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2024, Vol. 41 No. 1

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15 January 2024

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  • Innovation Article
    Calculating the thermal stress of the moon in cooling process with 3-D viscoelastic model
    JIN Yimin, TAO Sha, SHI Yaolin
    2024, 41 (1): 1-10.  DOI: 10.7523/j.ucas.2022.059
    Abstract ( 325 ) PDF (0KB) ( 0 )
    Thermal stress of the moon due to cooling process is non-negligible in lunar evolution. We calculate the accumulation of thermal stress with 3-D viscoelastic model, and explore the influence of viscosity parameters on thermal stress through comparative experiments. Numerical results suggest that the thermal stress of lithosphere is utterly distinct from deep mantle. The lithosphere is under tangential compression that concentrates at the bottom of the crust because of unevenly distributed cooling rate and elastic strength; on the other hand, the accumulation and relaxation of thermal stress in deep mantle is balanced due to low viscosity, and the thermal stress is in a “hydrostatic” state, which is mainly controlled by the elastic surface. Under the assumption that viscosity of lunar lithosphere is greater than 1028 Pa·s, the tangential compressive stress in lithosphere accumulates to several hundreds of MPa in the present day, while the tensile stress in deep mantle reaches up to 100 MPa. Consequently, part of the shallow moonquake events can be explained by thermal stress. However, the focal mechanism of deep moonquakes is still unclear. We speculate that the tensile thermal stress in deep mantle helps to develop pore structures, and the melting layer provides pore fluid with high pressure, which reduces the fracture strength of mantle medium.
    Review Article
    Learning path planning methods
    LUO Zhongkai, ZHANG Libo
    2024, 41 (1): 11-27.  DOI: 10.7523/j.ucas.2022.061
    Abstract ( 675 ) PDF (0KB) ( 5 )
    This review aims to guide the future development of related research in the field of learning path planning through the analysis of the current research status of learning path planning. Specifically, this review first introduces the definition of learning path planning and the commonly used parameters in learning path planning methods; then, it classifies in detail according to the algorithms used to generate learning path planning and summarizes the advantages and disadvantages of various learning path planning methods. In addition, the data set and evaluation method used by the learning path planning method is introduced. Finally, the challenges faced by the learning path planning method are summarized and the future development trend is predicted.
    Research Articles
    Continuity of the Lp-norm of the truncated Hardy-Littlewood maximal operator
    WU Jia, WEI Mingquan, YAN Dunyan
    2024, 41 (1): 28-34.  DOI: 10.7523/j.ucas.2021.0073
    Abstract ( 279 ) PDF (0KB) ( 0 )
    This paper focuses on the continuity of Lp(Rn)→Lp(Rn)-norm of the truncated Hardy-Littlewood maximal operator Mba with two truncation parameters a and b. We first, respectively, present the left semi-continuity and right semicontinuity of ‖MbaLp(Rn)→Lp(Rn) with respect to θ=b/a, and then the continuity of ‖MbaLp(Rn)→Lp(Rn) is extended to infinity.
    Nucleon resonances in γp→π-Δ++ photoproduction
    ZHU Yiming, YANG Fuzhong
    2024, 41 (1): 35-41.  DOI: 10.7523/j.ucas.2021.0042
    Abstract ( 338 ) PDF (0KB) ( 0 )
    The first measured high-precision data on the differential cross sections and polarization observable beam asymmetry Σ for the γp→π-Δ++ reaction from the LEPS collaboration are analyzed within a tree-level effective lagrangian approach. In addition to the t-channel π and ρ exchanges, the u-channel Δ exchange, the s-channel N exchange, and the interaction current that is required by the gauge invariance, the s-channel nucleon resonance exchanges are further taken into account to reproduce the data of LEPS. Numerical results show that, the data on Σ can not be well reproduced when no contributions from the s-channel resonance exchanges are introduced. Further analyses show that, by including the contribution from the resonance N(1860)5/2+, both the data on the differential cross sections and beam asymmetry Σ can be well reproduced.
    Curing process of 1,3-di(2'-aminoethyl)-2-methylimidazolium bromide with epoxy resin E-51
    SU Ze, BAI Jinhu, WU Qiong, LIU Long, ZHANG Yanqiang
    2024, 41 (1): 42-49.  DOI: 10.7523/j.ucas.2022.049
    Abstract ( 178 ) PDF (0KB) ( 0 )
    A diaminoimidazole ionic liquid curing agent, 1,3-di(2'-aminoethyl)-2-methylimidazolium bromide (DAIL) is prepared via quaternization of imidazole rings. With epoxy resin E-51 as matrix resin, the curing process conditions of DAIL as curing agent and the properties of cured products are studied in depth. The results show that DAIL can be used as a medium temperature curing agent for epoxy resins. The optimal ratio of the two is DAIL∶E-51=20∶100, the optimal curing temperature range is 74~105 ℃, and the post-curing temperature is 162 ℃. The tensile strength of the cured cast body splines is 159 MPa, the elastic modulus is 2 281 MPa, and the elongation at break is 12.8%, the thermal decomposition temperature is 424.4 ℃. DMA analysis shows that the maximum loss factor tanδ of the DAIL/E-51 cast body is 0.56, and the glass transition temperature θg is 83 ℃, the corresponding storage modulus E is 290 MPa, and the crosslinking density is 30 149 mol·m-3. This study provides an important experimental basis for the use of high mechanical properties of medium temperature epoxy resin curing agent.
