Extraction of topographic deformation based on the 3D information of individual trees

ABSTRACT

Terrestrial laser scanning (TLS) has been used widely in topographic deformation monitoring, and the issue of deformation information extraction from multi-temporal point cloud data has high importance. Here, a method is developed for the extraction of topographic deformation in a forested area based on the 3D spatial information of individual trees. Initially, ground points are removed by using a local topographic surface fitting method, then individual trees are segmented using the PTrees algorithm; finally, the motion of individual trees is computed with a combination of global and local rigid-body transformations. Experimental validation results show that the proposed method is reliable to within a 0.12° maximum tilt error and 8.7 mm maximum displacement error. In addition, some inferences were drawn based on the original topography and the topographic deformation monitoring results. For example, a mining work-face was located beyond the eastern part of the study area, and trees growing in the middle part of this region of interest may face a survival challenge.     

On the extraction of 3D models from airborne video sensors for geolocation

Geolocation of a feature in a video sequence collected from a moving platform is an activity that must be undertaken in video exploitation, especially surveillance and reconnaissance applications. Examples of sensor systems that are the focus of this work include manned and unmanned aerial vehicles. The approach described here uses positional information from three sources to compute refined coordinates in three dimensions for any feature in the video sequence. These three sources are: first, sensor-platform metadata describing the likely sensor footprint based on sensor-platform positional and attitudinal information; second, 3D information of a scene inherent in a video sequence collected from a moving platform; and third, reference imagery of the region of interest that is geolocated and georectified such as aerial photography. We describe the overall steps involved in this process and the progress made to date.     

Capabilities and limitations of 2-dimensional and 3-dimensional numerical methods in modeling the fluid flow in sudden expansion microchannels

This paper deals with computational and experimental investigations into pressure-driven flow in sudden expansion microfluidic channels. Improving the design and operation of microfluidic systems requires that the capabilities and limitations of 2-dimensional (2-D) and 3-dimensional (3-D) numerical methods in simulating the flow field in a sudden expansion microchannel be well understood. The present 2-D simulation results indicate that a flow separation vortex forms in the corner behind the sudden expansion microchannel when the Reynolds number is very low (Re∼0.1). However, the experimental results indicate that this prediction is valid only in the case of a sudden expansion microchannel with a high aspect ratio (aspect ratio >> 1). 3-D computational fluid dynamics simulations are performed to predict the critical value of Re at which the flow separation vortex phenomenon is induced in sudden expansion microchannels of different aspect ratios. The experimental flow visualization results are found to be in good agreement with the 3-D numerical predictions. The present results provide designers with a valuable guideline when choosing between 2-D or 3-D numerical simulations as a means of improving the design and operation of microfluidic devices.     

临界状态下三维仿射控制系统的局部光滑镇定

讨论三维仿射非线性控制系统,在具有零和一对共轭纯虚数特征值的临界状态下的局部光滑镇定性.首先,应用非奇异线性状态变换和时间尺度变换,将系统转化成标准形式.之后,运用形式级数法的思想和扩展正则判别函数法,构造多组线性方程组,给出确定光滑控制律和闭环系统李雅普诺夫函数的一种方法,从而得到该标准化系统局部光滑镇定的充分条件.示例说明该方法是有效的.     

Design and fabrication of 3-dimensional helical structures in polydimethylsiloxane for flow control applications

Soft lithography in 2-dimensional (2-D) was developed for polymer MEMS applications about two decades back. The technique was highly useful for replication of microstructure molds using a soft polymeric material called PDMS (polydimethylsiloxane). From its inception the process has been widely applied to microfluidics, biochips, hybrid biomedical microdevices etc. However, it was limited to only surface microstructures and 3-Dimensional (3-D) soft lithography although performed by some research groups involved some very precise and expensive techniques like stereolithography etc. The exploration of soft lithography in three dimensions by using a replication technique with copper wires with micron size diameters was performed by our group relatively recently (Singh et al. in International conference on MEMS, IIT Madras, Chennai, 2009). In this work we have used the 3-D replication and molding technique to develop concentric solenoid patterns around micro-channels in the bulk of PDMS. The solenoidal paths of various pitches ranging from 0.4 to 1.2 mm have been replicated in PDMS using an innovatively designed fixture. The solenoids have been structurally characterized using an inverted fluorescence microscope (Nikon 80i) for dimensional parameters like pitch, length etc. Further, the solenoidal path designs have been simulated, optimized and fabricated around a central channel of 80 μ diameter and we have observed the repeatability of this fabrication process multiple times. The purpose of this architecture is to initiate valving action wherein fluid movement in the central channel can be restricted by filling the surrounding solenoidal track with compressed air at high pressure so that it can squeeze the centrally located micro-channel carrying the liquid. This valving structure may find a lot of applications in lab on chip devices, PCR biochips, biomedical micro-devices etc.     

