The larger the difference between the willingness scale of tobacco family farmers and the optimal scale of efficiency,the greater the degree of irrationality,and the higher the decision making risk.With the aid of DEA...The larger the difference between the willingness scale of tobacco family farmers and the optimal scale of efficiency,the greater the degree of irrationality,and the higher the decision making risk.With the aid of DEA model,this study calculated the optimal scale of efficiency of Guiyang tobacco family farms.Using the ratio of willingness scale and efficiency optimal scale,it measured the degree of irrationality of family farmers.In addition,with the help of multiple linear regression model,it explained the irrational decision making mechanism of family farmers.Finally,it made a portrait of farmers who tend to make irrational decisions,to find specific farmers and guide them in their production and operation,reduce the risk of planting scale decision making and stabilize the sustainable development of the tobacco industry.展开更多
Scale management remains the core position in entire development process of the economics and is a major issue of academic research and government concern. Focusing on related problems of agricultural scale management...Scale management remains the core position in entire development process of the economics and is a major issue of academic research and government concern. Focusing on related problems of agricultural scale management,this paper explored 4 aspects of past literature.( i) It defined the agricultural scale management based on economies of scale theory and changes in returns to scale.( ii) From the perspective of the returns to scale of grain production,there are changes in returns to scale of China's grain production,but the measured changes are not significant.( iii) Existing analysis on factors influencing agricultural scale management mainly includes factors influencing farmers' willingness of scale management and restrictive factors of implementation of scale management.( iv) In studies of the relationship between land management scale and production efficiency,many scholars made qualitative and quantitative analysis on land scale efficiency on the basis of economic indicators they defined,but they reached different conclusions. Finally,it summarized literature and pointed out several issues needing special attention in this field.展开更多
Since 2009, Chinese nonferrous metals industry has been carried out industry consolidation with strong support by the central government. This work examined technical efficiency of Chinese nonferrous metals firms and ...Since 2009, Chinese nonferrous metals industry has been carried out industry consolidation with strong support by the central government. This work examined technical efficiency of Chinese nonferrous metals firms and its change during the period of 2007 and 2011. Based on financial data from nonferrous metals listed companies, technical efficiency of nonferrous metal minerals mining firms and nonferrous metal smelting, pressing and processing firms was estimated respectively using the data envelopment analysis (DEA) method. It was found that, in both sectors, number of pure technical and scale inefficient firms dominated over efficient ones. Overall, their technical and scale efficiency tended to be very low after 2009. In particular, efficiency scores of nonferrous metal smelting, pressing and processing firms fluctuated greatly during the research period. And a limited number of large leading firms were able to maintain 100% efficiency score in the industry, while efficiency of most of other leading firms has declined since 2009.展开更多
Agricultural mechanization and custom machine services have developed rapidly in China,which can influence rice production efficiency in the future.We calculate technical efficiency,allocative efficiency,and scale eff...Agricultural mechanization and custom machine services have developed rapidly in China,which can influence rice production efficiency in the future.We calculate technical efficiency,allocative efficiency,and scale efficiency using data collected in 2015 from a face-to-face interview survey of 450 households that cultivated 3096 plots located in the five major rice-producing provinces of China.We use a one-step stochastic frontier model to calculate technical efficiency and regress the efficiency scores on socio-demographic and physical land characteristics to find the influencing variables.Variables influencing technical efficiency are compared at three different phases of rice cultivation.We also calculate technical efficiency by using the Heckman Selection Model,which addresses technological heterogeneity and self-selection bias.Results indicate that:(1)the average value of technical efficiency using a one-step stochastic frontier model was found to be 0.74.When self-selection bias is accounted for using the Heckman Selection Model,the average value of the technical efficiency increases to 0.80;(2)mechanization at the chemical application phase has a positive effect on technical efficiency,but mechanization does not affect efficiency at the plowing and harvesting phases;(3)machines are overused relative to both land and labor,and high machine input use on the small size of landholding has resulted in allocative inefficiency;(4)rice farmers are overwhelmingly operating at a sub-optimal scale.Future policies should focus on encouraging farmland transfer in rural areas to achieve scale efficiency and allocative efficiency while promoting mechanization at the chemical application phase of rice cultivation to improve technical efficiency.展开更多
