Journal of University of Chinese Academy of Sciences

MM algorithm of the estimation of single-index quantile regression

GUO Yuanyuan, YANG Xuemei, SUN Zhihua

2021, 38 (3): 289-296. DOI: 10.7523/j.issn.2095-6134.2021.03.001

The single-index quantile regression model is an important semiparametric model with the merit of dimensionality reduction. Furthermore, it retains the robustness of a nonparametric model. For most existing estimating procedures of single-index quantile regression models, the estimators are obtained via minimizing the objective functions by the interior point method. In this paper, we investigate the MM (majorize-minimize) algorithm of the single index quantile regression model estimating procedure. We first construct the majorize function of the objective function and then minimize the substituted majorize function to find the estimators. Our numerical simulations and empirical study show that for the considered model, the MM algorithm has good stability and can yield more accurate estimation. Compared with the interior point method, the MM algorithm is more efficient and takes less time.

Particle transport and charging mechanism of the nano particle within an electrostatic precipitator

FENG Yuxuan, LUO Kun, FAN Jianren

2021, 38 (3): 297-305. DOI: 10.7523/j.issn.2095-6134.2021.03.002

Abstract ( 333 ) PDF (0KB) ( 0 )

Based on the Ansys Fluent platform along with its secondary development programs, this research developed a comprehensive numerical model for nano particle migration within an electrostatic precipitator (ESP). The multi-field model coupled sub-models such as flow field, electric field, particle charging, and particle motion. The moving and charging behavior of nano particles in the ESP are fully discussed. The results show that both the amount and the direction of the body force on the particles will change periodically before collecting or escaping. The deposition efficiency curve of the nano particle presents the U-shape which is different from that of the micron particle. It proved that it is resulted from the changes of the main type and magnitude of the body force on the particle. Moreover, the charging mechanism of nano particles will also change. The charge is closely related to the particle size and particle concentration, directly affecting the Coulomb force on particles and corona discharge, which may lead to corona obstruction and seriously lower the particle deposition efficiency.

Effect of chiral amino acids on DNA chain polymerization

BU Xinya, CHEN Lu, KAN Yuhe, LEI Huajun, HE Yujian, FENG Lutian, WU Li

2021, 38 (3): 306-313. DOI: 10.7523/j.issn.2095-6134.2021.03.003

Abstract ( 350 ) PDF (0KB) ( 21 )

The amino acids that make up natural proteins are L-conformation. Although D-conformation amino acids are not the basic structural units of proteins, many plants, microorganisms, and even human bodies have D-amino acids. DNA polymerase chain reaction occurs widely in organisms and in PCR. In this paper, the effect of chiral amino acids and their coordination with metal ions on DNA chain reaction catalyzed by Taq-DNA polymerase was investigated for the first time. It provides experimental basis for further study of the effects of chiral amino acids and metal ions on organisms. Denaturing polyacrylamide gel electrophoresis showed that acidic amino acids had inhibitory effect on DNA chain polymerization, and the polar uncharged amino acids. The inhibition of primer extension by L configuration was greater than that of D configuration amino acids, whereas the D structure of polar positively charged amino acids was opposite to that of L configuration. In the experiments of adding 9 metal ions such as Na⁺, K⁺, Ca²⁺, and chiral amino acids, the PCR was almost inhibited by aluminium and zirconium salts, followed by nickel, copper and calcium. When chiral amino acid metal complexes were added, the influence of chiral amino acid metal complexes on the results was partly changed.

Ecological effect of Natural Forest Protection Project in Northeast China

XIANG Hengxing, WANG Zongming, MAO Dehua

2021, 38 (3): 314-322. DOI: 10.7523/j.issn.2095-6134.2021.03.004

Abstract ( 302 ) PDF (0KB) ( 0 )

As an important natural forest distribution area in China, Northeast China is a significant implementation area of the Natural Forest Protection Project (NFPP). The improvement of project implementation effects and regional ecological protection requires a systematic evaluation of ecosystem changes before and after the implementation of the NFPP. To achieve this aim, this study compared the changes in landscape pattern, ecosystem quality and services from 1990 to 2000 and from 2000 to 2015 by means of Landsat and MODIS data and InVEST model. Results show that 1) forest area increased by 2 133 km² from 2000 to 2015; 2) ecosystem quality was improved after the implementation of the NFPP characterized by increasing LAI and NPP; 3) forest ecosystem carbon stocks increased by 49 Tg and habitat area in poor suitable grade decreased by 1 423 km², while water yield of forests decreased by 3.5×10⁹ m³. Although NFPP has achieved obvious ecological effects, there were tradeoffs between water yield and other ecosystem services such as habitat quality and ecosystem carbon sequestrations. Given the findings in this study, we argue that regional ecosystem protection needs to be further improved, and this study will be expected to provide data support and scientific basis for rational use of regional natural resources and the construction of ecological civilization.

