Synergetic use of SAR and Thermal Infrared data to study the physical properties of the lunar surface

The surface layer of the Moon preserves vital evidences of lunar impact and cratering processes due to the absence of any Aeolian and fluvial erosion processes acting on it. By examining these evidences, which are recorded throughout the evolutionary history of the Moon, several basic aspects of lunar science can be understood, and this has direct relevance to the surfaces of other airless bodies within the solar system. In this study, rock abundance data obtained from Thermal Infrared (TIR) observations and radar Circular Polarization Ratio (CPR) data sets obtained from polarimetric SAR observations were correlated at some sample sites on the lunar surface. Preliminary results yielded qualitative and quantitative estimates for surface rock abundances. Except at distal ejecta deposits of young, bright craters a general correlation was observed between the two datasets. Mixed results were observed from the impact melt flows where the situation is complex due to the possible subsurface-volume and volume-subsurface interactions of the radar waves. But the flow features were clearly separated from the interior and ejecta regions of their parent craters in terms of CPR and rock abundances. The extent and distributions of pyroclastic deposits and dark haloed regions could not be distinctly identified at the resolution of datasets utilized. Near Gerasimovich D crater, the Diviner Radiometer has provided the first TIR observations of a newly discovered impact melt flow which was not visible in the optical imagery. This facilitated the first ever quantitative comparisons of the radar CPR and rock abundance values near such a region. Also, significant differences in spatial patterns between the radar and rock concentration data sets were observed, owing to the differences in the sensitivity of the two observations.     

基于条件生成对抗网络的HDR图像生成方法

高动态范围（HDR）图像相比低动态范围（LDR）图像有更宽的色域和更高的亮度范围,更符合人眼视觉效果,但由于目前的图像采集设备大都是LDR设备,导致HDR图像资源匮乏,解决该问题的一种有效途径是通过逆色调映射将LDR图像映射为HDR图像。提出了一种基于条件生成对抗网络（CGAN）的逆色调映射算法,以重建HDR图像。为此,设计了基于多分支的生成对抗网络与基于鉴别块的鉴别网络,并利用CGAN的数据生成能力和特征提取能力,将单张LDR图像从BT.709色域映射到对应的BT.2020色域。实验结果表明:与现有方法相比,所提出的网络能够获得更高的客观与主观质量,特别是针对低色域中的模糊区域,所提方法能够重建出更清晰的纹理与细节。      

Hierarchical path computation approach for large graphs

Time is a critical factor in several path planning problems such as flood emergency rescue operations, escape planning from fires and chemical warfare agents dispersed in large buildings, evacuation from urban areas during natural disasters such as earthquakes, and military personnel movement. We propose a hierarchical path planning algorithm (HIPLA) for real time path planning problems where the computational time is of critical significance. The main idea of HIPLA is to significantly reduce the search space for path computation by searching in a high-level abstraction graph, whose nodes are associated with precomputed risk estimates. The cumulative risk associated with all nodes along a path determines the quality of a path. We present a detailed experimental analysis of HIPLA by comparing it with two well-known approaches viz., shortest path algorithm (SPAH) [1] and Dijkstra's algorithm with pruning [2] for large node-weighted graphs.     

On the line ratio diagnostics for NeV, MgV, SiVII and MgVII solar ions

We present NeV/MgV and MgVII/SiVII theoretical line intensity ratios as a function of electron density and temperature for physical conditions within the solar chromosphere-corona transition region. The electron pressure within the emission regions has been assumed to be a constant parameter. These line intensity ratios in addition could be useful for estimating relative element abundances Ne/Mg and Mg/Si. Line intensities of these ions have been computed using a model solar atmosphere and these have been compared with the available observed values for the quiet -Sun conditions. The analysis suggests the need for observations at higher spectral resolution. The successful launch of the SOHO satellite recently should provide such spectra.     