Two-oriented agriculture was a complex organism coupling production,economics,society and ecology.Its development process was affected by various factors such as producers,nature,society,etc.In order to overcome measu...Two-oriented agriculture was a complex organism coupling production,economics,society and ecology.Its development process was affected by various factors such as producers,nature,society,etc.In order to overcome measurement error of traditional data envelopment analysis caused by ignoring random,three-stage DEA model was studied to remove environmental factors and random effects.On the foundation of this model was two-oriented agriculture comprehensive production efficiency of 14 cities were estimated in Hunan Province in 2008,and brown forth corresponding policy proposals to promote agricultural development.展开更多
Using the DEA analysis method,on the basis of the national panel data from 2002 to 2014,this paper made a comparative analysis on the rice production performance before and after the implementation of direct grain sub...Using the DEA analysis method,on the basis of the national panel data from 2002 to 2014,this paper made a comparative analysis on the rice production performance before and after the implementation of direct grain subsidy policy,and made an empirical analysis on the relationship between the direct grain subsidy policy and the changes in the rice production performance. The results showed that the effect of the direct grain subsidy policy on promoting the rice production performance is declining year by year,largely because drop of scale efficiency. Besides,there are problems of serious redundancy in agricultural subsidy,unreasonable resource allocation,leading to low performance and resource waste of rice production.展开更多
Making use of the DEA-based method of quadruplicate decomposition of labor productivity, the paper analyzes the influence of labor productivity of provincial textile industry in China, caused by the effect of technica...Making use of the DEA-based method of quadruplicate decomposition of labor productivity, the paper analyzes the influence of labor productivity of provincial textile industry in China, caused by the effect of technical efficiency, pure technical progress, changes of scale efficiency of capital per labor and of capital intensity from the year of 2002 to 2005. Its results show that the improvement of provincial textile industry labor productivity has mainly resulted from technical progress since 2003. Meanwhile, labor productivity of underdeveloped provinces has been growing faster than that of developed ones owing to technology diffusion. And then, the above-mentioned improvement has originated from the enhancement of capital deepening and technology efficiency. In addition, scale return of capital per labor appeared to decrease during the period from 2004 to 2005.展开更多
Small-scale household agricultural production has been in conflict with China's agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,resear...Small-scale household agricultural production has been in conflict with China's agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,research on the relationship between farm size and scale efficiency has become increasingly important.In this paper,we use the "DEA-OLS" two stage method to analyze data from 368 surveys of rice farming households in the Jianghan Plain.The scale efficiency of rice farming was calculated,and the relationship between farm size and scale efficiency investigated.The results indicate that(1) the rice farm size is generally small in Jianghan Plain,with an average of 0.77 ha.The average scale efficiency is 0.88,and it is the main factor limiting an increase in comprehensive technical efficiency.Moreover,88.32% of households are in the stage of increasing returns to scale.(2) There is a stable inverted "U" type relationship between rice farm size and scale efficiency.Considering characteristics of the householder,the household and land quality,the maximum scale efficiency corresponds to a household with 5 ha of rice farm.(3) Among householder characteristics,age has a significant negative influence on scale efficiency,and scale efficiency is lower for a household whose householder is engaged in non-farm work than for one whose householder is devoted to farming.As for land quality,there was a significant positive effect of irrigation on scale efficiency.Among family characteristics,the application of a machine during the seeding process increased scale efficiency by 3.07%.Therefore,we suggest that local government should actively promote rural land circulation,implement a staged-scale management subsidy,and other forms of support for the purchase of agricultural machinery and technical popularization.Increased investment in irrigation improvements and mechanical facilities and encouragement of farmers to enlarge their farm size could improve scale efficiency and farming profit and lead to the development of moderate scale management.展开更多