    Cause of thermal event moonquakes by thermos-elastic stress finite element models
    ZHANG Junce, HU Caibo, SHI Yaolin
    2024, 41 (1): 50-64.  DOI: 10.7523/j.ucas.2022.045
    Abstract ( 326 ) PDF (0KB) ( 0 )
    On the basis of the previous work, considering the solar heat absorbed by the lunar surface inward and the lunar thermal radiation heat released outward, as well as the nonlinearities of the thermodynamic parameters of the lunar soil related to the temperature and depth, we have developed a thermo-elastic coupled finite element parallel program suitable for the study of the temporal and spatial evolutions of the temperature, deformation, and thermal stress of the lunar soil, and have utilized the four sets of finite element models to investigate the effects of the characteristic thicknesses of the lunar soil on the temporal and spatial evolutions of the temperature, deformation and thermal stresses of the lunar surface. The computational results show that the temperature of the lunar surface varies periodically over one lunar day (29.5 Earth days), and the temperature of the equatorial lunar surface varies from 100 to 385 K, with the variation decaying exponentially with the increase of the depth, and the depth of influence reaches to about 50 cm. The temperature cyclic changes also cause the vertical displacement of the lunar surface to rise and fall, and the horizontal normal stress of the lunar surface in the form of compression and tension. In general, the horizontal stresses are compressed during the day and tensile during the night, with the fastest increase in tensile stress at 18:00 and the highest tensile stress at 06:00. The characteristic thickness of the lunar soil has a strong influence on the temporal and spatial distributions of the temperature and the horizontal positive stresses. The magnitude of thermal stresses may reach the tensile strength of the lunar surface. The fastest growth of tensile stress and the period of maximum amplitude coincide with the observed high frequency of thermal events on the lunar surface in the morning and evening.
    Application of infinite-spectral hybrid method in 2.5-dimensional gravitational potential calculation
    REN Junsheng, ZHANG Huai
    2024, 41 (1): 65-69.  DOI: 10.7523/j.ucas.2022.041
    Abstract ( 139 ) PDF (0KB) ( 0 )
    Gravitational potential is an inseparable part of the earth’s free oscillation simulation. It is also the object of calculation in the study of gravity anomalies. Since the gravitational potential satisfies the unbounded Poisson-Laplace equation, which is zero at infinity, this is frustrating for numerical simulations. The purpose of numerical simulation is usually achieved by limiting the solution domain and approximating its boundary conditions. We attempt to use the infinite-spectral hybrid method to fit the infinity boundary directly and no longer approximate the boundary conditions. Considering the computational efficiency of the 3D Earth model, this study uses a 2.5-dimensional governing equation. Finally, numerical experiments verify the factual accuracy of this method.
    Coseismic deformation of Maduo MS7.4 earthquake in Qinghai, on May 22, 2021: numerical simulation analysis and geodynamic enlightenment
    MENG Sichen, MENG Qiu, CHEN Qizhi, HU Caibo
    2024, 41 (1): 70-80.  DOI: 10.7523/j.ucas.2022.046
    Abstract ( 138 ) PDF (0KB) ( 0 )
    The Maduo MS7.4 earthquake in Qinghai on May 22, 2021 is the only strong earthquake that occurred in Bayan Har block in recent years. The coseismic deformation and stress adjustment of the Maduo earthquake have been highly concerned by many scholars. In this paper, a three-dimensional parallel elastic finite element program for coseismic deformation simulation of large earthquakes is developed using split node technique. The correctness and effectiveness of the program were verified by comparing with the analytical solutions of the elastic seismic dislocation models. We calculated the coseismic deformation of the Maduo MS7.4 earthquake and the coseismic Coulomb stress changes on the major faults in the research area. The results show that the surface coseismic deformation is consistent with those by different geodetic observation data and inversion results of some finite fault models. It also shows the earthquake is mainly a sinistral strike-slip fault with some normal fault components. Most aftershocks (magnitude>1.0 and depth of 9-11 km) except those besides the mainshock fault located in the regions of positive Coulomb stress changes at the depth of 10 km. The distribution of the Coulomb stress changes on the different fault zones is not uniform. The Coulomb stress changes on the southern end of Elashan Fault zone, the eastern end of Kunzhong Fault zone, most segments except some central-western parts of East Kunlun Fault zone, the northwestern segment of Dari Fault zone and the northwest and southeast segments and regions near the mainshock of Maduo-Gande Fault zone increase obviously, which requires more attention.
    Calculation method of geometric parameters for decision support of “Zhurong” Mars rover leaving the landing platform
    LI Hao, MA Youqing, ZHANG Shuo, LIU Shaochuang
    2024, 41 (1): 81-87.  DOI: 10.7523/j.ucas.2022.048
    Abstract ( 255 ) PDF (0KB) ( 0 )
    The departure of Zhurong Mars rover from the landing platform is the first key action performed after the Tianwen-1 detector system landing on Mars, and it is the basis for subsequent inspections of the Martian surface. In order to provide decision support for the safe departure of the rover, a method for calculating the angle between planes based on the three-dimensional image of the navigation camera is proposed to calculate the angle between the two departure orbit planes and the departure angle (the angle between the departure orbits and the surface of Mars). The process of decision support for Mars rover departure based on the navigation camera images is described. First, the forward intersection algorithm was used to obtain the coordinates of the point cloud on the surface of Mars and the coordinates of the departure orbits feature points. Then a plane fitting method combining the random sample consensus (RANSAC) algorithm and the total least squares method was used to fit the departure orbit plane and the surface of Mars, and the rationality and robustness of the method was verified through simulation experiments. At the end, the angle between the departure orbit planes (0.203°) and two departure angle (-18.947°, -19.154°) were calculated and used in the decision of Zhurong rover departure. On May 22, 2021, the Zhurong Mars rover successfully departed from the landing platform and set foot on the surface of Mars.
