An Observation Operator for Radar Refractivity Change: Comparison of Observations and Convective-Scale Simulations

Weather radar refractivity depends on low-level moisture, temperature, and pressure and is available at high space–time resolutions over large areas. It is of definite meteorological interest for assimilation, verification, and process-study purposes. In this study, the path-averaged refractivity change is simulated from the Arome cloud-resolving atmospheric system analyses and compared with corresponding radar observations over a 35-day period with various meteorological conditions. For that, a novel post-processing procedure is applied to radar data to improve its quality. Also, an observation operator is developed that ingests Arome analyses and simulates a 3-h path-averaged refractivity change. A sensitivity study shows that simulated path-averaged refractivity change is immune to the modelling of the beam height as long as it remains below approximately 60 m above the ground. Comparisons show overall consistency between observed and simulated path-averaged refractivity change, with discrepancies at times that suggest an improvement in analyses once radar refractivity change observations are assimilated. Finally, errors introduced when retrieving local refractivity from path-averaged refractivity are estimated and it is found for our dataset that such retrievals halve the range of usable observations.     

Passive sonar ML estimator for ship propeller speed

The optimal estimator in the maximum-likelihood sense fur the propeller speed of a ship, using underwater radiated cavitation noise generated by the propeller blades, is derived. From the result the number of blades on the propeller can also be derived. Results obtained for real sonar data using a digital implementation of the estimator will be presented     

Energy-Momentum of a Stationary Beam of Light in Teleparallel Gravity

In this paper, we utilize the teleparallel gravity analogs of the energy and momentum definitions of Bergmann-Thomson and Landau-Lifshitz in order to explicitly evaluate the energy distribution (due to matter and fields including gravity) based on the Bonnor space-time, it is shown that for a stationary beam of light, these energy-momentum definitions give the same result. Furthermore, this result supports the viewpoint of Cooperstock and also agree with the previous works by Bringley and Gad.     

光纤光学延迟线及其应用于望远镜干涉阵的可行性研究

本文叙述了一台全新的全光学干涉仪，以此干涉仪为基础，就光纤联接的望远镜干涉阵中用拉伸光纤实现光程补偿的方法在国际上首次进行了研究，在对试验结果进行分析，讨论的基础上肯定了该方法的可行性。     

Quadtree-guided 3-D interpolation of irregular sonar data sets

Bottom-penetrating sonar can be used to visualize large areas, for example by normal logging and printing of collected pings. In many applications, it is necessary to obtain an impression of three-dimensional (3-D) structures, but this is not easy because of the irregular spatial sampling due to coarse ship trajectories. Normally, the ping map and the ping data, cover only a very small part of a region of interest. In this paper, we describe a new method for interpolating irregularly spaced sonar data. The basic idea is to use a two-dimensional quadtree of the ping map in order to guide the 3-D interpolation process: since gaps between pings become smaller at higher tree levels, the volume can be filled by marking neighborhood relations in the quadtree and interpolating available pings when they become neighbors. Different marking schemes and their central processing unit times are compared. In the interpolation process, we apply cross correlations of ping data in order to construct continuity of sloping reflections. Our results show that excellent results can be obtained on real sonar data sets, even for volumes filled for less than 7%, for which processing times are reasonable even for large areas, and that the interpolated data can be used for volumetric interactive visualization.     

现代海底烟囱中流体包裹体的研究

大洋中脊的海底块状硫化物矿床是当前地球科学的一个热点。因为他不仅具有经济效益,而且可以直接观测到这些矿床的形成过程。这些矿床均有许多黑烟囱和白烟囱。在这些烟囱中成矿流体不断地流过,并同时沉淀出Cu,Pb,Zn硫化物和脉石矿物。本研究的样品是取自北纬21°N的太平洋洋脊中现代大洋海底的Zn(Cu)型硫化物烟囱。对这些烟囱的矿物共生组合进行研究发现其矿物组合相当简单,分硫化物和脉石矿物两种。硫化物中以其含量多少排列为闪锌矿,黄铁矿,黄铜矿和磁黄铁矿。脉石矿物以硬石膏为主,见少量重晶石。在烟囱中这些硫化物和脉石矿物的分布是有分带性的。从外到内为硬石膏带,黄铁矿带,闪锌矿带。闪锌矿带向里可见到少量黄铜矿和磁黄铜矿,及硬石膏,但它们尚未构成一个带。烟囱的中心常常是空的,因为是原来的热液通道。 发现两类流体包裹体:一类为水溶液相包裹体。另一类为CH_4的包裹体。其均一温度是从180～265℃。最外面的硬石膏带,均一温度从180～245℃(平均212℃)。黄铁矿带均一温度从185～260℃(平均218℃)。闪锌矿带均一温度从190～265℃(平均229℃)。从平均的均一温度看似乎从边上到中心从212—218—229℃向上升,说明一个趋势,中间的温度较高,边上的较低。成矿溶液的盐度与海水相差不大,但略大於海水