A comparison of the facts at the micro-and macro-level indicates that although some Chinese enterprises are at the international frontier in terms of micro-level energy efficiency,overall energy efficiency at the indu...A comparison of the facts at the micro-and macro-level indicates that although some Chinese enterprises are at the international frontier in terms of micro-level energy efficiency,overall energy efficiency at the industrial and national level is seriously lagging behind.Hypotheses based on a market segmentation framework indicate that this is because market segmentation inhibits energy efficiency through its effect on technical efficiency,scale efficiency and allocation efficiency.This effect has been demonstrated by empirical research based on Chinese provincial panel data.展开更多
Precipitation of calcium carbonate (CaCOs) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect...Precipitation of calcium carbonate (CaCOs) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one (scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca^2+ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80℃ at pH 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCOs changed from calcite to aragonite.展开更多
Molecular simulation was performed to study the interaction between CaCO3 crystal and several oligomer inhibitors, by using the equilibrium morphology method to calculate the growth morphology of CaCO3 without inhibit...Molecular simulation was performed to study the interaction between CaCO3 crystal and several oligomer inhibitors, by using the equilibrium morphology method to calculate the growth morphology of CaCO3 without inhibitors. The calculated morphology agreed well with SEM photographs. Then, a double-layer model was built to investigate the interaction between calcite crystal and oligomer inhibitors containing maleic anhydride (MA) and acrylic acid (AA). Interaction energy per gram of an oligomer inhibitor was introduced as a scale of inhibition efficiency of different monomers. The results indicated that, for calcite scale inhibition, acrylamide (AM) and vinyl phosphonic acid (VPA) were the most efficient monomers, while allylsulfonic acid (AS) was the poorest. Increasing proportion of AM in dimer inhibitor molecule would improve the inhibition efficiency of MA, though, for a trimer, such as MA-AA-AM, certain sequence of monomers in the inhibitor molecule was necessary besides higher proportion of AM.展开更多
China has five layers of government including the central government.Recently,some prefectural governments meet fiscal distress.We investigate the effects of urban and rural populations and area sizes on the expenditu...China has five layers of government including the central government.Recently,some prefectural governments meet fiscal distress.We investigate the effects of urban and rural populations and area sizes on the expenditures of the prefecture-level local government by estimating quintile regression.At around 220,000 people,per capita local government expenditure for urban populations is minimized in our simulation.The expenditure for rural populations is proportional to the population size.The expenditure in accordance with the areas is also proportional to the area size.The cost structure is the reason why China’s recent rapid urbanization increases prefectural government’s fiscal distress.展开更多
Promoting the growth of the lithium battery sector has been a critical aspect of China's energy policy in terms of achieving carbon neutrality.However,despite significant support on research and development(R&...Promoting the growth of the lithium battery sector has been a critical aspect of China's energy policy in terms of achieving carbon neutrality.However,despite significant support on research and development(R&D)investments that have resulted in increasing size,the sector seems to be falling behind in technological areas.To guide future policies and understand proper ways of promoting R&D efficiency,we looked into the lithium battery industry of China.Specifically,data envelopment analysis(DEA)was used as the primary approach based on evidence from 22 listed lithium battery enterprises.The performance of the five leading players was compared with that of the industry as a whole.Results revealed little indication of a meaningful improvement in R&D efficiency throughout our sample from 2010 to 2019.However,during this period,a significant increase in R&D expenditure was witnessed.This finding was supported,as the results showed that the average technical efficiency of the 22 enterprises was 0.442,whereas the average pure technical efficiency was at 0.503,thus suggesting that they were suffering from decreasing returns to scale(DRS).In contrast,the performance of the five leading players seemed superior because their average efficiency scores were higher than the industry's average.Moreover,they were experiencing increasing scale efficiency(IRS).We draw on these findings to suggest to policymakers that supporting technologically intensive sectors should be more than simply increasing investment scale;rather,it should also encompass assisting businesses in developing efficient managerial processes for R&D.展开更多
