关闭×
Welcome to Journal of University of Chinese Academy of Sciences,Today is

Current Issue

2025, Vol. 42 No. 1

Publication date

15 January 2025

Host

University of Chinese Academy of Sciences
  • Current Issue
  • Latest
  • Archive
  • Most Download
  • Most Read
  • Review Article
    Tectonic stress chemistry: a possible perspective on focal mechanism of slow earthquakes
    GUO Qianqian, SUN Jingxian, HOU Quanlin
    2025, 42 (1): 1-12.  DOI: 10.7523/j.ucas.2024.010
    Abstract ( 170 ) PDF (0KB) ( 0 )
    Research on the slow-earthquake focal mechanism was mainly based on brittle deformation. However, high ratios of P-wave to S-wave velocity, and anomalously high Poisson’s ratios indicate that the source material of slow earthquakes is more viscous and more prone to plastic deformation. Traditional studies suggest that plastic deformation begins with dislocation, and is permanent. Therefore, the plastic strain energy cannot be released. However, it may be different when talked about on a microscopic molecular scale. The lithosphere is mainly constructed of silicate minerals, especially of tetracoordinated compounds with [SiO4] tetrahedrons as fundamental units. That is, within minerals, there are chemical bonds binding various atoms together. Therefore, the dislocation mechanism of plastic deformation may first start with the change of chemical bonds, and then the chemical bonds begin to break off and rebond, forming sub-grains and grain size reduction. Mechanochemical study shows that the mechanical force can directly act on the chemical bond via stretching and rotating, change the bond length and angle, and finally break off the chemical bond. Quantum chemical calculations on molecular fragments of the crystalline structure in coal indicate that the carbon bond breaks off at high energy levels, when the hydroxyl group of the 6-membered benzene ring falls off to form CO and 5-membered rings. During plastic deformation, the energy conversion may be work done from mechanical energy by external forces firstly to internal energy as atomic potential energy, and then plastic strain energy. However, not all atomic potential energy could transform into plastic strain energy for the reconstruction of the chemical bond may release energy. As a result, a little energy may be released during the plastic deformation. Whether this is related to slow earthquakes is a scientific proposition worth exploring. It may be a possible way to explore the focal mechanism of slow earthquakes by using atomic-scale quantum chemistry calculations to establish a finer energy change process of crystal plastic deformation and comparing the source parameters of slow earthquakes.
    Research Articles
    A class of quasilinear equations with -1 powers
    ZHANG Heng, SUN Yijing
    2025, 42 (1): 13-19.  DOI: 10.7523/j.ucas.2023.006
    Abstract ( 140 ) PDF (0KB) ( 0 )
    This paper deals with quasilinear elliptic equations of singular growth like -Δu-uΔ(u2)=a(x)u-1. We establish the existence of positive solutions for general a(x)∈Lp(Ω),p>2, where Ω is a bounded domain in ℝN with N≥1.
    Learning the parameters of a class of stochastic Lotka-Volterra systems with neural networks
    WANG Zhanpeng, WANG Lijin
    2025, 42 (1): 20-25.  DOI: 10.7523/j.ucas.2023.012
    Abstract ( 214 ) PDF (0KB) ( 0 )
    In this paper, we propose a neural network approach to learn the parameters of a class of stochastic Lotka-Volterra systems. Approximations of the mean and covariance matrix of the observational variables are obtained from the Euler-Maruyama discretization of the underlying stochastic differential equations (SDEs), based on which the loss function is built. The stochastic gradient descent method is applied in the neural network training. Numerical experiments demonstrate the effectiveness of our method.
    Stochastic augmented Lagrangian method for stochastic nonconvex nonsmooth programs with many convex constraints
    ZHAO Wenshen, HAN Congying, JIN Lingzi
    2025, 42 (1): 26-42.  DOI: 10.7523/j.ucas.2023.055
    Abstract ( 226 ) PDF (0KB) ( 0 )
    The stochastic gradient methods have been widely used in machine learning, but most existing works aim for unconstrained or simple constrained problems. In this paper, we consider the nonconvex stochastic programs with many functional convex constraints. The deterministic augmented Lagrangian method is a classic algorithm for such problems, but the requirement of accurate gradient information makes the method impractical for the case with large-scale constraints. To solve such problems, we propose a novel stochastic augmented Lagrangian method, which is called CSALM(composite stochastic augmented Lagrangian method). The CSALM uses a stochastic gradient to approximate the accurate gradient, and it only samples stochastic gradients and batches constraint gradient per iteration. We establish the convergence theory of CSALM and show that the CSALM can find an $\epsilon$-KKT point after $\mathcal{O}\left(\epsilon^{-8}\right)$ iterations. The numerical experiments on the multi-class Neyman-Pearson classification problem(mNPC) demonstrate the efficiency of CSALM.
    Design of low temperature measurement experimental device based on superconductor magnetic penetration depth
    ZHU Changyang, BIAN Xing, WANG Jinzhen, LIU Jie
    2025, 42 (1): 43-49.  DOI: 10.7523/j.ucas.2023.020
    Abstract ( 243 ) PDF (0KB) ( 0 )
    The magnetic penetration depth of the external magnetic field into the superconductor varies with the temperature, especially near the superconducting transition temperature, the penetration depth changes dramatically. Detecting the change of the penetration depth can achieve high-resolution measurement of temperature changes, which is an important principle of deep and low temperature measurement. Based on this basic principle, this work studies a temperature measurement scheme using the change of superconductor penetration depth, the quantization of closed superconducting loop magnetic flux and the superconducting quantum interference device (SQUID), carries out theoretical analysis and simulation, which is expected to achieve a temperature resolution of nK/$\sqrt{\mathrm{Hz}}$ in the liquid helium temperature region, and gives the specific experimental device design. This method offers high resolution, does not introduce additional heat flow, and does not require continuous current excitation. It can greatly reduce the adverse effects of the traditional temperature measurement caused by thermometer self-heating effect and contact thermal resistance. By plating superconducting film on the surface of the object,which is beneficial to temperature measurement experiments and applications below 10 K.
    Characteristics of high technology manufacturing industry migration based on micro enterprise data: a case study of Beijing metropolitan area
    ZHANG Peiyuan, LI Jiaming, ZHANG Wenzhong
    2025, 42 (1): 50-60.  DOI: 10.7523/j.ucas.2023.047
    Abstract ( 166 ) PDF (0KB) ( 0 )
    This study traces the migration process of key high-tech enterprises in Beijing during 2008-2016, revealing the migration characteristics and patterns of high-tech enterprises within the metropolitan area. The results show that medium-sized enterprises are more likely to relocate than small and large enterprises, especially in lucrative sectors. Moreover, migration is mainly within agglomerations, with relatively little migration across agglomerations and between agglomerations and non-agglomerations, although this varies between agglomerations. Finally, most high-tech manufacturing firms first relocate between 7 and 16 years after their establishment, which means that there is roughly a 7-year adaptation or development period for firms in a region after their establishment. During the adaptation period, companies do not tend to relocate, after which, as they grow, they need to find new spaces to grow. For reasons such as familiarity with the environment, enterprises give priority to finding new locations within the agglomeration and the surrounding area.
    Basin ecological restoration zoning and land use simulation evaluation based on multivariate coupling model: a case study of Dianchi Lake Basin
    WANG Jiaheng, YAN Wei, DUAN Xuejun, DUAN Yanyan, LI Zhuona, ZOU Hui
    2025, 42 (1): 61-73.  DOI: 10.7523/j.ucas.2023.039
    Abstract ( 119 ) PDF (0KB) ( 0 )
    Scientific delineation of watershed ecological restoration zones and simulation of land use scenarios in each zone can provide important support for the design of land space-related planning schemes such as watershed ecological restoration, ecological risk avoidance and land use index formulation. Taking the Dianchi Lake Basin as an example, this paper identified the ecological restoration zones of the Dianchi Lake Basin and conducted land use simulations under different scenarios based on the ecosystem service value and ecological risk calculation model, PLUS model, GIS analysis and other methods. The results showed that: 1) From 2000 to 2020, the ecosystem service value in the Dianchi Lake Basin decreased from 20.614 billion RMB to 19.271 billion RMB, and the proportion of areas with high ecological risk and above increased from 6.24% to 19.30%; 2) The spatial distribution of ecological restoration zones in the Dianchi Lake Basin was a circular structure. From the center of Lake Dianchi to the outside, ecological restoration zones were divided into 4 categories: the core area of ecological restoration, the important area of ecological restoration, the green development area and the ecological restoration and conservation area. The occupied area was 362.09, 109.99, 791.92, and 1 590.89 km2, respectively; 3) Under the natural development scenario in 2030, the construction land in the Dianchi Lake Basin would increase by 189.92 km2; under the ecological restoration scenario, the construction land would increase by 53.75 km2, and the urban expansion rate would slow down. The ecological restoration scenario had an additional ecosystem service value of 434 million RMB in the Dianchi Lake Basin compared with the natural development scenario.
    Response of glacial isostatic adjustment (GIA) in Patagonia, South America based on hydrological and GRACE gravity data
    LI Mengyu, SUN Pengchao, GUO Changsheng, WANG Changyu, WEI Dongping
    2025, 42 (1): 74-85.  DOI: 10.7523/j.ucas.2024.005
    Abstract ( 71 ) PDF (0KB) ( 0 )
    The Patagonia Plateau in South America is located in a complex tectonic area where the large ice sheets in the temperate zone are melting rapidly and the oceanic plate is subducting into the continental plate. The signal of glacial isostatic adjustment (GIA) and the mechanism of surface uplift in this area need to be further investigated. Based on the time-variable gravity data of gravity recovery and climate experiment (GRACE), this paper analyzes the characteristics of mass trends in the plateau from 2003 to 2016. Relevant hydrological models and remote sensing satellite data are used to improve the combined hydrological model of this region and extract the spatial variation characteristics of its hydrological information. The current GIA signals are obtained by deducting hydrologic signals from the integrated GRACE signals. The contribution of GIA effect to land surface uplift is analyzed using global positioning system (GPS) data. The results show mass loss in and around Patagonia Icefield (PIF) and mass increase in the south and north of the Patagonia Plateau. The hydrologic mass loss forms a spatial distribution with PIF as the center and the negative signal gradually weakening. The GIA response causes the plateau uplift and is most significant in the southern part of PIF, reaching a maximum of (1.97±0.35) cm/a. The GIA signal is similar to the GIA model. The GIA signals can interpret about 69.25% and 82.70% of GPS vertical speed signals in Northern Patagonia Icefield (NPI) and Southern Patagonia Icefield (SPI), respectively.
