The Voyage 2050 released by the European Space Agency (ESA) in its science programme for the time frame 2035- 2050 in June 2021 attracts the global attention of all walks of life. This paper presents a comprehensive and in-depth scientific interpretation of the plan, and it is shown that the Voyage 2050 focuses on major scientific frontiers, looks forward to the future technological innovation, and identifies the top three priorities for the future large-class missions, i.e., the moons of the giant Solar System planets, the temperate exoplanets or the galactic ecosystem, and the new physical probes of the early Universe. In the Voyage 2050, 14 candidate themes are listed for the medium and small missions, several recommendations are made for the key payload technology development for more long-term breakthrough scientific returns, and the importance of training the next generation of space science talents is emphasized.

This paper reviews the applications of foreign nuclear ships, discusses the nuclear safety challenges of developing the floating nuclear power plants, as well as the development situation of the key technologies of the equipment production and the shipbuilding, along with some possible solutions.

In the past 20 years, China has made a great progress in the field of the membrane, which plays an important role in the water resources, the new energy, the traditional industrial technology transformation and other related fields. In order to accurately evaluate the service life of the membranes to determine the economical and feasible replacement cycle and the postdisposal plan, this paper systematically reviews the internal and external factors, the characterization methods and the performance parameters that affect the membrane aging, and also discusses the membrane performance factors, the chemical/physical properties, the analysis methods and their interrelationships. The inconsistent research results between the laboratory simulation and the actual operation show that in the study of the membrane aging process it is necessary to consider not only the interaction between the membrane material and the chemical cleaning agent, but also the interaction between the membrane and its surface contaminants. Due to the complexity of the membrane aging process, the life cycle analysis is one of the feasible methods to assess the impact of the membrane aging.

The key odorant provides a vital indicator for the odor detection, evaluation and control. This paper reviews the key odorant identification methods around the world, including their weakness, and gives a proposal. It is shown that the Odor Activity Value(OAV), the common method, suffers a large deviation, because its application is limited by the two dimensions of the substance concentration and the olfactory threshold. In addition, the odor activity value method is based on the fact that there is no interaction between various substances, without considering the synergy or the antagonism between the substances. The gas chromatography olfactometry (GC-O) is a more advanced technology, which can realize the simultaneous analysis of the chemical concentration and the sensory evaluation. However, the sample analysis for this method takes a long time and requires the olfactory discriminator at a high level, so a rapid screening is not possible. In conclusion, there are several aspects to be considered in the future:establishing a systematic method to enhance the ability to identify the odorant; improving the odor threshold database to complete the odor thresholds and inconsistent values; studying the odor mechanism and the interaction between odorous substances to provide a theoretical research basis; developing multiple methods to advance the detectability.

With the super SBM-Undesirable model, this study evaluates the air pollution emission efficiency in 108 cities of the Yangtze River economic belt from 2007 to 2017. The relationship between the industrial structure evolution and the urban air pollution emission efficiency is confirmed by using the coupling coordination degree model and the Tobit model. The findings are as follows:(1) Only 6 cities reach the efficiency frontier of the average air pollution emission efficiencies. The regions in terms of the average air pollution emission efficiency from high to low are in this order:the downstream region, the midstream region and the upstream region; (2) The coupling coordination of the air pollution emission efficiency and the industrial structure rationalization, the air pollution emission efficiency and the industrial structure upgrading in the midstream and upstream cities are significantly lower than those of the downstream cities; (3) The industrial structure rationalization and the industrial structure upgrading are conducive to the improvement of the air pollution emission efficiency in cities of the Yangtze River economic belt. For the cities that have not achieved the coupling coordination of the air pollution emission efficiency and the industrial structure, the integrated development strategy of the industrial structure development and the environmental protection should be formulated.

As an important measure to strengthen the local government's enforcement in the environmental protection and to promote the national sustainable air pollution control, using the panel data of 225 prefecture-level cities in China from 2014 to 2018, this paper analyzes the policy effect of the central environmental protection inspection on the local air quality improvements by applying the multi-phase difference-in-differences method. It is shown that the central inspection of the ecological and environmental protection has a significant effect on the reduction of PM10, SO₂, and CO; a continuous effect on the reduction of the local SO₂ and CO; while it does not work well for the sustainable reduction of PM10. For the improvement of the local air quality, we suggest to further implement the Central Inspection of Ecological and Environmental Protection, and to pay more attention to the control of the mobile sources pollution, the construction dust, and the secondary air pollutants.

