The purpose of this paper is to identify the critical road sections and intersections in a road network which have great influence on the normal transport functions of the road network and to optimize the road network...The purpose of this paper is to identify the critical road sections and intersections in a road network which have great influence on the normal transport functions of the road network and to optimize the road network structure by reducing its vulnerability. In this paper, the framework of road network structural vulnerability measurement and improvement model is proposed. The network efficiency model is used to define road network structural vulnerability. Shanghai freeway network is analyzed based on this model. We find that using this model the critical components of the road network can be identified. Two methods which are increasing connections and rewiring are proposed to optimize the road network structural vulnerability and the results can be used to reduce the network vulnerability. The measurement method that we put forward for structure vulnerability is useful and important to optimize road network structure.展开更多
In the analysis of correlated data, it is ideal to capture the true dependence structure to increase effciency of the estimation. However, for multivariate survival data, this is extremely
Recurrent event time data are common in biomedical follow-up studies, in which a study subject may experience repeated occurrences of an event of interest. In this paper, we evaluate two popular nonparametric tests fo...Recurrent event time data are common in biomedical follow-up studies, in which a study subject may experience repeated occurrences of an event of interest. In this paper, we evaluate two popular nonparametric tests for recurrent event time data in terms of their relative effciency. One is the log-rank test for classical survival data and the other a more recently developed nonparametric test based on comparing mean recurrent rates. We show analytically that, somewhat surprisingly, the log-rank test that only makes use of time to the first occurrence could be more effcient than the test for mean occurrence rates that makes use of all available recurrence times, provided that subject-to-subject variation of recurrence times is large. Explicit formula are derived for asymptotic relative effciencies under the frailty model. The findings are demonstrated via extensive simulations.展开更多
The survival analysis literature has always lagged behind the categorical data literature in developing methods to analyze clustered or multivariate data. While estimators based on
We thank all the discussants for their interesting and stimulating contributions. They have touched various aspects that have not been considered by the original articles.
This review reports several key advances on the theoretical investigations of efficiency at maximum power of heat engines in the past five years. The analytical results of efficiency at maximum power for the Curzon-Ah...This review reports several key advances on the theoretical investigations of efficiency at maximum power of heat engines in the past five years. The analytical results of efficiency at maximum power for the Curzon-Ahlborn heat engine, the stochastic heat engine constructed from a Brownian particle, and Feynman＇s ratchet as a heat engine are presented. It is found that： the efficiency at maximum power exhibits universal behavior at small relative temperature differences; the lower and the upper bounds might exist under quite general conditions; and the problem of efficiency at maximum power comes down to seeking for the minimum irreversible entropy production in each finite-time isothermal process for a given time.展开更多
Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries(SIBs).However,their practical applicatio...Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries(SIBs).However,their practical applications are greatly restricted by the poor cycling performances and complicated synthesis methods.In this work,a sandwich-like Sn Se2/reduced graphene oxide(r GO)composite with a small amount of r GO(7.3%)is synthesized by a simple one-pot solvothermal technique.The as-synthesized Sn Se2/r GO shows improved initial coulombic efficiency(ICE)of 73.7%,high capacity of 402.0 m Ah g-1 after 150 cycles at 0.1 A g-1 with a retention of 86.2%and outstanding rate performances.The abundant Sn-O-C bonds of synthesized material not only accelerate the charge transfer at the interface but also enhance the mechanical strength to accommodate volume variation and prevent active material loss during cycling.Moreover,the compact structure leads to thin solid electrolyte interface(SEI)so that high initial coulombic efficiency was obtained.Furthermore,full cells are assembled to test its potential application.This work offers a simple method to synthesize Sn Se2/r GO as a candidate anode for SIBs.展开更多
Under the assumption that the ordering cone has a nonempty interior and is separable （or the feasible set has a nonempty interior and is separable）, we give scalarization theorems on Benson proper effciency. Applyin...Under the assumption that the ordering cone has a nonempty interior and is separable （or the feasible set has a nonempty interior and is separable）, we give scalarization theorems on Benson proper effciency. Applying the results to vector optimization problems with nearly cone-subconvexlike set-valued maps, we obtain scalarization theorems and Lagrange multiplier theorems for Benson proper effcient solutions.展开更多