    Organic mineralization in lead-zinc deposits: a case study of the Jinding lead-zinc deposit, Lanping Basin
    HOU Xingao, JU Yiwen, FENG Hongye, XIAO Lei, QIAO Peng, TAO Liru, WANG Peng, WANG Wei, GAO Jian
    2025, 42 (1): 86-106.  DOI: 10.7523/j.ucas.2024.016
    Abstract ( 148 ) PDF (0KB) ( 0 )
    A large amount of organic matter (OM) is associated with ore bodies in the Jinding lead-zinc deposit, Lanping Basin, the northwestern Yunnan Province, but the way and process of OM participation in lead-zinc mineralization remain controversial. OM in the deposit has generally undergone biodegradation, and much of it still contains detectable compounds such as n-alkanes, isoprenoids, naphthalene, phenanthrene, and biphenyl. A small portion of OM does not contain n-alkanes and isoprenoids but shows the characteristics of initial degradation of steranes while no 25-norhopane is generated, which is generally in line with the characteristics of grade 2-5 biodegradation, consistent with the bacterial sulfate reduction (BSR). No significant correlation is observed between the δ13CPDB and δ18OPDB values of calcites, and their distribution patterns of REEs, Y/Ho values, and Sr contents are also inconsistent with the characteristics of thermochemical sulfate reduction (TSR) calcites. The δ13CPDB values (~-27‰) of bitumen in the deposit are not less than those of source rocks (estimated value), so it is reasonable to infer that TSR is not the main way for OM to participate in the lead-zinc mineralization. The estimation results of δ34S show that the δ34S of H2S generated by the thermal decomposition of OM is from -5‰ to 0, which is consistent with the range of heavy sulfur isotope peaks (-8‰~-2‰) in the δ34S value histogram of metal sulfides in the deposit. Based on mineralization characteristics, if one-third of the lead-zinc ore is related to the thermal decomposition of OM, and the sulfur content of crude oil in the paleo reservoir is 1.5%, the amount of crude oil required for mineralization is calculated to be about 96.87 million tons, which is not contradictory to geological facts. Therefore, we propose that OM was mainly involved in lead-zinc mineralization through BSR in the formation stage of paleo reservoirs and thermal decomposition of OM in the high-temperature mineralization stage, while large-scale TSR might not occur.
    Remote sensing semantic segmentation method based on high-resolution relational graph convolutional network
    WANG Yinda, CHEN Jiahui, PENG Ling, LI Zhaobo, YANG Lina
    2025, 42 (1): 107-115.  DOI: 10.7523/j.ucas.2023.079
    Abstract ( 296 ) PDF (0KB) ( 0 )
    Semantic segmentation of remote sensing images is an important task in remote sensing image processing and analysis, especially in multi-category semantic segmentation. Current methods mainly revolve around convolutional neural networks, but convolution only focuses on the local information of the image while ignoring the global information. Therefore, inspired by high resolution network (HRNet) and relational graph convolutional network (R-GCN), this paper proposes a high-resolution relational graph convolutional network (HRGCN) for multi-category semantic segmentation. Firstly, simple linear iterative clustering (SLIC) is done on the original image, and the result is used to segment the feature map output from HRNet to obtain superpixel blocks with high homogeneity and containing multi-resolution information; then graph nodes and edges are constructed based on the superpixel blocks, and R-GCN is used to classify the graph nodes, so as to learn the long-distance dependency between different features and complete the extraction and classification of remote sensing images. The HRGCN model designed in this paper is experimented on Potsdam and Vaihingen datasets, and the results are compared with the existing methods, and the $\bar{F}_1$ values and MIoU values are improved to certain degrees, which proves that the method has good advancement.
    Shallow subsurface structure of the Utopia Planitia based on Zhurong rover penetrating radar data
    YANG Jiaqi, SHAO Yun, BIAN Xiaolin, ZHANG Tingting, WANG Guojun
    2025, 42 (1): 116-125.  DOI: 10.7523/j.ucas.2023.030
    Abstract ( 228 ) PDF (0KB) ( 0 )
    Mars subsurface exploration is essential to obtain information on the historical evolution of Mars and to search for possible living environments on Mars. The rover penetrating radar (RoPeR) on board Zhurong, the rover of China’s first Mars exploration mission, is used to detect the subsurface structure of Utopia Planitia. In this paper, high-frequency channel data of RoPeR are selected to obtain the shallow subsurface information of Utopia Planitia. This study includes 1) subsurface structure modeling of the landing area and numerical simulation of shallow subsurface echo based on the finite-difference time-domain (FDTD) algorithm; 2) processing the high-frequency channel data of RoPeR; 3) interpreting the shallow subsurface structure of Utopia Planitia. The study results validate the ability of RoPeR to detect shallow subsurface structure. There is a 10-20 cm duricrust at the surface of the Zhurong landing area. Under the duricrust are loose weathering material and randomly distributed gravels, which gradually transition to the middle Amazonian sedimentary sequence with increasing depth. There are strong echo signals in the radar image of Sol 101, which are presumed to be related to recent meteorite activity. The results of the study initially reveal the shallow subsurface structure of Utopia Planitia, which is a good reference for the situ probing and sampling experiments of the subsequent Mars exploration missions.
    Ultra-reliable low-latency edge computing architecture for 6G
    DING Yuhua, CHEN Li, WEI Guo
    2025, 42 (1): 126-133.  DOI: 10.7523/j.ucas.2023.029
    Abstract ( 206 ) PDF (0KB) ( 0 )
    MEC (mobile edge computing) is the supporting technology for the 6G mobile communication network to connect communication and service and realize the smart connection of everything. For the computational delay optimization of the MEC system, a horizontal multi-host architecture is proposed and a complete signaling flow is designed. For the transmission delay optimization of the MEC system and the straggler problem of multi-host parallel computation, a master-slave architecture of multi-connectivity is proposed and a complete signaling flow is designed. For the evaluation of MEC system performance, a multi-host MEC simulation platform based on the open-source libraries is built. The experiments show that the horizontal multi-host MEC architecture effectively improves computational latency performance; the proposed master-slave MEC architecture of multi-connectivity effectively alleviates the straggler problem and improves transmission latency performance; the built MEC simulation platform can effectively evaluate the key performance indicators of the multi-host architecture.
    Brief Report
    Public participation, environmental regulation, and residents' well-being: a bibliometric analysis based on CiteSpace
    ZOU Yurou, LIU Hong, LYU Chen
    2025, 42 (1): 134-144.  DOI: 10.7523/j.ucas.2023.080
    Abstract ( 248 ) PDF (0KB) ( 0 )
    The research on the relationship between public participation, environmental regulation and residents’ well-being is of great significance for the scientific formulation of environmental regulation policies and the optimization of the governance environment. Using the data of journal papers collected by Web of Science and CNKI from 2006 to 2021, using CiteSpace bibliometric analysis software and combining with traditional review methods, this paper draws the following conclusions: 1) Chinese literature research hotspots have gone through three stages: the western experience discussion of public participation in environmental governance and the initial stage in China, the theoretical model analysis of public participation in environmental governance and the empirical research stage of influencing factors, the evaluation of residents’ well-being effect of environmental regulation and the specific case study of public participation in environmental regulation. English literature research initially focused on the participation of residents at the community level in environmental regulation, and then focused on the exploration of problems and influencing factors in practice. At present, it focuses on the impact of environmental regulation on residents’ well-being and environmental health inequity and big data analysis applications; 2) The academic community has not yet reached a consistent conclusion on the impact of public participation in environmental regulation and residents’ well-being. The study confirms that environmental regulation has a positive impact on residents’ health and enhances individual subjective well-being, but at the same time it exacerbates the income gap between residents and between regions; 3) The research trend shows that the research perspective changes from macro to micro, the research method changes from statistical model to spatial analysis and quasi-natural experiment method, and the variable measurement changes from single index to comprehensive index; 4) Future research needs to focus on the analysis and optimization of government response mechanism, the research on the equity of environmental regulations on residents’ well-being, and the improvement and perfection of research methods, data, and variable measurement methods.
2024, Vol.41 No.6  No.5 No.4 No.3 No.2 No.1
2023, Vol.40 No.6  No.5 No.4 No.3 No.2 No.1
2022, Vol.39 No.6  No.5 No.4 No.3 No.2 No.1
2021, Vol.38 No.6  No.5 No.4 No.3 No.2 No.1
2020, Vol.37 No.6  No.5 No.4 No.3 No.2 No.1
2019, Vol.36 No.6  No.5 No.4 No.3 No.2 No.1
2018, Vol.35 No.6  No.5 No.4 No.3 No.2 No.1
2017, Vol.34 No.6  No.5 No.4 No.3 No.2 No.1
2016, Vol.33 No.6  No.5 No.4 No.3 No.2 No.1
2015, Vol.32 No.6  No.5 No.4 No.3 No.2 No.1
2014, Vol.31 No.6  No.5 No.4 No.3 No.2 No.1
2013, Vol.30 No.6  No.5 No.4 No.3 No.2 No.1
2012, Vol.29 No.6  No.5 No.4 No.3 No.2 No.1
2011, Vol.28 No.6  No.5 No.4 No.3 No.2 No.1
  • Please wait a minute...
    For Selected: Toggle Thumbnails
    Analysis of Shanghai and Shenzhen stock market using Copula-VaR method
    Hao Li-Xiang, Cheng Xi-Jun
    Journal of University of Chinese Academy of Sciences    2008, 25 (5): 682-686.   DOI: 10.7523/j.issn.2095-6134.2008.5.017
    Abstract1609)      PDF(pc) (727KB)(17358)       Save
    Risk analysis of Portfolio is studied ,by comparing Copula functions and the traditional VaR methods,mixing copula is made. By backtesting ,the empirical research shows that mixing Copula method makes better VaR model .
    Related Articles | Metrics | Comments0
    Shape-dependent effects of nanoceria on the activity of Pd/CeO2 catalysts for CO oxidation
    WANG Lei, MAO Junyi, YUAN Qing, HUANG Tao
       2015, 32 (5): 594-604.   DOI: 10.7523/j.issn.2095-6134.2015.05.004
    Abstract613)      PDF(pc) (9359KB)(15157)       Save

