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

### Current Issue

2023, Vol. 40 No. 1

15 January 2023

### Host

University of Chinese Academy of Sciences

### Journal

• Current Issue
• Latest
• Archive
• Research Articles
Limiting property of distribution function in Lorentz space
WU Di, DENG Yangkendi, YU Dandan, YAN Dunyan
2023, 40 (1): 1-5.
Abstract ( 265 ) PDF (0KB) ( 0 )
In this paper, we give a novel proof for the following equality
$\mathop {\lim }\limits_{\alpha \to {0^ + }} {\alpha ^P}{d_f}(\alpha ) = \mathop {\lim }\limits_{\alpha \to \infty } {\alpha ^P}{d_f}(\alpha ) = 0$
for fLp,q(X,μ) with 0<p<∞, and 0<q<∞.We also prove that the function αp can not be improved for some sense. When q=∞, the above equality does not hold.
Bonnet surfaces with constant Gauss curvature
LI Miaomiao, WU Yingyi
2023, 40 (1): 6-11.
Abstract ( 230 ) PDF (0KB) ( 0 )
A surfce in Euclidean 3-space $\mathbb{R}$3 is called Bonnet surface if it admits a nontrivial(not the restriction on a surface of rigid motions) one-parameter families of isometric immersions which preserve the mean curvature. Chen and Peng got the ODE of a Bonnet surface. Using this ODE, we give another proof of Colares-Kenmotsu theorem.
Variable selection method for high-dimensional survival error-in-variable data
ZHANG Jiarui, WU Yaohua
2023, 40 (1): 12-20.
Abstract ( 177 ) PDF (0KB) ( 0 )
Analysis with censored survival data plays an important role in high-dimensional sparse modeling. Much theoretical and applied work is based on clean data. However, we often face corrupted data with missing data or error-in-variable data and as a result analysis on error-in-variable data is more useful. While in the known literature, relatively few work has been done on high-dimensional survival data variable selecting with measurement error. In this situation, we propose a new method to select variables in high-dimensional additive hazards model with error-in-variable data, which combines the pseudoscore function and the nearest positive semi-definite projection. Our numerical studies and real data analysis show that the method has good performance and can select the nonzero coefficients successfully.
Numerical simulation of forced convection driven by high-frequency traveling magnetic field for low conductivity liquids
GUO Shengrong, NA Xianzhao, LIU Runcong, LI Yong, ZHANG Xiangping, DONG Haifeng, DAI Xiaotian, GONG Xiufang, WANG Xiaodong
2023, 40 (1): 21-28.
Abstract ( 63 ) PDF (0KB) ( 0 )
High frequency traveling magnetic field generated by two sets of coil can be applied as a new driving method for low conductivity liquid, therefore study on its mechanism is of great significance. In this paper, a numerical model is established to study the effects of current, frequency, phase difference， and coil distance on the flow field and temperature field of the low conductivity liquid being driven, so as to obtain the optimal electrical parameters configuration and coil structure for the driving task. The simulation results show that the average velocity and temperature of the fluid are linearly correlated with the magnitude and frequency of the current. The average velocity is maximized when the phase difference between the coils is near 90o. Depend on the coil distance, the flow field is either two vortices or a single large circulation. Particle image velocimetry (PIV) is also used to measure the flow field distribution of NaCl solution driven by high frequency traveling magnetic field, which verifies the feasibility and effectiveness of the driving method.
Trend analysis of ecohydrology research of Yellow River Basin
LI Tong, CUI Lizhen, YANG Yaqian, SONG Xiufang, TANG Li, CUI Xiaoyong, HAO Yanbin, WANG Yanfen
2023, 40 (1): 29-38.
Abstract ( 222 ) PDF (0KB) ( 0 )
The Yellow River Basin is a critical economic corridor for the implementation of the Belt and Road initiative. Maintaining the ecological health of the Yellow River is important for both the national social-economic development and ecological security. However, due to human activities and climate change, the Yellow River Basin has experienced ecological crises, such as degradation of vegetation in the upper reaches, sharp reduction of water and sand in the middle reaches, water shortage in the lower reaches, and retreat of the estuarine delta. This has seriously restricted the high-quality development of the Yellow River Basin and the process of ecological civilization in China. This study uses 5 190 related literature and 145 781 references in the Web of Science (WOS) database during 1990-2020 as the research sample. By scientometric and visual knowledge network methods, it analyzes the literature output pattern, keyword co-occurrence network, and future development of hydrology research in Yellow River Basin. Specifically, it quantifies and visualizes the current status, main institutions, academic journals, high-producing authors, and hot themes of the research at a multi-dimensional and deep level. Thus, this study aims at facilitating relevant researchers to get a panorama view, so as to focus the directions of ecohydrological research of the Yellow River Basin.
Atmospheric VOCs and their contribution to O3 and SOA formation in summer of Huairou District, Beijing City
ZHOU Bi, HU Jun, QI Yixuan, ZHANG Lijia, HUO Peng, ZHANG Yuanxun, ZHANG Yang, WANG Shulan
2023, 40 (1): 39-49.
Abstract ( 164 ) PDF (0KB) ( 0 )
In order to study the pollution characteristics and sources of volatile organic compounds (VOCs) and their environmental impact, 99 VOCs in Huairou District of Beijing were monitored online in summer 2016. During the observation period, the average concentration of VOCs was 20.02×10-9, among which alkanes accounted for the highest proportion of 38.48%, followed by oxygenated volatile organic compounds (OVOCs) (28.28%), halogenated hydrocarbons (12.89%), and halogenated hydrocarbons, aromatic hydrocarbons, olefins and alkynes and acetonitrile for a smaller percentage. The average hourly ozone formation potential of the initial VOCs was 157.03μg·m-3 and the major contributors were OVOCs, while alkenes and aromatics, aromatics were the major contributors to secondary organic aerosol formation potential. Seven sources were identified by the PMF model, including background and combustion sources, industrial sources, diesel vehicle emissions, gasoline vehicle emissions oil and gas volatilization, natural sources, and organic solvent use. The results from backward trajectory show that, in addition to local emissions, Hebei, Henan， and Shandong provinces have major contributions to Beijing VOCs pollution, while Tianjin City, Liaoning Province, and Inner Mongolia Autonomous Region also have some contributions.
Research on geographical factors of location of beacon towers of the Great Wall of Han Dynasty: a case study of Yumen City
SUN Ruiqi, LUO Lei, WANG Xinyuan, YAO Ya, HUANG Wenjiang, DONG Yingying, LIAN Yi
2023, 40 (1): 50-58.
Abstract ( 143 ) PDF (0KB) ( 0 )