Although total factor productivity(TFP)is a common concept in mainstream Western economics,its origins are actually embedded in Marx's understanding of improving labor productivity.As an important element of labor...Although total factor productivity(TFP)is a common concept in mainstream Western economics,its origins are actually embedded in Marx's understanding of improving labor productivity.As an important element of labor productivity under socialized production conditions,TFP is further reflected in the category of"socially necessary labor time"in two distinct senses.Re-examining TFP from the perspective of Marxist political economy and incorporating it into the theoretical system of political economy of socialism with Chinese characteristics vividly illustrates the essence of"adhering to original principles,assimilating foreign concepts,and embracing a forward-looking vision"within political economy of socialism with Chinese characteristics.In practice,it is necessary to start with Marx's theory of productive labor and delineate the sectors involved in productive labor so that TFP and its fluctuations can be measured in a more relevant way.In the context of the new era and the new journey,as the key to achieving high-quality economic development in China,efforts are needed to increase TFP.This requires balancing economic factors such as the long term and short term,supply and demand,and gross quantity and structure,and promoting transformative changes in the quality,efficiency,and dynamism of economic development.展开更多
Efficient and intuitive representation of floods can improve people's perception,which is useful for flood emergency management_and decision making.However,the current methods of visualizing flood disaster scenes ...Efficient and intuitive representation of floods can improve people's perception,which is useful for flood emergency management_and decision making.However,the current methods of visualizing flood disaster scenes have the shortcomings of data redundancy and low-efficiency.The interference of the complex background can be avoided through region of interest(ROl)extraction,because the attention will be quickly attracted by a few salient visual objects.First,the characteristics of the flood disaster scene object are analysed,and the method for scene division and data organization is established.Second,the region of interest is extracted according to the time series data of the flood evolution process simulated using cellular automata,and the dynamic identification model of the objects of interest is established.Then,a dynamic scheduling queue model with service interruption is designed to optimize the rendering efficiency of flood scenes and improve the perception efficiency.Finally,a prototype visualization system was developed and the experimental results show that approximately 30%of the redundant data are reduced,and the scene rendering efficiency is increased by approximately 15%.The non-ROl visualization is weakened by using the rules of human visual cognition,which improves the perception efficiency of flood scenes.展开更多
In randomized clinical trials with right-censored time-to-event outcomes,the popular log-rank test without adjusting for baseline covariates is asymptotically valid for treatment effect under simple randomization of t...In randomized clinical trials with right-censored time-to-event outcomes,the popular log-rank test without adjusting for baseline covariates is asymptotically valid for treatment effect under simple randomization of treatments but is too conservative under covariate-adaptive random-ization.The stratified log-rank test,which adjusts baseline covariates in the test procedure by stratification,is asymptotically valid regardless of what treatment randomization is applied.In the literature,however,under simple randomization there is no affirmative conclusion about whether the stratified log-rank test is asymptotically more powerful than the unstratified log-rank test.In this article we show when the stratified and unstratified log-rank tests aim for the same null hypothesis and that,under simple randomization,the stratified log-rank test is asymp-totically more powerful than the unstratified log-rank test in the region of alternative hypothesis that is specified by a Cox proportional hazards model.We also provide some discussion about why we do not have an affirmative conclusion in general.展开更多
Bioremediation is a process mediated by microorganisms and represents a sustainable and eco-friendly way to degrade and detoxify environmental contaminants. Soil microbiomes clearly become a key component of bioremedi...Bioremediation is a process mediated by microorganisms and represents a sustainable and eco-friendly way to degrade and detoxify environmental contaminants. Soil microbiomes clearly become a key component of bioremediation as they are more stable and effcient than pure cultures, being recognized as one of the scientific frontiers of the soil environmental science and technology fields. Recently,many advancements have been made regarding the investigation of remediation mechanisms by soil microbiomes and the interactions inside them. This has greatly expanded our ability to characterize the remediating function of soil microbiomes and identify the factors that influence their effciency for remediation. Here, we suggest that soil microbiomes are a promising strategy for soil remediation.Research is now needed to identify how we can manipulate and manage soil microbiomes to improve remediation effciency and increase soil fertility at the same time. Therefore, this review aims to emphasize the importance of soil microbiomes in bioremediation and promote further development of this strategy into a widely accepted technique.展开更多
Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use effciency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems cau...Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use effciency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems caused by nutrient leaching. This study investigated soil properties and cowpea yield responses to biochars(BCs) made from different feedstocks, baby corn peel biochar(BC1), branches of mango tree biochar(BC2), and rice husk biochar(BC3), applied in combination with nitrogen-phosphorus-potassium(NPK) fertilizers.The experiment was conducted in a greenhouse, using an acid sandy soil(Arenosol) that was submitted for 70 d to the following eight treatments: i) control;ii) full dose of NPK(a commercial compound fertilizer(12-24-12 of N-P2O5-K2O)+ urea(46% N));iii) BC1+ half dose of NPK;iv) BC1 + full dose of NPK;v) BC2 + half dose of NPK;vi) BC2 + full dose of NPK;vii) BC3 + half dose of NPK;and viii) BC3 + full dose of NPK. All biochars were applied at a rate of 0.9%(weight/weight), and each type of biochar was combined with half and full doses of NPK fertilizers. Soil pH increased significantly(P < 0.05) in treatments with BC1 and BC2,while cation exchange capacity(CEC) and available P were higher in the treatments with BC1;BC1 and BC2 also induced higher activity of enzymes related to the P cycle and higher cowpea yield. Similar soil properties and cowpea yield parameters were obtained with the full and half doses of NPK fertilizers for each type of biochar used. In conclusion, biochars in the combination with NPK fertilizers improved soil chemistry and enzymatic activities, allowing reduced fertilizer application and food production costs in the acid soil studied.展开更多
