基于运动方向及主轴的目标头部跟踪点稳定提取

光电成像跟踪过程中,目标距离较近时,将在视场中呈现出扩展目标的特性,其成像大小将随着距离的减小迅速增大甚至溢出视场.此时传统的质心、形心、相关跟踪会出现跟踪点跳动或漂移的问题,严重时甚至出现跟踪丢失的现象.针对这一问题,提出了结合目标运动与主轴方向的目标头部跟踪方式,通过跟踪目标头部确保背景在视场内占据定的比例,避免了目标充满视场而导致的分割失败或跟踪点在目标上滑动的情况.通过对目标的二值图像进行形态学滤波并计算头部的形心,进一步提高了头部跟踪点的稳定性.仿真测试与外场试验表明,该方法显著提高了跟踪的稳定性与可靠性.     

Coupled meshfree and fractal finite element method for mixed mode two‐dimensional crack problems

This paper presents a coupling technique for integrating the element‐free Galerkin method (EFGM) with the fractal finite element method (FFEM) for analyzing homogeneous, isotropic, and two‐dimensional linear‐elastic cracked structures subjected to mixed‐mode (modes I and II) loading conditions. FFEM is adopted for discretization of the domain close to the crack tip and EFGM is adopted in the rest of the domain. In the transition region interface elements are employed. The shape functions within interface elements which comprise both the EFG and the finite element (FE) shape functions, satisfies the consistency condition thus ensuring convergence of the proposed coupled EFGM–FFEM. The proposed method combines the best features of EFGM and FFEM, in the sense that no special enriched basis functions or no structured mesh with special FEs are necessary and no post‐processing (employing any path independent integrals) is needed to determine fracture parameters, such as stress‐intensity factors (SIFs) and T‐stress. The numerical results show that SIFs and T‐stress obtained using the proposed method are in excellent agreement with the reference solutions for the structural and crack geometries considered in the present study. Also, a parametric study is carried out to examine the effects of the integration order, the similarity ratio, the number of transformation terms, and the crack length to width ratio on the quality of the numerical solutions. A numerical example on mixed‐mode condition is presented to simulate crack propagation. As in the proposed coupled EFGM–FFEM at each increment during the crack propagation, the FFEM mesh (around the crack tip) is shifted as it is to the new updated position of the crack tip (such that FFEM mesh center coincides with the crack tip) and few meshless nodes are sprinkled in the location where the FFEM mesh was lying previously, crack‐propagation analysis can be dramatically simplified. Copyright © 2010 John Wiley & Sons, Ltd.     

A method for automated digital image-based tracking of delamination fronts in translucent glass fibre-laminated composite materials

A new automated digital image-based method for tracking both the position and shape of the crack front of delaminations in translucent glass fibre-laminated test specimens is proposed. The method is applicable to both fracture toughness tests and fatigue tests. The digital image-based algorithm identifies the newly formed crack area by the change in reflected light and then extracts both the crack front shape and the position. The method is used in a standard double cantilevered beam specimen test setup with the addition of light sources and a camera. The method does not rely on subjective test operator interpretations or calibrations. A reference pattern on the specimen is used to correctly map between the camera coordinate system and the specimen coordinate system, which makes the method insensitive to the camera position and camera or specimen movement during the test. Experimental test examples are provided, which shows that the whole crack front can be tracked with significantly higher accuracy than possible with existing methods.     

Estimation of AFM tip shape and status in linewidth and profile measurement

An atomic force microscopy image is a dilation of the specimen surface with the probe tip. Tips wear or are damaged as they are used. And AFM tip shape and position status make AFM images distorted. So it is necessary to characterize AFM tip shape and position parameters so as to reconstruct AFM images. A geometric model-based approach is presented to estimate AFM tip shape and position status by AFM images of test specimens and scanning electron microscope (SEM) images of AFM tip. In this model, the AFM tip is characterized by using a dynamic cone model. The geometric relationship between AFM tip and the sample structure is revealed in linewidth and profile measurement. The method can easily calculate the tip parameters including half-cone angle, installation angle, scanning tilting angle and curvature radius, and easily estimate the position status of AFM tip when AFM tip moves on the specimen. The results of linewidth and profile measurement are amended accurately through this approach.     

