The roughness of the dark side of Iapetus from the 2004 to 2005 flyby     

Janice S. Lee  Bonnie J. Buratti  Joel Mosher 《Icarus》2010,206(2):623-630

The roughness of a planetary surface offers clues to its past geologic history. We apply a surface roughness model developed by Buratti and Veverka (Buratti, B.J., Veverka, J. [1985]. Icarus 64, 320-328) to Cassini ISS data from the January 1st, 2005 flyby of Iapetus. This model uses the observed scattering behavior to provide a depth to radius factor q quantifying the size of idealized craters on the surface. Our findings indicate that the surface on the dark side is significantly smoother than the surfaces of other icy low-albedo saturnian satellites. We have found that the average depth to radius on the leading (dark) side is 0.084, corresponding to a Hapke mean slope angle of 6°. As compared to the 13-33° Hapke mean slope angle of other icy satellites (Buratti, B.J., and 10 colleagues [2008]. Icarus 193, 309-322), our results present a clearly different picture for the leading surface of Iapetus, suggesting that the dark deposit contributes to the decrease in macroscopic surface roughness of the leading side. Attempts were made to obtain an average depth to radius value for the trailing (bright) side; however the scans of the bright side from this flyby exhibited large variations in albedo, resulting in results that were physically unrealistic.  相似文献   

Sustaining marine life beyond boundaries: Options for an implementing agreement for marine biodiversity beyond national jurisdiction under the United Nations Convention on the Law of the Sea     

《Marine Policy》2014

For nearly a decade, governments have been discussing the need to improve efforts to conserve and sustainably use marine biodiversity in areas beyond national jurisdiction (ABNJ). Support for a new international agreement under the United Nations Convention on the Law of the Sea (UNCLOS) – an Implementing Agreement – on the conservation and sustainable use of marine biodiversity in ABNJ has been growing. In June 2012, at the United Nations Conference on Sustainable Development held in Rio de Janeiro, Brazil, States agreed to take a decision on the development of an international instrument under UNCLOS before the end of the 69th session of the United Nations General Assembly (UNGA), which runs from September 2014 to August 2015. In follow-up to this commitment, it was agreed to consider the “scope, parameters and feasibility” of this instrument. To inform these international discussions, this article highlights some potential options for the content of a new UNCLOS Implementing Agreement. It first reviews the history of UN discussions, and then elaborates on options to address key elements identified as priorities for States in 2011: marine genetic resources, including the sharing of benefits, area-based management tools, including marine protected areas, environmental impact assessments, capacity-building and the transfer of marine technology. It addresses cross-cutting issues such as the governing principles, institutional structure as well as on other critical points such as High Seas fishing and flag State responsibilities. The article concludes with suggestions on possible next steps in order to succeed in the negotiations for an agreement.  相似文献   

The use of ocean color remote sensing in integrated coastal zone management—A case study from Himmerfjärden,Sweden     

《Marine Policy》2014

In this study the use of ocean color data as a diagnostic tool in integrated coastal zone management was investigated as part of the Science Policy Integration for Coastal Systems Assessment (SPICOSA) project. Parallel to this, an operational coastal monitoring system has been set up in close collaboration with end-users. The core work of the bio-optical part in the project was to develop Secchi depth and attenuation of light as indicators for coastal zone management, by linking remote sensing with the socio-economic and ecological model developed in SPICOSA. The article emphasizes the benefits of stakeholder involvement and end-user feedback for efficient and improved system development. Furthermore, conceptual models were developed on how to integrate remote sensing data into coastal zone management and into a physical-biological model of the Baltic Sea. One of the work packages in the SPICOSA project was academic training. In this work package, on-line teaching material in the field of remote sensing and bio-optics was developed and disseminated on the SETnet web page. The article presented here may act as supportive material for training in bio-optics and remote sensing.  相似文献   

Automatic registration of optical imagery with 3D LiDAR data using statistical similarity     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

The development of robust and accurate methods for automatic registration of optical imagery and 3D LiDAR data continues to be a challenge for a variety of applications in photogrammetry, computer vision and remote sensing. This paper proposes a new approach for the registration of optical imagery with LiDAR data based on the theory of Mutual Information (MI), which exploits the statistical dependency between same- and multi-modal datasets to achieve accurate registration. The MI-based similarity measures quantify dependencies between aerial imagery, and both LiDAR intensity data and 3D point cloud data. The needs for specific physical feature correspondences, which are not always attainable in the registration of imagery with 3D point clouds, are avoided. Current methods for registering 2D imagery to 3D point clouds are first reviewed, after which the mutual MI approach is presented. Particular attention is given to adoption of the Normalised Combined Mutual Information (NCMI) approach as a means to produce a similarity measure that exploits the inherently registered LiDAR intensity and point cloud data so as to improve the robustness of registration between optical imagery and LiDAR data. The effectiveness of local versus global similarity measures is also investigated, as are the transformation models involved in the registration process. An experimental program conducted to evaluate MI-based methods for registering aerial imagery to LiDAR data is reported and the results obtained in two areas with differing terrain and land cover, and with aerial imagery of different resolution and LiDAR data with different point density are discussed. These results demonstrate the potential of the MI and especially the CMI methods for registration of imagery and 3D point clouds, and they highlight the feasibility and robustness of the presented MI-based approach to automated registration of multi-sensor, multi-temporal and multi-resolution remote sensing data for a wide range of applications.  相似文献   

