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Spatiotemporal changes in vegetation net primary productivity in the arid region of Northwest China, 2001 to 2012

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Frontiers of Earth Science 2018年第1期12卷 108-124页

作者： Zhen LI jinghu PAN College of Geographic and Environmental Science Northwest Normal University Lanzhou 730070 China

Net primary productivity （NPP） is recognized as an important index of ecosystem conditions and a key variable of the terrestrial carbon cycle. It also represents the comprehensive effects of climate change and anthropogenic activity on terrestrial vegetation. In this study, the temporal-spatial pattern of NPP for the period 2001-2012 was analyzed using a remote sensing-based carbon model （i.e., the Carnegie-Ames-Stanford Approach, CASA） in addition to other methods, such as linear trend analysis, standard deviation, and the Hurst index. Temporally, NPP showed a significant increasing trend for the arid region of Northwest China （ARNC）, with an annual increase of 2.327 g C. Maximum and minimum productivity values appeared in July and December, respectively. Spatially, the NPP was relatively stable in the temperate and warmtemperate desert regions of Northwest China, while temporally, it showed an increasing trend. However, some attention should be given to the northwestern warm-temperate desert region, where there is severe continuous degradation and only a slight improvement trend.

关键词： NPP CASA model remote sensing aridregion of Northwest China (ARNC)

Spatial Identification of Housing Vacancy in China

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Chinese Geographical Science 2021年第2期31卷 359-375页

作者： PAN jinghu DONG Leilei College of Geography and Environmental Sciences Northwest Normal UniversityLanzhou 730070China Northwest Institute of Eco-Environment and Resources Lanzhou 730000China

The housing vacancy rate(HVR)is an important index in assessing the healthiness of residential real estate *** China,it is hardly to take advantage of the basic data of real estate information due to the opaque of those *** this paper,the HVR is estimated to two *** the grid level,urban area ratio was calculated by nighttime images after eliminating outliers of nighttime images and night light intensity of non-residential pixels in mixed pixels by a proposed modified optimal threshold method,and built-up areas in each pixel were extracted from the land-cover ***,the HVR is calculated by comparing the light intensity of specific grid with the light intensity of full occupancy rate *** the administrative scale,the GCI(‘ghost city’index)is constructed by calculating the ratio of the total light radiation intensity of a city to the total construction land area of the *** overall spatial differentiation pattern of the vacant houses in the national prefecture level administrative regions is *** following conclusions were drawn:vacant housing is rare in certain eastern coastal cities and regions in China with relatively fast economic *** based on exhausted resources,some mountainous cities,and cities with relatively backward economic development more typically showed high levels of housing *** GCI of prefecture-level administrative units gradually declined from north to south,whereas the east-west distribution showed a parabolic *** city level decreased,the GCI registered a gradual upward ***’s urban housing vacancy can be divided into five categories:industry or resources driven,government planned,epitaxy expansionary,environmental constraint and speculative activate by combining the spatial distribution of housing vacancy with the factors of natural environment,social economic development level,and population density into consideration.

关键词： housing vacancy rate(HVR) spatial identification nighttime light spatial pattern ghost city China

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一维任意子Stark模型的多体局域化

物理学报 2025年第4期74卷 24-30页

作者：游慧敏刘敬鹄张云波徐志浩山西大学理论物理研究所量子光学与光量子器件国家重点实验室太原030006 忻州师范学院物理系忻州034000 浙江理工大学物理系浙江省光场调控重点实验室杭州310018 山西大学极端光学协同创新中心太原030006

本文研究了具有Stark势的一维相互作用任意子模型.通过数值计算能谱统计、半链纠缠熵和粒子非平衡态占据数等来观测有限尺寸下的多体局域化现象.随着线性势强度的增强,系统的能谱统计分布从高斯系综向泊松系综过渡,过渡区域的平均能级... 详细信息

