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1. chinaXiv:201711.00133 [pdf]

Solvent Synthesis, Growth Mechanism and Photocatalytic Properties of AgInS2 Nanoplate and Nanoparticle

WANG Yue; SHI Yong-Fang; LI Xiao-Bo; LI Dong-Wei; ZHANG Tao; HE Yu-Cen
Subjects: Chemistry >> Physical Chemistry

Orthorhombic AgInS2 nanoplate and nanoparticle were synthesized using pyridine and 1-dodecanethiol as the solvent. The obtained products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), field-emission transmission electron microscope (FETEM), and the possible growth mechanism of AgInS2 was also proposed by the exploration of reaction temperature and time. Meanwhile, the bandgap of AgInS2 was calculated by the UV-Vis diffuse reflectance spectrum, and the photocatalytic activity was also investigated. Those experimental results indicate that the reaction temperature, reaction time and solvent have an influence on phase and morphology of AgInS2, and both AgInS2 nanoplate and nanoparticle have some ability on photocatalytic degradation of organic dyes under UV-Vis light irradiation.

submitted time 2017-11-05 From cooperative journals:《结构化学》 Hits1936Downloads1003 Comment 0

2. chinaXiv:201703.00558 [pdf]

Study of defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals

LI Dong-Xiang; QIN Xiu-Bo; ZHENG Li-Rong; LI Yu-Xiao; CAO Xing-Zhong; LI Zhuo-Xin; YANG Jing; WANG Bao-Yi
Subjects: Physics >> Condensed Matter: Structural, Mechanical and Thermal Properties

Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when magnetic field is applied parallel to the sample plane. By combining X-ray absorption near edge structure spectrum and positron annihilation lifetime spectroscopy, Ti3+-VO defect complexes (or clusters) have been identified in annealed crystals at high vacuum. We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism. Besides, excess oxygen ions in TiO2 lattice could induce a number of Ti vacancies which increase magnetic moments obviously.

submitted time 2017-03-26 Hits1216Downloads692 Comment 0

3. chinaXiv:201703.00305 [pdf]

Model-based decomposition with adaptive selection of unitary transformations

Zhu, Feiya; Zhang, Yunhua; Li, Dong; Gu, Xiang
Subjects: Geosciences >> Space Physics

In this paper a three component model-based decomposition with adaptive selection of unitary transformations for polarimetric synthetic aperture radar (POLSAR) data processing is proposed. Singh et al implemented two unitary transformations on the coherency matrix to minimize the power of cross-polarization, and as a result the T23element of the coherency matrix becomes zero. Another two unitary transformations are proposed by us to carry out on the coherency matrix also to minimize the power of crosspolarization, and the T13element of the coherency matrix becomes zero. Here, we first implement Singh's two unitary transformations and the proposed two unitary transformations on the coherency matrix separately. Then we select the one which leads to the smaller T33. At last, we carry out the three component model-based decomposition proposed by Freeman and Durden based on the obtained coherency matrix. The smaller T33is obtained, the better the over-estimation of volume scattering in model-based decomposition can be suppressed. The RADARSAT-2 POLSAR data of San Francisco area is used to validate the improvement of the proposed method over the three component decomposition only with Singh's two unitary transformations.

submitted time 2017-03-10 Hits18342Downloads1493 Comment 0

4. chinaXiv:201703.00299 [pdf]

A novel deorientation method for PolSAR data processing

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

In PolSAR data processing, deorientation operation is often necessary. The existing deorientation method uniformly deorients all the sub-scatterers of a resolution cell with one orientation angle. For high entropy situation, the sub-scatterers have diverse OAs, and the effect of the existing method is unsatisfactory. A novel deorientation method is proposed to well treat the high entropy situation. Cloude's eigen-decomposition to the coherency matrix is first carried out. The three eigenvectors are then separately deoriented with their own orientation angles. Experiments demonstrate that the proposed method is suitable for extraction of urban regions, especially for extraction of oriented urban regions. ?VDE VERLAG GMBH ?Berlin ?Offenbach.

submitted time 2017-03-10 Hits3383Downloads1151 Comment 0

5. chinaXiv:201703.00297 [pdf]

A novel polarimetric interferometric SAR coherence parameter and its application in buildings detection

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

Man-made buildings detection is important in land use supervision and land control applications. Generally, polarimetric synthetic aperture radar (PolSAR) data are processed to detect buildings well. But for some buildings which are not aligned with the radar track, these buildings are usually incorrectly recognized as forest, because the oriented buildings produce additional cross-polarization. Polarimetric interferometric SAR (PolINSAR) acquires two measurements with a spatial baseline or a temporal baseline. For the PolINSAR with a temporal baseline i.e., the repeat pass PolInSAR, the two polarimetric measurements are sensitive to targets' temporal variations during the time. The buildings, regardless of the orientations, have high coherence, while some natural targets have low coherence. A novel parameter is proposed here, which represents the mean PolINSAR coherence and can be utilized to distinguish between buildings and some natural targets. The parameter is based on the coherence optimization theory of Cloude and Papathanassiou, and is the mean of the three optimal coherences with three pseudo-probabilities. Based on this new parameter and the SPAN, a method to detect buildings is further proposed. The excellent performance of the proposed method on buildings extraction is demonstrated by processing German Aerospace Center (DLR) L-band E-SAR repeat pass PolINSAR data of Oberpfaffenhofen area.

submitted time 2017-03-10 Hits3637Downloads1299 Comment 0

6. chinaXiv:201703.00292 [pdf]