Spatial economic connection and network structure of cities and counties in Central Jilin Urban System

ZHENG Chenrouyu, MA Yanji

2021, 38 (3): 323-332. DOI: 10.7523/j.issn.2095-6134.2021.03.005

Abstract ( 231 ) PDF (0KB) ( 0 )

The development of Central Jilin Urban System is of strategic significance for advancing new urbanization in Jilin Province and promoting northeast revitalization. From the perspective of the interaction between cities and counties, based on the multi-index data, time distance data, and train frequency data of 26 cities and counties in Central Jilin Urban System, the entropy TOPSIS method, the gravity model, and the social network analysis method are used to analyze the spatial economic connections and network structure of cities and counties. The study shows that:1) Single-polarization of Central Jilin Urban System is prominent. The level of economic comprehensive development reflects the characteristic of the attenuation from the urban area of Changchun to the surrounding area. 2) The economic connection intensity of the top 2, 5, and 10 cities and counties in Central Jilin Urban System is characterized by "high contact proximity and low linkage, loose distribution" and a cross-shaped development axis is prominent globally. The urban connections are more prominent and low connections in other cities and counties restrict the process of integration and urbanization locally. 3) The FPI index of the entire urban system is 0.101, which presents the characteristic of absolute dominance. The radiation influence of Changchun City is insufficient. The regional node cities are underdeveloped. 4) The Central Jilin Urban System can be divided into 4 city groups. The midwestern region has an obvious characteristic of centripetal concentration. Cities and counties in the northwestern region have outstanding collaboration effect. The internal and external connections of Jilin City are obvious in eastern region. The southern region has great development potential. The research results provide scientific reference for urban agglomeration construction and regional economic layout optimization.

Error analysis concerning 2006-2017 Central Asia precipitation estimation based on CMIP5 model

HUANG Fang, GAN Miao, YU Yang, TA Zhijie, ZHANG Haiyan, PI Yuanyue, SUN Lingxiao, YU Ruide

2021, 38 (3): 333-340. DOI: 10.7523/j.issn.2095-6134.2021.03.006

Abstract ( 195 ) PDF (0KB) ( 0 )

The 24-model simulated data of the coupled model intercomparison project phase 5 (CMIP5) are used to compare with the 2006-2017 monthly precipitation grid data provided by the Climatic Research Unit (CRU) of the University of East Anglia from UK, and the evaluation of the precipitation estimation error concerning Central Asia under the multi-model ensemble is conducted through analysis of error spatial distribution, percentage errors, standard deviations and error trends. The results show that the model-ensemble precipitation is overestimated in most part of Central Asia, and it is obvious in the south-east Pamirs and West Tianshan Mountains; in the summer-half year, it is obviously overestimated in some regions of the south-eastern and southern Central Asia, but underestimated in north-east Central Asia; while in the winter-half year, it is overestimated in most part of Central Asia, and the precipitation is underestimated in the eastern Balkhash Lake and some regions in western Pamirs Plateau, with both the estimations errors are not obvious. Meanwhile, it is discovered that, the standard deviations in western and north-western parts of Central Asia among the annual, summer-half year and winter-half year are less than those in eastern and south-eastern parts of Central Asia; and the annual, summer-half year and winter-half year precipitation errors concerning most regions in Central Asia especially its middle part all show a declining trend; the spatial distribution of precipitation estimation error in El Nino and La Nina years determined the characteristics of the multi-year average estimated error distribution. The different error analysis shows that there would be severe larger uncertainty if estimating Central Asia precipitation directly using the CMIP5 outputs, and such uncertainty is most probably the result of the model's inherent problems, such as the defective descriptions of resolution ratio and topographic treatment, cumulus convection parameterization scheme, physical process of precipitation.

