北半球夏季500hPa候平均高度场的遥相关和环流特征   总被引：6，自引：0，他引：6       下载免费PDF全文

杨秋明 《大气科学》1993,17(2):148-154

本文用10年(1980—1989)夏季北半球500hPa候平均高度场资料进行遥相关分析,得到东亚太平洋型(EAP)和西欧型(WE)两种遥相关型及西亚-太平洋-大西洋振荡,并对高度场进行主成分分析(PCA),讨论了环流的时空分布特征.  相似文献   

第27届IASPEI大会概况及其主要专题讨论会和研讨会内容汇编     

Members of the SSB Delegation 《国际地震动态》1994,(6)

国际地震学与地球内部物理学协会（ＬＡＳＰＥＩ）第２７届大会于１９９４年元月１０－２１日在新西兰首都惠灵顿的惠灵顿维多利亚大学举行。来自４２个国家的４８３位科学家参加了这次大会。国家地震局派出了以副局长陈为团长的１３人代表团出席会议。本届大会共安排了２７个学术报告会和研讨会，会上宣读论文和报告３９９篇，张贴展示论文约１６０篇。本届ＩＡＳＰＥＩ大会的学术报告会和研讨会涉及广泛的地震学和地球内部物理学研究的前沿问题，内容包括：波在非均匀介质中的传播；地震危险性与地震危害；亚太地区的沉积盆地及其构造背景；地球深部间断面的构造形态和动力学；地震预测；地震层析成像和地幔动力学；俯冲带和弧后盆地；地热在下地壳、岩石学与流变学等方面之作用；区域地震的定位和定量化；毫赫与毫微赫地震学；脊区的地震学详细研究；太平洋的地震和海啸危险性；大小尺度的各向异性；全球地震观测技术的改进；地震的震源模拟和断层力学；诱发地震；非线性地震学；地震运动的地面地质效应；空间大地测量学和实时构造地质学；热流和热液循环；宽频带地震学和震源，等等。  相似文献   

非共轴光学系统传递函数计算     

何对燕 《武汉大学学报(信息科学版)》1988,(3)

用坐标变换计算非共轴光学系统是十分有效的。本文讨论了非共轴光学系统传递函数(OTF)的计算要点,并给出了平行光束传递函数的计算方法。计算了一个无焦系统的波动光学传递函数。  相似文献   

Fusion of RADARSAT-2 and multispectral optical remote sensing data for LULC extraction in a tropical agricultural area     

Mohamed Barakat A. Gibril  Suzana A. Bakar  Kouame Yao  Mohammed Oludare Idrees 《国际地球制图》2017,32(7):735-748

In this study, we investigated the performance of different fusion and classification techniques for land cover mapping in Hilir Perak, Peninsula Malaysia using RADAR and Landsat-8 images in a predominantly agricultural area. The fusion methods used are Brovey Transform, Wavelet Transform, Ehlers and Layer Stacking and their results classified into seven different land cover classes which include (1) pixel-based classifiers (spectral angle mapper (SAM), maximum likelihood (ML), support vector machine (SVM)) and (2) Object-based (rule-based and standard nearest neighbour (NN)) classifiers. The result shows that pixel-based classification achieved maximum accuracy of the optical data classification using SVM in Landsat-8 with 74.96% accuracy compared to SAM and ML. For multisource data classification, the highest overall accuracy recorded for layer stacking (SVM) was 79.78%, Ehlers fusion (SVM) with 45.57%, Brovey fusion (SVM) with 63.70% and Wavelet fusion (SVM) 61.16%. And for object-based classifiers, the overall classification accuracy is 95.35% for rule-based and 76.33% for NN classifier, respectively. Based on the analysis of their performances, object-based and the rule-based classifiers produced the best classification accuracy from the fused images.  相似文献   

Remote detection of geological structures: an application to the Aravalli region,western India     

Debaditya Acharya  Alok Porwal  Avik Bhattacharya 《国际地球制图》2017,32(3):257-273

Optical and microwave remote sensing data are used in conjunction with a digital elevation model to map lineaments in the central parts of the Aravalli region, Rajasthan, western India. Lineament maps interpreted from each data-set are subsequently combined to derive a composite lineament map of the area. Rose plots are used to identify the prominent trends of the lineaments and compared with published structural map of the study area. Three major trends are identified, namely, the NE–SW, NNE–SSW and EW, which are interpreted to be, related to the DF1, DF2 and DF4 deformation phases identified by the previous workers through field studies. The lineaments are classified as fold axes or faults, and a total of 10-fold axes and 30 faults mapped in the area.  相似文献   

Development and deployment of a precision underwater positioning system for in situ laser Raman spectroscopy in the deep ocean     

Sheri N. White  William Kirkwood  Alana Sherman  Mark Brown  Richard Henthorn  Karen Salamy  Peter Walz  Edward T. Peltzer  Peter G. Brewer 《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(12):2376-2389

The field of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, difficulty exists in using deep submergence vehicle manipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates. We have developed, tested, and successfully deployed by remotely operated vehicle (ROV) a precision underwater positioner (PUP) which provides the stability and precision movement required to perform spectroscopic measurements using the Deep Ocean Raman In situ Spectrometer (DORISS) instrument on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positioning on the seafloor. PUP is capable of translating the DORISS optical head with a precision of 0.1 mm in three dimensions over a range of at least 15 cm, at depths up to 4000 m, and under the normal range of oceanic conditions (T, P, current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. This capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, including the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral grains. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.  相似文献   

Integration of European habitat monitoring based on plant life form composition as an indicator of environmental change and change in biodiversity     

Margit Bloch-Petersen  Jesper Brandt  Martin Olsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):61-74

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 61–74, 2006

During the last 25 years a number of European countries have developed general landscape monitoring systems. In the agricultural landscapes of Denmark the Small Biotope Monitoring Program (SBMP). which focuses on the dynamics of small biotopes and their relation to changes in agricultural technology and structural characteristics, has been developed since 1981. Erom 2007, the SBMP will continue as part of the Danish nature monitoring program, NOVANA.