The best breakdown point robustness is one of the most outstanding features of the univariate median.For this robustness property,the median,however,has to pay the price of a low effciency at normal and other light-ta...The best breakdown point robustness is one of the most outstanding features of the univariate median.For this robustness property,the median,however,has to pay the price of a low effciency at normal and other light-tailed models.Affine equivariant multivariate analogues of the univariate median with high breakdown points were constructed in the past two decades.For the high breakdown robustness,most of them also have to sacrifice their effciency at normal and other models,nevertheless.The affine equivariant maximum depth estimator proposed and studied in this paper turns out to be an exception.Like the univariate median,it also possesses a highest breakdown point among all its multivariate competitors.Unlike the univariate median,it is also highly efficient relative to the sample mean at normal and various other distributions,overcoming the vital low-effciency shortcoming of the univariate and other multivariate generalized medians.The paper also studies the asymptotics of the estimator and establishes its limit distribution without symmetry and other strong assumptions that are typically imposed on the underlying distribution.展开更多
The energy balance, air internal energy, enthalpy and exergy transfers of high pressure switching expansion reduction （SER） are comparatively analyzed in this paper to give a better understanding about the exergy an...The energy balance, air internal energy, enthalpy and exergy transfers of high pressure switching expansion reduction （SER） are comparatively analyzed in this paper to give a better understanding about the exergy analysis and its difference between energy conversion analyses for the pneumatics. In SER, the exergy transfer efficiency is much lower than the enthalpy efficiency. The enthalpy efficiency is primarily related to the initial pressure of supply tanks, and the exergy efficiency is primarily related to the pressure reduction ratios. Heat transfers increase the internal energy, enthalpy and exergy of air; the influence on exergy is relatively small. The total enthalpy in SER decreases as the air temperature decreases in the expansion process of the air. And exergy loss is primarily related to the irreversible process of isenthalpic throttling but not energy conversion. Based on the analyses, to improve the exergy efficiency of the pneumatics, the pressure reduction without power output should be avoided.展开更多
Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam...Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.展开更多
Carbon emission is inevitable,and changes with energy consumption and economic development,presents policy options toward sustainable development path.Currently,there is little assurance from policymakers in committin...Carbon emission is inevitable,and changes with energy consumption and economic development,presents policy options toward sustainable development path.Currently,there is little assurance from policymakers in committing to climate change pledges:taking the Middle-East and North African(MENA)region as a specific case with using 2019 as a cut-off period.We conducted an interim assessment of the Paris Agreement to ascertain whether climate actions are in tandem with emissions reduction targets.Making use of difference-in-difference technique as a quasiexperiment supported by fixed-effects and placebo treatment models,the results point to evidence of less than 1%effective CO_(2) emissions reduction as of 2019 compared to the 2015 level.The current carbon emissions reduction commitment level is far-reaching contrary to the Nationally Determined Contributions(NDCs)pledged(16.43%on average by 2030 compared to the 2015 level).The analysis suggests that achieving NDCs commitments are currently major burden on policymakers since the economic development is highly linked with nonrenewable energy consumption.Furthermore,a more comprehensive framework when accounting for all available renewable and clean energy projects shows reduction levels in the range of 30%-40%from 2020 to 2030.These results suggest that the Paris Agreement in MENA countries may be more effective from 2020,thus underscore the importance of capturing ongoing projects(involving renewable and clean energy technologies)into interim policy assessment.The shared implication is that greater efforts are demanded from the region and at country levels to further decrease emissions through the use of negative emissions technologies particularly in the electricity generation sector.展开更多
基金the National High Technology Research and Development Program (863) of China (No. 2006AA11Z209)
文摘The purpose of this paper is to identify the critical road sections and intersections in a road network which have great influence on the normal transport functions of the road network and to optimize the road network structure by reducing its vulnerability. In this paper, the framework of road network structural vulnerability measurement and improvement model is proposed. The network efficiency model is used to define road network structural vulnerability. Shanghai freeway network is analyzed based on this model. We find that using this model the critical components of the road network can be identified. Two methods which are increasing connections and rewiring are proposed to optimize the road network structural vulnerability and the results can be used to reduce the network vulnerability. The measurement method that we put forward for structure vulnerability is useful and important to optimize road network structure.