Assessment of satellite ocean color products of MERIS,MODIS and SeaWiFS along the East China Coast (in the Yellow Sea and East China Sea)     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

The validation of satellite ocean-color products is an important task of ocean-color missions. The uncertainties of these products are poorly quantified in the Yellow Sea (YS) and East China Sea (ECS), which are well known for their optical complexity and turbidity in terms of both oceanic and atmospheric optical properties. The objective of this paper is to evaluate the primary ocean-color products from three major ocean-color satellites, namely the Moderate Resolution Imaging Spectroradiometer (MODIS), Medium Resolution Imaging Spectrometer (MERIS), and Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Through match-up analysis with in situ data, it is found that satellite retrievals of the spectral remote sensing reflectance R_rs(λ) at the blue-green and green bands from MERIS, MODIS and SeaWiFS have the lowest uncertainties with a median of the absolute percentage of difference (APD_m) of 15–27% and root-mean-square-error (RMS) of 0.0021–0.0039 sr⁻¹, whereas the R_rs(λ) uncertainty at 412 nm is the highest (APD_m 47–62%, RMS 0.0027–0.0041 sr⁻¹). The uncertainties of the aerosol optical thickness (AOT) τ_a, diffuse attenuation coefficient for downward irradiance at 490 nm K_d(490), concentrations of suspended particulate sediment concentration (SPM) and Chlorophyll a (Chl-a) were also quantified. It is demonstrated that with appropriate in-water algorithms specifically developed for turbid waters rather than the standard ones adopted in the operational satellite data processing chain, the uncertainties of satellite-derived properties of K_d(490), SPM, and Chl-a may decrease significantly to the level of 20–30%, which is true for the majority of the study area. This validation activity advocates for (1) the improvement of the atmosphere correction algorithms with the regional aerosol optical model, (2) switching to regional in-water algorithms over turbid coastal waters, and (3) continuous support of the dedicated in situ data collection effort for the validation task.  相似文献   

传感光纤-砂土界面力学性质的试验研究     

佘骏宽  朱鸿鹄  张诚成  施斌  严臖凡 《工程地质学报》2014,22(5):855-860

近年来分布式光纤感测技术在岩土与地质工程领域的应用研究已成为一个研究热点,但工程实践表明,埋入式传感光纤与被测岩土体之间的变形协调性会对监测结果产生显著的影响,该问题一直制约着光纤感测技术在工程监测中的推广。本文通过一系列室内拉拔试验,对比了3种预埋于砂土中的单模光纤在不同上覆压力的作用下的拉拔力-拉拔位移曲线,并建立了一个用于描述光纤-砂土界面力学性质的三段式的拉拔模型,分析峰值拉拔力、残余拉拔力、有效拉拔位移和残余拉拔位移4个参数在不同上覆压力作用下的变化情况。分析结果揭示传感光纤-砂土界面的力学特性和应力传递规律,为分布式光纤传感技术在岩土体变形监测中的应用,尤其在变形监测光纤的选用标准方面,提供了参考依据。  相似文献   

X-rays from the Symbiotic Star RX Pup     

Gerardo J. M. Luna  J. L. Sokoloski  Roberto D. D. Costa 《Astrophysics and Space Science》2006,304(1-4):283-285

We describe X-ray and optical observations of the symbiotic star RX Pup. From low resolution optical spectra, we obtain a reddening for RX Pup of E(B−V)=0.79. We use the neutral column density corresponding to this reddening as a lower limit for the X-ray spectra fits. The X-ray spectra can be fitted with either a two-temperarure thermal plasma model or a single-temperature plasma plus a narrow line at ≈0.55 keV, each modified by interstellar absorption. The RX Pup X-ray flux is not variable within the observation exposure time, suggesting that unlike in most CVs, an accretion disk boundary layer does not contribute significantly to the X-ray flux. Instead, the X-ray emission may come from shock-heated gas further away from the compact object.  相似文献   

