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《地震地磁观测与研究》2016,(2)
为了解决地电阻率台站饱受环境干扰等问题,中国地震科技工作者致力于研究基于交流电法的新型电阻率观测系统,该系统主要由交流稳流电源和接收机组成。介绍电源研制过程涉及的SPWM驱动信号实现方法、高频变压器的设计方法等关键技术,并对电源样机进行输出性能测试。测试结果表明,电源样机的各项技术指标均达到设计要求,具有良好的输出性能。 相似文献
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引言我国地震系统数字化台网改造工作正在全面展开 ,不仅需要高质量的数字化地震观测仪器 ,提高观测质量 ;同样也需要一种适合遥测台工作特点的供电系统 ,提高遥测台地震观测仪器的连续运行率。在遥测台网的监测工作中 ,由于原有的电源不尽完善 ,不能完全适应遥测台的工作环境 ,造成地震信号断记的现象时有发生。一直是困扰遥测台网监测工作质量的一个难题。为此 ,我们研制了 LN-GDXT-1型多功能电源。LN-GDXT-1型多功能电源具有性能稳定 ,输入交流电压范围宽 ,停电时持续供电时间长 ,免维护等特点 ,是一种较为理想的遥测台供电系统。1… 相似文献
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广泛应用于我国地震台网上的 DJ-1型地震记录仪是一种交直流两用仪器 ,其外接直流电源普遍采用可以多次充放电的蓄电池。由于该仪器不具备自动充电功能 ,蓄电池的能量损耗需要根据实际使用情况不定期地进行人工补充。由于市电供、停的不规律 ,使蓄电池放电深度差异较大 ,补充电量不易掌握 ,从而导致充电不足或充电不及时引起蓄电池极板硫酸化、或因过充电造成蓄电池极板活性物质脱落而缩短其使用寿命。为了避免上述问题的发生 ,我们于 1 994年设计了一种 DJ-1型地震记录仪浮充电源。经河北电磁台网和地震台网等近 2 0台仪器长达几年时间的… 相似文献
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鉴于镍镉蓄电池存在售价偏贵、在中小城市购买困难等诸多弊病,近年来许多台站改用性价比较高、市场货源充足的铅蓄电池作为CZM-2型质子磁力仪电源。但是,由于铅蓄电池自放电率高,每个月至少要进行一次充电才能保证仪器正常工作和蓄电池的性能不受 相似文献
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首先从麦克斯韦方程出发,用伽里金方法推导了三维三分量CSAMT法的有限元方程.在研究过程中,认识到加入散度条件的必要性,在公式中强加了散度条件,提高了解的完备性.其次将成功应用于二维线源频率域电磁法有限元模拟中的两种技术推广到三维中,一是边界条件统一采用一阶吸收边界,使线源产生的电磁波在边界上按波的传播规律被吸收,以降低平面波假设造成的影响;二是总体系数矩阵的存储,用两个二维数组分别记录总体系数矩阵的非零元素及其在总体结点编号中所处的位置,使总体系数矩阵的存储量达到最小的同时,物理意义明确,迭代求解时迅速简便.最后用均匀半空间模型进行了验证. 相似文献
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J.M. Herndon M.W. Rowe E.E. Larson D.E. Watson 《Earth and Planetary Science Letters》1976,29(2):283-290
Thermomagnetic analysis was made on samples of all known C3 and C4 chondrites in a controlled oxygen atmosphere. Considerable variation was noted in the occurrence of magnetic minerals, comparable to the variation observed earlier in the C2 chondrites. Magnetite was found as the only major magnetic phase in samples of only three C3 chondrites (2–4 wt.%) and the Karoonda C4 chondrite (7.7 wt.%). The magnetite content of these three C3 chondrites is only about one-third that observed in the C1 and C2 chondrites which were found to contain magnetite as the only magnetic phase. Five C3 chondrites were observed to undergo chemical change during heating, producing magnetite: this behavior is characteristic of troilite oxidation. Upper limits on initial magnetite content of about 1–9% were established for these meteorites. Samples of the remaining five C3 chondrites and the Coolidge C4 chondrite were found to contain both magnetite and metallic iron. In two samples, iron containing ≤2% Ni was observed, while in the other four, the iron contained 6–8 wt.% Ni. In addition to containing both magnetite and iron metal, three of these samples reacted during heating to form additional magnetite. Variations in the magnetic mineralogy and, hence by inference bulk mineralogy, of C3 and C4 chondrites indicate a more complex genesis than is evident from whole-rock elemental abundance patterns. 相似文献
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Massimiliano Favalli Giuseppe D. Chirico Paolo Papale Maria Teresa Pareschi Enzo Boschi 《Bulletin of Volcanology》2009,71(4):363-374
The 2002 eruption of Nyiragongo volcano constitutes the most outstanding case ever of lava flow in a big town. It also represents
one of the very rare cases of direct casualties from lava flows, which had high velocities of up to tens of kilometer per
hour. As in the 1977 eruption, which is the only other eccentric eruption of the volcano in more than 100 years, lava flows