文摘In the analysis of correlated data, it is ideal to capture the true dependence structure to increase effciency of the estimation. However, for multivariate survival data, this is extremely
基金supported by US National Science Foundation (Grant No. DMS-0504269)
文摘Recurrent event time data are common in biomedical follow-up studies, in which a study subject may experience repeated occurrences of an event of interest. In this paper, we evaluate two popular nonparametric tests for recurrent event time data in terms of their relative effciency. One is the log-rank test for classical survival data and the other a more recently developed nonparametric test based on comparing mean recurrent rates. We show analytically that, somewhat surprisingly, the log-rank test that only makes use of time to the first occurrence could be more effcient than the test for mean occurrence rates that makes use of all available recurrence times, provided that subject-to-subject variation of recurrence times is large. Explicit formula are derived for asymptotic relative effciencies under the frailty model. The findings are demonstrated via extensive simulations.
文摘The survival analysis literature has always lagged behind the categorical data literature in developing methods to analyze clustered or multivariate data. While estimators based on
文摘We thank all the discussants for their interesting and stimulating contributions. They have touched various aspects that have not been considered by the original articles.
基金supported by the National Natural Science Foundation of China (Grant No.11075015)the Fundamental Research Funds for the Central Universities
文摘This review reports several key advances on the theoretical investigations of efficiency at maximum power of heat engines in the past five years. The analytical results of efficiency at maximum power for the Curzon-Ahlborn heat engine, the stochastic heat engine constructed from a Brownian particle, and Feynman＇s ratchet as a heat engine are presented. It is found that： the efficiency at maximum power exhibits universal behavior at small relative temperature differences; the lower and the upper bounds might exist under quite general conditions; and the problem of efficiency at maximum power comes down to seeking for the minimum irreversible entropy production in each finite-time isothermal process for a given time.
基金supported by the National Natural Science Foundation of China(Nos.21771164,U1804129,21773215)。
文摘Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries(SIBs).However,their practical applications are greatly restricted by the poor cycling performances and complicated synthesis methods.In this work,a sandwich-like Sn Se2/reduced graphene oxide(r GO)composite with a small amount of r GO(7.3%)is synthesized by a simple one-pot solvothermal technique.The as-synthesized Sn Se2/r GO shows improved initial coulombic efficiency(ICE)of 73.7%,high capacity of 402.0 m Ah g-1 after 150 cycles at 0.1 A g-1 with a retention of 86.2%and outstanding rate performances.The abundant Sn-O-C bonds of synthesized material not only accelerate the charge transfer at the interface but also enhance the mechanical strength to accommodate volume variation and prevent active material loss during cycling.Moreover,the compact structure leads to thin solid electrolyte interface(SEI)so that high initial coulombic efficiency was obtained.Furthermore,full cells are assembled to test its potential application.This work offers a simple method to synthesize Sn Se2/r GO as a candidate anode for SIBs.
基金Supported by the National Natural Science Foundation of China (10571035,10871141)
文摘Under the assumption that the ordering cone has a nonempty interior and is separable （or the feasible set has a nonempty interior and is separable）, we give scalarization theorems on Benson proper effciency. Applying the results to vector optimization problems with nearly cone-subconvexlike set-valued maps, we obtain scalarization theorems and Lagrange multiplier theorems for Benson proper effcient solutions.