    An improved UAV-borne DInSAR baseline estimation method based on interferometric phase period
    ZHANG Tong, QIAO Ming, DANG Xiangwei, ZHONG Shengyiliu
    2024, 41 (1): 88-96.  DOI: 10.7523/j.ucas.2022.053
    Abstract ( 173 ) PDF (0KB) ( 0 )
    UAV (unmanned aerial vehicle)-borne differential interferometric synthetic aperture radar (SAR) has unique advantage and has attracted the attention of key research institutions at home and abroad in recent years. Baseline is a crucial parameter in differential in DInSAR processing, which is directly related to the accuracy of interferometric measurements. Compared with space-borne InSAR, UAV platform is difficult to keep the flight at the same track, and the flight attitude are unstable, which brings great difficulties to the baseline estimation of UAV-borne DInSAR. In this paper, starts from the characteristics of UAV platform and application scenarios, an improved baseline estimation method is proposed. This method derives the relationship between the interference phase period, the slant range, the distance between two ground points, and the phase difference through the interference geometric relationship. The distance between the two points is then substituted into the known parameters for baseline estimation using the least squares method. Comparing the simulation results and the actual data results of the original method and the improved method, it shows that the accuracy and robustness of the baseline estimation results of the improved method are significantly improved.
    A remote sensing image registration method combining feature information clustering and partitioning
    SHI Zhengyi, LIU Shuo, XIA Hao
    2024, 41 (1): 97-106.  DOI: 10.7523/j.ucas.2022.021
    Abstract ( 124 ) PDF (0KB) ( 0 )
    Aiming at the problem that the global registration model can’t correctly fit the local region due to topographic relief and rich ground object types, this paper proposes a method to quickly divide the image region and realize fine fitting based on feature information hierarchical clustering method. This method uses the scale constraint of difference space to extract the feature points of sift with higher accuracy, and optimizes the matching efficiency combined with Hellinger transform to complete the rough feature matching. The initial clustering is completed according to the point neighborhood information, and different models are obtained; the coincidence degree of matching points to different transformation models is calculated, the tendency set is constructed, the set is merged according to the distance to obtain the cluster center; and the sub region is generated using Tyson polygon method. The transformation model of each sub region is solved and interpolated to obtain the registration results. The remote sensing images of farmland, mountainous areas and coastal cities and towns are used for experiments. The registration effects of SIFT+ST, FSC-SIFT and PSO-SIFT methods are compared with this method. The results show that the accuracy and visual registration effect of this method are better.
    An image matching algorithm combining local and semi-global geometry preservation
    ZHENG Meiyan, CHEN Jun, GE Xiaoqing, ZHANG Hong
    2024, 41 (1): 107-116.  DOI: 10.7523/j.ucas.2022.019
    Abstract ( 272 ) PDF (0KB) ( 0 )
    Remote sensing image matching is an essential preprocessing step for many remote sensing applications. However, the distortions caused by elevation differences and the complexity of remote sensing image matching severely limit the matching precision of high-resolution remote sensing images. This paper proposes a robust feature matching algorithm suitable for local distortion and high outlier ratio. First, the Delaunay triangulation algorithm is used to impose geometric constraints on the initial matching point set, and the local adjacency relationship of the feature points is obtained. Second, pre-filter is conducted based on the adjacency information. Third, a multi-scale strategy is used to establish the local adjacency consistent model. Finally, a triangle similarity function is defined to achieve matching recovery. The experimental results on high-resolution images show that the average accuracy of our algorithm is 7.69% higher than that of RANSAC, and it is still robust when the outlier ratio is higher than 90%.
    Local observation reconstruction for Ad-Hoc cooperation
    CHEN Hao, YANG Likun, YIN Qiyue, HUANG Kaiqi
    2024, 41 (1): 117-126.  DOI: 10.7523/j.ucas.2022.028
    Abstract ( 354 ) PDF (0KB) ( 0 )
    In recent years, multi-agent reinforcement learning has received a lot of attention from researchers. In the study of multi-agent reinforcement learning, the question of how to perform ad-hoc cooperation, i.e., how to adapt to a changing variety and number of teammates, is a key problem. Existing methods either have strong prior knowledge assumptions or use hard-coded protocols for cooperation, which lack generality and can not be generalized to more general ad-hoc cooperation scenarios. To address this problem, this paper proposes a local observation reconstruction algorithm for ad-hoc cooperation, which uses attention mechanisms and sampling networks to reconstruct local observations, enabling the algorithm to recognize and make full use of high-dimensional state representations in different situations and achieve zero-shot generalization in ad-hoc cooperation scenarios. In this paper, the performance of the algorithm is compared and analyzed with representative algorithms on the StarCraft micromanagement environment and ad-hoc cooperation scenarios to verify the effectiveness of the algorithm.
    Design and implementation of fuzzy extractor for PUF
    SONG Minte, HOU Kai, RU Zhanqiang, WANG Zhengguang, SONG Helun
    2024, 41 (1): 127-135.  DOI: 10.7523/j.ucas.2022.054
    Abstract ( 316 ) PDF (0KB) ( 5 )
    The physical unclonable function (PUF) implemented on SRAM and other schemes exists inherent demerit of poor reproducibility for environmental factors such as voltage changes and thermal noise. This disadvantage greatly restricts functional application in cryptography, communication and other fields. In this paper, a fuzzy extractor with large error correction capacity is designed to reconstruct the original data of SRAM by means of BCH codes (Bose-Chaudhuri-Hocquenghem Codes). The SRAM PUF chip applying this design is manufactured on the Hua Hong Grace 0.11 μm CMOS platform with area of 306 267 μm2. The original BCH code has a code length of 127 bits and an error correction capability of 27 bits, which achieves the practical requirements of PUF applications.
    Identification of core rumor spreaders in online social networks based on multi-stage deep model
    LI Yuan, ZHANG Qi, ZHU Jianming, JIAO Jianbin
    2024, 41 (1): 136-144.  DOI: 10.7523/j.ucas.2022.057
    Abstract ( 329 ) PDF (0KB) ( 6 )
    Online social networks have become the disaster areas where rumors grow. It is of great significance to identify core rumor spreaders for rumor prevention and control. The traditional rumor control model is mainly based on the dynamics of rumor propagation, and it is mainly focused on in-event or post-event control. In view of the timeliness of rumor control, this paper proposes a multi-stage graph convolutional network based on multi-dimensional features (MSF-GCN) deep learning model to accurately locate core rumor spreaders as early as possible and block rumor diffusion from the source. This work compares the MSF-GCN method with other three baseline methods on rumor data set, and the experimental results verify that our method is more efficient.
