关于精密地形改正的若干注记

引用斜率作为新的变量，首次使地形改正一类奇异积分非奇异，并在此基础上详细讨论了精密地形改政计算的若干技术问题，地形模型和某山区的试算结果均表明，以往线性近似误差较大，应避免使用。     

重力勘探地形改正最大半径的选择

重力勘探地形改正半径偏小,会降低资料的可信度;地形改正半径过大,则会造成人力、财力的浪费。通过地形改正数学物理模型的建立,提出了地形改正最大半径的选择方法。      

方域重力近区地形改正实测方法研究

介绍了采用“方域”方案时,在一般地形条件下求取近区重力地形改正值的公式和实测方法。讨论了沟渠、堤坝、路基等特殊地形情况下的地形改正与实测方法及其优越性。提出了判断是否进行地形改正实测及改正范围的原则。     

基于VC~( )的重力近中区地形改正可视化程序设计

从传统的重力地形改正方法入手,用VC~( )语言编制了重力地形改正可视化程序。它能用于重力近中区地形改正,并能满足重力地改的精度要求,使得多年来重力近中区地形改正繁重的手工数图工作能够用计算机完成,且计算精度和速度得到明显提高。通过人机对话的形式(操作界面),可直接计算出近、中区的地形改正值。     

航空伽玛能谱测量地形改正方法初探

航空γ能谱测量资料解释中,地形影响改正是人们关心的问题之一.常规的地形改正方法只能对测量剖面进行基于二维空间的修正,未考虑其它方向地形变化的影响.本文针对这一特点初步探讨了一种三维地形改正方法--角度扇形改正.方法从锥台状辐射体照射量率基本计算出发,将作用范围内的地形辐射体按角度划分为若干环形,然后对各环按照同样的规律细分为若干个小的扇形辐射体,分别计算各小辐射体对修正点的照射量率,求和并计算出相应的地形改正系数,进而对空中测点进行地形影响改正,从而实现任意地形、任意飞行方式下的航空γ能谱测量的三维正演、反演及地形影响改正等计算,同时还考虑了范围不饱和、地面辐射体中放射性元素含量不均匀等因素.正演模型和实例分析在一定程度上说明该三维地形改正方法的正确性和有效性.     

航空伽马能谱测量地形影响改正实现方法

航空伽马能谱测量受地形因素影响较大,采用常规高度改正方法对复杂地形条件下的航空伽马能谱数据进行改正,会造成结果失真。笔者结合航测动态测量特点,论述了利用航测过程中获得的地形数据,对作用带内的地形进行细化,应用点状辐射体辐射场理论,采用地形校正系数对航空伽马能谱数据进行地形影响改正的具体实现方法;通过实测的航空伽马能谱数据对该方法进行检验,并与地面异常查证的结果对比,表明该地形改正方法效果较好,基本能消除地形起伏对测量结果产生的影响。     

基于Matlab的吉林省大地水准面精化重力归算

基于Matlab平台,采用严格棱柱积分法和谱方法编程计算了吉林省大地水准精化重力归算,以长白山、吉林和松原地区为试验区分析了计算精度和速度。结果表明,不完全布格改正与地形高度成正比。地形改正的谱方法比组合法计算速度高,但精度较低,最大误差分别为2. 65 mgal和0. 21mgal。均衡改正的谱方法比组合法计算速度高,精度基本相同,平均误差分别为0. 02 mgal和0. 03mgal。地形改正分辨率达到30″时,内插精度优于1 mgal,而均衡改正分辨率为1'时,精度即可优于1mgal,不完全布格改正、地形改正和均衡改正的数值大小与地形复杂程度密切相关。     

三角平面拟合法在重力地形改正中的应用

介绍了三角平面拟合法在重力勘查近中区地形改正中的应用。该方法应用三角平面拟合通过地形图DEM模型数据（或散点模型数据）直接内插求得地形改正量板模型的结点高程数据,实现了地形改正的电脑化作业。     