When both of the scaling and hydrate risks occur in deep water wells or subsea pipelines at the same time,the compatibility between scale and hydrate inhibitors should be paid more attention to for the risk prevention...When both of the scaling and hydrate risks occur in deep water wells or subsea pipelines at the same time,the compatibility between scale and hydrate inhibitors should be paid more attention to for the risk prevention.In this paper,a new deep-water gas field found in the South China Sea is taken as a reference of project background to investigate the compati bility between scale inhibitors and hydrate inhibitors experimentally.Firstly a preliminary qualification evaluation of scale inhibitors was caried out,in which the static scale inhibition eficiency,the scale induction time,and the minimum effective concentrations of the selected scale inhibitors were tested.Then the effect of commonly used thermodynamic hydrate inhibitor MEG(Mono Ethylene Glycol)on the anti-scaling performance of scale inhibitors was evaluated.MEG-resisted scale inhibitors were further optimized.Finally,an extended discussion on the compati-bility of scale inhibition with hydrate inhibition was conducted.The experimental results showed that the scale inhi bitors HPMA and MA/AA were recommended with the best working concentration of 30 ppm.The high concentration inhibitors(30 wt%)can coexist with the same volume of pure MEG for more than 12-14 h at room condition and 60°C without any precipitation.The anti-scale fficiency of inhibitor with 30 ppm concentration is still up to 90%even at the presence of 20wt%MEG(after2-4 h at 95°C).Hence,in deep-water wellbore,compatible scale and hydrate inhi bitors can be injected together using one chemical pipeline.Besides,it is also found that the polymer scale inhibitors generally have good compatibility with MEG.It deserves further studies and can be regarded as one direction for scale inhibitor improvement in the future.展开更多
Data envelopment analysis has been successfully used in resource allocation problems.However,to the best of our knowledge,there are no allocation models proposed in the literature that simultaneously take both the glo...Data envelopment analysis has been successfully used in resource allocation problems.However,to the best of our knowledge,there are no allocation models proposed in the literature that simultaneously take both the global efficiency and growing potential into account.Hence,this research aims at developing an allocation model for extra input resources,which maximizes the global technical efficiency and scale efficiency of a decision-making unit(DMU)set while maintaining the pure technical efficiency(i.e.,growing potential)of each DMU.To this purpose,we first discuss the optimal resources required by each DMU.We prove that the optimal inputs for the DMU are actually the inputs of some most productive scale size(MPSS).We then propose the allocation model based on the discussion on the case of one DMU.The allocation model is illustrated using two numerical examples.展开更多
基金Supported by Science and Technology Project of Guiyang Company of Guizhou Provincial Tobacco Company"Study on Cultivation of New Type Tobacco Operation Entities in Guiyang Tobacco Area"(2022-06)Students’Platform for Innovation and Entrepreneurship Training Program of Colleges and Universities in Henan Province"Study on Cultivation of New Professional Tobacco Farmers with Family Farms as the Carrier"(202210466045)。
文摘The larger the difference between the willingness scale of tobacco family farmers and the optimal scale of efficiency,the greater the degree of irrationality,and the higher the decision making risk.With the aid of DEA model,this study calculated the optimal scale of efficiency of Guiyang tobacco family farms.Using the ratio of willingness scale and efficiency optimal scale,it measured the degree of irrationality of family farmers.In addition,with the help of multiple linear regression model,it explained the irrational decision making mechanism of family farmers.Finally,it made a portrait of farmers who tend to make irrational decisions,to find specific farmers and guide them in their production and operation,reduce the risk of planting scale decision making and stabilize the sustainable development of the tobacco industry.
基金Supported by Consulting Project of Chinese Academy of Engineering in 2015(2015-XY-22)
文摘Scale management remains the core position in entire development process of the economics and is a major issue of academic research and government concern. Focusing on related problems of agricultural scale management,this paper explored 4 aspects of past literature.( i) It defined the agricultural scale management based on economies of scale theory and changes in returns to scale.( ii) From the perspective of the returns to scale of grain production,there are changes in returns to scale of China's grain production,but the measured changes are not significant.( iii) Existing analysis on factors influencing agricultural scale management mainly includes factors influencing farmers' willingness of scale management and restrictive factors of implementation of scale management.( iv) In studies of the relationship between land management scale and production efficiency,many scholars made qualitative and quantitative analysis on land scale efficiency on the basis of economic indicators they defined,but they reached different conclusions. Finally,it summarized literature and pointed out several issues needing special attention in this field.
