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Current Issue
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Dynamic study and vibration suppression mechanism of rotor system with adjustable elliptical journal bearings
- ZHANG Lei, PEI Shiyuan, XU Hua
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2019, 36 (1):
15-24.
DOI: 10.7523/j.issn.2095-6134.2019.01.004
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Abstract (
268 )
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Elliptical bearings are widely used in many large and critical equipments. Elliptical bearings are usually designed based on certain conditions. However, in the actual operation processes, the speed and load parameter changes affect the dynamic characteristics of rotor bearing support system. The dynamic characteristics under the steady conditions do not meet the actual working conditions. In order to adapt to the time-varying conditions and maintain the stability of the rotor bearing system under different working conditions, an elliptical bearing with adjustable parameters is proposed in this study. By adjusting the oil film gap of the bearing, the influences of ellipticity on the stiffness and damping of the bearing oil film is studied. Then the dynamic analysis for the rotor bearing systems with different ellipticity values is carried out. Finally, a test rig for rotor bearing is set up to verify that the rotor vibration can be effectively suppressed by adjusting the oil film gap of the elliptical bearing.
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Influence of the strong magnetic field on free surface thermocapillary convection of an electrically conductive fluid
- CHEN Ran, WANG Zenghui, NI Mingjiu
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2019, 36 (1):
25-30.
DOI: 10.7523/j.issn.2095-6134.2019.01.005
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Abstract (
255 )
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The divertor of the nuclear fusion device effectively shields the impurities from the wall and discharges the particle flow and heat flow from the central plasma. The liquid metal performs this task well. Liquid metal has the characteristics of strong thermal conductivity, large liquid temperature range, and easy supplement. It is one of the principal materials for plasma facing components in future fusion reactor. There are large temperature differences at different locations of the divertor. Under the action of surface tension, the thermocapillary convection is formed on the free surface of liquid metal, and the thermocapillary convection is affected by the strong magnetic field of the fusion reactor. The visual experimental results have been obtained through the establishment of the conductive fluid free surface thermocapillary convection experiment system. We have studied the influences of temperature change and strong magnetic field parameters on the conductive fluid free surface thermocapillary convection. In-depth analysis of the process has important significance for successful application of liquid metal as plasma facing components in future fusion.
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Pinhole-array-based single-shot ptychography with dual-wavelenghth
- LUO Yong, XU Wenhui, SHI Yishi
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2019, 36 (1):
31-37.
DOI: 10.7523/j.issn.2095-6134.2019.01.006
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Abstract (
398 )
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The traditional ptychographic imaging engine effectively improves the imaging quality and anti-noise ability of the system when the number of wavelengths involved in imaging increases, and it has been widely used in the fields of imaging and measurement. However, the complicated mechanical moving exposure method leads to jittering of the system, data acquisition inefficiency, and poor accuracy, and increase in the number of imaging wavelengths even more seriously affects the system imaging and measurement performance. In this work, the pinhole-array dual-wavelength single-shot ptychographic imaging is used. Actual optical experiments and numerical simulation demonstrate that the experimental data can be collected efficiently with double wavelength and high precision, and the drawbacks of traditional multiwavelength stack imaging are avoided. We also point out and demonstrat that, in choosing the laser wavelength involved in imaging, it is necessary to consider two important wavelength parameters, center wavelength and wavelength interval, which provides effective guidance for multiwavelength multilayer imaging technology. The pinhole-array-based single-shot ptychographic imaging with dual-wavelength has higher efficiency and a wider range of applications, compared with the traditional dual wavelength and multiwavelength ptychographic imaging engines.
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Photoregulating primer extension using azobenzene linked DNA template
- JI Heming, KONG Dejia, MO Mengwu, LEI Huajun, CHEN Lu, ZHAO Ruiqi, WANG Wei, HE Yujian, FENG Lutian, WU Li
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2019, 36 (1):
38-47.
DOI: 10.7523/j.issn.2095-6134.2019.01.007
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Abstract (
342 )
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It has been a hot topic in recent years to carry out a series of life activities by artificial reversible manipulation of specific gene expression. In this work, the photocontrol of primer extension directed by azobenzene modified DNA templates was investigated. DNA templates attached by protective ODNs with 5, 6, 7, and 8 complementary bases through 4,4'-bis(hydroxymethyl) azobenzene were systematically evaluated in photoregulation of the primer extension without or with UV irradiation. The results showed high efficiencies of C3 with 7 protected bases and C2 with 6-base short chains for photoregulating Pri.15 and Pri.17, respectively. Especially, for C3, when catalyzed by Vent DNA polymerase, primer extension efficiency had one-fold increase upon UV irradiation. Similarly, for C2, the extension efficiency reached 91.4% with UV irradiation and achived 84% increase, compared to that without UV irradiation, although the background of primer extension in the dark was a little high. This work provides a new strategy or means for studying the gene function and gene expression network and for exploring the occurrence and development of disease at the molecular level.
