Journal of University of Chinese Academy of Sciences

Sharp bounds for fractional Hardy operator on higher-dimensional product spaces

LI Xiang, WEI Mingquan, YAN Dunyan

2020, 37 (1): 1-5. DOI: 10.7523/j.issn.2095-6134.2020.01.001

In this paper, we get the sharp bounds for fractional Hardy operator on higherdimensional product spaces from L¹(R^n₁×…×R^n_m) to the space wL^Q(R^n₁×…×R^n_m). More generally, the norm of fractional Hardy operator on higher-dimensional product spaces from L^P(R^n₁×…×R^n_m) to L^Q_I(R^n₁×…×R^n_m) is obtained.

Existence and related properties of non-zero Gaussian curvature Bonnet surfaces

WANG Ke, WU Yingyi

2020, 37 (1): 6-12. DOI: 10.7523/j.issn.2095-6134.2020.01.002

Abstract ( 282 ) PDF (KB) ( 3 )

We study two problems about Bonnet surfaces. First, we prove that the Bonnet surface whose Gaussian curvature is not identically zero must exist by studying the ordinary differential equation which the mean curvature of the Bonnet surface satisfies. Secondly, we prove that if there exists a conformal map which preserves the principal curvatures and the orientation between two Bonnet surfaces, then there are two cases as follows:1) If the zero points of the Gaussian curvature of the two surfaces are isolated, then the conformal map must be an isometry. 2) If the Gaussian curvature of the two surfaces is identically zero, then the conformal map is a similarity transformation.

Experimental study of free convection of liquid metal on vertical plate under the magnetic field

ZHOU Zhongkai, WANG Zenghui, CHEN Ran

2020, 37 (1): 13-19. DOI: 10.7523/j.issn.2095-6134.2020.01.003

Abstract ( 327 ) PDF (KB) ( 3 )

There are big temperature differences at different positions on the first walls facing the plasma in Tokamak device. Free convection experiments of liquid metal on the vertical wall are carried out under the influence of transverse magnetic field. In the experiments, K thermocouple is used to measure the temperatures of the environment and the both sides of the wall, and the flow boundary layer velocity of the wall is measured using a Doppler ultrasonic velocimeter.The experimental results show that the local heat transfer coefficient of the vertical plate is inversely proportional to the characteristic length, while the enhanced heating power increases the surface heat transfer coefficient. Under the condition of the strong magnetic field, the flow and heat transfer effect of the wall boundary layer are generally inhibited. However, in the weak magnetic field, increasing the magnetic field will enhance the effect of free convection and heat transfer on the surface of the plate. Based on the experimental results and existing simulation results, this turning point appears in the N range 1-4.

Effects of soil chromium pollution on activity of antioxidant enzyme of Eisenia fetida

LI Zejiao, CUI Yanshan, CAI Xiaolin, WANG Pengfei

2020, 37 (1): 20-26. DOI: 10.7523/j.issn.2095-6134.2020.01.004

Abstract ( 248 ) PDF (KB) ( 3 )

Effects of the soil type, exposure time, and chromium (VI) concentration on antioxidant enzyme[SOD (superoxide dismutase), CAT (catalase), and POD (peroxidase)] activity of Eisenia fetida were investigated. The experimental soils were selected from Heilongjiang, Shanxi, and Jiangsu Provinces, and then were aged for 40 days. The results of the significance analysis showed a significant difference in SOD activity in different soils (P<0.05), and Cr(VI) concentration and exposure time showed an extremely significant difference in SOD activity (P<0.01). Similar to SOD activity, the significant difference was found in the CAT activities of different soils (P<0.05), and Cr(VI) concentration and exposure time showed extremely significant effects (P<0.01) on CAT activity. Whereas, POD activities of different soils were significantly different (P<0.01), Cr(VI) concentration has a significant effect on POD activity (P<0.05), and the effect of exposure time on POD activity was significantly different (P<0.01). In Heilongjiang's aging soil, the POD and SOD activities increased significantly in the early exposure. In the experimental group exposed for 28 days, the maximum POD and SOD concentrations were 2.03 and 1.25 times those of the control group, respectively. With the delay of exposure time, the activities of POD and SOD were significantly inhibited, while there was no significant change in CAT activity in E. fetida. In the early exposure of soil of Jiangsu, the change trends of POD and SOD with time were similar to those of soil of Heilongjiang. In the early exposure of soil of Shanxi, POD and CAT activities increased significantly, and with the delay of exposure time the enzyme activity was significantly inhibited, but the SOD activity showed no obvious change under different aged treatments.