基金Project(70921001)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0799)supported by Program for New Century Excellent Talents in University,ChinaProjects(11YJA790158)supported by Humanities and Social Sciences Planning Fund by Chinese Ministry of Education
文摘Since 2009, Chinese nonferrous metals industry has been carried out industry consolidation with strong support by the central government. This work examined technical efficiency of Chinese nonferrous metals firms and its change during the period of 2007 and 2011. Based on financial data from nonferrous metals listed companies, technical efficiency of nonferrous metal minerals mining firms and nonferrous metal smelting, pressing and processing firms was estimated respectively using the data envelopment analysis (DEA) method. It was found that, in both sectors, number of pure technical and scale inefficient firms dominated over efficient ones. Overall, their technical and scale efficiency tended to be very low after 2009. In particular, efficiency scores of nonferrous metal smelting, pressing and processing firms fluctuated greatly during the research period. And a limited number of large leading firms were able to maintain 100% efficiency score in the industry, while efficiency of most of other leading firms has declined since 2009.
基金financial support from the National Social Science Foundation of China(14BGL094)the Rice Research System in Guangdong Province,China(2019KJ105)+2 种基金the EU Project H2020 Program(822730)supported by the United States Department of Agriculture(USDA)National Institute of Food and Agriculture(NIFA)funded Hatch projects(#94382 and#94483)。
文摘Agricultural mechanization and custom machine services have developed rapidly in China,which can influence rice production efficiency in the future.We calculate technical efficiency,allocative efficiency,and scale efficiency using data collected in 2015 from a face-to-face interview survey of 450 households that cultivated 3096 plots located in the five major rice-producing provinces of China.We use a one-step stochastic frontier model to calculate technical efficiency and regress the efficiency scores on socio-demographic and physical land characteristics to find the influencing variables.Variables influencing technical efficiency are compared at three different phases of rice cultivation.We also calculate technical efficiency by using the Heckman Selection Model,which addresses technological heterogeneity and self-selection bias.Results indicate that:(1)the average value of technical efficiency using a one-step stochastic frontier model was found to be 0.74.When self-selection bias is accounted for using the Heckman Selection Model,the average value of the technical efficiency increases to 0.80;(2)mechanization at the chemical application phase has a positive effect on technical efficiency,but mechanization does not affect efficiency at the plowing and harvesting phases;(3)machines are overused relative to both land and labor,and high machine input use on the small size of landholding has resulted in allocative inefficiency;(4)rice farmers are overwhelmingly operating at a sub-optimal scale.Future policies should focus on encouraging farmland transfer in rural areas to achieve scale efficiency and allocative efficiency while promoting mechanization at the chemical application phase of rice cultivation to improve technical efficiency.
文摘Two-oriented agriculture was a complex organism coupling production,economics,society and ecology.Its development process was affected by various factors such as producers,nature,society,etc.In order to overcome measurement error of traditional data envelopment analysis caused by ignoring random,three-stage DEA model was studied to remove environmental factors and random effects.On the foundation of this model was two-oriented agriculture comprehensive production efficiency of 14 cities were estimated in Hunan Province in 2008,and brown forth corresponding policy proposals to promote agricultural development.
文摘Using the DEA analysis method,on the basis of the national panel data from 2002 to 2014,this paper made a comparative analysis on the rice production performance before and after the implementation of direct grain subsidy policy,and made an empirical analysis on the relationship between the direct grain subsidy policy and the changes in the rice production performance. The results showed that the effect of the direct grain subsidy policy on promoting the rice production performance is declining year by year,largely because drop of scale efficiency. Besides,there are problems of serious redundancy in agricultural subsidy,unreasonable resource allocation,leading to low performance and resource waste of rice production.
基金Supported by Zhejiang Philosophy and Social Science (No.08CGJJ001Z)
文摘Making use of the DEA-based method of quadruplicate decomposition of labor productivity, the paper analyzes the influence of labor productivity of provincial textile industry in China, caused by the effect of technical efficiency, pure technical progress, changes of scale efficiency of capital per labor and of capital intensity from the year of 2002 to 2005. Its results show that the improvement of provincial textile industry labor productivity has mainly resulted from technical progress since 2003. Meanwhile, labor productivity of underdeveloped provinces has been growing faster than that of developed ones owing to technology diffusion. And then, the above-mentioned improvement has originated from the enhancement of capital deepening and technology efficiency. In addition, scale return of capital per labor appeared to decrease during the period from 2004 to 2005.
