Hydrogen is emerging as a promising alternative to fossil fuels in the transportation sector.This study evaluated the feasibility of estab-lishing hydrogen refueling stations in five cities in Oman,Duqm,Haima,Sur,Al B...Hydrogen is emerging as a promising alternative to fossil fuels in the transportation sector.This study evaluated the feasibility of estab-lishing hydrogen refueling stations in five cities in Oman,Duqm,Haima,Sur,Al Buraymi,and Salalah,using Hybrid Optimization of Multiple Electric Renewables(HOMER)software.Three hybrid energy systems,photovoltaic-wind turbine-battery,photovoltaic-battery,and wind turbine-battery were analyzed for each city.Results indicated that Duqm offers the lowest net present cost(NPC),levelized cost of energy,and levelized cost of hydrogen,making it the most cost-effective location.Additionally,Sensitivity analysis showed that as the life of electrolyzer increases during operation,the initial capital expenditure is distributed over a longer operational period,leading to a reduction in the NPC.More so,renewable energy systems produced no emissions which supports Oman’s mission target.This comprehensive analysis confirms the feasibility of establishing a hydrogen refueling station in Duqm,Oman,and highlights advanced optimization techniques’superior capability in designing cost-effective,sustainable energy systems.展开更多
This study aims to analysis the influence of economic growth(EG)and energy consumption(EC)on sulfur dioxide emissions(SE)in China.Accordingly,this study explores the link between EG,EC,and SE for 30 provinces in China...This study aims to analysis the influence of economic growth(EG)and energy consumption(EC)on sulfur dioxide emissions(SE)in China.Accordingly,this study explores the link between EG,EC,and SE for 30 provinces in China over the span of 2000-2019.This study also analyzes cross-sectional dependence tests,panel unit root tests,Westerlund panel cointegration tests,Dumitrescu-Hurlin(D-H)causality tests.According to the test results,there is an inverted U-shaped association between EG and SE,and the assumption of the Environmental Kuznets Curve(EKC)is verified.The signs of EG and EC in the fixed effect(FE)and random effect(RE)methods are in line with those in the dynamic ordinary least squares(DOLS),fully modified ordinary least squares(FMOLS)and autoregressive distributed lag(ARDL)estimators.Moreover,the results verified that EC can obviously positive impact the SE.To reduce SE in China,government and policymakers can improve air quality by developing cleaner energy sources and improving energy efficiency.This requires the comprehensive use of policies,regulations,economic incentives,and public participation to promote sustainable development.展开更多
Developing a green economy is key to achieving the 2030 Sustainable Development Goals. This paper uses the SBM-GML index, which includes non-desired outputs, to measure the trend of regional green economic efficiency ...Developing a green economy is key to achieving the 2030 Sustainable Development Goals. This paper uses the SBM-GML index, which includes non-desired outputs, to measure the trend of regional green economic efficiency changes and analyze the impact mechanism and realization path of industrial transformation on green economic efficiency. The research results show that advanced industrial structure has a positive influence on green economic efficiency nationwide, while energy utilization structure and energy utilization efficiency have positive partial intermediary effects in the influence path;industrial structure rationalization is also significantly positively related to green economic efficiency nationwide, and the mediating effect of energy utilization is positive. The impact of industrial transformation on green economic efficiency has regional heterogeneity, and the mediating effect of energy use also differs. Among them, the impact effect in the eastern region is basically consistent with the national sample, but is negative in the central and western regions. This paper proposes countermeasures in terms of adjusting the industrial structure, improving energy efficiency, and perfecting industrial and energy policies, which can provide theoretical and practical references for promoting the transformation and upgrading of regional industrial structure, optimizing energy utilization, and advancing the efficiency of the national and regional green economy.展开更多
The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set(VCTS)at a minimal but safe distance.To guarantee collision avoidance,the safety distance should be calcula...The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set(VCTS)at a minimal but safe distance.To guarantee collision avoidance,the safety distance should be calculated using the state-of-the-art space-time separation principle that separates the Emergency Braking(EB)trajectories of two successive units during the whole EB process.In this case,the minimal safety distance is usually numerically calculated without an analytic formulation.Thus,the constrained VCTS control problem is hard to address with space-time separation,which is still a gap in the existing literature.To solve this problem,we propose a Distributed Economic Model Predictive Control(DEMPC)approach with computation efficiency and theoretical guarantee.Specifically,to alleviate the computation burden,we transform implicit safety constraints into explicitly linear ones,such that the optimal control problem in DEMPC is a quadratic programming problem that can be solved efficiently.For theoretical analysis,sufficient conditions are derived to guarantee the recursive feasibility and stability of DEMPC,employing compatibility constraints,tube techniques and terminal ingredient tuning.Moreover,we extend our approach with globally optimal and distributed online EB configuration methods to shorten the minimal distance among VCTS.Finally,experimental results demonstrate the performance and advantages of the proposed approaches.展开更多