Spatiotemporal characteristics of different degrees of salinized cultivated land in Xinjiang in recent ten years

ZHUANG Qingwei, WU Shixin, YANG Yi, NIU Yaxuan, YAN Yuyan

2021, 38 (3): 341-349. DOI: 10.7523/j.issn.2095-6134.2021.03.007

Abstract ( 399 ) PDF (0KB) ( 0 )

In this study, the spatiotemporal characteristics of salinized cultivated land in Xinjiang from 2005 to 2014 were analyzed by matrix transfer method and land use dynamics. The matrix transfer method can calculate both the changes in the salinized cultivated land and transfer ratio of different degrees of salinized cultivated land from the previous period to the latter period. Our results indicate that:1)In 2005, the area of salinized cultivated land accounted for 32.07% of the total area of cultivated land. In 2014, the area of salinized cultivated land accounted for 37.72% of the total area of cultivated land. During the study period, the total area of salinized cultivated land in Xinjiang was increasing, and most of them concentrated in the new irrigation area. With the improvement of old irrigation area, the degrees of salinization damage were obviously weakened, and the salinized cultivated land showed a stable desalination trend. 2)The salinization degree was mainly mild in Xinjiang. The proportion of moderate and severe salinized cultivated land in southern Xinjiang was higher than that in northern Xinjiang. The salinization damage of cultivated land was serious in southern Xinjiang. There were some obvious differences in the structures and quantity of salinized cultivated land in various regions. The proportions of salinized cultivated land in Bazhou and Kashgar were higher than 50%, while the proportions of cultivated land in Urumqi and Yili were less than 10%. 3)There were also significant differences in the active degree of salinized cultivated land in various regions:The comprehensive dynamic degree of Karamay is the lowest, and the CLUD value was -0.39, indicating that the area of salinized cultivated land in Karamay has decreased. The CLUD values in other regions were positive, the hot spots with high comprehensive dynamics and rapid changes were mainly concentrated in southern Xinjiang, including Kezhou, Kashgar and Bazhou. Therefore, each region must formulate a plan for improving and utilizing soil salinization according to local conditions, and it must be consistent with the overall plan.

Spatial-temporal change and influence factors of park green space accessibility in arid area: taking Urumqi as an example

LIU Tao, YANG Degang, ZHANG Yufang, CAI Tianyi

2021, 38 (3): 350-359. DOI: 10.7523/j.issn.2095-6134.2021.03.008

Abstract ( 399 ) PDF (0KB) ( 0 )

As an important public service resource of the city, park green space plays an increasingly important role in improving livability of the city and enhancing well-being of residents. Based on GIS technology, this paper analyzes the temporal and spatial variation characteristics and influence factors of urban park green space accessibility in central area of Urumqi from 2007 to 2017, using the minimum distance method and the travel cost method considering the topographic factor, so as to provide scientific basis for layout of the green space of Urumqi parks. The results show that:1)The area of green park in central city of Urumqi continues to grow, and the spatial distribution shows a characteristic of "more in the south and less in the northsouth more north and less north". 2)From 2007 to 2017, the spatial and time accessibility of the green park in the central city increased greatly. The spatial accessibility shows a "circle layer" distribution feature, and time accessibility shows a "T"-shaped distribution feature. Both of them show a characteristic:gradually decreasing from the center to the periphery. Additionally,93.14% of the settlements can reach the nearest park green space within 5 min by 2017. 3)The density of road network, the area and shape index of park green space and the linear distance from residential space have significant influence on the accessibility of park green space. The density of road network and the distance between park green space and residential space are the key factors. 4)The change of green space layout is a main reason for the improvement of the accessibility in east-west direction,and it contributes more to the increase of accessible area within 5 min. The improvement of road network has a positive effect on the accessibility of park green space in the north-south direction, which plays an important role in area expansion with 5-30 min. The improvement of road network is the main reason for the improvement of green park accessibility in Urumqi.

Optimization of domestic tourism in Xinjiang under the policy of supporting Xinjiang tourism based on the modified tourism gravity model

GUO Jiaojiao, YANG Zhaoping, XU Xiaoliang, WANG Cuirong, ZHAO Hulan

2021, 38 (3): 360-366. DOI: 10.7523/j.issn.2095-6134.2021.03.009

Abstract ( 284 ) PDF (0KB) ( 0 )

The spatial structure of tourism market is the result of the interaction between tourist generating region and destination, and is a key field of tourism geography, which is directly related to the scientificity of tourism development strategic decision. Based on the flow characteristics of social factors between tourist generating region and destination, and the theoretical analysis of tourism gravity model, the paper adds policy factor to establish a tourism gravity suitable for Xinjiang, and measures the attraction of domestic tourism market. Besides, The IPA analysis method is used to compare the measurement results with the actual reception volume. The results showed that:Xinjiang local market is still the most important source market, which will be an unchangeable reality in the short term; Guangdong, Beijing, Sichuan, Jiangsu, Henan, Gansu, Shandong, Zhejiang, Shanxi, and Hebei are the main source markets except Xinjiang; Shanghai and Hubei are superior source markets; The other 18 provinces are potential source markets.

