126 results on '"Guang Cai"'
Search Results
2. A Multi-Pulse Cross Ambiguity Function for the Wideband TDOA and FDOA to Locate an Emitter Passively.
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Wang, Yuqi, Sun, Guang-Cai, Wang, Yong, Yang, Jun, Zhang, Zijing, and Xing, Mengdao
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HARDWARE-in-the-loop simulation , *AMBIGUITY , *DATA transmission systems , *PHOTOPLETHYSMOGRAPHY - Abstract
The time difference of arrival (TDOA) and frequency difference of arrival (FDOA) between two receivers are widely used to locate an emitter. Algorithms based on cross ambiguity functions can simultaneously estimate the TDOA and FDOA accurately. However, the algorithms, including the joint processing of received data, require transferring a large volume of data to a central computing unit. It can be a heavy load for the data link, especially for a wideband signal obtained at a high sampling rate. Thus, we proposed a multi-pulse cross ambiguity function (MPCAF) to compress the data before transmitting and then estimate the TDOA and FDOA with the compressed data. The MPCAF consists of two components. First, the raw data are compressed with a proposed two-dimensional compression function. Two methods to construct a reference pulse used in the two-dimensional compression function are considered: a raw data-based method constructs the pulse directly from the received signal, and a signal parameter-based method constructs it through the parameters of the received signal. Second, a wideband cross-correlation function is studied to refine the TDOA and FDOA estimates with the compressed data. The simulation and Cramer–Rao lower bound (CRLB) analyses show that the proposed method dramatically reduces the data transmission load but estimate the TDOA and FDOA well. The hardware-in-the-loop simulation confirms the method's effectiveness. [ABSTRACT FROM AUTHOR]
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- 2022
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3. A High-Resolution and High-Precision Passive Positioning System Based on Synthetic Aperture Technique.
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Wang, Yuqi, Sun, Guang-Cai, Wang, Yong, Zhang, Zijing, Xing, Mengdao, and Yang, Xiaoniu
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COST functions , *SYNTHETIC apertures , *MAXIMUM likelihood statistics , *SIGNAL-to-noise ratio - Abstract
The nonlinear variation of viewing angles over a long duration causes a nonlinear initial phase of the received pulse in a passive positioning system with a single moving receiver. Typical positioning systems ignore the phase and perform incoherent accumulation of the long-time data, thus resulting in a decrease in positioning accuracy, especially at a low signal-to-noise ratio (SNR). A novel passive positioning system with a synthetic aperture technique, named synthetic aperture positioning (SAP) system, is proposed to resolve the issue. First, a new 2-D continuous sampling working model is proposed. Then, the SAP system and a cost function are given to analyze the positioning performance. Third, a positioning algorithm based on the maximum likelihood estimation (MLE) is studied to handle the cost function and position the emitter. Simulation and experimental results verify the validity and effectiveness of the proposed SAP system. [ABSTRACT FROM AUTHOR]
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- 2022
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4. Focusing Challenges of Ships With Oscillatory Motions and Long Coherent Processing Interval.
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Liu, Wenkang, Sun, Guang-Cai, Xia, Xiang-Gen, Fu, Jixiang, Xing, Mengdao, and Bao, Zheng
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SINGLE-degree-of-freedom systems , *RELATIVE motion , *SHIPS , *CURVED surfaces , *SIGNAL-to-noise ratio - Abstract
Ship motions during long coherent processing interval (CPI) have six degrees of freedom, and the oscillatory motions are roughly periodical. The traditional ship imaging methods usually use a short time interval to form an image, while the image quality may suffer from low resolution, poor signal-to-noise ratio (SNR), and scatter scintillation. Using a longer CPI to generate an image may improve the quality but, however, largely increase the focusing difficulty. In this article, we investigate the focusing challenges of oscillatory ships with long CPI. Through analyzing the relative motion between the radar and the ship, the properties of wavenumber domain support (WDS) and point spreading function (PSF) of oscillatory ship imaging are studied. It is illustrated that the WDS is a 3-D sparse curved surface generated by the complex relative motion, with a time-variant energy density, nonparallel spectrum boundaries, and a complex structure. The PSF of an oscillatory ship may have a 3-D resolution but also multiple high-level sidelobes. The relationship between the WDS and the nonideal PSF is illustrated with the projection slice theorem (PST). Moreover, it is discussed that the scatterers distributed on a 3-D ship cannot be focused uniformly on a 2-D imaging plane (IP) due to the variation of the slant-range plane (SRP). The projection relationships of the resolutions and focusing positions between the SRP and the IP are also derived. Simulation results are presented to validate the analyses throughout this article. [ABSTRACT FROM AUTHOR]
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- 2021
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5. Ground Cartesian Back-Projection Algorithm for High Squint Diving TOPS SAR Imaging.
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Chen, Xiaoxiang, Sun, Guang-Cai, Xing, Mengdao, Li, Boyu, Yang, Jun, and Bao, Zheng
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SYNTHETIC aperture radar , *STRABISMUS , *ALGORITHMS , *DIVING , *FREQUENCY-domain analysis , *INTERPOLATION algorithms - Abstract
This article presents a fast back-projection (BP) algorithm based on subaperture (SA) image coherent combination in a downsampled Cartesian coordinate grid for high squint diving terrain observation by progressive scans (HSD-TOPS) synthetic aperture radar (SAR) ground plane imaging. A two-step spectrum compression (SC) method is proposed to coherently combine the aliasing SA images by exploiting the relationship between the wavenumber and the image frequency. The first-step SC is introduced to align the spectrum support region centers. The second-step SC effectively corrects the space-variant spectrum inclination. The proposed algorithm does not need interpolation in the process of image combination, which ensures the accuracy and the efficiency of the algorithm. Furthermore, the SC method is well-modified to suppress the sidelobes of the focused image. Simulation and measured data processing verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
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- 2021
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6. Dependence of dislocation creation on tensile orientation in face-centered-cubic ductile metals under high strain rate loading.
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Wei-Wei Pang, Guang-Cai Zhang, Xian-Geng Zhao, and Ping Zhang
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DISLOCATION structure , *TENSILE strength , *DUCTILE fractures , *STRAINS & stresses (Mechanics) , *BURGERS' equation , *COMPUTER simulation - Abstract
We investigate through molecular dynamic simulations the dependence of dislocation creation on tensile orientation in face-centered-cubic ductile metals under high strain rate loading. It is found that while dislocations generally originate from the double-layer defect clusters consisting of flatted octahedral structures (FOSs), the formation mechanism and the types of FOSs, as well as the types of nucleated dislocations, depend on the applied loading directions. For the loading along the [̅110], [̅1̅12], and [111] crystal directions, it is shown that a pair of the nearest-neighboring atoms move away to form the elongated FOS. However, for the loading along the [100] crystal direction, a pair of the next-nearest-neighboring atoms move close to form the compressed FOS. According to the uniform deformation amount of the spacing vector for a pair of neighboring atoms and the stress component along the Burgers vector on the stacking fault plane, we analytically predict the activated types of FOSs and dislocations for different loading directions, which turn to be remarkably consistent with our numerical simulations. [ABSTRACT FROM AUTHOR]
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- 2015
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7. 2-D Beam Steering Method for Squinted High-Orbit SAR Imaging.
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Liu, Wenkang, Sun, Guang-Cai, Xing, Mengdao, Pascazio, Vito, Chen, Quan, and Bao, Zheng
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BEAM steering , *SYNTHETIC aperture radar , *ANTENNA design , *AZIMUTH - Abstract
Since path curvature becomes severer for higher orbit synthetic aperture radar (SAR), the stripmap mode may not provide a reliable azimuth resolution under different look angles or at different positions. Beam steering is especially valuable herein for adjusting the azimuth resolution under different observation conditions by designing the antenna steering rate. Moreover, considering that the large range migration and center range variation in the squint mode may increase the echo length and reduce the achievable scene width, we proposed a novel 2-D beam steering (TDBS) method, which promises not only a required azimuth resolution but also a wide swath (or shortened echo length) at squint when cooperated with the variable interpulse time (VIPT) technique. The simulation results obtained under different look directions are shown to validate the effectiveness of the proposed beam controlling method. [ABSTRACT FROM AUTHOR]
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- 2021
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8. Dexmedetomidine Attenuates Lung Injury in Toxic Shock Rats by Inhibiting Inflammation and Autophagy.