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    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
    Abstract1480)      PDF(pc) (727KB)(17199)       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 .
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    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
    Abstract488)      PDF(pc) (9359KB)(14998)       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.

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    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
    Abstract2907)      PDF(pc) (1045KB)(6346)       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.

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    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
    Abstract2253)      PDF(pc) (154KB)(5796)       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.

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    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
    Abstract2732)      PDF(pc) (832KB)(5380)       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.
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    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
    Abstract2114)      PDF(pc) (1120KB)(4776)       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.
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    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
    Abstract3066)      PDF(pc) (268KB)(4317)       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.

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    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
    Abstract1566)      PDF(pc) (173KB)(4082)       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.

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    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
    Abstract2628)      PDF(pc) (820KB)(4000)       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.

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    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
    Abstract2440)      PDF(pc) (1138KB)(3893)       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.
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    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
    Abstract3309)      PDF(pc) (1395KB)(3690)       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.

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    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
    Abstract2586)      PDF(pc) (1540KB)(3642)       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.
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    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
    Abstract972)      PDF(pc) (1223KB)(3628)       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.

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    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
    Abstract2214)      PDF(pc) (929KB)(3397)       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.

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    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
    Abstract2008)      PDF(pc) (816KB)(3366)       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.
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    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
    Abstract1811)      PDF(pc) (832KB)(3325)       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.
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    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
    Abstract1804)      PDF(pc) (152KB)(3279)       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%.

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    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
    Abstract2648)      PDF(pc) (833KB)(3196)       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.
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    MEIL--A routing protocol with high throughput over wireless mesh network
    ZHANG Rui, HONG Pei-Lin ,LU Han-Cheng , ZHANG Xing
       2007, 24 (4): 473-479.   DOI: 10.7523/j.issn.2095-6134.2007.4.011
    Abstract2326)      PDF(pc) (977KB)(3064)       Save
    Because of the unique characteristics over wireless mesh networks, such as multi-radio multi-channel and static nodes, traditional Ad hoc network routing protocols can not work very well, which are based on the condition of “shortest path”. This paper presents a novel routing protocol named MEIL for wireless mesh networks. It designs routing metrics according to the wireless link loss, interference between channels and the load of wireless mesh nodes. MEIL chooses the route with lower loss, smaller interference and lighter load, so it can improve the throughput of the network efficiently. The simulation results show that MEIL performs much better than the AODV routing protocol and the DSDV+ETX algorithm under the circumstances of various services, and it is suitable for wireless mesh networks.
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    Cytotoxicity of ZnO nanoparticles in human lung cancer cell lines A549
    WANG Lin , WANG Li-juan , ZHANG Fang , DING Wen-jun
       2009, 26 (1): 83-90.   DOI: 10.7523/j.issn.2095-6134.2009.1.012
    Abstract2292)      PDF(pc) (1035KB)(2989)       Save
    The aim of the study was to investigate the toxic effects of nanosized ZnO in vitro. Characterization of ZnO nanoparticles was carried out by atomic force microscope (AFM), transmission electron microscope (TEM) and X-ray diffraction (XRD). In this study, lung cancer cell lines A549 were exposed to 0mmol/L, 0.1mmol/L, 0.5mmol/L, 1mmol/L, 5mmol/L, 10mmol/L of ZnO nanoparticles, respectively. MTT assay was performed to evaluate the viabilities of ZnO-treated cells after 12h, 24h, 36h and 48h exposure. The activities of lactate dehydrogenase (LDH), cellular superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) were determined after exposure to 1mmol/L ZnO for 24 h. Moreover, apoptotic characteristics and reactive oxygen species (ROS) production in A549 cells were measured. ZnO nanoparticles were needlelike crystals (75 nm length; 20 nm diameter). The viability of A549 cells were reduced after exposure to ZnO nanoparticles in a dose-dependent manner. The activities of LDH and the levels of MDA were significantly increased (P < 0.05, P < 0.01), respectively. However, the activities of CAT were significantly decreased (P < 0.01). No significant difference in the activities of SOD was observed between the ZnO-treated cells and the controls. ZnO nanoparticles at 1mmol/L induced apoptosis in A549 cells. The levels of ROS in ZnO-treated cells were significantly higher than that in controls. These results suggested that ZnO nanoparticles could result in apoptosis in A549 cells through oxidative stress.
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    Three-dimensional point cloud denoising
    XIAO Jun, SHI Guangtian
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 577-595.   DOI: 10.7523/j.ucas.2022.038
    Abstract2014)      PDF(pc) (14314KB)(1833)       Save
    With the development of 3D data acquisition technology, point cloud wins the favor of researchers for it's simple but effective representation and it is widely used in the fields of remote sensing, scene reconstruction, 3D modeling, etc. Considering that the data acquisition process is easily disturbed by many factors such as equipment, environment and material, raw point cloud is often corrupted with noise and so it is of great significance to explore robust and efficient denoising algorithms. This paper firstly investigates the relevant research works of point cloud denoising and divides them into traditional algorithms based on the optimization idea and denoising algorithms based on the deep learning idea according to the implementation principles. Secondly, the research progress of each kind of algorithm is discussed and a detailed analysis of representative algorithms is presented. Thirdly, the data sets, the evaluation metrics and experimental results are summarized with an in-depth comparison. Finally, the problems and possible development directions and trends of point cloud denoising are prospected.