A survey of methods for the extraction of information from Web resources

Earlier surveys of research in the field of extracting structured data from Web-pages are analyzed, and a scheme for the classification of the available approaches based on the extent of their application is proposed.     

Computational models of the emotions: from models of the emotions of the individual to modelling the emerging irrational behaviour of crowds

Computational models of emotions have been thriving and increasingly popular since the 1990s. Such models used to be concerned with the emotions of individual agents when they interact with other agents. Out of the array of models for the emotions, we are going to devote special attention to the approach in Adamatzky’s Dynamics of Crowd-Minds. The reason it stands out, is that it considers the crowd, rather than the individual agent. It fits in computational intelligence. It works by mathematical simulation on a crowd of simple artificial agents: by letting the computer program run, the agents evolve, and crowd behaviour emerges. Adamatzky’s purpose is to give an account of the emergence of allegedly “irrational” behaviour. This is not without problem, as the irrational to one person may seem entirely rational to another, and this in turn is an insight that, in the history of crowd psychology, has affected indeed the competition among theories of crowd dynamics. Quite importantly, Adamatzky’s book argues for the transition from individual agencies to a crowd’s or a mob’s coalesced mind as so, and at any rate for coalesced crowd’s agency.     

Estimation of the moisture content of bare soil from RADARSAT-1 SAR using simple empirical models

Synthetic Aperture Radar (SAR) provides a remote sensing tool to estimate soil moisture. Mapping surface soil moisture from the grey level of SAR images is a demonstrated procedure, but several factors can interfere with the interpretation and must be taken into account. The most important factors are surface roughness and the radar configuration (frequency, polarization and incidence angle). This Letter evaluates the influence of these variables for estimation of bare soil moisture using RADARSAT-1 SAR data. First, the parameters of two linear backscatter models, the Ji and Champion models (Ji et al . 1995, Champion 1996), were tested and the constants recalculated. rms error based on the backscattering coefficient was reduced from 6.12 and 6.48 dB to 4.28 and 1.68 dB for the Ji and Champion models respectively. Secondly, a new model is proposed which had an rms error of only 1.21 dB. The results showed a marked increase in accuracy compared with the previous models.     

一种自动特征提取的SAR图像水华识别方法

针对SAR图像水华识别中人工提取特征效率低的问题,提出了一种自动特征提取识别方法.该方法应用改进的K-means算法提取SAR图像暗斑,利用数据增强算法扩充暗斑图像集,并基于对水华暗斑图像特征的深入分析对DenseNet网络结构进行改进,以实现对水华暗斑与非水华暗斑更有效地识别区分.以太湖数据集作为实验数据,该方法获得了87.30％的总体精度,这一结果表明自动特征提取识别方法对于SAR图像水华识别的有效性.     

煤矿防治水害系统的三维空间数据模型研究

为了有效减少煤矿水害的发生,降低人员伤亡和财产损失,需要更加清晰准确地对煤矿井下各种相关地质体进行可视化建模,并在此基础上进行力学、数据挖掘等各类分析,研究了煤矿水害的主要成因,分析了常用的三维数据结构的特点和适用场合,指出在煤矿防治水害系统的构建中,针对水害的主要成因--含水层分布,断层分布、隔水层岩性组合,可以分剐使用针体模型、TEN、八又树等模型,使用混合数据结构实现对不同特点的地质体的可视化建模.     