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Li, Zhi-Bing, Li, Guang-Cai, and Qin, Jing
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DEXMEDETOMIDINE , *COMMERCIAL products , *LUNG injuries , *SPRAGUE Dawley rats , *AUTOPHAGY , *TRANSMISSION electron microscopy - Abstract
To explore the mechanisms whereby dexmedetomidine reversed lung injury in rats with toxic shock via inhibiting inflammation and autophagy. Thirty-six specific pathogen-free male Sprague Dawley rats with were screened and randomly divided into three groups. Toxic shock was induced by intestinal leakage. The control group received no cecal ligation and the treatment group received dexmedetomidine hydrochloride. Lung tissue morphology was studied by hematoxylin-eosin staining. The expression levels of inflammatory cytokines including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR). The expression levels of beclin l and LC3 were measured, and the expression levels of apoptosis gene Bax and Bcl-2 were determined. The autophagosomes in lung cells were observed by transmission electron microscopy. Extracellular signal-regulated kinase (ERK) 1/2 expression was determined by Western blotting assays. The results showed that the W/D, total protein and myeloperoxidase (MPO) index in the toxic shock group were 5.45 ± 0.35, 3.21 ± 0.47 and 4.53 ± 0.36, respectively. The W/D (4.02 ± 0.67), total protein (2.01 ± 0.35) and MPO index (2.31 ± 0.59) were significantly lower in the dexmedetomidine group (p <0.05). Similarly, compared with the toxic shock group, the expression of p-ERK1/2 protein in the dexmedetomidine treatment group was significantly decreased (p <0.05). The expression levels of autophagy proteins beclin1 and LC3 in the dexmedetomidine treatment group were not significantly different from those of the control group (p >0.05). Transmission electron microscopy showed that the number of autophagic bodies in lung cells decreased. After induction with dexmedetomidine hydrochloride, the proapoptotic gene Bax was significantly downregulated in the cells. Bax expression levels in each group were 0.36 ± 0.12, 0.67 ± 0.06, and 0.32 ± 0.12, respectively. Compared with the control group, Bax expression in lung tissue significantly increased in the toxic shock group (p <0.05). Dexmedetomidine attenuates lung injury in toxic shock rats by inhibiting inflammation and autophagy. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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9. Focusing of MEO SAR Data Based on Principle of Optimal Imaging Coordinate System.
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Liu, Wenkang, Sun, Guang-Cai, Xing, Mengdao, Li, Hang, and Bao, Zheng
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IMAGING systems , *COORDINATES , *SYNTHETIC apertures , *SPATIAL variation , *ALGORITHMS , *SYNTHETIC aperture radar - Abstract
The curved trajectory and long synthetic aperture time of medium-Earth-orbit (MEO) synthetic aperture radar (SAR) lead to a 2-D spatial variation in the signals. Traditional methods treat the range and azimuth variations separately and usually suffer from high computational complexities. In this article, we investigate the Doppler rate distribution across a large scene and exploit an optimal imaging coordinate system, in which the MEO SAR signals satisfy the azimuth-shift-invariant property. Thus, the additional processing of the azimuth spatial variation in MEO SAR imaging algorithms can be avoided, and the efficiency of the image formation processor can be obviously improved. The Doppler linearization is used to address the higher-order Doppler parameters to achieve more precise focusing, and at the same time, addresses the azimuth time shift caused by the changes of signal distribution. Finally, processing results of simulated stripmap-mode data with the 2-m resolution are presented to validate the proposed algorithm. [ABSTRACT FROM AUTHOR]
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- 2020
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10. Exercise-Induced Cognitive Improvement Is Associated with Sodium Channel-Mediated Excitability in APP/PS1 Mice.
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Tan, Ya-Xin, Liu, Guang-Cai, Chen, Hong-Lan, Lu, Min-Nan, Chen, Bo, Hu, Tao, Zhang, Li, Mao, Rui, Li, Shan, Mei, Rong, Wang, Xu-Yang, and Xiyang, Yan-Bin
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TREADMILL exercise , *AMYLOID beta-protein precursor , *TRANSGENIC mice , *COGNITION disorders , *EXERCISE , *THIRST , *IRRITABILITY (Psychology) - Abstract
Elevated brain activation, or hyperexcitability, induces cognitive impairment and confers an increased risk of Alzheimer's disease (AD). Blocking the overexcitation of the neural network may be a promising new strategy to prevent, halt, and even reverse this condition. Physical exercise has been shown to be an effective cognitive enhancer that reduces the risk of AD in elderly individuals, but the underlying mechanisms are far from being fully understood. We explored whether long-term treadmill exercise attenuates amyloid precursor protein (APP)/presenilin-1 (PS1) mutation-induced aberrant network activity and thus improves cognition by altering the numbers and/or distribution of voltage-gated sodium channels (Nav) in transgenic mice. APP/PS1 mice aged 2, 3.5, 5, 6.5, 8, and 9 months underwent treadmill exercise with different durations or at different stages of AD. The alterations in memory, electroencephalogram (EEG) recordings, and expression levels and distributions of Nav functional members (Nav1.1α, Nav1.2, Nav1.6, and Navβ2) were evaluated. The results revealed that treadmill exercise with 12- and 24-week durations 1) induced significant improvement in novel object recognition (NOR) memory and Morris water maze (MWM) spatial memory; 2) partially reduced abnormal spike activity; and 3) redressed the disturbed cellular distribution of Nav1.1α, aberrant Navβ2 cleavage augmentation, and Nav1.6 upregulation. Additionally, APP/PS1 mice in the 24-week exercise group showed better performance in the NOR task and a large decrease in Nav1.6 expression, which was close to the wild-type level. This study suggests that exercise improves cognition and neural activity by altering the numbers and distribution of hippocampal Nav in APP/PS1 mice. Long-term treadmill exercise, for about 24 weeks, starting in the preclinical stage, is a promising therapeutic strategy for preventing AD and halting its progress. [ABSTRACT FROM AUTHOR]
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- 2020
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11. Upregulated microRNA‐15b alleviates ovarian cancer through inhitbition of the PI3K/Akt pathway by targeting LPAR3.
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Li, Guang‐Cai, Qin, Xu‐Ling, Song, Huai‐Hua, Li, Ying‐Ni, Qiu, Yu‐Yan, Cui, Shi‐Chang, Wang, Yong‐Sheng, Wang, Hui, and Gong, Jun‐Ling
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OVARIAN cancer , *CANCER cell migration , *CANCER cell proliferation , *CELL migration inhibition , *LYSOPHOSPHOLIPIDS , *CANCER cells - Abstract
Ovarian cancer characterizes as the fourth leading consequence of death associated with cancer for women. Accumulating evidence underscores the vital roles of microRNAs (miRNAs) in preventing ovarian cancer development. Besides, induction of the phosphatidylinositol‐3 kinase/serine/threonine kinase (PI3K/Akt) pathway associated with the ovarian cancer cell migration and invasion. The study aims to examine the effects of miR‐15b on the proliferation, apoptosis, and senescence of human ovarian cancer cells by binding to lysophosphatidic acid receptor 3 (LPAR3) with the involvement of the PI3K/Akt pathway. The positive expression of LPAR3 protein was detected by immunohistochemistry. Then the interaction between miR‐15b and LPAR3 was examined. The possible role of miR‐15b in ovarian cancer was explored using gain‐ and loss‐of‐function experiments. Subsequently, the functions of miR‐15b on PI3K/Akt pathway, proliferation, migration, invasion, senescence and apoptosis of ovarian cancer cells were assessed. Furthermore, in vivo tumorigenicity assay in nude mice was performed. LPAR3 was overexpressed, whereas miR‐15b was poorly expressed in ovarian cancer tissues. LPAR3 is a direct target of miR‐15b. Restored miR‐15b promoted Bax expression, apoptosis, and senescence, inhibited expression of LPAR3 and Bcl‐2, the extent of PI3K and Akt phosphorylation, as well as ovarian cancer cell proliferation, migration, and invasion. Further, tumor growth was observed to be prevented by miR‐15b overexpression. Collectively, our study demonstrates that miR‐15b represses the proliferation and drives the senescence and apoptosis of ovarian cancer cells through the suppression of LPAR3 and the PI3K/Akt pathway, highlighting an antitumorigenic role of miR‐15b. [ABSTRACT FROM AUTHOR]
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- 2019
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12. Highly Squinted MEO SAR Focusing Based on Extended Omega-K Algorithm and Modified Joint Time and Doppler Resampling.
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Liu, Wenkang, Sun, Guang-Cai, Xia, Xiang-Gen, You, Dong, Xing, Mengdao, and Bao, Zheng
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AZIMUTH , *SYNTHETIC aperture radar , *COMPUTATIONAL geometry , *SPATIAL variation , *ALGORITHMS , *RECORDS management - Abstract
A squinted observation geometry along with long integration time significantly aggravates the range walk and spatial variation of a medium-earth-orbit (MEO) synthetic aperture radar (SAR) signal. Variable pulse repeating frequency (PRF) is recommended to avoid the blockage in echo recording and save storage space. The existing wavenumber algorithms cannot handle the nonlinear and range–azimuth-coupled spatial variation (RACSP) over a large scene. In this paper, we propose a modified Stolt mapping method along with a modified joint time and Doppler resampling (JTDR) for highly squinted MEO SAR data processing. An azimuth timescale transformation is used to deal with the nonlinear spatial variation of the azimuth frequency-modulation (FM) rate. An extended Omega-K is used to linearize the range frequency and achieve range cell migration correction (RCMC). To address the RACSP, the Doppler is linearized in the range-Doppler domain using a range-dependent Doppler scale transformation. The computational complexity and geometry distortion correction (GDC) are also discussed. Simulation results are shown to verify the effectiveness of the developed focusing approaches. [ABSTRACT FROM AUTHOR]
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- 2019
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13. High-Speed Maneuvering Platforms Squint Beam-Steering SAR Imaging Without Subaperture.