Quantitative reconstruction of refractive index distribution and imaging of glucose concentration by using diffusing light

We show that a two-step reconstruction method can be adapted to improve the quantitative accuracy of the refractive index reconstruction in phase-contrast diffuse optical tomography (PCDOT). We also describe the possibility of imaging tissue glucose concentration with PCDOT. In this two-step method, we first use our existing finite-element reconstruction algorithm to recover the position and shape of a target. We then use the position and size of the target as a priori information to reconstruct a single value of the refractive index within the target and background regions using a region reconstruction method. Due to the extremely low contrast available in the refractive index reconstruction, we incorporate a data normalization scheme into the two-step reconstruction to combat the associated low signal-to-noise ratio. Through a series of phantom experiments we find that this two-step reconstruction method can considerably improve the quantitative accuracy of the refractive index reconstruction. The results show that the relative error of the reconstructed refractive index is reduced from 20% to within 1.5%. We also demonstrate the possibility of PCDOT for recovering glucose concentration using these phantom experiments.     

一种新型的OFDM智能天线

根据自适应天线阵列理论，结合给定的参考波束的误差，引入虚拟干扰的概念，对目标波束图形状进行调整，提出一种新的可以应用于任意类型天线阵列的波束综舍算法．应用提出的新算法，在主辩和旁瓣位置都可以对波束进行有效的调节．最终获得阵列的最优权矢量，能够最小化目标波束图与参考波束图间的差异．理论分析与仿真结果表明，与现有的同类算法相比，该算法能更有效地获得与参考波束基本相符的波束．应用于OFDM智能天线系统时，对不同子载波频率上信号进行单独处理，利用该算法进行波束综合，能够在整个有效频段，使所有子载波上获得基本一致的阵列输出．     

Shape finding of cable systems using nonlinear displacement analysis approach

Abstract

An efficient method for finding initial shape of cable system by nonlinear displacement analysis is presented in this study. The supports of a cable system are first moved from a reference position to the specified boundary and the equilibrium position is then determined by the Newton‐Raphson iteration method. During analysis the large displacement effect is taken into account. The determined shape provides the geometry as well as the prestress distribution of the cable system. In general, the prestress of cable members may be too large or too small in the equilibrium position. So some modifications must be carried out in order to obtain a reasonable initial shape with suitable element length and prestress distribution. This method works well and can be applied to any cable system having an arbitrary form.     

Tunneling-stabilized magnetic force microscopy of bit tracks on ahard disk

A scanning tunneling microscope (STM) for surface magnetic force measurements on thin-film longitudinal magnetic storage media is described. The usual rigid PtIr tip of the STM was replaced by a flexible Fe-film tip and the tip position was stabilized near the surface of the sample using the STM feedback system as tunneling occurs between the tip and sample surface. Images of a CoCrTa thin-film hard disk showing 5 μm×3 μm bit tracks written by the ferrite head of a computer disk drive are presented. The images shown are comparable to images of the bit tracks on textured surfaces using either ferrofluid decoration or other magnetic force microscopy (MFM) imaging techniques. The sensitivity of the Fe-film tip was such that the influence on the image due to magnetic forces was larger than the influence due to sample surface topography     

Evaluation of test procedures for determining servo compatibilityof heads and media in magnetic disk drives

We evaluate a testing specification proposed by the National Storage Industry Consortium's (NSIC) Extremely High Density Recording (EHDR) group for evaluating head and media compatibility for servo performance in magnetic disk drives. These tests use average amplitude and average noise profile measurements across isolated tracks to predict the shape, linearity, noise, and long-term stability of position error signal (PES) patterns. We compare the predictions from these tests to measurements from null and amplitude PES patterns written on a spin-stand. Results show average PES-profile prediction errors of 1%-2% track width and noise level prediction within a factor of 2. We present data from tests for long-term stability of the magnetoresistive (MR) read element after repeated write cycles by the inductive write head. In the set of heads we tested, the MR head's center and effective width changed only slightly. Although we evaluated the NSIC specification for MR read elements, the specification should be equally valid for other read head types also, as long as the PES patterns are similar     