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Spatial-temporal variation of NDVI and its responses to precipitation and temperature in Inner Mongolia from 2001 to 2015
- LI Shuting, ZHOU Yi, WANG Shixin, SHANG Ming, YANG Baolin
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2019, 36 (1):
48-55.
DOI: 10.7523/j.issn.2095-6134.2019.01.008
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Abstract (
382 )
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Using the 2001-2015 MODIS NDVI datasets along with the meteorological data (temperature and precipitation), we analyzed the correlations of NDVI in different vegetation types (woodland, grassland, cultivated land, and other land) with meteorological factors at different temporal scales. The results indicated significant regional differences of NDVI in Inner Mongolia, and NDVI overall decreased from the east to the west. The woodland had the highest NDVI, followed by the cultivated land, grassland, and other land. During the study period, NDVI in Inner Mongolia exhibited an obvious recovering trend, and the decreasing order of the rate was:cultivated land > grassland > woodland > other land. In recent 15 years, the precipitation in Inner Mongolia showed an increasing trend, whereas the change in temperature was not obvious. At yearly scale, precipitation played a decisive role for the annual change in NDVI in Inner Mongolia, which meant the increase of precipitation promoted the growth of vegetation. At monthly scale, NDVI of vegetation was influenced by both precipitation and temperature. The responses of NDVI to precipitation and temperature in grassland and cultivated land all had some time lags, while those in woodland and other land merely showed time lags to temperature.
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Semantic information mining and remote sensing classification of urban functional areas
- LI Ya, LIU Yalan, REN Yuhuan, WANG Zhihao, QU Chang
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2019, 36 (1):
56-63.
DOI: 10.7523/j.issn.2095-6134.2019.01.009
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Abstract (
585 )
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As the urbanization and the policy of smart city advance step by step, new challenges are put forward for the meticulous planning of cities. It is of great significance to clarify the division of urban spatial structure and strengthen the rational planning of urban functional areas. We obtain the semantic classification results of urban functional areas using the remote sensing technology and the semantic information mining method based on the GF-1 image, POI (point of interest) data, and road network data. Firstly, extraction of construction land in study area is based on object-oriented method, and the block partition is recognized by using road network data. Considering that the semantic features from POI data make fine classification of urban construction land, we estimate POI data for each category using kernel density analysis. Then the evaluation model of function area category is established based on the overlapping regions of multiple types of kernel density. Thus the function land classification of study area is completed. 360 blocks of plots are randomly selected for sample verification test. The results show that the definition of urban function areas is accurate and the accuracy of urban function zoning is as high as 87.5%.
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Evolution of size distribution of primary schools in Nanjing City from the perspective of school system
- LIU Hongyan, CHEN Wen
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2019, 36 (1):
64-71.
DOI: 10.7523/j.issn.2095-6134.2019.01.010
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Abstract (
349 )
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Based on the spatial information and the numbers of students of primary schools in Nanjing City in the years of 1995, 2005, and 2012, we revealed the evolution of the size distribution, which was related to the number of students. Various methods, including Gini coefficient, Wolfson polarization index, kernel density estimation, Moran's index, and multiple linear regression, were used in this study. The results are given as follows.1) The average scale of schools expanded. 2) The polarization degree of size structure of the school system reduced before 2005 and then increased after 2005, with the polarization in the old city becoming increasingly prominent. 3) From 1995 to 2012, the degree of spatial concentration of students' distribution reduced and the spatial structure of students' distribution transformed from "mononuclear mass" into "multi-core scatter". 4) Driven by urban planning and the mechanism of self-organization in school system, factors, such as the location, the school quality, the original size, and school consolidation, contributed to the evolution of school-size structure and distribution. The impact of school quality has become increasingly prominent.
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Spatial-temporal evolution characteristics of decoupling relationship between industrial growth and industrial atmospheric pollution in Jilin Province
- REN Jiamin, MA Yanji
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2019, 36 (1):
72-81.