Jackknife and bootstrap methods in the identification of dynamic models

A new criterion based on a Jackknife or a Bootstrap statistic is proposed for identifying non-parsimonious dynamic models (FIR, ARX). It is applicable for selecting the number of components in latent variable regression methods or the constraining parameter in regularized least squares regression methods. These meta parameters are used to overcome ill-conditioning caused by model over-parameterization, when fitted using prediction error or least squares methods. In all cases studied, using PLS for parameter estimation, the proposed criterion led to the selection of better models, in the mean square error sense, than when selected via cross-validation. The methodology also provides approximate confidence intervals for the model parameters and the step and impulse response of the system.     

Asymptotic methods in the theory of optimal control

The paper gives a survey of some works devoted to methods of the small parameter for the solution of optimal control problems. It is well known that these problems are difficult both for analytical and numerical approaches. Exact analytical solutions exist only for specific classes of optimal control problems. A numerical solution is possible for optimal program (open-loop) controls, but it becomes very difficult for obtaining synthesis if the order of the system is high. Therefore, approximate methods based on the small parameter techniques seem to be useful. By means of these methods, one can find approximate optimal control (both program and synthesis) for a number of optimal control problems which arise in applications. The paper presents some approaches and results in this direction obtained in the Computing Center and the Institute for Problems of Mechanics of the USSR Academy of Sciences in the past 10-15 years.     

Asymptotic methods in the optimal control of distributed systems

A short review of the various problems which arise in connection with the use of asymptotic methods in the optimal control of distributed systems is presented. We consider the cases when the asymptotic analysis comes from the state equation, or from the cost function, or both and also when the state equation is defined in perturbed domains.     

Frequency methods in the theory of pulse-modulated control systems

The frequency methods of studying stability of the nonlinear control systems with various kinds of pulse modulation were reviewed.     

从数据中提取生料浆配料过程运行控制的模糊规则

将减法聚类、神经网络、最相邻原则、对提取后的规则进行调整等方法相结合,从过程数据中自动提取出模糊规则,从而实现在氧化铝生料浆配料过程中将生料浆的各项质量指标控制在目标值范围内.某氧化铝厂的应用结果表明,所提取的模糊规则不仅具有良好的完备性和可解释性,同时可根据工况的变化自动调整各个控制回路的设定值,实现了该过程的优化运行.     

Automatic extraction of flood inundation areas from SAR images: a case study of Jilin,China during the 2017 flood disaster

Flood is one of the most frequent and widespread natural hazards globally, which can cause tremendous economic damage and human casualties. As such, flood event monitoring is essential, for which Synthetic Aperture Radar (SAR), with high spatial resolution as well as all-weather and all-time capabilities, can provide high-quality data support. However, algorithms for automatic flood inundation mapping that do not require ancillary data are limited. In this study, we propose a hybrid methodology that combines automatic thresholds selection, pixel- and object-based classification, and bidirectional region growing method for extracting flood inundation areas. This is a fully automatic approach that does not require the assistance of ancillary data. Firstly, the gamma distribution is used to estimate the probability density function (PDF) of ‘open water’ and to set thresholds. Then, we introduce a two-step classification approach, applying the pixel- and object-based classifications; the former is easy to implement with low computational complexity and stable performance, whereas the latter can reduce noise pixels and is less sensitive to SAR intrinsic speckle. The two-step classification is employed to yield core flooded and non-flooded regions that are used as seeds for region growing. Furthermore, we propose a bidirectional region growing approach that grows regions for flooded and non-flooded regions simultaneously to eliminate areas of uncertainty, while minimizing under- and over-detection. We verified the proposed approach by applying it to real flood events that occurred in Jilin, China on 13 July 2017 and 20 July 2017. The experimental results demonstrate the effectiveness and reliability of the proposed approach.     

One-step maskless grayscale lithography for the fabrication of 3-dimensional structures in SU-8

We propose a novel and simplified method to fabricate complex 3-dimensional structures in SU-8 photoresist using maskless grayscale lithography. The proposed method uses a Digital Micro-mirror Device (DMD^®) to modulate the light intensity across a single SU-8 photoresist layer. Top and back-side exposure are implemented in the fabrication of original structures such as cantilevers, covered channels with embedded features and arrays of microneedles. The fabrication of similar structures in SU-8 with other techniques often requires complex physical masks or the patterning of several stacked layers. The effects of critical process parameters such as software mask design, exposure and developing conditions on the quality of 3-D structures are discussed. A number of applications using bridges, cantilevers and micromixers fabricated using this methodology are explored.