磁张量梯度数据方向解析信号比值的边界识别和空间位置反演方法

磁张量梯度测量具有高分辨率、多参量的优点,能更准确地描述磁源体的分布特征,在矿产资源勘探中具有广阔的用途.磁异常解析信号具有受倾斜磁化干扰小的特点,且为了增强深部地质体的分辨能力,本文提出磁张量梯度数据的解析信号比值的均衡边界识别及空间位置反演技术.磁张量梯度数据的均衡边界识别方法为不同方向解析信号比值的反正切函数,在降低倾斜磁化干扰的同时能有效地均衡不同深度地质体的响应,提高了对较深地质体的分辨率;空间位置反演技术是建立解析信号比值与地质体位置参数的对应方程,利用解析信号比值与地质体的对应关系作为约束条件来反演获得地质体的水平位置和深度信息,具有无需已知任何先验信息的优势.通过磁性体张量异常试验表明解析信号比值的边界识别方法能清晰和准确地获得不同深度地质体的边界,所建立的反演方程能准确地计算出地质体的范围和深度,具有较高的水平分辨率和精度.将本文方法应用于实测磁张量梯度数据的解释,获得了地下铁矿的分布特征,为区域矿产资源潜力评价提供了翔实的基础资料.     

分布式电磁法仪器系统设计及实现

本文介绍一种采用大功率稳流发射、低噪声测量、宽频带接收以及分布式同步等技术,自主研制的分布式多功能电磁法仪器系统.系统包括大功率电磁法发射机、分布式电磁法接收机、磁场传感器、整流源等设备.采用ARM芯片和FPGA芯片进行发射机的整机控制和信号整形发射,采用PC104工控机和FPGA芯片进行接收机的整机控制和信号处理.在人工场源模式下实现了可控源音频大地电磁法（CSAMT）、谱激电法（SIP）和时域激电法（TDIP）等测量功能;在天然场源模式下实现了大地电磁法（MT）、音频大地电磁法（AMT）的测量功能.发射机在满功率发射的情况下连续可靠运行时间大于12 h,接收机的动态范围大于120 dB,接收机可接收信号频率范围是0.001 Hz~32 kHz.通过典型矿区的野外实验和应用,表明本系统的性能总体上达到了国际先进水平.     

秒采样精度下磁暴急始自动拾取方法研究

磁暴急始的自动识别拾取与磁暴报告自动产出是国家地磁台网数据产品产出中重要的内容。为实现在1s采样率下的磁暴急始高精度拾取,本文针对性地提出基于Walsh变换和Akaike信息准则(AIC)的起跳点检测算法——Walsh-AIC算法,将其应用于98个磁暴急始事件的拾取上,并采用由国际地磁指数服务(ISGI)发布的磁暴时刻为标准对应用效果进行评估。结果表明,该算法不仅能够将急始磁暴起跳时刻的位置更加明显地刻画出来,而且能够有效避免传统识别急始磁暴的AIC算法中存在的识别起跳时刻结果晚于实际起跳时刻的情况。同时,将Walsh-AIC算法与其他主流拾取方法进行对比,发现前者定位结果的平均偏差和标准差均明显小于其他算法。此外,Walsh-AIC算法结果的误差关于0点的对称性较好,表明该算法拾取磁暴急始起跳时刻的精度较高,适合于解决磁暴急始的自动拾取问题。     

海南文昌涣文村老红砂剖面的磁化率测量及意义

通过对海南文昌县涣文村老红砂剖面的野外调查和磁化率测量, 绘制了该剖面磁化率曲线; 分析了剖面磁化率特征与剖面颜色及红化过程的关系。指出剖面磁化率可以作为反映老红砂堆积过程中(及以后)气候变化的物理参数。开展老红砂堆积连续剖面的磁化率测量, 以此进行气候地层的划分与对比, 对华南沿海乃至更大范围环境变化的研究具有重要意义     

Source of the Bicester magnetic anomaly

The Bicester magnetic anomaly is one of several high wavenumber features superimposed on the magnetic anomaly associated with the London Platform. Seismic reflection data suggest that the source of the Bicester anomaly is a body of basaltic rocks of Carboniferous age that can be traced from the Steeple Aston borehole. Three-dimensional interpretational techniques indicate that the magnetic source has a total magnetization vector dipping at 60°, azimuth 170°, with an intensity of 1.39 A m⁻¹ and this has been used to derive a three-dimensional model of the source. The nature of the magnetic remanence contributing to this vector is discussed. A detailed two-dimensional magnetic model has been constructed using the seismic control.     

高原地区不同坐标系及投影面引起的面积误差

讨论了高原地区北京坐标系和地方坐标系的高斯投影及不同高程投影面引起的面积变形,得到了不同高程投影面与高斯面上的面积误差,指出了高原地区面积最接近实际面积的坐标系就是边长变形最小的地方坐标系。     

On the theory of translationally invariant magnetohydrodynamic equilibria with anisotropic pressure and magnetic shear

We present an improved formalism for translationally invariant magnetohydrodynamic equilibria with anisotropic pressure and currents with a field aligned component. The derivation of a Grad-Shafranov type equation is given along with a constraint which links the shear field to the parallel pressure. The difficulties of the formalism are discussed and various methods of circumventing these difficulties are given. A simple example is then used to highlight the methods and difficulties involved.     

Nuclear magnetic resonance study of the formation and dissociation process of nature gas hydrate in sandstone

In this work, the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance (NMR) relaxation time (T₂) and 2D imaging measurement. The result shows that the intensity of T₂ spectra and magnetic resonance imaging (MRI) signals gradually decreases in the hydrate formation process, and at the same time, the T₂ spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate. The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity. Significantly, for the sample with lower porosity and higher argillaceous content, the intensity of the T₂ spectra also shows a trend of a great decrease in the hydrate formation process, which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content. The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.©2022 China Geology Editorial Office.     

http://www.sciencedirect.com/science/article/pii/S1674987114001303

We show the presence of fractal ordering of copper grade in bore core data at short range in the Cadia Ridgeway porphyry deposit and measure its persistence after mining by monitoring the output of the...     

大区域现代地籍测量基准的应用技术探讨

现代地籍测量主要体现在测量技术手段先进,成果丰富,大区域管理,小区域使用;本文以河南省地籍调查全省统一测量基准的应用和各县市地方平面基准系统建立为例,探讨分析大区域地籍测量基准建立和应用的技术方法。