重力近区地形改正精度探讨

在大比例尺重力勘探工作中,近区、中区地形改正误差对重力总精度影响较大。在实际工作中,近区域地形改正一般采用实测或用地形图读图计算;中区地形改正一般采用地形图读图计算,《大比例尺重力勘查规范》只考虑地形图高程精度对重力总精度的影响,忽略了地形图平面坐标精度对重力总精度影响。这里从锥形、扇形基本地形改正公式推导出发,探讨不同比例尺,不同高程,平面精度对重力总精度的影响,并提出了不同地形改正精度对地形图比例尺及高程,平面精度要求建议。     

边界单元法在高密度电阻率法二维地形改正中的应用效果

给出了高密度电阻率法二维地形改正的边界元数值解法及其探测地下煤气管道时进行二维地形改正的应用实例。     

利用H2O-NaCl-CaCl2体系水盐化合物和冰的融化温度计算NaCl/（NaCl＋CaCl2）比值和盐度的方程

The composition of fluid inclusions in the H_2O-NaCl-CaCl_2 system has been generally graphically estimated using the melting temperatures of hydrohalite(T_(m-HH))and ice(T_(m-ice)).Here we present two equations that can be used to calculate the relative proportion of NaCl(i.e.,NaCl/[NaCl CaCl_2],or X_(NaCl))and the total salinity( i.e.,NaC1 CaC12,wt% )for fluid inclusions with ice as the last melting phase.X_(NaCl)can be calculated from T_(m-HH)using the following equation: y=(a bx)~(-1/c) where y is X_(NaCl),x is T_(m-HH),a=0.33124402,b=-0.031518028,and c=0.22932736.In the cases where only T_(m-ice)is measured and T_(m-HH)is not known,T_(m-ice)can be used as the maximum possible TIn.nil to calculate the maximum value of X_(NaCl)using the above equation.In these cases,the following equation can be used to calculate the maximum total salinity: y=(a bx cx~2)~(-1) where y is salinity,x is T_(m-HH),a=0.057184817,b=0.00078565757,and c=5.7262766E-6.Because the isothems in the field of ice are sub-parallel to the NaCl-CaCl_2 binary side in the H20-NaC1-CaC12 ternary system,the errors in salinity calculation introduced by the above approximation are small(less than 2 wt% ).A Windows program for calculation of X_(NsCl)and salinity is available at: http://uregina.ca/～chiguox.     

小波变换在河西地区水文和气候周期变化分析中的应用

小波时—频分析由于其局部优化性质而优于傅立叶分析。应用 Meyer小波 ,对甘肃河西地区近 50 a来年径流量、年降水量和年平均气温做周期分析 ,发现河西地区水文气象序列的变化周期基本在 35a、2 2 a、1 1 a、5～ 6a和 2～ 3a左右的时间尺度上浮动。而这些基本周期正是太阳黑子活动周期或海—气相互作用的周期 ,说明河西地区水文、气象序列的周期变化受天体运动变化的影响。天体运动直接影响降水和气温的周期变化 ,进而在一定的下垫面条件下 ,影响径流的周期变化。     

铬天青S光度法及非线性拟合测定高纯硅中微量铝

铬天青S光度法是硅中铝含量的测定方法之一,该方法的标准曲线大多采用不过零点的线性拟合,导致低铝含量测定误差大。为提高方法准确度并降低方法检出限,研究了铝标准曲线低浓度部分的拟合问题,探讨了不同拟合模型对检测结果准确度的影响。实验结果表明,不同浓度铝标准液的吸光度在0~0.3 μg/mL范围内并不满足一次函数线性关系,采用三次函数关系y=-17.45230x³+10.42883x²+1.04047x (y为扣空白的吸光度,x为铝的质量浓度)拟合能获得良好结果,其相关系数R²为0.99975。利用已知铝含量的硅试液检验该公式,其相对标准偏差(RSD)为2.55%。样品中铝的测定值与电感耦合等离子体发射光谱法测定值吻合。该法可以显著提高低浓度的铝测定的准确性,可用于测定高纯硅中含量在0.55 μg/g以上的铝杂质。     

