粒子加速器中高精度丝线绝对位置测量技术研究   总被引：1，自引：0，他引：1  

梁静  罗明成  王铜  董岚  罗涛  柯志勇  王小龙 《测绘通报》2019,(9):44-50

粒子加速器中采用振动线技术进行共架单元上多块磁铁的高精度预准直，需要将振动线代表的磁中心引出进行共架单元之间的相对准直。为了获取以振动线为代表的丝线高精度空间绝对位置，本文对采用近景摄影测量技术进行点、线位置求解的方法进行了研究。利用单相机多站位的方法进行拍摄，通过标定板提供的高精度控制点坐标，采用自标定光束法平差对相机进行标定，并提出将空间直线离散成空间2点进行直线整体精确求解。对标定板上由2点组成的模拟直线进行测量验证，并与标定板提供的理论值进行对比，结果显示空间直线位置获取精度优于5 μm。这表明了本文理论和方法的正确性，为进一步研究丝线高精度空间绝对位置测量打下了基础。  相似文献   

基于投影变换的线阵旋转扫描相机标定方法     

苏琳  巫兆聪  闫钊  王鹏 《测绘通报》2019,(4):96-98,102

针对线阵旋转扫描相机标定数据难以获取及模型解算不稳定的问题，提出了一种基于投影变换的线阵旋转扫描相机标定方法。首先构建了一种新的线阵旋转扫描相机成像模型，该模型可以根据相机旋转平台参数、线阵旋转扫描相机成像平面与其切平面的位置关系将旋转扫描图像投影为框幅式图像；然后根据构建出的成像模型，采用直接线性变换法和非线性优化方法进行相机标定和参数优化。试验结果表明，此方法简单易行，具有较高的精度。  相似文献   

多视点相机联合标定及改进的PMVS重建方法     

赵漫丹  吴高昌  闫石  孙国鹏  郝向阳 《测绘科学技术学报》2017,34(4)

提出一种能够在强约束条件下快速进行相机标定的方法。通过相机间6个相互独立的约束,充分利用系统的几何条件,确定相邻立体相机的固有关系;再以共线方程为基础推导强约束条件下的平差模型,并应用于自检校光束法平差,从而实现多相机系统的快速标定;最后利用改进的PMVS三维重建方法开展标定后系统的人体三维重建。实验表明,通过加入强约束条件,增加平差的多余观测数,提高了标定精度和鲁棒性,对三维重建的精度亦有较大提高,并且该方法可推广到多个相机组成的多相机立体量测系统的标定中。  相似文献   

Assessing potential land suitable for surface irrigation using groundwater in Ethiopia     

《Applied geography (Sevenoaks, England)》2017

Although Ethiopia has abundant land for irrigation, only a fraction of its potential land is being utilized. This study evaluates suitability of lands for irrigation using groundwater in Ethiopia using GIS-based Multi-Criteria Evaluation (MCE) techniques in order to enhance the country's agricultural industry. Key factors that significantly affect irrigation suitability evaluated in this study include physical land features (land use, soil, and slope), climate (rainfall and evapotranspiration), and market access (proximity to roads and access to market). These factors were weighted using a pair-wise comparison matrix, then reclassified and overlaid to identify suitable areas for groundwater irrigation using a 1-km grid. Groundwater data from the British Geological Survey were used to estimate the groundwater potential, which indicates the corresponding irrigation potential for major crops. Results indicated that more than 6 million ha of land are suitable for irrigation in Ethiopia. A large portion of the irrigable land is located in the Abbay, Rift Valley, Omo Ghibe, and Awash River basins. These basins have access to shallow groundwater (i.e., depth of groundwater less than 20 m from the surface) making it easier to extract. The comparison between available groundwater and total crop water requirements indicate that groundwater alone may not be sufficient to supply all suitable land. The study estimates that only 8% of the suitable land can be irrigated with the available shallow groundwater. However, groundwater is a viable option for supplementing surface water resources for irrigation in several basins in the country.  相似文献   

Biodiversity Assessment of Mammal and Bird Species from Camera Trap Data in Yanchiwan National Nature Reserve,Gansu Province,China     