A novel interpretation of the PolSAR coherency matrix data

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

Cloude-Pottier incoherent target decomposition (ICTD) and Touzi ICTD has been widely applied as a popular approach to interpret the scattering characteristics of a target in polarimetric synthetic aperture radar (PolSAR) data processing. However, they have a common drawback, i.e. proliferation of parameters (PoP) is unavoidable. Paladini et al. solved this problem by developing an orientation-invariant ICTD based on the coherency matrix under circular polarization basis. As an alternative to Paladini decomposition, we proposed a novel ICTD based on the frequently used coherency matrix under linear polarization basis. The proposed method can also avoid the problem of PoP, and avoid the ambiguity of alpha angle of Paladini decomposition as well. Real PolSAR data is processed to validate the proposed decomposition.

submitted time 2017-03-10 Hits2789Downloads1188 Comment 0

7. chinaXiv:201703.00248 [pdf]

An Extension of a Complete Model-Based Decomposition of Polarimetric SAR Data

Zhu, Feiya; Zhang, Yunhua; Li, Dong
Subjects: Geosciences >> Space Physics

The model-based decomposition that originated from Freeman-Durden three-component decomposition (FDD) has been widely applied in polarimetric synthetic aperture radar (PolSAR) data processing for its clear physical interpretation and easy implementation. Numerous improvements have been proposed to settle the twomain drawbacks of FDD, i.e., the incomplete utilization of the polarimetric information in the coherency matrix and the negative scattering power problem. Recently, Cui et al. proposed a complete model-based three-component decomposition which successfully settled the two aforementioned drawbacks. However, the three scattering components' powers are not totally derived using scattering models, and the remaining coherency matrix (RCM) obtained by subtracting the volume scattering component from the coherency matrix is not consistent with the models of surface and double-bounce scattering components. As an extension of Cui's method, this letter is dedicated to develop a novel method to discriminate the surface and double-bounce scattering components both using scattering models. With the orientation angle (OA) variation and helix angle (HA) variation compensated for the RCM, the RCM is automatically consistent with the models of surface and double-scattering components. The OA variation and HA variation compensation for the RCMis done by unitary transformations of the eigenvectors of the RCM. The powers of surface and double-bounce scattering components are positive. The effectiveness of the proposedmethod is demonstrated by processing the real PolSAR data.

submitted time 2017-03-10 Hits2076Downloads1158 Comment 0

8. chinaXiv:201701.00028 [pdf]

A fast offset estimation approach for InSAR image subpixel registration

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A fast offset estimation approach for interferometric synthetic aperture radar (InSAR) image pair subpixel registration is proposed for cases of relatively gentle topography and/or short baseline. A coarse-to-fine registration strategy is taken. The pixel-level offset is estimated in the coarse registration step by a fast feature-based estimation, which uses the speeded up robust feature operator and fast least trimmed squares (Fast-LTS) estimator to accelerate the feature extraction and parameter estimation. A fine registration is performed subsequently. The conventional normalized cross-correlation algorithm (NCCA) searches for the optimal subpixel offset by oversampling either the coarse cross correlation or the InSAR image patch pair. The offset estimation accuracy is restricted by the oversampling rate, and the computational burden is heavy when high accuracy is demanded. In this letter, we transform the oversampling and correlation searching process of NCCA into a nonlinear optimization problem, which takes the maximization of the coherent cross correlation as the objective function; by solving it, the subpixel offset can be fast and exactly obtained without any image oversampling. The final registration parameters are inverted by Fast-LTS fitting of a series of subpixel tie point correspondences which can be constructed after applying the approach to several image patch pairs. RadarSat-2 data are used to test the approach, and the results show that it performs very well not only on the speed but also on the accuracy. ?2006 IEEE.

submitted time 2017-01-04 Hits2504Downloads1344 Comment 0

9. chinaXiv:201701.00027 [pdf]

Fast least trimmed squares (Fast-LTS); Image registration; Parameter estimation; Random sample consensus (RANSAC); Weak affine transformation

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A novel image registration scheme is devised in view of the weak affine transformation, which is a kind of similarity transformation with anisotropic scales or affine transformation without shearing. Two robust algorithms are proposed to retrieve the registration parameters from the error-prone initial correspondences based on the fast least trimmed squares (Fast-LTS) and the random sample consensus (RANSAC). In terms of several criteria, the algorithms are evaluated on three carefully selected datasets from different sensors and the experimental results demonstrate that the proposed scheme and algorithms perform robustly and accurately. Our findings also indicate that the Fast-LTS-based algorithm is more stable and appropriate for image registration than the RANSAC-based algorithm although the speed is slower. ?2012 Elsevier B.V. All rights reserved.

submitted time 2017-01-04 Hits2190Downloads1071 Comment 0

10. chinaXiv:201701.00026 [pdf]

A rigorous SAR epipolar geometry modeling and application to 3D target reconstruction

Li, Dong; Zhang, Yunhua
Subjects: Geosciences >> Space Physics

A rigorous epipolar geometry modeling for synthetic aperture radar (SAR) is developed from a concise imaging model proposed in the paper. The imaging model and epipolar model not only geometrically unify the SAR imaging and the optical camera imaging, but also motivate a 3D target reconstruction which is theoretically validated to be consistent with the radargrammetry and experimentally demonstrated to be accurate. ?2008-2012 IEEE.

submitted time 2017-01-04 Hits2278Downloads1216 Comment 0

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