    The redox property of palladium nanoparticles (NPs) is pivotal to CeO2 supported Pd catalysts in oxidation reactions and is closely related to the structure of Pd-CeO2 interface. Herein, we report that low-temperature CO oxidation activity of Pd/CeO2 highly depends on the shape and crystal plane of CeO2 supports. Pd/CeO2 catalysts with CeO2 nanoocthedrons (NOCs) and nanocubes (NCs) as supports were prepared by colloidal-deposition method. Results show that Pd/CeO2 NOCs with ceria {111} facets enclosed exhibited much higher catalytic activity than Pd/CeO2NCs with ceria {100} facets exposed. DFT calculations revealed that the redox property of surface Pd species may play important roles in determining the reducibility and activity of catalysts. The PdOx to Pd cycle is more facile on Pd4@CeO2(111) than on Pd4@CeO2(100), which is dictated by the Pd-ceria interaction in the end. Our results show that the redox property of surface Pd is pivotal to the reducibility and activity of Pd/ceria catalysts, which could be tuned by manipulation of the Pd-CeO2 interaction via tuning the exposed facets of ceria support.

    Reference | Related Articles | Metrics | Comments0
    Advances in light field photography technique
    NIE Yun-Feng, XIANGLI Bin, ZHOU Zhi-Liang
       2011, 28 (5): 563-572.   DOI: 10.7523/j.issn.2095-6134.2011.5.001
    Abstract3291)      PDF(pc) (1045KB)(6673)       Save

    Light field is a representation of full four-dimensional radiance of all rays with spatial and angular information in free space, and capture of light field data enables many new development potentials for computational imaging. The historical development of light field photography is summarized, and typical light field photography devices are categorized in view of capture methods for 4D light field. Based on the principles of light field camera, computational imaging theorem, refocusing theory, synthetic aperture refocusing algorithm, and light field microscopic technology are emphatically described. Finally, the promising application perspectives and existing critical issues of light field imaging are discussed.

    Reference | Related Articles | Metrics | Comments0
    Upstream promoter sequences of Arabidopsis GH3 gene family
    SUN Tao, CHAI Tuan-Yao, ZHANG Yu-Xiu
       2010, 27 (6): 847-852.   DOI: 10.7523/j.issn.2095-6134.2010.6.017
    Abstract2435)      PDF(pc) (154KB)(6282)       Save

    GH3 genes belong to a primary auxin-response gene family. The 10 promoter sequences of Arabidopsis GH3 genes were analyzed using bioinformatics method. The results show that the transcription start site of these genes is generally 65~145bp away from the start codon, and the TATA boxes are located in the (-24)-(-40)bp. MDB and MatInspector analyses show that most upstream regions of these GH3 genes contain the cis-elements required for tissue and organ-specific expression responding to phytohormones and external environment, indicating that the expressions of GH3 genes are strictly controlled by multi-factors. Gene chip data show that AuxREs is very important for GH3 genes in response to IAA treatment,but it is not the unique cis-element for auxin response.

    Reference | Related Articles | Metrics | Comments0
    Quality Evaluation for Three Textual Document Clustering Algorithms
    LIU Wu-Hua, LUO Tie-Jian, WANG Wen-Jie
       2006, 23 (5): 640-646.   DOI: 10.7523/j.issn.2095-6134.2006.5.012
    Abstract2891)      PDF(pc) (832KB)(5694)       Save
    Textual document clustering is one of the effective approaches to establish a classification instance of huge textual document set. Clustering Validation or Quality Evaluation techniques can be used to assess the efficiency and effective of a clustering algorithm. This paper presents the quality evaluation criterions from outer and inner. Based on these criterions we take three typical textual document clustering algorithms for assessment with experiments. The comparison results show that STC(Suffix Tree Clustering) algorithm is better than k-Means and Ant-Based clustering algorithms. The better performance of STC algorithm comes from that it takes accounts the linguistic property when processing the documents. Ant-Based clustering algorithm’s performance variation is affected by the input variables. It is necessary to adopt linguistic properties to improve the Ant-Based text clustering’s performance.
    Related Articles | Metrics | Comments0
    Investigation on the Preparation of μ-Sized PMMA Microspheres by the Dispersion Polymerization
    WU Shao-Gui, LIU Bai-Ling
       2006, 23 (3): 323-330.   DOI: 10.7523/j.issn.2095-6134.2006.3.007
    Abstract2333)      PDF(pc) (1120KB)(5303)       Save
    The micron-grade PMMA microspheres with narrow size distribution were prepared by dispersion polymerization. The mechanism of the dispersion polymerization was discussed. The factors influencing both the size and size distribution of the microspheres including initial concentrations of the initiator, monomer, stabilizer, the polarity of the medium and the reaction conditions were studied. The results indicated that the size and size distribution of microspheres both increased with initial concentrations of initiator and monomer. Increasing the amount of the stabilizer resulted in decreasing size and narrowing size distribution of microspheres. Other factors such as the polarity of medium and the reaction temperature had great influences too. By controlling these factors, the desired-size monodisperse microspheres could be obtained.
    Related Articles | Metrics | Comments0
    SA-DBSCAN:A self-adaptive density-based clustering algorithm
    XIA Lu-Ning, JING Ji-Wu
       2009, 26 (4): 530-538.   DOI: 10.7523/j.issn.2095-6134.2009.4.015
    Abstract3482)      PDF(pc) (268KB)(4737)       Save

    DBSCAN is a classic density-based clustering algorithm. It can automatically determine the number of clusters and treat clusters of arbitrary shapes. In the clustering process of DBSCAN, two parameters, Eps and minPts,have to be specified by uses. In this paper an adaptive algorithm named SA-DBSCAN was introduced to determine the two parameters automatically via analysis of the statistical characteristics of the dataset, which enabled clustering process of DBSCAN fully automated. Experimental results indicate that SA-DBSCAN can select appropriate parameters and gain a rather high validity of clustering.