In 2000 and 2001, 1-year-old seedlings of 7 economic tree species including chestnut, apricot, persimmon, peach, walnut, pear and apple were cultured in garden pots that had a diameter of 40 cm and were filled with cl...In 2000 and 2001, 1-year-old seedlings of 7 economic tree species including chestnut, apricot, persimmon, peach, walnut, pear and apple were cultured in garden pots that had a diameter of 40 cm and were filled with clean sand. The major components of exudates released from their roots were isolated and analysed by GC-MS. Totally 200 kinds of organic chemicals were isolated, of which 3 kinds i.e. naphthalene, dimethylbenzene and dibutyl phthalate were principally controlled pollutants according to 'Blacklist of Principal Environment Pollutants in China' and the standard of U.S. Environmental Protection Agency (EPA). The research result provided theoretical evidence for selecting low-pollution economic forest crops in the water source protection area in Miyun Reservoir.展开更多
The integration of linguistics and economics, economics of language, is a new peripheral subject based on theory of west ern human capital and educational economics. Catchwords which reflect many theories of economics...The integration of linguistics and economics, economics of language, is a new peripheral subject based on theory of west ern human capital and educational economics. Catchwords which reflect many theories of economics of language enter into people's scope of research. Study of catchword is of great significance for the enrichment of research of human language.展开更多
From the perspective of Language Economics,language education(including second language or foreign language education)is an economically valuable investment that has the function of promoting social development.Howeve...From the perspective of Language Economics,language education(including second language or foreign language education)is an economically valuable investment that has the function of promoting social development.However,there is an imbalance in the input and output of China’s college English education.From the perspective of language economics,this article focuses on the reform of College English courses in order to improve the efficiency of English teaching in common universities.展开更多
以国际权威期刊《Forest Policy and Economics》为例,选取其2007—2017年刊发的与中国林业经济问题相关的文献,从国际视角对中国林业经济问题进行梳理与总结。基于统计分析,刊发的文献总体呈现数量波动增长、内容多样化、合作形式国际...以国际权威期刊《Forest Policy and Economics》为例,选取其2007—2017年刊发的与中国林业经济问题相关的文献,从国际视角对中国林业经济问题进行梳理与总结。基于统计分析,刊发的文献总体呈现数量波动增长、内容多样化、合作形式国际化,研究区域具体化,定量分析为主等特点。从林产品贸易、森林资源经营管理、森林转型等主题展开对中国林业经济研究的论述,以期为我国相关学者全面把握中国林业经济前沿研究进展和发展趋势提供参考与借鉴。展开更多
Because forecasting a development program during the target selection phase of exploration for coalbed methane （CBM） is impossible, the conventional method that relies on a conceptual （or detailed） development pro...Because forecasting a development program during the target selection phase of exploration for coalbed methane （CBM） is impossible, the conventional method that relies on a conceptual （or detailed） development pro- gram cannot be used during the economic evaluation of CBM resources. Hence, this study focuses on establishing an economic evaluation model based on the characteristics of the target selection phase. The discounted cashflow method is applied to the construction of the model with the assumption that there is a uniform distribution of produc- tion wells. The computational error generated by the assumption is corrected by introducing a correction factor based on the production profile of single CBM wells. The case study demonstrates that the blocks lacking economic value can be screened out, and the most advantageous targets can be found by computing the resource values in the best- and worst-case scenarios. This technique can help to reduce wasted investments and improve the quality of decision-making in selecting targets for exploration.展开更多
In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formul...In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formulated in a simple and consistent manner. Selective maintenance problem under economic dependence(EDSMP) is presented based on a series–parallel system in this paper. A case study shows that the system reliability is promoted to a certain extent, which can validate the validity of the EDSMP model. The influence of the ratio of set-up cost on system performance is mainly discussed under different economic dependences. Several existing improvements of classical exhaust algorithm are further modified to solve a large sized EDSMP rapidly. Experimental results illustrate that these improvements can reduce CPU time significantly.Furthermore the contribution of each improvement is defined here, and then their contributions are compared thoroughly.展开更多
Background： Forest managers must deal with inherently stochastic ecological and economic processes. The future growth of trees is uncertain, and so is their value. The randomness of low-impact, high frequency or rare...Background： Forest managers must deal with inherently stochastic ecological and economic processes. The future growth of trees is uncertain, and so is their value. The randomness of low-impact, high frequency or rare catastrophic shocks in forest growth has significant implications in shaping the mix of tree species and the forest landscape. In addition, the fluctuations of wood prices influence greatly forest revenues. Methods： Markov decision process models （MDPs） offer a rigorous and practical way of developing optimum management strategies, given these multiple sources of risk. Results： Examples illustrate how such management guidelines are obtained with MDPs for combined ecological and economic objectives, including diversity of tree species and size, landscape diversity, old growth preservation, and carbon sequestration. Conclusions： The findings illustrate the power of the MDP approach to deal with risk in forest resource management. They recognize that the future is best viewed in terms of probabilities. Given these probabilities, MDPs tie optimum adaptive actions strictly to the state of the forest and timber prices at decision time. The methods are theoretically rigorous, numerically efficient, and practical for field implementation.展开更多