The Great Wall of Han Dynasty is the most important ancient defense system in the desert region of Northwest China with beacon towers standing in great numbers. In the Han dynasty with limited economic conditions and arid areas with adverse natural conditions, how spatial location of beacon towers played a role in agriculture and military is of great significance for understanding the past human-land relationship. However, current domestic researches are mostly qualitative from the perspective of history and archaeology which is difficult to restore the spatial cognition and technology in the ancient environment without quantitative results. Taking Yumen City, Gansu Province as an example, this paper introduced spatial analysis and statistical methods including point pattern analysis, spatial correlation test, Monte Carlo simulation to quantitatively test the sensitivity of factors that probably affect the spatial distribution of beacon sites. Two types of factors, natural environmental and human settlement, were tested, which further summarized the law of spatial layout of beacon towers. Results indicated that the elevation showed sensitivity in the range of 1250-1500m, while the nearest distance to water showed sensitivity in the range of 0-1535m. The slope factor was sensitive between 2.5°-8°, and the aspect was sensitive in the range of 70° southeast to 60° southwest. The city sites were also sensitive predictors within a radius of about 2-20km centered on themselves. Analysis of the results indicated that the beacon towers along the Great Wall optimized the cost and utility of the military intelligence transmission between the front and the rear city barrier while guaranteeing the visibility of the front line. Additionally, the environment for human settlements at the site was considered by choosing oases with flat terrain and sufficient water sources, confirming its auxiliary functions such as farming and transportation, which comprehensively reflected the advanced geospatial cognition and technology in the Han Dynasty.
Coupling analysis of energy efficiency and structural upgrade of manufacturing in Jiangsu Province
JIN Tingting, DUAN Xuejun, ZOU Hui
2023, 40 (1): 59-68.
Abstract ( 85 ) PDF (0KB) ( 0 )
The adjustment of regional industrial structure is an important way to improve energy efficiency. This paper evaluates the energy efficiency and structure up-grade index of manufacturing industry in prefecture-level cities of Jiangsu Province from 2006 to 2016 by constructing energy efficiency index, using up-grade index and coupling degree model. In addition, it calculates the coupling degree between energy efficiency and structure up-grade index, and divides the coupling types. Moreover, the structural characteristics of manufacturing industry in different coupling areas are analyzed. As a result, it shows that: 1)The energy efficiency is high in the east and low in the west and differentiated between the north and the south as a whole. In addition, the areas with high energy efficiency are mainly distributed in Nantong, Yancheng, and Suqian. At the same time, the areas with low energy efficiency are distributed in Huai’an, Lianyungang, and Xuzhou. 2)The bipolar pattern of manufacturing structure up-grade index in Nanjing-Suzhou is significant, and the overall level of the southern region is higher than that of the northern region. 3)The manufacturing energy efficiency and industrial structure in the study area are at the primary coupling coordination level as a whole, while Nantong and Yancheng are highly coupled areas. 4)Three kinds of coupling areas are divided according to the coupling relationship between energy efficiency and structural advanced degree of manufacturing industry in each city. The result shows that low energy efficiency-low manufacturing advanced degree region has a relatively large proportion of low added value and high energy consumption manufacturing sector, which is the key area to optimize the industrial structure and improve the efficiency of energy resources.
Spatial equity of healthcare resource in Xinjiang
FU Runde, ZHANG Xinhuan, YANG Degang
2023, 40 (1): 69-78.
Abstract ( 208 ) PDF (0KB) ( 0 )
The spatial equity of medical and healthcare resource help to improve social equity, increase residents’ happiness, and achieve the goal of “equal access to public services”. Based on OpenStreetMap dataset and Python scripts, extending accessibility calculation method to a large area, this study explored the spatial equity characteristics and influencing factors of medical and healthcare resource of Xinjiang Uygur Autonomous Region. The results indicate that: 1) From a demographic perspective, the equity of medical resource allocation in Xinjiang tends to be further improved; 2) On basic medical services, only 38.5% settlements-distance costs of nearest medical institutions are within 5km, and 20.1% beyond 10km. And there are significant differences in the equity of medical resource allocation in both cities and counties. The spatial allocation of basic medical services in some regions needs to be further optimized, especially in some border counties; 3) Even, some settlements have no medical institutions within 120km, having a shortage of basic medical services. And, there is significant spatial imbalance between rural area and city area; 4) Average distance costs of nearest tertiary A-level hospital of all settlements is 70.05km. Access to tertiary A-level hospital medical services has a large gap between different areas; 5) At present, the spatial equality of Xinjiang is mainly influenced by the construction of professional medical team and regional economic development.
VLBI polarization study of compact radio sources 0400+258
LI Yuhang, ZHANG Haiyan, CHEN Rurong, CHEN Tianlu
2023, 40 (1): 79-83.
Abstract ( 99 ) PDF (0KB) ( 0 )
Using the very long baseline array, we perform the double-band polarization observations of the compact radio source 0400+258 at 5 GHz and 8 GHz. We present its mas-resolution total intensity maps and, for the first time, its polarization maps at 5 GHz and 8 GHz frequency bands. The source 0400+258 displays one-sided core-jet structure, and the polarization emission is firmly detected in a region near the core. Besides, by fitting the polarization maps at four frequencies, the mas-scale rotation measure of the source is obtained for the first time. After removing the rotation measure, the intrinsic magnetic field of the source is acquired, which demonstrates that the magnetic field direction is roughly parallel to the direction of the jet.
A new method of moving target velocity measurement and location based on FrFT
SHEN Xiaotian, ZHENG Mingjie
2023, 40 (1): 84-92.
Abstract ( 143 ) PDF (0KB) ( 0 )
In traditional, the way to measure the velocity of moving targets using FrFT(fractional Fourier transform) is based on 2D searching. The FrFT is calculated by traversing all angles and the optimal solution is the peak value of 2D plane. The method needs to trade off computational accuracy and computational complexity. In this paper, a new method of velocity measurement and location for moving targets is proposed. Firstly, the FrFT of two different angles and their projection are calculated. Then, the optimal rotation angle for moving target is calculated by using geometric relationship in the time-frequency plane. Finally, the FrFT under the optimal rotation angle is calculated, and velocity and position parameters of moving target are calculated. Moreover, static cluster can be suppressed if two angles for FrFT are symmetric about π. In general, the proposed method is faster and more accurate than the traditional method. The effectiveness and superiority of the method are verified by simulation and real data experiments.
Unmanned aerial vehicle image face recognition based on improved YOLOv3 and Facenet
GAO Jinfeng, CHEN Yu, WEI Yongming, LI Jiannan
2023, 40 (1): 93-100.
Abstract ( 306 ) PDF (0KB) ( 0 )
High precision face recognition based on unmanned aerial vehicle (UAV) images plays an important role in emergency rescue, suspect tracking, and other scenes. Deep learning convolutional neural network is widely used in the field of target detection and recognition because of its high accuracy and less human interference, which can be well applied to UAV image face recognition tasks. This paper explores the use of convolution networks for high-precision face recognition in UAV application scenarios, uses the improved YOLOv3(you only look once) for face detection of UAV images, and inputs the prediction boxes into the classic Facenet network to determine the target identity. Through experiments, this paper compares the detection effect of the improved YOLOv3, the original YOLOv3, and the MTCNN (multi-task convolutional neural network), and also compares the face recognition effect of the three models combined with Facenet. The experimental results show that: 1) compared with the original YOLOv3, the improved YOLOv3 improves the accuracy and recall rate, reduces the number of model parameters; besides, the phenomenon of missing and wrong detection of the improved YOLOv3 for UAV image is less than that of the original YOLOv3; moreover, the AP (average precision) of improved YOLOv3 is 9.49% higher than that of MTCNN, and the detection speed is about 3 times of MTCNN; 2) compared with the original YOLOv3+Facenet and MTCNN+Facenet, the improved YOLOv3+Facenet has stronger ability to distinguish faces and higher accuracy, and has stronger robustness to occlusion and blur.
