Strong magnetic linear dichroism in Fe <Emphasis Type="Italic">L</Emphasis><Subscript>23</Subscript> and O <Emphasis Type="Italic">K</Emphasis> electron energy-loss near-edge spectra of antiferromagnetic hematite α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

We report strong magnetic linear dichroism (MLD) at the Fe L₂₃ and O K edges of the antiferromagnetic compound hematite -Fe₂ O₃ in high-resolution orientation- and temperature-dependent electron energy-loss spectroscopy (EELS). Large intensity differences of corresponding spectral features are observed when the Fe L₂₃ and O K edges are measured with momentum transfer either parallel or perpendicular to the magnetization. The resultant difference spectra for the Fe L₂₃ edges is consistent with the MLD observed in X-ray absorption spectroscopy. For the first time we have observed MLD at the O K edge, where the magnetic origin of this dichroism is demonstrated by temperature-dependent investigations across the Morin transition temperature T_M= 263 K, at which the Fe electron spins, i.e. the magnetic moments, rotate by 90°. The O K edge MLD is interpreted in terms of superexchange between the spins of the Fe 3d and O 2p electrons through overlapping Fe 3d and O 2p orbitals. The experiments were performed in a transmission electron microscope (TEM), yielding information about the anisotropic electronic structure at nanoscale spatial resolution when operated with a focused electron probe. The effects of MLD at the Fe L₂₃ edges on the determination of Fe³⁺/Fe in hematite at submicrometre scale using different independent quantification methods are discussed.     

Gas permeability evolution of cataclasite and fault gouge in triaxial compression and implications for changes in fault-zone permeability structure through the earthquake cycle

We report the results of permeability measurements of fault gouge and tonalitic cataclasite from the fault zone of the Median Tectonic Line, Ohshika, central Japan, carried out during triaxial compression tests. The experiments revealed marked effects of deformation on the permeability of the specimens. Permeability of fault gouge decreases rapidly by about two orders of magnitude during initial loading and continues to decrease slowly during further inelastic deformation. The drop in permeability during initial loading is much smaller for cataclasite than for gouge, followed by abrupt increase upon failure, and the overall change in permeability correlates well with change in volumetric strain, i.e., initial, nearly elastic contraction followed by dilatancy upon the initiation of inelastic deformation towards specimen failure. If cemented cataclasite suffers deformation prior to or during an earthquake, a cataclasite zone may change into a conduit for fluid flow. Fault gouge zones, however, are unlikely to switch to very permeable zones upon the initiation of fault slip. Thus, overall permeability structure of a fault may change abruptly prior to or during earthquakes and during the interseismic period. Fault gouge and cataclasite have internal angles of friction of about 36° and 45°, respectively, as is typical for brittle rocks.     

供电线路勘测内外业一体化系统的开发和应用

供电线路勘测是属于普通工程测量,结合计算机技术制图技术和电子测绘仪器的特点,作者开发了一套适合市县一级的供电线路勘测系统,以AutoCad为绘图平台,VBA5.0为开发语言,符合测绘习惯,提高了工作效率。     

Erratum: the 2.27 day period of WR-134 (HD 191765)

The original temporal analysis of a 12 night spectral timeseries of WR-134 has been found to be flawed and a re-analysis shows that the line profile variations are indeed periodic. When combined with a 4 night timeseries taken 45 days earlier, a period near 2.27 d is found in periodograms of the Heii 5412 line centroid,rms line width, and line skew variations. When the emission line residuals are ordered as a function of phase, a sinuous feature appears to snake about the line center with an amplitude of ± 500 km s^–1. This is 20 larger than the line centroid amplitude; the calculation of which is heavily weighted by static portions of the line profile. In addition to the snake, emission residuals appear that move away from line center on unbound trajectories and are thought to result from the interaction of a periodic driver with the unstable flow of the radiation driven wind. The nature of the periodic driver is a topic for discussion.     