DOI: 10.7523/j.issn.2095-6134.2019.01.011
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Abstract (
392 )
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In this study, the industrial SO2 emission and soot (dust) emission were selected as two indicators of atmospheric pollution, and the space and time patterns of the decoupling relationship between industrial growth and atmospheric pollution from 2003 to 2014 in Jilin Province were evaluated based on decoupling theory. Then, a new decoupling causality chain was established to analyze the change of decoupling indexes. Finally, the evolutionary characteristic of decoupling indexes was analyzed by adopting R/S method. Conclusions are drawn as follows. During the period from 2003 to 2014, decoupling of the emission of SO2 and soot (dust) from industrial growth mainly belonged to absolute decoupling, and the proportion of absolute decoupling of industrial soot (dust) was higher than that of industrial SO2. Based on the changes of decoupling level, we divided the 9 (prefectural) cities in Jilin Province into 4 groups. The spatial evolutions of decoupling state for the two kinds of industrial pollution were different. The decoupling state in the middle of Jilin Province changed more. For soot (dust), the state of expansive negative decoupling graduately expanded toward the east from the middle, and the stress of atmospheric pollution caused by soot (dust) mainly concentrated in cities around Changchun and Songyuan. Decomposition results of decoupling indexes showed that the constraints on decoupling level improvement were different in different cities. Hurst components showed that the decoupling elasticities of industrial SO2 would decrease and the decoupling elasticities of industrial soot (dust) in different cities showed different variation trends in the meantime.
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Spatio-temporal pattern and influencing factors of urbanization development of cities at prefecture level and above in China
- YANG Zhen, LEI Jun
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2019, 36 (1):
82-92.
DOI: 10.7523/j.issn.2095-6134.2019.01.012
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Abstract (
558 )
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This study establishes a comprehensive evaluation index system for the urbanization level in prefecture cities in terms of four aspects of urbanization connotation:population, economy, society, and landscape. The spatial and temporal characteristics and the formation mechanism were analyzed systematically by using the methods including entropy, united nations, quadrant map, and geographical detector technique. The results are shown as follows. 1) Population and economy are the two dominating factors reflecting the comprehensive urbanization level, while society and landscape are the subordinate factors, which have a little effect on the comprehensive urbanization level. 2) There exist significant spatial correlation and agglomeration of comprehensive urbanization scores, and the differentiation patterns are featured by the administrative grade and the spatial agglomeration. 3) The relationships between urbanization rate and urbanization quality in prefecture-level cities can be divided into seven types. 4) There are many factors affecting prefecture-level city urbanization, including total retail sales of consumer goods, outstanding obligation, fiscal expenditure, and urban fixed asset investment. In the development of urbanization, effects of the market force and administration force have weakened. However, the effects of the financial force and exterior force have gradually enhanced.
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Automatic color correction for remote sensing optical image based on dense convolutional networks
- ZHU Sijie, LEI Bin, WU Yirong
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2019, 36 (1):
93-100.
DOI: 10.7523/j.issn.2095-6134.2019.01.013
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Abstract (
552 )
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Many effective color correction algorithms have been proposed for single remote sensing optical image. However, these methods need prior knowledge or experience which is not feasible for automatic color correction of mass remote sensing images. In this work, a method based on dense convolutional networks named DCN (dense convolutional networks) is proposed for automatic color correction for remote sensing optical images. This model predicts the color correction parameter K for each RGB channel to correct the remote sensing optical images. In our experiment, the model is trained on 3 000 crops of GF-2 remote sensing images on the Tensorflow framework and the loss function is the angle between the predicted 3-channel K and the ground truth. Results show that the corrected image is in very good agreement with the ground truth and DCN outperforms the color correction method based on traditional CNN (convolutional neural networks). This method meets the demand of automatic color correction in large remote sensing datasets.
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An improved subpixel image registration algorithm based on singular value decomposition
- LING Cheng, GENG Xiurui, YANG Weitun, ZHAO Yongchao
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2019, 36 (1):
101-108.
DOI: 10.7523/j.issn.2095-6134.2019.01.014
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Abstract (
463 )
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Phase correlation method based on singular value decomposition (SVD) is a known subpixel image registration algorithm. However, when the translation between two images to be registered is large or there is high noise, the phase unwrapping results obtained using the integral method in the registration algorithm are often unreliable. In this work, an improved phase unwrapping algorithm is proposed based on the monotonic variation of linear phase. By comparing the consistency of the adjacent phase differences and the trend slopes, the algorithm determines whether to make corrections, so as to get the real phase. Experiments on real optical images show that the proposed method effectively corrects the results obtained using the integral method, and hence increases matching accuracy.
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Inactive-node detection and memory optimization in WFST decoder lattice generation algorithm
- DING Jiawei, LIU Jia, ZHANG Weiqiang, FENG Yunbo, LIU Lijun, YU Le
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2019, 36 (1):
109-114.
DOI: 10.7523/j.issn.2095-6134.2019.01.015
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Abstract (
424 )
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Decoder is the core module of speech recognition system, and the decoder based on the weighted finite-state transducers (WFST) is a typical form of decoder. We analyze the resource occupation of WFST-based static decoder in practice, and propose a strategy for dynamical recovery of system resources by detecting inactive nodes during decoding and lattice generation. Finally, we carry out experiments on the OpenKWS 15 dataset to show that the decoder with this strategy consumes about 75% less memory than decoders that do not reclaim system resources.
