Multiple outlier detection by evaluating redundancy contributions of observations

When applying single outlier detection techniques, such as the Tau () test, to examine the residuals of observations for outliers, the number of detected observations in any iteration of adjustment is most often more numerous than the actual number of true outliers. A new technique is proposed which estimates the number of outliers in a network by evaluating the redundancy contributions of the detected observations. In this way, a number of potential outliers can be identified and eliminated in each iteration of an adjustment. This leads to higher efficiency in data snooping of geodetic networks. The technique is illustrated with some numerical examples.     

Analysis of 2-d flare spectra: Velocity fields derived from Hα line asymmetries

We derive a time series of two-dimensional velocity fields for a flare region on 1992 December 16, based on the asymmetries of the H line. The H spectra were obtained by an imaging spectrograph at the Solar Tower Telescope of Nanjing University. Four sites with evident chromospheric downflows are found to appear and decay consecutively in the studied region. The value of maximum velocities is 30–40 km s^–1 and the lifetime of downflows is 2–3 min at these sites. It is also shown that the asymmetries only exist at the line wing, while the line center has nearly no shifts for this flare. Finally, we make a discussion on the characteristics of the velocity distribution and its correlations with the intensity distribution, as well as with the hard X-ray emission.     

Scattering of elastic waves by a fracture zone containing randomly distributed cracks

We theoretically study the scattering ofP, SV andSH waves by a zonal distribution of cracks, which simulates a fault fracture zone. An investigation is conducted how the geometrical properties of the crack distribution and the frictional characteristics of the crack surface are reflected in the attenuation and dispersion of incident waves, as well as in the amplitudes of the transmitted and reflected waves from the zone. If the crack distribution within the fault zone changes temporally during the preparation process of the expected earthquake, it will be important for earthquake prediction to monitor it, utilizing the scattering-induced wave phenomena.We consider the two-dimensional problem. Aligned cracks with the same length are assumed to be randomly distributed in a zone with a finite width, on which elastic waves are assumed to be incident. The distribution of cracks is assumed to be homogeneous and sparse. The crack surface is assumed to be stress-free, or to undergo viscous friction; the latter case simulates fluid-filled cracks. The opening displacement of the crack is assumed to be negligibly small. The idea of the mean wave formalism is employed in the analysis, and Foldy's approximation is assumed.When the crack surface is stress-free, it is commonly observed for every wave mode (P, SV andSH) that the attenuation coefficientQ ^–1 peaks aroundka1, the phase velocity is almost independent ofk in the rangeka<1 and it increases monotonically withk in the rangeka>1, wherek is the intrinsicS wavenumber anda is the half length of the crack. The effect of the friction is to shift the peak ofQ ^–1 and the corner of the phase velocity curve to the low wavenumber range. The high wavenumber asymptote ofQ ^–1 is proportional tok ^–1 independently of model parameters and the wave modes. If the seismological observation thatQ ^–1 ofS waves has a peak at around 0.5 Hz in the earth's crust is combined with our results, the upper limit of crack size within the crust is estimated about 4 km. The information regarding the transmitted and reflected waves, such as the high wavenumber limit of the amplitude of the transmitted wave etc., allows estimation of the strength of the friction.     

Study on the kinetics of iron oxide leaching by oxalic acid

The presence of iron oxides in clay or silica raw materials is detrimental to the manufacturing of high quality ceramics. Although iron has been traditionally removed by physical mineral processing, acid washing has been tested as it is more effective, especially for extremely low iron (of less than 0.1% w/w). However, inorganic acids such as sulphuric or hydrochloric acids easily contaminate the clay products with SO₄²⁻ and Cl⁻, and therefore should be avoided as much as possible. On the other hand, if oxalic acid is used, any acid left behind will be destroyed during the firing of the ceramic products. The characteristics of dissolution of iron oxides were therefore investigated in this study.The dissolution of iron oxides in oxalic acid was found to be very slow at temperatures within the range 25–60 °C, but its rate increases rapidly above 90 °C. The dissolution rate also increases with increasing oxalate concentration at the constant pH values set within the optimum range of pH2.5–3.0. At this optimum pH, the dissolution of fine pure hematite (Fe₂O₃) (105–140 μm) follows a diffusion-controlled shrinking core model. The rate expression expressed as 1 − (2 / 3)x − (1 − x)^2 / 3 where x is a fraction of iron dissolution was found to be proportional to [oxalate]^1.5.The addition of magnetite to the leach liquor at 10% w/w hematite was found to enhance the dissolution rate dramatically. Such addition of magnetite allows coarser hematite in the range 0.5–1.4 mm to be leached at a reasonable rate.     

藏西北三岔口地区泥瓮系生物礁特征及其意义

在羌塘西部的三岔口一带泥盆系拉竹龙组中发现规模较大的生物礁——台地前缘礁。下层礁体厚7．28m，上层礁体厚40.98m。两个礁体均为叠置礁，礁体由礁基、礁核、礁顶组成。剖面显示发育有礁前垮塌角砾、礁格架、礁间及礁后环境。泥盆纪生物礁的发现为羌塘盆地寻找油气资源提供了新思路。     

国外城市群经济联系空间研究进展

城市群经济联系的复杂性空间规律已经成为城市地理学、区域地理学、经济地理学研究的重点范畴。现代意义的城市群经济联系空间发展研究始于50年代,城市群体化现象大规模出现,城市化进程迅速发展的时期。经过二战前的启蒙发展、二战后-60年代的初步发展、70-80年代的丰富深化、90年代的全面发展阶段,50多年来城市群空间研究领域不断深化、研究队伍不断壮大、研究成果不断涌现、研究范式不断丰富,呈现多视角、多层次、多尺度,理论与实证、定性与定量相结合的研究体系,研究内容上文章着重对国外大都市区、都市带等城市群经济联系的空间组织与结构研究进行总结,并指出当前研究的热点与焦点。     

草原旅游发展的实践及空间格局研究

草原以其辽阔、坦荡的景观以及风土人情构成一类旅游目的地,世界上拥有大片草原的国家都非常重视草原旅游业的发展。我国草原旅游发展也较快,形成了不同空间类型、不同植被景观类型和不同人文与自然结合类型的旅游发展格局,其中又以内蒙古最为突出。但是,由于草原生态系统的脆弱性,决定了草原旅游发展存在脆弱性,因此,在开发中需要更加严格的科学规划和管理。     

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement (MEIFR) is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique (corresponding to the maximum curvature) and slope technique (slope being 1) are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.     

基于IMAGIS的数字小区建模探讨

随着城市化水平的不断提高，对城市的规划管理也提出了很高的要求，数字城市作为数字地球的重要组成部分正是在这一背景下提出的。本文结合适普公司的IMAGIS软件，对城市小区鼍维场景建设中的相关问题进行了探讨，并以遂宁市某街区为例进行了实践。     

一种数据网格的元数据分类管理机制研究

网格环境下数据发现和访问的关键问题是应用元数据管理和拷贝元数据管理，针对这一问题，提出了一种元数据分类管理机制。该机制定义了数据模型和应用元数据模式，采用了分类存储的方式对不同的元数据进行管理，并设计了一个基于向导的查询智能体。