山洞电源、信号线路改造与接地网建设相关技术探讨

本文对铁岭地震台在山洞电源，信号线路改造与接地网建设中遇到的问题及解决的办法做简要介绍，依据洞室固有条件，结合《规范》要求，探讨了监测环境建设施工经验。     

Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO)

We present microstructural data and lattice preferred orientations (LPOs) of omphacites from a suite of eclogites, from the Adula/Cima Lunga nappe (Central Alps). Our work shows a surprisingly strong correlation between the measured LPO and the ordering state of cations in omphacite. Estimates of deformation temperature from metamorphic petrology, together with measured omphacite compositions and LPOs, determine the field (ordering state), on the omphacite phase diagram, into which each sample falls. LPOs dominated by L-type and S-type signatures are developed in samples that fall in the P2/n field (ordered structure) and C2/c field (disordered structure), respectively.Dislocations with b=1/2−110 or b=[001] are observed in the transmission electron microscope (TEM) in all samples. The former change from a perfect dislocation in the C2/c structure to a partial in P2/n. Any movement of a partial dislocation requires the formation or growth of a stacking fault. Furthermore, in order to pass an obstacle a partial dislocation has to constrict to a unit dislocation. The energy to form a constriction is high in omphacite due to the large separation width. Thus, the activity of the b=1/2−110 dislocation is hindered in the P2/n structure relative to the C2/c structure, which change the balance between the two and might give rise to the different LPOs.     

数码航摄(DMC)像控布设方案研究

利用1∶3500、1∶6000、1∶20000三种比例尺的DMC航摄资料,在航线数不变的条件下分别采用每隔4、6、8、10、16条基线进行像控点布设,在立体测图仪上加密、纠正、测图,提取地物点其坐标与外业检测成果比较,检验其对1∶500、1∶1000、1∶5000三种比例尺成图精度的影响。     

中国西北“水三线”空间格局与水资源配置方略

水是西北地区可持续发展的生命线,中国西北地区占国土总面积35.9%,水资源约占全国水资源总量的5.7%。从水文气象、生态景观与社会经济的演变角度,面向水资源优化配置、生态环境与社会经济协调发展,探索提出西北“水三线”的划分格局,即“胡焕庸线”“阳关线”和“奇策线”。“水三线”是西北水资源合理开发利用的优化配置线、西北生态文明与环境保护的特征分区线、“一带一路”建设的战略制导线和边疆长治久安、社会稳定的国家安全线。针对西北地区水资源开发利用存在的问题、面临的挑战以及西北稳定发展的地理与历史之忧,本文通过对西北调水方案的初步分析,提出了西北“水三线”建设的空间格局与水资源配置方略,即通过建设南水北调大西线这一重大的基础工程,跨越“胡焕庸线”,促进中国东西部地区间适度均衡发展;跨越“阳关线”,促进河西走廊社会经济发展;跨越“奇策线”,增强新疆水资源及环境承载能力,建设和谐美丽、长治久安的西北边疆,形成以西北“水三线”建设为构架的水资源梯度配置格局,支撑西北地区经济社会稳定发展、生态文明建设,促进国土资源、人口分布、产业经济的空间均衡、优化布局、协调发展,为“一带一路”建设提供水资源保障。     

频率域线源大地电磁法有限元正演模拟

本文介绍了频率域线源大地电磁法有限元正演模拟的研究结果. 在外边界上统一应用适合于人工源的一阶吸收边界条件来形成边值问题,可减小基于平面波假设造成的人为截断边界的影响. 程序编辑中设计了两个二维数组分别存储总体系数矩阵的非零元素和在总体结点编号中的位置,使内存占用量减少,且物理意义明确,方便用高斯-赛德尔等迭代法解有限元方程时调用. 采用视δ函数模拟线源,提高了解方程组的稳定性. 最后通过对1个简单模型和1个复杂模型的模拟,证明所用的方法对异常体能够有明显的反映,说明了该方法的可靠性和有效性.