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Bie, Bowen, Sun, Guang-Cai, Xia, Xiang-Gen, Xing, Mengdao, Guo, Liang, and Bao, Zheng
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SYNTHETIC apertures , *BEAM steering , *STRABISMUS , *SYNTHETIC aperture radar , *AZIMUTH , *CELL migration - Abstract
This paper investigates the imaging problems in squint beam-steering synthetic aperture radar (SBS-SAR) mounted on high-speed platforms with constant acceleration. The cross-range-dependent range cell migration (RCM) is compensated by keystone transform (KT) and time domain RCM correction (RCMC). By derotation and phase compensation, the KT of Doppler folded signal is achieved without zero-padding. For azimuth processing, the signal is reconstructed by the nonlinear phase and range-dependent derotation. Then, the space-variant (SV) Doppler chirp rate is corrected by time domain azimuth nonlinear chirp scaling (ANCS). After frequency domain matched filtering, the full aperture signal is focused in the 2-D time domain. The algorithm is validated by simulated SAR data, including the evaluation of RCMC with KT, geometric correction, and the focusing performance. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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14. Discovery of 16-demethylrifamycins by Removing Predominant Polyketide Biosynthetic Pathway in Micromonospora sp. TP-A0468.
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Qiang Zhou, Guang-Cai Luo, Huizhan Zhang, and Gong-Li Tang
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POLYKETIDES , *MICROMONOSPORA , *NATURAL products , *GENE clusters , *MICROORGANISMS , *MYCOBACTERIUM tuberculosis - Abstract
A number of strategies have been developed to mine novel natural products based on biosynthetic gene clusters and there has been dozens of successful cases facilitated by the development of genomic sequencing. During our study on biosynthesis of the antitumor polyketide kosinostatin (KST), we found that the genome of Micromonospora sp. TP-A0468, the producer of KST, contains other potential polyketide gene clusters, with no encoded products detected. Deletion of kst cluster led to abolishment of KST and the enrichment of several new compounds which were isolated and characterized as 16-demethylrifamycins (3-6). Transcriptional analysis demonstrated that the expression of the essential genes related to the biosynthesis of 3-6 was in comparable level in wild type and kst cluster deletion strain. This indicates that the accumulation of these compounds was due to the redirection of metabolic flux rather than transcriptional activation. Genetic disruption, chemical complementation and bioinformatic analysis revealed that the production of 3-6 was accomplished by crosstalk between two distantly placed polyketide gene clusters pks3 and M-rif. This finding not only enriches the analogue pool and biosynthetic diversity of rifamycins, but also provides an auxiliary strategy for natural product discovery through genome mining in polyketide-producing microorganisms. Importance Natural products are essential in the development of novel clinically-used drugs. Discovering new natural products and modifying known compounds are still the two main ways to generate new 37 candidates. Here, we have discovered several rifamycins with varied skeleton by redirecting the metabolic flux from the predominant polyketide biosynthetic pathway to the rifamycin pathway in the marine actinomycetes species Micromonospora sp. TP-A0468. Rifamycins are indispensable chemotherapeutics in the treatment of various diseases such as tuberculosis, leprosy and AIDS-related mycobacterial infections. This work exemplifies a useful method for the discovery of cryptic natural products in genome-sequenced microbes. Moreover, the 16-demethylrifamycins and their genetically manipulable producer provides a new opportunity in the construction of novel rifamycin derivates to aid in the defense against the ever-growing drug-resistance of Mycobacterium tuberculosis. [ABSTRACT FROM AUTHOR]
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- 2019
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15. MicroRNA-374b inhibits cervical cancer cell proliferation and induces apoptosis through the p38/ERK signaling pathway by binding to JAM-2.
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Li, Guang-Cai, Cao, Xiao-Yun, Li, Ying-Ni, Qiu, Yu- Yan, Li, Ying-Na, Liu, Xing-Jie, and Sun, Xiang-Xiu
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CERVICAL cancer treatment , *EXTRACELLULAR signal-regulated kinases , *MICRORNA , *APOPTOSIS , *CELL junctions , *CANCER cell proliferation , *PROTEIN binding - Abstract
Cervical cancer (CC) remains a highly prevalent cancer and mortality globally among women globally. The aim of the present study was to assess the ability of miR-374b to regulate CC cells through JAM-2, whilst exploring whether the underlying mechanism and its relation to the p38/ERK signaling pathway. During the study, microRNA-374b (miR-374b) was observed to have been expressed at a low level among CC tissues. Hence, a series of miR-374b mimics, miR-374b inhibitors, siRNA against JAM-2, SB202190 (an inhibitor for p38), and PD98059 (an inhibitor for ERK) were introduced to treat CC Siha cells and normal cervical Ect1/E6E7 cells. MTT, flow cytometry, scratch test, and transwell assays were applied to determine cell viability, apoptosis, migration, and invasion. The inhibitory role of the p38/ERK signaling pathway was observed in the CC cells treated with miR-374b mimics or siRNA against JAM-2. miR-374b mimic exposure was found to reduce cell viability, migration, and invasion, but induce apoptosis. MiR-374b inhibitor exposure was observed to have induced effects on the CC cells in a contrary manner to those induced by that of the miR-374b mimics. The key findings of the study demonstrated that miR-374b significantly inhibits cell proliferation, migration, and invasion through the blockade of the p38/ERK signaling pathway activation, as well as negatively binding to JAM-2, highlighting its potential as a therapeutic target for CC. [ABSTRACT FROM AUTHOR]
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- 2018
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16. A Modified CSA Based on Joint Time-Doppler Resampling for MEO SAR Stripmap Mode.
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Liu, Wenkang, Sun, Guang-Cai, Xia, Xiang-Gen, Chen, Jianlai, Guo, Liang, and Xing, Mengdao
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SYNTHETIC aperture radar , *IMAGE processing , *DOPPLER effect , *SPACE vehicles , *RADIO frequency modulation - Abstract
Image formation of large scenes is still challenging in medium-earth-orbit (MEO) synthetic aperture radar (SAR) due to the existence of severe 2-D space variance. In this paper, the properties of space variance are analyzed in detail, and then a variable-coefficient fourth-order range model is adopted to model the space-variant range history of every target in a large scene accurately. A method integrating a modified chirp scaling algorithm with joint time-Doppler resampling is proposed to address the range-variant range cell migration, as well as the azimuth-variant frequency-modulation rate and higher order Doppler parameters. The computational burden and alternative implementation approaches are also discussed. Finally, processing of simulated data for MEO SAR with 2-m resolution is presented to validate the proposed algorithm. [ABSTRACT FROM AUTHOR]
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- 2018
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17. An Analytical Resolution Evaluation Approach for Bistatic GEOSAR Based on Local Feature of Ambiguity Function.
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Chen, Jianlai, Sun, Guang-Cai, Wang, Yong, Guo, Liang, Xing, Mengdao, and Gao, Yuexin
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SYNTHETIC aperture radar , *GEOSTATIONARY satellites , *THREE-dimensional imaging , *TRAJECTORIES (Mechanics) , *BISTATIC radar - Abstract
Due to the very high orbit, the apparent features of geosynchronous synthetic aperture radar (GEOSAR) are the curved trajectory and long integration time, which can lead to severe coupling between the azimuth and the range directions and, therefore, complicates the resolution evaluation. The traditional analytical approach based on the 2-D division may produce large resolution error, and the numerical approach may suffer from huge computation burden. Therefore, an analytical resolution evaluation approach for GEOSAR based on the local feature of the ambiguity function is studied in this paper. The proposed approach is validated with simulation data to be of high efficiency and accuracy. In addition, the proposed approach is also demonstrated to be capable of evaluating the resolution for other complex platforms, and of evaluating the 3-D resolution of a SAR system. [ABSTRACT FROM AUTHOR]
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- 2018
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18. A two-dimensional phase coding for range ambiguity suppression.
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Li, Jian, Sun, Guang-Cai, Xia, Xiang-Gen, Guo, Liang, Jing, Guo-Bin, Xing, Meng-Dao, and Bao, Zheng
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PHASE coding , *SIGNAL processing , *AZIMUTH , *DOPPLER effect , *ENCODING - Abstract
Abstract Based on a two-dimensional phase coding, a novel range ambiguity suppression technique is proposed in this paper. By transmitting two-dimensional phase coded signals, the two-dimensional spectrum of the range ambiguous signals will be shifted along both range and azimuth directions compared with that of desired signals. Then, part of the two-dimensional spectrum of the range ambiguous signals will be located outside the two-dimensional spectral support, which is known in priori, of the desired signals. Considering the range frequency and Doppler oversamplings, a filter corresponding to the two-dimensional spectral support of the desired signals is applied, which suppresses the range ambiguity. Simulation results of both point targets and distributed targets validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
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- 2018
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19. Full-Aperture Focusing of Very High Resolution Spaceborne-Squinted Sliding Spotlight SAR Data.
