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Chengdu, China

Cui P.,CAS Chengdu Institute of Mountain Hazards and Environment | Cui P.,Chinese Academy of Sciences | Zeng C.,CAS Chengdu Institute of Mountain Hazards and Environment | Zeng C.,Sichuan Geomatics Center | And 2 more authors.
Earth Surface Processes and Landforms

A miniaturized flume experiment was carried out to measure impact forces of viscous debris flow. The flow depth (7.2-11.2 cm), velocity (2.4-5.2 m/s) and impact force were recorded during the experiment. The impact process of debris flow can be divided into three phases by analyzing the variation of impact signals and flow regime. The three phases are the sudden strong impact of the debris flow head, continuous dynamic pressure of the body and slight static pressure of the tail. The variation of impact process is consistent with the change in the flow regime. The head has strong-rapid impact pressure, which is shown as a turbulent-type flow; the body approximates to steady laminar flow. Accordingly, the process of debris flows hitting structures was simplified to a triangle shape, ignoring the pressure of the tail. In order to study the distribution of the debris flow impact force at different depths and variation of the impact process over time, the impact signals of slurry and coarse particles were separated from the original signals using wavelet analysis. The slurry's dynamic pressure signal appears to be a smooth curve, and the peak pressure is 12-34 kPa when the debris flow head hits the sensors, which is about 1.54 ± 0.36 times the continuous dynamic pressure of the debris flow body. The limit of application of the empirical parameter α in the hydraulic formula was also noted. We introduced the power function relationship of α and the Froude number of debris flows, and proposed a universal model for calculating dynamic pressure. The impact pressure of large particles has the characteristic of randomness. The mean frequency of large particles impacting the sensor is 210 ± 50-287 ± 29 times per second, and it is 336 ± 114-490 ± 69 times per second for the debris flow head, which is greater than that in the debris flow body. Peak impact pressure of particles at different flow depths is 40-160 kPa, which is 3.2 ± 1.5 times the impact pressure of the slurry at the bottom of the flow, 3.1 ± 0.9 times the flow in the middle, and 3.3 ± 0.9 times the flow at the surface. The differences in impact frequency indicate that most of the large particles concentrate in the debris flow head, and the number of particles in the debris flow head increases with height. This research supports the study of solid-liquid two phase flow mechanisms, and helps engineering design and risk assessment in debris flow prone areas. © 2015 John Wiley & Sons, Ltd. Source

Zhu Q.,Southwest Jiaotong University | Zhang J.,Southwest Jiaotong University | Miao S.,Southwest Jiaotong University | Cao Z.,Sichuan Geomatics Center
Proceedings of SPIE - The International Society for Optical Engineering

Aiming at the diversity of emergency aerial photogrammetric mission requirements, complex ground and air environmental constraints make the planning mission time-consuming. This paper presents a fast adaptation for the UAV aerial photogrammetric mission planning. First, Building emergency aerial UAVs mission the unified expression of UAVs model and mechanical model of performance parameters in the semantic space make the integrated expression of mission requirements and low altitude environment. Proposed match assessment method which based on resource and mission efficiency. Made the Adaptive match of UAV aerial resources and mission. According to the emergency aerial resource properties, considering complex air-ground environment and mission requirements constraints. Made accurate design of UAV route. Experimental results show, the method scientific and efficient, greatly enhanced the emergency response rate. © 2015 SPIE. Source

Zhang J.,Southwest Jiaotong University | Zhu Q.,Southwest Jiaotong University | Miao S.,Southwest Jiaotong University | Cao Z.,Sichuan Geomatics Center | Weng Q.,Southwest Jiaotong University
Proceedings of SPIE - The International Society for Optical Engineering

Traditional mission scheduling methods are unable to meet the timeliness requirements of emergency surveying. Different size and overlaps of different missions lead to inefficient scheduling and poor mission returns. Especially for UAVs, based on their agile and flexible ability, the scheduling result becomes diversiform; as affected by environment and unmanned aerial vehicle performance, different scheduling will lead to different time costs and mission payoffs. An effective scheduling solution is to arrange the UAVs reasonably to complete as many as missions possible with better quality and satisfaction of different demands. This paper proposes a method for mission decomposition or aggregation to generate a mission unit for specific UAVs based on the spatio-temporal constraints of different missions and UAV observation ability demands. In this way, the problems of lack or redundancy of resource scheduling, which can be caused by mission overload, various information demands and spatial overlapping will be effectively reduced. Furthermore, the global efficiency evaluation function is built by considering typical scheduling objectives, such as mission returns, priority and load balancing of resources. Then, an improved ant colony algorithm is designed to acquire an optimal scheduling scheme and the dynamic adjustment strategy is employed. Finally, the correctness and validity are demonstrated by the simulation experiment. © 2015 SPIE. Source

Wang J.,LIAONING Technical University | Cao Z.,Sichuan Geomatics Center | Zhu H.,LIAONING Technical University | Li M.,National Quality Inspection and Testing Center for Surveying and Mapping Products
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

A new straight line matching method for aerial images is proposed in this paper. Compared to previous works, similarity constraints combining radiometric information in image and geometry attributes in object plane are employed in these methods. Firstly, initial candidate lines and the elevation values of lines projection plane are determined by corresponding points in neighborhoods of reference lines. Secondly, project reference line and candidate lines back forward onto the plane, and then similarity measure constraints are enforced to reduce the number of candidates and to determine the finial corresponding lines in a hierarchical way. Thirdly, "one-To-many" and "many-To-one" matching results are transformed into "one-To-one" by merging many lines into the new one, and the errors are eliminated simultaneously. Finally, endpoints of corresponding lines are detected by line expansion process combing with "image-object-image" mapping mode. Experimental results show that the proposed algorithm can be able to obtain reliable line matching results for aerial images. Source

Zhu Q.,Wuhan University | Zhu Q.,Southwest Jiaotong University | Cao Z.,Wuhan University | Cao Z.,Sichuan Geomatics Center | And 4 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University

Natural hazards and disasters in China have increased in magnitude and frequency in recent years as consequences of the fast urbanization promotion and global climate change, which has greatly threatened to the sustainable development of social economy. The widespread devastation, economic damages and loss of human lives, caused by numerous forms of natural emergency situations, are becoming more serious. The emergency surveying and mapping service system (ESMSS), which is able to make practical contributions to planning and operation of civil protection and disaster reduction, is urgently needed. The paper probes into some key techniques involved in the construction of the ESMSS at first. Taking applications in "4·20" Lushan earthquake as an example, the article deeply analyses the problems in data acquisition, transmission, processing, distribution, sharing of the current ESMSSs and their working mechanism. Then, the construction method of the proposed task-driven ESMSS is presented in details. Finally, the key techniques including focused service mechanism are expounded. Source

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