the hypothesis that,on the average,methane generation is proportional to the tonnage of wastes landfilled annually.The Landfill Methane Outreach Program of the EPA(EPA-LMOP)compiles annual operating data of all methane-capturing landfills.Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured,i.e.,an average capture of 0.024-ton CH4/ton waste.On the basis of the anaerobic reaction of the DOC(Degradable Organic Carbon)in landfilled wastes,the average rate of methane generation from all operating U.S.landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity;this number corresponds to bioreaction of about one half of the total organic carbon in MSW.On this basis,the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture,48%.Adding up all 1,164 operating landfills,their total emission of methane was estimated at 11.9 million metric tons of CH4.At CH4/CO2 equivalence of 25,this number corresponds to CO2-eq emissions of 270 million metric tons,i.e.,5.1%of the U.S.energy related carbon dioxide emissions.展开更多
Canola (Brassica napus L.) has potential to become alternative cash crop (healthy oil for human and meals for animal uses) with tremendous rotational benefits in the Southwestern U.S., a region dominated by cereal-fal...Canola (Brassica napus L.) has potential to become alternative cash crop (healthy oil for human and meals for animal uses) with tremendous rotational benefits in the Southwestern U.S., a region dominated by cereal-fallow cropping systems. However, information on optimum planting date for its successful production is limited. Field experiments were conducted in 2011-12 and 2012-13 seasons under irrigation condition to study the response of canola growth and yield to planting dates at Clovis, NM. Three planting dates (mid-September, late-September and early-October) and four canola varieties (early flowering: DKW41-10 and DKW46-15;medium flowering: Riley and Wichita) are studied. Fall plant stand density is significantly higher for early-October than mid- and late-September plantings. However, a ratio of fall to spring plant stand density indicates a greater reduction in spring plant stand density with early-October (25%) and mid-September (19%) than late-September (7%). Vegetative (by 13 days) and flowering (by 7 days) duration phases are significantly shortened with delay in planting. The decline in aboveground dry matter (DM) due to delayed planting resulted in significant seed yield reduction in both 2011-12 (26%) and in 2012-13 (8%) when early-October and mid-September plantings were compared. There was a positive relationship between final DM and canola seed yield, accounting for 84 and 34% variation for 2011-12 and 2012-13 seasons, respectively with the 2011-12 environmental conditions being conducive for genetically controlled variation in DM production to be more apparent and strong in explaining the variation in seed yield among varieties. Medium-flowering varieties produced higher DM (9741 vs. 8371 Kg•ha<sup>-1</sup>) and seed yield (2785 vs. 2035 Kg•ha<sup>-1</sup>) than early-flowering varieties. In addition to seed yield, DM can be used as an indirect selection criterion for seed yield in variety selection and appropriate planting dates including a guarantee for high crop residues (~75% of the total aboveground biomass) production to make canola a potential alternative cash and rotational break crop in the Southwestern U.S.展开更多
A growing demand for passenger and freight transportation, combined with limited capital to expand the United States （U.S.） rail infrastructure, is creating pressure for a more efficient use of the current line capa...A growing demand for passenger and freight transportation, combined with limited capital to expand the United States （U.S.） rail infrastructure, is creating pressure for a more efficient use of the current line capacity. This is further exacerbated by the fact that most passenger rail services operate on corridors that are shared with freight traffic. A capacity analysis is one alternative to address the situation and there are various approaches, tools, and methodologies available for application. As the U.S. continues to develop higher speed passenger services with similar characteristics to those in European shared-use lines, understanding the common methods and tools used on both continents grows in relevance. There has not as yet been a detailed investigation as to how each continent approaches capacity analysis, and whether any benefits could be gained from cross-pollination. This paper utilizes more than 50 past capacity studies from the U.S. and Europe to describe the different railroad capacity defini- tions and approaches, and then categorizes them, based on each approach. The capacity methods are commonly di- vided into analytical and simulation methods, but this paper also introduces a third, ＂combined simulation- analytical＂ category. The paper concludes that Europeanrail studies are more unified in terms of capacity, concepts, and techniques, while the U.S. studies represent a greater variation in methods, tools, and objectives. The majority of studies on both continents use either simulation or a combined simulation-analytical approach. However, due to the significant differences between operating philosophy and network characteristics of these two rail systems, European studies tend to use timetable-based simulation tools as opposed to the non-timetable-based tools commonly used in the U.S. rail networks. It was also found that validation of studies against actual operations was not typically completed or was limited to comparisons with a base model.展开更多
基于美国U. S. NEWS最新发布的"最佳图书情报学研究生院排名"(Best Library and Information StudiesPrograms)和代表院校的专业课程安排,通过调查和比较研究的方法,综合分析美国图书情报与档案管理类专业课程建设特点,为我...基于美国U. S. NEWS最新发布的"最佳图书情报学研究生院排名"(Best Library and Information StudiesPrograms)和代表院校的专业课程安排,通过调查和比较研究的方法,综合分析美国图书情报与档案管理类专业课程建设特点,为我国图书情报与档案管理类学科的课程建设提供参考与借鉴.展开更多