本文研究了具有Stark势的一维相互作用任意子模型.通过数值计算能谱统计、半链纠缠熵和粒子非平衡态占据数等来观测有限尺寸下的多体局域化现象.随着线性势强度的增强,系统的能谱统计分布从高斯系综向泊松系综过渡,过渡区域的平均能级差比率表现为强烈依赖于统计角的非单调行为.平均半链纠缠熵服从体积律到面积律转变且转变点对统计角有非单调依赖关系,遍历相的半链纠缠熵随时间线性增长,而在局域相中随时间呈对数增长,其演化行为也与统计角有关.最后随着线性势增大,长时极限下粒子非平衡态占据数由零变为有限值,有限值的大小与任意子统计角的取值有关,这种演化行为进一步验证了任意子模型中统计角的重要性.该研究结果为任意子系统中多体局域化的研究提供了新的视角.

关键词：任意子 Stark 势多体局域化

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棒束通道中边棒和角棒环状流扰动波特性研究

核动力工程 2025年第1期46卷 143-151页

作者：金光远白镜湖王睿李伟链杜利鹏张文超东北电力大学能源与动力工程学院吉林吉林132012 东北电力大学热流科学与核工程实验室吉林吉林132012

研究棒束通道中边棒和角棒环状流扰动波特性,可为核电厂稳态运行和应急处置提供理论支撑。本研究建立棒束通道中环状流可视化实验系统,对边棒和角棒表面扰动波特性进行分析。结果表明,扰动波形态可以分成小尺度波、包状扰动波、带状扰... 详细信息

研究棒束通道中边棒和角棒环状流扰动波特性,可为核电厂稳态运行和应急处置提供理论支撑。本研究建立棒束通道中环状流可视化实验系统,对边棒和角棒表面扰动波特性进行分析。结果表明,扰动波形态可以分成小尺度波、包状扰动波、带状扰动波和带状破碎波4种;液相折算速度保持不变时,平均液膜厚度随气相折算速度增加而变小,当液相折算速度逐渐变大时,平均液膜厚度数值也逐渐变大;扰动波波高随气相折算速度增加而变小,边棒表面扰动波高度低于角棒的值。当液相折算速度低于0.41 m/s时,扰动波波速随着气、液相折算速度增加而变大;当液相折算速度高于0.41 m/s时,扰动波波速高于气相折算速度。扰动波波频随气相折算速度增加而变大,随液相折算速度变化规律不明显,这取决于波动形态的变化。边棒和角棒表面液膜厚度数据的熵均值随着扰动波形态从小尺度波、包状扰动波、带状扰动波到带状破碎波逐步增加,因此可以使用多尺度排列熵分析方法判定棒束通道中扰动波形态。

关键词：棒束通道环状流扰动波多尺度排列熵

Research on modeling and self-excited vibration mechanism in magnetic levitation-collision interface coupling system

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 873-890页

作者： jinghu TANG Chaofeng LI Jin ZHOU Zhiwei WU School of Mechanical Engineering&Automation Northeastern UniversityShenyang 110819China Key Laboratory of Vibration and Control of Aero-Propulsion Systems of Ministry of Education of China Northeastern UniversityShenyang 110819China School of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The modeling and self-excited vibration mechanism in the magnetic levitation-collision interface coupling system are *** effects of the control and interface parameters on the system's stability are *** frequency range of self-excited vibrations is investigated from the energy point of *** phenomenon of self-excited vibrations is elaborated with the phase *** corresponding control strategies are briefly analyzed with respect to the vibration *** results show that when the levitation objects collide with the mechanical interface,the system's vibration frequency becomes larger with the decrease in the collision gap;when the vibration frequency exceeds the critical frequency,the electromagnetic system continues to provide energy to the system,and the collision interface continuously dissipates energy so that the system enters the self-excited vibration state.

