Distributed cooperative controller design considering guidance loop and impact angle

This paper presents an integrated distributed cooperative guidance and control scheme for multiple missiles to attack a single target simultaneously at desired impact angles. The scheme is divided into two parts: individual part and cooperative part. For the individual part, partial integrated guidance and control method is adopted to generate the elevator deflection (which is a realistic control input) to ensure that the missiles fly along their respective desired line of sight and hit the target; this is in contrast to previous works which analyze only the engagement dynamics and use missile accelerations as the control input, however, the proposed controller also considers the missile dynamics, thus enabling the implementation of an autopilot. For the cooperative part, using only information from adjacent missiles, the proposed distributed cooperative controller can make all missiles hit the target simultaneously. Hence in this scheme, each missile can hit the target at desired angles and at the same time, thus achieving salvo attack. Simulations are performed to verify the effectiveness of the scheme.     

国内外政务社交媒体研究评述及展望

[目的/意义] 本研究对国内外政务社交媒体相关研究进行梳理,分析现有研究的特点及不足,以期为政务社交媒体研究提供参考和借鉴。[方法/过程] 通过文献调研,对2014-2019年的国内外政务社交媒体研究进行系统归纳,梳理现有研究的特点及不足,以期为政务社交媒体研究提供参考和借鉴。[结果/总结] 分析发现近年的政务社交媒体研究多为量化研究,分析方法包括内容分析法、统计分析法、社会网络分析法、机器学习方法,研究主题集中于政务社交媒体的运营管理、内容挖掘、应急管理、功能与作用。现有研究存在着数据来源较为单一、数据分析方法有待优化、缺乏系统规范的研究范式等方面的不足,并从政府和公众两个视角为政务社交媒体的未来研究提供思路。     

基于层次结构的网页自动分类系统的设计与实现

构建了基于层次结构的网页自动分类系统;探讨了该系统中涉及的各项关键技术和构建方法;实现了平面分类和层次分类两种分类方法,并对两种分类方法在网络基础教育资源的环境下进行测试,给出了评价与分析.实验表明,层次分类方法有利于提高分类效率和分类效果.     

基于任务的听力教学设计研究

本文尝试从交际语言能力的界定、/语言使用任务及语言材料真实性,三个层面来探讨基于任务的语言教学理论;并以此为理论依据,尝试进行基于任务的听力教学设计研究,即从语言学习者需求出发,将雅思听力材料引入大学英语听力教学,选择合适的听力任务,进行任务教学,以期达到培养学习者英语交际能力的目标。     

中国山水画的精神解析

自然山水作为中国山水画创作的永恒主题,有中国古代文化的基因之缘。自然山水在中国人的心中具有寓意的象征,山水代表着宇宙自然。中国山水画的美学精神是人与自然的和谐同一,中国人移情于山水来传达内心的深情,是灌注了主观性情的人化自然,是自然与人的生命精神的融合。     

What (more) can,and should,assessment do for learning? Observations from ‘successful learning context’ in Singapore

Singapore has earned accolades as one of the leading education systems in the world, based on its record in international assessments, including TIMMS and PISA. This has contributed to the entrenchment of ‘assessment’ becoming an institutional authority of standards, teaching (performativity) and classroom learning. It is against, and amidst such contexts, that this article traces how the notion and discourse of formative assessment and Assessment for Learning (AfL) are widely introduced and used formally across all Singaporean schools, particularly after a recent introduction of new ‘Holistic and Balanced Assessment’ policies. We argue that the very institutional authority of successful high-stake examination results, which served as critical standards of performativity of teaching and learning in the classroom, is being challenged. The changing assessment context of Singaporean schools, therefore serves as an interesting case study site for studying how formative assessment and AfL can be adapted and understood when ‘learning’ is already seen to be successful.     

A heuristic hierarchical scheme for academic search and retrieval

We present PubSearch, a hybrid heuristic scheme for re-ranking academic papers retrieved from standard digital libraries such as the ACM Portal. The scheme is based on the hierarchical combination of a custom implementation of the term frequency heuristic, a time-depreciated citation score and a graph-theoretic computed score that relates the paper’s index terms with each other. We designed and developed a meta-search engine that submits user queries to standard digital repositories of academic publications and re-ranks the repository results using the hierarchical heuristic scheme. We evaluate our proposed re-ranking scheme via user feedback against the results of ACM Portal on a total of 58 different user queries specified from 15 different users. The results show that our proposed scheme significantly outperforms ACM Portal in terms of retrieval precision as measured by most common metrics in Information Retrieval including Normalized Discounted Cumulative Gain (NDCG), Expected Reciprocal Rank (ERR) as well as a newly introduced lexicographic rule (LEX) of ranking search results. In particular, PubSearch outperforms ACM Portal by more than 77% in terms of ERR, by more than 11% in terms of NDCG, and by more than 907.5% in terms of LEX. We also re-rank the top-10 results of a subset of the original 58 user queries produced by Google Scholar, Microsoft Academic Search, and ArnetMiner; the results show that PubSearch compares very well against these search engines as well. The proposed scheme can be easily plugged in any existing search engine for retrieval of academic publications.     

具有容错特性的反馈控制

考虑到最优反馈控制在部分执行器（传感器）失效时仍能使系统稳定运行的条件，给出了求解该总理的算法，并用实例作了说明。     

高校图书馆的组织重组研究

网络信息环境的日新月异、用户信息需求的不断增强以及各种管理理念的提出都深刻影响着图书馆的发展，给图书馆的发展带来了机遇与挑战。如何实行图书馆组织机构的有效重组，使图书馆更加适应新的发展环境，是目前图书馆业内人士探讨的一个热门话题。本文从全国60余家高校图书馆现行组织机构调研入手，分析了目前国内高校图书馆组织结构的现状，并对高校图书馆组织机构重组的原则、模式进行了探讨。     

对我国篮球理论研究现状的思考

本文运用文献资料、逻辑分析等研究方法, 就我国篮球理论研究的历史进行了简要的回顾与总结, 分析了我国篮球理论研究存在的不足, 提出了现阶段我国篮球理论研究亟待解决的问题, 以期我国篮球理论研究有新的突破