Distance higher education is an important component of the Chinese higher education.How to enhance the quality of distance higher education is one of the key issues to be addressed in the research areas of distance ed...Distance higher education is an important component of the Chinese higher education.How to enhance the quality of distance higher education is one of the key issues to be addressed in the research areas of distance education and higher education.As a crucial step to quality improvement,the constitution of accreditation system in distance higher education balances the benefits of all parties involved.This paper explores the American accreditation system of higher education and distance education and concludes with suggestions for the constitution of the Chinese quality assurance system:1)establishing third-party institutions to share part of the government roles;2)constituting the accreditation system;3)setting up appropriate standards;4)publicizing results of quality assurance work;and 5)building internal quality assurance mechanism.This paper is aimed to provide some reference to the constitution of accreditation system of distance higher education in China,facilitate the solution of quality problems in distance education,and promote the continuous improvement and development of distance education in China.展开更多
Objective To study the characteristics, specific functions and policy improvement process of the Group Purchasing Organizations (GPOs) in the U.S. and to provide references for drug group purchasing practices in China...Objective To study the characteristics, specific functions and policy improvement process of the Group Purchasing Organizations (GPOs) in the U.S. and to provide references for drug group purchasing practices in China. Methods Domestic and foreign relevant literatures, websites were reviewed or searched to analyze the functions and policy improvement process of the GPOs in the U.S. so as to provide references for drug group purchasing practices in China. Results and Conclusion As a third party in the U.S. GPOs has formed a relatively integrated business process and projects service system after long-term development. Supported by corresponding policies and industrial regulations, GPOs have made a great contribution to control the growth of medical and healthcare expenses and improve the efficiency of medical institutions, and its development experience can enlighten the practices in China.展开更多
Applying qualitative and quantitative methods, this article explains the driving forces behind U.S. President Donald Trump's decision to withdraw from the Paris Agreement, assesses the impacts of this withdrawal o...Applying qualitative and quantitative methods, this article explains the driving forces behind U.S. President Donald Trump's decision to withdraw from the Paris Agreement, assesses the impacts of this withdrawal on the compliance prospects of the agreement, and proposes how China should respond. The withdrawal undercuts the foundation of global climate governance and upsets the process of climate cooperation, and the impacts are manifold. The withdrawal undermines the universality of the Paris Agreement and impairs states' confidence in climate cooperation; it aggravates the leadership deficit in addressing global climate issues and sets a bad precedent for international climate cooperation. The withdrawal reduces other countries' emission space and raises their emission costs, and refusal to contribute to climate aid makes it more difficult for developing countries to mitigate and adapt to climate change. Cutting climate research funding will compromise the quality of future IPCC reports and ultimately undermine the scientific authority of future climate negotiations. China faces mounting pressure from the international community to assume global climate leadership after the U.S. withdraws, and this article proposes that China should reach the high ends of its domestic climate targets under the current Nationally Determined Contributions; internationally, China should facilitate the rebuilding of shared climate leadership, replacing the G2 with C5. Meanwhile, China needs to keep the U.S. engaged in climate cooperation.展开更多
基金the Vermont Agricultural Experiment Station at the University Vermont,USA,and the National Social Science Fund of China(17ZDA067)for financial support of this project。
文摘This study examines the development and trends of China’s alfalfa market and imports, identifies key factors for the rapid increase in China’s alfalfa imports, and discusses potential impacts of the U.S.-China trade dispute and retaliations on the alfalfa markets and trade in both nations. China’s rapid transition toward larger-scale commercial dairy production, with enhanced feed and cost management as well as quality and safety control, and its limited resources for high-quality alfalfa production are key factors for the dramatic increase in its alfalfa imports, from 19 601 metric tons in 2008 to 1.38 million metric tons(mmt) in 2018. While the United States dominated China’s alfalfa imports with an average share of 97.01% from 2007 to 2017, the share dropped to 83.76% in 2018 and 63.28% in January 2019 due to the trade dispute and retaliations started in 2018. China will likely remain a large importer of alfalfa because of both its growing demand and the comparative advantages of imported alfalfa in quality and price, but the imports from the United States will be highly affected by the ongoing trade dispute and negotiations. China is also expected to make more efforts to reduce its dependence on U.S. alfalfa through increased investment in domestic alfalfa production and identification of alternative sources of alfalfa and other hay imports.
