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2024, Vol. 41 No. 6

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15 November 2024

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    Continuity of truncated Hardy-Littlewood maximal function
    WANG Yidong, WU Jia, YAN Dunyan
    2024, 41 (6): 721-727.  DOI: 10.7523/j.ucas.2023.045
    Abstract ( 309 ) PDF (0KB) ( 0 )
    This paper focuses on the continuity of the truncated Hardy-Littlewood maximal function. We first show that the truncated Hardy-Littlewood maximal function is lower semi-continuous. Then by investigating the behavior of the truncated Hardy-Littlewood maximal function when the truncated parameter γ changes, we obtain an equivalent condition of the continuity of the truncated Hardy-Littlewood maximal function.
    Interval estimation for the process capability index under the inverse Rayleigh and log-logistic distributions
    MU Weiyan, JIA Xiaofang, XIONG Shifeng
    2024, 41 (6): 728-735.  DOI: 10.7523/j.ucas.2023.001
    Abstract ( 144 ) PDF (0KB) ( 0 )
    In this paper, we discuss the statistical inferential problem on an important process capability index CNpk under the inverse Rayleigh and log-logistic distributions. We construct the generalized pivotal quantities for CNpk, and subsequently the generalized confidence intervals proposed. Numerical results show that the proposed interval estimation performs better than the bootstrap method in terms of coverage rate and interval width.
    Numerical study of natural convection heat transfer from neck folds of the frill-neck lizard
    JIA Chongxi, WANG Hao, LIU Jie, LU Wenqiang
    2024, 41 (6): 736-745.  DOI: 10.7523/j.ucas.2022.078
    Abstract ( 316 ) PDF (0KB) ( 0 )
    In this paper, the physical modeling of frill-neck lizard, a reptile with special heat dissipation structure, was carried out, and the natural convection heat transfer properties of it were numerically studied. It was found that there was only one maximum heat transfer coefficient in the range of 45°-85°, which was obtained at around 65° for the simulation of different field angle adjustments of frill-neck lizard neck fold. At the same time, by changing the size of frill-neck lizard neck fold, it was also observed that there was a unique maximum convection heat transfer coefficient in the range of 6.3≤ L0/d ≤6.6. In addition, the field angle and area corresponding to the maximum heat transfer rate were close to the natural state of Australian subspecies. Therefore, it can be inferred that the evolution direction of frill-neck lizard neck fold may be beneficial to improving the natural convection heat transfer rate. Hence, the natural convection between frill-neck lizard and external environment may be considered as an important reason affecting the evolution direction of Chlamydosaurus kingii neck fold.
    Experimental study of MHD effect of phase change heat transfer in metals under the influence of a strong magnetic field
    CAI Zhiyang, MENG Xu, ZHANG Dengke, WU Xi, WANG Zenghui
    2024, 41 (6): 746-754.  DOI: 10.7523/j.ucas.2023.021
    Abstract ( 286 ) PDF (0KB) ( 0 )
    As a highly efficient heat transport medium, the study of the melting and heat transfer characteristics of metallic fluids in phase change processes under magnetic fields is of great importance for industrial processes such as fusion reactors, electromagnetic metallurgy, and additive manufacturing. In this paper, the melting process of metallic gallium under a strong magnetic field was studied by building a comprehensive experimental system for heat transfer through phase change of metal, and the heat transfer characteristics of metallic gallium melting under the action of a magnetic field were obtained. The dynamic average distance of the heated wall from the phase interface during melting instead of the fixed characteristic length was used to study the variation of the relative strength of convective heat transfer and thermal conductivity with Fourier number (Fo) during melting. The results show that: under a small Hartmann number (Ha), the melting has a melting-promoting effect at the early stage and is inhibited at the later stage; under a large Hartmann number the magnetic field has an inhibiting effect on the convection during the melting of gallium metal, and the melting process shows a laminar and uniform advance. The magnetic field reduces the height of the dominant zone of thermal conductivity at the bottom of the cavity during the melting process and suppresses temperature fluctuations during the melting process, resulting in a uniform temperature distribution during the melting process.
    Comparison study on classification accuracy of 11 common water indices based on Landsat 8 OLI images
    LI Longjie, YANG Yonghui
    2024, 41 (6): 755-765.  DOI: 10.7523/j.ucas.2023.088
    Abstract ( 431 ) PDF (0KB) ( 0 )
    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.