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Sun, Guang-Cai, Wu, Yuan, Yang, Jun, Xing, Mengdao, and Bao, Zheng
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HIGH resolution imaging , *SYNTHETIC aperture radar , *SPACE-based radar , *COMPUTER algorithms , *AZIMUTH - Abstract
In very high resolution spaceborne-squinted sliding spotlight synthetic aperture radar, the traditional imaging algorithms based on the equivalent squint range model (ESRM) cannot be applied, because the ESRM model is inaccurate in this case. For this problem, this paper proposes a squint equivalent acceleration range model to precisely take into account the spaceborne-squinted curved orbit. Then a full-aperture squint-imaging algorithm is proposed based on this new range model, which can handle the azimuth variation of the equivalent velocity and the range variation of the 2-D frequency spectrum. The results of the simulation validate the effectiveness of new range model and imaging algorithm. [ABSTRACT FROM PUBLISHER]
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- 2017
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20. Temporal dynamics of nutrient uptake by neighbouring plant species: evidence from intercropping.
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Zhang, Wei‐Ping, Liu, Guang‐Cai, Sun, Jian‐Hao, Fornara, Dario, Zhang, Li‐Zhen, Zhang, Fang‐Fang, Li, Long, and Niels, Anten
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PLANT nutrients , *PLANT species , *INTERCROPPING , *PLANT ecology , *ECOLOGICAL research - Abstract
The productivity of species-diverse plant assemblages strongly depends on the temporal dynamics of nutrient uptake by competing neighbouring plants. Our understanding, however, of how rates of nitrogen (N), phosphorous (P) and potassium (K) uptake might change through time between neighbouring plant species under field conditions is still very limited., Here, we specifically measure the temporal trajectories of N, P and K uptake by staple food plants such as wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.) and maize ( Zea mays L.) when growing either in monocultures or in intercropping systems. We ask how (i) plant species combinations, (ii) N fertilization and (iii) film mulching might affect key indexes of N, P and K uptake over time. We fit logistic models to characterize the nutrient uptake trajectories., Maximum cumulative N, P and K uptake (kg ha−1) by wheat and barley were significantly greater in wheat-maize or barley-maize intercropping systems than in wheat or barley monocultures. Cumulative nutrient uptake by intercropped maize (either with wheat or with barley) was reduced by interspecific competition at early growth stages, but it increased rapidly after wheat and barley were harvested. Maximum cumulative N and P (but not K) uptake by intercropped maize were significantly higher than the uptake by monoculture maize, particularly when N fertilizer or film mulching was applied., Intercropping induced a significant temporal niche differentiation in maximum daily nutrient uptake rates (kg ha−1 day−1) between intercropped species. Fertilization had much stronger effects on maximum cumulative nutrient uptake of maize than that of wheat and barley. Mulching significantly increased the maximum cumulative nutrient uptake of maize and advanced the time to reach its maximum daily P and K uptake rates., Our study provides evidence of an important temporal niche differentiation mechanism ('temporal complementarity') in nutrient uptake rates between neighbouring plant species. A better understanding of temporal trajectories of interspecific nutrient uptake rates remains crucial if we want to maximize the nutrient-use efficiency and sustain overyielding (i.e. high food production) in plant species-diverse systems such as intercropping. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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21. Space‐variant RCMC method for squint beam‐steering SAR imaging on high‐speed manoeuvring platforms.
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Bie, Bowen, Sun, Guang‐Cai, and Xing, Mengdao
- Abstract
The focusing of squint beam‐steering synthetic aperture radar (SAR) data is a challenging task for the technical difficulty of space‐variant range cell migration correction (RCMC). It is more complicated when considering the manoeuver of high‐speed platforms. The conventional Doppler domain RCMC method is with low performance and requires a large amount of zero‐padding. This Letter proposes a modified RCMC method which removes the space‐variant range cell migration (RCM) components by deramp‐keystone transform and then compensates the unified RCM terms in the time domain. Compared with the conventional method, the proposed one is with high performance and can avoid zero‐padding. This method is validated by the simulated SAR data. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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22. A LOCAL FRACTIONAL DERIVATIVE WITH APPLICATIONS TO FRACTAL RELAXATION AND DIFFUSION PHENOMENA.
- Author
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Yang ZHAO, Yan-Guang CAI, and Xiao-Jun YANG
- Subjects
- *
FRACTIONAL calculus , *DIFFERENTIAL equations , *CANTOR sets , *TOPOLOGY , *FINITE differences - Abstract
In this paper, a new application of the fractal complex transform via a local fractional derivative is presented. The solution for the fractal relaxation and time-fractal diffusion equations are obtained based on the sup-exponential functions defined on Cantor sets. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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- View/download PDF
23. Processing of Very High Resolution Spaceborne Sliding Spotlight SAR Data Using Velocity Scaling.
- Author
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Wu, Yuan, Sun, Guang-Cai, Yang, Chun, Yang, Jun, Xing, Mengdao, and Bao, Zheng
- Subjects
- *
SYNTHETIC aperture radar , *ALGORITHM research , *AZIMUTH , *HYPERBOLIC functions , *OPTICAL resolution - Abstract
In spaceborne synthetic aperture radar, the sliding spotlight mode can acquire high resolution and large azimuth scene size simultaneously. However, when the resolution is very high and the azimuth scene size is large, the traditional hyperbolic range model (HRM) is inaccurate and the variation of the equivalent velocity in azimuth dimension cannot be ignored. Thus, the traditional imaging algorithms based on HRM are no longer available. For this problem, this paper proposes an equivalent acceleration range model, which can precisely take into account the spaceborne curved orbit. Then, velocity scaling algorithm based on this new range model is proposed to meet the needs of very high resolution and large azimuth scene size. The results of the simulation validate the effectiveness of the new range model and the imaging algorithm. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
24. Lanthanide complexes with 3-bromine-4-methyl benzoic acid and 1,10-phenanthroline.
- Author
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Zong, Guang-Cai, Ren, Ning, Zhang, Jian-Jun, Qi, Xiao-Xia, and Gao, Jie
- Subjects
- *
RARE earth metals , *BROMINE , *BENZOIC acid , *PHENANTHROLINE , *CRYSTAL structure , *X-ray diffraction - Abstract
The crystal structures of complexes [Tb(3-Br-4-MBA)phen]( 1), [Ho(3-Br-4-MBA)(phen)HO]( 2) and [Er(3-Br-4-MBA)(phen)HO]( 3) (3-Br-4-MBA=3-bromine-4-methylbenzoate, phen=1,10-phenanthroline) have been solved by single-crystal X-ray diffraction methods. All obtained products were examined and characterized by elemental analysis, molar conductivity, IR, UV and XRD techniques. The thermogravimetric analysis of 1 to 3 was studied, indicating that the decomposition processes of 2 and 3 are different from 1. The mass loss of the first step for 2 and 3 is attributed to the HO molecules. The three-dimensional IR accumulation spectra of gaseous of 1 to 3 were also recorded. Complex 1 emits strong and bright green fluorescence under UV light at the room temperature. The bacteriostatic activities of the three complexes against bacteria, such as Escherichia coli and Staphylococcus aureus, and fungus (Candida albicans) were tested. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
25. Growth trajectories and interspecific competitive dynamics in wheat/maize and barley/maize intercropping.
- Author
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Zhang, Wei-Ping, Liu, Guang-Cai, Sun, Jian-Hao, Zhang, Li-Zhen, Weiner, Jacob, and Li, Long
- Subjects
- *
CROP growth , *INTERCROPPING , *PLANT competition , *FERTILIZER application , *MULCHING - Abstract
Background and Aims: Competition between intercropped species is important for yield advantage, but little attention has been given to interspecific competitive dynamics in intercropping. Methods: A field experiment with five cropping systems (wheat/maize, barley/maize intercropping, wheat, maize and barley sole cropping), two N levels (0 and 225 kg N ha) and two maize mulching treatments (with and without) were performed. Sequential harvest of subplots was performed between 7 and 10 times, and the data were fitted to a logistic growth model. Results: Intercropping significantly increased the maximum biomass and maximum growth rates of wheat and barley, but suppressed the early and maximum growth rate of intercropped maize. Maize growth recovered after the wheat or barley was harvested. In the presence of film mulch and/or fertilization, maximum biomass of intercropped maize was close to or significantly higher than that of maize alone. Fertilization and film mulching had much stronger effects on growth of maize than on wheat and barley. Conclusions: Interspecific competitive dynamics regulated by fertilization and film mulching can be quantified by the logistic model, which is helpful to understand the yield advantage of intercropping. This has important implications for managing interspecific competition through agronomic practices at field. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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26. Preparation, characterization and properties of four new trivalent lanthanide complexes constructed using 2-bromine-5-methoxybenzoic acid and 1,10-phenanthroline.