文摘语言作为人类精神的产物和文明的载体应具有审美价值,而演讲作为一种特殊的语言表现形式,它的审美价值在于能够使受众在愉悦中自觉地去接受或容纳演讲的主旨。Speech on Hitler’s Invasion of the U.S.S.R.是丘吉尔政治生涯中重要的演讲作品之一,既具有时效性和实效性,又具有历久弥新的语言审美价值。
文摘The United States passed the Better Utilization of Investment Leading to Development(BUILD Act),as a counterweight to China’s overseas development activities.Under the Act,the US established a new federal agency,the U.S.International Development Finance Corporation(DFC),to enhance U.S.development financing capabilities.To better understand the impact of the DFC on China’s development finance,this article analyzes the DFC’s purpose,functions,structure,and funding.Then it focuses on the purpose of establishing the DFC,providing a preliminary analysis of the potential motivation for its establishment.It also compares the China Development Bank(CDB)and the DFC based on their focused sectors.Finally,through an in-depth analysis of financial frictions in China-U.S.relations,this article argues that the DFC competes with China’s overseas development financing activities in the context of broader strategic competition between China and the U.S.
文摘The global community has prepared for the withdrawal of the U.S. from the Paris Agreement since Donald Trump was elected as the president of the U.S. However, Trump's formal declaration of withdrawal still caused worldwide reaction. Trump will use the withdrawal to build his political reputation and to renegotiate the Paris Agreement despite its negative effects on the political credibility, international relationships, and potential long-term economic growth of the U.S. In general, the withdrawal of the U.S. from the Paris Agreement will not change the development of low-carbon technologies and the transformation trend of the global climate governance regime. However, the long-term goals and international cooperation on climate change will be affected by budget cuts in American climate change research and the cancelation of donations from the multilateral environmental fund of the U.S. If the Paris Agreement is renegotiated, the common but differentiated principle of responsibility of the United Nations Framework Convention on Climate Change will be challenged again. Nevertheless, climate change governance remains a main theme of future sustainable development. Instead of national governments, local governments and non-governmental organizations will develop strategies for technical innovation and emphasize pragmatic cooperation, thus expanding their roles in climate change governance. The capacity building on climate change research and public awareness should be enhanced as a long-term objective of global climate change governance.
基金This study was supported by the 2017 National Natural Science Foundation Project “The Impacts of U.S. Withdrawal from Paris Agreement on Global Climate Governance and China's Response”.
文摘Based on the Computable General Equilibrium (CGE) model and scenario analysis, the impacts of the U.S. withdrawal from the Paris Agreement on the carbon emission space and mitigation cost in China, European Union (EU), and Japan are assessed under Nationally Determined Contributions (NDCs) and 2 C scenarios due to the changed emission pathway of the U.S. The results show that, under the condition of constant global cumulative carbon emissions and a fixed burden-sharing scheme among countries, the failure of the U.S. to honor its NDC commitment to different degrees will increase the U.S. carbon emission space and decrease its mitigation cost. However, the carbon emission space of other parties, including China, EU, and Japan, will be reduced and their mitigation costs will be increased. In 2030, under the 2 C target, the carbon price will increase by 4.4e14.6 US$ t1 in China, by 9.7e35.4 US$ t1 in the EU, and by 16.0e53.5 US$ t1 in Japan. In addition, China, EU, and Japan will incur additional Gross Domestic Production (GDP) loss. Under the 2 C target, the GDP loss of China would increase by US$22.0e71.1 billion (equivalent to 16.4e53.1 US$ per capita), the EU's GDP loss would increase by US$9.4e32.1 billion (equivalent to 20.7e71.1 US$ per capita), and Japan's GDP loss will increase by US$4.1e13.5 billion (equivalent to 34.3e111.6 US$ per capita).
