Attenuation prediction for fade mitigation using neural network with in situ learning algorithm

Increasing demand of bandwidth in communication satellites has forced satellite links to be designed in Ku bands and above. But at these frequencies, rain and other tropospheric elements result in large attenuation. To mitigate the tropospheric attenuation of microwave satellite signals above 10 GHz using any standard Fade Mitigation Technique (FMT), it is essential to have a priori knowledge about the level of attenuation. Hence, short-term rain attenuation prediction models play a key role in maintaining the link in which necessary compensation can be applied depending on the early information of attenuation. This paper presents a method of attenuation prediction using Adaptive Artificial Neural Network. Here In situ Learning Algorithm (ILA) has been used to enable the system to track the non-stationary nature of the attenuation. To validate this, Ku Band data, collected at three different sites in India have been used for the purpose of prediction. The performance of the algorithm is determined through the estimation of prediction accuracy by comparing the predicted values with the measured data. Results obtained using the mentioned technique shows considerably good accuracy even up to 20 s of prediction interval with acceptable ratio between the under and over predictions. The prediction performance is evaluated for different prediction intervals. Furthermore the present model is also compared with the persistence model and the relative performance is quantified.     

一类MIMO非线性系统的局部化自适应控制

针对一类不确定多输入多输出非线性系统,提出了一种局部化鲁棒自适应控制方法.提出的方法采用了指令滤波反推进行虚拟控制律的迭代设计.使用局部化逼近器对未知函数进行在线逼近.引入谱半径,避免了控制系数矩阵的估计必须非奇异的假设.对于固有逼近误差和外部扰动,采用自适应边界控制进行补偿.在自适应律中引入局部化σ修改,保证了边界参数估计的有界性,同时克服了全局遗忘特性.稳定性分析证明了提出的控制方法能够保证闭环系统的所有信号有界.仿真实例进一步验证了提出方法的有效性.     

构建与“工学结合”相适应的《高等数学》课程体系

通过深入研究高职数学课程目标,以"够用为度",提出构建与高职"工学结合"人才培养模式相适应的、具有高职特色的新型数学课程体系。采用与"工学单元紧配合"人才培养模式相匹配的模块式结构,通过三个模块———公共数学模块、扩展模块、数学实验,整合教学内容,实现高职教育"针对不同的专业开设不同的数学课程"的教育目标。     

课堂学习共同体视野下高职生的主体性培养

当前高职教育教学实践大多忽视学生主体性培育,造成学生主体性残缺不全,这种现实违背了素质教育的宗旨。为改变这种状况,结合公共英语课程教学实践,英语教师借助于课堂学习共同体,探索对高职生进行主体性培育的路径。英语教师要走下讲台,为学生主体性发挥创设环境;提供实践活动情境,唤醒学生主体意识;借助于小组合作学习,促进学生主体参与,发展主体性能力;开展元认知策略训练,激发学生的自我主体性培育。     

改进型负输入成形主动振动控制

针对柔性结构的主动振动控制问题,提出了一种改进型负输入成形方法。该方法设计成形器的脉冲序列包含多个正负依次交替的脉冲,通过所选择的脉冲数目和系统振动频率与阻尼比构成封闭形式解来直接确定成形器。与正输入成形方法相比可以改善系统的上升时间,而与传统的负输入成形方法相比不需要对时间约束条件进行优化。改进型负输入成形器所包含的脉冲个数可以自由选择,具有设计简单、灵活的优点。将其通过柔性机械臂进行仿真验证,结果表明：所提出的方法有效且可以快速实现振动抑制。     

利用字典优化方法实现sub Nyquist采样数据的频率估计

在稀疏重构理论中,重构信号需要预先设定稀疏表示字典,针对预设字典与真实字典之间的失配对信号稀疏表示造成的不利影响,提出一种基于字典优化和稀疏贝叶斯学习(Sparse Bayesian Learning, SBL)的频率估计算法。该算法首先构造基于sub Nyquist采样数据的信号稀疏表达式,然后利用SBL算法估计信号频率,同时根据估计结果优化字典,最后反复迭代上述步骤直至计算出的频率值和对应的幅度值趋于稳定。仿真结果校验了方法的有效性。     

Actors of the main activity in large complex centres during the 23 solar cycle maximum

During the maximum of Solar Cycle 23, large active regions had a long life, spanning several solar rotations, and produced large numbers of X-class flares and CMEs, some of them associated to magnetic clouds (MCs). This is the case for the Halloween active regions in 2003. The most geoeffective MC of the cycle (Dst = −457) had its source during the disk passage of one of these active regions (NOAA 10501) on 18 November 2003. Such an activity was presumably due to continuous emerging magnetic flux that was observed during this passage. Moreover, the region exhibited a complex topology with multiple domains of different magnetic helicities. The complexity was observed to reach such unprecedented levels that a detailed multi-wavelength analysis is necessary to precisely identify the solar sources of CMEs and MCs. Magnetic clouds are identified using in situ measurements and interplanetary scintillation (IPS) data. Results from these two different sets of data are also compared.     

高职院校工学结合实现途径研究

工学结合、校企合作是高职院校培养高端技能型人才的根本途径,但高职院校工学结合普遍存在着口号喊得多、实质内容少、短期合作多、长效机制少、学校热情多、企业关注少、校企浅层次合作多、深层次合作少等问题。通过思考促进校企深度融合、工学有效结合的方式,提出了"三位一体,项目育人"的高端技能型人才培养模式。     

主体性教育视野下的商贸类高职院校思想政治教育研究

主体性教育代表着一种全新的教育哲学和教育理念,为"工学结合"人才模式下商贸类高职院校思想政治教育提供新的价值取向和理论基础,构成了"工学结合"人才培养模式下商贸类高职院校思想政治教育的行动逻辑。     

关于大学引进版英语教材的适用性分析

对航空机务工程类专业两个年级进行公共英语教学的纵向问卷调查,对其所使用的两套引进版教材的结构内容等进行分析,基于此,结合学伴用随原则和中国学生的英语学习策略,对这两套教材的适用性进行对比评价,为大学公共英语教材的引进或编写提供经验借鉴。