Spatial analysis of the effects of urban underlying surface and rainfall events on surface runoff based on SWMM: a case study of Yanqi Lake campus of University of Chinese Academy of Sciences

LUO Yingjie, ZHANG Na, LI Qi, WANG Xin, JING Yongcai, YUE Rongwu

2020, 37 (1): 27-38. DOI: 10.7523/j.issn.2095-6134.2020.01.005

Abstract ( 366 ) PDF (KB) ( 23 )

The Yanqi Lake campus of University of Chinese Academy of Sciences was taken for a case study. Stormwater management model (SWMM) was used to model water overflow processes in all the subcatchments in the study area during the 48 rainfall events in 2016 and 2017. The relationships of spatial distribution of surface runoff with rainfall and underlying surface were explored. The results showed that there occurred higher runoff in the subcatchments with asphalt land cover, while there occurred lower runoff in the green-cover subcatchments. Asphalt land cover had the greatest possibility to produce overflow, green cover had much weak possibility, and brickwork cover was more likely to produce intermediate runoff. Although concrete land or roof cover produced more overflow than brickwork cover, they had similar patterns of producing runoff under different rainfall events. The surface runoff values of asphalt or brickwork land cover were linearly positively correlated with the slope value. For the subcatchments with asphalt-brickwork or asphalt-green cover, percent impervious cover (PIC) should be reduced to be below 60% to significantly control rainstorm and heavy rain runoff. To significantly control heavy rainstorm runoff produced within the subcatchments with asphalt-green cover, PIC should be lower than 30%. However, for the subcatchments with asphalt-brickwork cover, decreasing impervious area did not have obvious effect on mitigating heavy rainstorm runoff. The study may provide theoretical basis and decision-making suggestions for sponge city construction and urban flood prevention and control.

Comparison between two air quality index systems in study of urban air pollution in China and its socio-economic determinants

ZHANG Xiaoping, LIN Meihan

2020, 37 (1): 39-50. DOI: 10.7523/j.issn.2095-6134.2020.01.006

Abstract ( 610 ) PDF (KB) ( 3 )

Since the environmental quality in metropolitan areas has significant impact on public health and everyday life of urban residents, it is of great importance to provide scientific information about the urban air pollutant concentration, which has gained much concern from both the governmental authorities and the scientific fields. This study illustrated the urban air quality of 113 sample cities in China by the comparison between the aggregate air quality index (AAQI) and the air quality index (AQI) and then depicted its spatial differentiation based on spatial interpolation. Furthermore, this study analyzed the influential factors behind the air quality variations among these cities by employing panel data models. The results indicated that the urban air quality showed a significant agglomeration feature at the national scale, with North China retaining the highest values both in terms of AAQI and AQI. From temporal perspective, the urban air quality reported a desirable trend nationwide from 2014 to 2016. Results from the regression models indicated that the urban air quality was affected by geographical locations, socioeconomic factors, and environmental regulations, among which urbanization level and industrial structure were reported to be the important socioeconomic factors exerting more significant impacts on the urban air quality. We suggest that more efforts should be devoted to develop comprehensive indices for evaluation of the urban air quality and to explore new avenues to improve urban air quality from industrialization and urbanization perspectives.

Quantitative analysis of the impact of climate change and human activities on grassland ecosystem NPP in Xinjiang

ZHAO Peng, CHEN Tao, WANG Qian, YU Ruide

2020, 37 (1): 51-62. DOI: 10.7523/j.issn.2095-6134.2020.01.007

Abstract ( 507 ) PDF (KB) ( 3 )