Homestead forests contribute substantially to the rural econ- omy of Bangladesh. Rural people depend on trees and plants for their energy usage, housing, food and other forms of subsistence livelihood. In order to ide...Homestead forests contribute substantially to the rural econ- omy of Bangladesh. Rural people depend on trees and plants for their energy usage, housing, food and other forms of subsistence livelihood. In order to identify the potential role of forests on homestead dwellers, an empirical field investigation was conducted in the four Upazilas of My- mensingh district of Bangladesh. It was found that land holdings of the respondents within the four sites are the highest in Mymensingh. The study made an important observation that among all homestead vegeta- tion between 5-6 years old, tree species are generally preferred over plants. This is perhaps due to the efforts of the social forestry extension service to demonstrate that planting trees is an important long-term in- vestment. In all four Upazilas, there was a significant correlation between household annual income and homestead forestry, agriculture and fisher- ies practice, suggesting that higher income families tend to have larger holdings of homesteads, farms and pond areas. Three Upazilas displayed a strong positive relationship （nearly 45%） between homestead forest areas and annual family income; however, the Fulbaria Upazila showed a very poor relationship （0.2%） in this regard. The results of this study suggest that homestead forests play a positive role in the rural economy, in addition to helping mitigate the increasing problem of deforestation in Bangladesh.展开更多
This paper presents a modified sliding mode control for fractional-order chaotic economical systems with parameter uncertainty and external disturbance. By constructing the suitable sliding mode surface with fractiona...This paper presents a modified sliding mode control for fractional-order chaotic economical systems with parameter uncertainty and external disturbance. By constructing the suitable sliding mode surface with fractional-order integral, the effective sliding mode controller is designed to realize the asymptotical stability of fractional-order chaotic economical systems. Comparing with the existing results, the main results in this paper are more practical and rigorous. Simulation results show the effectiveness and feasibility of the proposed sliding mode control method.展开更多
The challenges in the chemical processing industry today are environmental concerns, energy and capital costs. Catalytic distillation(CD) is a green reactor technology which combines a catalytic reaction and separatio...The challenges in the chemical processing industry today are environmental concerns, energy and capital costs. Catalytic distillation(CD) is a green reactor technology which combines a catalytic reaction and separation via distillation in the same distillation column. Utilization of CD in chemical process development could result in capital and energy savings, and the reduction of greenhouse gases. The efficacy of CD and the economic merits, in terms of energy and equipment savings, brought by CD for the production of biodiesel from waste oil such as yellow grease is quantified. Process flow sheets for industrial routes for an annual production of 10 million gallon ASTM purity biodiesel in a conventional process(reactor followed by distillation) and CD configurations are modeled in Aspen Plus. Material and energy flows, as well as sized unit operation blocks, are used to conduct an economic assessment of each process. Total capital investment, total operating and utility costs are calculated for each process. The waste oil feedstock is yellow grease containing both triglyceride and free fatty acid. Both transesterification and esterification reactions are considered in the process simulations. Results show a significant advantage of CD compared to a conventional biodiesel processes due to the reduction of distillation columns, waste streams and greenhouse gas emissions. The significant savings in capital and energy costs together with the reduction of greenhouse gases demonstrate that process intensification via CD is a feasible and new green process for the biodiesel production from waste oils.展开更多
Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that c...Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that can be bundled with solar PV to improve the economic feasibility of long-distance transmitted power. In this paper, a quantification model is established taking into account the regulating capacity of the reservoir, the characteristics of solar generation, and cost of hydro and solar PV with long-distance transmission based on the installed capacity ratio of hydro–solar hybrid power. Results indicate that for hydropower stations with high regulating capacity and generation factor of approximately 0.5, a hydro–solar installed capacity ratio of 1:1 will yield overall optimal economic performance, whereas for hydropower stations with daily regulating capacity reservoir and capacity factor of approximately 0.65, the optimal hydro–solar installed capacity ratio is approximately 1:0.3. In addition, the accuracy of the approach used in this study is verified through operation simulation of a hydro–solar hybrid system including ultra high-voltage direct current(UHVDC) transmission using two case studies in Africa.展开更多