Satellite imaging planning method based on improved cuckoo search
LI Xiaomu, TIAN Miaomiao, MA Guangbin, LIN Youming, CHENG Bo
2023, 40 (1): 101-108.
Abstract ( 144 ) PDF (0KB) ( 0 )
This paper proposes a satellite mission planning method of multi-satellite regional targets based on improved cuckoo search(ICS) in order to maximize the use of satellite resources. Firstly, the regional target is decomposed into strips based on a single satellite transit activity. Secondly, the satellite attitude constraints, sensor usage constraints, transit time constraints, cloud cover and illumination constraints during imaging, etc. are considered to establish a constraint satisfaction model, for which coding and updating strategies are designed. Finally, an improved cuckoo search algorithm, with nonlinear inertia weight, is used to solve the constraint satisfaction model. The results of the experiment show that compared with genetic algorithm (GA), the proposed algorithm in this paper has better convergence, higher target completion rate and stronger stability, which proves the effectiveness of the method proposed in this paper.
Satellite data receiving system fault location based on GAN sequence
WANG Zhengsheng, LI Yalin, ZHANG Hongqun
2023, 40 (1): 109-118.
Abstract ( 164 ) PDF (0KB) ( 0 )
Existing satellite data receiving system fault location methods suffer from the difficulty in obtaining expert knowledge. A generative adversarial network (GAN) sequence method called GANseq is proposed in this paper. According to the feature of fault propagation, the receiving system was first divided into M signal processing unit (SPU) to form a SPU sequence ranked by signal processing order (SPO). The fault location issue then was decomposed into ranked M anomaly detection sub-problems, where the mth sub-problem was the detection of the top m SPUs’ joint state. State parameters GANomaly-based detector was employed in each sub-problem, forming a GAN sequence. The detection results of this sequence on all sub-problems were analyzed to locate fault SPU. The experiment result from practical receiving system shows that GANseq can not only achieve fault location from data-driven perspective, but also reduce fault alarm rate and enhance accuracy level of fault location.
SSA-based WSN clustering routing algorithm for power transmission and substation scenarios
LIU Tiankai, LIU Hong, ZHENG Min, TAN Chong
2023, 40 (1): 119-127.
Abstract ( 107 ) PDF (0KB) ( 0 )
In view of the large number of sensors and the lack of networking capability on some power transmission and substation scenarios, a solution for using the relay nodes with high computing power to collect sensor information and networking is proposed. According to this solution, a clustering routing protocol algorithm (LEACH-WGR-SSA) that rotates the root node of the relay nodes -wireless gateway is proposed. The sparrow search algorithm is used to optimize cluster head election, which considers the remaining energy of nodes, the number of adjacent and location information for the election of the wireless gateway and cluster heads and joins the Levy flight strategy to avoid the algorithm falling into the local optimum. Simulation results shows that when 50% of the nodes die, the number of network survival rounds of LEACH-WGR-SSA is increased by 121.6%, 64.1%, and 6.5% compared with LEACH, LEACH-WGR, and LEACH-WGR-PSO, which balances energy consumption, prolongs the network life and improves optimization accuracy.
Brief Reports
Compressed sensing GNSS signal acquisition algorithm based on singular value decomposition
DENG Lele, ZHOU Fangming, ZHAO Lulu, LIANG Guang, YU Jinpei
2023, 40 (1): 128-134.
Abstract ( 133 ) PDF (0KB) ( 0 )
Signal acquisition is the key step of GNSS (global navigation satellite system) signal reception, and its search process is computationally expensive. Compressed sensing can reduce the amount of computation, but it has a certain impact on the acquisition performance. In order to improve the performance of compressed sensing acquisition algorithm, based on the sparsity of GNSS signal, a Gaussian measurement matrix based on singular value decomposition is constructed. Compared with the traditional Gaussian measurement matrix, the constructed measurement matrix has better performance of non-correlation and reconstruction. Simulation results show that compared with the traditional Gaussian compressed sensing acquisition algorithm, the acquisition probability of the improved algorithm is significantly improved in the case of lower signal-to-noise ratio.
Three dimensional MIMO wireless channel prediction based on phase space reconstruction
FENG Xinyu, LI Kai, REN Tianfeng, LI Hanhui, YANG Yang, ZHOU Mingtuo
2023, 40 (1): 135-143.
Abstract ( 66 ) PDF (0KB) ( 0 )
The fifth generation (5G) wireless communication network uses multiple input multiple output (MIMO) technology, which requires a lot of air interface resource estimation and feedback MIMO channel. Besides optimizing pilot, estimation and feedback design, channel fading prediction is also an effective way to save air interface resources. In this paper, phase space reconstruction method is used to study the phase space reconstruction parameters related to three-dimensional channel model, and a small sample online learning method based on empirical knowledge is proposed to predict MIMO channel coefficients and channel capacity. It is found that the wireless channel data is chaotic, and the phase space delay time and embedding dimension obey a certain distribution, so it can be set as the prior parameters of real-time prediction. Experimental results show that the prediction efficiency of the proposed method is about six times higher than that of the traditional ARMA method, and the minimum average error of channel capacity is 5.91%. Finally, the effectiveness of the phase space reconstruction method is verified by the measured data of an urban area, and the minimum average error of channel capacity prediction is 0.91%.
2022, Vol.39 No.6  No.5 No.4 No.3 No.2 No.1
2021, Vol.38 No.6  No.5 No.4 No.3 No.2 No.1
2020, Vol.37 No.6  No.5 No.4 No.3 No.2 No.1
2019, Vol.36 No.6  No.5 No.4 No.3 No.2 No.1
2018, Vol.35 No.6  No.5 No.4 No.3 No.2 No.1
2017, Vol.34 No.6  No.5 No.4 No.3 No.2 No.1
2016, Vol.33 No.6  No.5 No.4 No.3 No.2 No.1
2015, Vol.32 No.6  No.5 No.4 No.3 No.2 No.1
2014, Vol.31 No.6  No.5 No.4 No.3 No.2 No.1
2013, Vol.30 No.6  No.5 No.4 No.3 No.2 No.1
2012, Vol.29 No.6  No.5 No.4 No.3 No.2 No.1
2011, Vol.28 No.6  No.5 No.4 No.3 No.2 No.1
Analysis of Shanghai and Shenzhen stock market using Copula-VaR method
Hao Li-Xiang, Cheng Xi-Jun
2008, 25 (5): 682-686.
Abstract ( 1384 ) PDF ( 727KB ) ( 17031 )
Risk analysis of Portfolio is studied ,by comparing Copula functions and the traditional VaR methods,mixing copula is made. By backtesting ,the empirical research shows that mixing Copula method makes better VaR model .
Related Articles | Metrics
Shape-dependent effects of nanoceria on the activity of Pd/CeO 2 catalysts for CO oxidation
WANG Lei, MAO Junyi, YUAN Qing, HUANG Tao
2015, 32 (5): 594-604.
Abstract ( 416 ) PDF ( 9359KB ) ( 14901 )