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    Learning path planning methods
    LUO Zhongkai, ZHANG Libo
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 11-27.   DOI: 10.7523/j.ucas.2022.061
    Abstract675)      PDF(pc) (2927KB)(719)       Save
    This review aims to guide the future development of related research in the field of learning path planning through the analysis of the current research status of learning path planning. Specifically, this review first introduces the definition of learning path planning and the commonly used parameters in learning path planning methods; then, it classifies in detail according to the algorithms used to generate learning path planning and summarizes the advantages and disadvantages of various learning path planning methods. In addition, the data set and evaluation method used by the learning path planning method is introduced. Finally, the challenges faced by the learning path planning method are summarized and the future development trend is predicted.
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    Temporal and spatial variation of diurnal asymmetric warming and its drivers in China
    HE Chang, DENG Jianming, CHEN Shuang
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 596-604.   DOI: 10.7523/j.ucas.2022.042
    Abstract459)      PDF(pc) (4950KB)(324)       Save
    Recently, a major feature of global warming is asymmetrical temperature increase during day and night, i.e., the rate of warming at night is greater than that during the day. However, effects of asymmetrical warming have not yet attracted widespread attention. In this study, by collecting historical observation data of 838 meteorological stations in China, and using methods such as trend estimation, the characteristics of the temporal and spatial variation of diurnal temperature range (DTR) and the long-term trends of DTR from 1952 to 2018 were analyzed. The results indicated that:spatially, the regions with the highest average annual DTR in the country were distributed in the northwest and southwest, followed by the northeast and north China, and the areas with lowest DTR located in central, eastern, and southern China. The average monthly DTR in the year was generally multimodal. Among four seasons, DTR in spring and autumn was higher than in summer. From 1952 to 2018, the annual average DTR decreased significantly (τ=-0.396; p<0.01). Long-term changes in DTR were positively correlated with evaporation, sunshine hours, latitude and altitude, and negatively correlated with wind speed, precipitation, relative humidity, station pressure, total cloudiness, and longitude.
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    Optimal design of the vacuum interlock and monitor systems for BSRF soft X-ray endstation
    LI Jialiang, LIU Shuhu, SHANG Congjian, WANG Fei
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 677-686.   DOI: 10.7523/j.ucas.2021.0069
    Abstract432)      PDF(pc) (6983KB)(125)       Save
    Beijing synchrotron radiation facility (BSRF) 4B7B soft X-ray endstation is an ultra-high vacuum system, which is connected to the upstream beamline through an electromagnetic plug-in valve. Scientific research users are prone to misoperation when changing samples in experiment. When valve is not closed, vacuum system is vented and equipment is damaged. In order to avoid vacuum accidents, this article proposes to optimize the original manual protection measures and design vacuum safety interlock protection systems. Vacuum gauge, pneumatic angle valve, and electromagnetic flapper valve are interlocked and controlled by electrical components, aiming to improve the convenience and reliability of user's operation on the basis of ensuring the vacuum safety of endstation when user changes samples. The safety interlocking protection system control cabinet was confirmed to meet the expected design requirements after many commissioning inspections and trial runs after landing, and was formally applied in soft X-ray calibration experiment, effectively ensuring the safety and reliability of equipment during user operation. In addition, application prospect of the safety interlock protection system in beamline of high energy photon source (HEPS) in the future is discussed in this article, and engineering design experience is provided for construction of vacuum interlocking protection system of HEPS beamline.
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    Tectonic evolution and mineralization of Carlin-type gold deposits in Youjiang basin
    FENG Hongye, JU Yiwen, ZHU Hongjian, YU Kun, QIAO Peng, JU Liting, XIAO Lei
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 614-636.   DOI: 10.7523/j.ucas.2021.0084
    Abstract407)      PDF(pc) (20326KB)(376)       Save
    Youjiang basin (Nanpanjiang basin) experienced a complex tectonic evolution of Paleozoic prototype basin-superimposed basin, and finally, it appears as a residual basin. According to the tectonic setting, sedimentary series and magmatic rocks, the evolution of Youjiang basin after Caledonian movement can be divided into six stages:intracontinental extensional basin (early rift valley) evolution stage (D21-D12), oceanic extensional basin (rift ocean basin) evolution stage (D2-T1), ocean basin extinction and foreland flexure basin evolution stage (T21-T13), fold orogeny and post collisional extension stage (T13-J1), NW trending compression orogeny stage (J2-K21), and local extension stage (K31-E). There are a large number of Carlin-type gold deposits in the basin, and most ore bodies occur in thrust-fold belts. The Carlin-type gold deposit has multi-stage metallogenic characteristics, large-scale mineralization mainly began in the compressive background and continued to the post orogenic extension stage, and there are two concentrated metallogenic periods. The first stage was formed in the evolution stage of foreland flexure basin related to collision orogeny to post collisional extension (235-193 Ma, Carlin-type gold deposit in the central and southern part of the basin). The mineralization in this stage was controlled by metamorphic hydrothermal fluids or hydrothermal fluids relate to magmatic melting which induced by the superposition of collision orogeny of the Yangtze Block and the Indochina Block and the subduction of the Paleo-Pacific plate to the Eurasian continent. The second stage was formed in the stage of NW trending compression orogeny to local extension (148-103 Ma, Carlin-type gold deposit in the whole Youjiang basin). The mineralization in this stage was mainly affected by the magmatic hydrothermal activities during the superposition and transformation of the pre-existing structures by the NW trending compression orogeny. Magmatic or metamorphic hydrothermal activities under extensional background before the Early Triassic has the effect of initial enrichment, and it has the effect of superimposed and reformation post mineralization after the Early Cretaceous. The ore-forming fluid of Carlin-type gold deposit has the characteristics of mixed sources. It is mainly metamorphic hydrothermal solution in the central and southern part of the basin, and mostly mixed source hydrothermal solution in the central part of the basin. While, the ore-forming fluid is mainly magmatic hydrothermal solution in the northern part of Youjiang basin. Through comparative analysis, it is considered that the ages obtained by different dating methods can represent the metallogenic age to a certain extent. And the combined application of multiple methods should be used to limit the metallogenic age of Carlin-type gold deposits.