基金National Natural Science Foundation of China(41571095)
文摘Small-scale household agricultural production has been in conflict with China's agricultural modernization.In the context of vigorously promoting rural land circulation and moderate scale management nationwide,research on the relationship between farm size and scale efficiency has become increasingly important.In this paper,we use the "DEA-OLS" two stage method to analyze data from 368 surveys of rice farming households in the Jianghan Plain.The scale efficiency of rice farming was calculated,and the relationship between farm size and scale efficiency investigated.The results indicate that(1) the rice farm size is generally small in Jianghan Plain,with an average of 0.77 ha.The average scale efficiency is 0.88,and it is the main factor limiting an increase in comprehensive technical efficiency.Moreover,88.32% of households are in the stage of increasing returns to scale.(2) There is a stable inverted "U" type relationship between rice farm size and scale efficiency.Considering characteristics of the householder,the household and land quality,the maximum scale efficiency corresponds to a household with 5 ha of rice farm.(3) Among householder characteristics,age has a significant negative influence on scale efficiency,and scale efficiency is lower for a household whose householder is engaged in non-farm work than for one whose householder is devoted to farming.As for land quality,there was a significant positive effect of irrigation on scale efficiency.Among family characteristics,the application of a machine during the seeding process increased scale efficiency by 3.07%.Therefore,we suggest that local government should actively promote rural land circulation,implement a staged-scale management subsidy,and other forms of support for the purchase of agricultural machinery and technical popularization.Increased investment in irrigation improvements and mechanical facilities and encouragement of farmers to enlarge their farm size could improve scale efficiency and farming profit and lead to the development of moderate scale management.
基金The research was supported by grants from the National Natural Science Foundation of China(71622014,41771564 and 71774165)the Humanities and Social Science Fund of the Ministry of Education(14JJD790033 and K16YJA790049)We hereby express our thanks to the anonymous reviewers for their valuable suggestions.
文摘A comparison of the facts at the micro-and macro-level indicates that although some Chinese enterprises are at the international frontier in terms of micro-level energy efficiency,overall energy efficiency at the industrial and national level is seriously lagging behind.Hypotheses based on a market segmentation framework indicate that this is because market segmentation inhibits energy efficiency through its effect on technical efficiency,scale efficiency and allocation efficiency.This effect has been demonstrated by empirical research based on Chinese provincial panel data.
基金supported by the Major Bidding Projects in Shandong Province (No. SDZS-2012-SHBT01)
文摘Precipitation of calcium carbonate (CaCOs) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one (scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca^2+ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80℃ at pH 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCOs changed from calcite to aragonite.
基金Financial support from the National Natural Science Foundation of China (No.50773063)National Basic Research Program of China(2010CB635111)Basic Research of National Defence are highly appreciated
文摘Molecular simulation was performed to study the interaction between CaCO3 crystal and several oligomer inhibitors, by using the equilibrium morphology method to calculate the growth morphology of CaCO3 without inhibitors. The calculated morphology agreed well with SEM photographs. Then, a double-layer model was built to investigate the interaction between calcite crystal and oligomer inhibitors containing maleic anhydride (MA) and acrylic acid (AA). Interaction energy per gram of an oligomer inhibitor was introduced as a scale of inhibition efficiency of different monomers. The results indicated that, for calcite scale inhibition, acrylamide (AM) and vinyl phosphonic acid (VPA) were the most efficient monomers, while allylsulfonic acid (AS) was the poorest. Increasing proportion of AM in dimer inhibitor molecule would improve the inhibition efficiency of MA, though, for a trimer, such as MA-AA-AM, certain sequence of monomers in the inhibitor molecule was necessary besides higher proportion of AM.