- Author
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Zong, Guang-Cai, Huo, Jian-Xia, Ren, Ning, Zhang, Jian-Jun, Qi, Xiao-Xia, Gao, Jie, Geng, Li-Na, Wang, Shu-Ping, and Shi, Shi-Kao
- Subjects
- *
RARE earth metals , *COMPLEX compounds , *BROMINE , *BENZOIC acid , *PHENANTHROLINE , *COORDINATE covalent bond , *LIGANDS (Chemistry) , *CHELATING agents - Abstract
Four dinuclear trivalent lanthanide complexes of the general formula [Ln2(2-Br-5-MOBA)6(phen)2] (Ln = Nd(1), Sm(2), Ho(3), Er(4); 2-Br-5-MOBA = 2-bromine-5-methoxybenzoate, phen = 1,10-phenanthroline) were prepared and structurally characterized. The complexes 1 to 4 are isostructural with a coordination number of nine. The carboxylic acid ligands adopt bridging, bidentate chelating, and tridentate chelating bridging modes to coordinate with Ln(iii) ions. The structures of the complexes were confirmed on the basis of elemental analysis, molar conductance, thermogravimetric analysis (TGA), and IR and UV spectra. The heat capacities and thermal circulating processes of the prepared complexes were performed on a differential scanning calorimeter under a nitrogen atmosphere. Two remarkable solid–solid phase transitions existed both in the heat capacities and thermal circulating processes. The bacteriostatic activities of the complexes were evaluated against Candida albicans, Escherichia coli and Staphylococcus aureus. Besides, the luminescent property of complex 2 was also investigated, and the magnetic properties of complexes 3 and 4 were also discussed in detail. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
27. Rapid identification of apolipoprotein E genotypes by high-resolution melting analysis in Chinese Han and African Fang populations.
- Author
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XIU-HUI ZHAN, GUANG-CAI ZHA, JI-WEI JIAO, LI-YE YANG, XIAO-FEN ZHAN, JIANG-TAO CHEN, DONG-DE XIE, EYI, URBANO MONSUY, MATESA, ROCIO APICANTE, ONDO OBONO, MAXIMO MIKO, EHAPO, CARLOS SALA, ER-JIA WEI, YU-ZHONG ZHENG, HUI YANG, and MIN LIN
- Subjects
- *
APOLIPOPROTEIN E , *GENETIC polymorphisms , *GENOTYPES , *POLYMERASE chain reaction , *ALLELES - Abstract
Apolipoprotein E (APOE) gene polymorphism can affect APOE gene transcription, serum lipid levels and repair of tissue damage, which could place individuals at serious risk of cardiovascular disease or certain infectious diseases. Recently, high-resolution melting (HRM) analysis was reported to be a simple, inexpensive, accurate and sensitive method for the genotyping or/and scanning of rare mutations. For this reason, an HRM analysis was used in the present study for APOE genotyping in the Southern Chinese Han and African Fang populations. A total of 100 healthy Southern Chinese Han and 175 healthy African Fang individuals attended the study. Polymerase chain reaction-DNA sequencing was used as a reference method for the genotyping of these samples. The six APOE genotypes could all be rapidly and efficiently identified by HRM analysis, and 100% concordance was found between the HRM analysis and the reference method. The allele frequencies of APOE in the Southern Chinese Han population were 7.0, 87.5 and 5.5% for ε2, ε3 and ε4, respectively. In the African Fang population, the allele frequencies of APOE were 24.3, 65.7 and 10.0% for ε2, ε3 and ε4, respectively. A statistically significant difference was found between the allele frequencies between the populations (P<0.05). In conclusion, the present study revealed the molecular characterization of APOE gene polymorphism in the Han population from the Chaozhou region of Southern China and the Fang population from Equatorial Guinea. The findings of the study indicated that HRM analysis could be used as an accurate and sensitive method for the rapid screening and identification of APOE genotypes in prospective clinical and population genetic analyses. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
28. A 2-D Space-Variant Chirp Scaling Algorithm Based on the RCM Equalization and Subband Synthesis to Process Geosynchronous SAR Data.
- Author
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Guang-Cai Sun, Mengdao Xing, Yong Wang, Jun Yang, and Zheng Bao
- Subjects
- *
GEOSTATIONARY satellites , *SYNTHETIC aperture radar , *LOW earth orbit satellites , *POLYNOMIALS , *ALGORITHMS - Abstract
A space-variant chirp scaling algorithm based on the range cell migration (RCM) equalization and azimuth subband synthesis has been studied to process simulated geosynchronous synthetic aperture radar (GEO-SAR) data. The acceptable order of terms in polynomials for the slant range models in the RCM correction and phase error compensation, division of subband, and suppression of grating lobes of the subbands was investigated. Qualitatively and quantitatively, the method was able to focus simulated GEO-SAR signals well. Finally, the constraint on the spatial extent of azimuth and range dimensions using the algorithm was assessed. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
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- View/download PDF
29. Multichannel Full-Aperture Azimuth Processing for Beam Steering SAR.
- Author
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Sun, Guang-Cai, Xing, Mengdao, Xia, Xiang-Gen, Wu, Yufeng, Huang, Pingping, Wu, Yirong, and Bao, Zheng
- Subjects
- *
AZIMUTH , *BEAM steering , *SYNTHETIC aperture radar , *HIGH resolution imaging , *SPACE-time adaptive signal processing - Abstract
Terrain Observation by Progressive Scans (TOPS) synthetic aperture radar (SAR) and spotlight SAR are advanced SAR imaging modes for wide range swath and high resolution. In order to obtain a wider range coverage, azimuth multichannel is introduced in the literature. Since the azimuth bandwidth of beam steering SAR (BS-SAR; spotlight SAR, sliding spotlight SAR, or TOPS SAR) is much greater than that of a stripmap SAR, a signal reconstruction algorithm used for multichannel stripmap SAR may not be effective for multichannel BS-SAR. In this paper, a multichannel full-aperture azimuth processing algorithm is proposed for a BS-SAR. The key of this algorithm lies in the beam and the azimuth bandwidth compressions of multichannel signals in the Doppler–array and slow time–angle planes, respectively. Through compression processing, the beamwidth and the azimuth bandwidth are smaller than the available angle and equivalent pulse repeating frequency , respectively. Then, an improved post-Doppler STAP method is proposed to recover a 2-D spectrum. With the recovered signal, further processing can be utilized to focus the multichannel signal. Simulation and real data results show the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
30. Beam Steering SAR Data Processing by a Generalized PFA.
- Author
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Sun, Guang-Cai, Xing, Mengdao, Xia, Xiang-Gen, Wu, Yirong, and Bao, Zheng
- Subjects
- *
SYNTHETIC aperture radar , *DIRECTIONAL antennas , *OPTICAL resolution , *AZIMUTH , *ALGORITHMS , *SIMULATION methods & models - Abstract
For different applications with different requirements, many synthetic aperture radar (SAR) modes have been developed in the literature, such as, Terrain Observation by Progressive Scans (TOPS) SAR and sliding spotlight SAR. In this paper, we call TOPS SAR, sliding spotlight SAR, and spotlight SAR as beam steering SAR (BS-SAR for short). Comparing with stripmap SAR, BS-SAR can obtain a wide diversity of resolutions by increasing or reducing the azimuth synthetic time. Traditional polar formation algorithm (PFA) is an efficient algorithm which is mainly developed for spotlight SAR. The PFA has been validated to obtain well-focused results of raw data. In this paper, we extend the traditional PFA to process sliding spotlight SAR and TOPS SAR data, and we call it generalized PFA (GPFA). Comparing with the traditional PFA, GPFA contains a different azimuth deramping function and an additional azimuth scaling operation. The simulated and real data are used to validate the effectiveness of this method. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
31. A Unified Focusing Algorithm for Several Modes of SAR Based on FrFT.
- Author
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Sun, Guang-Cai, Xing, Mengdao, Xia, Xiang-Gen, Yang, Jun, Wu, Yirong, and Bao, Zheng
- Subjects
- *
IMAGING systems , *FOURIER transforms , *SYNTHETIC aperture radar , *ALGEBRA , *ALGORITHMS - Abstract
Many imaging algorithms for different modes, such as, stripmap synthetic aperture radar (SAR), spotlight SAR, sliding spotlight SAR, and terrain observation by progressive scans (TOPS) SAR, of SAR have been studied. This paper is to obtain a unified focusing algorithm (UFA) for these SAR modes based on fractional Fourier transform. By defining the rotation-center range, the stripmap SAR and spotlight SAR can be treated as special cases of sliding spotlight SAR or TOPS SAR. Then, a parameterized focusing algorithm determined by the rotation-center range is presented. Data of each mode can be focused by utilizing UFA and selecting parameters or rotation angles. Some application aspects of UFA are also analyzed. Simulation and real data results are presented to validate the analysis and the proposed method. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