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

Reference | Related Articles | Metrics
Advances in light field photography technique
NIE Yun-Feng, XIANGLI Bin, ZHOU Zhi-Liang
2011, 28 (5): 563-572.
Abstract ( 2664 ) PDF ( 1045KB ) ( 6155 )

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

Reference | Related Articles | Metrics
Upstream promoter sequences of Arabidopsis GH3 gene family
SUN Tao, CHAI Tuan-Yao, ZHANG Yu-Xiu
2010, 27 (6): 847-852.
Abstract ( 2083 ) PDF ( 154KB ) ( 5613 )

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

Reference | Related Articles | Metrics
Quality Evaluation for Three Textual Document Clustering Algorithms
LIU Wu-Hua, LUO Tie-Jian, WANG Wen-Jie
2006, 23 (5): 640-646.
Abstract ( 2665 ) PDF ( 832KB ) ( 5252 )
Textual document clustering is one of the effective approaches to establish a classification instance of huge textual document set. Clustering Validation or Quality Evaluation techniques can be used to assess the efficiency and effective of a clustering algorithm. This paper presents the quality evaluation criterions from outer and inner. Based on these criterions we take three typical textual document clustering algorithms for assessment with experiments. The comparison results show that STC(Suffix Tree Clustering) algorithm is better than k-Means and Ant-Based clustering algorithms. The better performance of STC algorithm comes from that it takes accounts the linguistic property when processing the documents. Ant-Based clustering algorithm’s performance variation is affected by the input variables. It is necessary to adopt linguistic properties to improve the Ant-Based text clustering’s performance.
Related Articles | Metrics
Investigation on the Preparation of μ-Sized PMMA Microspheres by the Dispersion Polymerization
WU Shao-Gui, LIU Bai-Ling
2006, 23 (3): 323-330.
Abstract ( 1904 ) PDF ( 1120KB ) ( 4382 )
The micron-grade PMMA microspheres with narrow size distribution were prepared by dispersion polymerization. The mechanism of the dispersion polymerization was discussed. The factors influencing both the size and size distribution of the microspheres including initial concentrations of the initiator, monomer, stabilizer, the polarity of the medium and the reaction conditions were studied. The results indicated that the size and size distribution of microspheres both increased with initial concentrations of initiator and monomer. Increasing the amount of the stabilizer resulted in decreasing size and narrowing size distribution of microspheres. Other factors such as the polarity of medium and the reaction temperature had great influences too. By controlling these factors, the desired-size monodisperse microspheres could be obtained.
Related Articles | Metrics
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.
Abstract ( 1466 ) PDF ( 173KB ) ( 4014 )

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

Reference | Related Articles | Metrics
XIA Lu-Ning, JING Ji-Wu
2009, 26 (4): 530-538.
Abstract ( 2728 ) PDF ( 268KB ) ( 3958 )

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

Reference | Related Articles | Metrics
A block Gram-Schmidt algorithm with its application
ZHAO Tao, JIANG Jin-Rong
2009, 26 (2): 224-229.
Abstract ( 2416 ) PDF ( 820KB ) ( 3857 )

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

Reference | Related Articles | Metrics
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.
Abstract ( 2364 ) PDF ( 1138KB ) ( 3781 )
A design of high resolution camera system based on DALSA’ s CCD evaluation kit EKxxxx was presented. It was composed of a pulse pattern generator (SAA8103), a vertical line driver (TDA9991), four analog-to-digital interfaces (TDA9965) and a system controller (P89LV51RD2). Camera link with medium configuration was adopted to transfer digital images. The software for controlling and debugging the camera was developed. To correct the non-uniformity of 4 outputs, a method based on two-point correction was described. The system can acquire ultra high resolution pictures at a high frame rate thus it is suitable for aero photography.
Related Articles | Metrics
A CMOS high performance 50MSPS sample/hold circuit
LI Tie, GUO Li, BAI Xue-fei
2007, 24 (6): 788-793.
Abstract ( 2528 ) PDF ( 1540KB ) ( 3543 )
A high performance CMOS sample/hold circuit is presented, which achieves the precision of 10-bit over Nyquist band in 50-MHz sampling frequency at 3.3-V supply. This circuit uses full differential circuits, bottom-plate sampling, bootstrap circuits and high performance gain-boost operational amplifier. Simulation in 0.35-μm CMOS process shows the circuit consumes 18-mW of power.
Related Articles | Metrics
An easy-to-deploy behavior monitoring scheme for Android applications
WANG Xueqiang, LEI Lingguang, WANG Yuewu
2015, 32 (5): 689-694.
Abstract ( 749 ) PDF ( 1223KB ) ( 3543 )

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

Reference | Related Articles | Metrics
Heavy metals in aerosol in China: pollution, sources,and control strategies
TAN Ji-Hua, DUAN Jing-Chun
2013, 30 (2): 145-155.
Abstract ( 3044 ) PDF ( 1395KB ) ( 3489 )