    Measurement and influencing factors of open economy in border cities: taking Hunchun City, China as an example
    LIAO Maowei, ZHANG Pingyu, LI Yuxin
    2024, 41 (6): 766-775.  DOI: 10.7523/j.ucas.2023.026
    Abstract ( 219 ) PDF (0KB) ( 0 )
    Based on the concept connotation of open economy, this paper builds the evaluation index system for open economy in border cities from opening to the outside world and opening to the interior. Taking Hunchun City, China as an example, the entropy method, coupling coordination model and obstacle degree model were used to explore the development process, characteristics and influencing factors of open economy in Hunchun from 2001 to 2020. The results are as follows: 1) The economic openness of Hunchun showed a trend of fluctuating upward, and the opening process has experienced three stages: slow development (2001-2008), rapid development (2009-2014) and stable development (2015-2020). Opening to the outside world and the interior have gradually transitioned from barely coordinated to well-coordinated. 2) During the study period, the obstacle degree of opening to the outside world showed a trend of fluctuating upward, while the obstacle degree of opening to the interior showed a trend of fluctuating downward. Opening to the outside world is the critical factor that restricts the opening development of Hunchun at its current stage. The main obstacle factors include degree of dependence on foreign trade, the number of newly approved foreign-funded enterprises, actual utilization of foreign capital and investment promotion.
    Lightweight network for fast ship detection in SAR images
    ZHOU Wenxue, ZHANG Huachun
    2024, 41 (6): 776-785.  DOI: 10.7523/j.ucas.2023.017
    Abstract ( 393 ) PDF (0KB) ( 0 )
    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.
    The improved SLM algorithm used in hybrid beamforming architecture
    XIAO Disheng, HU Shicheng, QIAN Hua, KANG Kai, LI Mingqi
    2024, 41 (6): 786-793.  DOI: 10.7523/j.ucas.2023.015
    Abstract ( 204 ) PDF (0KB) ( 0 )
    In the massive multi-input multi-output system, the peak-to-average power ratio (PAPR) is one of the factors which greatly affect the performance of the transmitter. The existing PAPR reduction methods are based on the fully-digital architecture, which can not effectively reduce the PAPR of signal at the transmitting antennas in the hybrid beamforming architecture. To address this problem, an improved selective mapping (SLM) method is proposed, which adopts independent phase rotations to the initial input signal and then calculates the PAPR at the transmitting antennas and finally transmits the sequence with minimum PAPR. Besides, the upper bound and lower bound of PAPR at the transmitting antennas are analyzed. Theoretical analysis and simulation results suggest that the proposed improved SLM can effectively reduce the PAPR at the transmitting antennas in the hybrid beamforming architectures.
    Water image extraction algorithm based on improved Gaussian mixture model and graph cut model
    BAO Linan, LYU Xiaolei
    2024, 41 (6): 794-802.  DOI: 10.7523/j.ucas.2023.028
    Abstract ( 214 ) PDF (0KB) ( 0 )
    Synthetic aperture radar (SAR) has the characteristics of all-day and all-weather imaging, wide observation range, and short mapping period, which make it highly advantageous in water extraction. However, existing algorithms for lake extraction are easily affected by the surrounding environment of lakes and noise interference, resulting in low operational efficiency. Therefore, this paper proposes a detection method that combines an improved Gaussian mixture model (GMM) with graph cut model (GCM). First, the two-level Otsu threshold method is used to obtain the initial segmentation map of the lake, and the calculated parameter set is used as the initial parameter of the GMM. The expectation maximum algorithm (EM) is employed to obtain the optimal parameters of the GMM iteratively. The experimental results demonstrate that the more accurate the initial parameters, the clearer the outline of the water body. The introduction of the two-level Otsu algorithm not only greatly reduces the times of iterations of the EM algorithm, but also effectively enhances the running speed of the algorithm in combination with downsampling in preprocessing. In addition, the energy function of the graph cut model enables accurate lake boundaries to be obtained without requiring any post-processing.