32. Hepatic Resection is Safe for Metachronous Hepatic Metastases from Ovarian Cancer.
- Author
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Guang-cai Niu, Chang-ming Shen, Wei Cui, and Qiang Li
- Subjects
- *
SURGICAL excision , *OPERATIVE surgery , *LIVER surgery , *METASTASIS , *OVARIAN cancer - Abstract
Objective To explore the efficacy of hepatic resection (HR) in a relatively unselected group of patients with ovarian cancer liver metastases (OCLM). Methods A study was conducted between September 2000 and September 2011 on 60 ovarian cancer patients with hepatic metastases (24 solitary and 36 multiple), 40 of whom had extrahepatic metastases. HR was done in all patients provided that curative hepatic resection was feasible, and extrahepatic disease was controlled with medical and/or surgical therapy. Results Most patients (n=54; 90.0%) had a negative hepatic margin (R0), whereas 6 patients (10.0%) had microscopic disease at the margin (R1). The prognostic value of each study variable was assessed using log rank tests for univariate analysis and Cox proportional hazard models for multivariate analysis. The result was a median survival of 39 months and 5-year overall survival rate of 30%. Univariate analysis showed that surgery result (P=0.001), disease free interval (P=0.018) and the number of hepatic lesions (P=0.018) were significantly related to survival. Furthermore, the surgery result (P=0.004) remained significant for prognosis in multivariate analysis. Conclusions For patients with OCLM, HR is safe and may provide a significant survival benefit compared with medical therapy alone. A long interval time, the number of hepatic lesions, and surgery results are key prognostic factors. Favorable outcomes can be achieved even in patients with medically controlled or surgically resectable extrahepatic disease, indicating that surgery should be considered more frequently in the multidisciplinary care of patients with OCLM. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
33. Phytoaccumulation of copper in willow seedlings under different hydrological regimes
- Author
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Chen, Guang-Cai, Liu, Zhikun, Zhang, Jianfeng, and Owens, Gary
- Subjects
- *
SEEDLINGS , *WILLOWS , *HYDROLOGY , *PLANT biomass , *EFFECT of copper on plants , *BIOACCUMULATION in plants , *PLANT-soil relationships , *PLANT roots - Abstract
Abstract: Plant biomass and copper (Cu) accumulation by Salix jiangsuensis CL ‘J-172’ and Salix babylonica Linn grown in Cu spiked soils were investigated under different hydrological regimes to assess the suitability of willow for phytoremediation of contaminated wetlands. The results showed that willow can maintain normal growth with no visual symptoms of Cu toxicity, suggesting that willow has high resistance to the combined stresses of Cu and waterlogging. The elevated Cu concentration in soil significantly decreased the biomass and increased Cu content in the roots of the two species. Flooding increased Cu accumulation in the roots and decreased Cu accumulation in the stems and leaves. Considering the large biomass of willow and its metal accumulation ability, willow has the potential for use in phytoremediation of Cu-contaminated wetlands. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
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34. Rapid Analysis of Apple Leaf Nitrogen using Near Infrared Spectroscopy and Multiple Linear Regression.
- Author
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Zhang, Guang-Cai, Li, Zhuang, Yan, Xiang-Mei, Cheng, Cun-Gang, Zhou, Ping, Lin, Guo-Lin, Zhou, Chong-Jun, Liu, Ning, and Han, Xiao-Ri
- Subjects
- *
NITROGEN content of plants , *NEAR infrared spectroscopy , *REGRESSION analysis , *APPLES , *STANDARD deviations , *DATA analysis , *INFRARED spectroscopy - Abstract
A quick method was developed for diagnosis of nitrogen (N) in apple trees based on multiple linear regressions to establish the relationship between near-infrared reflectance spectra (NIRS) and the N contents of fresh and dry tissue. Spectral pretreatment methods such as derivatives, smoothing, and normalization were used. The derivatives appeared to be the most effective. The best calibration for fresh leaf gave 0.842 for the correlation coefficient of validation (Rv), 1.119 g kg−1 for the root mean square error of prediction (RMSEP), and 8.311 for the ratio of the range in reference data from the validation samples to the root mean square error of prediction (RER). The best calibration for dried ground samples was obtained with Rv = 0.952, RMSEP = 0.633 g kg−1, the ratio performance deviation (RPD) = 3.27, and RER = 13.728. The results showed that calibrations of dry-apple leaf are robust enough for an accurate prediction of N. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
35. Water film motor driven by alternating electric fields: Its dynamical characteristics.
- Author
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Zhong-Qiang Liu, Guang-Cai Zhang, Ying-Jun Li, and Su-Rong Jiang
- Subjects
- *
ELECTRIC fields , *LIQUID films , *WATER , *ELECTRIC motors , *DIRECT currents , *ELECTROHYDRODYNAMICS , *POLARIZATION (Electricity) , *ELECTRIC conductivity , *VISCOSITY - Abstract
The "liquid film motor," a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference, (ii) Vibrations may be induced by fields with different frequencies, (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
36. Airflow and Heat Transfer in the Slot-Vented Room with Radiant Floor Heating Unit.
- Author
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Liu, Xiang-Long, Gong, Guang-Cai, Cheng, Heng-Sheng, and Ding, Li-Xing
- Subjects
- *
AIR flow , *HEAT transfer , *RADIANT floor heating , *ENERGY consumption , *HEATING , *INDOOR air quality , *MATHEMATICAL combinations , *CONFERENCES & conventions - Abstract
Radiant floor heating has received increasing attention due to its diverse advantages, especially the energy saving as compared to the conventional dwelling heating system. This paper presents a numerical investigation of airflow and heat transfer in the slot-vented room with the radiant floor heating unit. Combination of fluid convection and thermal radiation has been implemented through the thermal boundary conditions. Spatial distributions of indoor air temperature and velocity, as well as the heat transfer rates along the radiant floor and the outer wall, have been presented and analyzed covering the domains from complete natural convection to forced convection dominated flows. The numerical results demonstrate that the levels of average temperature in the room with lateral slot-ventilation are higher than those without slot-ventilation, but lower than those in the room with ceiling slot-ventilation. Overall, the slot-ventilation room with radiant floor heating unit could offer better indoor air quality through increasing the indoor air temperature and fresh air exchanging rate simultaneously. Concerning the airborne pollutant transports and moisture condensations, the performance of radiant floor heating unit will be further optimized in our future researches. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
37. Adsorption of diuron and dichlobenil on multiwalled carbon nanotubes as affected by lead
- Author
-
Chen, Guang-Cai, Shan, Xiao-Quan, Pei, Zhi-Guo, Wang, Huanhua, Zheng, Li-Rong, Zhang, Jing, and Xie, Ya-Ning
- Subjects
- *
ADSORPTION (Chemistry) , *DIURON , *NITRILES , *CARBON nanotubes , *LEAD , *HERBICIDES , *WATER pollution , *FOURIER transform infrared spectroscopy , *METAL complexes - Abstract
Abstract: The effect of lead on the adsorption of diuron and dichlobenil on multiwalled carbon nanotubes (MWCNTs) was investigated to explore the possible application of MWCNTs for removal of both herbicides from contaminated water. The adsorption of diuron and dichlobenil on MWCNTs at pH 6 was nonlinear and fit the Polanyi–Manes model well. The adsorption of diuron and dichlobenil was closely correlated with specific surface areas and micropore volumes of MWCNTs. An increase in oxygen content of MWCNTs with same diameters and similar surface areas decreased the adsorption of diuron and dichlobenil, while increased the adsorption of lead. Micro-Fourier transform infrared spectroscopic study indicated that hydrogen bonding is a main mechanism responsible for the adsorption of diuron or dichlobenil onto MWCNTs-O. Oxygen containing groups, mainly carboxylic groups, significantly increased the adsorption of lead through the formations of outer-sphere and inner-sphere complexes, which are verified by X-ray absorption spectroscopic measurements. Oxygen containing groups and the presence of lead diminished the adsorption of diuron and dichlobenil. The suppression mechanisms of lead were ascribed to hydration and complexation of lead with carboxylic groups, which may occupy part of surface of MWCNTs-O. The large hydration shell of lead cations may intrude or shield hydrophobic and hydrophilic sites, resulting in a decreased adsorption of diuron and dichlobenil at the lead-complexed moieties. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
38. Water shortages and countermeasures for sustainable utilisation in the context of climate change in the Yellow River Delta region, China.
