南极半岛地区GPS坐标时间序列噪声分析及形变模式初探

有色噪声广泛存在于各种连续GPS站坐标时间序列,对GPS时间序列分析有重要影响.利用GAMIT/GLOBK软件解算了南极半岛地区8个GPS测站2010—2014年的实测数据,对坐标时间序列使用主分量分析法(PCA)进行了空间滤波,利用CATS软件估计了不同噪声模型下和空间滤波前后的噪声量级、站坐标时间序列参数及其不确定度,最后对南极半岛地区水平和垂向的形变模式进行了分析和讨论.结果表明,南极半岛地区GPS时间序列不仅存在白噪声,还存在较大量级的闪烁噪声,部分测站E方向在滤波前可能存在随机游走噪声;空间滤波能够有效降低这三种噪声的量级,从而有效减小线性项和周期项估计的不确定度;南极半岛地区在水平方向主要表现为板块运动,还可能存在局部性构造运动;在垂直方向上由冰川均衡调整(Glacial Isostatic Adjustment,GIA)因素引起的抬升较小,主要表现为现今冰雪质量损失引起的弹性抬升运动.

中国大陆现今构造变形:三十年的GPS观测与研究

中国大陆的构造变形主要与印度和欧亚两大板块的碰撞有关。印度板块的北向推挤直接导致了世界上最宽旷、最活跃和最复杂的现今构造变形。GPS观测技术问世前,构造变形的定量化研究主要依赖活断层的形貌勘察和区域强震的震源机制解,其结果准确度不足且时空界限模糊。1988年中国地震局在滇西地震实验场首次开展GPS形变监测实验,后又经历国家“攀登项目”、“首都圈GPS地形变监测网”等诸多项目实践,直到“九五”重大科学工程“中国地壳运动观测网络”成功建成,中国大陆现今变形图像才逐步完整和清晰。特别是近年基于“中国构造环境监测网络”2000多站点及近30年累积的其他数据,一个覆盖中国大陆且衔接边邻、框架统一、毫米/亚毫米精度的速度场构建完成。这一基础图像对揭示中国大陆活动构造的运动学和动力学特征、深入研究青藏高原及其周边地区构造形成与演化提供了强有力的观测约束,也为地震危险性的定量化分析奠定了坚实基础。

Analysis of granular assembly deformation using discrete element method

The discrete element method is used to simulate specimens under three different loading conditions（conventional triaxial compression,plane strain,and direct shear）with different initial conditions to explore the underlying mechanics of the specimen deformation from a microscale perspective.Deformations of specimens with different initial void ratios at different confining stresses under different loading conditions are studied.Results show that the discrete element models successfully capture the specimen deformation and the strain localization.Particle behaviors including particle rotation and displacement and the mesoscale void ratio distributions are used to explain the strain localization and specimen deformation.It is found that the loading condition is one of the most important factors controlling the specimen deformation mode.Microscale behavior of the granular soil is the driving mechanics of the macroscale deformation of the granular assembly.

Deformation Pattern and Holocene Slip Rate Along the Fukang Fault in Eastern Tianshan, China

The deformation pattern and Holocene slip rate along the Fukang fault in Eastern Tianshan, China are analyzed and studied using the data obtained in field investigation. The result indicates that the Fukang fault consists of 4 low-angle south-dipping thrust faults with stepover, displaying recent tectonic activity. The movement along the termination parts of the fault is weaker, with an average vertical slip rate of 0 13～0 33 mm/a in Holocene, and along the middle part of the fault is stronger, with an average vertical slip rate larger than 1.42 mm/a in Holocene. The Holocene deformation pattern along the fault displays generally steady slip, multi-phase intermittent movement along its western segment, and persistent movement along its middle and eastern segments, which have caused rapid dislocation up to the surface in an earlier phase.