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Analyzing and extracting stable feature of target backscattering for C-band SAR
- YANG Jintao, QIU Xiaolan, DING Chibiao, LEI Bin, LU Xiaojun
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2019, 36 (1):
115-124.
DOI: 10.7523/j.issn.2095-6134.2019.01.016
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Abstract (
389 )
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The absolute radiometric accuracy of synthetic aperture radar (SAR) images directly affects the quantitative applications of SAR. It is difficult to continuously monitor SAR systems using conventional calibrator-based methods. However, if a stable backscattering feature can be observed in a common scene, its value can be used as a reference to ensure the routine calibration. In this study, a scattering sample database, which includes several different categories, is built using C-band SAR images, and the analysis of the results depicts that the median center of the backscattering coefficient in urban area is relatively stable over time. Further, a neural network-based method is presented and it can be used to finely filter the urban targets and extract stable backscattering feature. This method is validated by using the test data and a contrast experiment with rainforest data. This further illustrates that the stable feature extracted using this method can be used to perform routine radiometric calibration of SAR systems.
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Attitude maneuver strategy of video mode based on agile SAR satellite
- LIANG Jian, ZHANG Running, WANG Dawei, LUO Rongzheng
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2019, 36 (1):
125-130.
DOI: 10.7523/j.issn.2095-6134.2019.01.017
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Abstract (
343 )
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As a new microwave remote sensing mode, video SAR provides a continuous surveillance over a region of interest. An implementation method of video SAR based on spotlight SAR imaging mode is proposed in this study. The segmentation method of SAR raw data and the attitude maneuver strategy for video SAR are also discussed. Rotation between consecutive frames is avoided through yaw compensation, and Euler angles and angular rates are obtained based on theoretical analysis. Finally the simulation and numeric experiments verify the feasibility of the method and strategy.
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Antioxidant properties of Au/CeO2 prepared by two different modification methods
- FA Mengmei, YAO Xin
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2019, 36 (1):
131-136.
DOI: 10.7523/j.issn.2095-6134.2019.01.018
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Abstract (
294 )
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The application of Au nanoparticles (AuNPs) modified CeO2(Au/CeO2) as an antioxidant has great potential in the field of life health, and exploring the antioxidant activities of Au/CeO2 prepared by different methods is helpful for optimizing the property of Au/CeO2. In this work, two different Au-modified CeO2 were synthesized by modifying AuNPs on the surface of CeO2 nanorods using sol-immobilized and deposition methods, respectively. The antioxidant activities of two different Au/CeO2 were studied by UV method in the MV-Fenton system, and the results showed that the antioxidant activity of Au/CeO2 by sol-immobilized method (S-Au/CeO2) was higher than that of Au/CeO2 by deposition method (D-Au/CeO2). The affecting factors on the differences between the antioxidant properties of the two Au/CeO2 were further investigated. We suppose that the surface structure of CeO2 may be damaged in the process of preparation by deposited method, which resulted in the lower antioxidant activity of D-Au/CeO2. In addition, the electron transfer between sol-immobilized AuNPs and CeO2 contributed to the higher antioxidant activity of S-Au/CeO2. These results have great significance for the functional preparation and antioxidant property regulation of Au/CeO2.
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Joint clustering and resource allocation strategy for multicast device-to-device communication underlaying cellular networks
- LI Weiqian, QIU Ling
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2019, 36 (1):
137-143.
DOI: 10.7523/j.issn.2095-6134.2019.01.019
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Abstract (
323 )
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In the scenario of multicast D2D communication underlaying a cellular network,a new optimization scheme of clustering strategy and resource allocation is proposed aiming at reducing the co-channel interference caused by channel reuse and increasing the limited capacity of multicast D2D communication caused by the worst channel quality in the cluster. We formulate the optimization problem for maximizing the total system capacity to ensure the minimum SINR for cellular and D2D users,but it is difficult to find the optimal solution. We decompose the problem into two sub-problems, power control sub-problem and clustering and channel allocation sub-problem, to find the sub-optimal solutions. Based on k-medoids clustering algorithm,a channel quality-based clustering algorithm is proposed to improve the multicast D2D capacity. Then, through the joint clustering and channel allocation strategy, the co-channel interference is reduced. Simulation shows that the proposed CQCA significantly improves the minimum throughput of multicast D2D users and results in a great improvement in the total system throughput.
where Ω⊂R3 is an open bounded domain with smooth boundary ∂Ω, 0∈Ω, a,b ≥ 0 and a+b>0, λ>0,0 < q < 1,0 ≤ s<1. The existence of its positive solutions is proved by using the variational methods.