晚更新世以来东昆仑山区黄土沉积及其气候意义

分布于东昆仑山北坡、发育于距今约24kaB.P.以来的高海拔黄土提供了东昆仑山区晚更新世以来气候变化的完整记录。根据黄土岩性、粒度、重矿物及其地磁分析,结合本区内的古冻土研究结果,东昆仑山约24kaB.P.以来经历了晚更新世末寒冷期(24～10.7kaB.P.);早全新世转暖期(10.7～8.8kaB.P.);中全新世暖湿期(8.8～6.0kaB.P.);中全新世暖干期(6.0～4.5kaB.P.);全新世后期(4.5kaB.P.)以来等气候演化阶段。     

自由能密度上限及毫秒级射电尖峰的“饱和”机制

本文首先介绍了热力学自由能上限的普遍公式及其推导思想,然后应用于非热电子束的具体形式,从而估计太阳射电活动中的毫秒级尖峰辐射的“饱和”能量;在此基础上,进一步为饱和时间问题作一般性的讨论;最后,在把尖峰“饱和”的几种机制进行了比较之后提出:由于尖峰能量远未达到非线性饱和的水平,因此,由某种外部因素(例如加速机制等)所导致的高能电子束的非均匀性可能是一种较为合理的模型。     

Timing analysis of the black hole candidate EXO 1846-031 with insight-HXMT monitoring

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations ...     

空间视角下城乡物流网络的内涵、构成要素与研究框架

地理学视角的物流网络研究已成为物流科学领域的热点方向。从地理学的空间视角出发,在明确城乡物流网络理论来源和相关概念的基础上,对城乡物流网络的内涵、构成及研究框架进行梳理。基于研究,首先给出了城乡物流网络的定义,认为城乡物流网络的本质是旧的城市物流网络和乡村物流网络在空间上的延伸、衔接和提效。其次,从空间视角将城乡物流网络分解为节点、连线和域面3要素,指出网络各要素均出现了功能强化和更新,如节点的管理、衔接和经济社会功能强化;连线的联结功能和平衡功能出现,域面的协同组织、动态调整功能突出。最后,遵循地理学“格局-过程-机理-决策”的科学逻辑,提出“数据采集与融合、要素映射与解析、时空比较与分析、机理探究与优化”4个模块的城乡物流网络分析框架,为深刻揭示城乡物流网络结构及其演化机理提供基础。进一步指出未来应探讨城乡物流节点、连线、域面及网络的地区类型、区域适宜性及要素间相互作用机制,提炼适应不同区域、能有效提升要素流通效应的多尺度空间组织模式,加强对城乡要素流通系统的科学认知,科学支撑城乡地域融合发展实践。     

Study on Sampling Rule and Simplification of LiDAR Point Cloud Based on Terrain Complexity

It is difficult to obtain digital elevation model (DEM) in the mountainous regions. As an emerging technology, Light Detection and Ranging (LiDAR) is an enabling technology. However, the amount of points obtained by LiDAR is huge. When processing LiDAR point cloud, huge data will lead to a rapid decline in data processing speed, so it is necessary to thin LiDAR point cloud. In this paper, a new terrain sampling rule had been built based on the integrated terrain complexity, and then based on the rule a LiDAR point cloud simplification method, which was referred as to TCthin, had been proposed. The TCthin method was evaluated by experiments in which XUthin and Lasthin were selected as the TCthin’s comparative methods. The TCthin’s simplification degree was estimated by the simplification rate value, and the TCthin’s simplification quality was evaluated by Root Mean Square Deviation. The experimental results show that the TCthin method can thin LiDAR point cloud effectively and improve the simplification quality, and at 5 m, 10 m, 30 m scale levels, the TCthin method has a good applicability in the areas with different terrain complexity. This study has theoretical and practical value in sampling theory, thinning LiDAR point cloud, building high-precision DEM and so on.     

Dim and Small Target Detection Based on Characteristic Spectrum

Dim and small target detection is one of the most challenging issues based on space-based detector. Original space-based detector only uses infrared bands, and the target information is limited in one-band image, so that detection error rate is high. In order to increase the target information, we suppose spectral imaging technology can be applied to the space-based detection system. Use bands of stronger radiation of targets than that of background as detection bands theoretically; the detection bands also can be called as the characteristic bands of targets. On these bases, the paper proposes methods of fuzzy fusion and fusion segmentation to achieve the target detection. Fusion is a combination of images from the characteristic bands, which can eliminate background, restrain noise, and enhance the target. Threshold segmentation and fuzzy algorithm assisted fusion algorithm to complete the final detection. In the simulation experiment, missile plume is considered as the detection target, atmosphere, cloud and jet plume is considered as the detection background, and the advantages of the characteristic spectrum detection and the proposed algorithm are verified from SNR, SCR, ROC curve, and time.     