ZHANG Chengcheng  WANG Jun  Justine Shanti ALEXANDER  DOU Zhigang  WU Liji  DONG Wantao  Dabuxilite  YANG Jucai  SHI Kun 《资源与生态学报(英文版)》2018,9(5):566-574

Camera traps serve as an important tool for monitoring species diversity. We used data from camera traps set for capturing snow leopards (Panthera uncia) in the Yanchiwan National Nature Reserve, Gansu Province, China, to assess species richness with respect to mammal and birds species. We also assessed survey efficiency for species detection, and conducted an initial analysis of species interactions. The survey effort of 10, 171 camera workdays yielded 2, 868 suitable animal image events involving 17 mammal and 20 bird species. Among these, the dhole (Cuon alpinus) is considered to be Endangered, the snow leopard and white-lipped deer (Cervus albirostris) Vulnerable, and the Pallas’s cat (Feli smanul), mountain weasel (Mustela altaica), Himalayan griffon (Gyps himalayensis) and cinereous vulture (Aegypius monachus) Near Threatened under the IUCN red list. Fourteen species were also listed as key protected wild animals according to China national standards. Both the rarefaction curves and richness estimators suggested our sampling for mammal and pheasant species is sufficient, while more survey efforts are still needed to detect other bird species. With a focus on the dominant species Eurasian lynx (Lynx lynx), occupancy models were used to estimate site use and detection probability for selected species, and to investigate predator-prey relationships between lynx on the one hand and woolly hare (Lepus oiostolus), pika (Ochotona spp.) and Tibetan partridge (Perdix hodgsoniae) on the other. We give recommendations on how to increase efficiency in camera-based species inventory and biodiversity monitoring.  相似文献   

Probing fault zone heterogeneity on the Nojima fault: Constraints from zircon fission-track analysis of borehole samples   总被引：2，自引：0，他引：2  

Takahiro Tagami  Masaki Murakami 《Tectonophysics》2007,443(3-4):139

Fission-track (FT) thermochronologic analysis was performed on zircon separates from rocks in and around the Nojima fault, which was activated during the 1995 Kobe earthquake. Samples were collected from the University Group 500 m (UG-500) borehole and nearby outcrops. FT lengths in zircons from localities > 25 m away from the fault plane as well as one 0.1 m away from the fault in the footwall are characterized by concordant mean values of  10–11 μm and unimodal distributions with negative skewness, which showed no signs of appreciable reduction in FT length. In contrast, those adjacent (< 3 m) to the fault at depths on the hanging wall side showed significantly reduced mean track lengths of  6–8 μm and distributions having a peak around 6–7 μm with rather positive skewness. The former pattern is interpreted to reflect cooling through the zircon partial annealing zone (ZPAZ), without later, partial thermal overprints. The latter indicates substantial track shortening due probably to secondary heating by a thermal event(s) that locally perturbed the geothermal structure. Modeled zircon FT length and age data of partially annealed samples from the UG-500 borehole revealed a cooling episode in the ZPAZ that started at  4 Ma within  3 m from the fault plane, whereas those from the Geological Survey of Japan 750 m borehole record cooling started at  31–38 Ma within  25 m from the fault. On the basis of one-dimensional heat conduction modeling as well as the consistency between the degree of FT annealing and the degree of deformation/alteration of borehole rocks, these cooling ages in both boreholes are interpreted as consequences of ancient thermal overprints by heat transfer or dispersion via fluids in the fault zone. Together with the zircon FT data of a pseudotachylyte layer recently analyzed, it is suggested that the present Nojima fault system was reactivated in the Middle Quaternary from an ancient fault initiated at  56 Ma at mid-crustal depths. Also shown is a temporal/spatial variation in terms of the thermal anomalies recorded in the fault rocks, implying heterogeneity of hot fluid flows in the fault zone.  相似文献   

Photogrammetric Capabilities of the Kodak DC40, DCS420 and DCS460 Digital Cameras     

