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Rapid economic growth leads to such problems as resource scarcity and environmental degradation. Local governments successively take measures such as technological innovation to solve atmospheric environmental pollution; however, technological innovation fails to fundamentally alleviate atmospheric environmental pollution. Therefore, local governments come to realize the importance of green-technology innovation, which means an inevitable choice for various countries in the world to seek long-term development and win competitive advantage. Under such circumstances, this paper chooses the panel data of 30 provinces and regions in China from 2005 to 2018, takes environmental regulation as the threshold variable, and empirically analyzes the relationship between green-technology innovation and atmospheric environmental pollution by constructing a Spatial Measurement Model and Panel Regression Model. As evinced, green-technology innovation has a significant inhibitory effect and a spatial spillover effect on atmospheric environmental pollution. When environmental regulation reaches a level of intensity, green-technology innovation can effectively curb atmospheric environmental pollution. Accordingly, relevant parties should strengthen green-technology innovation, coordinate the development of the governance system of green-technology innovation, establish a joint prevention and control mechanism, increase the investment in green technology research and development, and augment the role of green-technology innovation. [ABSTRACT FROM AUTHOR]

With the accelerating urbanization process in China, the extensive economic growth model with high energy consumption and high pollution aggravates atmospheric environmental pollution and restricts the sustainable development of the social economy. The Beijing–Tianjin–Hebei region has the most severe haze pollution and the most acute contradiction between resources, environment and economic development. Based on the physical coupling theory, this paper constructs a coupling coordination degree model of the economy, environment and high haze pollution industries, such as the thermal power industry. Through literature analysis and expert investigation of the economic, industrial and environmental data of the Beijing–Tianjin–Hebei region from 2006 to 2018, the coordinated development of the economy, environment and high haze pollution industries, such as the thermal power industry, in the above region, was dynamically monitored. The monitoring results show that the development level of the Beijing, Tianjin and Hebei region is significantly different, and the three subregions have not entered the stage of coordinated development. Moreover, since 2015, they have been in a bottleneck period of development and have not achieved a higher level of progress. The three subregions have different advantages and restraining factors. For example, the backward level of Hebei's economy and high haze pollution industries, such as the thermal power industry, restrict the coordinated development of the region as a whole. Only by accelerating the high-quality development of the Hebei economy can we break through the bottleneck of the development of Beijing, Tianjin and Hebei. [ABSTRACT FROM AUTHOR]

The iron and steel industry is an important foundation of the national economy. It is the inevitable choice, to achieve high-quality development in the new era of the iron and steel industry, to speed up the green development of the iron and steel industry. This paper studies the effect of steel industry agglomeration on regional economic growth and air pollution. Through the analysis of the characteristics of iron and steel industry agglomeration, and the empirical analysis of the relationship between iron and steel industry agglomeration, regional economic growth, and air pollution, it is found that: (1) Iron and steel industry agglomeration helps to promote economic growth; (2) Iron and steel industry agglomeration has an obvious spatial correlation effect and obviously drives the development of surrounding areas; (3) Iron and steel industry agglomeration will cause air pollution. The marginal effect of air pollution will decline rapidly with the development of iron and steel industry agglomeration. (4) The impact of green process innovation investment on air pollution presents an inverted U-shaped effect, which has a positive effect on air recovery after exceeding the critical point. (5) The air self-purification capacity represented by precipitation, helps to reduce air pollution. Based on the above conclusions, this paper puts forward some policy suggestions, such as making a scientific development plan for the iron and steel industry, accelerating green process innovation, effectively improving regional precipitation and precipitation times, vigorously promoting high-quality development of the regional economy, and comprehensively promoting coordinated development of the iron and steel industry, so as to cope with the dilemma of the coordinated development of the iron and steel industry, regional economic growth, and smog pollution, and strive for international development in the future. In the competition, we should gain the first opportunity and obvious competitive advantage. [ABSTRACT FROM AUTHOR]

