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    2022,14(3):253-266, DOI: 10.13878/j.cnki.jnuist.2022.03.001
    Abstract:
    The main objective of this study is to reveal the variation characteristics of extreme temperature and precipitation events in Lijiang of Yunnan province.The data of daily maximum and minimum temperature and daily precipitation from 1951 to 2017 were obtained from Lijiang Meteorological Station.The variation trends,mutation and period characteristics of 16 extreme temperature indices and 11 extreme precipitation indices have been analyzed with methods of linear regression analysis,Mann-Kendall abrupt change test,moving t test,and Morlet complex wavelet analysis.The results of variation trends are as follows.As for extreme temperature indices,significant increasing trends were observed in TNx,TNn,SU,TN90p,TX90p and WSDI;obvious decreasing trends were observed in FD,TN10p,CSDI and DTR;non-significant increasing trends were observed in TXx,TR and GSL;non-obvious decreasing trends were observed in TXn and TX10p;and the values of ID remained 0 days during the study period.As for extreme precipitation indices,a significant decreasing trend was observed in R1;a significant increasing trend was observed in R99pTOT;non-significant decreasing trends were observed in R10,CWD,PRCPTOT and Rx5day;whereas non-significant increasing trends were observed in R20,R95pTOT,CDD,Rx1day and SDII.The results of mutation test are as follows.Significant mutation years were observed in some extreme temperature and precipitation indices,which usually fall on period from the 1980s to the beginning of the 21st century or period from the 1950s to the 1970s.Furthermore,the extreme cold events indices of FD,TN10p and TX10p showed decreasing trends after the significant mutation years,while the extreme warm events indices of SU,TN90p and TX90p showed increasing trends after the significant mutation years.The values of TR were 1 day in 2015 and 0 days in the remaining years of the study period.The periodic results of wavelet analysis are as follows.The 15 extreme temperature indices (except ID) presented 2-6 quasi-periods ranging at 3-56 years,with 1-3 main periods ranging at 10-56 years.The 11 extreme precipitation indices presented 4-6 quasi-periods ranging from 4-56 years,with 1-3 main periods ranging from 12-56 years.Therefore,there are same or similar main periods for some extreme temperature and precipitation indices.
    2022,14(3):267-276, DOI: 10.13878/j.cnki.jnuist.2022.03.002
    Abstract:
    Given that there is very limited knowledge about how urban thermal environment varies diurnally,we first classified Local Climate Zones (LCZs) based on multi-source remote sensing data such as airborne LiDAR and IKONOS-2,and then investigated the responses of LCZs to diurnal Land Surface Temperature (LST).The results suggested that there was significant diurnal variability in LST among LCZs.During the daytime,the warmest and coolest zones were large low-rise buildings (LCZ 8) and water (LCZ G),respectively.At night,bare soil or sand (LCZ F) obtained the lowest LST,while the warmest zone was water (LCZ G).With the increasing of building height,daytime LST related to compact and open built-up types tended to decrease,and an opposite trend was observed at night.LCZs were differentiated better at night than during daytime.Moreover,regardless of day and night,open high-rise built-type (LCZ 4) and LCZ G were the most differentiated zones for built-up and land cover types,respectively.
    2022,14(3):277-286, DOI: 10.13878/j.cnki.jnuist.2022.03.003
    Abstract:
    Urban growth and shrinkage are the inevitable results of rapid urbanization.Excessive growth or shrinkage will bring problems such as resource mismatch and ecological environment deterioration.Based on the nighttime light data of China's districts and counties from 1992 to 2019,this paper explores the temporal and spatial dynamic characteristics and underlying causes of urban growth and shrinkage in China,with purpose to provide reference for policy-making on future urbanization,balanced allocation of resources and national development.The results show that urban growth and shrinkage alternate in China with increasingly obvious polarization between growth and shrinkage.Centered in Henan's Nanyang city,the urban growth is mainly a belt structure supplemented by points,in which the belts include the coastal urban belt and the recently formed "Beijing-Zhengzhou-Nanchang" urban belt,and the points refer to inland provincial capitals as agglomeration growth cores.While the urban shrinkage,centered in Shaanxi's Ankang city (shifted from Hebei's Xingtai city),has gradually changed from scattered point shrinkage to belted shrinkage along "Beijing-Xi'an-Chengdu-Kunming".The underlying reasons of urban growth and shrinkage in China include global financial cycle,industrial structure transformation,national policies,etc.