A. Ahmad  & J. H. Chandler 《The Photogrammetric Record》1999,16(94):601-615

The aim of this study is to assess the impact of sensor size and resolution of different digital camera sensors upon the accuracy and precision of three dimensional data derived by photogrammetry. Kodak DC40, DCS420 and DCS460 digital cameras were used to produce digital images of retroreflective targets in a 4 m three dimensional test field. The image locations of the targeted points were automatically measured using an off the shelf image processing software package. Two different sub-pixel measurement approaches were examined: centre of gravity and weighted mean. From the automated sub-pixel measurement of the targeted points, results indicate that the high resolution DCS460 camera produces optimum results using either the weighted mean or centre of gravity approaches. Although this was perhaps expected, the far lower resolution DC40 camera performed better than was originally anticipated, suggesting potential for the cheaper DC40 for many applications.  相似文献   

SHORT COMMUNICATION­­A field experiment of cusp formation on a coarse clastic beach using a suspended video‐camera system     

Tsuguo Sunamura  Hisashi Aoki 《地球表面变化过程与地形》2000,25(3):329-333

Cusp formation was continuously monitored on a manually flattened, plane section of a coarse clastic, microtidal, pocket beach on the Pacific coast of Japan using a CCD camera suspended in the air. Vertical video pictures enabled the examination of the temporal change in foreshore morphologies and swash pattern. Boulders on the beach face appeared to have triggered the formation of beach cusps, which gradually and successively grew up alongshore. In 2·5 h, two well defined beach cusps had developed with a spacing of 2·2 and 2·5 m, respectively. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

井下地震计的P波接收函数正演计算及其稳定性研究——以首都圈地区为例          下载免费PDF全文

郑德高  倪四道  杨卓欣  刘志 《地球物理学报》2018,61(10):3964-3979

井下地震计波形记录的P波垂向分量存在频谱极小（spectrum null）现象,导致接收函数的结果不稳定.本文以首都圈地区为例,基于平面波入射的传播矩阵理论,发展了用于计算井下地震计的接收函数正演方法.在此基础上,分析了井下地震计波形垂向分量频谱极小现象,研究其对接收函数稳定性的影响.结果表明,井下地震计波形记录垂向分量的频谱极小开始出现的频率和地震计的埋深相关.该现象可造成反卷积提取的接收函数不稳定,且不稳定情况出现在频谱极小附近的频段,可通过选择合适的高斯因子压制其对接收函数的影响.  相似文献   

Feasibility of borehole ambient noise interferometry for permanent reservoir monitoring          下载免费PDF全文

M. Behm 《Geophysical Prospecting》2017,65(2):563-580

The analysis of seismic ambient noise acquired during temporary or permanent microseismic monitoring campaigns (e.g., improved/enhanced oil recovery monitoring, surveillance of induced seismicity) is potentially well suited for time‐lapse studies based on seismic interferometry. No additional data acquisition required, ambient noise processing can be automatized to a high degree, and seismic interferometry is very sensitive to small medium changes. Thus there is an opportunity for detection and monitoring of velocity variations in a reservoir at negligible additional cost and effort. Data and results are presented from an ambient noise interferometry study applied to two wells in a producing oil field in Romania. Borehole microseismic monitoring on three component geophones was performed for four weeks, concurrent with a water‐flooding phase for improved oil recovery from a reservoir in ca. 1 km depth. Both low‐frequency (2 Hz–50 Hz) P‐ and S‐waves propagating through the vertical borehole arrays were reconstructed from ambient noise by the virtual source method. The obtained interferograms clearly indicate an origin of the ambient seismic energy from above the arrays, thus suggesting surface activities as sources. It is shown that ambient noise from time periods as short as 30 seconds is sufficient to obtain robust interferograms. Sonic log data confirm that the vertical and horizontal components comprise first arrivals of P‐wave and S‐waves, respectively. The consistency and high quality of the interferograms throughout the entire observation period further indicate that the high‐frequency part (up to 100 Hz) represents the scattered wave field. The temporal variation of apparent velocities based on first‐arrival times partly correlates with the water injection rate and occurrence of microseismic events. It is concluded that borehole ambient noise interferometry in production settings is a potentially useful method for permanent reservoir monitoring due to its high sensitivity and robustness.  相似文献