A pump-jet, which is generally and widely adopted on underwater vehicles for applications from deep sea exploration to mine clearing, consists of a rotor, stator, and duct, with the properties of high critical speed, high propulsion efficiency, great anti-cavitation performance, and low radiated noise. The complex interaction of the flow field between the various components and the high degree of coupling with the appendage result in the requirements of in-depth research on the hydrodynamic performance and flow field for application and design. Due to the initial application on the military field and complicated structure, there is scant literature in the evaluation of pump-jet performance and optimal design. This paper, in a comprehensive and specialized way, summarizes the pump-jet hydrodynamic performance, noise performance, and flow field characteristics involving cavitation erosion and vortices properties of tip-clearance, the interaction between the rotor and the stator and the wake field, as well as the optimal design of the pump-jet. The merits and applications range of numerical and experimental methods are overviewed as well as the design method. It also concludes the main challenges faced in practical applications and proposes a vision for future research. It was found that the compact structure and complex internal and external flow field make the pump-jet significantly different, also leading to higher performance. As the focus of cavitation research, vortices interact with the complex structure of the pump-jet, leading to instabilities of the flow field, such as vibration, radiated noise, and cavitation erosion. The effective approaches are adopted to reduce radiated pump-jet with minimal influence on the hydrodynamic performance, such as eliminating the tip clearance and installing the sawtooth duct. Advanced optimal technology can achieve high performance, cavitation performance, and acoustic performance, possessing good prospects. Further developments in investigation and the application of pump-jets in the multidisciplinary integration of fluid dynamics, acoustics, materials, chemistry, and bionics should be the main focus in future research. [ABSTRACT FROM AUTHOR]

Landscape pattern changes caused by human activities are among the most important driving factors affecting ecosystem spatial structure and components, and significantly impact ecosystem services. Understanding the relationship between landscape patterns and ecosystem services is important for improving regional conservation and establishing ecosystem management strategies. Taking the Huaihe River Basin as an example, this study used land-use data, meteorological data, and topographic data to analyze the spatial and temporal changes in landscape patterns via landscape transfer matrix and landscape indices, and measured four ecosystem services (water retention, soil retention, carbon storage, and biodiversity conservation) with the InVEST models. Furthermore, correlation analysis and global spatial autocorrelation coefficient were used to analyze the impact of landscape pattern changes on ecosystem services. The results showed grassland and farmland areas had continuously decreased, while built-up land and affected water had significantly increased. Landscape fragmentation was reduced, the connectivity between patches was weakened, landscape heterogeneity, evenness, and patch irregularity were increased. Changes in landscape composition and configuration have affected the ecosystem services of the Huaihe River Basin. The reduction in grassland areas and the increase in built-up land areas have significantly reduced the capacity for soil retention, carbon storage, and biodiversity conservation. Spatially, regions with low landscape fragmentation and high patch connectivity had a higher water retention capacity and biodiversity conservation, while soil retention and carbon storage were opposite. Temporally, reduction of landscape fragmentation and increase of patch shape irregularity had a negative effect on water retention, carbon storage, and biodiversity conservation, while soil retention was not sensitive to these changes. The findings in this paper promote an understanding of the relationship between landscape patterns and ecosystem services on a large scale and provide theoretical guidance for ecosystem management and protection planning in the Huaihe River Basin, China. [ABSTRACT FROM AUTHOR]

When a pump-jet propeller rotates at high speeds, a tip vortex is usually generated in the tip clearance region. This vortex interacts with the main channel fluid flow leading to the main energy loss of the rotor system. Moreover, operating at a high rotational speed can cause cavitation near the blades which may jeopardize the propulsion efficiency and induce noise. In order to effectively improve the propulsion efficiency of the pump-jet propeller, it is mandatory to research more about the energy loss mechanism in the tip clearance area. Due to the complex turbulence characteristics of the blade tip vortex, the widely used Reynolds averaged Navier–Stokes (RANS) method may not be able to accurately predict the multi-scale turbulent flow in the tip clearance. In this paper, an unsteady numerical simulation was conducted on the three-dimensional full flow field of a pump-jet propeller based on the DES (detached-eddy-simulation) turbulence model and the Z-G-B (Zwart–Gerber–Belamri) cavitation model. The simulation yielded the vortex shape and dynamic characteristics of the vortex core and the surrounding flow field in the tip clearance area. After cavitation occurred, the influence of cavitation bubbles on tip vortices was also studied. The results revealed two kinds of vortices in the tip clearance area, namely tip leakage vortex (TLV) and tip separation vortex (TSV). Slight cavitation at J = 1.02 led to low-frequency and high-frequency pulsation in the TLV vortex core. This occurrence of cavitation promotes the expansion and contraction of the tip vortex. Further, when the advance ratio changes into J = 0.73, a third type of vortex located between TLV and TSV appeared at the trailing edge which runs through the entire rotational cycle. This study has presented the dynamic characteristics of tip vortex including the relationship between cavitation bubbles and TLV inside the pump-jet propeller, which may provide a reference for the optimal design of future pump-jet propellers. [ABSTRACT FROM AUTHOR]