Grassland is the most widespread land cover type in Xinjiang, which plays a significant role in carbon cycle of terrestrial ecosystems. Climate change and human activity are two important factors affecting the terrestrial carbon cycle. Quantitative assessment of climate change and human activities is the critical step which dominates the grassland sustainability and the prevention of grassland degradation and desertification in Xinjiang. This study uses actual net primary productivity(NPP) and potential net primary productivity as indicators to quantitatively analyze the impact of climate change and human activities on Xinjiang grassland. Since the ecological engineering operation started in 2000 over China, the study period was divided into two parts:from 1982 to 2000 and from 2000 to 2015. The results showed that climatic factors were the main factors for the increase of NPP in Xinjiang from 1982 to 2000.The area affected by climatic factors accounted for 79.41% of the total grassland area. From 2000 to 2015, the area affected by human activities distinctly extended, and the area accounted for 45.05% of the total area. At the same time, human activities led to the variation of the ratio of the area with the increasing NPP from 18.71% to 27.87%, indicating that the ecosystem protection project achieved its goal. However, human activities led to the variation of the ratio of the area with the decreasing NPP from 1.87% to 15.22%. The reduction of NPP in grassland appearing in the Ili River Valley, the southern Altay Mountains, and parts of the Tianshan Mountains is mainly caused by human activities, such as overgrazing. The protection policies in these areas should be optimized and strictly followed, and the number of livestock should be controlled within a reasonable range. Therefore, the government should insist on the implementation of the ecological protection projects and gradually optimize its refinement and concreteness. In some overgrazing areas, such as Ili, Tacheng, and Altay, reduction of the amount of livestock has to be implemented so as to achieve the dynamic balance of grassland and livestock.

Spatiotemporal evolution of urban and rural development level and its coordination degree in Tarim Basin in recent ten years

WU Shengqin, YANG Degang, HUO Jinwei, WU Rongwei

2020, 37 (1): 63-73. DOI: 10.7523/j.issn.2095-6134.2020.01.008

Abstract ( 335 ) PDF (KB) ( 8 )

The level of urban and rural development and its degree of coupling and coordination affect regional social stability. In this study we construct the urban and rural comprehensive development level index, and use the exploratory spatial data analysis method (ESDA) to analyze the spatial and temporal evolution process of urban and rural development in the 42 counties and cities in Tarim Basin from 2004 to 2014. The main conclusions are shown as follows. 1) The urban and rural development level of the basin increased during the study period, but it is still low; and the characteristic of the development level was high in the east and south and low in the west and north. 2) Coupling degree (C_coupling) was generally fluctuating:Kizilsu was always in a low coupling area, Bayangol was in a high-value state, and the C_coupling of Hotan City and Yutian County reduced at the most rapid speed. The coordinated development degree (C_coordination) was generally on the rise and was fluctuating or declining only in a few areas. 3) The C_coordination was spatially positively correlated, the high-value agglomeration and hotspots were mainly located near Korla, and the low-value agglomeration and cold-spot areas were chiefly located at the junction of Kashgar and Hotan. The pattern of the low-value agglomeration and cold-spot areas remained basically unchanged during the two periods between 2004-2009 and between 2009-2014. This study finally proposes to improve the development pattern in the aspects of infrastructure investment, industrial optimization, education investment, embedded development, and social stability.

Analysis of the changes of ports and port-city relationships along the 21st-Century Maritime Silk Road

BI Sen, ZHANG Li, GU Yu, WANG Heng, WEN Li, LI Tong, BI Jingpeng

2020, 37 (1): 74-82. DOI: 10.7523/j.issn.2095-6134.2020.01.009

Abstract ( 1040 ) PDF (KB) ( 1 )

As important nodes of the 21st-Century Maritime Silk Road, ports and port cities play the key role in promoting the development of countries along the road. Based on Google Earth and Landsat remote sensing data and the container throughput statistics, we adopt the spatial analysis method to analyze the temporal and spatial variation characteristics of 38 important ports in the countries (excluding China) along the 21st-Century Maritime Silk Road. Furthermore, we introduce the urban construction land area as a representative parameter of urban development to modify the relative concentration index (RCI), and evaluate the relationships between ports and port cities along the road. The results are shown as follows. 1) The areas of important ports along the 21st-Century Maritime Silk Road have obvious regional distribution patterns, showing the characteristic of "bigger in the west and smaller in the east". 2) The variation of the port area (0.01-4.93 km²) and the change proportion of the port area (1%-507%) have the characteristics of regional differentiation. In the different regions (Southeast Asia, South Asia, West Asia, Africa, and Europe), the differences in port area change are little, while the differences in port area change proportion are large. 3) The port-city relationships also have obvious regional features. The influences of European ports on the cities are relatively strong (average RCI is about 2.98 in 2017), and the role of the ports in Asia is relatively weak (average RCI is about 1.51 in 2017). The results provide scientific information for construction of ports and port hinterlands.