Fractal study on the spatial structure of A-class tourist attraction system in Urumqi

ZHAO Hulan, YANG Zhaoping, SHI Hui, LIU Qin, HAN Fang, WANG Cuirong, GUO Jiaojiao

2021, 38 (3): 367-373. DOI: 10.7523/j.issn.2095-6134.2021.03.010

Abstract ( 231 ) PDF (0KB) ( 0 )

Spatial structure of tourist attraction system has effects on spatial layout of regional infrastructures as well as the optimization and adjustment of regional spatial structure. Based on the fractal theory, this article studies the spatial structure of class-A tourist attraction system in Urumqi. Taking the Tianshan Grand Canyon (the only class-5A tourist attraction) as center to measure the aggregation dimension as well as the spatial correlation dimension based on crow distance and cow distance. This article indicates the following results:There are double fractal characteristics in the spatial structure of class-A tourist attraction system in Urumqi. In general, there is an aggregate distribution, and the distribution density decays rapidly from the center to the surrounding areas. In the evolution of the spatial structure, multi-center pattern may occur. The spatial structure of the tourist attraction system has a trend of self-organization optimization. Although there are strong traffic correlations among tourist attractions, the transportation network is not adequate enough. Based on these, the article proposes few recommendations to help shape tourism spatial network system by developing polycentric collaborative model, building theme sight-seeing spots, and creating high-quality self-driving routes.

A load forecast method of composite materials based on LSTM network and Kalman filtering

XIAO Ya, ZHOU Wei, CUI Jie, LIU Tingting, XIAO Ling

2021, 38 (3): 374-381. DOI: 10.7523/j.issn.2095-6134.2021.03.011

Abstract ( 484 ) PDF (0KB) ( 0 )

Composite material is a new type of material based on different combinations of various material components. It has been widely used in transportation, construction and other fields because of its excellent comprehensive properties during recent years. Despite of the large errors between experimental analysis and empirical analysis result sometimes,it is of great theoretical significance to establish a credible theoretical analysis to verify the bearing properties of composite materials.Considering that the forecast accuracy is affected by the length of the data sequence when using the memory characteristics of LSTM to predict the load, a load forecast method of composite materials combined with LSTM network and Kalman filtering is proposed. The model can learn from the data avoiding the dependence of traditional Kalman filtering on the dynamic model, at the same time the influence of training data sequence length on traditional LSTM can be overcome to some extent.The results show that the method proposed in this paper can obtain more excellent predictive performance:(1)The performance of LSTM-KF is better than the independent LSTM, and the prediction curve of LSTM-KF is closer to the actual load value;(2)The prediction error of LSTM-KF reduces that of LSTM from 0.033 0 kN to 0.016 0 kN, a decrease of 51.52%.

A new adaptive filter for slow-moving target detection based on FMCW radar

SONG Zhihua, CHEN Kunshan, ZENG Jiangyuan, XU Zhen

2021, 38 (3): 382-391. DOI: 10.7523/j.issn.2095-6134.2021.03.012

Abstract ( 416 ) PDF (0KB) ( 0 )

Frequency-modulated continuous wave (FMCW) radar is commonly used to detect the slow-moving target in close range, due to its capability of high-precision measurement and non-blind zone in close range. In this paper, a new adaptive clutter suppression filter is proposed for FMCW radar to detect ground slow-moving target scene. The proposed filter can be used to suppress the impact of strong clutter in the environment and to improve the detection performance. Results show that under the effects of the background of strong clutter, the peak value of signal after clutter suppression is reduced by 91.1%, and the average amplitude of signal is reduced by 82.7%. The proposed filter shows better performance in terms of suppressing clutter and extracting moving target compared to the moving target indication (MTI) pulse cancellation filter. Finally, the proposed filter is validated by using real measurement data. Results illustrate that the relative errors of distance detection and velocity detection are on the order of 10^-3, indicating the proposed filter has good detection accuracy.