    Reference | Related Articles | Metrics | Comments0
    A block Gram-Schmidt algorithm with its application
    ZHAO Tao, JIANG Jin-Rong
       2009, 26 (2): 224-229.   DOI: 10.7523/j.issn.2095-6134.2009.2.011
    Abstract2871)      PDF(pc) (820KB)(4490)       Save

    Gram-Schmidt algorithm is one of the fundamental methods in linear algebra, which is mainly used to compute QR decomposition. The classical and modified Gram-Schmidt are both based on level 1 or level 2 BLAS operations which have low cache reuse. In this paper, a new block Gram-Schmidt algorithm is proposed. The new algorithm ensures the orthogonality of resulting matrix Q is close to machine precision and improves performance because of using level 3 BLAS. Numerical experiments confirm the favorable numerical stability of the new algorithm and its effectiveness on modern computers.

    Reference | Related Articles | Metrics | Comments0
    Software protection method based on self-modification mechanism
    WANG Xiang-Gen, SI Duan-Feng, FENG Deng-Guo, SU Pu-Rui
       2009, 26 (5): 688-694.   DOI: 10.7523/j.issn.2095-6134.2009.5.015
    Abstract1694)      PDF(pc) (173KB)(4236)       Save

    In this paper, we present a new method based on self-modification mechanism to protect softwares against illegal acts of hacking. The key idea is to converse key codes into data in the original program so as to make programs harder to analyze correctly. Then, we translate data to executable codes by enabling the virtual memory page which stores the hidden code to be executable at run-time. Our experiments demonstrate that the method is practical and efficient.

    Reference | Related Articles | Metrics | Comments0
    Design of high resolution camera system based on full frame CCDs
    LIU Guang-Lin, YANG Shi-Hong, WU Qin-Zhang, XIA Mo
       2007, 24 (3): 320-324.   DOI: 10.7523/j.issn.2095-6134.2007.3.008
    Abstract2574)      PDF(pc) (1138KB)(4168)       Save
    A design of high resolution camera system based on DALSA’ s CCD evaluation kit EKxxxx was presented. It was composed of a pulse pattern generator (SAA8103), a vertical line driver (TDA9991), four analog-to-digital interfaces (TDA9965) and a system controller (P89LV51RD2). Camera link with medium configuration was adopted to transfer digital images. The software for controlling and debugging the camera was developed. To correct the non-uniformity of 4 outputs, a method based on two-point correction was described. The system can acquire ultra high resolution pictures at a high frame rate thus it is suitable for aero photography.
    Related Articles | Metrics | Comments0
    Recent Advances in the Biodegradability of PVA and its Derivative Material
    ZHANG Hui-Zhen, LIU Bai-Ling, LUO Rong
       2005, 22 (6): 657-666.   DOI: 10.7523/j.issn.2095-6134.2005.6.001
    Abstract929)      PDF(pc) (1257KB)(4119)       Save

    Poly (vinyl alcohol) (PVA) and its derivatives,the excellent water-soluble polymers,have attracted more and more attention,as they show the usability in many processes,as well as possess the promise of degradation in the presence of some specific microbials.In the present paper,the recent advances in the biodegradation of PVA and its derivatives,including the mechanism,influential factors,evaluation method and degradation environment etc,have been reviewed.Moreover,the latest development of PVA-based blendsPcomposites and their biodegradation is also introduced in the present article.

    Reference | Related Articles | Metrics | Comments0
    Heavy metals in aerosol in China: pollution, sources,and control strategies
    TAN Ji-Hua, DUAN Jing-Chun
       2013, 30 (2): 145-155.   DOI: 10.7523/j.issn.1002-1175.2013.02.001
    Abstract3830)      PDF(pc) (1395KB)(3987)       Save

    In recent years, the heavy metal pollution incidents in China were frequently reported. However, studies on pollution, sources, and control strategies of atmospheric heavy metals in China are rare. We summarize the research results reported in recent years. The features of pollution level, seasonal variation, regional differences, size distribution of the atmospheric heavy metal elements including Pb, V, As, Mn, Ni, Cr, and Cd in China are analyzed. The main sources, current control status, and control technologies of atmospheric heavy metals are discussed. Comprehensive suggestions for China's heavy metal pollution control are put forward based on the summarization of the progress and experience of the atmospheric heavy metal pollution control in other countries and regions.

    Reference | Related Articles | Metrics | Comments0
    Experiment and numerical simulation of thermal conductivity of uranium dioxide
    WANG Zeng-Hui, HUANG Xiao-Feng
       2009, 26 (3): 415-418.   DOI: 10.7523/j.issn.2095-6134.2009.3.017
    Abstract2540)      PDF(pc) (929KB)(3882)       Save

    Uranium dioxide is a kind of steady nuclear fuel that has the characteristic of high melting point and steady property. The thermal conductivity of uranium dioxide can directly influence the temperature distribution of nuclear fuel and the max temperature of the center of nuclear fuel. The experimental results and expression of thermal conductivity have been compared in the paper. The deviation between the experiment results has decreased. The non-equilibrium molecular dynamics simulation results are in good agreement with the experiment results in medium temperature region. In low temperature region, it is necessary to add the quantum correction to the kinetic energy computation of phonon. In high temperature region, it is needed to use the accurate potential model and build up the electron gas energy transport model and photon radiation energy transport to study the thermal conductivity well and truly for the nuclear reactor safety design and uranium dioxide engineering application.

    Reference | Related Articles | Metrics | Comments0
    A CMOS high performance 50MSPS sample/hold circuit
    LI Tie, GUO Li, BAI Xue-fei
       2007, 24 (6): 788-793.   DOI: 10.7523/j.issn.2095-6134.2007.6.010
    Abstract2703)      PDF(pc) (1540KB)(3856)       Save
    A high performance CMOS sample/hold circuit is presented, which achieves the precision of 10-bit over Nyquist band in 50-MHz sampling frequency at 3.3-V supply. This circuit uses full differential circuits, bottom-plate sampling, bootstrap circuits and high performance gain-boost operational amplifier. Simulation in 0.35-μm CMOS process shows the circuit consumes 18-mW of power.
    Related Articles | Metrics | Comments0
    An easy-to-deploy behavior monitoring scheme for Android applications
    WANG Xueqiang, LEI Lingguang, WANG Yuewu
       2015, 32 (5): 689-694.   DOI: 10.7523/j.issn.2095-6134.2015.05.016
    Abstract1117)      PDF(pc) (1223KB)(3790)       Save

    Malicious applications pose tremendous threats to Android platform. More than 90% of malicious codes are introduced in the form of Android apps. Hence, behavior monitoring scheme for Android applications are required in order to resolve the problem. However, most of the schemes are based on system customization and hard to deploy on devices for Android's fragmentation problem. In this paper, an easy-to-deploy Android application monitoring method on the basis of process hijacking is proposed after analysis of Android process model and code execution details. The method depends on Dalvik interpreter entry point and system call interception. The authors created a fully usable prototype of the system, and the evaluation results show that the system is easy to deploy, provides a whole-scale behavior of Android applications, and incurs little performance overhead.

