三分量磁通门磁变仪探头正交误差对定向的影响

本文分析了磁通门磁变仪探头三分量正交度误差对定向的影响并提出了减小其影响的措施。     

磁通门磁变仪定向状态函数的稳定性分析

在地磁观测中 ,磁变仪的稳定性是基本要求。磁通门磁变仪的稳定性依赖于电子反馈、补偿线路的稳定性和磁通门磁变仪定向状态函数的稳定性。本文对后者进行讨论。1　磁通门磁变仪的定向要求磁通门磁变仪的定向就是使传感器线圈轴方向与被测磁场方向一致。设磁通门 3个探头线圈分别与定向方向 X、Y、Z间有微小差角 ,省略电子放大部分 ,忽略温度影响 ,有(周锦屏等 ,1 999)TX =X0 + SXn X=X + tanε* Y + tanβX* Z ( 1 )TY=Y0 + SYn Y=Y + tanδ* X + tanβY* Z ( 2 )TZ=Z0 + SZn Z-Z + tanθX* X + tanθY* Y ( 3 )其中 X0 ,Y0…     

自动化磁通门经纬仪测量误差仿真

目前绝对地磁观测中磁偏角(D)和磁倾角(I)的观测仍然依靠人工,为了实现绝对地磁观测的全面自动化,本文针对研制中的自动化磁通门经纬仪进行了测量误差仿真分析.文中利用多体系统理论对自动化磁通门经纬仪的传感器输出直接进行建模,基于磁通门经纬仪的测量特点,使用计算机仿真直观展示了仪器装配和运行过程中的各类误差对测量误差的影响.从仿真结果可以看出,测量磁偏角D时,竖轴晃动误差影响最大,磁轴不正交误差和横轴晃动误差影响次之,横轴倾斜误差没有影响;测量磁倾角I时,磁轴不正交误差影响最大,竖轴晃动误差和横轴晃动误差影响次之,横轴倾斜误差影响最小.     

磁通门磁变仪与经典磁变仪状态函数之比较

分析了影响磁通门磁变仪定向状态函数和经典磁变仪定向状态函数改变的因素，对磁通门磁变仪定向状态函数和经典磁变仪定向状态函数及其稳定性进行了比较，得出了有益的结论。     

变倾角磁异常化极方法

磁异常化极是磁测资料处理和解释的重要基础,在大面积磁法测量及编图工作中,测区内磁纬度的变化范围很大,多个图幅资料只采用单一的磁倾角作化极处理显然是不合理的,必须考虑变磁倾角的处理方法.本文针对这一问题,改进常规的化极实现途径,尝试了在频率域进行大区域逐点变磁倾角实现化极的方案.理论模型和实际资料均表明,该方法在磁倾角变化范围很大的情况下,数值恢复精度比传统方法有较大提高,对目前大面积矿产资源磁法勘探资料连片处理具有实际意义.     

三轴磁通门探头球型反馈线圈的设计方法研究

长周期大地电磁测量要求三轴磁通门传感器具有低的噪声水平及高稳定性,根据实际需求设计一个尺寸合适的球型反馈线圈可以有效提高反馈磁场的均匀性,进而降低磁通门传感器的噪声水平.本文首先分析了非均匀反馈磁场引入磁通门噪声的机理,然后根据毕奥-萨伐尔定律和矢量叠加原理,以等间距多个单匝线圈构成单轴绕组的形式,建立了球型反馈线圈轴线上的轴向磁场分布及磁场均匀度数学模型,在给定磁场均匀度和球型反馈线圈直径的条件下,运用控制变量法确定了球型反馈线圈的单匝线圈数量和间距等关键结构参数.我们把设计的结构参数代入球型空间磁场分布数学模型,验证了本设计方法的正确性.最后,按照设计的结构参数制作了基于球型反馈线圈磁通门探头的三轴磁通门传感器,通过与体积相近的基于亥姆霍兹型反馈线圈磁通门探头的三轴磁通门传感器对比测试噪声水平,结果表明球型反馈线圈磁通门探头能够使得三轴磁通门传感器具有更稳定和较低的噪声水平.     