In Europe, during the last 10 years, several national landscape surveys have cooperated to develop a European platform for consistent landscape related habitat monitoring. This has been through the BioHab Concerted Action Framework Programme of the EU (2002–2005), and the resulting publication of a handbook for recording and monitoring habitats (Bunce et al., 2005). The focus on environmentally conditioned habitat changes at a landscape level has led to the re-introduction of Raunkiaer's plant life form concept. This approach enables the indication of changes in biodiversity based on alterations in general habitat composition and quality.

Although the objectives of the SBMP and the BioHab projects have been somewhat different, the methodologies have much in common. In this paper the background and perspectives of the two approaches are discussed, and a test of the BioHab field methodology in an area previously monitored by the SBMP is presented. It was found not to be difficult to integrate the BioHab field recording methodology with the existing SBMP methods, thus permitting the SBMP to deliver an additional European perspective, with relatively little additional effort.  相似文献   

On the reliability of the so-far performed tests for measuring the Lense–Thirring effect with the LAGEOS satellites     

Lorenzo Iorio   《New Astronomy》2005,10(8):603-615

In this paper, we critically discuss the so-far performed attempts aimed at the detection of the general relativistic gravitomagnetic Lense–Thirring effect in the gravitational field of the Earth with the existing LAGEOS satellites. In the latest reported measurement of the gravitomagnetic shift with the nodes of the LAGEOS satellites and the second generation GRACE-only EIGEN-GRACE02S Earth gravity model over an observational time span of 11 years a 5–10% total accuracy is claimed at 1–3σ, respectively. We will show that, instead, it might be 15–45% (1–3σ) if the impact of the secular variations of the even zonal harmonics is considered. Possible strategies in order both to make more robust and reliable the tests with the node-only LAGEOS–LAGEOS II combination used and to overcome the problems affecting it with other alternative combinations are presented.  相似文献   

切仑科夫铁Kα和Kβ发射线的强度比和本征红移比的计算及其在活动星系核中的可能应用     

刘当波  陈磊  尤峻汉 《天文学报》2007,48(3):269-279

当具有各向同性速度分布的相对论电子穿过稠密气体区,或者轰击稠密气体区的表面时,切仑科夫效应将会产生一种特殊的原子或离子发射线,称做切仑科夫线状发射.这一预言在光学波段已由实验室的实验所证实.把线状发射理论推广到X射线波段,给出计算切仑科夫铁Kα和Kβ发射线的强度比和本征红移比的基本公式,列出了不同价次铁线的强度比和本征红移比.这一计算结果在活动星系核中有可能找到潜在的应用.最近观测发现源NGC3783,除存在着6.4 keV的铁Kα发射线,还存在着很强的7.0 keV的铁Kβ发射线,且两者等值宽度之比为EW_(Kα)/EW_(Kβ)≈3.43,这很难用传统的"光电吸收-莹光机制"来解释.切仑科夫线状发射机制可为解决这一困惑提供一条新途径.此外,期待切仑科夫铁Kα和Kβ线的本征红移比也会在以后的观测中能得到检验.假如切仑科夫线状辐射的设想得到观测的进一步支持,则对中央大质量黑洞周围物理环境的传统认识将有大的修改-活动更加剧烈,而且更加高能,其中气体也更加稠密.  相似文献   

The effect of the prompt particle environment at L2 on optical CCDs for astronomy and astrophysics     

R.M. Ambrosi  A.D. Holland  D.R. Smith  I.B. Hutchinson  M. Denby 《Planetary and Space Science》2005,53(14-15):1449-1465

The increasing number of probes carrying large focal planes consisting of many charge-coupled devices (CCDs), planned to be sent to the L2 Lagrangian point, 1.5 million kilometres from Earth in the next 15 years, implies that a detailed study of the effects of the prompt particle environment at L2 on CCDs is required. The focus of this study will be on CCDs for optical astronomy, astrometry and photometric applications. This study will be of particular interest to GAIA the European Space Agency's (ESA) cornerstone optical astronomy mission to further explore and map sections of our galaxy in greater detail. The results will also have implications for future X-ray astronomy missions like the X-ray Evolving Universe Spectroscopy Mission (XEUS). Both the above missions will require large area focal planes incorporating many CCD detectors.The sources of the instrument background are both solar and galactic and if a probe is launched around the peak in the next solar cycle (2010), the possible false detection rate or the amount of data that could be lost during a mission must be determined. This paper presents measured data for a spacecraft in a geostationary orbit, specifically Geosynchronous Operational Environmental Satellites (GOES) data, and makes predictions of the flux and energy of the particle environment at L2. The solar and galactic cosmic ray background was determined by using the Cosmic Ray Effects on Micro-Electronics or CREME96 code. A comparison was then made between the GOES data and the output from the CREME96 code in order to make predictions about the L2 environment.  相似文献