不同影像处理系统的空三数据处理比较研究

系统介绍了像素工厂和海拉瓦数字摄影测量系统的空中三角测量特点,并通过实验比较了二者的性能。实验比较发现,基于两个系统的空中三角测量精度基本相同;执行效率方面,当测区数据量较大时,像素工厂更具有整体优势;而在小区域数据处理上,SOCET GXP更具灵活性。当测区影像超过150景时,建议在像素工厂中进行空中三角测量。     

浅谈电视监控系统的防雷保护

1引言电视监控系统在银行、交通、公安等系统中得到广泛应用,监控系统的设备是敏感的电子设备,耐压低,易受雷击,其后果可能会使整个系统瘫痪,并造成难以估计的经济损失和社会影响。电视监控系统的防雷保护是比较复杂的,首先必须明确监控系统遭受雷击损害的主要原因以及雷电可能入侵途径,然后在分析其损坏原因的基础上正确选择和使用监控系统设备的防雷保护装置。2电视监控系统的组成以及遭雷击损坏的途迳2.1电视监控系统电视监控系统(Closed Circait Televisiow,简称CCTV),一般由以下3部分组成:前端部分:主要由黑白(彩色)摄像机、镜头、…     

GIS-based landslide susceptibility mapping using hybrid integration approaches of fractal dimension with index of entropy and support vector machine

The loess area in the northern part of Baoji City, Shaanxi Province, China is a region with frequently landslide occurrences. The main aim of this study is to quantitatively predict the extent of landslides using the index of entropy model(IOE), the support vector machine model(SVM) and two hybrid models namely the F-IOE model and the F-SVM model constructed by fractal dimension. First, a total of 179 landslides were identified and landslide inventory map was produced, with 70%(125) of the landslides which was optimized by 10-fold crossvalidation being used for training purpose and the remaining 30%(54) of landslides being used for validation purpose. Subsequently, slope angle, slope aspect, altitude, rainfall, plan curvature, distance to rivers, land use, distance to roads, distance to faults, normalized difference vegetation index(NDVI), lithology, and profile curvature were considered as landslide conditioning factors and all factor layers were resampled to a uniform resolution. Then the information gain ratio of each conditioning factors was evaluated. Next, the fractal dimension for each conditioning factors was calculated and the training dataset was used to build four landslide susceptibility models. In the end, the receiver operating characteristic(ROC) curves and three statistical indexes involving positive predictive rate(PPR), negative predictive rate(NPR) and accuracy(ACC) were applied to validate and compare the performance of these four models. The results showed that the F-SVM model had the highest PPR, NPR, ACC and AUC values for training and validation datasets, respectively, followed by the F-IOE model.Finally, it is concluded that the F-SVM model performed best in all models, the hybrid model built by fractal dimension has advantages than original model, and can provide reference for local landslide prevention and decision making.     

Effects of rainfall intensity and topography on rill development and rill characteristics on loessial hillslopes in China

Rill development is a major soil erosion process that causes severe soil degradation.This study examined the effects of representative rainfall intensities(50 and 75 mm h-1),slope gradients(10°and 150),and slope lengths(7.5 and 10.0 m)on rill development and rill characteristics on loessial hillslopes in China.Loessial soil was collected from the cropland of Ansai Town,Yan'an City,Shaanxi Province.The soil with 28.3%sand,58.1%silt,and13.6%clay was packed into a soil pan to conduct rainfall simulations in 2012.The results showed that the time of the knickpoint occurrence(5-16 min),the rill headcut extension(9-33 min),and the mean headward erosion rate(1.7-5.o cm min-1)were better representative indicators for reflecting the changes in the rill development than other indicators used in this study.For a quick evaluation of the rill erosion severity,the rill coverage ratio(1%-12%,generallyincreasing with an increase in the rainfall intensity)was better than the other indicators for treatments with different rainfall intensities,and the rill width-depth ratio(1.56-2.27,generally decreasing with an increase in the slope gradient)was better than the other indicators for treatments with different slope gradients.Furthermore,the rill inclination angle(8.2°-19.1°,significantly increasing with an increase in the slope length)and rill density(0.19-1.34 m·m-2,generally increasing with an increase in the slope length)were more suitable for evaluating the rill erosion severity on hillslopes with different slope lengths.Therefore,the representative indicators could reflect the differences in the rill development and rill characteristics under different rainfall and topographic situations.The study greatly improved the evaluation of rill erosion severity and the prediction of the development of rills for loessial hillslopes.     