    2022,14(3):287-293, DOI: 10.13878/j.cnki.jnuist.2022.03.004
    Abstract:
    To select the interpolation algorithm for the refinement of Precipitable Water Vapor (PWV),this paper systematically analyzes three interpolation methods including the linear interpolation triangulation,the Kriging interpolation and the Inverse Distance Weighting (IDW) interpolation,and then proposes an improved IDW interpolation approach.First,both the influence of GNSS station distance and the distribution characteristics of atmospheric water vapor on the interpolation result is analyzed,which is then used to optimize the interpolation parameters thus make the interpolation result close to the high-precision observation value.Second,this approach is tested using GNSS data of Xuzhou continuously operated reference stations as well as the radiosonde data during the period of May to July 2017.The results demonstrate that the improved IDW interpolation approach outperforms the above three classical interpolation methods in standard deviation,mean absolute error,mean relative error,and Root Mean Square Error (RMSE).Specifically,the RMSE is lowered by 14.88%,15.70% and 4.12%,compared with the linear interpolation triangulation,the Kriging and the IDW interpolation,respectively.Moreover,the proposed interpolation approach has excellent ability in reconstructing the high-resolution atmospheric water vapor distribution map during storms,which can significantly reduce the interpolation error caused by the uneven distribution of sampling sites and the precipitation surge.The comparisons indicate that the improved IDW interpolation approach is conducive to reconstruct the high-resolution atmospheric water vapor distribution map for areas with sparse GNSS station network,thus to improve the capacity of extreme weather monitoring.
    2022,14(3):294-303, DOI: 10.13878/j.cnki.jnuist.2022.03.005
    Abstract:
    Based on monitoring data of atmospheric pollutants in Nanjing from Jan.1,2015 to Feb.10,2021,the spatial-temporal distribution characteristics of Nanjing's ambient air quality and the contribution of potential source areas were analyzed.The average concentrations of six air pollutants (CO,NO2,SO2,O3,PM10,and PM2.5) were 800 μg·m-3,43.1 μg·m-3,13.0 μg·m-3,106.0 μg·m-3,77.1 μg·m-3,and 43.0 μg·m-3,respectively.The average concentration of ozone in Nanjing was higher than that in China's other typical cities (Beijing,Shanghai,Guangzhou,Chengdu,Lanzhou,and Wuhan).The number of pollution days for NO2,PM10,and PM2.5 were reduced by 29.1%,38.1%,and 28.1% during 2015 to 2020.However,the frequency of ozone pollution days was increasing (the highest value in summer and the lowest value in winter).The potential source analysis of fine particulate matter in January of 2015-2020 was carried out.It was found that the potential source for Nanjing's PM2.5 was surrounding industrial areas (Anhui province,north of Jiangsu province,and Shandong province).The concentration of air pollutants in Nanjing in 2020 was lower than that in 2019 and 2021.It indicated that the reduction of human activity caused by COVID-19 pandemic has resulted in less air pollutant emissions and improved air quality in Nanjing.
    2022,14(3):304-316, DOI: 10.13878/j.cnki.jnuist.2022.03.006
    Abstract:
    Rigid-flexible robots are primarily composed of rigid components coupling with compliant material.Rigid robots have high rigidity and good controllability,while flexible robots have good toughness.The rigid-flexible coupled robots integrate both advantages,thus are promising in future development.Here,we introduce the coupled robots in aspects of their current development at home and abroad,and elaborate their three actuation modes:pneumatic driving,electro active polymer driving and shape memory alloy driving.We also focus on the modeling processes commonly used in coupled robots,especially the flexible ones,as well as the control algorithms for the coupled robots.Finally,the future development of rigid-flexible coupled robots is prospected.
    2022,14(3):317-323, DOI: 10.13878/j.cnki.jnuist.2022.03.007
    Abstract:
    This paper proposes an active control system for urban road traffic,with the purpose to provide a new way to realize the intelligent control of urban traffic and alleviate traffic congestion.The system is composed of four subsystems.The cloud-side-end support subsystem constitutes the basis of computing,communication and storage.The visualized hardware- and software-in-the-loop subsystem is the key to command,make decision,and exercise in traffic control.The real-time control subsystem and real-time simulation subsystem constitute the core of traffic control operation,which can guarantee the real-time and advanced traffic control.Instead of traditional passive control of intersection signals relying on cycle and green ratio adjustment,the system adopts an active control of intersections characterized with variable lanes,adjustable phase sequence and chain connection features.Experimental analysis shows that the system can effectively reduce the total delay time and average queue value of vehicles waiting on the traffic lights at the intersection.