This study was performed in five villages of Sandwip Upazila, Chittagong district with a view to identify the tree resources, utilization pattern and economic return of major fruit and timber tree species. Information...This study was performed in five villages of Sandwip Upazila, Chittagong district with a view to identify the tree resources, utilization pattern and economic return of major fruit and timber tree species. Information collected from a total of 60 households ranging from marginal, small, medium and large categories. Number of plant species increased with the increase of homestead area. A total of 33 plant species were recorded from the homegarden, of which 19 were fruit and 14 were timber tree species. Considerable number of vegetables was also planted under the shade of the homestead trees. The investment analysis showed that average benefit-cost ratios were greater than one, net present values were positive and internal rate of returns were more than 10%. Long term investment on horticulture and timber tree species is highly profitable if species like Artocarpus heterophyllus, Cocos nucifera, Tectona grandis and Swietenia macrophylla are planted.展开更多
This study aims to investigate the influence of rapid economic development on pollution at the municipal level in China.It constructs a Stochastic Impacts by Regression on Population,Affluence and Technology model(STI...This study aims to investigate the influence of rapid economic development on pollution at the municipal level in China.It constructs a Stochastic Impacts by Regression on Population,Affluence and Technology model(STIRPAT model) and uses comprehensive municipal data on industrial pollution and economic performance.The dataset contains 290 cities from2003 to 2016 as a sample for the panel data analysis.The study further separates the cities into two groups by their levels of economic development for heterogeneity analysis.It reveals that a low level of economic development would aggravate environmental pollution,and when the economy reaches a high level,this economic development will improve environmental quality.We also find that the relationships between foreign direct investment and industrial dust and sulfur dioxide(SO_2) discharge are significant,while the relationship between economic growth and effluent emission is not.The more developed subsample cities present an inverted U-shaped curve between industrial pollutant emission,GDP per capita,and foreign direct investment,while the less developed subsamples show no such relationship.Since the shape of these curves differs among regions,their turning points vary accordingly.Based on this finding,this study suggests that the governments of more developed cities should balance environmental pollution and economic development by enhancing environmental regulations and adjusting industrial structure.展开更多
Power transmission across the sea is an important part of global energy interconnection(GEI).To support the construction of GEI and to serve the needs of future clean energy trans-sea transportation and offshore wind ...Power transmission across the sea is an important part of global energy interconnection(GEI).To support the construction of GEI and to serve the needs of future clean energy trans-sea transportation and offshore wind power development,this study a)analyzes the requirements of the GEI backbone network pertaining to direct current(DC)submarine cable technology,and b)defines the key technical and economic indices of ultrahigh-voltage direct current(UHVDC)submarine cable based on theoretical computations.The research is based on the thermoelectric coupling model and the finite element method.It is shown that the dielectric strength of the insulating materials of the±800 kV~±1100 kV/4000 MW^12000 MW UHVDC submarine cable(extrusion insulation)should be not less than 43~65 kV/mm,while the heat resistance is not less than 110°C.As the cost of submarine cable is 5~10 times higher than that of the overhead line,the project investment need to be decreased to a level within the economical carrying capacity to guarantee extensive applicability of the HVDC submarine cable technology.展开更多
The development of coalbed methane (CBM) in China poses great difficulties because of high investments, low produc- tion and high risks. So a study of the economic effect of a single well at its preliminary stage is h...The development of coalbed methane (CBM) in China poses great difficulties because of high investments, low produc- tion and high risks. So a study of the economic effect of a single well at its preliminary stage is helpful for commercial exploitation of CBM. Affected by wellbore flow pressure, initial reservoir pressure, relative permeability, Langmuir pressure and other factors, the trend of declining production of a single CBM well agrees, by and large, with a hyperbolic pattern of decline. Based on Arps’s equation, nearly 200 wells production with different peak yields and initial rates of were simulated. Given the present cost of drill- ing, gas production and engineering on the ground, the gross investment for the development of a single coalbed methane well was estimated for the Fanzhuang block in central China. Considering the current industrial policies for CBM, we established an eco- nomic assessment model and analyzed economic peaks. The results show the economic benefits with or without government subsi- dies at different peak yields of a single CBM well. The results of the evaluation can be directly applied in the Fanzhuang block. The evaluation method, formulated in our study, can be used to other areas with similar conditions.展开更多