Effects of spatial modes on ladar vibration signature estimation

Ladar-based vibrometry has been shown to be a powerful technique in enabling the plant identification of machines. Rather than sensing the geometric shape of a target laser vibrometers sense motions of the target induced by moving parts within the system. Since the target need not be spatially resolved, vibration can be sensed reliably and provide positive identification at ranges beyond the imaging limits of the aperture. However, as the range of observation increases, the diffraction-limited beam size on the target increases as well, and may encompass multiple vibrational modes on the target's surface. As a result, vibration estimates formed from large laser footprints illuminating multiple modes on a vibrating target will experience a degradation. This degradation is manifest as a spatial low-pass filtering effect: high-order mode shapes, associated with high-frequency vibrations, will be averaged out while low-frequency vibrations will be affected less. A model to predict this phenomenology is proposed for both pulse-pair and cw vibrometry systems. The cw model is compared to results obtained using an off-the-shelf laser vibrometry system.     

呼吸裂纹梁非线性动力特性研究

疲劳裂纹是结构损伤的重要形式,是引起结构破坏的主要因素之一。建立了含非对称疲劳裂纹梁的非线性数值分析模型,采用奇异单元模拟裂纹尖端的效应,使用无摩擦的接触单元模拟疲劳裂纹的张开闭合特性,研究了结构在简谐荷载激励下的非线性动力特性。以悬臂梁为例分别分析了外部激励频率、裂纹深度以及裂纹位置等参数的变化对系统非线性行为的影响,重点讨论了系统的亚谐、超谐等共振现象,并且提出了系统频率的相对幅值用于辨识裂纹深度的方法。研究结果为裂纹结构的损伤识别提供了一定的理论基础和参考。     

Manipulation by dipole probe

A dipole probe is fabricated to manipulate millimeter- to submillimeter-sized objects. A tungsten needle, an alumina tube and a stainless tube are arranged concentrically in order inside the probe. The tip of the stainless tube is ground to form a needle. They are embedded in an epoxy resin and the tip of the probe is shaped hemispherically. The probe has two electrodes, a tungsten needle and a stainless steel needle, inside it. The probe can attract objects by gradient force like a bipolar electrostatic chuck. The attraction force is measured as a function of the applied voltage, and they are compared with those calculated by a 3D FEM. Both the experimental values and the calculated values are proportional to the square of the applied voltage. The determined values are, however, three times greater than those by the calculated values. The difference is ascribed to the incomplete shape of the probe model and the difference of dielectric constants of materials. The probe can attract both conductive gold particles and dielectric foam styrene particles. The probe is placed above the particle and a voltage supplier is turned on. The particle jumps up and adheres at the tip of the probe. The adhesive position is not on the center axis of the probe but the opposite side to the stainless needle against the center of the probe. The distances from the center of the probe are at a range of 0.4–1.05 mm for 20 experiments. The FEM calculation shows that maximum attraction force is for the particle placed at the opposite side to the stainless needle. Release is possible only by turning the voltage supplier off. The particle moves to the bottom of the probe, and falls after 1–2 s. The delay is due to the attenuation period of electrons accumulated at the surface of the probe.     

Discrete element modelling of a bucket elevator head pulley transition zone

This paper presents the results of discrete element simulations applied to a bucket elevator model with particular reference to the head pulley transition zone. This is the first stage in a larger study to better understand the mechanics of bucket elevator operation with reference to the discharge of particles at the head end. At the head end two issues arise; mechanically, the buckets are bolted to the conveying media (typically a fabric reinforced belt) and at the point of belt to headpulley tangency, the tip of the bucket undergoes a theoretical step change in velocity. This theoretical step change results in a classical under-damped response in the buckets tip velocity. In undergoing this motion, there are stresses that are passed to the carcass of the conveying media; understanding the magnitude of these stresses is one longer term goal of this research allowing a quantitative basis for the existing qualitative design guidelines such as (Handbook for conveyor and elevator belting, Apex Belting Pty Ltd). The discharge of the bulk material from the bucket has been addressed Beverly et al. (Bulk Solids Handling, 1983) but this analysis is dependent on simple, but common, bucket geometry and ignores the initial transition to the headpulley. Ignoring the transition with a low speed discharge elevator is not likely to impact on the predicted discharge pattern, however with high speed discharge elevators, the destabilising effect of the transition is expected to promote premature discharge of bulk material from the bucket. Depending on the design of the elevator casing this early discharge may or may not impact on the overall conveying efficiency.     

