论几种常用重力异常正演公式的计算精度及速度

本文讨论了四种常用重力异常正演公式的计算速度以及用另外三种形体公式拟合立方体公式的计算精度。其结果表明,在通常情况下,用直立线元公式代替立方体公式进行正演计算,除保证一定计算精度外,还可提高计算速度近20倍。     

拓扑多边形自相交判断及纠正方法

提出了一种解决地形图处理中拓扑多边形自相交问题的方法。首先在原多边形内部构建新多边形,通过判定新多边形的顶点是否为原多边形内点实现了多边形自相交的判断。最后利用三种方式对存在自相交的多边形进行纠正。基于VC＋＋6.0实现相关功能,并以实例验证了这一方法的稳定性和可行性。     

长大隧道洞内自由测站边角交会网平面控制测量

为了减小长大隧道洞内控制网中的横向贯通误差,文章提出一种隧道洞内平面控制测量新方法——自由测站边角交会网.文中介绍了自由测站边角交会网的网型特点、外业观测方法和内业数据处理方珐,并提出了自由测站边角交会网的附合路线闭合差和横向贯通误差计算等方法.通过对洞内横向贯通中误差进行估算并结合仿真测量实验,验证了自由测站边角交会网应用于隧道洞内平面控制中的可行性,实验表明,自由测站边角交会网在削减横向贯通误差等方面,要优于传统的导线网.     

时间域航空电磁系统瞬变全时响应正演模拟

近年来很多专家学者致力于时间域航空系统正反演的研究.本文针对一维均匀层状介质和三维模型进行正演.不仅计算垂直方向上的电磁响应,还计算了同线方向上的电磁响应,为航空电磁多分量观测提供理论依据.通过比较航空电磁系统的脉冲响应和阶跃响应特征,发现脉冲响应在早期时间存在奇异性,造成计算不稳定.然而,阶跃响应在早期时间没有奇异性,因而利用系统的阶跃响应可得到一种计算时间域航空电磁系统全时响应的稳定算法.该算法具有较高的精度,并很好地保持了磁场强度B和磁感应dB/dt关系的一致性.该算法推广到三维地质体的时间域正演模拟亦取得很好的效果.     

随钻伽马测井快速正演算法及地质导向应用

在定向井及水平井钻井过程中,常采用地质导向技术;地质导向的关键在于实时确定地层界面和产状、实现地层模型的实时更新和井眼轨迹的及时调整,从而最大限度地提高油层的钻遇率.利用基于地层模型的测井响应正演曲线与随钻测井曲线进行对比是确定地层界面的有效方法;本文基于伽马射线在地层中的衰减规律,导出了不同地层模型中随钻伽马测井响应快速正演算法,克服了目前难以将蒙特卡罗算法用于实时随钻伽马测井正演的困难.应用实例表明该方法可以有效地辅助实时判定实际地层界面,更好地实现地质导向.     

An iconic query language for topological relationships in GIS

Abstract

The study of query languages for spatial databases is an active research area. This paper describes a new spatial query language that uses a visual grammar to express topological relationships. It is supplemented by text and icons to handle other spatial and non-spatial queries. A graphical user interface is also developed to provide an interactive environment for composing the iconic query command. To test the language, the interface is implemented on a SUN 4 Workstation and linked to Ingres, a relational DBMS. Preliminary tests show that the iconic query language is more convenient for expressing spatial concepts than conventional textual languages. This is due mainly to the two-dimensionality of iconic languages in contrast with the linear nature of conventional languages.     

近断层地震动作用下土质边坡动力响应研究

根据汶川地震中滑坡多沿断层分布的特点,利用FLAC有限差分软件建立了一个土质边坡动力数值分析模型,分别研究了具有向前方向性效应、滑冲效应和无速度脉冲的近断层地震动作用下边坡的动力响应.结果表明:含速度脉冲地震动对边坡的破坏作用远强于无速度脉冲地震动,且具有滑冲效应的地震动引起的边坡动力响应稍大于向前方向性效应地震动.近断层地震作用下,边坡水平方向绝对峰值加速度分布存在沿高程放大效应.具有向前方向性效应的地震动会增强边坡加速度的高程放大效应而具有滑冲效应的地震动则在一定程度上削弱了这种放大效应,且边坡中下部绝对峰值加速度值相对于向前方向性效应地震动和无速度脉冲地震动引起的绝对峰值加速度值较大.     

Resolving the Routine Presence of Kyanite,Andalusite and Sillimanite across a Region using Foliation Intersection/Inflection Axes Preserved in Porphyroblasts,Petrographic Observations and Thermobarometry

Constraints from P-T pseudosections (MnNCKFMASH system), foliation intersection/inflection axes preserved in porphyroblasts (FIAs), mineral assemblages and textural relationships for rocks containing all three Al2SiO5 polymorphs indicate a kyanite→ andalusite→ sillimanite sequential formation at different times rather than stable coexistence at the Al2SiO5 triple point. All three Al2SiO5 polymorphs grew in the Chl, Bt, Ms, Grt, St, Pl and Crd bearing Ordovician Clayhole Schist in Balcooma, northeastern Australia separately along a looped P-T-t-D path that swaps from clockwise to anticlockwise in the tectono-metamorphic history of the region. Kyanite grew during crustal thickening in an Early Silurian Orogenic event followed by decompression/heating, andalusite and fibrolitic sillimanite growth during Early Devonian exhumation.     

Groundwater age,life expectancy and transit time distributions in advective–dispersive systems; 2. Reservoir theory for sub-drainage basins

Groundwater age and life expectancy probability density functions (pdf) have been defined, and solved in a general three-dimensional context by means of forward and backward advection–dispersion equations [Cornaton F, Perrochet P. Groundwater age, life expectancy and transit time distributions in advective–dispersive systems; 1. Generalized reservoir theory. Adv Water Res (xxxx)]. The discharge and recharge zones transit time pdfs were then derived by applying the reservoir theory (RT) to the global system, thus considering as ensemble the union of all inlet boundaries on one hand, and the union of all outlet boundaries on the other hand. The main advantages in using the RT to calculate the transit time pdf is that the outlet boundary geometry does not represent a computational limiting factor (e.g. outlets of small sizes), since the methodology is based on the integration over the entire domain of each age, or life expectancy, occurrence. In the present paper, we extend the applicability of the RT to sub-drainage basins of groundwater reservoirs by treating the reservoir flow systems as compartments which transfer the water fluxes to a particular discharge zone, and inside which mixing and dispersion processes can take place. Drainage basins are defined by the field of probability of exit at outlet. In this way, we make the RT applicable to each sub-drainage system of an aquifer of arbitrary complexity and configuration. The case of the well-head protection problem is taken as illustrative example, and sensitivity analysis of the effect of pore velocity variations on the simulated ages is carried out.     

RTK技术在工程测量中几种作业方法的创新探讨

GPS有两种情况无法直接设站观测：一是GPS在待测点不能接收到卫星信号或信号不全,如高压电杆下、房沿下及隐蔽的钻孔等;二是GPS仪器或作业人员无法或不方便到达的待测点,如水中电杆及小煤窑井口。对于煤炭地质勘探中的测量误差,来源于RTK测量仪器本身的误差很小,源于距离交会法的误差主要是钢尺或皮尺丈量误差及位置标定误差,源于方向交会法的误差主要是瞄准误差。多个勘探区实际观测数据表明,使用钢尺量距的距离交会法其点位误差均不超过10cm,方向交会法的点位误差也能控制在20cm以内。