- Author
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Zhang, Jianfeng, Chen, Guang-Cai, Xing, Shangjun, Shan, Qihua, Wang, Ying, and Li, Zebo
- Subjects
- *
WATER shortages , *WATER supply , *CLIMATE change , *ECONOMIC development , *RESOURCE management , *BIOTIC communities , *SUSTAINABLE development - Abstract
With an increasing population and rapid development of the economy and society of the Yellow River Basin region, the Yellow River is at crisis point. The discrepancy between supply and demand of water resources is a key issue. In 2000-2006, the mean annual discharge of the Yellow River entering the delta was 13.2 billion m3, a reduction of 18.6 billion m3 compared with the 1980s, and 9 billion m3 less than in the 1990s. The water requirements of various sectors are increasing. Large amounts of water essential to maintain the health of the delta ecosystem have been diverted for other users. The lower river channel is shrinking and the threat of flooding is becoming severe. Moreover, water pollution is increasing to a serious level; the river mouth ecosystem is subject to degradation. Due to overall decreased flow into the delta, and almost no flow into the delta for much of the year except in wet periods, biodiversity is threatened and there has been degradation of the ecological environment. In view of the water scarcity and variation in water supply, particularly in the context of climate change, measures need to be taken to realise sustainable water use in the Yellow River Delta region. In view of the lack of a complete index system for sustainable utilisation of regional water resources in China, this paper examines the major countermeasures for sustainable water use in the region. A rational adjustment mechanism for water prices is needed. Adjustment of agricultural infrastructure and water saving need to be directed by water prices, and thus the reasonable exploitation of groundwater must also be directed by water prices. Participation of the public is to be encouraged, with the development of a water user association that will become involved in formulating water rights, water allocation and water prices. Decision-making, management and supervision of this association will be done in a democratic way to promote the social management of water saving. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
39. Atypical Class 1 Integron Coexists with Class 1 and Class 2 Integrons in Multi-Drug Resistant Shigella flexneri Isolates from China.
- Author
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Jing Yuan Zhu, Guang Cai Duan, Hai Yan Yang, Qing Tang Fan, and Yuan Lin Xi
- Subjects
- *
ANTI-infective agents , *SHIGELLA flexneri , *PLASMIDS , *CHROMOSOMES , *ESCHERICHIA coli - Abstract
The antimicrobial resistance and the character of integrons were determined in 58 Shigella flexneri strains isolated from China. All isolates were multi-drug resistant and found to carry integrons of class 1 (94.8%), class 2 (100%), or both (94.8%). No intI3 was detected. The typical class 1 integrons were found in conjugative plasmids and could be transferred to the recipient E. coli DH5α. The gene cassettes of typical class 1 integrons dfrA17- aadA5 and dfrA12- orfF- aadA2 were detected in 54 strains (93.1%) and 1 strain, respectively. Atypical class 1 integrons located on the chromosome with gene cassettes bla- aadA1 were detected in 55 isolates (94.8%). All the intI2 positive isolates carried gene cassettes dfrA1- sat1- aadA1. To our knowledge, this is the first report that atypical and typical class 1 integrons coexisted with class 2 integron in multi-drug resistant S. flexneri strains. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
40. Carbon sequestration of black locust forests in the Yellow River Delta region, China.
- Author
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Zhang, Jianfeng, Chen, Guang-Cai, Xing, Shangjun, Sun, Qixiang, Shan, Qihua, Zhou, Jinxing, and Wang, Ying
- Subjects
- *
CARBON sequestration , *AFFORESTATION , *BLACK locust , *CARBON dioxide & the environment , *BIOMASS , *HERBACEOUS plants - Abstract
The Yellow River Delta region in China is a land area of 1,200,000 ha with rich natural resources. Adverse environmental conditions, such as low rainfall and high salinity, promote the dominance of black locust trees for afforestation. With the increase of CO2 in the atmosphere, this forest and others throughout the world have become valued for their ability to sequester and store carbon. Forests store carbon in aboveground biomass (i.e. trees), belowground biomass (i.e. roots), soils and standing litter crop (i.e. forest floor and coarse woody debris). There are well-developed methods to sample forest ecosystems, including tree inventories that are used to quantify carbon in aboveground tree biomass. Such inventories are used to estimate the types of roundwood products removed from the forest during harvesting. Based on standard plot inventories and stem analyses, carbon sequestration estimates of trees were 222.41 t ha-1 for the Yellow River Delta region accounted for 67.12% of the whole forest. Similarly, carbon storage by herbaceous matter and soil was 0.50 and 50.34 t ha-1, respectively. The results suggest that carbon sequestration in the forest ecosystem was performed by most of the forest, which plays an increasingly important role in sequestering carbon as the stand grows. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
41. Microstructure transformations induced by modified-layers on pentacene polymorphic films and their effect on performance of organic thin-film transistor
- Author
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Yuan, Guang-Cai, Lu, Zhisong, Xu, Zheng, Gong, Cheng, Song, Qun-Liang, Zhao, Su-Ling, Zhang, Fu-Jun, Xu, Na, Gan, Ye, Yang, Hong-Bin, and Li, Chang Ming
- Subjects
- *
MICROSTRUCTURE , *PENTACENE , *THIN film transistors , *ORGANIC electronics , *ELECTRIC insulators & insulation , *MOLECULAR structure , *CRYSTALS , *ATOMIC force microscopy - Abstract
Abstract: Phenyltrimethoxysilane was used to modify SiO2 insulator and significantly enhanced the pentacene based organic thin-film transistors (OTFTs). The crystal structure, surface morphology, molecular structure and microstructure of pentacene polymorphic films with and without the modifications were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle meter. XRD studies reveal a decreased tilt angle (θT ) of pentacene molecules from c-axis toward a-axis, indicating that polymorphs transformation from the “triclinic bulk” phase to the “thin film” phase and orthorhombic phase occurs. AFM images show that the surface roughness of gate insulators has no influence on performance of the pentacene based OTFT. These results provide strong evidence that the performance improvement of OTFT after PhTMS modification of SiO2 insulator surface is related to the microstructure transformation of the semiconductor. It suggests that the modified-layer may alter the molecular geometry and further induce structural phase transitions in the pentacene films for the performance improvement. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
42. Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes
- Author
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Chen, Guang-Cai, Shan, Xiao-Quan, Zhou, Yi-Quan, Shen, Xiu-e, Huang, Hong-Lin, and Khan, Shahamat U.
- Subjects
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CARBON nanotubes , *ADSORPTION (Chemistry) , *ATRAZINE , *EFFECT of temperature on chemical kinetics , *THERMODYNAMICS , *REGRESSION analysis , *CHEMICAL models , *ATMOSPHERIC temperature - Abstract
Abstract: The adsorption kinetics, isotherms and thermodynamic of atrazine on multiwalled carbon nanotubes (MWCNTs) containing 0.85%, 2.16%, and 7.07% oxygen was studied. Kinetic analyses were performed using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. The regression results showed that the pseudo-second-order law fit the adsorption kinetics. The calculated thermodynamic parameters indicated that adsorption of atrazine on MWCNTs was spontaneous and exothermic. Standard free energy (ΔG 0) became less negative when the oxygen content of MWCNTs increased from 0.85% to 7.07% which is consistent with the low adsorption affinity of MWCNTs for atrazine. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
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43. Study on characteristics of a double-conductible channel organic thin-film transistor with an ultra-thin hole-blocking layer.
- Author
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Yuan Guang-Cai, Xu Zheng, Zhao Su-Ling, Zhang Fu-Jun, Xu Na, Tian Xue-Yan, and Xu Xu-Rong
- Subjects
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ORGANIC thin films , *THIN film transistors , *PHENANTHROLINE , *INTERFACES (Physical sciences) , *PENTACENE , *THRESHOLD voltage - Abstract
The properties of top-contact organic thin-film transistors (TC-OTFTs) using ultra-thin 2, 9-dimethyl-4, 7- diphenyl-1, 10-phenanthroline (BCP) as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers are limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate in- sulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at VDS = -20 V showed excellent hole mobility µFE and threshold voltage VTH of 0.58 cm2/(V·s) and -4.6 V, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
44. Adsorption of 2,4,6-trichlorophenol by multi-walled carbon nanotubes as affected by Cu(II)
- Author
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Chen, Guang-Cai, Shan, Xiao-Quan, Wang, Yu-Sheng, Wen, Bei, Pei, Zhi-Guo, Xie, Ya-Ning, Liu, Tao, and Pignatello, Joseph J.