求解半无限长多孔介质柱体水动力弥散系数的一种最小二乘法

针对半无限长多孔介质柱体,一端为定浓度边界的水动力弥散反求参数问题,先用数值方法求解补余误差函数erfc（x）的反函数,再根据该问题的解析解,通过变量代换,构造一个基于解析解的最小二乘模型来反求水动力弥散系数。最后将该方法应用于一个实例,计算结果表明该方法比erfc（x）近似公式法、配线法、正态分布函数法等传统方法要好。     

A Note on Robust Estimates

It is well known that the mean can be an unsatisfactory estimator of a true value if data are a poor approximation to a normal distribution or are too few in number for a normal distribution to be adequately delineated. Unfortunately, this knowledge is not always implemented in the evaluation of analytical data. The median may be used occasionally because it is recognised to be less affected by discrepent data. However, there are other 'robust' estimators which can be better than the simple median. This note complements a previous paper by the writer (1).     

Foundations of cable car towers upon alpine glaciers

This paper presents a design approach for strip footings upon glacier ice. Safety against ultimate limit state is proved by the geotechnical slip-line field solution by Prandtl. Glacier ice at 0°C can be modelled as purely cohesive material. Statistical evaluation of uniaxial compression tests with high strain rate revealed a mean value of the cohesion of 600 kPa and a characteristic value c _k = 355 kPa (5% fractile). With a coefficient of variation V _c = 0.3, the partial safety factor turns out to be γ _c = 1.9. An approximate solution for estimating the creep settlement rate is presented to check the serviceability limit state: with the width b of the strip foundation, p the foundation pressure and for ice at 0°C. Experiences on Stubai glacier with grate shaped footings showed that creep settlements occurring per year due to maximum foundation pressures 250 kPa did not influence the operation and the maintenance of the cable cars.     

化学沉积过程中元素间线性关系的研究──以盐类沉积为例

本文研究了半封闭体系的盐类化学沉积过程。在获得单个元素浓度变化规律的基础上，推导了元素间线性关系的数学模型。提出元素定性分配系数和定量分配系数概念，给出元素拟合直线截距和斜率的地球化学意义，并讨论了制约元素间关系的影响因素。最后给出了应用实例。     

The concept of geochemical potential field exemplified by ore formation field

Geochemical potential field is defined as the scope within the earth’s space where a given component in a certain phase of a certain material system is acted upon by a diffusion force, depending on its spatial coordinatesX, Y andZ. The three coordinates follow the relations: $$NF_{ix} = - \frac{{\partial \mu }}{{\partial x}}, NF_{iy} = - \frac{{\partial \mu }}{{\partial y}}, NF_{iz} = - \frac{{\partial \mu }}{{\partial z}}$$ The characteristics of such a field can be summarized as: (1) The summation of geochemical potentials related to the coordinatesX, Y, Z, or pseudo-velocity head, pseudo-pressure head and pseudo-potential head of a certain component in the earth is a constant as given by $$\mu _x + \mu _y + \mu _z = c$$ or $$\mu _{x2} + \mu _{y2} + \mu _{z2} = \mu _{x1} + \mu _{y1} + \mu _{z1} $$ Derived from these relations is the principle of geochemical potential conservation. The following relations have the same physical significance: $$\mu _k + \mu _u + \mu _p = c$$ or $$\mu _{k2} + \mu _{u2} + \mu _{p2} = \mu _{k1} + \mu _{u1} + \mu _{p1} $$ (2) Geochemical potential field is a vector field quantified by geochemical field intensity which is defined as the diffusion force applied to one molecular volume (or one atomic volume) of a certain component moving from its higher concentration phase to lower concentration phase. The geochemical potential field intensity is given by $$\begin{gathered} E = - grad\mu \hfill \\ E = \frac{{RT}}{x}i + \frac{{RT}}{y}j + \frac{{RT}}{z}K \hfill \\ \end{gathered} $$ The present theory has been inferred to interpret the mechanism of formation of some tungsten ore deposits in China.     