Vibrating interventional device detection using real-time 3-D color Doppler

Ultrasound image guidance of interventional devices during minimally invasive surgery provides the clinician with improved soft tissue contrast while reducing ionizing radiation exposure. One problem with ultrasound image guidance is poor visualization of the device tip during the clinical procedure. We have described previously guidance of several interventional devices using a real-time 3-D (RT3-D) ultrasound system with 3-D color Doppler combined with the ColorMark technology. We then developed an analytical model for a vibrating needle to maximize the tip vibrations and improve the reliability and sensitivity of our technique. In this paper, we use the analytical model and improved radiofrequency (RF) and color Doppler filters to detect two different vibrating devices in water tank experiments as well as in an in vivo canine experiment. We performed water tank experiments with four different 3- D transducers: a 5 MHz transesophageal (TEE) probe, a 5 MHz transthoracic (TTE) probe, a 5 MHz intracardiac catheter (ICE) transducer, and a 2.5 MHz commercial TTE probe. Each transducer was used to scan an aortic graft suspended in the water tank. An atrial septal puncture needle and an endomyocardial biopsy forceps, each vibrating at 1.3 kHz, were inserted into the vascular graft and were tracked using 3-D color Doppler. Improved RF and wall filters increased the detected color Doppler sensitivity by 14 dB. In three simultaneous planes from the in vivo 3-D scan, we identified both the septal puncture needle and the biopsy forceps within the right atrium using the 2.5 MHz probe. A new display filter was used to suppress the unwanted flash artifact associated with physiological motion.     

Automatic target tracking in FLIR image sequences using intensity variation function and template modeling

A novel automatic target tracking (ATT) algorithm for tracking targets in forward-looking infrared (FLIR) image sequences is proposed in this paper. The proposed algorithm efficiently utilizes the target intensity feature, surrounding background, and shape information for tracking purposes. This algorithm involves the selection of a suitable subframe and a target window based on the intensity and shape of the known reference target. The subframe size is determined from the region of interest and is constrained by target size, target motion, and camera movement. Then, an intensity variation function (IVF) is developed to model the target intensity profile. The IVF model generates the maximum peak value where the reference target intensity variation is similar to the candidate target intensity variation. In the proposed algorithm, a control module has been incorporated to evaluate IVF results and to detect a false alarm (missed target). Upon detecting a false alarm, the controller triggers another algorithm, called template model (TM), which is based on the shape knowledge of the reference target. By evaluating the outputs from the IVF and TM techniques, the tracker determines the real coordinates of one or more targets. The proposed technique also alleviates the detrimental effects of camera motion, by appropriately adjusting the subframe size. Experimental results using real-life long-wave and medium-wave infrared image sequences are shown to validate the robustness of the proposed technique.     

Analysis of a vibrating interventional device to improve 3-D colormark tracking

Ultrasound guidance of interventional devices during minimally invasive surgical procedures has been investigated by many researchers. Previously, we extended the methods used by the Colormark tracking system to several interventional devices using a real-time, three-dimensional (3-D) ultrasound system. These results showed that we needed to improve the efficiency and reliability of the tracking. In this paper, we describe an analytical model to predict the transverse vibrations along the length of an atrial septal puncture needle to enable design improvements of the tracking system. We assume the needle can be modeled as a hollow bar with a circular cross section with a fixed proximal end and a free distal end that is suspended vertically to ignore gravity effects. The initial results show an ability to predict the natural nodes and antinodes along the needle using the characteristic equation for free vibrations. Simulations show that applying a forcing function to the device at a natural antinode yields an order of magnitude larger vibration than when driving the device at a node. Pulsed wave spectral Doppler data was acquired along the distal portion of the needle in a water tank using a 2-D matrix array transesophageal echocardiography probe. This data was compared to simulations of forced vibrations from the model. These initial results suggest that the model is a good first order approximation of the vibrating device in a water tank. It is our belief that knowing the location of the natural nodes and antinodes will improve our ability to drive the device to ensure the vibrations at the proximal end will reach the tip of the device, which in turn should improve our ability to track the device in vivo.     