    Multi-satellite cooperative observation method based on area target gridding
    ZHENG Qicun, YUE Haixia, LIU Dacheng, LI Hua, REN Mingshan, JIA Xiaoxue
    2024, 41 (6): 803-809.  DOI: 10.7523/j.ucas.2023.019
    Abstract ( 261 ) PDF (0KB) ( 0 )
    By analyzing the constraints of using multiple SAR satellites to observe a specific large area target, the constraint satisfaction model is established to maximize the observation profit within a given mission time horizon. To improve the global search capabilities of the traditional tabu search algorithm, an improved tabu search algorithm with the variable neighbourhood is proposed. In implementing the algorithm with variable neighbourhood, the area target is gridded to dynamically generate observation patterns, and the observation rates are calculated for each pattern. Compared to the traditional tabu search algorithm, the variable neighbourhood tabu search algorithm proposed in this paper increases the observation profit by more than 8% while maintaining the same computational burden.
    Field dynamic small object detection network based on double frame fusion
    ZHAO Xiaohan, ZHANG Zebin, LI Baoqing
    2024, 41 (6): 810-820.  DOI: 10.7523/j.ucas.2023.008
    Abstract ( 278 ) PDF (0KB) ( 1 )
    Detecting dynamic small objects in complex environments in the field remains a challenging problem for defense and military applications due to factors such as more background interference in the field surveillance sensing systems, fewer pixels of small targets, and the lack of relevant open datasets. In order to solve this problem, a YOLOv5-based object detection network with double frame feature fusion (YOLO-DFNet) is proposed. Firstly, a double frame feature fusion module(D-F fusion) is introduced to process the adjacent frame features from the backbone network, calculating attention in channel, time, and space dimensions successively, to extract motion features. Secondly, a temporal trapezoidal fusion network based on an attention mechanism(TTFN_AM) is designed between the neck network and the detection head to focus on dynamic objects within receptive fields of different sizes, thereby improving the detection effect of small objects with large displacement. The experimental results on field motion small object dataset (FMSOD) show that the mean average precision (mAP) on different IoUs of the proposed YOLO-DFNet is 3.9 percentage points higher than that of YOLOv5, and also outperforms other object detection models such as Tph-YOLOv5 and YOLOv7.
    Detection method and characterization of ramp events of wind speed and wind power based on swinging door algorithm
    LIANG Zhi, ZHANG Zhe, SHI Yu, LIU Lei
    2024, 41 (6): 821-829.  DOI: 10.7523/j.ucas.2023.014
    Abstract ( 344 ) PDF (0KB) ( 10 )
    The ramp event of wind speed is a large increase or decrease in wind speed within a short period, causing a significant change in wind farm power, affecting the safe operation of the grid and even triggering accidents such as frequency reduction and voltage collapse. This paper selects the simultaneous data of wind turbines and meteorological towers in wind farms, identifies the ramp events by the swinging door algorithm (SDA), analyzes the duration, magnitude and change rate of the ramp events, and discusses the influence of mountainous terrain on them. In this paper, the recognition algorithm of the ramp event of wind speed and power is designed based on the SDA, and the algorithm parameters are set as follows: the time threshold 4 h, wind speed threshold 6 m·s-1, and power threshold 1 000 kW. For the recognition of ramp events in other wind turbines, this paper suggests using 2/3 value of the difference between rated wind speed and cut-in wind speed as the wind speed threshold parameter, and 2/3 value of rated power as the power threshold parameter. The terrain influence on the ramp event is significant, and the ramp event is more related to the altitude and average wind speed at the turbine, and the time proportion of the ramp event under different terrain ranges from 6.5% to 9.8%, with the average value of 7.8%.
    A framework of graph classification with self-supervised heterogeneous graph neural network
    YUAN Ming, ZHAO Tong
    2024, 41 (6): 830-841.  DOI: 10.7523/j.ucas.2023.048
    Abstract ( 271 ) PDF (0KB) ( 0 )
    Graph data exists widely in various forms, and the tasks of graph classification have great significance for many problems. However, the tasks of graph classification still face many challenges, including how to make full use of the semantic information contained in the graph structures, and how to further reduce the computational complexity and the cost of obtaining labels. In this paper, a construction method of a hyper-node heterogeneous network is proposed for the first time, along with a new framework, GChgnn, which can be applied to graph classification. The GChgnn framework achieves the following goals through the introduction of a double-view graph representation mechanism and self-supervised contrastive learning: 1)measuring the similarity between the objectives of the large-scale graph classification tasks; 2)inspired by the graph matching methods, improving the accuracy of similarity measurement by the cross-graph idea, and making up for the lack of the explicit expression of graph embedding; 3)avoid the need to design complicated convolution and pooling operators in the network. After testing on some public datasets, the framework outperforms other existing methods.