First approximation sea-level dependent mathematical model for volume eroded and submarine profile development in a semienclosed sea: Kiel Bay,Western Baltic

Given a marine basin of near homogeneous lithology, a known sea level curve, and known submarine abrasion rates, a model is developed to estimate the volume of material eroded by marine action. Assumptions of the model are that erosion is effected solely by submarine abrasion, which is assumed known and uniform through time, and that the volume eroded is small relative to the total volume of the basin. The basis of the model is that the volume eroded V, between time limits t₁ andt ₂,is essentially a function of the perimeter length l of the basin, which in turn is time-dependent on the sea level curve, so that $$V = k\int_{t1}^{t2} {l(t)dt} $$ where k is an abrasion rate constant. The model was tested on Kiel Bay, Western Baltic, a shallow semienclosed, essentially nontidal sea, for which considerable data is available. Critical for numerical integration of the model is the k value, representing the volume eroded from the shore normal profile per unit length of shoreline per year. A number of possible k values were utilized, the most likely realizing a total volume eroded over the past 9000 y, since the sea first entered Kiel Bay, of 2.60×10⁹ m ³. From this model, long-term average vertical submarine abrasion rates for Kiel Bay can be deduced as being between 0.001 and 0.0004 m/y. An extension to the model analyzes the effect of sea level transgression rate on whether cliffs develop and predicts the theoretical form of the submarine profile based on varying abrasion rates summarized as $$y_B (x) = \left\{ {\begin{array}{*{20}c} {h({x \mathord{\left/ {\vphantom {x {V_c }}} \right. \kern-\nulldelimiterspace} {V_c }}) - a_T (x) for x > 0;} \\ {x\tan \theta - a_T (x) for x > 0.} \\ \end{array} } \right.$$ Here the origin x=0, y_B=0 is chosen horizontally at the position where cliff formation first occurs, and vertically at the sea level at that time. The coordinate x measures distance inshore from the origin, y_B(x) is the vertical position of the sea floor, a_T(x) is the total depth abraded, tanθ is the original land surface slope, V_c the rate of cliff retreat, and h(t) the sea-level at time t. The synthetic profiles are compared to actual erosional profiles from representative sectors of Kiel Bay. The model predicts cliff development began at about 5800 yB.P., resulting in submarine abrasion profile lengths of about 1740 m and cliff heights of about 17.4 m for original land surface slopes of 0.01. This agrees to within about 10% of mean values obtained from bathymetric and topographic maps.     

An objective replacement method for censored geochemical data

Geochemical data are commonly censored, that is, concentrations for some samples are reported as less than or greater than some value. Censored data hampers statistical analysis because certain computational techniques used in statistical analysis require a complete set of uncensored data. We show that the simple substitution method for creating an uncensored dataset, e.g., replacement by3/4 times the detection limit, has serious flaws, and we present an objective method to determine the replacement value. Our basic premise is that the replacement value should equal the mean of the actual values represented by the qualified data. We adapt the maximum likelihood approach (Cohen, 1961) to estimate this mean. This method reproduces the mean and skewness as well or better than a simple substitution method using3/4 of the lower detection limit or3/4 of the upper detection limit. For a small proportion of less than substitutions, a simple-substitution replacement factor of 0.55 is preferable to3/4; for a small proportion of greater than substitutions, a simple-substitution replacement factor of 1.7 is preferable to4/3, provided the resulting replacement value does not exceed 100%. For more than 10% replacement, a mean empirical factor may be used. However, empirically determined simple-substitution replacement factors usually vary among different data sets and are less reliable with more replacements. Therefore, a maximum likelihood method is superior in general. Theoretical and empirical analyses show that true replacement factors for less thans decrease in magnitude with more replacements and larger standard deviation; those for greater thans increase in magnitude with more replacements and larger standard deviation. In contrast to any simple substitution method, the maximum likelihood method reproduces these variations. Using the maximum likelihood method for replacing less thans in our sample data set, correlation coefficients were reasonably accurately estimated in 90% of the cases for as much as 40% replacement and in 60% of the cases for 80% replacement. These results suggest that censored data can be utilized more than is commonly realized.