MIMO regulation control design for magnetic steering of a ferromagnetic particle inside a fluidic environment

As an important development of medical instrumentation, minimally invasive therapeutic operations have been recently introduced. The foremost element of minimally invasive techniques is navigating a micro-device through human body, especially inside blood vessels. A remote actuation over the micro-device is normally provided by electromagnetic actuators. In most applications, a control scheme is also required to initiate the actuation force, the magnetic propulsion, such that at every time step, the micro-device moves towards or along a given path. This paper contributes in development of the electromagnetic system model mostly used in magnetic navigation systems to be representable in control affine form. Next, a multi-input multi-output (MIMO) trajectory tracking controller is designed to conduct the auto-navigation of the device along a given path. This method is a generalised version of a ‘semi-global nonlinear output regulation’ introduced for single-input single-output (SISO) systems. Finally, the proposed scheme is examined for an iron particle moving in a fluidic environment. The simulation results show fast decay in deviation of the particle position from the reference path under some assumptions. This shows that the proposed scheme can be offered for medical applications.     

局部梯度轮廓变换的高光谱异常检测

目的 高光谱异常检测由于其重要的应用价值,引起了研究人员的广泛关注,但大部分的检测算法,往往直接利用输入的高光谱遥感影像所携带的光谱信息或者空谱信息进行检测。考虑到由于成像过程的限制,如成像条件的复杂性以及光谱通道众多导致的每个通道光子数量有限等问题,所获取的高光谱遥感影像往往在一定程度上偏离真实场景,而这也制约了异常检测的精度。针对此问题,本文提出了一种局部梯度轮廓变换的高光谱遥感影像异常检测算法。方法 为了在不影响算法性能的基础上减少计算复杂度,首先选取部分可能的异常像元,只对这些局部的异常像元可能位置进行梯度轮廓变换。其次,将变换后的梯度轮廓用于指导原始高光谱遥感影像的空域增强。最后,对增强后的高光谱遥感影像进行检测。通过将局部梯度轮廓用于影像的增强,避免了成像过程中由于细节损失而造成检测精度受限的情况。结果 实验在来自4个数据集的6幅高光谱遥感影像上进行了性能验证。首先利用经典的Global-RX （Reed Xiaoli）检测算法同时检测本文算法增强后的影像和原始影像,分别取得的平均AUC （area under curve）值为0.987 1和0.933 6,本文算法带来了0.053 5的精度提升;同时,通过与其他3种预处理方法进行比较,证明了本文局部梯度轮廓变换方法的有效性;更进一步,利用基于协同表示CRD （collaborative representation-based detector）的检测器对增强后的影像和原始影像分别进行检测,分别取得的平均AUC值为0.990 7和0.977 5,检测结果再次验证了本文算法能够有效提升影像的检测精度;通过对比,实验数据表明本文所采用的局部梯度轮廓变换可减少约37.82%的时间复杂度。结论 本文算法通过将局部的梯度轮廓进行变换并用于指导原始影像的增强过程,使得影像的空间轮廓信息更为锐利,更为接近真实场景,从而获得异常检测结果的提升。     

人工神经网络遥感分类方法研究现状及发展趋势探析

从人工神经网络技术本身出发,概括了其在遥感分类中的研究现状,分析了人工神经网络遥感分类方法与其它分类方法相比具有的优势,介绍了人工神经网络遥感分类的一些主要应用,并进一步对人工神经网络遥感分类方法的发展趋势进行了展望。     

图像法空间运动物体尺寸测量的畸变特性研究

图像法用于空间运动物体尺寸测量时,由于图像传感器和物体存在相对运动关系,造成测量尺寸的畸变。在分析图像传感器动态测量过程的基础上,抽象出动态采集的数学模型,分析了传感器采集频率、被测物体运动速度等各个参数对动态采集畸变特性的影响,并进行了实验研究。研究表明:在动态模型的基础上优化采集参数可以减小畸变,进一步修正畸变数据可以提高动态测量的准确度。     