基于深度学习的航空发动机不平衡故障部位识别

针对基于机匣测点的航空发动机不平衡故障部位识别问题,提出了基于深度卷积神经网络的航空发动机不平衡故障部位诊断方法。针对某典型双转子航空发动机,建立整机耦合动力学模型,并利用数值积分算法实现不平衡故障数值仿真;在从发动机压气机端到涡轮端的高、低压转子上选择4个不平衡故障部位作为诊断对象,通过仿真分析得到发动机典型转速下的转子不同部位不平衡故障的仿真样本;计算4个机匣测点信号的规范化频谱,通过对大量仿真数据的处理得到反映不同不平衡故障部位的故障样本集;利用仿真得到的大量不平衡故障样本,训练深度卷积神经网络,利用深度卷积神经网络的优良特征学习能力实现航空发动机不平衡故障的不同部位进行识别,数值试验结果表明该方法对航空发动机不平衡故障部位的识别准确率达到95%。     

Temporally staggered sensors in multi-sensor target tracking systems

For a multi-sensor target tracking system, the effects of temporally staggered sensors on system performance are investigated and compared with those of synchronous sensors. To capture system performance over time, a new metric, the average estimation error variance (AEV), is proposed. For a system that has N sensors with equal measurement noise variance, numerical results show that the optimal staggering pattern is to use N uniformly staggered sensors. We have also shown analytically that the AEV of the system with N uniformly staggered sensors is always smaller than that of the system with N synchronous sensors. For sensors with different measurement noise variances, the optimal staggering pattern can be found numerically. Practical guidelines on selecting the optimal staggering pattern have been presented for different target tracking scenarios. Due to its simplicity, uniform staggering can be used as an alternative scheme with relatively small performance degradation.     

An analytical model of prominence dynamics

Solar prominences are magnetic structures incarcerating cool and dense gas in an otherwise hot solar corona. Prominences can be categorized as quiescent and active. Their origin and the presence of cool gas ($～{10}^4$?K) within the hot ($～{10}^6\text{K}$) solar corona remains poorly understood. The structure and dynamics of solar prominences was investigated in a large number of observational and theoretical (both analytical and numerical) studies. In this paper, an analytic model of quiescent solar prominence is developed and used to demonstrate that the prominence velocity increases exponentially, which means that some gas falls downward towards the solar surface, and that Alfvén waves are naturally present in the solar prominences. These theoretical predictions are consistent with the current observational data of solar quiescent prominences.     

Preliminary results of a meteorological payload being developed by IITM

A meteorological rocket payload developed at the Indian Institute of Tropical Meteorology (IITM) using thermistor as a temperature sensor was flight tested on RH-200 rocket at Thumba (08° 32'N, 76° 52'E), India, during February/April 1982 on four occasions. The corrected data obtained with this payload are compared with Russian rocket, M-100, data. The temperature profile obtained with IITM payload is warmer above 45-km, as compared with M-100 temperature profile, on all occasions. Meridional and zonal winds also agree up to 45-km level. Temperature records show a wave pattern varying in amplitude and frequency in the 20 to 45-km range.     

Marangoni effects under electric fields

An electric field when applied across liquid-liquid interface was found to cause, due to different susceptibilities of the two phases, what the authors would term as Marangoni “type” of instabilities, that resulted in the generation of bubbles/drops and caused the movement of the interface countering gravity. Thus “mixing” of the two phases would occur and in systems involving mass transfer, enhanced rates of transfer could be expected.Equations for the bubble formation involving parameters such as electrostatic pressure, surface tension, gravity force have been derived.In the case of non-gravitational or weak-gravitational fields such as obtainable in space, the separation of two liquids one below the other, as obtaining on the earth, exhibiting an interface may well nearly be impossible. Under such conditions recourse may have to be taken to super-imposition of other fields as a tool for obtaining the necessary contacting/separation. The dynamics of bubble formation etc. under these contexts are theoretically analysed.