磁偏角（D）的数据处理   总被引：2，自引：0，他引：2  

史勇军  孙燕萍 《内陆地震》1999,13(1):84-87

磁偏角观测数据既有东西方向的区别,又有数值大小的变化,由于喀仁台所处的地理纬度,其磁偏角方向偏东,观测工作就是要搞清磁照图上Ｄ与ＤＢ相对位置及Ｄ↑及Ｄ↓的物理意义;箭头表示磁场变化的向东偏的方向。在处理Ｄ观测数据时很容易发生混乱的错误,针对存在的问题,对数据处理展示了讨论。  相似文献   

Structural and magnetic properties of Co2Al4Si5O18 and Mn2Al4Si5O18 cordierite     

K. Knorr  M. Meschke  B. Winkler 《Physics and Chemistry of Minerals》1999,26(6):521-529

The crystal structures, lattice dynamics and magnetic properties of synthetic Co-cordierite, Co₂Al₄Si₅O₁₈, and Mn-cordierite, Mn₂Al₄Si₅O₁₈ have been studied by neutron powder diffraction, infrared spectroscopy and magnetisation measurements. Due to different synthesis conditions, the Co-cordierite used here crystallised in the hexagonal α-cordierite structure with a disordered Si/Al distribution in the framework, while for the Mn-cordierite the orthorhombic β-structure has been determined. The experimentally determined paramagnetic moments, _exp (Mn) = 5.47(6) _B and _exp (Co) = 3.88(4) _B , are in good agreement with theoretical predictions for octahedrally coordinated Mn²⁺ and Co²⁺, respectively. In both compounds there is no magnetic long-range order down to at least 1.5 K. However, the onset of an anti-ferromagnetic short-range correlation of magnetic moments along [001] has been observed for Mn-cordierite by magnetisation and neutron diffraction measurements. This short-range magnetic correlation becomes evident from diffuse scattering observed at 2 K. The diffuse scattering has been interpreted in terms of a Blech-Averbach function. Received: 30 June 1998 / Revised, accepted: 3 March 1999  相似文献   

磁变仪布局的研究     

朱兆才 《东北地震研究》1999,15(4):42-49

本文提出了改进磁变仪布局的必要性和布局标准,对磁变仪定向及其稳定性、标度值稳定性和分量仪间允许的最小间距进行了研究,提出了可以提高磁变仪记录质量的改进布局和满足布局全部标准的新布局,改进布局特别是新布局可以显著提高磁变仪保持定向、抗干扰能力,获得记录标度值稳定的较理想的磁照图。  相似文献   

1950—2000年中国地磁测量地磁图与地磁研究   总被引：7，自引：2，他引：5  

安振昌 《地球物理学进展》1999,14(4):75-88

为纪念“３９１２”建队三十周年,本文回顾了１９５０－２０００年中国地磁测量和地磁图,回顾了“３９１２”任务的光辉业绩,阐述了“３９１２”任务的学术意义和应用价值。  相似文献   

GD—DTPA脊髓造影磁共振扫描技术应用的研究     

曾庆玉  霍建伟 《CT理论与应用研究》1999,8(1):21-25

本文目的,通过将ＧＤ－ＤＴＰＡ直接注入蛛网膜下腔后进行脊髓造影ＭＲ扫描,探索一种新的ＭＲ检查方法,材料方法：对１１例患者进行ＧＤ－ＤＴＰＡ蛛网膜腔直接注射脊髓造影前后ＭＲ扫描,保持扫描序列不变。造影剂量为０．５～１．０ｍｌ,结果：所有患者脊髓造影后即刻扫描显示脑脊液信号反转,Ｔ１Ｗ高信号。Ｔ２Ｗ低信与,结论：小剂量ＧＤ－ＤＴＰＡ直接蛛网膜注射脊髓造影ＭＲ扫描是一种安全可靠的检查方法。对观察脑脊液动  相似文献   

核磁共振技术应用的新领域——探查地下水     

潘玉玲  张昌达 《CT理论与应用研究》1999,8(4):5-8

利用核磁共振（ＮｕｃｌｅａｒＭａｇｎｅｔｉｃＲｅｓｏｎａｎｃｅ缩写为ＮＭＲ）技术探查地下水仅有二十多年的历史,文中简要介绍了ＮＭＲ找水方法的发展状况,原理和方法特点,重点介绍了中国地质大学（武汉）利用ＮＭＲ找水方法在中国一些地区找水取得的成效,最后指出了ＮＭＲ找水方法的发展趋势。  相似文献   

Evidences of the Blake and Iceland Basin magnetic excursions in southeastern Iberia and chronological implications for the Padul sedimentary record     