Validation for building density remote sensing products of built-up areas at large scale

WANG Shuai, QIN Yuchu, YANG Fukun

2020, 37 (1): 83-92. DOI: 10.7523/j.issn.2095-6134.2020.01.010

Abstract ( 324 ) PDF (KB) ( 3 )

Building density map (BDM) product derived from remotely sensed imagery over large areas is the vital data set for supporting studies of human settlement environment and land use planning. GHSL (global human settlement layer) is a mapping project for developing human settlement map product with remotely sensed data. It is sponsored by the Joint Research Center of European Commission. The BDM is an important component of GHSL. Currently, the BDM of GHSL has been validated over Europe and America. However, the shapes of buildings and the landscape patterns of urban areas in East Asia, especially in China, are significantly different from those in the EU and US, and the validation of BDM over Asia is vital for further applications of the GHSL products. This study takes large area individual building footprint data sets over 5 typical mega cities (Shanghai, Xi'an, Changchun, Kunming and Urumqi) as ground truth through the pixel aggregation and the neighboring points searching and location matching, and the ground truth map of the building density is produced as the validation data set. With regression analysis, the method for BDM assessment is explored by calculating accuracy indicators over large metro-areas in China. The results show that the GHSL building density products of built-up areas reflect the densities of buildings in China at lower resolutions, but at higher resolutions they overestimate the densities in high-value areas. This study provides a basis for research and development of built-up area density products in China.

An information extraction method of earthquake-induced landslide: a case study of the Jiuzhaigou earthquake in 2017

LI Qilun, ZHANG Wanchang, YI Yaning

2020, 37 (1): 93-102. DOI: 10.7523/j.issn.2095-6134.2020.01.011

Abstract ( 325 ) PDF (KB) ( 3 )

Earthquake-induced landslide is the most common and the most destructive geological secondary disaster triggered by the earthquake. Rapid and accurate extraction of the distribution and extent information of landslides is of great significance for post-earthquake emergency rescue and post-disaster reconstructions. In this study, we take the Zhangzha Town, the heavily hit district by the "8·8 Jiuzhaigou earthquake", as the study region, and the information concerning the distribution and extent of the earthquake-induced landslides was extracted by combining the change detection technology and the object-oriented method. The extracted information was optimized using the improved region growing algorithm based on Sentinel-2A image. The extraction performance was evaluated by comparison with the traditional CVA extraction results, and the results indicated that the overall accuracy of our extraction was above 90% and the Kappa coefficient was over 0.7. The higher automation level and quicker processing of the proposed method in this study meet the time and precision requirements for earthquake emergency rescues.

TOC prediction model for muddy source rocks based on convolutional neural network (CNN): a case study of the Hangjinqi area of the Ordos Basin

WANG Huijun, ZHAO Guiping, LI Liang, ZHANG Wei, QI Rong, LIU Jun

2020, 37 (1): 103-112. DOI: 10.7523/j.issn.2095-6134.2020.01.012

Abstract ( 381 ) PDF (KB) ( 3 )

Total organic carbon (TOC) is a significant factor for oil and gas exploration and development. For determining TOC, previous researchers mainly employed ΔlogR and back propagation artificial neural network (BP). However, ΔlogR has a low coefficient of the determination of the calculated TOC compared to the core measured data, while BP is easily trapped into a local optimum. To address these challenges, we propose a new method based on convolutional neural network (CNN) to calculate TOC. In this work, the argillaceous source rocks in the Hangjinqi area of the Ordos Basin were studied, and the effectiveness of the method was verified. The experimental verification showed that CNN could be used for TOC prediction of the source rocks and the prediction accuracy was higher than those of ΔlogR and BP neural network. CNN was used to predict the TOC values of the Shan 1 and Taiyuan mudstones of 108 wells. The TOC planar graphs were made in combination with the sedimentary microfacies. We found that the TOC values of the swamps in the southeast and central parts were higher and the TOC values of the distributary channels were generally lower. The TOC plane distribution well matched the sedimentary microfacies distribution, showing the feasibility of this prediction method.

