Uplift and subsidence due to the 26 December 2004 Indonesian earthquake detected by SAR data

The Indonesian earthquake took place on 26 December 2004 at 00:58 GMT (moment magnitude 9.3) in the Indian Ocean, offshore the west coast of Sumatra, at a depth of about 30 km. This earthquake is one of the largest of the past 100 years, comparable only with those in Chile (1960) and Alaska (1964). The earthquake originated in the subduction zone of the Indian and Burma plates, moving at a relative velocity of 6 cm/year. The aftershocks were distributed along a plate boundary of about 1000–1300 km between Sumatra and the Andaman Islands. Some hours after the earthquake a destructive tsunami followed and hit the coastlines of the surrounding regions, causing widespread destruction in Indonesia, India, Thailand and Sri Lanka. The European Space Agency (ESA) made available a data package composed of European Remote Sensing Satellite Synthetic Aperture Radar (ERS‐SAR) and Environment Satellite Advanced SAR (ENVISAT‐ASAR) data covering the affected area, acquired before (four acquisition dates) and after (five acquisition dates) the earthquake. A total of 26 frames were analysed. We used this dataset to evaluate the effects of the earthquake and tsunami on the human settlements and the physiographic conditions along the coast. The proposed method is based on a visual comparison between pre‐ and post‐seismic SAR intensity images, and on an analysis of their correlation coefficients. No complex data were made available by the ESA to exploit phase coherence. Analysis of pre‐ and post‐earthquake SAR backscattering showed wide uplift areas between the Andaman Islands and Simeulue Island, and large modifications of the coastline of Sumatra. Subsiding areas were detected along the southeast coast of Andaman up to the west coast of Nicobar Island. Tidal effects were filtered out of the SAR images to identify the consequences of the earthquake. Global Positioning System (GPS) stations in the Andaman provided results confirming the surface displacement pattern detected by SAR. The analysis enabled us to draw a boundary line separating the uplift and subsidence.     

Analysis of GPS-based TEC and electron density by the DEMETER satellite before the Sumatra earthquake on 30 September 2009

An analysis of ionospheric total electron content (TEC) variations obtained using Global Positioning System (GPS) measurements and electron density observations by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER)/ISL before the Sumatra earthquake (magnitude 7.6) on 30 September 2009 is presented. The data used are global TEC maps created in the IONEX format to estimate the spatial scale of ionospheric irregularities associated with this earthquake and DEMETER/ISL observations to analyse plasma parameter changes during earthquakes. This study for the first time integrates ground-based GPS receiver and space-based DEMETER/ISL observations to probe seismo-ionospheric anomalies before a large earthquake. The pre-seismic behaviour of the TEC was detected within a few days before the main event. The anomaly appeared as local TEC enhancement in the vicinity of the forthcoming earthquake epicentre. These structures were generated in the ionosphere at a similar local time at 1, 3 and 5 days prior to the main shock. The equatorial anomaly trough moved northwards (5°) on the earthquake day and 7.5° southwards the next day. The results demonstrate that both enhanced and reduced anomalies in the ionospheric electron density appeared before the Sumatra earthquake. The results from International GNSS Service (IGS) GPS data demonstrate that TEC variations can be used to detect seismo-ionospheric signatures.     

The problem of selecting an approach based on prior success

This article is the twenty-sixth of a series of articles discussing various open research problems in automated reasoning. The problem posed for research asks one to find criteria for choosing from among previously answered questions a question that dictates the approach to take for attacking the problem of current interest. Especially because the better automated reasoning programs often offer a wide range of choices for representation, inference rule, and strategy, a solution to the proposed problem would materially reduce the difficulty of using these powerful aids for research.This work was supported by the Office of Scientific Computing, U.S. Department of Energy, under Contract W-31-109-Eng-38.     

Marsobot: design and performance characterization of a low-cost,ground-based multispectral camera on an open source rover

Open source, low cost sensors, and robotic systems have developed to the point of being able to produce meaningful, repeatable results in real-life applications. We developed a low-cost, open source multispectral camera mounted on a small custom-built robotic rover. We compared the performance of our camera with a commercial multispectral camera and a laboratory spectrometer using minerals commonly found on Mars that exhibited different reflectance values in visible and near-infrared wavelengths. Our camera performed favourably when compared to the commercial instruments. It is a very cost effective solution for operating in extreme situations, where damage to instruments is possible. Our total system of rover and sensor would, therefore, be very useful for operating in delicate and inaccessible environments where damage to the area under investigation and to human observers is of concern.     