遥感图像恢复与遥感器MTF 在轨检测技术

遥感成像过程受到大气和成像系统中的光学、探测器和电子学子系统等的影响, 引起成像退化作用, 造成图像模糊, 降低了图像中信息的提取能力。图像恢复技术可以改善图像的质量, 提高图像信息提取能力。依据图像恢复技术的要求, 高精度成像系统调制传递函数(MTF) 是高质量图像恢复的基本条件。针对不同遥感器之间、同一遥感器不同时期存在的成像性能变化, 所引起成像系统MTF 变化的实际情况, 介绍了成像过程中系统MTF 在轨运检测方法。着重于介绍刃边法, 对刃边法的原理、刃边法检测对地物景观的要求等进行了详细分析, 对这一方法中有关图像景物的行扫描采样、扫描行的配准以及对所获得的边扩散函数的拟合等关键技术进行了详细介绍, 这些技术是保证较高精度获取遥感图像MTF 的基础。文章在介绍基于成像系统MTF 图像恢复技术后, 通过实验检验了方法的可行性, 结果表明以MTF 在轨检测为基础的图像恢复技术, 可以明显地提高遥感图像质量。     

Estimating the concentration of optically active constituents of sea water by Takagi-Sugeno models with quadratic rule consequents

Determining the concentrations of chlorophyll, suspended particulate matter and coloured dissolved organic matter in the sea water is basic to support the monitoring of upwelling phenomena, algae blooms, and changes in the marine ecosystem. Since these concentrations affect the spectral distribution of the solar light back-scattered by the water body, their estimation can be computed by using a set of remotely sensed multispectral measurements of the reflected sunlight. In this paper, the relation between the concentrations of interest and the average subsurface reflectances is modelled by means of a set of second-order Takagi-Sugeno (TS) fuzzy rules. Unlike first-order TS rules, which adopt linear functions as consequent, second-order TS rules exploit quadratic functions, thus improving the modelling capability of the rule in the subspace determined by the antecedent. First, we show how we can build a second-order TS model through a simple transformation, which allows estimating the consequent parameters using standard linear least-squares algorithms, and by adopting one of the most used methods proposed in the literature to generate first-order TS models. Then, we compare first-order and second-order TS models against mean square error and interpretability of rules. We highlight how second-order TS models allow us to achieve better approximation than first-order TS models though maintaining interpretability of the rules. Finally, we show how second-order TS models perform considerably better (the mean square error is lower by two orders of magnitude) than the specific implementations of radial basis function networks and multi-layer perceptron networks used in previous papers for the same application domain.     

Microwave remote sensing of physically buried objects in the Negev Desert: implications for environmental research

We report remote detections of physically buried specularly reflecting objects using microwave radar at two sites: Ashalim and Tseelim in the northern region of the Negev Desert, Israel. These detections provide confirmation that microwave subsurface remote sensing is a genuine phenomenon. At Ashalim, a scatterometer operating in the P-band (441 MHz, 68 cm) was mounted on a cherry picker truck at a height of 8 m and used to detect two triangular aluminum mesh reflectors (forming a 1-m square area reflector) buried down to a depth of 8 cm in dry sand. At Tseelim, the same scatterometer was mounted on an airplane flying at an altitude of 70 m and used to detect 1-m square aluminum reflectors (each one submerged at a different location along the airplane flight path) buried down to a depth of 20 cm. The experimental results compare favorably with a theoretical model that incorporates radar absorption effects arising in the sandy subsurface layer and radar interference effects arising from phase differences between reflections from the surface and buried reflector. The theoretical modeling also predicts the detection of a subsurface reflector down to a depth of about 4.4 m. This experiment and the associated modeling approach is the first of a series of planned experiments, which we outline for the detection and the theoretical evaluation of buried reflectors using remote microwave and VHF radar. We identify potential subject areas for environmental research.     