地质工程专业普通地质认识实习教学的思考     

许宝田  张勇  王博  杨爱华  解国爱 《高校地质学报》2022,28(3):382-386

文章针对地质工程专业中基础地质学的重要性和普地实习野外教学实际,提出在普地实习中融入地质工程专业知识教学内容。从岩石基本地质特征、力学问题和具体工程地质问题3个方面将基础地质学与地质工程专业知识进行融合、交叉。从而拓展学生视野,实现实习模式创新、内容改革,促进学生学习意识和自主学习的发展,提升专业思维。岩石成分与岩石力学性质、风化特征和水软化性关系密切,节理面的粗糙、起伏和充填物成分影响节理面抗剪、透水等特性,具体工程中的“滑坡”问题是典型的岩体剪切破坏问题,其形成的力学机制与剪节理相同。将上述问题两者联系起来的讲解丰富了普地实习的内容。文章认为普地实习中观察到的现象与地质工程专业课程中很多知识点紧密联系,在基础地质实习教学中融入上述地质工程的专业知识是完全可行性的,采取增加与地质工程专业结合的实践教学环节的办法,既扩大了学生知识面,初步提高学生专业素养,也为实现毕业后成为专业领域合格工程师和科研人员的培养目标迈出重要的第一步。  相似文献   

Evaluation and comparison of CMIP6 models and MERRA-2 reanalysis AOD against Satellite observations from 2000 to 2014 over China     

《地学前缘(英文版)》2022,13(2):101325

Rapid industrialization and urbanization along with a growing population are contributing significantly to air pollution in China. Evaluation of long-term aerosol optical depth (AOD) data from models and reanalysis, can greatly promote understanding of spatiotemporal variations in air pollution in China. To do this, AOD (550 nm) values from 2000 to 2014 were obtained from the Coupled Model Inter-comparison Project (CIMP6), the second version of Modern-Era Retrospective analysis for Research, and Applications (MERRA-2), and the Moderate Resolution Imaging Spectroradiometer (MODIS; flying on the Terra satellite) combined Dark Target and Deep Blue (DTB) aerosol product. We used the Terra-MODIS DTB AOD (hereafter MODIS DTB AOD) as a standard to evaluate CMIP6 Ensemble AOD (hereafter CMIP6 AOD) and MERRA-2 reanalysis AOD (hereafter MERRA-2 AOD). Results show better correlations and smaller errors between MERRA-2 and MODIS DTB AOD, than between CMIP6 and MODIS DTB AOD, in most regions of China, at both annual and seasonal scales. However, significant under- and over-estimations in the MERRA-2 and CMIP6 AOD were also observed relative to MODIS DTB AOD. The long-term (2000–2014) MODIS DTB AOD distributions show the highest AOD over the North China Plain (0.71) followed by Central China (0.69), Yangtse River Delta (0.67), Sichuan Basin (0.64), and Pearl River Delta (0.54) regions. The lowest AOD values were recorded over the Tibetan Plateau (0.13 ± 0.01) followed by Qinghai (0.19 ± 0.03) and the Gobi Desert (0.21 ± 0.03). Large amounts of sand and dust particles emitted from natural sources (the Taklamakan and Gobi Deserts) may result in higher AOD in spring compared to summer, autumn, and winter. Trends were also calculated for 2000–2005, for 2006–2010 (when China introduced strict air pollution control policies during the 11th Five Year Plan or FYP), and for 2011–2014 (during the 12th FYP). An increasing trend in MODIS DTB AOD was observed throughout the country during 2000–2014. The uncontrolled industrialization, urbanization, and rapid economic development that mostly occurred from 2000 to 2005 probably contributed to the overall increase in AOD. Finally, China's air pollution control policies helped to reduce AOD in most regions of the country; this was more evident during the 12th FYP period (2011–2014) than during the 11th FYP period (2006–2010). Therefore this study strongly advises the authority to retain or extend these policies in the future for improving air quality.  相似文献   

The Cherenkov Telescope Array potential for the study of young supernova remnants     

《Astroparticle Physics》2015

Supernova remnants (SNRs) are among the most important targets for γ-ray observatories. Being prominent non-thermal sources, they are very likely responsible for the acceleration of the bulk of Galactic cosmic rays (CRs). To firmly establish the SNR paradigm for the origin of cosmic rays, it should be confirmed that protons are indeed accelerated in, and released from, SNRs with the appropriate flux and spectrum. This can be done by detailed theoretical models which account for microphysics of acceleration and various radiation processes of hadrons and leptons. The current generation of Cherenkov telescopes has insufficient sensitivity to constrain theoretical models. A new facility, the Cherenkov Telescope Array (CTA), will have superior capabilities and may finally resolve this long standing issue of high-energy astrophysics. We want to assess the capabilities of CTA to reveal the physics of various types of SNRs in the initial 2000 years of their evolution. During this time, the efficiency to accelerate cosmic rays is highest. We perform time-dependent simulations of the hydrodynamics, the magnetic fields, the cosmic-ray acceleration, and the non-thermal emission for type Ia, Ic and IIP SNRs. We calculate the CTA response to the γ-ray emission from these SNRs for various ages and distances, and we perform a realistic analysis of the simulated data. We derive distance limits for the detectability and resolvability of these SNR types at several ages. We test the ability of CTA to reconstruct their morphological and spectral parameters as a function of their distance. Finally, we estimate how well CTA data will constrain the theoretical models.  相似文献