    Reference | Related Articles | Metrics | Comments0
    Rice Varietal Improvement and Rice Production in China
    LI Hai-Ming
       2007, 24 (1): 1-8.   DOI: 10.7523/j.issn.2095-6134.2007.1.001
    Abstract1933)      PDF(pc) (832KB)(3630)       Save
    The specific objective of the study is to analyse the adoption of improved varieties and the changes in characteristics of varieties across China. It also estimates the contribution of varietal improvement to rice production in China. The results indicated that the story of rice improvement over the past 50 years stood as an enormous success. Nearly 30% of the net gain in rice production came from varietal improvement. Compared with the beginning of 1980s, the numbers of released varieties have been improved by 1. 5 times, the share of total rice area planted to varieties with resistances has increased 10%, and the planting area of high-quality varieties has increased 50%. However, the declining contribution of varietal improvement since 1997 pointed out that government should encourage breeders to explore elite germplasm, improve breeding level, and break through yield stagnates so that varietal improvement can contribute greater to rice production.
    Related Articles | Metrics | Comments0
    Optimized Regulation Model of Human-Earth System Based on System Dynamics
    CHENG Ye-Qing
       2006, 23 (1): 83-90.   DOI: 10.7523/j.issn.2095-6134.2006.1.016
    Abstract2150)      PDF(pc) (816KB)(3615)       Save
    study of human-earth system is the most important content in geography; regional sustainable development relies on the reasonable structure optimal model and effective regulation of regional human-earth system. County region is a complex and opening human-earth system, taking Huangling county as an example, the environment, resources exploitation, economic development and structure evolvement of industry were systematically analyzed. And the systematical dynamic model was established and multi-projects were simulated with the theory and method of system dynamic. Optimized regulation models of human-earth system evolvement were educed based on three projects: (1) Traditional evolvement method. The intensity of resource exploitation and environment pollution is the least, but the speed of its economy development is the lowest, which restrict social sustainable development and economic reproduction. (2) Economy development method. The intensity of resource exploitation and environment pollution is the worst, economic development mostly depends on higher investment and pollution, which is a traditional mode of unsustainable development. (3) Harmonious development mode. The mode considers not only economic sustainable development and natural recourses utilizing reasonably, but also gives more attention to environment protection and harmonious development of industry, agriculture, tourism and so on. It is the optimized mode of the human-earth system evolvement.
    Related Articles | Metrics | Comments0
    An Improved K-means Algorithm Based on Optimizing Initial Points
    QIN Yu, JING Ji-Wu, XIANG Ji, ZHANG Ai-Hua
       2007, 24 (6): 771-777.   DOI: 10.7523/j.issn.2095-6134.2007.6.008
    Abstract2759)      PDF(pc) (833KB)(3455)       Save
    K-means is an important clustering algorithm. It is widely used in Internet information processing technologies. Because the procedure terminates at a local optimum, K-means is sensitive to initial starting condition. An improved algorithm is proposed, which searches for the relative density parts of the database and then generates initial points based on them. The method can achieve higher clustering accuracies by well excluding the effects of edge points and outliers, as well as adapt to databases which have very skewed density distributions.
    Related Articles | Metrics | Comments0
    Spectrophotometric determination of polyphenols in Quercus mongolicus Fisch leaves by means of Folin-ciocalteu reagent
    ZHANG Guo-You, TANG Ling, CHEN Wei, HE Xing-Yuan, HUANG Wei
       2009, 26 (3): 319-322.   DOI: 10.7523/j.issn.2095-6134.2009.3.005
    Abstract1962)      PDF(pc) (152KB)(3417)       Save

    The total polyphenols(TP)content of Quercus mongolicus Fisch leaves extracts was analyzed by Folin-ciocalteu colorimetry,with gallic acid as standard.The method was improved and verified in the aspects of stability, linearity,precision and accuracy.The results showed that the total polyphenols content of Quercus mongolicus Fisch leaves extracts could be well calculated according to their colorimetric absorption at 760nm by applying Folin-ciocalteu reagent (1mol/L) 0.15mL and 10% volume fraction of Na2CO3 0.15mL at 25℃ for 80min. The (TP)content in Quercus mongolicus Fisch leaves determinated by the method was 6.39% and RSD was 1.90%.

    Reference | Related Articles | Metrics | Comments0
    The Research Progress in Synthesis and Application of Gallium Nitride2Based Materials
    PENG Bi-Xian, QIAN Hai-Sheng, YUE Jun, CHEN Li-Juan, WANG Chong-Chen, ZHANG Li-Juan
       2005, 22 (5): 536-544.   DOI: 10.7523/j.issn.2095-6134.2005.5.002
    Abstract560)      PDF(pc) (574KB)(3401)       Save

    Gallium nitride is a novel kind of semiconductor,whose direct band gap is 3139eV at the room temperature. It has been proved to be a promising material for electronic and photoelectric devices. A good many of its growth methods have been discovered, and some of them had been implemented in production practice with monitoring systems. Some comparisons were made between different methods. The structure-performance dependence of GaN itself, GaN-based family and multinitrides have been summarized. The main fields of GaN-based material were presented. GaN-based material is being considered to be the excellent candidate of electronic device potentially used in high temperature,high-power and worst environment surroundings.