Non-field on-orbit geometric calibration method for spaceborne laser altimeter based on curve matching

CHEN Linsheng, ZHOU Mei, Tenggeer, CHEN Jiuying, LI Chuanrong, TANG Lingli

2020, 37 (1): 113-119. DOI: 10.7523/j.issn.2095-6134.2020.01.013

Abstract ( 312 ) PDF (KB) ( 3 )

The rapid development of spaceborne laser altimetry technology urgently requires an effective on-orbit geometric calibration method to correct the systematic errors in altimetry data. Based on curve matching, this study explores a method for on-orbit geometric calibration of the altimeter without field. The method uses the laser footprint elevation curve to match the DEM for obtaining the laser footprint control points to calculate the calibration parameter, and it is not necessary to build the detector calibration field. We use the ZY3-02 satellite altimetry data to verify the proposed calibration method and to evaluate accuracy of the calibration. Experiment results show that the accuracy of the altimetry data has been significantly improved after conection using the calibration method, which verifies the effectiveness of the method.

TMRC-Filter: a subband filter design method for Filtered OFDM system

LI Yingrui, XU Jing, LIU Xiang, YI Huiyue

2020, 37 (1): 120-127. DOI: 10.7523/j.issn.2095-6134.2020.01.014

Abstract ( 323 ) PDF (KB) ( 3 )

In order to satisfy requirements for the subband filter in Filtered-OFDM (filtered-orthogonal frequency division multiplexing) systems, the TMRC-Filter (truncate modified raised-cosine filter) is proposed based on the window function method. Compared with the traditional SinC-Filter (windowed sinc function filter) and RC-Filter (raised-cosine filter) whose linear phase filter ends with 0, the linear phase filter of the proposed TMRC-Filter ends with a non-zero roll-cut-off-amplitude factor, and the rolled-off bandwidth of the proposed TMRC-Filter can be flexibly adjusted. Moreover, the performance of the rpoposed TMRC-Filter is totally determined by the rolled-off bandwidth which is independent of the system parameter and roll-off factor, and it is simple to implement. The simulation results show that the TMRC-Filter achieves the lower ripple, larger stop-band attenuation, and better time localization than the SinC-Filter and the narrower transition band than the RC-Filter.

Intelligent mobile edge network caching based on deep learning

SONG Xuming, SHEN Yifei, SHI Yuanming

2020, 37 (1): 128-135. DOI: 10.7523/j.issn.2095-6134.2020.01.015

Abstract ( 477 ) PDF (KB) ( 2 )

In view of mobile edge network caching problem, computation resources are further pushed to the network edge to enable data analysis and to build deep learning-based caching strategy at access points, thereby boosting caching gain. The long short term memory (LSTM)-based neural network is proposed to predict the future content popularity by analysing the local data, which is further used to optimize content replacement for the cache hit rate maximization and construct deep caching strategy. Real-world dataset is used to validate the effectiveness of the proposed deep caching strategy. Numerical results demonstrate that our content popularity prediction method outperforms the state-of-art prediction method. Compared with traditional methods, the caching system needs only approximately half storage space to achieve the same cache hit rate.

Property analysis and validity verification algorithms of sum-product network

LIU Yang, LUO Chenxi, LUO Tiejian

2020, 37 (1): 136-143. DOI: 10.7523/j.issn.2095-6134.2020.01.016

Abstract ( 441 ) PDF (KB) ( 3 )

Sum-product networks (SPN) is a deep probabilistic graphical model which has the characteristic of fast inference in multilayer networks, and it has wide application prospect in the field of artificial intelligence. The validity of SPN is that it can be used to represent the probability distribution correctly so that SPN can be used to represent the distribution functions of some graph models and all the marginal distributions. Since SPN is not always valid, it is necessary to determine the effectiveness of SPN quickly. In this paper, we consider the problem of validity verification in the SPN theoretical system, reveal the internal structure properties of SPN, and propose two algorithms for verifying the validity of SPN. The correctness proofs and the complexity of the proposed algorithms are given. We also verify the reliability of the proposed algorithms by giving a new method of calculating the number of generation trees in SPN.

Current Issue