磁通门磁变仪状态函数的测定与记录的校正计算

对磁通门磁变仪状态函数的测定方法进行了研究，提出了磁通门磁变仪标度值——状态函数的测定和磁通门磁变仪记录的校正计算方法。     

环境对磁通门磁变仪定向影响的分析

磁通门磁变仪实际工作在弱铁磁环境。本文分析了弱铁磁环境等对磁通门磁定仪定向的影响，得出了弱铁磁影响等环境中磁通门磁变仪准确定向的方法。     

三分量磁通门磁变仪和经典磁变仪记录的比较

对磁通门磁变仪和经典光记录磁变仪记录进行比较分析。认为可以用磁通门磁变仪记录和处理日常数据。用经典磁变仪来判断和改正磁通门磁变仪的记录错误。     

磁偏角变化对垂直分量磁变仪记录影响的实验

实验证实了磁偏角变化对垂直分量磁变仪记录有影响。对于磁南北向布局中的垂直分量磁变仪，Ｚ磁针偏离定向位置θ０＝０越远，磁偏角变化对垂直分量磁变仪记录的影响越大。认为应重视垂直分量磁变仪遥定向工作并有必要提高垂直分量磁变仪磁针稳定性。     

首都圈地区地震重力测量数据的统一处理与分析

对首都圈地区由不同施测单位用不同仪器或不同方法获得的三组重力测量数据，通过绝对和相对测量的联合平差、相对测量结果的系统差消除，建立起绝对的、统一的重力时变体系；在此基础上分析了非构造因素地壳沉降的影响，并进行了测点位移改正，消除了长波干扰；实现了绝对和相对测量方法优势互补、消除矛盾和环境干扰、扩大信息量、加密时域采样间隔等目的，提高了识别构造活动过程的能力．结果表明，两组相对测量数据之间以及其中的10期观测资料中存在系统误差，研究区东南部的非均匀性局部地壳下沉导致10个点重力值线性上升，本文用回归分析的方法进行了改正．改正后的重力时变图对1995年10月6日古冶5.0级地震有明显而完整的反映．      

Evaluation of statistical tropospheric scintillation models using SUPERBIRD-C satellite for Malaysia

The main purpose of this paper is to evaluate and compare some of the statistical tropospheric scintillation models for one-year data (1999–2000) measured using SUPERBIRD-C satellite in Tronoh, Malaysia. Eight statistical models of monthly mean scintillation intensity are briefly reviewed and their predictions compared with measurements. Results are discussed in order to understand the potentials and the limits of each prediction model within this case study. In the context of our measurements, the Karasawa and Ortgies-T models have the best overall performance. The agreement with satellite measurements is found to be mainly dependent on the parameterization of prediction models to the radiometeorological variables along the earth-space path.     

Aerosol extinction and ozone measurements

The effect of aerosol extinction on Dobson measurements of total ozone is investigated, and several recent attempts to resolve this problem are reviewed. It is pointed out that the balloon measurements of Paetzold and his colleagues circumvent this problem: Solar-cycle and quasi-biennial effects can be clearly discerned in the balloon data. It is suggested that Paetzold's data would be ideal for testing stratospheric models and searching for man's effect on the stratospheric ozone layer.     

Sensitivity analysis of sediment flux derived by laser diffraction and acoustic backscatter within a reservoir

A combination of two indirect methods to measure sediment flux is presented in this study to evaluate suspended sediment transport in a hydropower reservoir. The acoustic backscatter signal (ABS) from an Acoustic Doppler Current Profiler (ADCP) is therefore applied in pre-defined transects within the reservoir in combination with a Laser In-Situ Scattering Transmissometry – stream lined device (LISST-SL). The stationary LISST-SL derived suspended sediment concentration (SSC) measurements are used to calibrate the ABS. From the LISST-SL measurements a time series of SSC is obtained. This enables, in addition, a comprehensive data analysis to evaluate the influence of natural fluctuations of the SSC on the calculated sediment flux, which should be taken into account when assessing sediment transport. Furthermore SSC measurements are done with the LISST-SL close to the reservoir bed. In areas close to the bed no information regarding the ABS is available from the ADCP measurements due to the side-lobe interference. In various studies the information from the last three valid cells is used for extrapolation. However, as result of a comparison of the LISST-SL measurements with extrapolated SSC values from the ADCP measurements it can be seen that, especially in deep reservoirs, this method has to be adapted to the in-situ conditions.     