    2022,14(3):324-330, DOI: 10.13878/j.cnki.jnuist.2022.03.008
    Abstract:
    The openness of wireless media has been a security threat for traditional wireless network based on security protocol.While the Radio Frequency Fingerprint (RFF) identification is based on physical layer security,and considering the RFF is impossible to forge,the RFF identification can effectively improve the security of wireless network.Aiming at the multi-scene and multi-device identification,an RFF identification approach is constructed based on attention residual convolution neural network.The dataset contains 32 Wi-Fi modules,covering the 2.4 GHz module of 802.11b standard.The comparison results show that the recognition accuracy of the proposed approach is 90% for the 32 Wi-Fi modules,higher than that of traditional algorithm (86%) and convolutional neural network approach (89%);the recognition accuracy can be higher than 90% on the dataset with different sampling rates when the SNR is greater than 2 dB,which can reach as high as 96% when the SNR is greater than 20 dB.
    2022,14(3):331-340, DOI: 10.13878/j.cnki.jnuist.2022.03.009
    Abstract:
    In order to achieve the goal of low power consumption and low latency for edge-end human activity recognition,this paper designs a fast recognition system based on wearable sensors and Convolutional Neural Networks (CNNs).First,the system collects data through sensors to make a human activity recognition dataset,and pre-trains a CNN-based behavior recognition model on the PC side,which achieves an accuracy of 93.61% on the test set.Then,hardware acceleration is realized through methods such as data fixed point,convolution kernel multiplexing,parallel processing of data,and pipeline.Finally,the recognition model is deployed on the FPGA,and the collected sensor data are input into the system to realize the recognition of human activity at the edge.The whole system is developed jointly with hardware and software based on Ultra96-V2.The experimental results show that when the input clock is 200 M,the system runs on FPGA with an accuracy of 91.80%;the proposed system is superior to CPU in recognition speed as well as power consumption,specifically,the power consumption is only one-tenth of CPU consumed,and energy consumption ratio is 91% higher than that of GPU.It can be concluded that the FPGA-based human activity recognition system meets the design requirements of low power consumption and low delay.
    2022,14(3):341-347, DOI: 10.13878/j.cnki.jnuist.2022.03.010
    Abstract:
    At present,high-dimensional (HD) feature detection is an effective approach to improve the detection performance of sea-surface small targets.The main difficulty lies in the design of classifier in high-dimensional space.Therefore,a feature detection approach based on false-alarm-controllable gradient boosting decision tree (GBDT) is proposed in this paper.First,multiple features are extracted from the 1D long-term observation vector in time,frequency,time-frequency domains to construct an HD feature vector.In this way,the detection problem is converted into a binary classification problem.Second,two types of balanced training samples are solved by simulating returns with target.Third,GBDT algorithm is introduced to condense the HD feature vector into 1D predicted value in probability.The predicted value is used as detection statistics to solve the problem of uncontrollable false alarm rate perplexed the binary classifier.Finally,experimental results are verified by IPIX measured data,which show that the proposed detector can make full use of all the information from the HD characteristics,and the performance is improved by over 13%.
    2022,14(3):348-360, DOI: 10.13878/j.cnki.jnuist.2022.03.011
    Abstract:
    Phase-Locked Loop (PLL) with a pre-filtering stage is a powerful tool to study the grid synchronization technology.However,the dynamic performance of this class of commonly used PLL (e.g.,second-order generalized integrator PLL,complex-coefficient filter PLL) is constrained by the low cut-off frequency of the front-stage structure.Thus,a three-phase PLL technique based on fractional-order generalized integrator is proposed.The front-stage filter of the PLL is composed of fractional-order integrators,which can generate two diagonal signals whose phase difference is 45°.Through the correlation linear operation,the positive- and negative-sequence components of the grid voltage can be extracted from the diagonal signals.Combined with the post-stage synchronous rotating frame PLL,a mathematical model of the entire PLL system is built,and the third order optimal design method is used to correct the system and determine the related control parameters.The study shows that,the cut-off frequency of the fractional-order generalized integrator is obviously higher than that of the second-order generalized integrator,which is helpful to improve the dynamic quality of the PLL system.The simulation and experimental results show that the dynamic performance of the proposed PLL is better than that of the multiple second-order generalized integrator PLL.