    Reference | Related Articles | Metrics | Comments0
  • Please wait a minute...
    For Selected: Toggle Thumbnails
    Allometric equation and biomass estimation of Eucalyptus in Fujian
    ZHENG Xiaoman, WENG Xian, OU Linglong, REN Yin
    Journal of University of Chinese Academy of Sciences    2024, 41 (3): 321-333.   DOI: 10.7523/j.ucas.2022.074
    Abstract739)      PDF(pc) (10322KB)(782)       Save
    The estimation of forest biomass at individual tree scale is the basis for the estimation of forest biomass at the regional scale. This paper aims at developing a reliable and effective allometric equation for Eucalyptus in Fujian in order to improve the estimation accuracy of Eucalyptus biomass in this area and to provide basic supporting data for the sustainable forestry development of Eucalyptus. This study takes Eucalyptus, a major fast-growing and productive tree species in Southern China, as the research object. Using 90 Eucalyptus woods harvested in the field, the partitioning of Eucalyptus biomass among organs are studied, the optimal allometric equations are constructed, and the Eucalyptus root/shoot ratios are calculated and applied to estimate Eucalyptus root biomass. Results show Eucalyptus has the following biomass allocation strategies: the biomass proportion of trunks increases with increasing stand age, while that of branches, leaves, and roots decreases. The most feasible and effective way to estimate Eucalyptus root biomass is to use root/shoot ratio data with stand age. In the construction of the allometric equation for Eucalyptus biomass, the multiplicative power equation is better than the linear equation, and the optimal independent variable varied by organ type. This paper provides data and theoretical support for the accurate estimation of Eucalyptus plantation biomass, and has implications for species growth patterns, survival strategies, and even forest ecological management.
    Reference | Related Articles | Metrics | Comments0
    Solving quadratic assignment problem based on actor-critic framework
    LI Xueyuan, HAN Congying
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 275-284.   DOI: 10.7523/j.ucas.2022.031
    Abstract735)      PDF(pc) (4937KB)(1921)       Save
    The quadratic assignment problem (QAP) is one of the NP-hard combinatorial optimization problems and is known for its diverse applications in real life. The current relatively mature heuristic algorithms are usually problem-oriented to design customized algorithms and lack the ability to transfer and generalize. In order to provide a unified QAP solution strategy, this paper abstracts the flow matrix and distance matrix of QAP problem into two undirected complete graphs and constructs corresponding correlation graphs, thus transforming the assignment task of facilities and locations into node selection task on the association graph. Based on actor-critic framework, this paper proposes a new algorithm ACQAP(actor-critic for QAP). Firstly, the model uses a multi-headed attention mechanism to construct a policy network to process the node representation vectors from the graph convolutional neural network; Then, the actor-critic algorithm is used to predict the probability of each node being output as the optimal node. Finally, the model outputs an action decision sequence that satisfies the objective reward function within a feasible time. The algorithm is free from manual design and is more flexible and reliable as it is applicable to different sizes of inputs. The experimental results show that on QAPLIB instances, the algorithm has stronger transfer and generalization ability under the premise that the accuracy is comparable to the traditional heuristic algorithm, while the assignment cost for solving is less compared to the latest learning-based algorithms such as NGM, and the deviation is less than 20% in most instances.
    Reference | Related Articles | Metrics | Comments0
    Spatial and temporal distribution characteristics and influential factors of PM2.5 pollution in Beijing-Tianjin-Hebei
    SU Mengqian, SHI Yusheng
    Journal of University of Chinese Academy of Sciences    2024, 41 (3): 334-344.   DOI: 10.7523/j.ucas.2023.025
    Abstract659)      PDF(pc) (6043KB)(1119)       Save
    The fine particulate matter PM2.5 could be harmful to human health and the atmospheric environment. Beijing-Tianjin-Hebei is one of the most serious regions in China in terms of atmospheric PM2.5 pollution. Based on PM2.5 concentrations data, natural factors data, and human activity factors data, this study used kriging interpolation and statistical analysis to explore the spatial and temporal distribution characteristics of atmospheric PM2.5 pollution in 13 cities of Beijing-Tianjin-Hebei in 2017 and then used correlation analysis models and factor analysis models to explore its influential factors. The results show that in Beijing-Tianjin-Hebei, 1) PM2.5 concentrations are low in the north and high in the south. The gradient of annual average concentrations between the southern and northern cities can reach up to 64μg/m3. 2) PM2.5 concentrations are high in winter and low in summer, high in the morning and evening, and low in the afternoon. PM2.5 concentration in winter is 1.3-2.8 times higher than in summer, and the daily differences in PM2.5 concentrations in all seasons are between 11-29μg/m3. 3) Atmospheric PM2.5 pollution is closely related to natural factors. Terrain and topography affect the processes of PM2.5 aggregation, transport, and dispersion. Wind speed, sunshine hours, and relative humidity are the dominant meteorological factors affecting atmospheric PM2.5 pollution, and PM2.5 concentrations have the strongest correlation with meteorological factors in winter. 4) Atmospheric PM2.5 pollution is closely related to human activities, which can be summarized into social economy factor, industrial pollutant discharge factor, and urban construction factor. The results of this study will help fill the gaps in air pollution prevention and control in Beijing-Tianjin-Hebei.
    Reference | Related Articles | Metrics | Comments0
    Seamless image completion via GAN inversion
    YU Yongsheng, LUO Tiejian
    Journal of University of Chinese Academy of Sciences    2024, 41 (5): 705-714.   DOI: 10.7523/j.ucas.2022.075
    Abstract595)      PDF(pc) (10147KB)(832)       Save
    Image completion is widely used in unwanted object removal and media editing, which aims to find a semantically consistent way to recover corrupted images. This paper is based on generative adversarial network (GAN) inversion, which leverages a pre-trained GAN model as an effective prior to filling in the missing regions with photo-realistic textures. However, existing GAN inversion methods ignore that image completion is a generative task with hard constraints, making final images have noticeable color and semantic discontinuity issues. This paper designs a novel bi-directional perceptual generator and pre-modulation network to seamlessly fill in the images. The bi-directional perceptual generator uses extended latent space to help the model perceive the non-missing regions of the input images in terms of data representations. The pre-modulated networks utilize a multiscale structure further providing more discriminative semantics for the style vectors. In this paper, experiments are conducted on Places2 and CelebA-HQ datasets to verify that the proposed method builds a bridge between GAN inversion and image completion and outperforms current mainstream algorithms, especially in FID metrics up to 49.2% enhancement at most.
    Reference | Related Articles | Metrics | Comments0
    Interference avoidance strategy for LEO satellite based on transmit beam sidelobe nulling
    WANG Haiwang, ZOU Cheng, CHANG Jiachao, SHAO Fengwei, JIANG Quanjiang, LI Guotong
    Journal of University of Chinese Academy of Sciences    2024, 41 (4): 541-549.   DOI: 10.7523/j.ucas.2022.068
    Abstract594)      PDF(pc) (5608KB)(930)       Save
    With the rapid development of broadband low-orbit satellite systems, communication frequency bands such as Ku and Ka tend to be saturated gradually, and non-geostationary orbit (NGSO) satellites will inevitably cause interference to geostationary orbit (GSO) satellites operating at the same frequency. At present, a spatial isolation strategy is often adopted to avoid interference. NGSO satellites always produce the strongest interference to the collinear area. Increasing the isolation angle can reduce the interference, but it will greatly lose the coverage of the LEO satellite. This paper proposes an interference avoidance strategy based on sidelobe nulling of the transmit beam. The antenna array is divided into row and column elements by establishing the LEO satellite coordinate system. In the dimension of column elements, the robust LCMV algorithm is used to realize wide nulling. In the dimension of row elements, it is expanded in combination with beam direction, and finally forms a “null band” in the direction of the collinear area. Through simulation analysis, the proposed strategy can effectively reduce the interference avoidance isolation area of LEO satellites while avoiding collinear interference. The algorithm has low complexity and is easy to implement on satellites.
    Reference | Related Articles | Metrics | Comments0
    Temporal and spatial variation of summer soil moisture and its driving factors in Yellow River basin during the last 20 years
    ZHANG Ya'nan, SONG Xiaoning, LENG Pei, GAO Liang, YIN Dewei
    Journal of University of Chinese Academy of Sciences    2024, 41 (4): 477-489.   DOI: 10.7523/j.ucas.2023.041
    Abstract564)      PDF(pc) (12970KB)(481)       Save
    Based on the moderate resolution imaging spectroradiometer products and global land data assimilation system meteorological data from 2001 to 2020, soil moisture in summer in the Yellow River basin was retrieved based on the vegetation index/land surface temperature trapezoid feature spatial model. The spatial-temporal pattern and driving factors of soil moisture in the Yellow River basin were analyzed using the Sen slope method, Mann-Kendall method, and geographical detector. The results showed that soil moisture in the Yellow River basin had apparent spatial heterogeneity. The source and lower reaches of the Yellow River are humid, while the middle reaches are relatively dry. From 2001 to 2020, soil moisture in the Yellow River basin showed an insignificant increase and an insignificant decrease in space, accounting for 39.54% and 58.01% of the regional area, respectively. The growth rate of soil moisture in the upper reaches was the fastest. Precipitation is the dominant factor of temporal variation of soil moisture in the Yellow River basin. Temperature and elevation are the main factors affecting the spatial variation of soil moisture in the upper reaches, and normalized difference vegetation index and precipitation are the main driving factors influencing soil moisture change in the middle reaches of the Yellow River.
    Reference | Related Articles | Metrics | Comments0
    SA-YOLO: self-adaptive loss object detection method under imbalance samples
    SU Yapeng, CHEN Gaoshu, ZHAO Tong
    Journal of University of Chinese Academy of Sciences    2024, 41 (3): 411-426.   DOI: 10.7523/j.ucas.2023.013
    Abstract561)      PDF(pc) (12585KB)(484)       Save