This paper presents a very simple method to derive the explicit transformations of the optimal economical 1 to M phase-covariant cloning. The fidelity of clones reaches the theoretic bound [D＇Ar]ano G M and Macchiave...This paper presents a very simple method to derive the explicit transformations of the optimal economical 1 to M phase-covariant cloning. The fidelity of clones reaches the theoretic bound [D＇Ar]ano G M and Macchiavello C 2003 Phys. Rev. A 67 042306]. The derived transformations cover the previous contributions [Delgado Y, Lamata Let al, 2007 Phys. Rev. Lett. 98 150502] in which M must be odd.展开更多
文摘Hydrogen is emerging as a promising alternative to fossil fuels in the transportation sector.This study evaluated the feasibility of estab-lishing hydrogen refueling stations in five cities in Oman,Duqm,Haima,Sur,Al Buraymi,and Salalah,using Hybrid Optimization of Multiple Electric Renewables(HOMER)software.Three hybrid energy systems,photovoltaic-wind turbine-battery,photovoltaic-battery,and wind turbine-battery were analyzed for each city.Results indicated that Duqm offers the lowest net present cost(NPC),levelized cost of energy,and levelized cost of hydrogen,making it the most cost-effective location.Additionally,Sensitivity analysis showed that as the life of electrolyzer increases during operation,the initial capital expenditure is distributed over a longer operational period,leading to a reduction in the NPC.More so,renewable energy systems produced no emissions which supports Oman’s mission target.This comprehensive analysis confirms the feasibility of establishing a hydrogen refueling station in Duqm,Oman,and highlights advanced optimization techniques’superior capability in designing cost-effective,sustainable energy systems.
文摘This study aims to analysis the influence of economic growth(EG)and energy consumption(EC)on sulfur dioxide emissions(SE)in China.Accordingly,this study explores the link between EG,EC,and SE for 30 provinces in China over the span of 2000-2019.This study also analyzes cross-sectional dependence tests,panel unit root tests,Westerlund panel cointegration tests,Dumitrescu-Hurlin(D-H)causality tests.According to the test results,there is an inverted U-shaped association between EG and SE,and the assumption of the Environmental Kuznets Curve(EKC)is verified.The signs of EG and EC in the fixed effect(FE)and random effect(RE)methods are in line with those in the dynamic ordinary least squares(DOLS),fully modified ordinary least squares(FMOLS)and autoregressive distributed lag(ARDL)estimators.Moreover,the results verified that EC can obviously positive impact the SE.To reduce SE in China,government and policymakers can improve air quality by developing cleaner energy sources and improving energy efficiency.This requires the comprehensive use of policies,regulations,economic incentives,and public participation to promote sustainable development.
基金supported by National Natural Science Foundation of China [grant numbers 42371194]。
文摘Developing a green economy is key to achieving the 2030 Sustainable Development Goals. This paper uses the SBM-GML index, which includes non-desired outputs, to measure the trend of regional green economic efficiency changes and analyze the impact mechanism and realization path of industrial transformation on green economic efficiency. The research results show that advanced industrial structure has a positive influence on green economic efficiency nationwide, while energy utilization structure and energy utilization efficiency have positive partial intermediary effects in the influence path;industrial structure rationalization is also significantly positively related to green economic efficiency nationwide, and the mediating effect of energy utilization is positive. The impact of industrial transformation on green economic efficiency has regional heterogeneity, and the mediating effect of energy use also differs. Among them, the impact effect in the eastern region is basically consistent with the national sample, but is negative in the central and western regions. This paper proposes countermeasures in terms of adjusting the industrial structure, improving energy efficiency, and perfecting industrial and energy policies, which can provide theoretical and practical references for promoting the transformation and upgrading of regional industrial structure, optimizing energy utilization, and advancing the efficiency of the national and regional green economy.
基金supported by the National Natural Science Foundation of China(52372310)the State Key Laboratory of Advanced Rail Autonomous Operation(RAO2023ZZ001)+1 种基金the Fundamental Research Funds for the Central Universities(2022JBQY001)Beijing Laboratory of Urban Rail Transit.
文摘The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set(VCTS)at a minimal but safe distance.To guarantee collision avoidance,the safety distance should be calculated using the state-of-the-art space-time separation principle that separates the Emergency Braking(EB)trajectories of two successive units during the whole EB process.In this case,the minimal safety distance is usually numerically calculated without an analytic formulation.Thus,the constrained VCTS control problem is hard to address with space-time separation,which is still a gap in the existing literature.To solve this problem,we propose a Distributed Economic Model Predictive Control(DEMPC)approach with computation efficiency and theoretical guarantee.Specifically,to alleviate the computation burden,we transform implicit safety constraints into explicitly linear ones,such that the optimal control problem in DEMPC is a quadratic programming problem that can be solved efficiently.For theoretical analysis,sufficient conditions are derived to guarantee the recursive feasibility and stability of DEMPC,employing compatibility constraints,tube techniques and terminal ingredient tuning.Moreover,we extend our approach with globally optimal and distributed online EB configuration methods to shorten the minimal distance among VCTS.Finally,experimental results demonstrate the performance and advantages of the proposed approaches.