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    2014,6(5):405-419, DOI:
    [Abstract] (1656) [HTML] (0) [PDF 1.98 M] (20753)
    Abstract:
    With the rapid development of internet of things,cloud computing,and mobile internet,the rise of Big Data has attracted more and more concern,which brings not only great benefits but also crucial challenges on how to manage and utilize Big Data better.This paper describes the main aspects of Big Data including definition,data sources,key technologies,data processing tools and applications,discusses the relationship between Big Data and cloud computing,internet of things and mobile internet technology.Furthermore,the paper analyzes the core technologies of Big Data,Big Data solutions from industrial circles,and discusses the application of Big Data.Finally,the general development trend on Big Data is summarized.The review on Big Data is helpful to understand the current development status of Big Data,and provides references to scientifically utilize key technologies of Big Data.
    2013,5(5):385-396, DOI:
    [Abstract] (1450) [HTML] (0) [PDF 1.40 M] (7112)
    Abstract:
    Recently,coordinated control of multi-agent systems has been a hot topic in the control field,due to its wide application in cooperative control of multiple autonomous vehicles,traffic control of vehicles,formation control of unmanned aircrafts,resource allocation in networks and so on.Firstly,the introduction of background about multi-agent systems,the concepts of agents and the knowledge of the graph theory has been given.And then research status of swarming/flocking problems,formation control problems,consensus problems and network optimization are summarized and analyzed at home and abroad,including coordination control of multi-agent systems.Finally,some problems about multi-agent systems to be solved in future are proposed,in order to urge deep study on the theory and application in coordinated control of multi-agent systems.
    2010(5):410-413, DOI:
    [Abstract] (2262) [HTML] (0) [PDF 960.26 K] (6866)
    Abstract:
    设计了一个三维声源定位系统,提出了一个新的系统模型,并对传统的基于声波到达时间差TDOA的算法进行了优化。通过检测麦克风接收到信号的时间差,结合已知的阵列元的空间位置确定声源的位置。该系统声源采集部分由4个阵列成正四面体的麦克风组成。算法的硬件实现由TMS320C5416DSP芯片完成'整个系统实现了声源定位的功能。
    2017,9(2):159-167, DOI: 10.13878/j.cnki.jnuist.2017.02.006
    [Abstract] (1057) [HTML] (0) [PDF 1.56 M] (5408)
    Abstract:
    Various indoor positioning techniques have been developed and widely applied in both manufacturing processes and people's lives.Due to the electromagnetic interference and multipath effects,traditional Wi-Fi,Bluetooth and other wireless locating technologies are difficult to achieve high accuracy.Modulated white LED can provide both illumination and location information to achieve highly accurate indoor positioning.In this paper,we first introduce several modulation methods of visible light positioning systems and compare the characteristics of different modulation methods.Then,we propose a viable indoor positioning scheme based on visible light communications and discuss two different demodulation methods.In the following,we introduce several positioning algorithms used in visible light communication system.Finally,the problems and prospects of the visible light communication based indoor positioning are discussed.
    2012,4(4):351-361, DOI:
    [Abstract] (1333) [HTML] (0) [PDF 1.22 M] (5219)
    Abstract:
    In recent years,cloud computing as a new computing service model has become a research hotspot in computer science.This paper is to give a brief analysis and survey on the current cloud computing systems from the definition,deployment model,characteristics and key technologies.Then,the major international and domestic research enterprises and application products on cloud computing are compared and analyzed.Finally,the challenges and opportunities in current research of cloud computing are discussed,and the future directions are pointed out.So,it will help to provide a scientific analysis and references for use and operation of cloud computing.
    2017,9(2):174-178, DOI: 10.13878/j.cnki.jnuist.2017.02.008
    Abstract:
    With the deepening study of nonlinear effect in optical fiber,the distributed optical fiber sensor has been widely studied and applied.In this paper,the application of optical fiber sensor is introduced.To realize different types of fiber distributed sensing,the principle of three kinds of scattered light based on Brillouin scattering,Raman scattering,and Rayleigh scattering is summarized.Finally,the future development direction of fiber distributed sensing is prospected.
    2014,6(5):426-430, DOI:
    [Abstract] (1591) [HTML] (0) [PDF 1.04 M] (3755)
    Abstract:
    We propose a scheme to produce continuous-variable(CV) pair-entanglement frequency comb by nondegenerate optical parametric down-conversion in an optical oscillator cavity in which a multichannel variational period poled LiTaO3 locates as a gain crystal.Using the CV entanglement criteria,we prove that every pair generated from the corresponding channel is entangled.The characteristics of signal and idler entanglement are discussed.The CV pair-entanglement frequency comb may be very significant for the application in quantum communication and computation networks.