    The phenomenon of sample imbalance refers to the excessive number of background easy samples in the dataset but too few foreground hard samples, which means the sample suffers from inter-class imbalance and hard-easy imbalance. Most of the existing object detection methods are two-stage detectors based on proposed regions or one-stage detectors based on regression. When applied to imbalanced samples, it is impossible to avoid the over-dependence of the prediction bounding box generated in training on a large number of negative samples, which leads to overfitting of the model and low detection accuracy, poor accuracy and generalization. In order to achieve efficient and accurate object detection under imbalanced samples, a new SA-YOLO self-adaptive loss object detection method is proposed in the paper. 1) To address the sample imbalance problem, we propose the SA-Focal Loss function, which adjusts the loss adaptively for different datasets and training stages to balance inter-class samples and hard-easy samples. 2) In this paper, we construct the CSPDarknet53-SP network architecture based on the multi-scale feature prediction mechanism, which enhances the extraction ability of global features of difficult small target samples and improves the detection accuracy of difficult samples. To verify the performance of the SA-YOLO method, extensive simulation experiments are conducted on the sample imbalance dataset and the COCO dataset respectively. The results show that compared with the optimal metrics of YOLO series method, SA-YOLO reaches 91.46% of mAP in the imbalance dataset, which improves 10.87%, and the enhancement of AP50 for all kinds of objects is more than 2%, with excellent specialization; mAP50 in the COCO dataset is upgraded by 1.58%, and all indexes are not lower than the optimal value, with good effectiveness.
    Reference | Related Articles | Metrics | Comments0
    An adaptive variance reduction method with negative momentum
    LIU Hai, GUO Tiande, HAN Congying
    Journal of University of Chinese Academy of Sciences    2024, 41 (5): 577-588.   DOI: 10.7523/j.ucas.2024.024
    Abstract554)      PDF(pc) (3480KB)(596)       Save
    Stochastic variance reduction methods have been successful in solving large scale machine learning problems, and researchers cooperate them with adaptive stepsize schemes to further alleviate the burden of parameter-tuning. In this article, we propose that there exists a trade-off between progress and effectiveness of adaptive stepsize arising in the SVRG-BB algorithm. To enhance the practical performance of SVRG-BB, we introduce the Katyusha momentum to handle the aforementioned trade-off. The linear convergence rate of the resulting SVRG-BB-Katyusha algorithm is proven under strong convexity condition. Moreover, we propose SVRG-BB-Katyusha-SPARSE algorithm which uses Katyusha momentum sparsely in the inner iterations. Numerical experiments are given to illustrate that the proposed algorithms have promising advantages over SVRG-BB, in the sense that the optimality gaps of the proposed algorithms are smaller than the optimality gap of SVRG-BB by orders of magnitude.
    Reference | Related Articles | Metrics | Comments0
    Remote sensing inversion of CO2 emissions from super-large coal-fired power plants in China based on OCO-2/3 satellite
    GUO Wenyue, SHI Yusheng
    Journal of University of Chinese Academy of Sciences    2024, 41 (4): 490-502.   DOI: 10.7523/j.ucas.2023.050
    Abstract552)      PDF(pc) (21553KB)(903)       Save
    Coal-fired power plants are important contributors to CO2 emissions in China. Due to the low timeliness of statistical data and inaccurate emission factors, the existing emission inventories gradually fail to reflect the CO2 emissions of power plants. This study provides a method to estimate CO2 emissions from power plants based on Orbiting Carbon Observatory 2/3 (OCO-2/3) satellite data and Gaussian plume model, retrieving the images of super-large coal-fired power plants (≥5 000 MW) in China from the OCO-2 (September 6,2014-October 1, 2021) and OCO-3 (August 6, 2019-October 1, 2021) dataset, and identifying a total of seven plumes near Tuoketuo, Waigaoqiao, and Jiaxing power plants. Using a combination of three atmospheric background value determination methods, the CO2 emissions estimated by the Gaussian plume model range from 43 to 77 kt/d, with correlation coefficients ranging from 0.50 to 0.87. The uncertainties of individual plumes varied from 8% to 32% (1σ), with wind speed being the largest uncertainty (6%-31%), followed by background values (5%-18%), enhanced values (1%-21%), and plume rise (1%-8%). The estimates are verified to be in high agreement with Carbon Monitoring for Action, Carbon Brief, and the Global Power Emissions Database (Tuoketuo: (76.48±15.75), Waigaoqiao: (55.98±6.90), Jiaxing: (64.55±15.89) kt/d). This study helps monitor and estimate important point source carbon emissions, which is not only a prerequisite for the power industry to carry out carbon reduction efforts but also helps develop specific regional carbon reduction policies, thereby reducing anthropogenic carbon emissions.
    Reference | Related Articles | Metrics | Comments0
    Building extraction method based on MFF-Deeplabv3+ network for high-resolution remote sensing images
    CHEN Jingwei, LI Yu, CHEN Jun, ZHANG Hongqun
    Journal of University of Chinese Academy of Sciences    2024, 41 (5): 654-664.   DOI: 10.7523/j.ucas.2023.010
    Abstract535)      PDF(pc) (20364KB)(571)       Save
    Automatic extraction of building information from high-resolution remote sensing images is of great significance in the fields of environmental monitoring, earthquake mitigation, and land use, making it a research hotspot in the field of high-resolution remote sensing applications. In order to improve the accuracy of building extraction from high-resolution remote sensing images, a building extraction method based on MFF-Deeplabv3+(multiscale feature fusion-Deeplabv3+) network for high-resolution remote sensing images is proposed in this paper. First, the multi-scale feature enhancement module is designed to enable the network to capture more scale context information; then, the feature fusion module is designed to effectively fuse deep features with shallow features to reduce the loss of detail information; finally, the attention mechanism module is introduced to select accurate features adaptively. In the comparison experiments of the Inria building dataset, MFF-Deeplabv3+ achieved the highest accuracy in PA, MPA, FWIoU, and MIoU metrics with 95.75%, 91.22%, 92.12%, and 85.01%, respectively, while the generalization experiments of the WHU building dataset achieved good results. The results show that this method extracts building information from high-resolution remote sensing images with high accuracy and strong generalization.
    Reference | Related Articles | Metrics | Comments0
    Mahler measure of a two-variable polynomial
    ZHANG Anhao, TANG Guoping
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 145-150.   DOI: 10.7523/j.ucas.2022.060
    Abstract532)      PDF(pc) (841KB)(723)       Save
    In this paper, we express the Mahler measure of a two-variable polynomial P(x,y)=(x2+1)y2+2(x2+x)y+x(x2+1) as a linear sum of some Bloch-Wigner Dilogarithm functions. and prove that the Mahler measure of P(x,y) is rationally proportional to L'(χ-3,-1):m(P(x,y))=5/2L'(χ-3,-1).
    Reference | Related Articles | Metrics | Comments0
    Multi-scale featured convolution neural network-based soybean phenotypic prediction
    LIN Yutong, WANG Hong, CHAI Tuanyao
    Journal of University of Chinese Academy of Sciences    2024, 41 (4): 468-476.   DOI: 10.7523/j.ucas.2023.046
    Abstract526)      PDF(pc) (5008KB)(890)       Save
    In breeding, single nucleotide polymorphisms (SNPs) in the genome are often used to predict quantitative phenotypes to assist breeding, thereby improving breeding efficiency. The traditional statistical analysis method is limited by many factors including missing data, and its performance sometimes can not meet the requirements. In this paper, we proposed a multi-scale feature convolutional neural network model (MSF-CNN) to predict plant traits. The model extracted SNP features at three different scales through convolution and analyzed the significance of SNP sites through the weight of the SNPs input into the model. The test results showed that MSF-CNN model performed with higher accuracy than the known methods and other deep learning models in phenotype prediction on the datasets with missing genotypic data. This paper also studied the contribution of genotype to traits through saliency map, and discovered several significant SNP loci. These results showed that, compared with other known methods available at present, the deep learning model proposed in this paper can obtain more accurate prediction results of quantitative phenotypes, and can also effectively and efficiently identify SNPs associated with genome-wide association research.
    Reference | Related Articles | Metrics | Comments0
    Spatiotemporal variation in the maximum leaf area index of temperate grassland in northern China and its response to climate change
    FENG Yiming, ZHANG Na, YUE Rongwu, YAN Zhihui, LI Zhenyu, LI Xiaofan, Erridunqimuge
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 195-211.   DOI: 10.7523/j.ucas.2022.072
    Abstract525)      PDF(pc) (15706KB)(547)       Save
    There might be great differences in spatiotemporal variation in leaf area index (LAI) of different grassland types; the responses of LAI with different annual variations to climate change are probably distinct. To explore these differences, from the long-term LAI data and meteorological data and the grassland type data, we obtained the temporal and spatial varying characteristics of the maximum LAI of different types of temperate grassland in northern China from 1981 to 2017, and explored the responses of LAI with different annual variations to the changes of air temperature and precipitation. The results showed that the average annual maximum LAI of temperate grassland was (0.76±1.07) m2/m2, the higher in the east and the lower in the west. The meadow steppe had the highest LAI ((2.73±1.20) m2/m2) and the steppe desert had the lowest LAI ((0.13±0.17) m2/m2). From 1981 to 2017, the average annual maximum LAI showed a significantly increasing trend. The maximum LAI increased significantly for 32.52% of the area and decreased significantly for 6.31% of the area. The areas with a significantly increasing LAI were greater than those with a significantly decreasing LAI for all the grassland types. The annual average maximum LAI was positively correlated with the annual total precipitation from January to August and the annual mean air temperature for July and August. Both the significant decrease and increase of the maximum LAI was mainly affected by the significant increase of annual mean air temperature for July and August. There existed a critical threshold of the rising rate of air temperature for July and August that influenced the variation in LAI; for the grassland types that accounted for the larger areas, this threshold was 0.042-0.043 ℃/a. LAI increased with the rising air temperature as the rising rate of air temperature was lower than this threshold; conversely, LAI decreased. These results are expected to provide important scientific basis for grassland utilization, protection and restoration in the context of climate change.
    Reference | Related Articles | Metrics | Comments0
    Comparison study on classification accuracy of 11 common water indices based on Landsat 8 OLI images
    LI Longjie, YANG Yonghui
    Journal of University of Chinese Academy of Sciences    2024, 41 (6): 755-765.   DOI: 10.7523/j.ucas.2023.088
    Abstract524)      PDF(pc) (13417KB)(485)       Save