Short-term deformation behavior model of endangered earthen heritage slope after conservation in Jiaohe Ruins

Cliff deformation behavior after conservation is of great significance for evaluating the conservation effect and discovering the dynamical law of soil. Modeling on deformation behavior is beneficial to the quantitative evaluation of interactions between soil mass and structures as well as the forecast. Based on cliff conservation engineering of Jiaohe Ruins （the largest raw soil heritage site in the world）, data of horizontal deformation of the upper cliff were obtained by using Nanrui-made NDW-50 displacement device （precision： 0.01 mm, frequency： 15 min^-l）. Regression analysis indicates that deformation behavior models include exponential growth, linear growth and parabolic growth types, while daily deformation presents more intense periodicity （24 h）. The deformation is less than 1.5 mm during monitoring period, which has no impact on the stability of cliff. Deformation behavior provides the mutual duress and interaction between soil and engineering intervention. In addition, deformation mode attaches tensely to the damage pattern of the cliff. The conclusions are of importance to the stability evaluation of the carrier along Silk Road.

New Activity of the Tanlu Fault Zone in the South of Huaihe to the Nvshanhu Segment since the Late Quaternary

Taking the Huaihe to the Nvshanhu segment of the Tanlu( Tancheng-Lujiang) fault zone as the main research target to explore whether there has been new activity since the late Quaternary,and based on the interpretation of remote sensing images and repeated surface investigations,we excavated trenches at the sections where the tectonic landform is significant,identified and recorded the deformation patterns of the fault and analyzed the activity behavior. Samples of new activity and deformation were collected and oriented slices were ground based on the samples ' original state to make the micro structural analysis and demonstration. All of the above research shows very clear linear tectonic geomorphology along the fault,three trenches across the fault zone all revealed new deformation traces since late Quaternary. The latest stratum dislocated by the fault is the late Quaternary and Holocene. The main slip mode is stick slip,as represented typically by fault scarps,wedge accumulation,the faults and the filled cracks and so on. In general,it shows the characteristics of brittle high-speed deformation and belongs to the prehistoric earthquake ruins. The above understanding was confirmed partially by microscopic analysis. In addition,the similarities and differences and the possible reasons for the characteristics of the latest activities of the Tancheng-Lujiang fault zone in the north and south of the Huaihe River regions are also discussed in this paper.

Identification of Bandhead Spin and Identical Bands for Odd-A Nuclei in A-190 Superdeformed Mass Region

The dynamical moment of inertia is estimated with its even-power expansion of the rotational frequency and in accordance we determine the intermediate spins of the superdeformed(SD)rotational bands.Using Marquardt method of nonlinear least-squares routines,we determine the expansion coefficients by fitting the proposed dynamical moment of inertia with its recent experimental data of the SD nuclei in the A=190 mass region.The comparison between our theoretical and available experimental data for the dynamic moment of inertia and spin shows good agreements. Also,we have calculated the static moment of inertia at three alternative values of spin.The value of spin at which the two moments of inertia are nearly equals is to be regarded as a bandhead spin of the corresponding band.These studies are carried out for eighteen bands of odd-A nuclei of the superdeformed region 190,namely ~(189)Hg(b1),~(191)Hg(b1,b2, b3,b4),~(193)Hg(b2,b3,b5),~(195)Hg(b1,b2,b3,b4),~(193)Tl(b1,b2,b3,b5),~(189)Tl(b1),and~(197)Bi(b1).We also notice the occurrence of identical SD bands with near identical transition energies among the considered SD bands.

Jacquard image segmentation using Mumford-Shah model

Jacquard image segmentation is one of the primary steps in image analysis for jacquard pattern identification. The main aim is to recognize homogeneous regions within a jacquard image as distinct, which belongs to different patterns. Active contour models have become popular for finding the contours of a pattern with a complex shape. However, the performance of active contour models is often inadequate under noisy environment. In this paper, a robust algorithm based on the Mumford-Shah model is proposed for the segmentation of noisy jacquard images. First, the Mumford-Shah model is discretized on piecewise linear finite element spaces to yield greater stability. Then, an iterative relaxation algorithm for numerically solving the discrete version of the model is presented. In this algorithm, an adaptive triangular mesh is refined to generate Delaunay type triangular mesh defined on structured triangulations, and then a quasi-Newton numerical method is applied to find the absolute minimum of the discrete model. Experimental results on noisy jacquard images demonstrated the efficacy of the proposed algorithm.

Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form

Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.

仿生磁响应4D智能水凝胶制备及其自驱动变形研究

洋绣球种子芒在湿度条件下,通过弯曲与解弯曲变形特性实现自驱动播种功能。以洋绣球种子芒为生物模本,基于其变形部位的微观结构特性及自驱动变形机理,构建了溶胀度具有各向异性的仿生双层结构模型,指导仿生磁响应4D智能水凝胶的设计。以N,N-二甲基丙烯酰胺为单体,合成硅酸镁锂为交联剂,纳米木浆纤维素为增强相,四氧化三铁为磁响应粒子,由物理交联方法制备聚N,N-二甲基丙烯酰胺智能水凝胶为基本材料,通过"一步法"模具成型技术成功制备了具有溶胀、磁响应变形特性的仿生磁响应4D智能水凝胶,实现了力学强度与多形式智能响应的有效兼顾,为磁响应智能水凝胶瓶颈问题的解决提供了一种有效的仿生学新思路与新方法。

前纵梁等效薄壁结构正面碰撞特性实验研究

通过实验分析了一系列高强度钢材料的正面碰撞特性。基于台车正碰试验所获得的数据基础研究了各种材料及其厚度下的形变模式及其碰撞吸能特性,分析对比了各材料下的平均加速度,为前纵梁材料和厚度的选取提供选择方向。结果表明,DP590,TR590,DP780和DP780+Z 4种材料具有优秀的折叠次序,属于渐进叠缩变形,能通过变形充分吸收碰撞能量,并且较低的平均加速度比较适合前纵梁前段压溃区,故在等厚度情况下,宜选用强度较低的高强度钢。

Accurate modelling of the crush behaviour of thin tubular columns using material point method

In this paper,we apply the material point method(MPM),also known as a meshfree method,to examine the crush behaviour of thin tubular columns.Unlike the finite element method,randomly-distributed-weak-particle triggers were used to account for the deformation behaviour of collapse modes.Both symmetric and asymmetric modes of deformation and their associated mean collapse loads are determined for an elasto-plastic constitutive law describing the tubular columns.Attention was devoted to the accuracy and the convergence of the MPM simulation,which is determined by the number of the particles and the size of the background cells used in our explicit solver.Furthermore,a novel contact approach was adopted to establish the crush behaviour of the tubular columns.Two aspects of the work were accordingly examined,including three different crush velocities(5,10 and 15 m/s) and varied geometrical features of the tube(t/d and l/d) based on the deformation history.The results of our model,which were compared with existing analytical predictions and experimental findings,identify the critical geometric features of the tubular columns that would dictate the deformation mode as being either progressive collapse or following Euler's buckling mode.

Upper mantle anisotropy and crust-mantle deformation pattern beneath the Chinese mainland