were emitted from several vents along a N–S system of fractures extending for more than 10 km, from which they propagated
mostly towards Lake Kivu and Goma, a town of about 500,000 inhabitants. We assessed the lava flow hazard on the entire volcano
and in the towns of Goma (D.R.C.) and Gisenyi (Rwanda) through numerical simulations of probable lava flow paths. Lava flow
paths are computed based on the steepest descent principle, modified by stochastically perturbing the topography to take into
account the capability of lava flows to override topographic obstacles, fill topographic depressions, and spread over the
topography. Code calibration and the definition of the expected lava flow length and vent opening probability distributions
were done based on the 1977 and 2002 eruptions. The final lava flow hazard map shows that the eastern sector of Goma devastated
in 2002 represents the area of highest hazard on the flanks of the volcano. The second highest hazard sector in Goma is the
area of propagation of the western lava flow in 2002. The town of Gisenyi is subject to moderate to high hazard due to its
proximity to the alignment of fractures active in 1977 and 2002. In a companion paper (Chirico et al., Bull Volcanol, in this issue, 2008) we use numerical simulations to investigate the possibility of reducing lava flow hazard through the construction of protective
barriers, and formulate a proposal for the future development of the town of Goma. 相似文献
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川西坳陷孝泉地区深层须家河组致密砂岩气藏属于典型非常规裂缝性气藏,储层识别、裂缝检测、含气性识别是气藏研究的重点和难点.转换波3D3C勘探可同时获得反映岩石骨架和各向异性特性的C波资料及反映骨架及流体特性的P波资料,因而适用于川西孝泉深层超致密裂缝性气藏.在3D3C地震勘探中,三维三分量地震采集方法是采集到高质量多分量原始资料的技术保障,本文重点研究这种采集方法.首先根据地球物理参数,结合地质任务要求,分析了三维三分量观测系统设计的方法及观测系统参数,然后根据分析结果和勘探目的层的实际情况设计了同时适合纵波勘探和转换波勘探的面元尺寸、最大和最小炮检距、接收线距、束间滚动距等参数并确定了三维三分量观测系统.该观测系统在孝泉地区资料采集中,获得的三分量资料波组特征清楚,同相轴连续,反射信息丰富;Z分量剖面和R分量剖面反射层次清楚,目的层反射特征明显,具有非常好的构造形态一致性. 相似文献
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S.P. DASGUPTA 《Geophysical Prospecting》1987,35(8):924-931
A complete mathematical analysis is proposed for direct current resistivity prospecting over the surface of a layered paraboloid. The analysis evaluates the Green's function in parabolic coordinates for a current source at the vertex. The general solution is obtained as a Fourier-Bessel integral involving those curvilinear coordinates that have a kernel function which is similar to that of a half-plane containing inhomogeneous layers. This similarity permits the computation of a class of sounding curves over such an oval surface providing a way to analyse field data over hilly terrain. 相似文献
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三维三分量(3D3C)陆地反射PS转换波共中心点(CMP)叠加成像方法,虽然抽道集简单,但是对实际资料处理结果往往不理想.尤其当反射界面为三维倾斜界面时,其成像质量较差.本文提出有三个主要因素影响其成像质量:第一,转换点离散.运用实例计算得出,转换点离散度随着纵横波速度比、偏移距和界面倾角的增大而增大.相同界面倾角,不同测线方位的转换点离散度不同,视倾角的绝对值越大离散度也越大;第二,道集内静校正量差异增大.CMP道集中,由于转换点离散使得转换点横向跨度较大,经倾斜界面反射转换的S波出射到近地表地层时的角度差异也较大,导致静校突出;第三,加大动校叠加复杂性.三维倾斜界面PS波CMP道集近炮检距时距方程可表示为双曲形式,但是曲线的顶点位置和动校速度同时随测线方位变化,使得CMP道集同相轴很难校平,动校叠加过程很复杂. 相似文献
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三维三分量(3D3C)陆地反射PS转换波共中心点(CMP)叠加成像方法,虽然抽道集简单,但是对实际资料处理结果往往不理想.尤其当反射界面为三维倾斜界面时,其成像质量较差.本文提出有三个主要因素影响其成像质量:第一,转换点离散.运用实例计算得出,转换点离散度随着纵横波速度比、偏移距和界面倾角的增大而增大.相同界面倾角,不同测线方位的转换点离散度不同,视倾角的绝对值越大离散度也越大;第二,道集内静校正量差异增大.CMP道集中,由于转换点离散使得转换点横向跨度较大,经倾斜界面反射转换的S波出射到近地表地层时的角度差异也较大,导致静校突出;第三,加大动校叠加复杂性.三维倾斜界面PS波CMP道集近炮检距时距方程可表示为双曲形式,但是曲线的顶点位置和动校速度同时随测线方位变化,使得CMP道集同相轴很难校平,动校叠加过程很复杂. 相似文献