基金supported by a NIOSH Capacity Building grant (No. 200-2016-90154) to Drs. G. Walton and E. Holley and collaborators at the Colorado School of Mines
文摘The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.
基金supported by the National Nature Science Foundation of China (Grant No. 41401604)the Central Universities Fund Project of Southwest Minzu University (Grant No. 2019SYB07)
文摘Accessibility is a factor affecting national park visitation.However,the effect of accessibility on national park visitation is not fully understood.This paper examines the relationship between U.S.national park visitation and accessibility.First,the global and local accessibility indexes of each park unit are computed based on an accessibility model that takes into account the surrounding population and its proximity to the park unit.Integrated in the model is a distance decay coefficient that is derived from U.S.national park visitor surveys and therefore pertinent to the case of study.Then correlation analysis is performed between park visitation and accessibility based on park types,regions,and visitation types.Results show that total visitation is positively related to accessibility in National Memorials,Military Parks and Battlefield Parks/Sites but negatively related to accessibility in national parks and national monuments.However,recreational overnight stay visits are commonly negatively correlated to accessibility for almost all park types.Moreover,local accessibility index displays enhanced correlation coefficients with improved significance levels in many categories of analysis.Results suggest that historical/cultural national parks which often show positive correlations tend to attract more local visitors,but nature-based parks which mainly show negative correlations tend to attract more distant visitors.
基金This study was sponsored by the Earth Engineering Center of Columbia University in the City of New York.
文摘Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of waste were landfilled in 2017.In total,these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG(Landfill Gas)generation accurately,or collect most of the LFG generated.This study was based on the hypothesis that,on the average,methane generation is proportional to the tonnage of wastes landfilled annually.The Landfill Methane Outreach Program of the EPA(EPA-LMOP)compiles annual operating data of all methane-capturing landfills.Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured,i.e.,an average capture of 0.024-ton CH4/ton waste.On the basis of the anaerobic reaction of the DOC(Degradable Organic Carbon)in landfilled wastes,the average rate of methane generation from all operating U.S.landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity;this number corresponds to bioreaction of about one half of the total organic carbon in MSW.On this basis,the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture,48%.Adding up all 1,164 operating landfills,their total emission of methane was estimated at 11.9 million metric tons of CH4.At CH4/CO2 equivalence of 25,this number corresponds to CO2-eq emissions of 270 million metric tons,i.e.,5.1%of the U.S.energy related carbon dioxide emissions.
文摘Canola (Brassica napus L.) has potential to become alternative cash crop (healthy oil for human and meals for animal uses) with tremendous rotational benefits in the Southwestern U.S., a region dominated by cereal-fallow cropping systems. However, information on optimum planting date for its successful production is limited. Field experiments were conducted in 2011-12 and 2012-13 seasons under irrigation condition to study the response of canola growth and yield to planting dates at Clovis, NM. Three planting dates (mid-September, late-September and early-October) and four canola varieties (early flowering: DKW41-10 and DKW46-15;medium flowering: Riley and Wichita) are studied. Fall plant stand density is significantly higher for early-October than mid- and late-September plantings. However, a ratio of fall to spring plant stand density indicates a greater reduction in spring plant stand density with early-October (25%) and mid-September (19%) than late-September (7%). Vegetative (by 13 days) and flowering (by 7 days) duration phases are significantly shortened with delay in planting. The decline in aboveground dry matter (DM) due to delayed planting resulted in significant seed yield reduction in both 2011-12 (26%) and in 2012-13 (8%) when early-October and mid-September plantings were compared. There was a positive relationship between final DM and canola seed yield, accounting for 84 and 34% variation for 2011-12 and 2012-13 seasons, respectively with the 2011-12 environmental conditions being conducive for genetically controlled variation in DM production to be more apparent and strong in explaining the variation in seed yield among varieties. Medium-flowering varieties produced higher DM (9741 vs. 8371 Kg•ha<sup>-1</sup>) and seed yield (2785 vs. 2035 Kg•ha<sup>-1</sup>) than early-flowering varieties. In addition to seed yield, DM can be used as an indirect selection criterion for seed yield in variety selection and appropriate planting dates including a guarantee for high crop residues (~75% of the total aboveground biomass) production to make canola a potential alternative cash and rotational break crop in the Southwestern U.S.
