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Development of a Tomography Technique for Assessment of the Material Condition of Concrete Using Optimized Elastic Wave Parameters

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MATERIALS 2016年第4期9卷 291-291页

作者： Chai, Hwa Kian Liu, Kit Fook Behnia, Arash Yoshikazu, Kobayashi Shiotani, Tomoki Univ Malaya Dept Civil Engn Kuala Lumpur 50603 Malaysia Monash Univ Malaysia Sch Engn Discipline Civil Engn Selangor 46150 Malaysia Nihon Univ Dept Civil Engn Tokyo 1018308 Japan Kyoto Univ Dept Civil & Earth Resources Engn Kyoto 6158530 Japan

Concrete is the most ubiquitous construction material. Apart from the fresh and early age properties of concrete material, its condition during the structure life span affects the overall structural performance. Therefore, development of techniques such as non-destructive testing which enable the investigation of the material condition, are in great demand. Tomography technique has become an increasingly popular non-destructive evaluation technique for civil engineers to assess the condition of concrete structures. In the present study, this technique is investigated by developing reconstruction procedures utilizing different parameters of elastic waves, namely the travel time, wave amplitude, wave frequency, and Q-value. In the development of algorithms, a ray tracing feature was adopted to take into account the actual non-linear propagation of elastic waves in concrete containing defects. Numerical simulation accompanied by experimental verifications of wave motion were conducted to obtain wave propagation profiles in concrete containing honeycomb as a defect and in assessing the tendon duct filling of pre-stressed concrete (PC) elements. The detection of defects by the developed tomography reconstruction procedures was evaluated and discussed.

关键词： tomography honeycomb pre-stressed concrete (PC) imaging algorithm ray tracing wave propagation

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Damage localization in metallic plate structures using edge-reflected lamb waves

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SMART MATERIALS AND STRUCTURES 2016年第8期25卷

作者： Ebrahimkhanlou, A. Dubuc, B. Salamone, S. Univ Texas Austin Smart Struct Res Lab Dept Civil Environm & Architectural Engn 10100 Burnet RdBldg 177 Austin TX 78758 USA

This paper presents a model-based guided ultrasonic waves imaging algorithm, in which multiple ultrasonic echoes caused by reflections from the plate's boundaries are leveraged to enhance imaging performance. An analytical model is proposed to estimate the envelope of scattered waves. Correlation between the estimated and experimental data is used to generate images. The proposed method is validated through experimental tests on an aluminum plate instrumented with three low profile piezoelectric transducers. Different damage conditions are simulated including through-thickness holes. Results are compared with two other imaging localization methods, that is, delay and sum and minimum variance.

关键词： guided ultrasonic waves structural health monitoring imaging algorithm

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A Millimeter Wave imaging Radar Simulation Based on the GPU 8

A Millimeter Wave Imaging Radar Simulation Based on the GPU

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Proceedings 2015 8 International Congress on Image and Signal Processing (CISP)

作者： Zhao, Yongjia Hu, Xuerui Liu, Weihua Beihang Univ Sch Automat Sci & Elect Engn Beijing Peoples R China

ISBN: (纸本)9781467390989

In this paper, the procedure of a millimeter wave imaging radar simulation based on the GPU is presented to obtain radar images rapidly and effectively. An intuitionistic vertex pre-excursion algorithm is proposed to generate radar images with shadow during a single-step process by taking advantage of the perspective projection function inside the GPU. C for graphics (Cg) is adopted to design programs for vertex and fragment shaders, which achieves a high rendering speed. Locations and lighting of vertices are specified by geometry positions and colors according to the radar response (returned power), respectively. The method is greatly useful for the development of high speed radar imaging simulations.

关键词： remote sensing millimeter wave radar imaging simulaiton imaging algorithm GPU

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Range-resolution improvement for spaceborne/airborne bistatic synthetic aperture radar using stepped-frequency chirp trains

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IET SIGNAL PROCESSING 2015年第4期9卷 377-386页

作者： Xu, Haisheng Wang, Jian Yuan, Jian Wang, Robert Shan, Xiuming Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China Chinese Acad Sci Inst Elect Spaceborne Microwave Remote Sensing Syst Dept Beijing 100190 Peoples R China