Graphical interactive generation of gravity and magnetic fields

This paper presents a MATLAB^®- based geopotential field generator called GamField that constructs and visualizes subsurface sources in 3-D space and computes their gravity and magnetic effects. GamField also computes anomaly gradients and remanent magnetization effects. The user inputs Cartesian prisms along with their physical properties to fabricate subsurface sources. Examples illustrating the utility of GamField for synthetic anomaly generation of gravity and magnetic fields are shown. ftp://ftp.ingv.it/pub/alessandro.pignatelli/Pignatelli     

遥感技术用于旅游资源调查及研究

遥感技术除了广泛应用于林业、农业、地质、气象等领域外,也应用于旅游资源调查、评价、规划与管理。实践证明,遥感在旅游区的自然风景、人文景观、服务设施和古迹考察方面具有巨大的优越性,取得了显著的成果,产生了良好的社会和
经济效益。     

通报距离对应召磁异搜潜概率的影响

为了分析应召搜潜过程中通报距离对搜潜概率的影响,推导出了计算潜艇位置分布概率的模型。通过该模型建立了通报距离与应召磁异搜潜概率的关系,并给出了一些典型情况下的计算结果。结果显示：应召磁异搜潜概率随通报距离的增加迅速下降,仅当通报距离较近且潜艇初始分布半径较小、航速较低时,应召磁异搜潜拥有较高的探测概率;从而表明通报距离对应召磁异搜潜概率影响较大,磁异探测不适合对远的通报距离的区域实施搜索     

Animation of water droplets moving down a surface

Rendering a scene containing water is among the most challenging aspects in the field of computer graphics. Researchers have developed a wide variety of algorithms for rendering water, but there still remain unaddressed problems due to water's multiformity and complex patterns of motion. This paper proposes a method for generating realistic animation of water droplets on transparent surfaces such as the windshield of a vehicle. One of the method's applications can be considered the animation of water droplets on a windshield, a process vital for drive simulators. The proposed method employs a particle system in a discrete environment to calculate the movement of water droplets on a surface, and environment mapping for indicating the property of transparency to quickly render scenes through transparent objects. Using the method, windshield wipers moving on a windshield and other obstacles moving against water droplets can also be taken into account. Fully computer‐generated animations and video compositions of water droplets on a windshield demonstrate the usefulness of the proposed method. Copyright © 1999 John Wiley & Sons, Ltd.     

闽北山区竹林分布及动态变化的地形分异特征研究

地形是影响植被分布和变化的重要因素之一,摸清竹资源的地形分异特征,对制定区域的竹资源可持续发展和生态环境建设战略具有重要意义。以福建省顺昌县为例,在GIS和遥感技术的支持下,结合遥感数据成图与地形因子叠加分析,对竹林分布及动态变化的地形分异特征进行了研究。研究结果表明：①竹林主要分布在海拔1 200 m以下,400~800 m区域竹林面积最大,在海拔800 m以下随着海拔的升高,竹林面积逐渐增大,在海拔800 m以上,随着海拔的升高竹林面积逐渐减少;②竹林集中分布在坡度6~25°区域,并且主要分布在半阳坡和半阴坡;③从1988~2007年间顺昌县竹林面积呈快速增长态势,净增加面积为1 6811.48 hm²;增加、减少和未变3种变化类型中,增加和未变的竹林面积随地形的变化呈先增加后减少的趋势;而减少的竹林面积随着海拔升高逐渐减少,随着坡度的变化先升高后减少,并且在各个坡向上变化不大。研究成果反映了自然与人为驱动力对顺昌县竹林面积的动态变化的影响,为该县竹林利用规划和生态建设提供了科学依据。     

OmniClimbers: Omni-directional magnetic wheeled climbing robots for inspection of ferromagnetic structures

This paper introduces Omniclimber, a new climbing robot with high maneuverability for inspection of ferromagnetic flat and convex human made structures. In addition to maneuverability, adaptability to various structures with different curvatures and materials are addressed. The conceptual and detailed design of OmniClimbers are presented and two prototypes of the robot are introduced. Several laboratory and field tests are reported, and the results are discussed.     

