Delineation of possible influence of solar variability and galactic cosmic rays on terrestrial climate parameters

The present paper has investigated the associations of solar activity (SA), represented by total solar irradiance (TSI), galactic cosmic rays (GCR) and terrestrial climate parameters in particular the global cloudiness and global surface temperature. To that end, we have analysed thirty five years (1983–2018) data of these parameters and have applied the Granger-causality test in order to assess whether there is any potential predictability power of one indicator to the other. The correlations among the involved parameters are tested using Vector Auto Regression (VAR) model and variance decomposition method. As a result of the above analysis, we have found that the TSI is an important factor and has contributed about 8.77 ± 0.42% in the cosmic ray intensity variations. In case of cloud cover variations, the other three parameters (TSI, cosmic ray and global surface temperature) have played a significant role. Further, the TSI changes have contributed 1.68 ± 0.03% fluctuations in the variance of the cloud cover while the cosmic ray intensity and global surface temperature have contributed about 4.89 ± 0.08% and 10.87 ± 1.41% respectively. In case of the global surface temperature anomaly both TSI and cloud covers have contributed about 5.07 ± 0.47% and 14.42 ± 2.13% fluctuations respectively. Additionally, we have also assessed the impact of internal climate oscillations like multivariate ENSO index (MEI), north Atlantic oscillations (NAO) and quasi biennial oscillations (QBO) on cloud cover variations. The contribution of these internal oscillations e.g. ENSO, NAO and QBO in cloud cover variation were reported as 7.48 ± 1.02%, 5.51 ± 0.16% and 1.36 ± 0.43% respectively.     

Non-linear methods in remotely sensed multispectral data classification

The aim of this research is to develop an effective approach being able to deal with the stochastic nature of remote sensing data. In order to achieve this objective it is necessary to structure the methodological knowledge in the area of data mining and reveal the most suitable methods for the prediction and decision support based on large amounts of multispectral data. The idea is to establish a framework by decomposing the task into functionality objectives and to allow the end-user to experiment with a set of classification methods and select the best methods for specific applications. As a first step, we compare our results from Bayesian classification based on non-parametric probability density estimates of the data to the results obtained from other classification methods. Tree scenarios are considered, making use of a small benchmark dataset, a larger dataset from Corine land cover project for Bulgaria and analyzing different features and feature selection methods. We show that the theoretically optimal Bayesian classification can also achieve optimal classification in practice and provides a realistic interpretation of the world where land cover classes intergrade gradually.     

直升机空中回收和投放货物技术发展综述

针对直升机空中回收和投放货物技术的发展进行了探讨.首先按照直升机空中回收系统发展的三个阶段,简要介绍了三代系统的特点、工作过程及典型应用实例；其次对无人直升机投放技术进行研究综述,介绍了美国K - Max直升机实现无人货运投放的技术及其应用.     

高温热源羽流流场及伴生粉尘控制特性

采用CFD数值模拟软件对高温热源上部接受罩的羽流温度场和速度场进行分析,比较不同工况下上部伞形接受罩对高温烟气的控制特性,同时提出合理设置排风罩位置和风量的措施。     

某型无人机伞降回收过程分析及回收策略研究

在分析某型无人机回收系统组成和工作程序的基础上,研究了某型无人机伞降回收过程的的运动特点,建立了某型无人机回收各个阶段的动力模型,通过数值仿真方法得到了回收各个阶段的运动特征,分析了回收过程的运动轨迹和落点误差的影响因素,在此基础上建立了合理的回收策略。     

舷外有源诱饵降落伞载荷运动仿真

对火箭发射降落伞悬降方式的舷外有源诱饵的载荷运动进行了分析。在此分析的基础上,通过在2个正交铅垂平面上的分解,建立了载荷运动的数学模型,描述了在2个正交铅垂平面上降落伞—载荷连线相对于铅垂线的角运动。利用Simulink进行了单个铅垂平面上的角运动的仿真和2个正交铅垂平面上的角运动的综合仿真。     

Development and testing of a statistical texture model for land cover classification of the Black Sea region with MODIS imagery

A statistical model is proposed for analysis of the texture of land cover types for global and regional land cover classification by using texture features extracted by multiresolution image analysis techniques. It consists of four novel indices representing second-order texture, which are calculated after wavelet decomposition of an image and after texture extraction by a new approach that makes use of a four-pixel texture unit. The model was applied to four satellite images of the Black Sea region, obtained by Terra/MODIS and Aqua/MODIS at different spatial resolution. In single texture classification experiments, we used 15 subimages (50 × 50 pixels) of the selected classes of land covers that are present in the satellite images studied. These subimages were subjected to one-level and two-level decompositions by using orthonormal spline and Gabor-like spline wavelets. The texture indices were calculated and used as feature vectors in the supervised classification system with neural networks. The testing of the model was based on the use of two kinds of widely accepted statistical texture quantities: five texture features determined by the co-occurrence matrix (angular second moment, contrast, correlation, inverse difference moment, entropy), and four statistical texture features determined after the wavelet transformation (mean, standard deviation, energy, entropy). The supervised neural network classification was performed and the discrimination ability of the proposed texture indices was found comparable with that for the sets of five GLCM texture features and four wavelet-based texture features. The results obtained from the neural network classifier showed that the proposed texture model yielded an accuracy of 92.86% on average after orthonormal wavelet decomposition and 100% after Gabor-like wavelet decomposition for texture classification of the examined land cover types on satellite images.     

大型伞绳帆和抽打现象连续模型及验证

文章主要推导了可用于描述大型降落伞绳帆和抽打现象的一般绳索三维动力学连续模型,及弦坐标系下可用于求解绳帆现象的两点边值问题(BVP)模型,并采用某型号大型降落伞的空投录像和杆件算例对模型进行验证对比,说明了模型的正确性,采用这一连续模型能够更直观地对大型伞的绳帆和抽打现象进行定性和定量分析。     

复合材料易碎盖薄弱区结构设计分析

 针对复合材料易碎盖关键部位薄弱区结构进行设计,并采用数值模拟方法对其力学性能进行了研究。首先对易碎盖整体进行数值模拟,为薄弱区结构局部模型分析提供了边界条件与载荷。其次通过局部数值模拟结果结合相应的强度准则,预测了相应的易碎盖冲破压力,并通过对易碎盖实验件进行冲破实验验证了设计方案与理论方法的准确性。最后讨论了薄弱区参数对易碎盖冲破压力的影响。     

半球形伞流固耦合工程算法

降落伞流固耦合模拟非常难以实现,而一些工程设计任务要求迅速高效地完成.为了适应该要求,针对稳定下降阶段的半球形伞,提出了一种流固耦合工程算法.以轴对称伞形为伞衣初始形状,通过流场模拟得到结构模拟所需的伞衣压力系数分布,通过结构模拟得到新的伞衣外形,如此循环,直到伞衣中幅线和伞绳外形趋于稳定为止.结果表明,伞衣外形能迅速收敛,该方法能满足工程设计要求.