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

Reference | Related Articles | Metrics
Optimized Regulation Model of Human-Earth System Based on System Dynamics
CHENG Ye-Qing
2006, 23 (1): 83-90.
Abstract ( 1918 ) PDF ( 816KB ) ( 3277 )
study of human-earth system is the most important content in geography; regional sustainable development relies on the reasonable structure optimal model and effective regulation of regional human-earth system. County region is a complex and opening human-earth system, taking Huangling county as an example, the environment, resources exploitation, economic development and structure evolvement of industry were systematically analyzed. And the systematical dynamic model was established and multi-projects were simulated with the theory and method of system dynamic. Optimized regulation models of human-earth system evolvement were educed based on three projects: (1) Traditional evolvement method. The intensity of resource exploitation and environment pollution is the least, but the speed of its economy development is the lowest, which restrict social sustainable development and economic reproduction. (2) Economy development method. The intensity of resource exploitation and environment pollution is the worst, economic development mostly depends on higher investment and pollution, which is a traditional mode of unsustainable development. (3) Harmonious development mode. The mode considers not only economic sustainable development and natural recourses utilizing reasonably, but also gives more attention to environment protection and harmonious development of industry, agriculture, tourism and so on. It is the optimized mode of the human-earth system evolvement.
Related Articles | Metrics
Rice Varietal Improvement and Rice Production in China
LI Hai-Ming
2007, 24 (1): 1-8.
Abstract ( 1707 ) PDF ( 832KB ) ( 3246 )
The specific objective of the study is to analyse the adoption of improved varieties and the changes in characteristics of varieties across China. It also estimates the contribution of varietal improvement to rice production in China. The results indicated that the story of rice improvement over the past 50 years stood as an enormous success. Nearly 30% of the net gain in rice production came from varietal improvement. Compared with the beginning of 1980s, the numbers of released varieties have been improved by 1. 5 times, the share of total rice area planted to varieties with resistances has increased 10%, and the planting area of high-quality varieties has increased 50%. However, the declining contribution of varietal improvement since 1997 pointed out that government should encourage breeders to explore elite germplasm, improve breeding level, and break through yield stagnates so that varietal improvement can contribute greater to rice production.
Related Articles | Metrics
Experiment and numerical simulation of thermal conductivity of uranium dioxide
WANG Zeng-Hui, HUANG Xiao-Feng
2009, 26 (3): 415-418.
Abstract ( 2029 ) PDF ( 929KB ) ( 3212 )

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

Reference | Related Articles | Metrics
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.
Abstract ( 1669 ) PDF ( 152KB ) ( 3147 )