Over the past 10 years, the number of broadband seismic stations in China has increased significantly. The broadband seismic records contain information about shear-wave splitting which plays an important role in revealing the upper mantle anisotropy in the Chinese mainland. Based on teleseismic SKS and SKKS phases recorded in the seismic stations, we used the analytical method of minimum transverse energy to determine the fast wave polarization direction and delay time of shear-wave splitting. We also collected results of shear-wave splitting in China and the surrounding regions from previously published papers. From the combined dataset we formed a shear-wave splitting dataset containing 1020 parameter pairs. These splitting parameters re- veal the complexity of the upper mantle anisotropy image. Our statistical analysis indicates stronger upper mantle anisotropy in the Chinese mainland, with an average shear-wave time delay of 0,95 s; the anisotropy in the western region is slightly larger （1.01 s） than in the eastern region （0.92 s）. On a larger scale, the SKS splitting and surface deformation data in the Tibetan Plateau and the Tianshan region jointly support the lithospheric deformation mode, i.e. the crust-lithospheric mantle coherent deformation. In eastern China, the average fast-wave direction is approximately parallel to the direction of the absolute plate motion; thus, the upper mantle anisotropy can be attributed to the asthenospheric flow. The area from the Ordos block to the Sichuan Basin in central China is the transition zone of deformation modes between the east and the west regions, where the anisotropy images are more complicated, exhibiting ＂fossil＂ anisotropy and/or two-layer anis^3trc^py. The c^llisi（3n between the Indian Plate and the Eurasian Plate is the main factor of upper mantle anisotropy in the western region of the Chinese mainland, while the upper mantle anisotropy in the eastern region is related to the subduction of the Pacific Plate and the Philippine Sea Plate beneath the Eurasian Plate.

Structural geometrical analysis and simulation of decollement growth folds in piedmont Fauqi Anticline of Zagros Mountains, Iraq

This study carried out detailed structural analyses of the plane structural deformation pattern and sectional structural deformation styles of the Fauqi Anticline by the 3D seismic section with full cover collection, and carried out the kinematical simulation of the Fauqi anticlinal deep decollement coupling shallow growth folds and faults based on the fault decollement fold model and the forward balanced geological section technique. The study subsequently evaluated the differentiated petroleum enrichment mechanism of the Fauqi Anticline by utilizing the results of the structural analysis and combining the spatial-temporal relationship analysis of the source, the reservoir, and the caprock. The results showed that the differentiated plane structural deformation pattern and hierarchical sectional structural deformation style were developed by the superposed coupling of deep decollement, syntectonic sedimentation of shallow growth strata, and the compression of the south-west horizontal tectonic stress from the Zagros Mountains. It was found that the differentiated structural deformation caused the differentiated enrichment of petroleum in the Fauqi Anticline. It was also found that the horizontal slip distance of the Fauqi Anticlinal Folds reached around 3.5 km by the simulation of deep decollement coupling the movement of the shallow growth folds and the faults.

Size-dependent deformation behavior of dual-phase,nanostructured CrCoNi medium-entropy alloy

The mechanical size effect of nanostructured,dual-phase CrCoNi medium-entropy alloy(MEA)was investigated by combining in-situ micro-compression testing with post-mortem electron microscopy analysis.The alloy possesses a superior yield strength up to~4 GPa,primarily due to its hierarchical microstructure including column nanograins,preferred orientation,a high density of planar defects and the presence of the hexagonal close packed(HCP)phase.While the yield strength of the alloy has shown sizeindependency,the deformation behaviour was strongly dependent on the sample size.Specifically,with decreasing the pillar diameters,the dominant deformation mode changed from highly localized and catastrophic shear banding to apparently homogeneous deformation with appreciable plasticity.This transition is believed to be governed by the sizedependent critical stress required for a shear band traversing the pillar and mediated by the competition between shearinduced softening and subsequent hardening mechanisms.In addition,an unexpected phase transformation from HCP to face-centered cubic(FCC)was observed in the highly localized deformation zones,leading to strain softening that contributed to accommodating plasticity.These findings provide insights into the criticality of sample dimensions in influencing mechanical behaviors of nanostructured metallic materials used for nanoelectromechanical systems.