张掖市甘州区1959~2009年间城市扩展分析

利用锁眼、MSS、TM影像和地形图及其他辅助数据,提取张掖市1959、1968、1977、1986、1997、2009共6个年份的城市建成区范围和面积,利用空间重心转移模型、扩展强度指数、扩展速度指数、紧凑度指数、面积变化、城市用地扩展系数等指标,分析了近50 a来城市土地利用扩张的空间变化特征。结果表明,50 a间张掖市城市建成区扩展5.71倍,其中1986年之前属于缓慢扩展阶段,1986年之后属于快速扩展阶段。在1959~1986的27 a间,建成区面积仅扩展258.42 hm²。1986~2009年期间,随着改革开放和西部大开发战略的实施,建成区面积增加了1 995.11 hm²,是前27 a的7.73倍。1959~1977年期间,城市重心偏移量小,1977~1986年期间,虽然城市扩展面积较小,但城市主要向西和西北方向扩展,重心开始向西北偏移,偏移量较大;1977~2009年期间,由于城市向东和东北方向扩展,城市重心开始向东和东北方向偏移,偏移量都很大,最大达到629.79 m。城市紧凑度在1959~1968年间急剧下降;在1968~1997年间逐渐趋于稳定后又略有下降,1997~2009年开始慢慢上升,该市后期土地的集约化以及城市基础设施和公共资源的利用效率有所提高。城市用地扩展系数在1959~1986年期间小于1.12,城市用地规模扩展不足(1977年前后比较特殊),1986~2009年期间,城市用地扩展系数大于1.12,城市用地规模扩展过快。     

Multisim变压器参数分析与应用

针对软件Multisim中变压器参数含义不清所造成的困惑问题,结合变压器一般工作原理及方程,通过虚拟仿真实验,研究了Multisim中变压器模型及其部分参数的含义,给出了该软件变压器参数与变压器绕组自感互感的关系。通过一个电路实例,进一步说明了Multisim变压器参数的设置与应用。     

A method to estimate the parameters of an ARMA model

A method of estimating the parameters of an ARMA model is proposed. In the transient case, we show that the formulas recently given by Li and Dickinson [7] for the AR parameters are easily obtained by considering the formulation of the one-step predictor. In the steady-state case, we can get separately the AR parameters and the MA ones.     

融合背景先验与中心先验的显著性目标检测

目的 现有的显著性目标检测算法通常基于单一的先验信息,导致提取的原图像信息不全面,为了解决该问题,提出一种新的基于背景先验与中心先验相融合的显著目标检测算法。方法 该方法首先以边缘超像素为吸收节点,利用马尔可夫吸收链计算其他超像素的平均吸收时间作为背景先验值,得到背景先验图;然后使用改进Harris角点检测估计目标区域位置,建立峰值位于目标中心的2维高斯函数,计算各超像素的中心先验值,获取中心先验图;最后将背景先验图与中心先验图相融合得到显著图。同时该方法融合多尺度检测结果,进一步提高显著值的准确性。结果 通过ASD、SED1、SED2和SOD 4个公开数据库对比验证了基于背景先验与中心先验相融合算法具有较高的查准率、查全率和F-measure,相较于基于马尔可夫吸收链算法均提高了3%以上,总体效果明显优于目前的10种主流算法。结论 相较于基于单一先验信息的算法,基于背景先验与中心先验相融合的算法充分利用了图像信息,在突出全局对比的同时也保留了较多的局部信息,能高亮地凸显图像中的显著性目标。该方法在检测单一目标的图片时效果显著,但对于多目标的显著性检测尚有不足。     

The Al Hoceima (Morocco) earthquake of 24 February 2004, analysis and interpretation of data from ENVISAT ASAR and SPOT5 validated by ground-based observations

The magnitude M_w = 6.3 earthquake in Al Hoceima, Morocco of 24 February, 2004 occurred in the active plate boundary accommodating the oblique convergence between Africa and Eurasia. Three different sets of estimates of its source parameters have already been published. We try to resolve the discrepancies between them by using additional data including two remote sensing satellite systems (ENVISAT and SPOT5). Using a model with a dislocation in an elastic half-space, we constrain the source parameters. The hypothesis of two subevents on distinct faults as inferred from seismological inversions is confirmed here by adopting a cross-fault mechanism. The rupture began on a left-lateral strike-slip fault striking at N10° azimuth with 90 cm of horizontal slip and then transferred to a right-lateral strike-slip fault striking at N312° azimuth with 85 cm of horizontal slip. The first fault is at 500 m depth from the free surface and the second fault is at 3 km depth. This model is consistent with ground-based observations, including GPS, seismology, and mapped surface fissures. The pair of faults activated in 2004 appears to constitute part of a complex seismogenic structure striking NNE-SSW that separates the Rif tectonic blocks.     

Frequency-domain application of an input-error method to estimate aircraft longitudinal parameters

An input-error method for estimating parameters of a single-input-multi-output linear time-invariant system is formulated in the frequency domain. The input-error method includes the Gauss-Newton minimization technique as a part of the estimation procedure. Two possible ways of defining the objective function are presented and the results obtained from these two approaches are compared. The method is applied to extract the longitudinal stability and control derivatives (parameters) of an aircraft from simulated flight data. Flight data for the short-period dynamics of the aircraft are analysed for different control input forms to identify the effect of the input forms on the accuracy of estimation. The effect of the variations in the intensity of noise present in the input and/or output data and the effect of the choice of initial values to start the identification process, on the accuracy of estimation, is also studied. The method is shown to be quite robust to estimate parameters from flight data having high intensity noise in both the input and the output signals.     