Joint processing and analysis of seismic gravity measurements in Capital Circle area

In Capital Circle area, there are three groups of repeated gravity measurements observed by different institutes using different instruments or methods. The simultaneous adjustment of absolute and relative measurements and the elimination of systematic error among the relative measurements have been carded out in this paper. Thus an unified temporal gravity change system with absolute reference has been established. On the basis of this, the crustal subsidence effect on gravity, which belongs to non-tectonic factor, is analyzed and the station displacement corrections are carried out, so that the long-wave disturbance is eliminated. So far our following aims are realized： the advantages of the absolute and relative measurement methods are complementary to each other; the contradiction and environment disturbance are eliminated; the amounts of information are enlarged; the sampling interval of time domain is compressed. In a word, the ability of identifying the tectonic activity process is enhanced. The results show that： there are systematic errors between the two groups of relative measurements and within the data of 10 campaigns ; the uneven local crustal subsidence in the southeast of the study area results in a linear rise of gravity value at 10 stations; they can be corrected by the regression analysis. The maps of revised temporal gravity change can obviously and integrally reflect the Ms=5.0 earthquake in Guye on October 6, 1995.     

Use of steady-state concentration measurements in geostatistical inversion

In geostatistical inverse modeling, hydrogeological parameters, such as hydraulic conductivity, are estimated as spatial fields. Upon discretization this results in several thousand (log-)hydraulic conductivity values to be estimated. Common inversion schemes rely on gradient-based parameter estimation methods which require the sensitivity of all measurements with respect to all parameters. Point-like measurements of steady-state concentration in aquifers are generally not well suited for gradient-based methods, because typical plumes exhibit only a very narrow fringe at which the concentration decreases from a maximal value to zero. Only here the sensitivity of concentration with respect to hydraulic conductivity significantly differs from zero. Thus, if point-like measurements of steady-state concentration do not lie in this narrow fringe, their sensitivity with respect to hydraulic conductivity is zero. Observations of concentrations averaged over a larger control volume, by contrast, show a more regular sensitivity pattern. We thus suggest artificially increasing the sampling volume of steady-state concentration measurements for the evaluation of sensitivities in early stages of an iterative parameter estimation scheme. We present criteria for the extent of artificially increasing the sampling volume and for decreasing it when the simulation results converge to the measurements. By this procedure, we achieve high stability in geostatistical inversion of steady-state concentration measurements. The uncertainty of the estimated parameter fields is evaluated by generating conditional realizations.     

Some results of aerosol measurements

Summary In brief a newly developed freezing nuclei meter is described. Results of measurements made with this instrument in New Jersey, California and in the Thule area, Greenland, are shown. These data are compared with measurements of condensation nuclei, simultaneously made with the General Electric and the Aitkennuclei counters. Also the results obtained from some measurements of the lightscattering function of the aerosol in industrial areas near New York City are presented.     

In situ measurements of surficial mud strength: A new vane tester suitable for soft intertidal muds

A vane fitted to a standard shear vane tester is described, the purpose of which is to obtain better measurements of the rheological properties of soft, surficial, intertidal muds (and consequently, variations in their erodability). Specifications and geometry of this vane are presented. The computation procedure is detailed, so that the methodology can be applied to any vane tester. The main improvement is a greater vertical resolution, typically less than 1 cm. Sets of direct measurements with this equipment and correlation with dry densities for three intertidal mudflats (estuaries and bay) are presented.     

TEST OF RECIPROCITY AND SUPERPOSITION IN TIME DOMAIN INDUCED POLARIZATION MEASUREMENTS*

The principles of reciprocity and superposition, which hold in normal resistivity measurements, are sometimes considered to apply also to Induced Polarisation measurements. In this paper, an account is given of experiments designed to test how far such a proposition is justified. The experiments comprise a limited field test and more extensive observations using a tank analogue. Within acceptable limits, both tests showed that these basic theorems are applicable to I.P. potentials provided that these are measured at the same instant after switch off and that identical charging regimes are used. The implications of these findings are discussed.     

Developing multimetric indices for monitoring ecological restoration progress in salt marshes

Effective tools for monitoring the status of ecological restoration projects are critical for the management of restoration programs. Such tools must integrate disparate data comprised of multiple variables that describe restoration status, including the condition of environmental stressors, landscape connectivity, ecosystem resilience, and ecological structure and function, while communicating these concepts effectively to a wide range of stakeholders. In this paper we describe the process of constructing multimetric indices (MMIs) for monitoring restoration status for restoration projects currently underway on the eastern coast of Saudi Arabia. During this process, an initial suite of measurements is filtered for response and sensitivity to ecosystem stressors, eliminating measurements that provide little information and reducing future monitoring efforts. The retained measurements are rescaled into comparable domain metrics and assembled into MMIs. The MMIs are presented in terms of established restoration theories, including restoration trajectory and restoration endpoint targets.