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

Reference | Related Articles | Metrics
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.
Abstract ( 2558 ) PDF ( 833KB ) ( 3113 )
K-means is an important clustering algorithm. It is widely used in Internet information processing technologies. Because the procedure terminates at a local optimum, K-means is sensitive to initial starting condition. An improved algorithm is proposed, which searches for the relative density parts of the database and then generates initial points based on them. The method can achieve higher clustering accuracies by well excluding the effects of edge points and outliers, as well as adapt to databases which have very skewed density distributions.
Related Articles | Metrics
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.
Abstract ( 2183 ) PDF ( 977KB ) ( 2997 )
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.
Related Articles | Metrics
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.
Abstract ( 2183 ) PDF ( 1035KB ) ( 2832 )
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.
Related Articles | Metrics
Predicting sunspot variations through neural network
CHENG Shu, SHI Yaolin, ZHANG Huai
2022, 39 (5): 615-626.
Abstract ( 547 ) PDF ( 16219KB ) ( 404 )
Sunspot variations are the sun's symptoms of strong magnetic perturbations. In this paper, we use long short-term memory neural network and one-dimensional convolution neural network to detect sunspot variations. Here we use three different datasets, including the yearly mean sunspot number (YSSN) from 1700 to 2020, the monthly mean sunspot number (MSSN) from 1749 to 2021 and the monthly mean sunspot areas (MSSA) from 1874 to 2021. First, based on the YSSN dataset, we obtain YSSN for 2021 and the predicted YSSN in the 25th solar cycle appears at 2025 which equals 163.4; Then, based on the MSSN dataset, we obtain MSSN for June 2021 and the predicted YSSN in the 25th solar cycle appears in October 2024 which equals 245.9; Next, based on the MSSA dataset, the predicted MSSA for June 2021 is 73.1; Finally, the latitude is divided into 13 partitions to predict the butterfly diagram, and still, neural network can reconstruct the butterfly diagram. Therefore, neural network can provide a physical perspective for sunspot investigation.
Reference | Related Articles | Metrics
A new joint model for extracting overlapping relations based on deep learning
ZHAO Minjun, ZHAO Yawei, ZHAO Yajie, LUO Gang
2022, 39 (2): 240-251.
Abstract ( 515 ) PDF ( 4199KB ) ( 194 )
With the rapid developments of Internet technologies and popularization of Internet among daily activities, we are surrounded by all kinds of information every moment. Hence, to mine valuable information from massive data has always been a hotspot of research at home and abroad. In this environment, relationship extraction is an important subtask of information extraction, which purpose is to identify the relationship between entities from the text, so as to mine the structured information in the text, that is, fact triplet. In the text, entity overlapping and relationship overlapping are very common phenomena, but the existing joint extraction model cannot effectively solve such problems, so the paper proposes a new joint extraction model, which regards the relationship extraction task as consisting of entity recognition and relationship recognition of two subtasks. The two subtasks are identified using sequence labeling method and multi-classification method, respectively. In the joint extraction process, in order to fully mine the semantic information of the text, the part of speech (POS) and syntactic dependency (Deprel) features were added to the input layer of the model. Attention mechanism is also introduced in the model, which can eliminate the problem of long-distance dependence as sentence length increases. Finally, the paper conducts relationship extraction experiments on the NYT dataset and the WebNLG dataset. The experimental results show that the model proposed in the paper can effectively solve the problem of overlapping relationships and obtain the best extraction effect.
Reference | Related Articles | Metrics
Solutions of a class of stochastic Poisson systems
WANG Yuchao, WANG Lijin
2022, 39 (6): 721-726.
Abstract ( 479 ) PDF ( 1392KB ) ( 270 )
In this paper, a class of stochastic Poisson systems, arising from randomly perturbing a type of Lotka-Volterra systems by certain Stratonovich white noise, are considered. We give the sufficient conditions for the almost sure existence (global non-explosion) and uniqueness of the solution of the system, and further prove that the solution is positive and bounded almost surely under the proposed conditions. Numeraical experiments are performed to verify the results.
Reference | Related Articles | Metrics
Fine process method for Gaofen-3 L1A-level image
FANG Hankang, ZHANG Bo, CHEN Weirong, WU Fan, WANG Chao
2022, 39 (5): 648-657.
Abstract ( 475 ) PDF ( 9292KB ) ( 128 )
Level one A (L1A) product of Gaofen-3 SAR satellite is the primary image set delivering for customer. This paper presents a complete workflow to facilitate the post-process of GF-3 L1A images for follow-up scientific research or value-added applications, where robust and precise processing is essential to generate the advanced high-level product concerning radiometric correction and geometric correction. Firstly, to eliminate the statistical bias caused by the null and zero pixel values induced in the quantization of the L1A product, an improved radiometric correction formula is derived based on the equivalent noise coefficient of Gaofen-3 images. Then, to determine the coordinates of image corners, an inverse algorithm supported by RPC parameters is proposed for geometric correction. This algorithm is robust by counting on the orbit direction, look direction, and sampling interval provided in an XML metadata file. Finally, a SAR filter operator is introduced into the resampling step of output results to improve the equivalent look number. Experimental results comparing with the radiometric values of a sentinel-1 image and the geometric accuracy of a sentinel-2 optical image, respectively, validate the accuracy and reliability of this method for L1A product processing.
Reference | Related Articles | Metrics
An experimental investigation on the breakup characteristics of liquid metal free jet under a horizontal magnetic field
DONG Quanrun, YANG Juancheng, NI Mingjiu
2022, 39 (5): 577-585.
Abstract ( 459 ) PDF ( 10358KB ) ( 541 )
Based on a high-speed photographic system, experiments on three-dimensional free jets of liquid metal in the absence of a magnetic field and in a horizontal magnetic field have been carried out to observe the process of liquid GaInSn jet breakup and droplet formation in an oxygen-free environment with a maximum We of 400 and a maximum Ha of 30. From the results on jet morphology, surface disturbance, and breakup length, we analyzed the characteristics of jet breakup. In the absence of magnetic field, the jet shows nine different morphologies, and the surface disturbance shows two forms:expansion wave and sinusoidal wave; with the increase of We, the disturbance amplitude first decreases and then increases, and the breakup length first increases and then decreases. When a horizontal magnetic field is imposed, the jet shows four typical morphologies, with the leading edge of the jet being flattened in the direction of the vertical magnetic field line and elliptical along the magnetic field line. As the Ha number increases, the jet break length tends to increase overall, but decreases in some operating conditions. The results of this paper have enriched the phenomenon of liquid metal jets under magnetohydrodynamic effects.
Reference | Related Articles | Metrics
A review of three-dimensional point cloud denoising
XIAO Jun, SHI Guangtian
Accepted: 13 April 2022
Building extraction based on UNet++ network with different backbones
GU Yumin, YAN Fuli
2022, 39 (4): 512-523.
Abstract ( 454 ) PDF ( 55188KB ) ( 454 )
Automatic building extraction methods based on deep learning theory have the technical characteristics of high accuracy and speed,and are of great significance in industrial applications, such as urban planning,disaster prevention and mitigation. This paper introduces the deep learning modules and the traditional remote sensing validation section in the proposed building extraction method in high-resolution remote sensing imageries, forming an operational deep-learning-theory based building extraction technical system that integrates different backbone modules, UNet + + networks,and remote sensing authenticity verification modules. The basic network is transformed through the traditional convolutional network model backbones,such as VGG,ResNet, and Inception to improve the model operational efficiency,strengthen the model feature learning capabilities,verify the effectiveness and applicability of the algorithm through authenticity validation. Taking the Massachusetts building dataset published by Mnih as the data source,a comparative analysis was carried out with the traditional non-full convolutional network model and full convolutional network model. The results show that an increasing in the depth and width of the model can substantially improve the building extraction results. The InceptionV3-UNet + + backbone model has the best performance in recall rate,accuracy,CSI, F1 score,Kappa coefficients, and total accuracy,reaching 85. 14%,90. 50%,0. 781 6,0. 877 4,0. 850 4, and 95. 57%,respectively,and its robustness is also verified on the WHU datasets. This method has significantly improved the extraction accuracy and the details of the buildings extracted, especially on complex and irregular buildings, which will facilitate the building extraction applications in real, complex, and large scene of high-resolution remote sensing imageries.