Merging complementary remote sensing datasets in the context of snow water equivalent reconstruction

Time series of snow covered area (SCA) estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat Enhanced Thematic Mapper (ETM+) were merged with a spatially explicit snowmelt model to reconstruct snow water equivalent (SWE) in the Rio Grande headwaters (3419 km²). A linear optimization scheme was used to derive SCA estimates that preserve the statistical moments of the higher spatial resolution (i.e. 30 m) ETM+ data and resolve the superior temporal signal (i.e. ∼ daily) of the MODIS data. It was found that merging the two SCA products led to an 8% decrease and an 18% increase in the basinwide SWE in 2001 and 2002, respectively, compared to the SWE estimated from ETM+ only. Relative to SWE simulations using only ETM+ data, the hybrid SCA estimates reduced the mean absolute SWE error by 17 and 84% in 2001 and 2002, respectively; errors were determined using intensive snow survey data and two separate methods of scaling snow survey field measurements of SWE to the 1-km model pixel resolution. SWE bias for both years was reduced by 49% and skewness was reduced from − 0.78 to 0.49. These results indicate that the hybrid SWE was closer to being an unbiased estimate of the measured SWE and errors were distributed more normally. The accuracy of the SCA estimates is likely dependent on the vegetation fraction.     

Representing short-term observations of moving objects by a simple visual language

In a variety of dynamical systems, formations of motion patterns occur. Observing colonies of animals, for instance, for the scientist it is not only of interest which kinds of formations these animals show, but also how they altogether move around. In order to analyse motion patterns for the purpose of making predictions, to describe the behaviour of systems, or to index databases of moving objects, methods are required for dealing with them. This becomes increasingly important since a number of technologies have been devised which allow objects precisely to get traced. However, the indeterminacy of spatial information in real world environments also requires techniques to approximate reasoning, for example, in order to compensate for small and unimportant distinctions which are due to noisy measurements. As a consequence, precise as well as coarse motion patterns have to be dealt with.A set of 16 atomic motion patterns is proposed. On the one hand, a relation algebra is defined on them. On the other hand, these 16 relations form the basis of a visual language using which motion patterns can easily be dealt with in a diagrammatic way. The relations are coarse but crisp and they allow imprecise knowledge about motion patterns to be dealt with, while their diagrammatic realisation also allow precise patterns to get handled. While almost all approaches consider motion patterns along arbitrary time intervals, this paper in particular focuses on short-term motion patterns as we permanently observe them in our everyday life.The bottom line of the current work, however, is yet more general. While it has been widely argued that it makes sense to use both sentential and diagrammatic representations in order to represent different things in the same system adequately (and hence differently), we argue that it makes even sense to represent the same things differently in order to grasp different aspects of one and the same object of interest from different viewpoints. We demonstrate this by providing both a sentential and a diagrammatic representation for the purpose of grasping different aspects of motion patterns. It shows that both representations complement each other.     

水利部旱情遥感监测系统建设与展望

遥感技术以其快速、经济和大空间范围获取的特点,已成为旱情监测的重要手段。介绍国家防汛指挥系统二期工程水利部旱情遥感监测系统的建设情况,包括旱情遥感监测模型、业务流程及系统的设计与开发等。系统实现全国旱情监测逐周生产、区域旱情1~3 d应急快速监测及逐月区域水体监测产品的生产。试运行表明全国旱情监测与国外同类产品结果一致或优于同类产品;区域旱情监测平均精度达到80%以上。最后,对旱情遥感监测系统未来发展进行展望。     

Floodplain water storage in the Negro River basin estimated from microwave remote sensing of inundation area and water levels

