Cell-free systems can effectively eliminate the inter-cell interference by enabling multiple base stations (BSs) to cooperatively serve users without cell boundaries at the expense of high costs of ...hardware and power sources due to the large-scale deployment of BSs. To tackle this issue, the low-cost reconfigurable intelligent surface (RIS) can serve as a promising technique to improve the energy efficiency of cell-free systems. In this article, we consider an RIS aided cell-free MIMO system where multiple RISs are deployed around BSs and users to create favorable propagation conditions via reconfigurable reflections in a low-cost way, thereby enhancing cell-free MIMO communications. To maximize the energy efficiency, a hybrid beamforming (HBF) scheme consisting of the digital beamforming at BSs and the RIS-based analog beamforming is proposed. The energy efficiency maximization problem is formulated and an iterative algorithm is designed to solve this problem. The impact of the transmit power, the number of RIS, and the RIS size on energy efficiency are investigated. Both theoretical analysis and simulation results reveal that the optimal energy efficiency depends on the numbers of RISs and the RIS size. Numerical evaluations also show that the proposed system can achieve a higher energy efficiency than conventional ones.
Abstract
Contemporary feminism is currently at a crossroads, facing a concerted onslaught from both neoliberal and neoconservative ideologies. While these ideologies are inherently ...different—neoliberalism often appropriates feminist language to serve capitalist ends, and neoconservatism typically attacks feminist principles—they similarly reinforce the traditional role of families as providers of welfare. This crisis of alienation in feminism is characterized by three key factors: the gender divisions brought about by feminism’s shift to identity politics, the obscuring of feminist critique of capitalism by the spread of commercialization, and the instrumentalization of feminism in politics. These challenges have resulted in increased class antagonism and the further marginalization of lower-income women, reinforcing one another. To address this multifaceted crisis, a return to Marxist thought is deemed necessary for women’s liberation. The historical foundation of women’s issues can be traced back to class oppression, which stems from the primacy of material production over reproductive labor. In this context, gender oppression becomes an instrument that perpetuates class oppression. Only by interpreting women’s bodily autonomy and power from the perspective of material life and class reproduction, and by uniting various social forces against capitalism with practical actions, can feminism regain its vitality. Although the current global women’s movement is full of internal divisions, contradictions, and struggles, there is still hope for achieving unity. When the day comes, history will confirm that true gender equality is not merely the promotion of individual choice for a few, but the emancipation of all, and Marxism will be recorded once again in the history of human liberation. To accomplish this grand objective, the vital step is to end the marginalization of Marxist Feminism.
To enhance obstacle avoidance abilities of the plant protection UAV in unstructured farmland, this article improved the traditional A* algorithms through dynamic heuristic functions, search point ...optimization, and inflection point optimization based on millimeter wave radar and monocular camera data fusion. Obstacle information extraction experiments were carried out. The performance between the improved algorithm and traditional algorithm was compared. Additionally, obstacle avoidance experiments were also carried out. The results show that the maximum error in distance measurement of data fusion method was 8.2%. Additionally, the maximum error in obstacle width and height measurement were 27.3% and 18.5%, respectively. The improved algorithm is more useful in path planning, significantly reduces data processing time, search grid, and turning points. The algorithm at most increases path length by 2.0%, at least reduces data processing time by 68.4%, search grid by 74.9%, and turning points by 20.7%. The maximum trajectory offset error was proportional to the flight speed, with a maximum trajectory offset of 1.4 m. The distance between the UAV and obstacle was inversely proportional to flight speed, with a minimum distance of 1.6 m. This method can provide a new idea for obstacle avoidance of the plant protection UAV.
China’s public cultural service system transitioned from a centrally controlled model to a more complex one due to the gradual introduction of market forces. This change brought new challenges and ...opportunities, making the role of market forces a practical concern. By analyzing data from 282 public and 153 private children’s libraries in China, this study investigates how market forces compensate for the government’s capacity limitations in constructing public cultural service systems. Results show that market factors within the scope of our study do not negatively impact the system but instead promote synergy between government and market entities to meet children’s cultural needs. It is essential not to sever the role of the market from its interdependent relationship with the government, as this stance is based on unrealistic assessments of how policies function in practice, potentially leading to inadequate public cultural services. This study provides novel empirical evidence from China by confirming the interdependent relationship between the market and the government in constructing public cultural service systems and highlights the significance of applying complexity thinking. Overall, understanding the complexity of the role of market forces is essential for the construction of a robust and inclusive public cultural service system.
The corn production cost (CPC) in China is related to national food security. However, there are few studies on the temporal and regional differences (TRD) and sensitive factors in the CPC. In this ...paper, the TRD of the corn production cost across various regions, as well as over the entirety of the country from 2008 to 2018, is presented. It is based on the GIS exploratory spatial data analysis method (ESDA). Simultaneously, a spatial panel model is established to conduct an empirical analysis of the main factors affecting the CPC. The results from the period in question show that the CPC in China and the three major production regions present a fluctuating growth trend, mainly associated with the increase in labor prices. Moreover, the CPC exhibits significant spatial differences, and demonstrates an overall trend of gradual increase from the east to the west. Over time, the number of relatively high-cost provinces has increased. All are located in southern mountainous and hilly corn areas. In addition, the CPCs of various regions are spatially correlated. Factors such as the scale of land management, the degree of mechanization, and socioeconomic conditions have a significantly negative impact on the CPC in China. Furthermore, the labor structure has a notably positive impact on the CPC.