萤火虫算法参数分析与优化

针对萤火虫算法参数设置问题,在分析萤火虫算法原理和数学模型基础上,确定算法需要设置的主要参数有萤火虫数量n、步长因子α、吸收因子γ、最大迭代次数T。提出了一种通过理论定性分析以及单因素数值试验,测试经典测试函数分析各参数对求解性能影响的方法,测试结果表明参数的设置对算法的求解性能有很大影响。最后通过对比试验数值表明,参数优化后比优化前萤火虫算法的求解精度提高了1～2个数量级,并且收敛代数也明显减少,验证了所提出方法的有效性,达到提高算法精度和速度的效果,也为算法的进一步应用提供参数设置与优化的参考。     

Analysis and visualization of predicate dependence on formal parameters and global variables

Empirical data concerning the qualitative and quantitative nature of program dependence is presented for a set of 20 programs ranging from 600 lines of code to 167,000 lines of code. The sources of dependence considered are global variables and formal parameters and the targets considered are a program's predicate nodes. The results show that as the number of formal parameters available to a predicate increases, there is a decrease in the proportion of these formal parameters which are depended upon by the predicate. No such correlation was found for global variables. Results from theoretical and actual computation time analysis indicate that the computation of dependence information is practical, suggesting that the analysis may be beneficial to several application areas. The paper also presents results concerning correlations that provide strong evidence that the global and formal dependence sources are independent of one another and that the numbers of globals and formals are independent of the size of the procedure that contains them. Finally, two visualization techniques for displaying dependence information are introduced. Illustrations show how these visualizations and predicate dependence analysis can assist in activities such as testing, comprehension, and evolution.     

Local motion deblurring using an effective image prior based on both the first- and second-order gradients

Local motion deblurring is a highly challenging problem as both the blurred region and the blur kernel are unknown. Most existing methods for local deblurring require a specialized hardware, an alpha matte, or user annotation of the blurred region. In this paper, an automatic method is proposed for local motion deblurring in which a segmentation step is performed to extract the blurred region. Then, for blind deblurring, i.e., simultaneously estimating both the blur kernel and the latent image, an optimization problem in the form of maximum-a-posteriori (MAP) is introduced. An effective image prior is used in the MAP based on both the first- and second-order gradients of the image. This prior assists to well reconstruct salient edges, providing reliable edge information for kernel estimation, in the intermediate latent image. We examined the proposed method for both global and local deblurring. The efficiency of the proposed method for global deblurring is demonstrated by performing several quantitative and qualitative comparisons with the state-of-the-art methods, on both a benchmark image dataset and real-world motion blurred images. In addition, in order to demonstrate the efficiency in local motion deblurring, the proposed method is examined to deblur some real-world locally linear motion blurred images. The qualitative results show the efficiency of the proposed method for local deblurring at various blur levels.     

Comparative study of aircraft- and satellite-derived aerosol and cloud microphysical parameters during CAIPEEX-2009 over the Indian region

This article presents the spatial and vertical distribution of aerosols and cloud microphysical parameters from the combined data sets of aircraft and satellites. The aircraft-based Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) was conducted in India during May to September 2009. During the experimental period, 3 days were identified on which space-borne lidar (CALIPSO) and radar (CloudSat) were nearby/over passed the observational regions, which covered north, south central, and southern parts of the Indian subcontinent. The results obtained from these three cases are explored. Similar features of aerosol layering and water/ice cloud signatures are observed by both aircraft and CALIPSO. In addition, events where dust aerosols acting as ice nuclei and polluted aerosols increase the depth of warm rain initiation are observed. The CloudSat profiles of liquid water content, droplet number concentration, and effective radii are underestimated when compared with the corresponding aircraft profiles. The aircraft measurements are able to bring out fine variability in vertical distribution, which would be more useful for regional parameterization schemes and model evaluation.     

Multiphase segmentation using an implicit dual shape prior: Application to detection of left ventricle in cardiac MRI

Cardiac magnetic resonance imaging (MRI) has been extensively used in the diagnosis of cardiovascular disease and its quantitative evaluation. Cardiac MRI techniques have been progressively improved, providing high-resolution anatomical and functional information. One of the key steps in the assessment of cardiovascular disease is the quantitative analysis of the left ventricle (LV) contractile function. Thus, the accurate delineation of LV boundary is of great interest to improve diagnostic performance. In this work, we present a novel segmentation algorithm of LV from cardiac MRI incorporating an implicit shape prior without any training phase using level sets in a variational framework. The segmentation of LV still remains a challenging problem due to its subtle boundary, occlusion, and inhomogeneity. In order to overcome such difficulties, a shape prior knowledge on the anatomical constraint of LV is integrated into a region-based segmentation framework. The shape prior is introduced based on the anatomical shape similarity between endocardium and epicardium. The shape of endocardium is assumed to be mutually similar under scaling to the shape of epicardium. An implicit shape representation using signed distance function is introduced and their discrepancy is measured in a probabilistic way. Our shape constraint is imposed by a mutual similarity of shapes without any training phase that requires a collection of shapes to learn their statistical properties. The performance of the proposed method has been demonstrated on fifteen clinical datasets, showing its potential as the basis in the clinical diagnosis of cardiovascular disease.