文摘China has five layers of government including the central government.Recently,some prefectural governments meet fiscal distress.We investigate the effects of urban and rural populations and area sizes on the expenditures of the prefecture-level local government by estimating quintile regression.At around 220,000 people,per capita local government expenditure for urban populations is minimized in our simulation.The expenditure for rural populations is proportional to the population size.The expenditure in accordance with the areas is also proportional to the area size.The cost structure is the reason why China’s recent rapid urbanization increases prefectural government’s fiscal distress.
基金This workwas supported by R&D and Application Demonstration of Common Key Technologies in Modern Service Industry,Key Special Sub Topics of National Key R&D Plan(Grant No.2018YFB1402500).
文摘Promoting the growth of the lithium battery sector has been a critical aspect of China's energy policy in terms of achieving carbon neutrality.However,despite significant support on research and development(R&D)investments that have resulted in increasing size,the sector seems to be falling behind in technological areas.To guide future policies and understand proper ways of promoting R&D efficiency,we looked into the lithium battery industry of China.Specifically,data envelopment analysis(DEA)was used as the primary approach based on evidence from 22 listed lithium battery enterprises.The performance of the five leading players was compared with that of the industry as a whole.Results revealed little indication of a meaningful improvement in R&D efficiency throughout our sample from 2010 to 2019.However,during this period,a significant increase in R&D expenditure was witnessed.This finding was supported,as the results showed that the average technical efficiency of the 22 enterprises was 0.442,whereas the average pure technical efficiency was at 0.503,thus suggesting that they were suffering from decreasing returns to scale(DRS).In contrast,the performance of the five leading players seemed superior because their average efficiency scores were higher than the industry's average.Moreover,they were experiencing increasing scale efficiency(IRS).We draw on these findings to suggest to policymakers that supporting technologically intensive sectors should be more than simply increasing investment scale;rather,it should also encompass assisting businesses in developing efficient managerial processes for R&D.
基金the Zhanjiang Branch company,CNOOC,and partially financed by the Fundamental Research Funds for the Central Universities(No.18CX05009A)the National Major S&T Project(No.2016ZX05056004-003)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT 14R58).
文摘When both of the scaling and hydrate risks occur in deep water wells or subsea pipelines at the same time,the compatibility between scale and hydrate inhibitors should be paid more attention to for the risk prevention.In this paper,a new deep-water gas field found in the South China Sea is taken as a reference of project background to investigate the compati bility between scale inhibitors and hydrate inhibitors experimentally.Firstly a preliminary qualification evaluation of scale inhibitors was caried out,in which the static scale inhibition eficiency,the scale induction time,and the minimum effective concentrations of the selected scale inhibitors were tested.Then the effect of commonly used thermodynamic hydrate inhibitor MEG(Mono Ethylene Glycol)on the anti-scaling performance of scale inhibitors was evaluated.MEG-resisted scale inhibitors were further optimized.Finally,an extended discussion on the compati-bility of scale inhibition with hydrate inhibition was conducted.The experimental results showed that the scale inhi bitors HPMA and MA/AA were recommended with the best working concentration of 30 ppm.The high concentration inhibitors(30 wt%)can coexist with the same volume of pure MEG for more than 12-14 h at room condition and 60°C without any precipitation.The anti-scale fficiency of inhibitor with 30 ppm concentration is still up to 90%even at the presence of 20wt%MEG(after2-4 h at 95°C).Hence,in deep-water wellbore,compatible scale and hydrate inhi bitors can be injected together using one chemical pipeline.Besides,it is also found that the polymer scale inhibitors generally have good compatibility with MEG.It deserves further studies and can be regarded as one direction for scale inhibitor improvement in the future.
文摘Data envelopment analysis has been successfully used in resource allocation problems.However,to the best of our knowledge,there are no allocation models proposed in the literature that simultaneously take both the global efficiency and growing potential into account.Hence,this research aims at developing an allocation model for extra input resources,which maximizes the global technical efficiency and scale efficiency of a decision-making unit(DMU)set while maintaining the pure technical efficiency(i.e.,growing potential)of each DMU.To this purpose,we first discuss the optimal resources required by each DMU.We prove that the optimal inputs for the DMU are actually the inputs of some most productive scale size(MPSS).We then propose the allocation model based on the discussion on the case of one DMU.The allocation model is illustrated using two numerical examples.