Primary molecular basis of androgenic gland endocrine sex regulation revealed by transcriptome analysis in Eriocheir sinensis

In crustaceans, the male sexual dif ferentiation and maintenance are specially regulated by androgenic gland(AG). However, little is known about the genes involved in the regulation process.RNA-Seq was performed on AG with ejaculatory duct(AG_ED) and ejaculatory duct(ED) as control in Eriocheir sinensis, one of the most important economic and ?shery crabs with typically sex dimorphism. A total of 925 unigenes were identi?ed as dif ferentially expressed genes(DEGs) and the expression of nine genes randomly selected was con?rmed by qRT-PCR. 667 unigenes were up-regulated in AG_ED, being supposed to be AG preferential genes. Among them, the full length of i nsulin-like androgenic gland factor( IAG) cDNA named as Es-IAG was obtained as a logo gene of AG, which together with the genes i nsulin-like receptor( INR), and s ingle insulin binding domain protein( SIBD), might constitute the sex regulation pathway. Several sex related genes were identi?ed, and their function will have to be investigated. Also,the identi?cation of j uvenile hormone epoxide hydrolase 1( JHEH1), ecdysteroid 22-hydroxylase( DIB) and e cdysone receptor( ECR) preliminarily clari?ed the molecular regulation mechanism of eyestalk-AG-testis axis, which plays important roles in molting and reproduction. The results will enhance our understanding for the molecular basis of the AG involved in male sex regulation in crabs.     

差分层析SAR技术研究现状分析

差分层析SAR是在层析SAR基础上发展起来的一种四维信息反演技术。它不仅实现了对雷达目标的三维分辨能力,同时可以获取目标的形变速率信息,可实现对目标方位-距离-高度-时间四维成像,这对实现城市基础设施动态形变监测、古建筑风险评估、重要工程安全监测等应用具有重要实际意义和价值。本文基于差分层析SAR成像原理,分析了成像处理过程中存在的问题,总结了差分层析SAR成像算法研究现状和特点;最后列举了差分层析SAR技术的主要应用领域,并对其技术发展趋势进行了展望。     

椭球谐和球谐系数之间一个简单的转换关系

本文推导的椭球谐系数和球谐系数相互之间转换关系的核心思想是在ε~2量级下利用Legendre函数的正交性,从球谐系数求解的积分表示出发,将积分中的椭球坐标变量与球坐标变量相互转换,从而得出椭球谐系数与球谐系数之间的转换关系。本文导出的转换关系有以下优点:①对于第二类Legendre函数的计算采用Laurent级数表示,使计算第二类Legendre函数更为简单;②保留了ε~2量级下,导出的转换关系相比文献[2]的形式更简单,满足物理大地测量边值问题线性化的要求;③顾及了余纬和归化余纬的区别。     

国外OTA与传统旅游企业竞合关系研究综述

作为重要的在线营销渠道,OTA一直是传统旅游企业的重要合作伙伴之一。无论是OTA抢夺资源还是传统旅游企业对抗升级,双方之间的竞争趋势愈加明显。由此,相关方面的研究逐步增多。国外研究从OTA与饭店、航空公司等传统旅游企业合作、竞争和竞合平衡三个方面入手,主要围绕OTA与饭店的竞合问题展开。重视实证分析,采用数理统计和模型构建等定量研究方法,针对航空公司和饭店企业,从市场细分、定价、客房分配等角度提出实现双方竞合平衡的方案。建议今后加强对OTA和传统旅游企业合作模式变化的跟踪分析,关注OTA与景区、餐馆等旅游供应商的博弈关系。     

Rift structures and its related unconformities on and adjacent the Dongsha Rise: insights into the nature of the high-velocity layer in the northern South China Sea

Marine Geophysical Research - It is curious that the typical feature of high-velocity layer (HVL) underneath the crust for the magma-rich margin was found in the magma-poor margin of the South...     

Establishment of Numerical Wave Flume Based on the Second-Order Wave-Maker Theory

With growing computational power, the first-order wave-maker theory has become well established and is widely used for numerical wave flumes. However, existing numerical models based on the first-order wave-maker theory lose accuracy as nonlinear effects become prominent. Because spurious harmonic waves and primary waves have different propagation velocities, waves simulated by using the first-order wave-maker theory have an unstable wave profile. In this paper, a numerical wave flume with a piston-type wave-maker based on the second-order wave-maker theory has been established. Dynamic mesh technique was developed. The boundary treatment for irregular wave simulation was specially dealt with. Comparisons of the free-surface elevations using the first-order and second-order wave-maker theory prove that second-order wave-maker theory can generate stable wave profiles in both the spatial and time domains. Harmonic analysis and spectral analysis were used to prove the superiority of the second-order wave-maker theory from other two aspects. To simulate irregular waves, the numerical flume was improved to solve the problem of the water depth variation due to low-frequency motion of the wave board. In summary, the new numerical flume using the second-order wave-maker theory can guarantee the accuracy of waves by adding an extra motion of the wave board. The boundary treatment method can provide a reference for the improvement of nonlinear numerical flume.