Reference | Related Articles | Metrics
Robust ordinal mislabel logistic regression based on γ-divergence
GUO Meijun, REN Mingyang, LI Shiming, ZHANG Sanguo
2022, 39 (3): 289-301.
Abstract ( 440 ) PDF ( 1540KB ) ( 203 )
Ordinal multi-classification methods have been studied widely. Traditional ordinal multi-classification methods assume that the sample label is not mislabeled. Due to the complexity of the real data and the limited artificial experience, it is unrealistic to obtain completely accurate labels, in which conventional methods perform poorly. In this article, we propose an ordinal mislabel logistic regression method based on γ-divergence, which possessing strong robustness when dealing with ordinal mislabeled response data. That is to say, when mislabeled, the weight of the sample in parameter estimation equation diminish compared to the case that the sample is properly labeled. Our method not only possesses the robustness but also can ignore the mislabel probabilities in the model. We construct the model by minimizing γ-divergence estimation and solve the model by gradient descent algorithm. Both simulation studies and real data analysis demonstrate that the method, namely robust ordinal mislabel logistic regression, is efficient to analyze ordinal mislabeled response data.
Reference | Related Articles | Metrics
Removing highlights from single image via an attention-auxiliary generative adversarial network
ZHAO Xinchi, JIANG Ce, HE Wei
2022, 39 (4): 524-531.
Abstract ( 435 ) PDF ( 10210KB ) ( 158 )
The highlights in the image will degrade the image quality to some extent. In this paper, we focus on visually removing the highlights from degraded images and generating clean images. In order to solve this problem, we present an attention-auxiliary generative adversarial networks. It mainly consists of the convolutional long short term memory network with squeeze-and-excitation (SE) block and the map-auxiliary module. Map-auxiliary can instruct the autoencoder to generate clean images. The injection of SE block and map-auxiliary module to the generator is the main contribution of this paper. And our proposed deep learning-based approach can be easily ported to handle other similar image recovery problems. Experiments prove that the network architecture is effective and makes a lot of sense.
Reference | Related Articles | Metrics
Review of studies on electrical conductivity of hydrous minerals
WANG Libing, WANG Duojun, SHEN Kewei
2022, 39 (4): 433-448.
Abstract ( 415 ) PDF ( 5955KB ) ( 214 )
Hydrous minerals play a vital role in the Earth's interior water cycle. The path of water cycle and the change of composition in the Earth's interior can be estimated by the electrical conductivity of typical hydrous minerals. In this paper, we summarized the electrical conductivities, conduction mechanisms, dehydration mechanisms and geophysical implications for typical hydrous minerals before and after dehydration under high temperatures and pressures. The electrical conductivities of most hydrous minerals before dehydration are generally distributed at 10 -4S/m, and increase significantly after dehydration. There are differences in the electrical conductivities of different hydrous minerals. The coupling of dehydration mechanisms and conduction mechanisms may determine the electrical conductivity of hydrous minerals during dehydration. The electrical conductivity of hydrous minerals after dehydration generally depends on the composition and connectivity of the fluid. The changes of electrical conductivities of hydrous minerals before and after dehydration provide experimental constraints for the high-conductivity anomalies at different depths in subduction zones. In addition, the determination of the composition of the fluid derived from the dehydration of the hydrous minerals enriched our knowledge of material circulation in subduction zones. Based on the recent progress, the potential research directions of the electrical conductivity of hydrous minerals are prospected.
Reference | Related Articles | Metrics
Signed-rank-based test for high dimensional mean vector
LIU Yan, LI Shiming, ZHANG Sanguo
2022, 39 (5): 586-592.
Abstract ( 388 ) PDF ( 2179KB ) ( 159 )
This work is concerned with tests for one-sample mean vectors under high dimensional cases. Existing high dimensional tests for mean vectors base on the assumption of elliptical distribution have been proposed recently. To extend to more distributions, we propose a signed-rank-based test. The proposed test statistic is robust and scalar-invariant. Asymptotic properties of the test statistic are established. Numerical studies show that the proposed test has a good control of the type-I error and is more efficiency. We also employ the proposed method to analyze an ophthalmic data.
Reference | Related Articles | Metrics
Spatio-temporal change of ecological land in lake-basin of Yangtze River system
CHEN Zhongyuan, GAO Yongnian
2022, 39 (2): 172-184.
Abstract ( 378 ) PDF ( 16565KB ) ( 392 )
The area of lake type watershed (LTW) accounts for more than 30% of the Yangtze River basin, and the change of its ecological land plays an important role in regulating the water ecological environment of the Yangtze River. Based on the land use data of 229 LTWs in the Yangtze River system from 1980 to 2015, the temporal and spatial change characteristic of ecological land in recent decades was analyzed by using the methods of ecological land area and its proportion, improved comprehensive dynamic degree, transfer matrix, and spatial operation. The results showed that the change of ecological land use in the LTWs presented a three-stage trend of "first gradually increasing, then fluctuating and stable, and finally rapidly decreasing"; Woodland and grassland showed a downward trend, while wetland showed an upward trend; The comprehensive dynamic degree of ecological land in the LTWs presented a state of "wave-like vibration". From the perspective of lake size classification, the total area of ecological land in the four types of LTW was quite different. The watershed ecological land corresponding to small lakes was the least, followed by large and medium-sized lakes, while the watershed ecological land area of super large lakes was the largest. Although the ecological land change trend in different types of LTWs was first rising and then declining, the corresponding turning points appeared in different years. From the perspective of different regions of the Yangtze River system, compared with 1980, the ecological land of the LTW in the source, middle, and lower regions increased in 2015, while the ecological land of the LTW in the upper regions decreased; The transfer amount within ecological land was the least, and the transfer amount between ecological land and non-ecological land and the transfer amount within nonecological land accounted for more than 42% of the total transfer amount. The transfer of ecological land was the most complex and intense in the middle region, followed by the lower region, the source region and the upper region were relatively gentle and simple. Before 2000, the main reasons for the change of ecological land were cutting trees, developing agriculture and animal husbandry and reclaiming land from lakes. After 2000, the main reasons were returning farmland to forests and building reservoirs. The increase of construction land, i. e., urban expansion, was one of the main reasons for the decrease of ecological land for most LTWs from 2010 to 2015.
Reference | Related Articles | Metrics
DFT mechanistic insight into the modular strategy involved in the palladium-catalyzed synthesis of cyclopentenones from α,β-unsaturated acid chlorides and alkynes
ZHONG Liang, ZHAO Ruihua, WANG Zhixiang
2022, 39 (2): 145-153.
Abstract ( 359 ) PDF ( 8789KB ) ( 170 )
Cyclopentenones are important synthetic building blocks and as motifs appear in bioactive molecules and natural products. We applied density functional theory (DFT) calculations to gain insight into the modular strategy involved in the palladium-catalyzed synthesis of cyclopentenone from α,β-unsaturated acid chlorides and alkynes in the presence of hydrosilane. The study unveils that the transformation proceeds via the sequence:the disassembly of α,β-unsaturated acid chloride into vinyl, carbonyl, and Cl fragments with the palladium catalyst; carbon monoxide release; coupling of alkyne with vinyl group; carbon monoxide re-coordination and migratory insertion to form another C-C bond with alkyne, ring-closure via C=C bond insertion, transmetalation with hydrosilane, C, H-reductive elimination to release the product. Different from the mechanism proposed by the experimentalists, the CO group is involved in the reaction via separate liberation and re-coordination in the solvent cage, rather than persistent coordination with palladium. The transmetalation for H/Cl exchange takes place at the late stage and is a bottleneck of the transformation, instead of at early disassembly stage.
Reference | Related Articles | Metrics
Coherence analysis of high resolution SAR sub-aperture image and its application in ground feature classification
XING Wenji, JIN Yan, QIU Xiaolan, DING Chibiao, ZHOU Xiao
2022, 39 (6): 764-775.
Abstract ( 353 ) PDF ( 23603KB ) ( 112 )
