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In order to meet the requirements of informationized and intelligent air warfare characterized by system confrontation, countries all over the world keep pushing forward the new concept of air-to-air missile. The US Air Force’s Next Generation Air Dominance(NGAD) project sets up Air Dominance Air-to-Air Weapon program to explore and integrate new missile concepts for its next generation stealth fighter aircraft, examples include the AIM-260 Joint Advanced Tactical Missile(JATM) and Modular Advanced Mission(MAM). At the same time, the US Air Force has vigorously promoted missile digital engineering, for example Pathfinder projects such as Weapon ONE have been launched, utilizing digital twin technology to quickly enhance weapon combat capabilities and improve research and acquisition processes.France and Britain are developing much of the next generation missile technologies under Materials and Components for Missiles, Innovation and Technology Partnership(MCM ITP)and Complex Weapon Innovation and Technology Partnership(CW ITP) projects. Russia, Israel, India and Japan are also developing their own new generation of air-to-air missile. The emergence of a large number of new technologies promotes the rapid development of air-to-air missile. The anti-stealth, anti-jamming performance and the level of miniaturization, networking, multi-purpose, digitalization and intelligence for the new air-to-air missile to adapt to the complex combat environment. In the future, air-to-air missile will be given new missions with new attitudes and play a greater role in the air combat system.

The US pays great attention to and leads the development of hypersonic weapon defense technology in the world, vigorously promots hypersonic defense programs such as Hypersonic Defense Weapon Concept Definition, Hypersonic Defense Component Technology, High Overload Aerodynamic Control and Glide Breaker, explores hypersonic weapon interception capabilities. Faced to continuous development of the US hypersonic weapons, Russia designs a multipurpose long-range interceptor missile system for MiG-31 and MiG-41 fighter. This long-range air-to-air missile with son-missiles can destroy incoming hypersonic missiles and pose a threat to high value enemy targets such as early warning aircraft and aerial refueling aircraft hundreds of kilometers away. Europe, which has a blank missile defense capability, is ready to take this opportunity to leapfrog forward and launch Timely Warning and Interception with Space-based Theater Surveillance program to develop ballistic missile and hypersonic missile defense systems. In this paper, the development states of hypersonic defense weapon in US, Russia and Europe are studied.

[Objective] The spatiotemporal changes of different grades of sloping farmland, the soil conservation effects of different sloping farmland types, and the impact of returning farmland to forest or grassland on sloping farmland and soil conservation at the source area of Weihe River were studied in order to provide a scientific basis for the rational planning and utilization of different sloping farmland resources. [Methods] Land use and topographic data at the source area of Weihe River from 1990 to 2020 were analyzed by superposition analysis, farmland dynamic attitude, land use transfer matrix, and the Chinese soil loss equation. [Results] ① During 1990 to 2020, the area of cultivated land increased slowly, then decreased sharply, and then decreased slowly, with a net decrease of 321.03 km2. Steep slope cultivated land and gentle slope cultivated land were the main types of cultivated land change. ② The temporal and spatial changes of cultivated land were mainly characterized by a small increase in cultivated land from 1990 to 2000, mainly located in Zhangxian County and Minxian County. With the implementation of the grain for green project (GGP), 279.80 km2 of sloping land were transformed into forest and grassland, in which the conversion of cultivated land to grassland was mainly located in Tongwei and Longxi counties, while the conversion of cultivated land to forest land was mainly located in Longxi and Minxian counties. ③ The reclamation of forest and grassland at the source area of Weihe River from 1990 to 2000 reduced soil conservation by 5.52×104 t, while returning farmland to forest and grassland increased soil conservation by 2.21×106 t from 2000 to 2020. The transformation of sloping land with greater than 15° slope could affect changes in soil conservation. [Conclusion] The implementation of GGP has achieved remarkable results at the source area of Weihe River. The area of farmland conversion on steep slopes was the largest from 2000 to 2010. The soil conservation effect on steep slopes was the largest on abandoned land. Steeply sloping farmland will be the main target during the new round of returning farmland.

As an important attack weapon in information countermeasures, high-power microwave weapon can interfere with or damage important enemy sensors, destroy key electronic components and pose a great threat to radar, navigation, communication systems, battlefield awareness systems and other weapon equipments. Now high-power microwave weapon technology has become a research hotspot in the world and also a new concept weapon technology under development. the US, Russia and European Defense Agency attach great importance to the development and application of the technology. Currently, the US is a leader in research on high-power microwave sources, high-power microwave emission and transmission, high-power microwave effects and protection. A major breakthrough has been made in miniaturization of high-power microwave warhead and accurate beam control. Russia is leading the way in repetition frequency pulse power sources and high-power microwave generation technology. In this paper, the development states of high-power microwave weapons of US, Russia and European Defense Agency are investigated.