    Water index is one of the most effective methods to extract water bodies from remote sensing images. There are many kinds of water index, each with its own characteristics. It is, therefore, necessary to select the index with best classification accuracy. Taking Shijiazhuang City as the research area, 11 common water indices were used to extract water bodies from Landsat 8 OLI images. The accuracy of the water index extraction results is validated by using the visual interpretation (VI) result as the standard classification map from Sentinel-2 MSI based on the area test method in combination with transition matrix and sampling test method. Results show little difference in the extraction of large water bodies among different water indices. Small ponds and rivers can better check the extraction ability of water index. It is proved that Water Index 2019 (WI2019) has the best water classification. WI2019 is then used to find out the recent expansion of water bodies after the start of South-to-North Water Diversion Project for water transfer. It was found that the area of surface water body in Shijiazhuang excluding large reservoirs increased significantly, from 42 km2 in 2014 to 62 km2 in 2020, an increase of 20 km2. In view of the canal seepage control treatment at the bottom of most newly added water bodies, with poor groundwater recharge function, and more ineffective evaporation, it is recommended to properly control the scale of water bodies in order to effectively reduce the waste of water transferred from outside.
    Reference | Related Articles | Metrics | Comments0
    Robust individualized subgroup analysis
    ZHANG Xiaoling, REN Mingyang, ZHANG Sanguo
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 151-164.   DOI: 10.7523/j.ucas.2022.037
    Abstract520)      PDF(pc) (1144KB)(565)       Save
    Subgroup analysis of heterogeneous groups is a crucial step in the development of individualized treatment and personalized marketing strategies. Regression-based approaches are one of the main schools of subgroup analysis, a paradigm that divides predictor variables into two parts with heterogeneous and homogeneous effects and divides the sample into subgroups based on the heterogeneous effects. However, most of the existing regression-based subgroup analysis methods have two major limitations: First, they still consider the sample homogeneous within subgroups and do not fully consider individual effects; Second, the common contamination phenomenon of homogeneous effect variables is not taken into account, which will lead to large bias in the model results. To address these challenges, we propose a robust individualized subgroup analysis. We use a multidirectional separation penalty function to achieve individualized effects analysis for the heterogeneous part of the model and use γ-divergence to obtain robust estimates for the contaminated homogeneous part. We also propose an efficient alternating iterative two-step algorithm, combining coordinate descent and alternating direction method of multipliers (ADMM) techniques to implement this process. Our proposed method is further illustrated by simulation studies and analysis of a skin cutaneous melanoma dataset.
    Reference | Supplementary Material | Related Articles | Metrics | Comments0
    Remote sensing extraction method of agricultural greenhouse based on an improved U-Net model
    WANG Yinda, PENG Ling, CHEN Deyue, LI Weichao
    Journal of University of Chinese Academy of Sciences    2024, 41 (3): 375-386.   DOI: 10.7523/j.ucas.2023.060
    Abstract477)      PDF(pc) (27690KB)(803)       Save
    The agricultural greenhouse is a kind of agricultural facility, which is divided into transparent and non-transparent according to the surface transmittance. The large-scale statistics of agricultural greenhouses are of great significance to the survey of agricultural facilities, the formulation of agricultural policies, and the planning of county economic development. Aiming at the problem that manual statistics are time-consuming and laborious, this paper utilizes the convolutional neural network to extract agricultural greenhouses information from high-resolution remote sensing images. To solve the problems of insufficient semantic information extraction in remote sensing images and insufficient utilization of edge information of the U-Net model, this paper proposes the following improvements: 1) The semantic segmentation task is optimized, and ConvNeXt and attention mechanism is utilized to extract deep semantic information of agricultural greenhouses in remote sensing images. 2) The edge detection task is introduced, and the gated convolution layer and concate operation are used to fuse the semantic features of the encoder and the image gradient output by the decoder, and then the edge information is combined to optimize the segmentation results. After testing, the improved model can extract both transparent and non-transparent agricultural greenhouses information at the same time and the recognition effect is good, which is greatly improved compared with the traditional method.
    Reference | Related Articles | Metrics | Comments0
    Lightweight network for fast ship detection in SAR images
    ZHOU Wenxue, ZHANG Huachun
    Journal of University of Chinese Academy of Sciences    2024, 41 (6): 776-785.   DOI: 10.7523/j.ucas.2023.017
    Abstract458)      PDF(pc) (34205KB)(549)       Save
    In the field of SAR image ship detection based on deep learning, traditional models are usually complex in structure and require a large amount of calculation, making them unsuitable for low computing power platforms and real-time detection. And convolutional neural networks that rely on preset anchor boxes will lead to a lot of computational redundancy due to the difficulty of setting a reasonable anchor box. To solve these problems, an end-to-end lightweight convolutional neural network based on anchor-free design is proposed, and a lightweight channel attention module (EESE) is designed and applied to the detection head (ED-head), to resolve the conflict between classification and localization tasks. In addition, an optimized EIOU loss function is proposed, which enables the model to effectively improve the network performance without increasing the inference time. The proposed method is tested on the SSDD dataset, and the experimental results show that compared to YOLOX-nano, AP50 and AP are increased by 2.1 and 7.4 percentage points, respectively, with the CPU latency being only 5.33 ms, much less than 13.13 ms of YOLOX-nano. The proposed method achieves a balance between accuracy and efficiency.
    Reference | Related Articles | Metrics | Comments0
    Power performance measurement based on nacelle mounted Lidar
    LIANG Zhi, SHI Yu, ZHANG Zhe, HU Fei
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 257-267.   DOI: 10.7523/j.ucas.2022.036
    Abstract455)      PDF(pc) (11445KB)(469)       Save
    The power performance measurement (PPM) of wind turbine is an objective method to evaluate the performance of wind turbine, which is the basis for the optimization of the wind turbine, the calculation of annual energy production and other related topics. Traditional testing method usually installs the ground-based equipment, such as the meteorological mast or ground-based lidar, which are more constrained by the on-site conditions. The nacelle mounted Lidar (NML), which can be installed on the top roof on wind turbine nacelle, could overcome the constraints of the on-site conditions. In recent years, NML starts to be used in PPMs, especially for offshore wind turbines. In this paper, the PPM had been conducted by using NML, and the differences were analyzed. The results showed that the wind speed accuracy of NML was consistent with the meteorological mast, the correlation coefficient of the two devices was 0.994, and the slope and offset by linear regression were 0.979 and 0.084, respectively; the scattering point of PPM by NML was more concentrated, and NML was always measuring the wind speed exactly in front of the wind turbine with the yawing of the wind turbine nacelle, which was better representative of the wind speed. The AEP assessment results showed that the NML was 1.73% overestimated relative to the met mast, and the overall evaluation error range was smaller due to the lower dispersion of NML. The NML had a better representation of wind speed than met mast, with less uncertainty, and had value for the application of PPM of wind turbine.
    Reference | Related Articles | Metrics | Comments0
    Dynamic mechanism and river evolution under coupling effects of surficial and tectonic processes: a case study of Qinghai Lake and Daotang River
    MIAO Yu, ZHANG Huai, SHI Yaolin
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 212-221.   DOI: 10.7523/j.ucas.2022.056
    Abstract442)      PDF(pc) (13615KB)(750)       Save
    Since the late Cenozoic, the geodynamic mechanism of the transformation of Qinghai Lake from the external lake to the endorheic lake is still an open problem. The Daotang River is an important channel for transforming from external-flow to the endorheic-flow type of Qinghai Lake. Its evolution records the prominent landform transition event. Based on the newly developed numerical calculation program for geomorphic evolution with finite volume method, in this work, we conduct a series of the landscape evolution models of the Daotang River under the combined influence of mountain uplift and river downcutting, and have a quantitative analysis of the effects of uplift rate and river undercutting coefficient on river backflow patterns. We attempt to explore the mechanism of landform transition events that could provide evidence for the formation process of Daotang River basin and the origin of Qinghai Lake. Our modeling results indicate that the reorganization of the river system and backward flow of the river is jointly controlled by the rapid mountain uplift from the Riyue Mountain active fault and the river undercutting coefficient. The mountain uplift rate is the controlling factor that affects the reorganization of the river system in the Daotang River basin. When rising mountains block the river, the river incision coefficient is the factor that controls the rate of reorganization that occurs in the basin. The result recognizes they have enlightening significance for further understanding the dynamic mechanism of river evolution under the regional tectonic deformation and the coupled surface processes.
    Reference | Related Articles | Metrics | Comments0
    Uncertainty-based credit assignment for cooperative multi-agent reinforcement learning
    YANG Guangkai, CHEN Hao, ZHANG Mingyi, YIN Qiyue, HUANG Kaiqi
    Journal of University of Chinese Academy of Sciences    2024, 41 (2): 231-240.   DOI: 10.7523/j.ucas.2022.047
    Abstract426)      PDF(pc) (6471KB)(1078)       Save
    In recent years, multi-agent cooperation under partially observable conditions has attracted extensive attention. As a general paradigm to deal with such tasks, centralized training with decentralized execution faces the core problem of credit assignment. Value decomposition is a representative method within this paradigm. Through the mixing network, the joint state action-value function is decomposed into multiple local observation action-value functions to realize credit assignment, which performs well in many problems. However, the single point estimation of the mixing network parameters maintained by these methods lacks the representation of uncertainty and is thus difficult to effectively deal with the random factors in the environment, resulting in convergence to the suboptimal strategy. To alleviate this problem, this paper performs Bayesian analysis on the mixing network and proposes a method based on uncertainty for multi-agent credit assignment, which guides the credit assignment by explicitly quantifying the uncertainty of parameters. Considering the complex interactions among agents, this paper utilizes the Bayesian hypernetwork to implicitly model the arbitrary complex posterior distribution of the mixing network parameters, to avoid falling into the local optima by specifying the distribution type a priori. This paper compares and analyzes the performance of representative algorithms on multiple maps in StarCraft multi-agent challenge (SMAC) and verifies the effectiveness of the proposed algorithm.
    Reference | Related Articles | Metrics | Comments0

News More+

Download More+

Links More+