《Quaternary Geochronology》2023

The Padul-15-05 sediment core provides an exceptional perspective of the paleoenvironmental and climate change in the Western Mediterranean region for the last ca. 200 kyr. However, even though a robust chronology mainly relying on radiometric dating is available for the last 50 ka, the chronology for the older sediments is not yet fully resolved. Ages for the bottom part of the core (>21 m) were previously inferred from amino-acid racemization dating and sediment accumulation rates. In this work, we provide a more accurate chronology for the older part (>100 kyr) of the Padul-15-05 sediment core record based on the recognition of past Earth's magnetic excursions. We identify an interval prone of reversed polarity samples close to MIS-5e/5 d transition that we correlate to the Blake geomagnetic excursion (116.5 kyr–112 kyr). In addition, we identify an interval of low inclinations and two reversed samples that we interpret as the Iceland Basin geomagnetic excursion (192.7 kyr–187.7 kyr: wide scenario of VGP <40°). Our new results, which include IRM acquisition curves that contribute to understand the magnetic mineralogy, enhances the robustness of the age model for the Padul-15-05 sedimentary sequence by adding an independent age dataset with new accurate tie-points. Our refined age control together with the available paleoenvironmental and paleoclimate multiproxy data provide insightful information to unveil the response of the western Mediterranean environments to regional environmental and climate change.  相似文献   

Rapid magnetic susceptibility measurement as a tracer to assess the erosion–deposition process using tillage homogenization and simple proportional models: A case study in northern of Morocco     

《国际泥沙研究》2023,38(5):739-753

Soil erosion is a significant threat in the Rif region in northern Morocco. Hence, accurate cartography of the phenomenon, magnitude, and extent of erosion in the area needs a simple, rapid, and economical method such as magnetic susceptibility (MS). The current study aims to: (i) determine the factors influencing the variation of soil MS, (ii) exploit MS to estimate soil loss using two approaches in different homogenous units characterized by the same climatic conditions with different edaphic characteristics (land use, slope, and lithology), and (iii) highlight the potential for using MS as a cheap and rapid tracer of a long term erosion and deposition processes. Mass-specific magnetic susceptibility at low (χ_lf) and high (χ_hf) frequencies were measured for 182 soil samples collected in the study area. A tillage homogenization (T-H) model and a simple proportional model (SPM) were applied on an undisturbed soil profile to predict the eroded soil depths for given cores. The results confirm that χ_lf is influenced by land use, slope, and soil type. Pedogenesis is the main factor affecting soil MS enhancement, indicated by homogenous magnetic mineralogy with a dominance of super-paramagnetic (SP) and stable single domain (SSD) magnetic grains. The study results show that higher soil losses have occurred in almost all the soil samples when applying the T-H model compared to application of the SPM. The SPM underestimates erosion due to its ignorance of the MS of the plow layers after erosion. The current study implies the high efficacy of magnetic susceptibility as the quick, easily measurable, simple, and cost-effective approach that can be used as an alternative technique for evaluating soil redistribution.  相似文献   

地球磁尾等离子体片磁洞的统计分析   总被引：1，自引：1，他引：0       下载免费PDF全文

刘建坤  葛亚松  张铁龙  王国强  LYU Hao-Yu 《地球物理学报》2017,60(3):873-878

本文利用THEMIS卫星的磁场数据和等离子体观测数据,统计分析地球磁尾等离子体片区域线性磁洞的发生率、时空尺度、分布特征、和发生率与地磁AE指数的相关性.分析结果表明磁尾等离子体片区域的磁洞的时间尺度为几秒到几十秒,空间尺度小于当地的质子回旋半径.通过磁洞在空间的位置分布和卫星数据在空间的数据采样分布的对比,我们发现线性磁洞在等离子体片内经常发生,然而在磁尾等离子体片中的发生率要小于太阳风中磁洞的发生率.本文最后统计分析了磁洞发生和AE指数的相关性,结果表明磁洞可能与地磁活动有关系.  相似文献   

地下核磁共振小尺寸线圈设计和实验   总被引：1，自引：1，他引：0       下载免费PDF全文

林君  张健  易晓峰 《地球物理学报》2017,60(11):4184-4193

很多国家在进行隧道挖掘、地下矿体开采时,经常会遇到突水涌泥事故.核磁共振方法(Magnetic Resonance Sounding,MRS)作为目前唯一一种直接找水的地球物理技术,在探测诱发灾害的水体方面具有明显的优势.本文首先给出了多匝分离式线圈的MRS信号响应和核函数的计算公式,分析了线圈的匝数、边长和含水层位置对MRS信号响应的影响.分析表明,在限定空间内,利用多匝分离式线圈的设计方法可以提高小尺寸线圈的探测能力.同时,对高匝数线圈给探测系统带来的不利因素进行了分析和改进.最后,为了验证本研究所采用的方法,利用6 m边长的方形线圈和改进型MRS探测系统在中国温州一处在建隧道内的地下场地进行实地探测,探测结果与瞬变电磁方法结果对比表明,6 m边长的方形线圈可以对地下30 m内的含水层进行有效探测.  相似文献