文摘Although total factor productivity(TFP)is a common concept in mainstream Western economics,its origins are actually embedded in Marx's understanding of improving labor productivity.As an important element of labor productivity under socialized production conditions,TFP is further reflected in the category of"socially necessary labor time"in two distinct senses.Re-examining TFP from the perspective of Marxist political economy and incorporating it into the theoretical system of political economy of socialism with Chinese characteristics vividly illustrates the essence of"adhering to original principles,assimilating foreign concepts,and embracing a forward-looking vision"within political economy of socialism with Chinese characteristics.In practice,it is necessary to start with Marx's theory of productive labor and delineate the sectors involved in productive labor so that TFP and its fluctuations can be measured in a more relevant way.In the context of the new era and the new journey,as the key to achieving high-quality economic development in China,efforts are needed to increase TFP.This requires balancing economic factors such as the long term and short term,supply and demand,and gross quantity and structure,and promoting transformative changes in the quality,efficiency,and dynamism of economic development.
基金funded by National Natural Science Foundation of China[grant number U2034202,42271424 and 41871289].
文摘Efficient and intuitive representation of floods can improve people's perception,which is useful for flood emergency management_and decision making.However,the current methods of visualizing flood disaster scenes have the shortcomings of data redundancy and low-efficiency.The interference of the complex background can be avoided through region of interest(ROl)extraction,because the attention will be quickly attracted by a few salient visual objects.First,the characteristics of the flood disaster scene object are analysed,and the method for scene division and data organization is established.Second,the region of interest is extracted according to the time series data of the flood evolution process simulated using cellular automata,and the dynamic identification model of the objects of interest is established.Then,a dynamic scheduling queue model with service interruption is designed to optimize the rendering efficiency of flood scenes and improve the perception efficiency.Finally,a prototype visualization system was developed and the experimental results show that approximately 30%of the redundant data are reduced,and the scene rendering efficiency is increased by approximately 15%.The non-ROl visualization is weakened by using the rules of human visual cognition,which improves the perception efficiency of flood scenes.
文摘In randomized clinical trials with right-censored time-to-event outcomes,the popular log-rank test without adjusting for baseline covariates is asymptotically valid for treatment effect under simple randomization of treatments but is too conservative under covariate-adaptive random-ization.The stratified log-rank test,which adjusts baseline covariates in the test procedure by stratification,is asymptotically valid regardless of what treatment randomization is applied.In the literature,however,under simple randomization there is no affirmative conclusion about whether the stratified log-rank test is asymptotically more powerful than the unstratified log-rank test.In this article we show when the stratified and unstratified log-rank tests aim for the same null hypothesis and that,under simple randomization,the stratified log-rank test is asymp-totically more powerful than the unstratified log-rank test in the region of alternative hypothesis that is specified by a Cox proportional hazards model.We also provide some discussion about why we do not have an affirmative conclusion in general.
基金supported by the National Natural Science Foundation of China (No.41671327)the Outstanding Youth Fund of Jiangsu Province, China (No.BK20150049)
文摘Bioremediation is a process mediated by microorganisms and represents a sustainable and eco-friendly way to degrade and detoxify environmental contaminants. Soil microbiomes clearly become a key component of bioremediation as they are more stable and effcient than pure cultures, being recognized as one of the scientific frontiers of the soil environmental science and technology fields. Recently,many advancements have been made regarding the investigation of remediation mechanisms by soil microbiomes and the interactions inside them. This has greatly expanded our ability to characterize the remediating function of soil microbiomes and identify the factors that influence their effciency for remediation. Here, we suggest that soil microbiomes are a promising strategy for soil remediation.Research is now needed to identify how we can manipulate and manage soil microbiomes to improve remediation effciency and increase soil fertility at the same time. Therefore, this review aims to emphasize the importance of soil microbiomes in bioremediation and promote further development of this strategy into a widely accepted technique.
基金“Applied Research and Multi-sectorial Program (FIAM) (No.5.2.1)” granted by the Italian Cooperation and Development Agency (ICDA) to the Universidade Eduardo Mondlane
文摘Fertilization is required for optimum plant growth, particularly in unfertile soils, while optimizing nutrient use effciency is an alternative to reduce inorganic fertilizer needs and reduce environmental problems caused by nutrient leaching. This study investigated soil properties and cowpea yield responses to biochars(BCs) made from different feedstocks, baby corn peel biochar(BC1), branches of mango tree biochar(BC2), and rice husk biochar(BC3), applied in combination with nitrogen-phosphorus-potassium(NPK) fertilizers.The experiment was conducted in a greenhouse, using an acid sandy soil(Arenosol) that was submitted for 70 d to the following eight treatments: i) control;ii) full dose of NPK(a commercial compound fertilizer(12-24-12 of N-P2O5-K2O)+ urea(46% N));iii) BC1+ half dose of NPK;iv) BC1 + full dose of NPK;v) BC2 + half dose of NPK;vi) BC2 + full dose of NPK;vii) BC3 + half dose of NPK;and viii) BC3 + full dose of NPK. All biochars were applied at a rate of 0.9%(weight/weight), and each type of biochar was combined with half and full doses of NPK fertilizers. Soil pH increased significantly(P < 0.05) in treatments with BC1 and BC2,while cation exchange capacity(CEC) and available P were higher in the treatments with BC1;BC1 and BC2 also induced higher activity of enzymes related to the P cycle and higher cowpea yield. Similar soil properties and cowpea yield parameters were obtained with the full and half doses of NPK fertilizers for each type of biochar used. In conclusion, biochars in the combination with NPK fertilizers improved soil chemistry and enzymatic activities, allowing reduced fertilizer application and food production costs in the acid soil studied.