In this paper, a stepped-frequency spaceborne/airborne bistatic synthetic aperture radar (SFSA-BiSAR) configuration is proposed to show to improve the range resolution of BiSAR. First, the geometry and the signal model of SFSA-BiSAR are formulated, and then an analytical bistatic point target reference spectrum (BPTRS) is derived. Second, based on the developed BPTRS, two imaging algorithms called combination-before-focusing algorithm (CBFA) and combination-after-focusing algorithm (CAFA) are proposed to obtain BiSAR images with improved range resolution. CBFA uses sub-band combination to obtain synthetic BPTRS, and then uses a new bistatic frequency-domain algorithm (BFDA) to obtain the improved BiSAR image, whereas CAFA first uses the BFDA to focus all the sub-pulses, and then uses sub-image combination to obtain the improved BiSAR image. Both of the two algorithms can focus the SFSA-BiSAR signal well and comparison simulations are performed to verify the authors' conclusion. Computation loads are also calculated to compare the two algorithms and show that CAFA uses less floating-point operations than CBFA. Besides, some important parameters of SFSA-BiSAR are analysed both theoretically and numerically to provide a reference for system design.

关键词： synthetic aperture radar radar imaging frequency-domain analysis radar resolution range-resolution improvement spaceborne-airborne bistatic synthetic aperture radar stepped-frequency chirp trains SFSA-BiSAR configuration signal model analytical bistatic point target reference spectrum analytical BPTRS imaging algorithm combination-before-focusing algorithm CBFA combination-after-focusing algorithm CAFA sub-band combination synthetic BPTRS bistatic frequency-domain algorithm BFDA improved BiSAR image sub-image combination floating-point operations system design

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Focusing one-stationary bistatic forward-looking synthetic aperture radar with squint minimisation method

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IET RADAR SONAR AND NAVIGATION 2015年第8期9卷 927-932页

作者： Ma, Chao Gu, Hong Su, Weimin Zhang, Xiaohu Li, Chuanzhong Nanjing Univ Sci & Technol Inst Elect Engn & Optoelect Technol Nanjing 210094 Jiangsu Peoples R China

This study deals with the imaging problem of one-stationary bistatic forward-looking synthetic aperture radar (BFSAR). This BFSAR has extensive potential applications, such as self-navigation and self-landing in the airport. However, the forward-looking (or squint) angle is usually large in one-stationary BFSAR. It causes large range migration and strong range dependence on the secondary range compression term. Therefore it is difficult to use traditional imaging algorithms to focus one-stationary BFSAR. To solve this problem, an imaging algorithm based on squint minimisation method is proposed in this study. The squint minimisation operation can shear the high forward-looking angle data spectrum and decrease the coupling between range and azimuth. Then, the authors derive a modified range Doppler algorithm (RDA) to focus the sheared data. Numerical simulations show that by combining squint minimisation method and modified RDA, the raw data of one-stationary BFSAR can be well imaged.

关键词： radar imaging synthetic aperture radar minimisation Doppler radar data compression image coding numerical analysis one-stationary bistatic forward-looking synthetic aperture radar BFSAR squint minimisation method self-navigation self-landing squint angle large range migration strong range dependence secondary range compression imaging algorithm high forward-looking angle data spectrum modified range Doppler algorithm RDA numerical simulations modified RDA

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An algorithm for inverse synthetic aperture imaging lidar based on sparse signal representation

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LASER PHYSICS 2014年第12期24卷 125007-125007页

作者： Ren, X. Z. Sun, X. M. Henan Univ Technol Coll Informat Sci & Engn Zhengzhou 450001 Peoples R China Henan Tech Coll Construct Dept Informat Engn Zhengzhou 450064 Peoples R China

In actual applications of inverse synthetic aperture imaging lidar, the issue of sparse aperture data arises when continuous measurements are impossible or the collected data during some periods are not valid. Hence, the imaging results obtained by traditional methods are limited by high sidelobes. Considering the sparse structure of actual target space in high frequency radar application, a novel imaging method based on sparse signal representation is proposed in this paper. Firstly, the range image is acquired by traditional pulse compression of the optical heterodyne process. Then, the redundant dictionary is constructed through the sparse azimuth sampling positions and the signal form after the range compression. Finally, the imaging results are obtained by solving an ill-posed problem based on sparse regularization. Simulation results confirm the effectiveness of the proposed method.

关键词： synthetic aperture lidar sparse signal representation imaging algorithm

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Space-Surface BiSAR based on GNSS Signal: Synchronization, imaging and Experiment Result

Space-Surface BiSAR based on GNSS Signal: Synchronization, I...