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    Comparative study of “resource value” and “visitor perception” at national parks: a case study from Sichuan area of Giant Panda National Park
    REN Qingliu, YANG Zhaoping, HAN Fang, PU Yulin
    Journal of University of Chinese Academy of Sciences    2023, 40 (3): 333-342.   DOI: 10.7523/j.ucas.2021.0075
    Abstract384)      PDF(pc) (1801KB)(171)       Save
    National parks are the best case for the innovative development and practical application of Tourism human-land relationship theory. Nature education and ecological recreation is the important window to show the resources value of national park and the important way to build the harmonious human-land relationship. Displaying the value of resources through recreational activities and being perceived, inherited and transmitted by tourists is the process of realizing the value of resources in national parks. This paper analyzes the resource value characteristics and carrier elements of Sichuan Giant Panda National Park from four dimensions:geological value, ecological value, aesthetic value, and human value. The content analysis method is used to evaluate the tourists' perceived benefits and attention to the value of different types of resources. The IPA model is used to analyze the synergy state of "resources value-visitor perception". The results show that:1) There are great differences in tourists' perception of the value of different resource values. The order of tourists' perceived benefits is as follows:geographic value (55.42%) > ecological value (24.45%) > aesthetic value (17.62%) > human value (2.51%). The high frequency words show a significant "long tail" distribution feature, and the semantic network graph shows the pattern of "dual-core, multi-node"; 2) The tourists' perceived benefits of geographic value and ecological value have a relatively high degree of coordination with resource value, while tourists' awareness of human value is low, and their perception of aesthetic value is more superficial. It is necessary to further improve tourists' overall cognition of the scientific connotation of resource value. The results of this study can promote the formation of a virtuous cycle of "value perception-environmental awareness-ecological behavior", and provide an important decision basis for optimizing the nature education system in national parks.
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    Relationships between ΛφBV and BV(q,δ)
    GE Ajun, WANG Heping, YAN Dunyan
    Journal of University of Chinese Academy of Sciences    2023, 40 (6): 721-725.   DOI: 10.7523/j.ucas.2022.035
    Abstract365)      PDF(pc) (819KB)(259)       Save
    In this note, we obtain the sufficient and necessary conditions for the inclusions ΛφBVBV(q,δ), and BV(q,δ)⊂ΛφBV is false when φ satisfies the Δ2 condition.
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    Screening method of remote sensing image region covering dataset
    YAN Xuejing, LIU Wei, LIU Shibin, DUAN Jianbo, XIA Wei
    Journal of University of Chinese Academy of Sciences    2023, 40 (4): 523-530.   DOI: 10.7523/j.ucas.2022.006
    Abstract356)      PDF(pc) (6362KB)(263)       Save
    With the development of remote sensing satellite technology, the temporal and spatial resolution of remote sensing data has been continuously improved, showing the trend of big data and massive quantification, which has brought challenges to the screening of remote sensing data. Traditional remote sensing data retrieval often has the problem of large amount of query results and high overlap. It requires manual data selection, which is inefficient and low in accuracy. Therefore, how to quickly and accurately find the required data from a large number of remote sensing images is a problem that needs to be solved urgently. In this paper, a remote sensing data screening algorithm based on area coverage is used to divide the target area into non-overlapping fragments using the effective range of images. A normalized mathematical calculation model is established based on the number of fragments contained in the image, imaging time, and cloud cover. The model obtains a comprehensive cost. An optimal image combination is selected according to the cost, which completely covers the target area. This paper confirms the effectiveness of the method through Landsat8 data, and improves the screening efficiency through parallel computing.
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    Asset selection based on high frequency Sharpe ratio and robust correlation coefficient
    ZHANG Shanhua, ZHANG Sanguo
    Journal of University of Chinese Academy of Sciences    2023, 40 (6): 834-842.   DOI: 10.7523/j.ucas.2022.039
    Abstract355)      PDF(pc) (4086KB)(188)       Save
    High frequency Sharpe ratio, a measure of return and risk, is commonly used in current portfolio construction method since it can avoid covariance matrix in high dimensional analysis. The newly proposed D-SEV measures the correlation between stock's return and high frequency Sharpe ratio index to further construct portfolio. However, there are some problems with the measure used in D-SEV, such as its lack of robustness and slow computational speed. In this paper, we propose to use a new correlation coefficient proposed by Sourav Chatterjee instead. The new correlation coefficient guarantee robustness, specifically it can reduce the impact of abnormal data on correlation, such as significant events that have a large impact on the asset prices. It is also extremely fast in its calculations. Extensive simulation demonstrate that new correlation coefficient outperforms D-SEV and other traditional methods in several different models. Actual Shanghai Securities Exchange (SSE) and Shenzhen Securities Exchange (SZSE) stock market data for 2019 and 2020 also show that the assets selected by new correlation coefficient earns 8% more excess annualized return than D-SEV, while it also owns a higher Sharpe ratio.
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    Local observation reconstruction for Ad-Hoc cooperation
    CHEN Hao, YANG Likun, YIN Qiyue, HUANG Kaiqi
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 117-126.   DOI: 10.7523/j.ucas.2022.028
    Abstract354)      PDF(pc) (9211KB)(277)       Save
    In recent years, multi-agent reinforcement learning has received a lot of attention from researchers. In the study of multi-agent reinforcement learning, the question of how to perform ad-hoc cooperation, i.e., how to adapt to a changing variety and number of teammates, is a key problem. Existing methods either have strong prior knowledge assumptions or use hard-coded protocols for cooperation, which lack generality and can not be generalized to more general ad-hoc cooperation scenarios. To address this problem, this paper proposes a local observation reconstruction algorithm for ad-hoc cooperation, which uses attention mechanisms and sampling networks to reconstruct local observations, enabling the algorithm to recognize and make full use of high-dimensional state representations in different situations and achieve zero-shot generalization in ad-hoc cooperation scenarios. In this paper, the performance of the algorithm is compared and analyzed with representative algorithms on the StarCraft micromanagement environment and ad-hoc cooperation scenarios to verify the effectiveness of the algorithm.