Radar automatic target recognition using complex high-resolution range profiles

Radar high-resolution range profile (HRRP) has received intensive attention from the radar automatic target recognition (RATR) community. Usually, since the initial phase of a complex HRRP is strongly sensitive to target position variation, only the amplitude information in complex HRRPs is used for RATR, whereas the phase information is discarded. However, the remaining phase information except for initial phases in complex HRRPs may also contain valuable target discriminant information. RATR using complex HRRPs is discussed. The complex HRRPs' feature subspace within each target-aspect sector is extracted via principal component analysis as the corresponding template during the training phase; while in the test phase we decide that a test sample belongs to the feature subspace which has the test sample's minimum reconstruction error approximation. It is shown that the whole process is independent of the initial phases, but exploits the remaining phase information in complex HRRPs. Furthermore, to make the proposed recognition method more practical, a fast time-shift compensation algorithm is proposed. In the recognition experiments based on measured data, the proposed recognition method using complex HRRPs achieves better recognition results than that using only the amplitude vectors of the complex HRRPs     

Fiber-Grating-Based Vision System for Real-Time Tracking, Monitoring, and Obstacle Detection

There is a real need to develop a sensory system that can monitor and track the behavioral status of a person in real time while protecting his/her privacy. In addition, it is important to have the ability to detect stationary and moving objects in real time to support dynamic navigation needs for mobile robots. This paper describes the development of intelligent fiber-grating (FG)-based 3-D vision sensory system that enables real-time object detection, monitoring, and tracking. This system uses the richness and the strength of the vision while reducing the data load and computational cost by encoding the working space using a limited number of spatially interrelated 2-D laser spots. The sensor system generates the laser spots by projecting a coherent laser beam on two perpendicularly overlaid layers of FGs. The presence of a target within the visible operational view of the sensor disturbs the part of the projected laser spots' pattern where the target appeared. By calculating the displacement of the disturbed spots within the CCD image plane, the sensor system can detect, in a short time, an object/human and provide relevant information in terms of range, approximate shape, and position. To facilitate faster detection and real-time tracking, the author has developed two strategies that decompose the working space into zones and virtual planes     

3-D ultrasound volume reconstruction using the direct frame interpolation method

A new method for 3-D ultrasound volume reconstruction using tracked freehand 3-D ultrasound is proposed. The method is based on solving the forward volume reconstruction problem using direct interpolation of high-resolution ultrasound B-mode image frames. A series of ultrasound B-mode image frames (an image series) is acquired using the freehand scanning technique and position sensing via optical tracking equipment. The proposed algorithm creates additional intermediate image frames by directly interpolating between two or more adjacent image frames of the original image series. The target volume is filled using the original frames in combination with the additionally constructed frames. Compared with conventional volume reconstruction methods, no additional filling of empty voxels or holes within the volume is required, because the whole extent of the volume is defined by the arrangement of the original and the additionally constructed B-mode image frames. The proposed direct frame interpolation (DFI) method was tested on two different data sets acquired while scanning the head and neck region of different patients. The first data set consisted of eight B-mode 2-D frame sets acquired under optimal laboratory conditions. The second data set consisted of 73 image series acquired during a clinical study. Sample volumes were reconstructed for all 81 image series using the proposed DFI method with four different interpolation orders, as well as with the pixel nearest-neighbor method using three different interpolation neighborhoods. In addition, volumes based on a reduced number of image frames were reconstructed for comparison of the different methods' accuracy and robustness in reconstructing image data that lies between the original image frames. The DFI method is based on a forward approach making use of a priori information about the position and shape of the B-mode image frames (e.g., masking information) to optimize the reconstruction procedure and to reduce computation times and memory requirements. The method is straightforward, independent of additional input or parameters, and uses the high-resolution B-mode image frames instead of usually lower-resolution voxel information for interpolation. The DFI method can be considered as a valuable alternative to conventional 3-D ultrasound reconstruction methods based on pixel or voxel nearest-neighbor approaches, offering better quality and competitive reconstruction time.