基金supported by Natural Science Foundation of USA (Grant Nos. DMS-0071976, DMS-0234078)the Southwestern University of Finance and Economics Third Period Construction Item Funds of the 211 Project (Grant No. 211D3T06)
文摘The best breakdown point robustness is one of the most outstanding features of the univariate median.For this robustness property,the median,however,has to pay the price of a low effciency at normal and other light-tailed models.Affine equivariant multivariate analogues of the univariate median with high breakdown points were constructed in the past two decades.For the high breakdown robustness,most of them also have to sacrifice their effciency at normal and other models,nevertheless.The affine equivariant maximum depth estimator proposed and studied in this paper turns out to be an exception.Like the univariate median,it also possesses a highest breakdown point among all its multivariate competitors.Unlike the univariate median,it is also highly efficient relative to the sample mean at normal and various other distributions,overcoming the vital low-effciency shortcoming of the univariate and other multivariate generalized medians.The paper also studies the asymptotics of the estimator and establishes its limit distribution without symmetry and other strong assumptions that are typically imposed on the underlying distribution.
基金the National Natural Science Foundation of China(No.50575202)
文摘The energy balance, air internal energy, enthalpy and exergy transfers of high pressure switching expansion reduction （SER） are comparatively analyzed in this paper to give a better understanding about the exergy analysis and its difference between energy conversion analyses for the pneumatics. In SER, the exergy transfer efficiency is much lower than the enthalpy efficiency. The enthalpy efficiency is primarily related to the initial pressure of supply tanks, and the exergy efficiency is primarily related to the pressure reduction ratios. Heat transfers increase the internal energy, enthalpy and exergy of air; the influence on exergy is relatively small. The total enthalpy in SER decreases as the air temperature decreases in the expansion process of the air. And exergy loss is primarily related to the irreversible process of isenthalpic throttling but not energy conversion. Based on the analyses, to improve the exergy efficiency of the pneumatics, the pressure reduction without power output should be avoided.
基金Supported by National Basic Research Program (973 program) of China (2007CB815000, 2005CB724800) National Natural Science Foundation of China (10775003,10475004, 10405001, 10221003, J0730316)
文摘Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.
基金supported by the funding of Belt and Road Research Institute,Xiamen University(No:1500-X2101200)National Natural Science Foundation of China(Key Program,No 72133003).
文摘Carbon emission is inevitable,and changes with energy consumption and economic development,presents policy options toward sustainable development path.Currently,there is little assurance from policymakers in committing to climate change pledges:taking the Middle-East and North African(MENA)region as a specific case with using 2019 as a cut-off period.We conducted an interim assessment of the Paris Agreement to ascertain whether climate actions are in tandem with emissions reduction targets.Making use of difference-in-difference technique as a quasiexperiment supported by fixed-effects and placebo treatment models,the results point to evidence of less than 1%effective CO_(2) emissions reduction as of 2019 compared to the 2015 level.The current carbon emissions reduction commitment level is far-reaching contrary to the Nationally Determined Contributions(NDCs)pledged(16.43%on average by 2030 compared to the 2015 level).The analysis suggests that achieving NDCs commitments are currently major burden on policymakers since the economic development is highly linked with nonrenewable energy consumption.Furthermore,a more comprehensive framework when accounting for all available renewable and clean energy projects shows reduction levels in the range of 30%-40%from 2020 to 2030.These results suggest that the Paris Agreement in MENA countries may be more effective from 2020,thus underscore the importance of capturing ongoing projects(involving renewable and clean energy technologies)into interim policy assessment.The shared implication is that greater efforts are demanded from the region and at country levels to further decrease emissions through the use of negative emissions technologies particularly in the electricity generation sector.