The objective of this study is to determine spatio-temporal variations of water volume over inundated areas located in large river basins using combined observations from the Synthetic Aperture Radar (SAR) onboard the Japanese Earth Resources Satellite (JERS-1), the Topex/Poseidon (T/P) altimetry satellite, and in-situ hydrographic stations. Ultimately, the goal is to quantify the role of floodplains for partitioning water and sediment fluxes over the great fluvial basins of the world. SAR images are used to identify the type of surface (open water, inundated areas, forest) and, hence, the areas covered with water. Both radar altimetry data and in-situ hydrographic measurements yield water level time series. The basin of the Negro River, the tributary which carries the largest discharge to the Amazon River, was selected as a test site. By combining area estimates derived from radar images classification with changes in water level, variations of water volume (focusing on a seasonal cycle) have been obtained. The absence of relationship between water volume and inundated area, reflecting the diverse and widely dispersed floodplains of the basin, is one of the main result of this study.     

三江平原洪河自然保护区湿地遥感分类研究

湿地是指陆地上常年或季节性积水或过湿的土地与生长栖息于其上的生物种群构成的独特生态系统,具有重要的生态价值与科学研究价值。研究选取重要国际湿地洪河保护区作为研究区,应用多期LandsatTM影像,采取基于专家经验的监督分类方法进行基于群落尺度的分类,取得了较好的分类效果。研究表明有效的影像增强处理和分类训练区的精确选择是监督分类的关键,基于专家辅助的地理信息系统空间分析方法有助于提高分类精度。依据遥感分类结果定量分析了高度自然状态下的北方半湿润区内陆淡水湿地群落类型的原始空间格局。研究揭示具有从沼泽湿地向草甸湿地明显过渡特征的小叶章-苔草群落占据整个保护区面积过高比例,显示该湿地保护区典型沼泽湿地的现状湿生环境退化特征比较明显,应尽早采取相应措施。     

Validation of daily MODIS snow cover maps of the Upper Rio Grande River Basin for the 2000-2001 snow year

Snow cover represents an important water resource for the Upper Rio Grande River Basin of Colorado and New Mexico. Accuracy assessment of MODIS snow products was accomplished using Geographic Information System (GIS) techniques. Daily snow cover maps produced from Moderate Resolution Imaging Spectroradiometer (MODIS) data were compared with operational snow cover maps produced by the National Operational Hydrologic Remote Sensing Center (NOHRSC) and against in situ Snowpack Telemetry (SNOTEL) measurements for the 2000-2001 snow season. Over the snow season, agreement between the MODIS and NOHRSC snow maps was high with an overall agreement of 86%. However, MODIS snow maps typically indicate a higher proportion of the basin as being snow-covered than do the NOHRSC snow maps. In particular, large tracts of evergreen forest on the western slopes of the San de Cristo Range, which comprise a large portion of the eastern margin of the basin, are more consistently mapped as snow-covered in the MODIS snow products than in the NOHRSC snow products. NOHRSC snow maps, however, typically indicate a greater proportion of the central portion of the basin, predominately in cultivated areas, as snow. Comparisons of both snow maps with in situ SNOTEL measurements over the snow season show good overall agreement with overall accuracies of 94% and 76% for MODIS and NOHRSC, respectively. A lengthened comparison of MODIS against SNOTEL sites, which increases the number of comparisons of snow-free conditions, indicates a slightly lower overall classification accuracy of 88%. Errors in mapping extra snow and missing snow by MODIS are comparable, with MODIS missing snow in approximately 12% of the cases and mapping too much snow in 15% of the cases. The majority of the days when MODIS fails to map snow occurs at snow depths of less than 4 cm.     

利用通用微机进行TM磁带数据转换的研究

主要介绍了利用小型机或微型机,将TM影像CCT磁带数据转换为微机磁盘数据,并利用普通微型计算机进行遥感图像数据读取的遥感图像显示处理过程。