The quality of food safety sampling inspection data are a comprehensive reflection of the technical ability, professional competence, and management service level of inspection institutions. It is an important guarantee for the effectiveness of food safety sampling inspection work, and a key factor in doing a good job in verification and disposal work. Market regulatory administrations have strengthened the verification of food sampling inspection data in recent years, which have played a good role in improving the quality of food safety sampling inspection data. However, it was found that some inspection and testing institutions have some problems in sampling, inspection, and report standardization during the data verification process. It will have a certain impact on subsequent regulatory and administrative penalties. This article analyzes common problems in the daily sampling inspection process and proposes some measures to optimize food safety sampling inspection work, wishing to provide reference for food safety supervision and sampling inspection personnel.

Along with the arrival of the digital era, promoting the high-quality development of rural tourism with a digital economy has become a new driving force and goal. This study examines the mechanism of digital technology to promote the high-quality development of rural tourism based on the perspective of stakeholders in rural tourism development. After selecting the evaluation indexes of digital technology to promote the high-quality development of rural tourism, the weights of the indexes are determined, and the level of digital technology to promote the high-quality development of rural tourism is measured by using the fuzzy comprehensive evaluation method in a rural tourism site as an example. The driving force factors of digital technology to promote the high-quality development of rural tourism are selected from both internal and external dimensions, and the driving force of digital technology to promote the high-quality development of rural tourism is analyzed by using geographic detectors for divergence and factor detection and interaction detection. The results can be obtained that the overall development of the sample rural tourism sites is located between average and better, with a comprehensive score of 6.842, especially in its cultural digitization and environmental monitoring digitization, with scores greater than 6. Digital technology to promote the high-quality development of rural tourism is subject to the joint effect of a variety of factors. The number of Internet broadband access ports is the core factor, and the factor contribution rates are all above 0.8. The research on effects and driving forces in this paper is of great significance in achieving high-quality development of rural tourism.

In recent years, the etiology of periodontitis has tended to be based on the theory of flora imbalance. That is, periodontitis is not caused by specific bacteria but by the breakdown of the oral flora balance, which leads to an immune imbalance. Imbalanced bacterial flora cooperate with each other to produce virulent factors that destroy organism tissues and induce immune cells to produce abnormal levels of cytokines, causing greater damage. This article reviews the initiation of a flora imbalance, the interaction between bacteria, the immune damage of the host and the prevention and treatment of the flora imbalance. The literature review shows that peroxidase released by inflammatory reactions, host immune responses to pathogenic microorganisms and some systemic factors, such as diabetes, can trigger flora imbalance. As a result, ion transport, substance synthesis and metabolism of bacteria change; virulence factors increase; and the oral flora balance is disrupted. Red complex bacteria enter gingival epithelial cells, produce adhesin, and selectively inhibit the expression of specific chemokines, which is beneficial for other pathogenic bacteria to enter gingival epithelial cells. Toxicity factors increase throughout the body, directly destroying body tissues and inducing innate and adaptive immune responses, thus causing related immune damage. The dysbacteriosis model of periodontitis provides a new idea for the prevention and treatment of periodontitis, such as using biological factors, bacteriophages, probiotics and other methods to reduce the number of periodontal pathogens to restore the steady state of periodontal flora.

Background: The aim of this study was to investigate the correlation between maternal serum homocysteine (Hcy), folate, vitamin B12 (VitB12) and the development of pre-eclampsia (PE).

Cyanobacterial bloom elimination has become an urgent concern in aquatic environment protection. Allelopathic technology, however, is one of the potential effective approaches because of its exclusive and ecological safety protection. The potential application of chitosan fiber in the inhibition of Microcystis aeruginosa was explored for the first time. Results showed that the cell growth of M. aeruginosa was inhibited effectively by chitosan fibers. After 12 days of treatment, the inhibition rate (IR) of algal cells was above 78.9%; those of chlorophyll a and carotenoids in algal cells were 86.9% and 93.1%, respectively; those of phycocyanin, allophycocyanin and phycoerythrin in phycobiliproteins were all approximately 100%; those of soluble proteins and algal toxins were 88% and 100%, respectively; and those of superoxide dismutase and catalase activities were 68% and 74%, respectively. In addition, chitosan fiber effectively destroyed the structure of algal cells involved in the photosynthetic process, thereby destroying the metabolic activity of algal cells. This study provides a novel method utilizing a new allelopathic material.

Leadership behavior of classroom teachers has a significant impact on students' academic success. However, little empirical research on this subject has been undertaken in China. By developing truth tables and doing necessary computations, this study examines the influence of differential combinations of parameters connected to class teachers' qualities and leadership behavior on student academic performance. It has been discovered that the democratic leadership behavior displayed by class teachers is the most popular among students and is helpful to student academic achievement; the numerous combinations of linked characteristics have varying effects on student academic performance. The study compensates for a dearth of empirical research on the subject and sheds light on the process by which class teacher leadership influences student academic progress.