关键词： magnetic levitation coupling system self-excited vibration mechanical interface vibration frequency

Reduce Training Error of Extreme Learning Machine by Selecting Appropriate Hidden Layer Output Matrix

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Journal of Systems Science and Systems Engineering 2021年第5期30卷 552-571页

作者： Yang Lv Bang Li jinghu Yu Yiming Ding School of Science Wuhan University of TechnologyWuhan 430070China Center for Mathematical Sciences Wuhan University of TechnologyWuhan 430070China

Extreme learning machine(ELM)is a feedforward neural network with a single layer of hidden nodes,where the weight and the bias connecting input to hidden nodes are randomly *** output weight between hidden nodes and outputs are learned by a linear *** is interesting to ask whether the training error of ELM is significantly affected by the hidden layer output matrix H,because a positive answer will enable us obtain smaller training error from better *** single hidden layer feedforward neural network(SLFN)with one input neuron,there is significant difference between the training errors of different *** find there is a reliable strong negative rank correlation between the training errors and some singular values of the Moore-Penrose generalized inverse of *** on the rank correlation,a selection algorithm is proposed to choose robust appropriate H to achieve smaller training error among numerous *** experiments are carried out to validate the selection algorithm,including tests on real data *** results show that it achieves better performance in validity,speed and robustness.

关键词： ELM SLFNs training error Moore-Penrose generalized inverse selection algorithm

Effects of mechanical interfaces on magnetic levitation systems and analysis of self-excited vibration mechanisms in coupled systems

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Science China(Technological Sciences) 2024年第12期67卷 3925-3939页

作者： TANG jinghu LI ChaoFeng ZHOU Jin WU ZhiWei School of Mechanical Engineering&Automation Northeastern UniversityShenyang 110819China Key Laboratory of Vibration and Control of Aero-Propulsion Systems Ministry of Education of China Northeastern University Shenyang 110819China School of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 20016China

Magnetic levitation is a non-self-stabilizing system that requires high control *** system's stability is affected by the mechanical interface between the levitation object and the loading device,with self-excited vibration generated in the operation *** paper proposes to consider the mechanical behavior of the contact interface in the magnetic levitation *** electromagnetic and control systems are mechanically equivalent,the coupled electric-magnetic-mechanical model is established by adopting the lumped mechanical modeling ***,the effect of the contact clearance on the mechanical behavior of the system is analyzed using the Routh-Hurwitz *** research results show that with the decrease in the contact clearance,the vibration frequency *** the vibration frequency exceeds the critical value,a continuous vibration phenomenon occurs in the system under the joint action of feedback and energy ***,the effect of interface parameters on the vibration characteristics is analyzed using the fourth-order Runge-kutta numerical *** analyses show that the interface contact leads to combination frequency and frequency multiplication components in the coupled system.

关键词： magnetic levitation coupled systems self-excited vibrations mechanical interfaces nonlinear vibrations

Numerical simulation of non-Gaussian wind load

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Science China(Technological Sciences) 2012年第11期55卷 3057-3069页

作者： YE JiHong DING jinghu LIU ChuanYan Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education Southeast UniversityNanjing 210018China

Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.

关键词： non-Gaussian wind load power spectrum skewness kurtosis numerical simulation

Analysis of structural characteristics and spatial distribution of the national intangible cultural heritage in China and its policy implications

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Research in Cold and Arid Regions 2019年第5期11卷 389-406页

作者： BaiCui Xu jinghu Pan College of Geography and Environmental Science of Northwest Normal University

Based on an investigation of four published batches listing 3, 140 national intangible cultural heritage(ICH) projects in China and using GIS and some quantitative analysis methods, the spatial structure was investigated and the characteristics and distribution discussed. The distribution of ICHs in China is agglomerative and spatially dependent. From the view of ICH type, each type is distributed in different places, for different reasons, with history being the most important one we found. Nationwide, high-density cores are located in the Beijing-Tianjin-Hebei region and the Yangtze River Delta region. High densities of ICH are concentrated in flat, water-rich regions where broad-leaved forests dominate plains and low mountain areas-areas that have fertile soil, pleasant weather, a long history of culture, ethnic agglomeration, and development. This paper suggests that development of the ICH should be based on discovering unknown items, to break the existing pattern of strong cohesion and high density, and to seek a balanced development of the whole.

关键词： national intangible culture heritage ICH spatial structure influencing factor geographical distribution China