基金The study was supported by Natural Science Foundation of Beijing to Wang Yuzhu (No. 6992013).
文摘In 2000 and 2001, 1-year-old seedlings of 7 economic tree species including chestnut, apricot, persimmon, peach, walnut, pear and apple were cultured in garden pots that had a diameter of 40 cm and were filled with clean sand. The major components of exudates released from their roots were isolated and analysed by GC-MS. Totally 200 kinds of organic chemicals were isolated, of which 3 kinds i.e. naphthalene, dimethylbenzene and dibutyl phthalate were principally controlled pollutants according to 'Blacklist of Principal Environment Pollutants in China' and the standard of U.S. Environmental Protection Agency (EPA). The research result provided theoretical evidence for selecting low-pollution economic forest crops in the water source protection area in Miyun Reservoir.
文摘The integration of linguistics and economics, economics of language, is a new peripheral subject based on theory of west ern human capital and educational economics. Catchwords which reflect many theories of economics of language enter into people's scope of research. Study of catchword is of great significance for the enrichment of research of human language.
文摘From the perspective of Language Economics,language education(including second language or foreign language education)is an economically valuable investment that has the function of promoting social development.However,there is an imbalance in the input and output of China’s college English education.From the perspective of language economics,this article focuses on the reform of College English courses in order to improve the efficiency of English teaching in common universities.
文摘以国际权威期刊《Forest Policy and Economics》为例,选取其2007—2017年刊发的与中国林业经济问题相关的文献,从国际视角对中国林业经济问题进行梳理与总结。基于统计分析,刊发的文献总体呈现数量波动增长、内容多样化、合作形式国际化,研究区域具体化,定量分析为主等特点。从林产品贸易、森林资源经营管理、森林转型等主题展开对中国林业经济研究的论述,以期为我国相关学者全面把握中国林业经济前沿研究进展和发展趋势提供参考与借鉴。
基金funded by the Beijing Natural Science Foundation (9144033)the National Social Science Fund for Major Projects (11&ZD164)
文摘Because forecasting a development program during the target selection phase of exploration for coalbed methane （CBM） is impossible, the conventional method that relies on a conceptual （or detailed） development pro- gram cannot be used during the economic evaluation of CBM resources. Hence, this study focuses on establishing an economic evaluation model based on the characteristics of the target selection phase. The discounted cashflow method is applied to the construction of the model with the assumption that there is a uniform distribution of produc- tion wells. The computational error generated by the assumption is corrected by introducing a correction factor based on the production profile of single CBM wells. The case study demonstrates that the blocks lacking economic value can be screened out, and the most advantageous targets can be found by computing the resource values in the best- and worst-case scenarios. This technique can help to reduce wasted investments and improve the quality of decision-making in selecting targets for exploration.
基金supported by the National Science Foundation of China (Grant No. 61305083)
文摘In view of the high complexity of the objective world, an economic dependence between subsystems(paired and unpaired) is proposed, and then the maintenance cost and time under different economic dependences are formulated in a simple and consistent manner. Selective maintenance problem under economic dependence(EDSMP) is presented based on a series–parallel system in this paper. A case study shows that the system reliability is promoted to a certain extent, which can validate the validity of the EDSMP model. The influence of the ratio of set-up cost on system performance is mainly discussed under different economic dependences. Several existing improvements of classical exhaust algorithm are further modified to solve a large sized EDSMP rapidly. Experimental results illustrate that these improvements can reduce CPU time significantly.Furthermore the contribution of each improvement is defined here, and then their contributions are compared thoroughly.
基金supported in part by the USDA Forest Service, Southern Research Station, through a cooperative research agreement with Joseph Buongiornodirected by Jeff Prestemonsupported in part by the USDA Mc Intire-Stennis fund WVA00105
文摘Background： Forest managers must deal with inherently stochastic ecological and economic processes. The future growth of trees is uncertain, and so is their value. The randomness of low-impact, high frequency or rare catastrophic shocks in forest growth has significant implications in shaping the mix of tree species and the forest landscape. In addition, the fluctuations of wood prices influence greatly forest revenues. Methods： Markov decision process models （MDPs） offer a rigorous and practical way of developing optimum management strategies, given these multiple sources of risk. Results： Examples illustrate how such management guidelines are obtained with MDPs for combined ecological and economic objectives, including diversity of tree species and size, landscape diversity, old growth preservation, and carbon sequestration. Conclusions： The findings illustrate the power of the MDP approach to deal with risk in forest resource management. They recognize that the future is best viewed in terms of probabilities. Given these probabilities, MDPs tie optimum adaptive actions strictly to the state of the forest and timber prices at decision time. The methods are theoretically rigorous, numerically efficient, and practical for field implementation.