文摘A growing demand for passenger and freight transportation, combined with limited capital to expand the United States （U.S.） rail infrastructure, is creating pressure for a more efficient use of the current line capacity. This is further exacerbated by the fact that most passenger rail services operate on corridors that are shared with freight traffic. A capacity analysis is one alternative to address the situation and there are various approaches, tools, and methodologies available for application. As the U.S. continues to develop higher speed passenger services with similar characteristics to those in European shared-use lines, understanding the common methods and tools used on both continents grows in relevance. There has not as yet been a detailed investigation as to how each continent approaches capacity analysis, and whether any benefits could be gained from cross-pollination. This paper utilizes more than 50 past capacity studies from the U.S. and Europe to describe the different railroad capacity defini- tions and approaches, and then categorizes them, based on each approach. The capacity methods are commonly di- vided into analytical and simulation methods, but this paper also introduces a third, ＂combined simulation- analytical＂ category. The paper concludes that Europeanrail studies are more unified in terms of capacity, concepts, and techniques, while the U.S. studies represent a greater variation in methods, tools, and objectives. The majority of studies on both continents use either simulation or a combined simulation-analytical approach. However, due to the significant differences between operating philosophy and network characteristics of these two rail systems, European studies tend to use timetable-based simulation tools as opposed to the non-timetable-based tools commonly used in the U.S. rail networks. It was also found that validation of studies against actual operations was not typically completed or was limited to comparisons with a base model.
文摘基于美国U. S. NEWS最新发布的"最佳图书情报学研究生院排名"(Best Library and Information StudiesPrograms)和代表院校的专业课程安排,通过调查和比较研究的方法,综合分析美国图书情报与档案管理类专业课程建设特点,为我国图书情报与档案管理类学科的课程建设提供参考与借鉴.
文摘Distance higher education is an important component of the Chinese higher education.How to enhance the quality of distance higher education is one of the key issues to be addressed in the research areas of distance education and higher education.As a crucial step to quality improvement,the constitution of accreditation system in distance higher education balances the benefits of all parties involved.This paper explores the American accreditation system of higher education and distance education and concludes with suggestions for the constitution of the Chinese quality assurance system:1)establishing third-party institutions to share part of the government roles;2)constituting the accreditation system;3)setting up appropriate standards;4)publicizing results of quality assurance work;and 5)building internal quality assurance mechanism.This paper is aimed to provide some reference to the constitution of accreditation system of distance higher education in China,facilitate the solution of quality problems in distance education,and promote the continuous improvement and development of distance education in China.
文摘Objective To study the characteristics, specific functions and policy improvement process of the Group Purchasing Organizations (GPOs) in the U.S. and to provide references for drug group purchasing practices in China. Methods Domestic and foreign relevant literatures, websites were reviewed or searched to analyze the functions and policy improvement process of the GPOs in the U.S. so as to provide references for drug group purchasing practices in China. Results and Conclusion As a third party in the U.S. GPOs has formed a relatively integrated business process and projects service system after long-term development. Supported by corresponding policies and industrial regulations, GPOs have made a great contribution to control the growth of medical and healthcare expenses and improve the efficiency of medical institutions, and its development experience can enlighten the practices in China.
基金This study was supported by the 2017 National Natural Science Foundation Project “The Impacts of U.S. Withdrawal from the Paris Agreement on Global Climate Governance and China's Response”.
文摘Applying qualitative and quantitative methods, this article explains the driving forces behind U.S. President Donald Trump's decision to withdraw from the Paris Agreement, assesses the impacts of this withdrawal on the compliance prospects of the agreement, and proposes how China should respond. The withdrawal undercuts the foundation of global climate governance and upsets the process of climate cooperation, and the impacts are manifold. The withdrawal undermines the universality of the Paris Agreement and impairs states' confidence in climate cooperation; it aggravates the leadership deficit in addressing global climate issues and sets a bad precedent for international climate cooperation. The withdrawal reduces other countries' emission space and raises their emission costs, and refusal to contribute to climate aid makes it more difficult for developing countries to mitigate and adapt to climate change. Cutting climate research funding will compromise the quality of future IPCC reports and ultimately undermine the scientific authority of future climate negotiations. China faces mounting pressure from the international community to assume global climate leadership after the U.S. withdraws, and this article proposes that China should reach the high ends of its domestic climate targets under the current Nationally Determined Contributions; internationally, China should facilitate the rebuilding of shared climate leadership, replacing the G2 with C5. Meanwhile, China needs to keep the U.S. engaged in climate cooperation.