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    Prediction of landslide displacement based on EEMD-Prophet-LSTM
    WANG Zhenhao, NIE Wen, XU Hanhua, JIAN Wenbin
    Journal of University of Chinese Academy of Sciences    2023, 40 (4): 514-522.   DOI: 10.7523/j.ucas.2022.002
    Abstract352)      PDF(pc) (10558KB)(272)       Save
    For the unsteady process of step-type landslide displacement, a method combining ensemble empirical mode decomposition (EEMD), Prophet, and long short time memory network (LSTM) to predict landslide displacement is proposed. The displacement data of Baishuihe landslide was taken as examples. The displacement time series was decomposed into residual(RES) and several intrinsic mode functions(IMF) by EEMD. The superimposition of IMFS which included periodic factors and random factors was considered as a volatility item, and the RES was regarded as a trend term. The trending term was fitted by the Prophet and the the volatility term was predicted by LSTM. The addition of the two prediction results was the predictied value of the landslide displacement. The results show that the coefficient of determination(R2) of the EEMD-Prophet-LSTM model is above 0.98 for Baishuihe landslide displacement prediction, which is better than traditional machine learning methods such as support vector machine and artificial neural network. Moreover, the prediction accuracy R2 of this method for each monitoring point of the Bazimen landslide is also above 0.96, which proves the applicability of this method.
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    Design of object detection and weak position location system base on coaxial dual-rotor drone
    FENG Hangtao, ZENG Shaofeng, ZHANG Lu, YANG Xu, LIU Zhiyong
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 701-709.   DOI: 10.7523/j.ucas.2022.017
    Abstract346)      PDF(pc) (10908KB)(237)       Save
    Unmanned aerial vehicles (UAV) controlled by autonomous control algorithms often have greater advantages than manned aircraft in the execution of directional strikes and other dangerous tasks. When performing blasting tasks, the robustness of the UAV detection algorithm in different scenarios is often not guaranteed, which greatly affects the UAV's positioning of the target, thus reducing the success rate of the mission. In order to solve the above problems, the crossdomain-based object detection algorithm is used to improve the robustness of the UAV detection algorithm in different scenarios, and the online GPS clustering algorithm is used to improve the robustness of object positioning. At the same time, in view of the impact of the object blasting position on the blasting result, the system uses an algorithm for locating weak parts to improve the accuracy and success rate of blasting.
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    Nucleon resonances in γp→π-Δ++ photoproduction
    ZHU Yiming, YANG Fuzhong
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 35-41.   DOI: 10.7523/j.ucas.2021.0042
    Abstract338)      PDF(pc) (4263KB)(86)       Save
    The first measured high-precision data on the differential cross sections and polarization observable beam asymmetry Σ for the γp→π-Δ++ reaction from the LEPS collaboration are analyzed within a tree-level effective lagrangian approach. In addition to the t-channel π and ρ exchanges, the u-channel Δ exchange, the s-channel N exchange, and the interaction current that is required by the gauge invariance, the s-channel nucleon resonance exchanges are further taken into account to reproduce the data of LEPS. Numerical results show that, the data on Σ can not be well reproduced when no contributions from the s-channel resonance exchanges are introduced. Further analyses show that, by including the contribution from the resonance N(1860)5/2+, both the data on the differential cross sections and beam asymmetry Σ can be well reproduced.
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    SAR image change detection algorithm based on hierarchical fuzzy clustering and wavelet convolution neural network
    ZHANG Meng, PAN Zhigang
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 637-646.   DOI: 10.7523/j.ucas.2022.013
    Abstract333)      PDF(pc) (7162KB)(236)       Save
    Traditional synthetic aperture radar (SAR) image change detection methods have some problems, such as big impact by speckle noise, difficult to use deep information of the image, and low detection accuracy. To solve above problems, this paper presents an SAR amplitude image change detection algorithm based on convolution neural network and fuzzy clustering. Firstly, a hierarchical FLICM algorithm based on Gabor texture is used to pre-classify the difference images, and reliable training samples are automatically selected based on the pre-classification results without manual labeling. Then, a multiscale channel attention mechanism is introduced, and a MSCA_WCNN is used to complete the second classification, and the result of change detection is obtained. This algorithm extracts the different scale features of SAR images while suppressing the irrelevant feature channels to effectively utilize the image features. The wavelet convolution neural network achieves the denoising function while preserving the useful information of the image and enhances the robustness of the algorithm. The comparison experiments using real spaceborne SAR image data show that the algorithm has high detection accuracy and the effectiveness of the algorithm is verified.
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    Identification of core rumor spreaders in online social networks based on multi-stage deep model
    LI Yuan, ZHANG Qi, ZHU Jianming, JIAO Jianbin
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 136-144.   DOI: 10.7523/j.ucas.2022.057
    Abstract329)      PDF(pc) (3614KB)(231)       Save
    Online social networks have become the disaster areas where rumors grow. It is of great significance to identify core rumor spreaders for rumor prevention and control. The traditional rumor control model is mainly based on the dynamics of rumor propagation, and it is mainly focused on in-event or post-event control. In view of the timeliness of rumor control, this paper proposes a multi-stage graph convolutional network based on multi-dimensional features (MSF-GCN) deep learning model to accurately locate core rumor spreaders as early as possible and block rumor diffusion from the source. This work compares the MSF-GCN method with other three baseline methods on rumor data set, and the experimental results verify that our method is more efficient.