Optimal design of wind turbine placement in a wind farm is one of the most effective tools to reduce wake power losses by alleviating the wake effect in the wind farm. In comparison to the discrete grid-based wind farm design method, the continuous coordinate method has the property of continuously varying the placement of wind turbines, and hence, is far more capable of obtaining the global optimum solutions. In this paper, the coordinate method was applied to optimize the layout of a real offshore wind farm for both simplified and realistic wind conditions. A new analytical wake model (Jensen-Gaussian model) taking into account the wake velocity variation in the radial direction was employed for the optimization study. The means of handling the irregular real wind farm boundary were proposed to guarantee that the optimized wind turbine positions are feasible within the wind farm boundary, and the discretization method was applied for the evaluation of wind farm power output under Weibull distribution. By investigating the wind farm layout optimization under different wind conditions, it showed that the total wind farm power output increased linearly with an increasing number of wind turbines. Under some particular wind conditions (e.g., constant wind speed and wind direction, and Weibull distribution), almost the same power losses were obtained under the wake effect of some adjacent wind turbine numbers. A common feature of the wind turbine placements regardless of the wind conditions was that they were distributed along the wind farm boundary as much as possible in order to alleviate the wake effect. [ABSTRACT FROM AUTHOR]

Pump-jet propulsion, a new propulsion technology, is primarily designed for underwater vehicles. Because of its concealment and excellent performance, it has been widely used, but due to its confidentiality and complexity, few studies have been published. To explore the relevant design theory of pump-jet propulsion with the aim of increasing its performance, in this study, we applied the direct and inverse design methods to construct a three-dimensional pump-jet model. The direct design method was carried out by comparing the lifting and lifting-line design methods, followed by further geometric optimization of the better model. In a numerical study using computational fluid dynamics (CFD) simulations, the Reynolds Averaged Naviere-Stokes (RANS) equations with SST k-ω turbulence model were solved in a cylindrical computational domain around the pump-jet propulsion device. A numerical investigation of the E779A propeller was carried out beforehand, using different advance ratios, in order to validate the accuracy of the numerical simulation method. The results show that for the direct method, although the model designed using the lifting-line method produced a greater thrust and the pump-jet designed using the lifting method was more efficient and stable, which is more suitable for small and medium underwater vehicles. When considering the inverse design method, the pump-jet propeller obviously accelerated the fluid, and the speed was obviously greater than that designed using the direct design method, while the turbulent kinetic energy in the flow field was higher, as well as the energy loss. Therefore, for small- and medium-sized underwater vehicles, if the priorities are high thrust and high efficiency, the inverse design method is the best option, whereas if stability and lower energy loss are preferred, the direct design method should be adopted. [ABSTRACT FROM AUTHOR]

Because the Three Gorges Dam (TGD) has disturbed the normal hydrological regime downstream, analyzing the influence of the TGD on water level fluctuation is of great importance to ecological planning. The distribution and dynamic of the water level before and after the TGD were analyzed using frequency distribution and a complex network. Frequency distribution was unimodal before the TGD, and the peak ranged from 13–15 m. Frequency distribution was bimodal after TGD and two peaks ranged from 9–10 m and 16–17 m. The number of days when the water level was above warning level was reduced, and it was increased when the water level was below the ecological level. Further, the TGD had little effect on the number of days of rapid water level rising, which mainly existed during the flood season. However, this imposed a greater influence on the number of days of rapid water level decline, which implies a weaker intensity of the recession process, along with a longer duration. Thirdly, in winter and spring, the water level after the TGD was lower than that before the TGD by approximately 1 m. In summer, the number of days when the water level was above warning level was reduced. In autumn, the frequency distribution changed from unimodal to bimodal. The TGD has the greatest influence during the winter, which resulted in a lower water level and more severe drought. [ABSTRACT FROM AUTHOR]