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A great number of bridges have been built in the world, which are very important for economic and society developments. Thus, the bridge monitoring is vital and is also a hot topic in recent years. Many bridge monitoring methods have been presented to monitor the bridge vibration. For example, some bridge monitoring methods require the sensors directly contact with the bridge, which might be difficult to install and maintain. In addition, some remote monitoring instruments are expensive and sensitive to the environment. In this paper, a bridge monitoring radar with a central frequency of 36.05 GHz is devised based on a millimeter-wave technology to measure the bridge vibration. It has a super-range resolution of 0.5 m and a high deformation measure precision of 56 μm. Experiments on a high-speed railway bridge and a large cable suspended bridge are performed to verify the effectiveness of the radar interferometry for accurate and precise monitoring of the vibration types and magnitudes of these bridges.

A general zero attraction (GZA) proportionate normalized maximum correntropy criterion (GZA-PNMCC) algorithm is devised and presented on the basis of the proportionate-type adaptive filter techniques and zero attracting theory to highly improve the sparse system estimation behavior of the classical MCC algorithm within the framework of the sparse system identifications. The newly-developed GZA-PNMCC algorithm is carried out by introducing a parameter adjusting function into the cost function of the typical proportionate normalized maximum correntropy criterion (PNMCC) to create a zero attraction term. The developed optimization framework unifies the derivation of the zero attraction-based PNMCC algorithms. The developed GZA-PNMCC algorithm further exploits the impulsive response sparsity in comparison with the proportionate-type-based NMCC algorithm due to the GZA zero attraction. The superior performance of the GZA-PNMCC algorithm for estimating a sparse system in a non-Gaussian noise environment is proven by simulations.

A large number of studies have been conducted to investigate macroscopic responses of gravelly soils using large-scale triaxial compression tests; however, particle-level responses of gravelly soils under triaxial compression remain poorly explored. Here, we reported a series of large-scale triaxial compression tests on uniformly graded gravels subjected to a low to medium range of confining pressures (200-800 kPa). We further investigated the particle-level responses of the gravels using the combined triaxial compression test with computed tomography (CT) scan. A computer image analysis program was developed to analyze the CT images, providing visualized and quantitative particle displacement and rotation. Based on the experimental results, the stress-strain relationships at different confining pressures and the microscopic characteristics of the gravels (e.g., changes in internal structures) under different deviator stress levels were discussed. The changes in particle-level responses were linked to those in macroscopic responses. From both macroscopic and microscopic analyses, some insights into the underlying mechanism of the stress-strain relationships were provided. [ABSTRACT FROM AUTHOR]

In this paper, a mm-wave radar is devised to monitor the micro-deformation of bridges and its performance is verified via monitoring a highway and a freight railway bridges. The radar interferometry technology is utilized to develop the compact and portable mm-wave radar. Experiments are set up to monitor a highway bridge around Beijing-Tianjin expressway which is near the sixth ring roads of Beijing and a Daqin freight railway bridge in Yanqing, Beijing. The experimental results demonstrate that the devised radar can detect the micro-deformation of the bridge vibration with a super-resolution and high precision, making the mm-wave radar promising for bridge monitoring, dam monitoring, debris flow monitoring applications. [ABSTRACT FROM AUTHOR]

Drained triaxial compression tests were carried out for a well-graded coarse granular soil (CGS) to investigate the effect of the initial specific volume on the location of the critical state line (CSL). A family of parallel CSLs in the v ∼ log p′ plane was observed for the well-graded CGS, indicating that it exhibited transitional behavior. The degree of transitional behavior was quantified from the relationship between the intercepts of the CSLs and the initial specific volumes, giving a value of 0.59, which indicated a substantially transitional behavior. The observations of the CSL pattern in the CGS illustrated that transitional behavior could be extended to large-sized granular soils, beyond the usual transitional soils that have been observed so far, which generally have gradings between those of clean sand and plastic clay. [ABSTRACT FROM AUTHOR]

The influences of particle breakage on the position of the critical state line (CSL) were systematically investigated in this paper through a series of large-scale triaxial compression tests on Tacheng rockfill material (TRM). It was found that the critical-state stress ratio of TRM (i.e., the gradient of the CSL in the p - q space) was approximately regarded as a constant. In the e - log p space, the CSL of TRM descended with a decrease in the initial void ratio, whereas the gradient of the CSL was constant. A procedure was established for evaluating the critical state point at a same particle breakage, which comprised the breakage critical state line (BCSL). An increase of the particle breakage led to not only a vertical translation but also a rotation on the BCSL of TRM in the e - log p space, which was similar to the observation of Dog's Bay sand. Consequently, the initial gradation (or the corresponding initial void ratio) was the dominant factor that affected the position of the CSL of TRM in the e - log p space. [ABSTRACT FROM AUTHOR]

The authors providea response to a commentary about their study concerning the transitional behaviors of granular soils. Topics discussed include the dependence of the critical-state line on the initial void ratio, reanalysis of the drained triaxial compression tests on rockfill materials, and the evolution of the specific volume of the rockfill material with the axial strain at different relative densities and different confining pressures.