    2013,5(6):544-547, DOI:
    [Abstract] (915) [HTML] (0) [PDF 1.56 M] (3629)
    Abstract:
    On account of the power quality signal under stable state,this paper integrates the function of Hanning window with Fast Fourier Transform(FFT),and uses it to harmonic analysis for power quality.Matlab simulation is carried out for the feasibility of the proposed windowed FFT method,and results show that the integration of Hanning window function with FFT can significantly reduce the harmonic leakage,effectively weaken the interference between the harmonics,and accurately measure the amplitude and phase of power signal.
    2014,6(3):226-230, DOI:
    [Abstract] (869) [HTML] (0) [PDF 1.33 M] (3586)
    Abstract:
    As a modulation with relatively strong anti-interference capacity,quadrature phase shift keying(QPSK) has been extensively used in wireless satellite communication.This paper describes the Matlab simulation of QPSK demodulation,and designs an all-digital QPSK demodulation with FPGA.The core of demodulation is synchronization,which includes carrier synchronization and signal synchronization.The carrier synchronization is completed through numerical Costas loop,while signal synchronization through modulus square spectrum analysis,and the results are simulated on Matlab.The communication functions are implemented by upgradable or substitutable softwares as many as possible,based on the idea of software radio communication.The parameter values through Matlab simulation,combined with appropriate hardware system,technically realize the design of the proposed all-digital meteorological satellite demodulator based on FPGA.
    2011(1):1-22, DOI:
    [Abstract] (1788) [HTML] (0) [PDF 1.29 M] (3319)
    Abstract:
    System identification is the theory and methods of establishing mathematical models of systems.The mathematical modeling has a long research history,but the system identification discipline has only several tens of years.In this short decades,system identification has achieved great developments,new identification methods are born one after another,and the research results cover the theory and applications of natural science and social sciences,including physics,biology,earth science,meteorology,computer science,economics,psychology,political science and so on.In this context,we come back to ponder some basic problems of system identification,which is not without benefits for the development of system identification.This is a paper of an introduction to system identification which briefly introduces the definition of identification,system models and identification models,the basic steps and purposes of identification,including the experimental design of identification and data preprocessing,and the types of identification methods,including the least squares identification methods,gradient identification methods,auxiliary model based identification methods,and multi innovation identification methods,and hierarchical identification methods,etc
    2017,9(6):575-582, DOI: 10.13878/j.cnki.jnuist.2017.06.002
    [Abstract] (1314) [HTML] (0) [PDF 1.18 M] (3092)
    Abstract:
    Knowledge graph technology is widely concerned and studied during recent years,in this paper we introduce the construction methods,recent development of knowledge graph in details,we also summarize the interdisciplinary applications of knowledge graph and future directions of research.This paper details the key technologies of textual,visual and multi-modal knowledge graph,such as information extraction,knowledge fusion and knowledge representation.As an important part of the knowledge engineering,knowledge graph,especially the development of multi-modal knowledge graph,is of great significance for efficient knowledge management,knowledge acquisition and knowledge sharing in the era of big data.
    2013,5(5):414-420, DOI:
    [Abstract] (934) [HTML] (0) [PDF 1.04 M] (3073)
    Abstract:
    With the continuous increase of road vehicles,occasional congestion caused by traffic accidents seriously affect the commuting efficiency of traveler and the overall operation level of road network.Real-time and exact forecasting of short-term traffic flow volume is the key point to intelligent traffic system and precondition to solve the congestion situation by route guidance and clearing.According to the uncertain and non-linear features of traffic volume,a model integrated of the improved BP neural network and autoregressive integrated moving average (ARIMA) model is established to forecast the short-term traffic flow.The case application result shows that the combined model has an advantage over the single models in forecasting performance and forecasting accuracy.
    2014,6(6):515-519, DOI:
    Abstract:
    This paper proposes a two-step detection scheme that begins thick and ends thin,to mine the outliers of multivariable time series (MTS).According to the confidence interval of the data in sliding window,characteristics of both variation trend value and relevant variation trend value were constructed,which were then used in the two detection processes.Meanwhile,the rapid extraction algorithm for characteristics is studied.The outlier detection scheme is then applied to mine outliers before and after an accident happened at a 110 kV Grid Transformer Substation in Jiangsu province.Data sets of various equipment tables,which were collected by OPEN3000 data surveillance system,were checked by the proposed detection scheme,and experiment result indicates that this algorithm can rapidly and precisely locate the outliers.

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