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IEEE Radar Conference - From Sensing to Information

作者： Tian, Weiming Zhang, Tian Zeng, Tao Hu, Cheng Long, Teng Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China

ISBN: (纸本)9781479920358

This paper presents a novel synchronization method for space-surface BiSAR (SS-BiSAR) illuminated by navigation satellites. Direct signal is utilized to obtain theoretical Doppler and navigation data. According to the navigation data and receiver position, theoretical Doppler history can be calculated. Comparing the tracking result and theoretical result, phase synchronization error could be estimated. After phase synchronization error is estimated and compensated, echo of SS-BiSAR is focused by bistatic back-projection algorithm. The proposed method has been verified by SS-BiSAR imaging experiment based on BeiDou signal.

关键词： bistatic SAR GNSS signal imaging algorithm synchronization

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An Improved Frequency Domain Focusing Method in Geosynchronous SAR

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2014年第9期52卷 5514-5528页

作者： Hu, Cheng Long, Teng Liu, Zhipeng Zeng, Tao Tian, Ye Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China China Acad Elect & Informat Technol Beijing 100041 Peoples R China

Geosynchronous (GEO) SAR has been proposed as a means for obtaining observations of the Earth with finer temporal sampling than possible with a single satellite from a lower orbit. However, standard algorithms developed for low-Earth-orbit SAR imaging are inadequate for GEO, where the typical assumptions of quasi-linear trajectory and "stop-and-go" transmit/receive propagation break down because of the long integration time and the very long range between the satellite and the Earth. This paper proposes a curved trajectory model to overcome these limitations and considers the impact of the "stop-and-go" assumption. According to the proposed range model, an accurate 2-D analytical spectrum is deduced under the curved trajectory model based on a series reversion method, leading to an improved frequency domain imaging algorithm involving a high-order-phase coupling function and a range migration correction function. An adaptive azimuth compression function overcomes the space variance for large-scene focusing. Simulation results validate that the improved imaging algorithm performs well over the expected range of applicability for GEO SAR.

关键词： Analytical spectrum curved trajectory model geosynchronous synthetic aperture radar (GEO SAR) imaging algorithm "stop-and-go" assumption

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One-Stationary Bistatic Forward-Looking SAR imaging Based on Improved Nonlinear Chirp Scaling algorithm

One-Stationary Bistatic Forward-Looking SAR Imaging Based on...

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6th International Congress on Image and Signal Processing (CISP)

作者： Liu Huan Zhou Jianxiong Fu Qiang Natl Univ Def Technol ATR Lab Changsha Hunan Peoples R China

ISBN: (纸本)9781479927630

The forward-looking imaging problem of synthetic aperture radar (SAR) can be resolved by adopting the bistatic configuration. A bistatic configuration with a stationary transmitter and a forward-looking receiver is introduced and the two-dimensional spectrum is derived, and then an improved nonlinear chirp scaling algorithm is used to focus the data. The imaging quality is compared with the traditional nonlinear chirp scaling algorithm;the simulation results verify the 2D imaging ability of the proposed method.

关键词： bistatic SAR forward-looking nonlinear chirp scaling imaging algorithm

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Pressure mapping system based on guided waves reflection

Pressure mapping system based on guided waves reflection

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Conference on Health Monitoring of Structural and Biological Systems

作者： Quaegebeur, Nicolas Masson, Patrice Brault, Louis-Philippe Beaudet, Nicolas Sarret, Philippe Univ Sherbrooke GAUS Dept Mech Engn Sherbrooke PQ J1K 2R1 Canada Univ Sherbrooke CNS Dept Neurosci Sherbrooke PQ J1K 2R1 Canada

ISBN: (纸本)9780819494788

In this paper, a guided wave-based pressure mapping system is presented for medical and touch-screen applications. Piezoceramics are used as actuators and to measure the reflected waves due to an added mass or local pressure, responsible for a change of local surface impedance. SHM imaging algorithms are implemented in order to obtain cartography of the reflections and deduce the presence, localization and intensity of pressure spots. Analytical and numerical models are validated on an aluminum plate prototype instrumented using 1 actuator and 2 sensors. It is observed that imaging of single or multiple pressure spots is achieved using both A0 and S0 modes around 300 kHz with a resolution of 0.5 mm.

关键词： guided waves added mass pressure mapping piezoceramics touchscreen and medical sensor imaging algorithm real-time application reflection and scattering

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