基金financially supported by the Alexander von Humboldt Foundation, Germany
文摘Homestead forests contribute substantially to the rural econ- omy of Bangladesh. Rural people depend on trees and plants for their energy usage, housing, food and other forms of subsistence livelihood. In order to identify the potential role of forests on homestead dwellers, an empirical field investigation was conducted in the four Upazilas of My- mensingh district of Bangladesh. It was found that land holdings of the respondents within the four sites are the highest in Mymensingh. The study made an important observation that among all homestead vegeta- tion between 5-6 years old, tree species are generally preferred over plants. This is perhaps due to the efforts of the social forestry extension service to demonstrate that planting trees is an important long-term in- vestment. In all four Upazilas, there was a significant correlation between household annual income and homestead forestry, agriculture and fisher- ies practice, suggesting that higher income families tend to have larger holdings of homesteads, farms and pond areas. Three Upazilas displayed a strong positive relationship （nearly 45%） between homestead forest areas and annual family income; however, the Fulbaria Upazila showed a very poor relationship （0.2%） in this regard. The results of this study suggest that homestead forests play a positive role in the rural economy, in addition to helping mitigate the increasing problem of deforestation in Bangladesh.
基金supported by the National Natural Science Foundation of China(Grant Nos.51207173 and 51277192)
文摘This paper presents a modified sliding mode control for fractional-order chaotic economical systems with parameter uncertainty and external disturbance. By constructing the suitable sliding mode surface with fractional-order integral, the effective sliding mode controller is designed to realize the asymptotical stability of fractional-order chaotic economical systems. Comparing with the existing results, the main results in this paper are more practical and rigorous. Simulation results show the effectiveness and feasibility of the proposed sliding mode control method.
基金Financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC)
文摘The challenges in the chemical processing industry today are environmental concerns, energy and capital costs. Catalytic distillation(CD) is a green reactor technology which combines a catalytic reaction and separation via distillation in the same distillation column. Utilization of CD in chemical process development could result in capital and energy savings, and the reduction of greenhouse gases. The efficacy of CD and the economic merits, in terms of energy and equipment savings, brought by CD for the production of biodiesel from waste oil such as yellow grease is quantified. Process flow sheets for industrial routes for an annual production of 10 million gallon ASTM purity biodiesel in a conventional process(reactor followed by distillation) and CD configurations are modeled in Aspen Plus. Material and energy flows, as well as sized unit operation blocks, are used to conduct an economic assessment of each process. Total capital investment, total operating and utility costs are calculated for each process. The waste oil feedstock is yellow grease containing both triglyceride and free fatty acid. Both transesterification and esterification reactions are considered in the process simulations. Results show a significant advantage of CD compared to a conventional biodiesel processes due to the reduction of distillation columns, waste streams and greenhouse gas emissions. The significant savings in capital and energy costs together with the reduction of greenhouse gases demonstrate that process intensification via CD is a feasible and new green process for the biodiesel production from waste oils.
基金supported by the Global Energy Interconnection Group’s Science & Technology Project “Global Clean Energy Potential Estimating Model: Methodology and Application” (524500180011)
文摘Solar PV is expected to become the most cost-competitive renewable energy owing to the rapidly decreasing cost of the system. On the other hand, hydropower is a high-quality and reliable regulating power source that can be bundled with solar PV to improve the economic feasibility of long-distance transmitted power. In this paper, a quantification model is established taking into account the regulating capacity of the reservoir, the characteristics of solar generation, and cost of hydro and solar PV with long-distance transmission based on the installed capacity ratio of hydro–solar hybrid power. Results indicate that for hydropower stations with high regulating capacity and generation factor of approximately 0.5, a hydro–solar installed capacity ratio of 1:1 will yield overall optimal economic performance, whereas for hydropower stations with daily regulating capacity reservoir and capacity factor of approximately 0.65, the optimal hydro–solar installed capacity ratio is approximately 1:0.3. In addition, the accuracy of the approach used in this study is verified through operation simulation of a hydro–solar hybrid system including ultra high-voltage direct current(UHVDC) transmission using two case studies in Africa.