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    Cause of thermal event moonquakes by thermos-elastic stress finite element models
    ZHANG Junce, HU Caibo, SHI Yaolin
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 50-64.   DOI: 10.7523/j.ucas.2022.045
    Abstract326)      PDF(pc) (14838KB)(283)       Save
    On the basis of the previous work, considering the solar heat absorbed by the lunar surface inward and the lunar thermal radiation heat released outward, as well as the nonlinearities of the thermodynamic parameters of the lunar soil related to the temperature and depth, we have developed a thermo-elastic coupled finite element parallel program suitable for the study of the temporal and spatial evolutions of the temperature, deformation, and thermal stress of the lunar soil, and have utilized the four sets of finite element models to investigate the effects of the characteristic thicknesses of the lunar soil on the temporal and spatial evolutions of the temperature, deformation and thermal stresses of the lunar surface. The computational results show that the temperature of the lunar surface varies periodically over one lunar day (29.5 Earth days), and the temperature of the equatorial lunar surface varies from 100 to 385 K, with the variation decaying exponentially with the increase of the depth, and the depth of influence reaches to about 50 cm. The temperature cyclic changes also cause the vertical displacement of the lunar surface to rise and fall, and the horizontal normal stress of the lunar surface in the form of compression and tension. In general, the horizontal stresses are compressed during the day and tensile during the night, with the fastest increase in tensile stress at 18:00 and the highest tensile stress at 06:00. The characteristic thickness of the lunar soil has a strong influence on the temporal and spatial distributions of the temperature and the horizontal positive stresses. The magnitude of thermal stresses may reach the tensile strength of the lunar surface. The fastest growth of tensile stress and the period of maximum amplitude coincide with the observed high frequency of thermal events on the lunar surface in the morning and evening.
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    Calculating the thermal stress of the moon in cooling process with 3-D viscoelastic model
    JIN Yimin, TAO Sha, SHI Yaolin
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 1-10.   DOI: 10.7523/j.ucas.2022.059
    Abstract325)      PDF(pc) (8323KB)(246)       Save
    Thermal stress of the moon due to cooling process is non-negligible in lunar evolution. We calculate the accumulation of thermal stress with 3-D viscoelastic model, and explore the influence of viscosity parameters on thermal stress through comparative experiments. Numerical results suggest that the thermal stress of lithosphere is utterly distinct from deep mantle. The lithosphere is under tangential compression that concentrates at the bottom of the crust because of unevenly distributed cooling rate and elastic strength; on the other hand, the accumulation and relaxation of thermal stress in deep mantle is balanced due to low viscosity, and the thermal stress is in a “hydrostatic” state, which is mainly controlled by the elastic surface. Under the assumption that viscosity of lunar lithosphere is greater than 1028 Pa·s, the tangential compressive stress in lithosphere accumulates to several hundreds of MPa in the present day, while the tensile stress in deep mantle reaches up to 100 MPa. Consequently, part of the shallow moonquake events can be explained by thermal stress. However, the focal mechanism of deep moonquakes is still unclear. We speculate that the tensile thermal stress in deep mantle helps to develop pore structures, and the melting layer provides pore fluid with high pressure, which reduces the fracture strength of mantle medium.
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    Design and implementation of fuzzy extractor for PUF
    SONG Minte, HOU Kai, RU Zhanqiang, WANG Zhengguang, SONG Helun
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 127-135.   DOI: 10.7523/j.ucas.2022.054
    Abstract316)      PDF(pc) (7892KB)(268)       Save
    The physical unclonable function (PUF) implemented on SRAM and other schemes exists inherent demerit of poor reproducibility for environmental factors such as voltage changes and thermal noise. This disadvantage greatly restricts functional application in cryptography, communication and other fields. In this paper, a fuzzy extractor with large error correction capacity is designed to reconstruct the original data of SRAM by means of BCH codes (Bose-Chaudhuri-Hocquenghem Codes). The SRAM PUF chip applying this design is manufactured on the Hua Hong Grace 0.11 μm CMOS platform with area of 306 267 μm2. The original BCH code has a code length of 127 bits and an error correction capability of 27 bits, which achieves the practical requirements of PUF applications.
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    Multipath routing protocol for MANET based on flooding limiting
    WANG Xiaoxiang, WANG Mingliang, XU Huihui, QIN Ronghua
    Journal of University of Chinese Academy of Sciences    2023, 40 (5): 710-719.   DOI: 10.7523/j.ucas.2022.004
    Abstract310)      PDF(pc) (4736KB)(271)       Save
    Mobile ad hoc network (MANET) is widely used in emergency rescue scenarios because of its dynamic network reconfiguration. However, the dynamic topology of MANET causes routes to be easily broken and route reconstruction will occupy more network resources. To solve this problem, this paper proposed a new multipath routing protocol FLMP based on flooding limiting and multiple measurement functions. It uses the flooding limiting mechanism based on node mobility, combines local and global optimal ideas to construct routs, and uses multiple route measurement functions to select the optimal main route and backup route for data transmission. The simulation results show that the FLMP routing protocol can effectively reduce the number of routing breaks, ensure reliable data transmission, and significantly reduce overhead.
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    Continuity of the Lp-norm of the truncated Hardy-Littlewood maximal operator
    WU Jia, WEI Mingquan, YAN Dunyan
    Journal of University of Chinese Academy of Sciences    2024, 41 (1): 28-34.   DOI: 10.7523/j.ucas.2021.0073
    Abstract279)      PDF(pc) (894KB)(112)       Save
    This paper focuses on the continuity of Lp(Rn)→Lp(Rn)-norm of the truncated Hardy-Littlewood maximal operator Mba with two truncation parameters a and b. We first, respectively, present the left semi-continuity and right semicontinuity of ‖MbaLp(Rn)→Lp(Rn) with respect to θ=b/a, and then the continuity of ‖MbaLp(Rn)→Lp(Rn) is extended to infinity.
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