Moving target detection and tracking of satellite videos based on V-CSK algorithm

HUANG Pingping, WANG Feng, XIANG Yuming, YOU Hongjian

2021, 38 (3): 392-401. DOI: 10.7523/j.issn.2095-6134.2021.03.013

Abstract ( 446 ) PDF (0KB) ( 0 )

Video remote sensing satellite has many applications in road traffic navigation, military dynamic monitoring, target tracking and so on, so the use of satellite video to achieve real-time detection and tracking of moving targets is of great concern. Aiming at the problem of moving target detection and tracking in satellite video, this paper proposes a detection and tracking method based on V-CSK algorithm, which adopts improved ViBe detection algorithm, introduces multiple custom threshold filtering algorithm to obtain the center area of moving target, and then extracts the center coordinates of target according to the principle of center position mean and noise distance judgment, and realizes the estimation and repair of track curve. Finally, the target tracking is realized by CSK algorithm. The experiment is based on three groups of satellite video data, and the contrast experiment of target detection and tracking is introduced as a reference. The experimental results show that V-CSK algorithm has good performance in satellite video moving target detection and tracking.

RPC-based configuration satellite simulator fault injection method

YANG Shanqiang, LI Huawang, CHANG Liang, GAO Caidong, YU Yeluo

2021, 38 (3): 402-408. DOI: 10.7523/j.issn.2095-6134.2021.03.014

Abstract ( 197 ) PDF (0KB) ( 0 )

In order to improve the reusability of satellite fault injection model and shorten the development cycle, this paper contains a standard hierarchical model for satellite simulation system, which consists of a satellite simulator, a fault injection front end, and a fault protocol. Each individual machine in the satellite simulator is configured with a universal stand-alone model to make the satellite simulator configurable. The fault injection front end encapsulates the fault information by calling each function in the simulator by RPC(remote procedure call) to improve scalability. The actual results indicate that the standard hierarchical model constructed based on this scheme can be configured to create the simulation models of different types of satellites. Moreover, the fault injection mechanism is embedded in each stand-alone model, which improves the reusability of the satellite simulation model and effectively shortens the cycle time of simulation modeling.

An anomaly detection method for satellite based on correlation probability model

SUN Yuhao, LI Guotong, ZHANG Ge

2021, 38 (3): 409-416. DOI: 10.7523/j.issn.2095-6134.2021.03.015

Abstract ( 302 ) PDF (0KB) ( 0 )

During the orbital operation of the satellite, the telemetry data is an important basis for reflecting the health status of satellites. The detection of potential anomalies in telemetry data is of great significance for the maintenance of satellites. Threshold method used in engineering can not effectively detect failure symptoms within the threshold, and the current theoretical research in this field can not effectively tap the potential correlation of multidimensional telemetry sequences. Therefore, this paper, taking the actual on-orbit telemetry data of a satellite as the object, adopts a detection method of correlation probability model that incorporates principal component analysis (PCA), and analyzes the failure case deeply. It verifies that this method can detect satellite's early failure and the results are compared and analyzed. This method can also quickly diagnose the failure so that the ground can handle it in time to avoid further accidents.

Analysis for QAM performance on WSN

ZHU Baiming, YAN Liyan, YIN Hongsheng, QI Honggang

2021, 38 (3): 417-422. DOI: 10.7523/j.issn.2095-6134.2021.03.016

Abstract ( 195 ) PDF (0KB) ( 0 )

The nonlinear characteristics of power amplifiers are always ignored in the research of wireless sensor network system in which the single carrier quadrature amplitude modulation is adopted. In fact, the effect of the nonlinear characteristics of power amplifiers on the system is also very important. In this paper, we assume the characteristics of the power amplifier, which is processed with nonlinear distortion compensation, as the approximate ideal class A of power amplifier. The different effects of the power amplifier are analyzed from the roll-off coefficient of the filter and the power regression of the power amplifier aspects on the three parameters of constellation, power spectral density, and symbol error rate. The simulation results verify our theoretical analysis.

A method to extend available main memory for computer systems

HAO Xiaoran, CHEN Lan, NI Mao, PAN Lei

2021, 38 (3): 423-432. DOI: 10.7523/j.issn.2095-6134.2021.03.017

Abstract ( 199 ) PDF (0KB) ( 0 )

In operating systems, swapping mechanism provides extended main memory space for memory-intensive applications. However, page-granularity swapping causes extra system I/O when objects are smaller than a page. This paper uses NAND flash-based SSD to extend DRAM main memory, and proposes an object-granularity hybrid main memory management scheme to reduce extra system I/O by caching as many hot objects as possible in DRAM. Compared to Linux-swap system, the proposed memory management scheme improves system performance by up to 47.5% for microbenchmarks and 73.3% for real-world memory-intensive workloads.

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