- Subjects
- *
ADSORPTION (Chemistry) , *SCIENTIFIC experimentation , *CHEMICAL equilibrium , *TRICHLOROPHENOL , *CARBON nanotubes , *INDUSTRIAL applications of copper , *X-ray spectroscopy - Abstract
Adsorption equilibrium of 2,4,6-trichlorophenol (TCP) on multi-walled carbon nanotubes (MWCNTs) was investigated to explore the possibility of using MWCNTs for concentration, detection and removal of TCP from contaminated water. The adsorption of TCP on MWCNTs at pH 4 was nonlinear, reversible and best fit by a Polanyi¿Manes model. Oxidation treatment increased surface area and introduced hydrophilic carboxylic groups to the defect sites of MWCNTs, hence increased the sorption of TCP and Cu(II) individually. Cu(II) suppressed the sorption of TCP on oxidized MWCNTs15A, but had little effect on as-grown MWCNTs15. TCP had no influence on Cu(II) sorption to either. The mechanisms of Cu(II) suppression effect on TCP adsorption are ascribed to the formation of surface complexes of Cu(II), which was verified by X-ray absorption spectroscopy. Cu(II) exerts a cross-linking effect of functional groups on adjacent tubes, creating a more tightly knit bundle and suppressing the condensation of TCP in the pore spaces between the tubes. The large hydration sphere around surface complexes of Cu(II) may also intrude or shield hydrophilic sites, leading to the ¿crowding out¿ of TCP around the Cu(II)-complexed sites. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
45. Composition influence of SiNx gate insulator fabricated by radio frequency (RF) Magnetron sputtering on characteristics of organic thin-film transistors
- Author
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Yuan, Guang-Cai, Xu, Zheng, Zhao, Su-Ling, Zhang, Fu-Jun, Jia, Xiao-Yun, Xu, Na, Sun, Qin-Jun, and Xu, Xu-Rong
- Subjects
- *
ORGANIC thin films , *THIN film transistors , *RADIO frequency , *MAGNETRON sputtering , *ORGANIC semiconductors , *ELECTRIC insulators & insulation , *GATE array circuits , *PENTACENE , *SILICON nitride - Abstract
Abstract: To investigate the effect of composition of SiNx on the properties of organic thin-film transistors (OTFTs), we fabricated bottom gate top contact OTFTs devices with different composition SiNx gate insulator. Pentacene based OTFTs with SiNx insulator, prepared using an interface modification process of UV-ozone treatment, exhibited effective mobility of 0.63cm2/Vs and on/off current ratio of 105. Overall improvement in field-effect mobility, threshold voltage was observed as silicon content in SiNx increases. The results demonstrate that the viability of using SiNx for OTFTs and of UV-ozone treatment could be used to improve the properties of organic thin-film transistors. The dependence of the contact angle on the SiNx film composition is evident for the untreated samples, the contact angle increases as the silicon content in the untreated nitride film increases. In contrast, the rise in contact angle across all samples after surface treatment signifies effective surface modification to promote hydrophobicity of the nitride surface. The hydrophobic surface is needed for the organic semiconductor. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
46. Effects of Copper, Lead, and Cadmium on the Sorption and Desorption of Atrazine onto and from Carbon Nanotubes.
- Author
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GUANG-CAI CHEN, XIAO-QUAN SHAN, YU-SHENG WANG, ZHI-GUO PEI, SHEN, XIU-E., WEN, BET, and OWENS, GARY
- Subjects
- *
CARBON nanotubes , *ATRAZINE , *ABSORPTION , *COPPER , *LEAD , *CADMIUM , *HYDRATION , *IONS , *HYDROGEN bonding , *NITROGEN - Abstract
There are currently few studies on the dual effects of metal ions on the sorption of atrazine and conversely of atrazine on metal adsorption on multiwalled carbon nanotubes (MWCNTs). While a number of sorption models were considered to describe the sorption of atrazine on MWCNTs, the Polanyi-Manes model (PMM) fit the sorption isotherms well with the lowest mean weighted square errors. Atrazine was mainly adsorbed onto the surface and micropores of MWCNTs bundles or aggregates. Hydrogen bonding between azo and amino nitrogen of atrazine and functional groups on MWCNTs also occurred. Oxygenated functionalities, mainly carboxylic groups on MWCNTs surface, decreased the sorption of atrazine. Metal cations Cu2+, Pb2+, and Cd2+ diminished the sorption of atrazine depending on the oxygenated functionalities densities. The mechanisms ascribed were due to the formation of surface or inner-sphere complexes of Cu2+, pb2+ and Cd2+ through carboxylic groups and hydration, which may occupy part of the surface of MWCNTs-O. The large hydration shell of metal cations may intrude or shield the hydrophobic and hydrophilic sites and indirectly compete with atrazine for surface sites, leading to the inhibition of atrazine adsorption around the metalcomplexed moieties. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
47. High squint multichannel SAR imaging algorithm for high speed maneuvering platforms with small-aperture.
- Author
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Li, Ning, Sun, Guang-Cai, Li, Boyu, Liu, Wenkang, Yang, Jun, Xing, Mengdao, and Bao, Zheng
- Subjects
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SYNTHETIC aperture radar , *SIGNAL reconstruction , *STRABISMUS , *DOPPLER effect , *AZIMUTH , *SPECTRAL lines , *SPECTRAL line broadening , *HILBERT-Huang transform - Abstract
• The space time spectrum of the high-speed maneuvering platforms multichannel SAR signal is irregular, in which the space time spectral lines are nonlinear and there is a massive Doppler spectrum shift. • Unambiguous Doppler spectrum can be obtained by the range-dependent signal reconstruction method based on space time spectrum correction. • Range variations of range cell migration can be addressed by a modified Stolt mapping. • The time domain spectrum compression function can be used to eliminate the time domain aliasing of small-aperture data without zero-padding. For high speed maneuvering platforms, multichannel synthetic aperture radar (SAR) can realize wide-swath imaging more flexibly at a high squint. In this mode, the signal reconstruction and imaging is a challenging task because the direction of the channel array vector is time-variant and inconsistent with the radar velocity vector. In this paper, the properties of space time spectrum are analyzed in detail at first. It is found that the space time spectrum of the signal is irregular, in which the space time spectral lines are nonlinear and there is a massive Doppler spectrum shift. Therefore, a range-dependent signal reconstruction method based on space time spectrum correction is proposed to obtain the unambiguous Doppler spectrum. For wide-swath data processing, an improved Omega-K approach based on time domain spectrum compression is further proposed to obtain a well-focused image. A modified Stolt mapping is used to address the range variations of range cell migration (RCM). Subsequently, a time domain spectrum compression function is used to eliminate the time domain aliasing of small-aperture data without zero-padding. Simulation results and real data processing are presented to validate the proposed algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
48. Vehicle Trace Detection in Two-Pass SAR Coherent Change Detection Images With Spatial Feature Enhanced Unet and Adaptive Augmentation.
- Author
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Zhang, Jinsong, Xing, Mengdao, Sun, Guang-Cai, and Shi, Xin
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SYNTHETIC aperture radar , *CONVOLUTIONAL neural networks , *DATA augmentation , *REMOTE sensing , *CHARGE coupled devices - Abstract
As a typical application of remote sensing technology, change detection can find the ground information changes by acquiring the images of the same region at different times. The change detection using the synthetic aperture radar (SAR) with the advantages of all day and all-weather usually monitors the significant surface change, such as flood disasters and earthquake deformation. However, when it comes to detecting subtle changes such as vehicle traces, the traditional methods ignoring the phase coherence between image pairs cannot intensify these faint changes in the difference image. The SAR coherent change detection (CCD) based on repeat-pass repeat-geometry complex images utilizing both the intensity and phase fraction could exhibit the subtle vehicle trace in the difference image. However, the complicated background and decorrelation factors significantly affect the quality of difference images, further causing great trouble for automatic trace detection. This article proposes the spatial feature enhanced Unet and adaptive data augmentation to realize vehicle trace detection. More specifically, the pseudocolor image is first synthesized based on a two-stage coherence estimation method. Then, considering the long-continuity and parallel distribution of vehicle trace samples, the enhanced Unet is constructed by fusing spatial convolutional neural network and spatial attention mechanism. After that, the adaptation data augmentation strategy is presented by introducing manual registration errors and multiple estimation windows. Finally, the experimental results on the Sandia CCD data and our measured data demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
49. Space-variant RCMC method for squint beam-steering SAR imaging on high-speed manoeuvring platforms.
- Author
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Bowen Bie, Guang-Cai Sun, and Mengdao Xing
- Subjects
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SYNTHETIC aperture radar , *BEAM steering , *DOPPLER effect , *ADAPTIVE signal processing , *TIME-domain analysis - Abstract
The focusing of squint beam-steering synthetic aperture radar (SAR) data is a challenging task for the technical difficulty of space-variant range cell migration correction (RCMC). It is more complicated when considering the manoeuver of high-speed platforms. The conventional Doppler domain RCMC method is with low performance and requires a large amount of zero-padding. This Letter proposes a modified RCMC method which removes the space-variant range cell migration (RCM) components by deramp-keystone transform and then compensates the unified RCM terms in the time domain. Compared with the conventional method, the proposed one is with high performance and can avoid zero-padding. This method is validated by the simulated SAR data. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
50. High performance organic thin film transistor with phenyltrimethoxysilane-modified dielectrics.
- Author
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Guang Cai Yuan, Zheng Xu, Cheng Gong, Qin Jia Cai, Zhi Song Lu, Jing Sheng Shi, Fu Jun Zhang, Su Ling Zhao, Na Xu, and Chang Ming Li
- Subjects
- *
ORGANIC thin films , *THIN film transistors , *SEMICONDUCTOR junctions , *PENTACENE , *SOLID state electronics - Abstract
In this work, fabrication of organic thin film transistors (OTFTs) using a phenyltrimethoxysilane (PhTMS) modified SiO2 insulator greatly improves the device electrical properties over those with plain or octadecyltrichlorosilane (OTS) modified SiO2, particularly improves the carrier mobility, the subthreshold slope, and channel resistance resulted from reduced density of charge trapping states at the semiconductor/insulator interface. The pentacene OTFTs with modification from PhTMS (3.5‰ v/v) achieves carrier mobility of 1.03 cm2/V s, on/off current ratio of 1.98×105, and subthreshold slope of 0.20 V/decade. This work renders a new, simple approach to significantly improve the OTFT performance. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
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