A series of large-scale triaxial compression tests on Tacheng rockfill material (TRM) showed that the dilatancy and stress-strain behaviors were significantly influenced by density and pressure. The critical state friction angle ofTRM decreased with an increase in the initial confining pressure. In addition, the critical state line of this material in the e-log p9 plane ascended with an increase in the initial void ratio. On the basis of the specific critical state behaviors of TRM, a state-dependent constitutive model was slightly adapted in the triaxial stress space. The model, with only a set of model parameters, could capture the state-dependent behaviors of the dilatancy, stress-strain, and mobilized friction angle of TRM at various densities and pressures. The peak friction angle of TRM was found to be linear, with a coefficient of 0.21, in relation to the maximum dilatancy angle. The coefficient for rockfill materials was smaller than that for sands, indicating that the influence of dilatancy on the strength for sands was more pronounced than that for rockfill materials. [ABSTRACT FROM AUTHOR]

As the bandwidth of SAR/ISAR system continuously increases as well as the synthetic aperture techniques develop, the spatial resolution of radar image is higher and higher. However, the high resolution of radar image does not mean the resolving ability for targets is high. We may have the same experience that the optical image is much easy to understand than radar image even if it has less resolution. A simple and frank explanation is due to the wavelengths of optical waves are much shorter than that of microwaves at which radars usually work, e.g., in the order of 10-5-10-4. Are there any the deep reasons for this? We will illustrate the inherent reasons in this paper from the aspects of imaging geometry and principle, electromagnetic scattering, signal characteristics, and so on. [ABSTRACT FROM AUTHOR]

Original Freeman three-component decomposition was found useful in information extraction from a mix of area: city blocks, forest, ocean and land surfaces, etc.. However, it always suffers from some inconsistencies with real situation such as negative power and scattering mechanism ambiguity. It is probably because of the overestimate of volume scattering power. But intrinsically it is the inconsistency between the assumed models and the PolSAR. The de-orientation method was initially found useful to alleviate this problem to some degree. However, because of the boundedness of deorientation, it is sometimes noneffective. Nonnegative eigenvalue decomposition (NNED) can absolutely solve the negative power problem. But the residual matrix except the volume scattering model is assumed equal to two. So in some sense it is under the volume scattering dominance assumption. Therefore, the decomposition should be separated into two individual parts. In this paper, for the pixels that volume scattering dominates, the NNED will be used. For the pixels that volume scattering doesn't dominate, we will start with the assumed models, and focus on developing a generalized model-based decomposition. Because for model-based scheme, we insist that one should radically start from the models and then a generalized three-component model-based decomposition is proposed, which consist of the surface, double bounce and volume scattering. Among it the generalized scattering mechanism proposed by Cloude is adopted, which provides a more accurate model for surface and dihedral scattering, and the dominant scattering component will be figured out according to the alpha angle parameter to be solved in the generalized model. Through this solution, the dominant scattering mechanism in one pixel will be preserved better. The performance of this approach is demonstrated and evaluated using the airborne AIRSAR and E-SAR data sets. The results show the advantages and improvements especially for alleviating the scattering mechanism ambiguity of oriented buildings from vegetation. [ABSTRACT FROM AUTHOR]

Original three-component polarimetric decomposition always suffers from some deficiencies such as negative power and scattering mechanism ambiguity. In fact, it is probably because of the inconsistency between the assumed models and PolSAR data. In this paper, we intend to solve the scattering mechanism ambiguity in original three-component decomposition, and later we will try to find out some solutions aiming at alleviating the negative power problem. Considering that the nonnegative eigenvalue decomposition (NNED) is only applicative for the pixels that volume scattering dominates (the details will be discussed in Section 1), an improved model-based scheme is proposed, in which the decomposition will be hierarchical. If volume scattering is dominant, a revised NNED is adopted, for which the volume scattering employs the model proposed by Yamaguchi, and if volume scattering is not dominant, a revised four-component decomposition is adopted, for which the volume scattering employs the model proposed by Freeman. The entropy and alpha parameter are employed to identify the dominant scattering mechanism. Through this revision, the decomposition will be more accurate and the dominant scattering mechanism in each pixel will be preserved better. To verify and demonstrate the performance and advantages of the proposed decomposition, the L-band airborne AIRSAR San Francisco data and E-SAR Oberpfaffenhofen polarimetric data are used. Comparison studies are also carried out to show the improvements by the proposed method especially for the oriented urban areas. [ABSTRACT FROM AUTHOR]

In this paper, we give an introduction to some of the research activities on radar for both the hardware development and signal processing algorithms conducted in recent years in the key lab of microwave remote sensing (MIRSL), Chinese Academy of Sciences (CAS). The works focus on the following aspects: (1) interferometric and wide-band radar system development; (2) radar signals and processing; (3) radar image registration; (4) polarimetric radar remote sensing; (5) radar compressive sensing. Some typical results are presented. [ABSTRACT FROM AUTHOR]

Detection performance of the laser altimeter with avalanche photodiode has been analyzed and the studies indicate that the detection threshold applied to the discriminator has the decisive influence on the detection performance. Simulation shows that the primary photoelectron count produced by laser pulse returns and the average gain of APD determine the selection scope of the threshold, and also a method to select the threshold has been presented. [ABSTRACT FROM AUTHOR]

The system design, principles, technical characteristics, and preliminary simulation results of the Chino Spaceborne Scanning Scatterometer (China Scanscat or CNSCAT) are introduced. This system uses two parabolic antennas, which do conical scanning around the axis normal to the observation surface. These two antennas (one for horizontal polarization and the other for vertical polarization) are separated by 90-degrees in azimuth but have the same incident angle. The CNSCAT is different from the recently launched NASA Quickscat, although both of them use a pencil-beam antenna. In the design of CNSCAT, a near-field absolute calibration of the antenna is involved. The simulation shows that the CNSCAT has the capability to retrieve the wind field and can meet the design goal. [ABSTRACT FROM AUTHOR]