文摘This study was performed in five villages of Sandwip Upazila, Chittagong district with a view to identify the tree resources, utilization pattern and economic return of major fruit and timber tree species. Information collected from a total of 60 households ranging from marginal, small, medium and large categories. Number of plant species increased with the increase of homestead area. A total of 33 plant species were recorded from the homegarden, of which 19 were fruit and 14 were timber tree species. Considerable number of vegetables was also planted under the shade of the homestead trees. The investment analysis showed that average benefit-cost ratios were greater than one, net present values were positive and internal rate of returns were more than 10%. Long term investment on horticulture and timber tree species is highly profitable if species like Artocarpus heterophyllus, Cocos nucifera, Tectona grandis and Swietenia macrophylla are planted.
基金financially supported by the Major Program of National Social Science Foundation (No.16ZDA006)National Natural Science Foundation of China (Nos.71603193 and 71974151)Teaching and Research Project of Wuhan University (No.1201-413200127)。
文摘This study aims to investigate the influence of rapid economic development on pollution at the municipal level in China.It constructs a Stochastic Impacts by Regression on Population,Affluence and Technology model(STIRPAT model) and uses comprehensive municipal data on industrial pollution and economic performance.The dataset contains 290 cities from2003 to 2016 as a sample for the panel data analysis.The study further separates the cities into two groups by their levels of economic development for heterogeneity analysis.It reveals that a low level of economic development would aggravate environmental pollution,and when the economy reaches a high level,this economic development will improve environmental quality.We also find that the relationships between foreign direct investment and industrial dust and sulfur dioxide(SO_2) discharge are significant,while the relationship between economic growth and effluent emission is not.The more developed subsample cities present an inverted U-shaped curve between industrial pollutant emission,GDP per capita,and foreign direct investment,while the less developed subsamples show no such relationship.Since the shape of these curves differs among regions,their turning points vary accordingly.Based on this finding,this study suggests that the governments of more developed cities should balance environmental pollution and economic development by enhancing environmental regulations and adjusting industrial structure.
基金supported by the Global Energy Interconnection Group Co.,Ltd.Science and Technology Project(Project No.101662224/Title:UHV large-capacity DC submarine cable key technology and roadmap research)the National Key R&D Program of China(2016YFB0900702)
文摘Power transmission across the sea is an important part of global energy interconnection(GEI).To support the construction of GEI and to serve the needs of future clean energy trans-sea transportation and offshore wind power development,this study a)analyzes the requirements of the GEI backbone network pertaining to direct current(DC)submarine cable technology,and b)defines the key technical and economic indices of ultrahigh-voltage direct current(UHVDC)submarine cable based on theoretical computations.The research is based on the thermoelectric coupling model and the finite element method.It is shown that the dielectric strength of the insulating materials of the±800 kV~±1100 kV/4000 MW^12000 MW UHVDC submarine cable(extrusion insulation)should be not less than 43~65 kV/mm,while the heat resistance is not less than 110°C.As the cost of submarine cable is 5~10 times higher than that of the overhead line,the project investment need to be decreased to a level within the economical carrying capacity to guarantee extensive applicability of the HVDC submarine cable technology.
基金Project supported by the Creative Foundation for Young-Middle-Aged Researchers from CNPC 2006–2008
文摘The development of coalbed methane (CBM) in China poses great difficulties because of high investments, low produc- tion and high risks. So a study of the economic effect of a single well at its preliminary stage is helpful for commercial exploitation of CBM. Affected by wellbore flow pressure, initial reservoir pressure, relative permeability, Langmuir pressure and other factors, the trend of declining production of a single CBM well agrees, by and large, with a hyperbolic pattern of decline. Based on Arps’s equation, nearly 200 wells production with different peak yields and initial rates of were simulated. Given the present cost of drill- ing, gas production and engineering on the ground, the gross investment for the development of a single coalbed methane well was estimated for the Fanzhuang block in central China. Considering the current industrial policies for CBM, we established an eco- nomic assessment model and analyzed economic peaks. The results show the economic benefits with or without government subsi- dies at different peak yields of a single CBM well. The results of the evaluation can be directly applied in the Fanzhuang block. The evaluation method, formulated in our study, can be used to other areas with similar conditions.
基金supported by the National Natural Science Foundation of China (Grant No 10674001)the Program of the Education Department of Anhui Province of China (Grant No KJ2007A002)
文摘This paper presents a very simple method to derive the explicit transformations of the optimal economical 1 to M phase-covariant cloning. The fidelity of clones reaches the theoretic bound [D＇Ar]ano G M and Macchiavello C 2003 Phys. Rev. A 67 042306]. The derived transformations cover the previous contributions [Delgado Y, Lamata Let al, 2007 Phys. Rev. Lett. 98 150502] in which M must be odd.
