The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using...The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using） of DSC.The effect of the rate of the depressurization of CO2 on the crystallization of the samples was also examined.It is found that there are three melting peaks on each DSC curve of the samples treated in supericritical CO2 at the temperature above tm of the untreated PVCH-PE-PVCH.They corresponded to the 'hard' confined crystallization of PE blocks homogeneous nucleation,the 'soft' confined crystallization of PE blocks homogeneous nucleation and the self-seeding nucleation free crystallization of PE blocks respectively.Furthermore,these three kinds of crystallization could be controlled by changing the competition between the crystallization of PE block and the vitrifaction of PVCH block in the samples,which depended on the rate of the depressurization of CO2.展开更多
Payments for ecosystem service （PES） schemes have spread all over developing countries in the last 20 years or so. PES schemes often have high opportunity costs in terms of foregone uses of goods and services offere...Payments for ecosystem service （PES） schemes have spread all over developing countries in the last 20 years or so. PES schemes often have high opportunity costs in terms of foregone uses of goods and services offered by the environment. It is within this scope that economic evaluation of environmental goods and services plays a role. In this paper we surveyed articles and studies that report application of economic environmental valuation procedures in PES schemes. Special attention was paid to data collection and analysis, to theoretical robustness of its procedures and to the aggregation of estimated value. We also scrutinize how these estimates had been incorporated into PES schemes, in particularly in the assessment phase of these schemes. Empirical data from Brazil and other Latin American countries were used, particularly those in the Amazon Basis. Our results reveal a frequent overestimation of the values of ecosystem services calculated through the use of economic valuation methods. Values have been estimated by production function methods （opportunity cost, preventive expenditures, recovering cost or dose-response methods）. As a consequence, estimated values reflect much more willingness to accept compensation by supplier and rarely willingness to pay by consumer of these ecosystem services. Besides this distance between supply and demand, application of valuation methods did not account for problems such as uncertainty, risks, and lack of information. All these limitations have led to wrong decision-making.展开更多
This paper introduces a newly developed vacuum Plume effects Experimental System(PES) used for plume effect tests of rocket engines and vacuum heat tests of satellites. The design level, manufacturing technique, and t...This paper introduces a newly developed vacuum Plume effects Experimental System(PES) used for plume effect tests of rocket engines and vacuum heat tests of satellites. The design level, manufacturing technique, and testing capabilities of the PES have reached a highly advanced level at home and abroad. The PES mainly consists of a vacuum chamber, vacuum acquisition system, nitrogen system, helium system, and parameter measurement system. A breakthrough was obtained on the Large Scale Cryo-Pumping System, which was based on a combined liquid nitrogen and liquid helium heat sink. An internal cryopump with a limiting temperature of 4.2 K and an efficient absorption area of 305 m2 was developed. The absorption capability of the cryopump was above 7×107 L/s. Vacuum plume tests were performed in the temperature ranges of ambient temperature, liquid nitrogen, and liquid helium. The experimental results showed that the plume test capability of PES is higher than that of similar foreign equipment STG and CHAFF-4. For 2 g/s and 117 N rocket engines, the dynamic vacuum degree of environment was 8.0×10?4 Pa(approximately 137 km height) and 1.1×10?2 Pa(approximately 106 km height), respectively.展开更多
文摘The melting and recrystallization behaviour of poly（vinylcyclohexane）-b-poly（ethylene）-b-poly（vinylcyclohexane）（PVCH-PE-PVCH） triblock copolymer in supercritical carbon dioxide(CO2) was investigated by（using） of DSC.The effect of the rate of the depressurization of CO2 on the crystallization of the samples was also examined.It is found that there are three melting peaks on each DSC curve of the samples treated in supericritical CO2 at the temperature above tm of the untreated PVCH-PE-PVCH.They corresponded to the 'hard' confined crystallization of PE blocks homogeneous nucleation,the 'soft' confined crystallization of PE blocks homogeneous nucleation and the self-seeding nucleation free crystallization of PE blocks respectively.Furthermore,these three kinds of crystallization could be controlled by changing the competition between the crystallization of PE block and the vitrifaction of PVCH block in the samples,which depended on the rate of the depressurization of CO2.
文摘Payments for ecosystem service （PES） schemes have spread all over developing countries in the last 20 years or so. PES schemes often have high opportunity costs in terms of foregone uses of goods and services offered by the environment. It is within this scope that economic evaluation of environmental goods and services plays a role. In this paper we surveyed articles and studies that report application of economic environmental valuation procedures in PES schemes. Special attention was paid to data collection and analysis, to theoretical robustness of its procedures and to the aggregation of estimated value. We also scrutinize how these estimates had been incorporated into PES schemes, in particularly in the assessment phase of these schemes. Empirical data from Brazil and other Latin American countries were used, particularly those in the Amazon Basis. Our results reveal a frequent overestimation of the values of ecosystem services calculated through the use of economic valuation methods. Values have been estimated by production function methods （opportunity cost, preventive expenditures, recovering cost or dose-response methods）. As a consequence, estimated values reflect much more willingness to accept compensation by supplier and rarely willingness to pay by consumer of these ecosystem services. Besides this distance between supply and demand, application of valuation methods did not account for problems such as uncertainty, risks, and lack of information. All these limitations have led to wrong decision-making.
基金supported by the Space Cooperation Project between Russia and China
文摘This paper introduces a newly developed vacuum Plume effects Experimental System(PES) used for plume effect tests of rocket engines and vacuum heat tests of satellites. The design level, manufacturing technique, and testing capabilities of the PES have reached a highly advanced level at home and abroad. The PES mainly consists of a vacuum chamber, vacuum acquisition system, nitrogen system, helium system, and parameter measurement system. A breakthrough was obtained on the Large Scale Cryo-Pumping System, which was based on a combined liquid nitrogen and liquid helium heat sink. An internal cryopump with a limiting temperature of 4.2 K and an efficient absorption area of 305 m2 was developed. The absorption capability of the cryopump was above 7×107 L/s. Vacuum plume tests were performed in the temperature ranges of ambient temperature, liquid nitrogen, and liquid helium. The experimental results showed that the plume test capability of PES is higher than that of similar foreign equipment STG and CHAFF-4. For 2 g/s and 117 N rocket engines, the dynamic vacuum degree of environment was 8.0×10?4 Pa(approximately 137 km height) and 1.1×10?2 Pa(approximately 106 km height), respectively.