Based on the panel data of 285 cities from 2005 to 2016, the interactive relationship among the urban innovation behavior, the economic development and the environmental pollution is studied, and a panel threshold model is used, with the urban innovation behavior as the threshold, to verify the nonlinear relationship between the economic development and the environmental pollution. One sees an inverted U-shaped relationship between the levels of the economic development and the environmental pollution, and it is a single threshold nonlinear relationship based on the urban innovation behavior. Only when the level of the urban innovation crosses the threshold value, the economic development has a significant inhibitory effect on the environmental pollution. In the sample range, the level of the urban innovation constantly crosses the threshold, and the number of cities in the eastern region with the level of the urban innovation crossing the threshold is larger than those in the central and western regions. The industrial structure upgrading and the population agglomeration also help to reduce the environmental pollution, while the increase of the energy consumption will aggravate the environmental pollution. For all cities, the level of the urban innovation should be improved, to speed up the optimization and the upgrading of the industrial structure and to promote the development of green economy.

In a quasi-natural experiment of the expansion of the Yangtze River Delta, the panel data of 211 cities in China from 2008 to 2017 are analyzed. The difference-in-difference method is adopted to analyze the influence and the internal mechanism of the pollution emissions in related cities after the expansion of the Yangtze River Delta. The PSM-DID estimation, the parallel trend test, the synthetic control methods and the placebo test are adopted for the robustness test. It is shown that the expansion of the Yangtze River Delta would significantly reduce the pollution emissions in all related cities and the incumbent cities, but the reduction in the incumbent cities is greater than that in all related cities. The reduction of the emissions of the pollution is not significant in the new cities. In terms of the influencing mechanism, the pollution emissions in the whole Yangtze River Delta are significantly reduced through the scale effect, the technology effect and the structure effect, while the reduction of the pollution emissions is not so significant in the new cities due to the time delay. Therefore, it is necessary to strengthen the integrated regional development for the urban agglomeration and enhance the cooperation mechanism of the environmental pollution control in innovative regions, so as to realize the"win-win"goal-the regional economic development and the environmental protection improvement.

This paper makes a statistical analysis of the membrane separation projects funded by the National Natural Science Foundation of China (NSFC) from 2000 to 2019, including the types of the projects funded, the project names, the leading scholars of the projects, the amounts of funds, the supporting entities, and the regions of the related research groups. It is shown that during these 20 years:(1) the NSFC has funded 920 projects in the field of the membrane separation, with a total funding of 54,684 million yuan, and the number and the funding of the projects have shown an increasing trend year by year. (2) Beijing, Jiangsu, Tianjin, Zhejiang and Liaoning are the five major membrane separation research areas in China. (3) The number of projects and the funding for the membrane water treatment technologies, such as the ultrafiltration, the nanofiltration, the reverse osmosis and the forward osmosis, have increased rapidly after 2010, while the growth of the membrane reactors is relatively slow. (4) From the perspective of the key projects and the major projects, the research directions in recent years have mainly focused on the hydrogen membrane separation technology and the carbon dioxide membrane separation technology in the gas separation field, and on the drinking water treatment and the wastewater regeneration technology in the water treatment field.

The built environment has a close relation with the travel carbon emissions of local residents. This study firstly reviews the development framework and the theoretical basis of the resident' travel behavior theory. Based on this framework, the measurement index of the built environment and its influence on the number of cars owned by the residents and the travel carbon emission are analyzed, and the residential self-selection effect of their relations is revealed. It is shown that the built environment measurement index and its impact on the residents' travel carbon emissions are not uniform.

The effectiveness evaluation of the joint combat system has important significance. In order to solve the problem of the confrontation effectiveness evaluation of the system-of-systems in the complex combat background, the typical effectiveness evaluation methods are reviewed. The proposed methods can provide a methodological support for the effectiveness evaluation of the operation system-of-systems. Their advantages and disadvantages are illustrated. The problems involved in the existing methods are discussed.

Ionic liquids with high thermal stability, non-volatility and good solubility are often used as green solvents and catalysts. Recently, the application of ionic liquids in flame retardant polymers is increasing. In this paper, the application and progress of ionic liquid as flame retardant in polymers are reviewed, including the main types, synthesis, mechanism, action mode and application of ionic liquid in different polymers. The catalytic carbonization of ionic liquid and multi-element synergy flame retardant mechanism are widely accepted. In terms of the future trend of ionic liquids, halogen-free and nano-flame retardant compounds show great potential in future. In addition, the designability of ionic liquids provides an opportunity for the synthesis of new flame retardants and broadens the application of polymer flame retardants by ionic liquids.