PMODTRAN: a parallel implementation based on MODTRAN for massive remote sensing data processing

MODerate resolution atmospheric TRANsmission (MODTRAN) is a commercial remote sensing (RS) software package that has been widely used to simulate radiative transfer of electromagnetic radiation through the Earth's atmosphere and the radiation observed by a remote sensor. However, when very large RS datasets must be processed in simulation applications at a global scale, it is extremely time-consuming to operate MODTRAN on a modern workstation. Under this circumstance, the use of parallel cluster computing to speed up the process becomes vital to this time-consuming task. This paper presents PMODTRAN, an implementation of a parallel task-scheduling algorithm based on MODTRAN. PMODTRAN was able to reduce the processing time of the test cases used here from over 4.4 months on a workstation to less than a week on a local computer cluster. In addition, PMODTRAN can distribute tasks with different levels of granularity and has some extra features, such as dynamic load balancing and parameter checking.     

Selection and quality assessment of Landsat data for the North American forest dynamics forest history maps of the US

Using the NASA Earth Exchange platform, the North American Forest Dynamics (NAFD) project mapped forest history wall-to-wall, annually for the contiguous US (1986–2010) using the Vegetation Change Tracker algorithm. As with any effort to identify real changes in remotely sensed time-series, data gaps, shifts in seasonality, misregistration, inconsistent radiometry and cloud contamination can be sources of error. We discuss the NAFD image selection and processing stream (NISPS) that was designed to minimize these sources of error. The NISPS image quality assessments highlighted issues with the Landsat archive and metadata including inadequate georegistration, unreliability of the pre-2009 L5 cloud cover assessments algorithm, missing growing-season imagery and paucity of clear views. Assessment maps of Landsat 5–7 image quantities and qualities are presented that offer novel perspectives on the growing-season archive considered for this study. Over 150,000+ Landsat images were considered for the NAFD project. Optimally, one high quality cloud-free image in each year or a total of 12,152 images would be used. However, to accommodate data gaps and cloud/shadow contamination 23,338 images were needed. In 220 specific path-row image years no acceptable images were found resulting in data gaps in the annual national map products.     

基于DBN的车载激光点云路侧多目标提取

提出一种基于深度信念网络（DBN）的车载激光点云路侧多目标提取方法。首先通过预处理对原始数据进行分段,并将地面和建筑物点云与路侧目标进行分离;然后利用连通分支聚类分析算法进行路侧点云聚类,并采用基于体素的归一化分割方法分割重叠点云,从而生成独立目标点云;在此基础上,生成基于多方向目标对象的二值图像并展开成二值向量作为独立目标点云的描述特征;最后构建并训练DBN,利用训练好的DBN提取行道树、车辆及杆状目标等3类路侧目标。试验采用两份不同城市道路场景的点云数据,行道树、车辆及杆状目标提取结果的准确率分别达97.31%、97.79%、92.78%,召回率分别达98.30%、98.75%和96.77%,精度分别达95.70%、93.81%和90.00%,F1值分别达97.80%、96.81%和94.73%。试验结果验证了本文的有效性。     

The Characteristics of Storm Wave Behavior and Its Effect on Cage Culture Using the ADCIRC+SWAN Model in Houshui Bay,China

The current storm wave hazard assessment tends to rely on a statistical method using wave models and fewer historical data which do not consider the effects of tidal and storm surge.In this paper,the wave-current coupled model ADCIRC+SWAN was used to hindcast storm events in the last 30 years.We simulated storm wave on the basis of a large set of historical storms in the North-West Pacific Basin between 1985 and 2015 in Houshui Bay using the wave-current coupled model ADCIRC+SWAN to obtain the storm wave level maps.The results were used for the statistical analysis of the maximum significant wave heights in Houshui Bay and the behavior of wave associated with storm track.Comparisons made between observations and simulated results during typhoon Rammasun(2014)indicate agreement.In addition,results demonstrate that significant wave height in Houshui Bay is dominated by the storm wind velocity and the storm track.Two groups of synthetic storm tracks were designed to further investigate the worst case of typhoon scenarios.The storm wave analysis method developed for the Houshui Bay is significant in assisting government's decision-making in rational planning of deep sea net-cage culture.The method can be applied to other bays in the Hainan Island as well.