BDRM理论在双轴海洋声道中的应用

由于表面声道与深海声道间的耦合效应,声波在双轴海洋声道中的传播比较复杂,因此求解双轴海洋声道中的声场就比较困难。在 WKBZ 本征函数的基础上,推导出了参考界面相位修正的一致表达式,并将浅海声传播的波束位移射线简正波(BDRM)理论应用于计算双轴海洋声道中的声场,进行了数值模拟并与传统简正波方法进行比较,结果表明应用 BDRM 理论计算的传播损失具有很高的精度和速度,可以对双轴海洋声道内声传播问题进行分析和预报。     

川东北Y地区雷口坡组古岩溶辨识标志

川东北Y地区三叠系雷口坡组沉积后,受三叠纪印支Ⅰ幕运动的影响,Y地区抬升,缺失部分上三叠统、部分中三叠统,与上覆上三叠统须家河组呈区域性平行不整合接触,接受大气淡水淋滤,为古岩溶的形成提供了有利条件.通过对研究区钻井资料、测井资料的分析,借助岩心观察与岩石薄片,以及电子探针、阴极发光、碳氧同位素等测试手段,综合分析和研...     

三维航标监测与管理系统的设计与实现

设计了三维航标监测与管理系统的整体框架和功能结构,研究了其涉及的若干关键技术,开发实现了系统功能.     

Time‐sensitive astronomy in non‐robotic telescopes

Protocols for dealing with time‐sensitive observations have traditionally focused on robotic telescope networks and other types of automated dedicated facilities, mostly in the optical domain. Using UKIRT and JCMT as examples, which are infrared and sub‐millimetre telescopes with a traditional PI‐dominated user base, we discuss how such facilities can join a heterogeneous telescope network to their mutual advantage. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

DOC budgets of drained peat catchments: implications for DOC production in peat soils

The blocking of drainage ditches in peat has been proposed as a possible mitigation strategy for the widely observed increases in dissolved organic carbon (DOC) concentrations from northern peatlands. This study tested the hypothesis that drain‐blocking could lead to lower DOC concentrations by measuring the DOC export from a series of small peat‐covered catchments over a period of 2 years. Six catchments were chosen: two were pristine that had never been drained; three where drains had been blocked (one in 1995, and two in 2003); and a control peat drain catchment where the drain was left unblocked throughout the study. In the case where drains were blocked as part of thus study, the drains were observed for 2 months before blocking and 2 years after blocking. The results show that: (i) high concentrations of DOC can come from water ponded in the drain; (ii) the DOC export (flux of DOC per area of catchment) from the six study catchments shows a high degree of positive correlation with both catchment size and water yield; (iii) distinctly lower DOC export with water yield was observed for the catchments containing higher‐order channels (>27 500 m²) as opposed to single drain catchments (>7500 m²); (iv) drain‐blocking resulted in a statistically significant decrease in DOC export (average was 39%) but the effect upon DOC concentration explained only 1% of the variance in the data. The results suggest that drain blocking works by decreasing the flow from the drain, not by changing the production of DOC in the peat. The change in export with catchment size implies a considerable removal of DOC from large catchments. Copyright © 2009 John Wiley & Sons, Ltd.     

The United Kingdom Infrared Telescope Deep Impact observations: Light curve, ejecta expansion rates and water spectral features

We present results from the United Kingdom Infrared Telescope observations of the impact of Deep Impact with Comet 9P/Tempel 1, on July 4, 2005 UT. These observations were carried out in conjunction with the worldwide observing campaign co-ordinated by K.J. Meech [Meech, K.J., and 208 colleagues, 2005. Science 310, 265-269]. The UKIRT team was the first to observe and announce the successful impact. At 05:50:52 (±2.5 s) UT the visible camera that is used to guide the telescope on the comet showed the start of a rapid rise in intensity, such that the visible brightness of Tempel 1 approximately doubled in 70 s. After that time there was a steady increase in the visible flux from the comet until it reached a maximum around 35 min post-impact, at which point it was more than ten times its original intensity. From an average of the time to maximum brightness and the time to noticeable intensity decline, we deduce that the material ejected by the impact expanded with a range of velocities between ∼125 and ∼390 m/s. We also observed water emission lines in the spectral region from 2.8945 to 2.8985 μm. We noted several water lines, which are known to be pumped by sunlight. But there was a lower intensity spectral component, which we propose may result from solar heating of icy grains freshly exposed by the impact.     

The Morávka meteorite fall: 3. Meteoroid initial size,history, structure,and composition

Abstract— The properties and history of the parent meteoroid of the Morávka H5–6 ordinary chondrites have been studied by a combination of various methods. The pre‐atmospheric mass of the meteoroid was computed from fireball radiation, infrasound, seismic signal, and the content of noble gases in the meteorites. All methods gave consistent results. The best estimate of the pre‐atmospheric mass is 1500 ± 500 kg. The fireball integral bolometric luminous efficiency was 9%, and the acoustic efficiency was 0.14%. The meteoroid cosmic ray exposure age was determined to be (6.7 ± 1.0) × 10⁶ yr. The meteorite shows a clear deficit of helium, both ³He and ⁴He. This deficit can be explained by solar heating. Numerical backward integration of the meteoroid orbit (determined in a previous paper from video records of the fireball) shows that the perihelion distance was probably lower than 0.5 AU and possibly as low as 0.1 AU 5 Ma ago. The collision which excavated Morávka probably occurred while the parent body was on a near‐Earth orbit, as opposed to being confined entirely to the main asteroid belt. An overview of meteorite macroscopic properties, petrology, mineralogy, and chemical composition is given. The meteorites show all mineralogical features of H chondrites. The shock level is S2. Minor deviations from other H chondrites in abundances of trace elements La, Ce, Cs, and Rb were found. The ablation crust is enriched with siderophile elements.     

Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis

Sites impacted by per- and polyfluoroalkyl substances (PFAS) pose significant challenges to investigation and remediation, including very low cleanup objectives, limited information on natural PFAS degradation processes in the subsurface, and the apparent mobility and persistence of PFAS. Consequently, monitored natural attenuation (MNA) may be considered less applicable to PFAS compared to biodegradable classes of chemicals such as petroleum hydrocarbons and chlorinated solvents that can completely biodegrade to innocuous end products. However, MNA has proven effective for certain non-degrading metals, metalloids, and radionuclides (e.g., chromium, arsenic, and uranium). To assess the applicability of MNA to PFAS, this paper reviews the fate and transport properties of PFAS in conjunction with the various physiochemical factors that control the subsurface movement of chemicals. This analysis demonstrates that two important retention processes: (1) chemical retention in the form of PFAS precursors, and (2) geochemical retention in the form of sorption and matrix diffusion to mitigate the movement and potential impacts of PFAS in groundwater that may form the scientific basis for applying MNA to PFAS contamination. This paper describes the scientific and regulatory basis for using MNA to manage PFAS-impacted groundwater.     

基于Erdas2013的Pleiades卫星影像区域网平差设计与实现

介绍了Pleiades卫星影像数据及基于Erdas 2013的Pleiades卫星影像应用的可行性和区域网平差技术,为该卫星影像应用于相关测绘工程提供了技术依据。