With the continuous improvement of synthetic aperture radar (SAR) resolution, the transmitted signal bandwidth and synthetic aperture are continuously increasing, which provide more options for subsequent applications. How to develop the potential of high resolution SAR with large synthetic aperture and large signal bandwidth in the application of ground feature classification and interference is worth studying. Coherence, the feature most commonly used in SAR image analysis, is analyzed in this paper. Firstly, the coherence coefficients between the sub-apertures, sub-bands, and repeat-pass interferometric sub-apertures of typical targets, such as man-made targets and natural features, are analyzed theoretically. Then, the above coherence coefficients are calculated using the real data of high-resolution spaceborne SAR to verify the correctness of the analysis. And then, unsupervised feature classifications are performed according to different features of different ground objects in different coherence coefficients, and the features represented by different categories were given. The analysis results in this paper provide support for the optimization application of high-resolution SAR data, and deepen the understanding of the characteristics of different SAR targets.
Reference | Related Articles | Metrics
Hot spots tracking of nighttime light data application in research of urbanization and its resource and environmental effects
ZHANG Xiaoping, GAO Shanshan, CHEN Mingxing, ZHAO Yanyan
2022, 39 (4): 490-501.
Abstract ( 349 ) PDF ( 4386KB ) ( 240 )
Being closely related to human socioeconomic activity and its footprints, nighttime light (NTL) data shows great advantages in urbanization and socioeconomic development research, especially in densely populated cities. Based on CiteSpace software and the core databases of CNKI (China National Knowledge Infrastructure) and WOS (Web of Science), this paper tracked the hot spots of NTL data in the study of urbanization and related resource consumption and environmental effects from 2000 to 2019. The main results are as follows. 1) Urbanization was the main focus of the application of NTL data, but the researches on the resource consumption and environmental effects caused by urbanization were slightly weak, which was more obvious in Chinese literature. 2) Researches of urban expansion and urban form evolution focused on process of land expansion based on different features of NTL datasets, while in researches of population, socioeconomic development, electricity consumption and carbon emissions, NTL data usually played the role as a supporting tool to explore spatiotemporal characteristics and mechanism. 3) In regards of air pollution and urban heat island induced by urbanization, NTL datasets were usually used to represent factors related to human activities and their impacts. 4) Urbanization process and its impacts on resource and environment are complex, the improved spatial resolution and integrated multi-source data, along with new methods as machine learning, will make the urbanization related research be more precise and scientific. Finally, the paper summarizes the possible new directions of the application of NTL data in urban geography.
Reference | Related Articles | Metrics
Momentum strategy, momentum crashes, and risk management: an empirical research based on Chinese commodity futures market
WEI Yongfeng, ZHAO Wei
2022, 39 (5): 593-614.
Abstract ( 336 ) PDF ( 3823KB ) ( 154 )
This article aims to study the effectiveness of momentum strategies in Chinese commodity futures market, and after judging the existence and causes of momentum crashes, puts forward effective methods to manage the risk of momentum crashes. In this paper, considering the transaction costs, the commodity futures momentum strategy can continuously obtain significant risk-adjusted returns, and further empirical discovery of the momentum crashes phenomenon in Chinese commodity futures market. The reason of momentum crashes is that the loser portfolio has the nature of option-like is more sensitive to market portfolio volatility, which in turn leads to the crashes of momentum portfolios. In order to carry out the risk management of momentum crashes, this paper proposes to construct a dynamic weighted momentum strategy based on target condition stop to manage the risk of momentum crashes. The results show that this method effectively avoids the extreme risk brought about by momentum crashes and obtains higher momentum return and Sharpe ratio.
Reference | Related Articles | Metrics
The recognition and utilization of Cannabis sativa in ancient Xinjiang viewed from plant remains
LIU Yan, GU Man, CHEN Tao, WANG Binghua, JIANG Hong'en
2022, 39 (4): 567-576.
Abstract ( 333 ) PDF ( 4845KB ) ( 320 )
Xinjiang is an important area connecting the east and west alongside the Silk Road. As a result of its dry weather and less rainfall, plant remains were well preserved, including hemp ( Cannabis sativa). The history of Cannabis recognition and utilization in ancient Xinjiang could be roughly divided into two stages. Due to inherent advantages of the geographical environment, Xinjiang was firstly affected by the ancient civilization of Central Asia in the prehistoric period, mainly retaining the hallucinogenic tradition of Cannabis. During the historical period, the beginning of the Silk Road promoted exchanges between the Western Regions and the interior areas. The edible and fiber values of Cannabis were gradually accepted. Therefore, in terms of Cannabis usage, ancestors generally had a transformation from psychoactive agents to food crops, fiber crops, and even medicinal plants. In this study, we reviewed the Cannabis researches in Xinjiang during the past years, summarizing the ways and differences of Cannabis utilization, especially their causes in different periods. Meanwhile, we restudied Cannabis remains in Turpan with plant identification and radiocarbon dating, comprehensively sorting out the handed-down and unearthed documents, to explore not only the utilization of Cannabis medicinal value, but also to provide new clues for the spread of Chinese medicine in ancient Xinjiang.
Reference | Related Articles | Metrics
Ab initio simulations of NO adsorption on hematite (0001) surface: PBE versus PBE+U
WU Cuixia, SUN Tao, FABRIS Stefano, DU Lin
2022, 39 (2): 193-200.
Abstract ( 326 ) PDF ( 4596KB ) ( 120 )
NO x( x=1,2) are major air-pollutants detrimental to human health and much effort has been devoted to find efficient photocatalysts capable of removing NO x from air (de-NO x). Recent experiments indicate that hematite (α-Fe 2O 3) is a promising de-NO x photocatalyst. However some key features of the NO adsorption on the hematite surface remain unclear, hindering further comprehension of the photocatalytic process. Here we study the adsorption of NO on the hematite (0001) surface using the PBE+U method with a dispersion correction (vdw) in the framework of density functional theory (DFT). We find the addition of a Hubbard U term in the DFT Hamiltonian strongly affects the adsorption properties, with the adsorption energy (-0.64eV) decreased by 50% with respect to those of PBE (-1.31eV). This decrease is attributed to two factors:(i) the U term shifts the energy of Fe 3d orbitals away from the valence band maximum, making them chemically less active; (ii) the NO molecule has an unpaired π * electron and is more sensitive to the electronic structure of the substrate. In contrast to the inclusion of U, the dispersion correction causes little change to the adsorption properties except increases the adsorption energy by about -0.18eV. We use the Langmuir formula to calculate the thermal equilibrium coverage of NO on the hematite (0001) surface and find predictions made with the PBE+U vdw are more consistent with experiments. These results highlight the importance of strong electronic correlations in describing the hematite surface reactions, and may serve as a starting point to unravel the complete photocatalytic mechanism.
Reference | Related Articles | Metrics
A LiDAR data visualized management and analysis system for power line inspection application based on B/S architecture
LIANG Lei, XI Xiaohuan, WANG Cheng, WANG Jinliang, HUANG Youju
2022, 39 (2): 201-207.
Abstract ( 320 ) PDF ( 12077KB ) ( 358 )
LiDAR, being an active remote sensing technology, can obtain 3D information of surface feature and has extensive applications in power line fields, such as construction line selection, digital management, safety inspection, etc. However, the software visualized management ability is a serious limitation of its widespread use. In this paper, we built the overall and functional design of a LiDAR data visualized management and analysis system based on B/S architecture, focusing on electric power line inspection application requirements. WebGL was applied to develop this system and points cloud data were stored and indexed by an improved modifiable nested octree, and rendered by Levels of Detail and other technologies. A lot of practical function and tools, such as interaction in 3D scene, managing data of power line features, editing point cloud attribute, 3D measurement, clipping, profile map and points cloud filtering were all achieved. The research results show that LiDAR electric power line inspection in web browser is applicable and effective, and has prospective application in future.
Reference | Related Articles | Metrics
Road information extraction and application in the suburban mountainous area based on remote sensing images
CHEN Ruonan, PENG Ling, LIU Yufei, WEI Zhichao, LYU Beiru, CHEN Deyue
2022, 39 (5): 658-667.
Abstract ( 310 ) PDF ( 14720KB ) ( 373 )