    Vulnerability exploitability assessment method based on network environment
    ZHENG Jinghua, KAI Shaofeng, SHI Fan
    2024, 41 (6): 842-852.  DOI: 10.7523/j.ucas.2023.037
    Abstract ( 171 ) PDF (0KB) ( 0 )
    The common vulnerability scoring system is the most widely used vulnerability evaluation method, but its evaluation results tend to be the harmfulness of the vulnerability itself, ignoring the network environment factors. In view of the above problems, we propose a network environment-oriented vulnerability exploitability assessment method. Based on the experience of group experts, using statistical methods to select vulnerability attributes, the vulnerability exploitability assessment metric system is constructed. And combined with the target environment attributes, this method can evaluate the vulnerability exploitability based on the K-nearest neighbor (KNN) algorithm. This method performs accurate and intelligent assessment of known and unknown vulnerabilities, integrating the impact of the target environment and reducing the reliance on expert experience. At last, we validate the method through experiments. Our method provides a scientific decision-making basis for network security protection measures.
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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
    Abstract1597)      PDF(pc) (727KB)(17334)       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
    Abstract599)      PDF(pc) (9359KB)(15135)       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
    Abstract3248)      PDF(pc) (1045KB)(6650)       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
    Abstract2413)      PDF(pc) (154KB)(6192)       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
    Abstract2881)      PDF(pc) (832KB)(5655)       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
    Abstract2313)      PDF(pc) (1120KB)(5231)       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
    Abstract3429)      PDF(pc) (268KB)(4689)       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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    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
    Abstract2847)      PDF(pc) (820KB)(4421)       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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    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
    Abstract1679)      PDF(pc) (173KB)(4204)       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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    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
    Abstract2558)      PDF(pc) (1138KB)(4133)       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
    Abstract3770)      PDF(pc) (1395KB)(3932)       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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    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
    Abstract902)      PDF(pc) (1257KB)(3920)       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.

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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
    Abstract2695)      PDF(pc) (1540KB)(3817)       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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    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
    Abstract2500)      PDF(pc) (929KB)(3796)       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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    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
    Abstract1093)      PDF(pc) (1223KB)(3755)       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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    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
    Abstract2133)      PDF(pc) (816KB)(3590)       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
    Abstract1921)      PDF(pc) (832KB)(3568)       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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    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
    Abstract2744)      PDF(pc) (833KB)(3408)       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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    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
    Abstract1953)      PDF(pc) (152KB)(3397)       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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    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
    Abstract545)      PDF(pc) (574KB)(3317)       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.

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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
    Abstract1148)      PDF(pc) (2927KB)(2056)       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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    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
    Abstract704)      PDF(pc) (4937KB)(1745)       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.
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    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
    Abstract669)      PDF(pc) (10322KB)(695)       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.
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    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
    Abstract593)      PDF(pc) (6043KB)(898)       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.
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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
    Abstract573)      PDF(pc) (3614KB)(615)       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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    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
    Abstract559)      PDF(pc) (10147KB)(660)       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.
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    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
    Abstract551)      PDF(pc) (5608KB)(836)       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.
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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
    Abstract523)      PDF(pc) (9211KB)(561)       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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    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
    Abstract522)      PDF(pc) (12585KB)(455)       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.
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    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
    Abstract521)      PDF(pc) (841KB)(672)       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).
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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
    Abstract512)      PDF(pc) (7892KB)(679)       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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    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
    Abstract503)      PDF(pc) (1144KB)(531)       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.
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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
    Abstract502)      PDF(pc) (4263KB)(247)       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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    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
    Abstract499)      PDF(pc) (20364KB)(523)       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.
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    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
    Abstract498)      PDF(pc) (12970KB)(422)       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.
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    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
    Abstract491)      PDF(pc) (5008KB)(732)       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.
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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
    Abstract491)      PDF(pc) (14838KB)(445)       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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    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
    Abstract490)      PDF(pc) (21553KB)(799)       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.
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    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
    Abstract487)      PDF(pc) (15706KB)(512)       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.
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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
    Abstract483)      PDF(pc) (8323KB)(511)       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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