Downy blight, caused by
, is a destructive disease that impacts lychee fruit throughout the pre-harvest, post-harvest, and transportation phases. Therefore, the prompt and precise identification of
...is crucial for the effective management of the disease. A novel gene encoding a Rh-type ammonium transporter,
, was identified in
through bioinformatic analysis in this study. Based on this gene, a coupled recombinase polymerase amplification-lateral flow (RPA-LF) assay for the rapid visual detection of
was developed. The assay has been shown to detect
accurately, without cross-reactivity to related pathogenic oomycetes or fungi. Moreover, it can be performed effectively within 15 to 25 min at temperatures ranging from 28 to 46 °C. Under optimized conditions, the RPA-LF assay could detect as low as 1 pg of
genomic DNA in a 25 μL reaction system. Furthermore, the RPA-LF assay successfully detected
in infected lychee samples within a 30 min timeframe. These attributes establish the RPA-LF assay as a rapid, sensitive, and specific method for diagnosing
early; it is particularly suitable for applications in resource-limited settings.
Aiming at the problems of complicated structure, difficult processing and high cost of transplanting mechanism of pot seedling transplanting machine, this paper develops a kind of crank and rocker ...type transplanting mechanism. The mechanism consists of transplanting arm, eccentric wheel, connecting rod and cylindrical cam seedling clamp. This paper analyzes the working mechanism of the seedling picking mechanism, and establishes the geometric relations among the components by selecting the appropriate parameters of the seedling picking and releasing points of the crank and rocker mechanism. A set of optimal solutions are solved iteratively by using the software of Matlab. Meanwhile, the cam mechanism used to control the opening and closing of the seedling clamp is designed by using the geometric characteristics of the seedling clamp and the periodic characteristics of the seedling clamp, and the results of Matlab are modeled in SolidWorks and imported into Adams for virtual simulation analysis. The analysis results showed that the seedling clamp could reach the pre-set position to pick and release seedlings smoothly through the movement of the seedling picking mechanism, which verified the correctness of the mathematical model of the seedling picking mechanism.
Autonomous sprayer UAVs are one of the most used aerial machines in modern agriculture. During flight missions, some common narrow obstacles appear in the flying zone. These are non-detectable from ...satellite images and one of the biggest challenges for autonomous sprayer UAVs in farmland. This work introduces an obstacle avoidance architecture specifically for sprayer UAVs. This architecture has generality in the spraying UAV problem, and it reduces the reliance on the global mapping of farmland. This approach computes the avoiding path based on the onboard sensor fusion system in real-time. Moreover, it autonomously determines the transition of several maneuver states using the current spraying liquid data and the UAV dynamics data obtained by offline system identification. This approach accurately tracks the avoidance path for the nonlinear time-variant spraying UAV systems. To verify the performance of the approach, we performed multiple simulations with different spraying missions, and the method demonstrated a high spraying coverage of more than 98% while successfully avoiding all vertical obstacles. We also demonstrated the adaptability of our control architecture; the safe distance between the UAV and obstacles can be changed by specifying the value of a high-level parameter on the controller. The proposed method adds value to precision agriculture, reduces mission time, and maximizes the spraying area coverage.
This paper discusses the processing of desilting for silt of river and lake in order to improve the water quality. The technology system of multi-dimensional combination of trash sorting separation, ...separation of sand, silt amendment, silt concentration, silt flocculation, dehydration, solidification/stabilization and resource reuse are proposed. The average water content of the dehydrated silt is less than 45 percent in the practical project when the system was used. The dehydrated silt can be used for backfilling. The effect meets the expected demand. The given results provide valuable reference for the process and equipment of environmental desilting project.
Research shows that the accurate acquisition of flight parameters of the plant protection UAV and accurate evaluation of flight parameter quality have great significance for improving the effect and ...precision of spraying. In order to further improve the accuracy of the flight parameter quality evaluation of the plant protection UAV, this study conducted an evaluation and experiment of the flight parameter quality of the plant protection UAV using a laser tracker. The experimental results showed that the current plant protection UAV used the average altitude and speed of the onboard sensors to determine whether it reached the preset flight operation parameters, but this interpretation method could not accurately reflect the actual flight situation. Laser trackers could obtain more accurate flight parameters, especially instantaneous flight parameters. Compared with the laser tracker, the flight trajectory, altitude, and speed of the UAV reflected by onboard sensors were erroneous and tended to be smooth and stable. This method can obtain more accurate flight parameters, improve the accuracy of the flight parameter quality evaluation of the plant protection UAV, and provide data support and a reference for the precision spraying and performance improvement of the plant protection UAV.
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