Comparisons between centrifuge and numerical modeling results for slope toppling failure

This paper presents series studies on the toppling mechanism by centrifuge tests and numerical simulations. Two different discrete element methods, i.e., the continuum-based discrete element method(CDEM) and the discontinuous deformation analysis(DDA), are adopted. The modeling results show that both the methods can accurately capture the failure modes of the centrifuge tests, including three distinct zones and two failure surfaces. Comparisons are made between the physical test and numerical simulation results. The critical inclination angle of the tilting table where the slope models are fixed on can be moderately predicted by the two methods, with different degrees of precision. The error between the test results and the simulated results is within 1% for the slope models without rock-bridges by both CDEM and DDA. However, it is amplified for the staggered-joint models that simulate the rock-bridges. With DDA, the average error is about 5%, and the maximum error is up to 17%. While with CDEM, the errors for the aligned-joint models are ranged from 1% to 6%, and it is from 10% to 29% for the staggered-joint models. The two numerical methods show the capability in simulating toppling failure of blocky rock mass with and without rock-bridges. The model with rock-bridges which provides a certain bending resistance is more stable than the one without any rock-bridge. In addition, the two failure surfaces were observed, which is different from the common understanding that only one failure surface appears.

Deformational characteristics of sensor-enabled geobelts incorporating two failure modes in reinforced sand

Geobelt deformation is of significance when making prejudgments on potential failure planes in reinforced structures.A failure plane results from two geobelt failure modes,tensile failure and pullout.In order to investigate the deformation characteristics of geobelts in two failure modes,results from pullout tests on sensor-enabled geobelts(SEGBs)with various lengths in sand are reported here across a range of normal pressures.Self-measurements of SEGB can provide data during the tests regarding distributions of strain,stress,and displacement.Data collected during pullout tests reveal the effects of normal pressures and specimen lengths on failure mode.A critical line considering normal pressure and specimen length is derived to describe the transition between two failure modes,an approach which can be utilized for preliminary predictions of failure mode in pullout tests.Warning criteria established based on critical line and data from the self-measurements of SEGB are proposed for failure mode prediction which can contribute to prejudgments of potential failure plane in geosynthetically reinforced soil structures.

Size-dependent transition of the deformation behavior of Au nanowires

Inspired by the controversy over tensile deformation modes of single-crystalline 〈110〉/{111} Au nanowires, we investigated the dependency of the deformation mode on diameters of nanowires using the molecular dynamics technique. A new criterion for assessing the preferred deformation mode-slip or twin propagation--of nanowires as a function of nanowire diameter is presented. The results demonstrate the size-dependent transition, from superplastic deformation mediated by twin propagation to the rupture by localized slips in deformed region as the nanowire diameter decreases. Moreover, the criterion was successfully applied to explain the superplastic deformation of Cu nanowires.

Melanopsin-expressing retinal ganglion cell loss and behavioral analysis in the Thy1-CFP-DBA/2J mouse model of glaucoma

In this study, the role of melanopsin-expressing retinal ganglion cells （mRGCs） in the glaucoma-induced depressive behavioral response pattern was investigated. The CFP-D2 transgenic glaucoma animal model from five age groups was used in this study. Immunohistochemical labeling, quantitative analysis of mRGC morphology, open field test （OFT）, and statistical analysis were used. In comparison with C57 BL/6 mice, the age-matched CFP-D2 mice had significantly elevated intraocular pressure （lOP）. We observed parallel morphological changes in the retina, including a reduction in the density of cyan fluorescent protein- （CFP） expressing cells （cells mm^-2 at 2 months of age, 1309±26; 14 months, 878±30, P〈0.001）, mRGCs （2 months, 48_＋3; 14 months, 19±4, P〈0.001）, Brn3b-expressing RGCs （2 months, 1283±80; 14 months, 950±31, P〈0.001）, Brn-3b expressing mRGCs （5 months, 50.17%±5.5%; 14 months, 12.61%±3.8%, P〈0.001）, and reduction in the dendritic field size of mRGCs （mm^2 at 2 months, 0.077±0.015; 14 months, 0.065±0.015, P〈0.05）. CFP-D2 mice had hyperactive locomotor activity patterns based on OFT findings of the total distance traveled, number of entries into the center, and time spent in the center of the testing apparatus. The glaucoma induced hyperactive response pattern could be associated with dysfunctional mRGCs, most likely Brn-3b-positive mRGCs in CFP-D2 mice.