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Stability Robustness of Control System in Angular Metric

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Stability Robustness of Control System in Angular Metric

Determination of potential management zones from soil electrical conductivity,yield and crop data

第25届中国控制与决策会议

作者： Bin Liu Wei-fang ci Bo-wen Huo School of Electrical and Information Engineering Northeast Petroleum University 91451 Troops

ISBN: (纸本)9781467355339

The robust control theory based on -norm is the successful example of solving the robust control problem, which has become a fairly systematic theory. However, -norm can only be used to measure the distance between two stable systems not the unstable systems. Sometimes, it is not appropriate to measure the gap of two stable systems. A new metric, angular metric, is defined in linear spaces of real rational matrices, which can measure the uncertainties and describe the performance specifications of the robust control system. In the framework of this metric, robust stability margin is proposed to characterize the stability robustness of the closed-loop system. When both the plant and the controller have uncertainties simultaneously, we introduce the structural robust stability, and prove the necessary and sufficient conditions of the robust stability of the feedback control system.

关键词： Stability Robustness Unitarily Invariant Norm Angular Metric

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2008年第1期9卷 68-76页

作者： Yan LI Zhou SHI ci-fang WU Hong-yi LI Feng LI College of Southeast Land Management Zhejiang University Hangzhou 310029 China Institute of Agricultural Remote Sensing and Information Technology Application Zhejiang University Hangzhou 310029 China Department of Environmental Engineering Zhejiang University Hangzhou 310029 China

One approach to apply precision agriculture to optimize crop production and environmental quality is identifying management zones. In this paper,the variables of soil electrical conductivity (EC) data,cotton yield data and normalized differ-ence vegetation index (NDVI) data in an about 15 ha field in a coastal saline land were selected as data resources,and their spatial variabilities were firstly analyzed and spatial distribution maps constructed with geostatistics technique. Then fuzzy c-means clustering algorithm was used to define management zones,fuzzy performance index (FPI) and normalized classification entropy (NCE) were used to determine the optimal cluster numbers. Finally one-way variance analysis was performed on 224 georefer-enced soil and yield sampling points to assess how well the defined management zones reflected the soil properties and produc-tivity level. The results reveal that the optimal number of management zones for the present study area was 3 and the defined management zones provided a better description of soil properties and yield variation. Statistical analyses indicate significant differences between the chemical properties of soil samples and crop yield in each management zone,and management zone 3 presented the highest nutrient level and potential crop productivity,whereas management zone 1 the lowest. Based on these findings,we conclude that fuzzy c-means clustering approach can be used to delineate management zones by using the given three variables in the coastal saline soils,and the defined management zones form an objective basis for targeting soil samples for nutrient analysis and development of site-specific application strategies.

关键词： Management zones Fuzzy clustering Spatial variability Saline land Precision agriculture

Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar

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Journal of Environmental Sciences 2015年第3期27卷 106-114页

作者： ci fang Tao Zhang Ping Li Rongfeng Jiang Shubiao Wu Haiyu Nie Yingcai Wang Key Laboratory of Plant–Soil Interactions of Ministry of Education College of Resources and Environmental SciencesChina Agricultural University College of Engineering China Agricultural University College of Science China Agricultural University

Shortage in phosphorus （P） resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar （Ca-Mg/biochar） application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63 mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600 〉 Ca-Mg/B4S0 〉 Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment.

关键词： Phosphorus Ca-Mg loaded biochar Biogas fermentation liquid Recovery

Changes of forest land use and ecosystem service values along Lao-Chinese border:A case study of Luang Namtha Province,Lao PDR

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Forestry Studies in China 2009年第2期11卷 85-92页

作者： Hemmavanh CHANHDA WU ci-fang Yoshida AYUMI Department of Land Resource Management Zhejiang University Hangzhou 310029 P. R. China Zhejiang University Tea Research Institute Hangzhou 310029 P. R. China

Forest cover and land use change directly impact biological diversity worldwide, contribute to climate change and affect the ability of biological systems to support human needs by altering ecosystem services. Given the forest land use characteristics and ecosystem types in Luang Namtha Province, Lao PDR, the forest cover and land cover category of Luang Namtha Province were divided into six classes, i.e., current forest （CF）, potential forest （PF）, other wooded areas （OW）, permanent agricultural land （PA）, other non-forest areas （NF） and water （W）. In first instance, earlier geographic information data （GIS data） of forest cover and land use during 1992 and 2002 was obtained from the Ministry of Agriculture and Forestry （MAF）, Lao PDR. Two steps of forest land use change assessment were conducted by the MAF, i.e., plot sampling on satellite image maps （SIMs） to detect the changes of forest cover and land use during 1992 and 2002 for the entire Luang Namtha Province and field verification in order to identify causes of the changes. Secondly, dynamic information of the forest land cover changes during this ten-year period was calculated by means of map algebra in ArcGIS 9.2. Thirdly, based on the theory of ecosystem service functions and the service function values of different global ecosystems, the value of the six forest cover and land use categories in the province was obtained. Finally, ecological environmental effects, produced by the regional land cover changes over the study period, were calculated.

关键词： ecosystem services forest land use Luang Namtha Lao PDR

Effectiveness of urban construction boundaries in Beijing:an assessment

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第9期10卷 1285-1295页

作者： Hao-ying HAN Shih-Kung LAI An-rong DANG Zong-bo TAN ci-fang WU College of Public Administration Zhejiang University Hangzhou 310029 China School of Architecture Tsinghua University Beijing 100084 China Department of Real Estate and Built Environment National Taipei University Taipei

Based on the remote sensing (RS) and geographic information system (GIS) analysis of the Landsat multispectral scanner (MSS) and thematic mapper (TM) satellite images of 1983, 1993, and 2005, the present research examined the effectiveness of the urban construction boundaries (UCBs) in containing urban growth within the 6th Ring Road of Beijing Municipality. Three indicators on boundary control were proposed, through which the effectiveness of boundary containment, land inventory sufficiency and illegal adjacent development to the UCBs were explored. The results suggested that, first, the UCBs were limited in effectiveness in containing urban growth; second, the area encompassed by the UCBs might not be designed large enough to accommodate new development. The frustration of the urban growth control through the UCBs mainly resulted from the lack of a transparent system for urban land use planning and control to provide sufficient information, the limitation of the traditional land use prediction method to consider contingencies, and the absence of a mechanism to monitor and adjust the UCBs to respond just in time to urban change.

关键词： Urban construction boundary (UCB) Urban growth boundary city master plan (CMP) Beijing Remote sensing (RS)

Quantification of the effects of management factors on maize (Zea mays L.) and cotton(Gossypium hirsutum L.) residues decomposition rate

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Journal of Environmental Sciences 2002年第2期14卷 165-172页

作者： JONES Chilima, HUANG Chang yong, WU ci fang (College of Natural Resources and Environment, Zhejiang University, Hangzhou 310029, China. College of Natural Resources and Environment Zhejiang University Hangzhou 310029 China

Efforts to quantify management effects on decomposition rate of added substrates to the soil is important especially where such information is to be used for prediction in mathematical or simulation models. Using data from a short term (60 days) greenhouse simulation study, a procedure for quantifying effects of management on SOM and substrate decomposition is presented. Using microbial growth rate u (q), microbial efficiency in substrate utilization e (q), specific decomposition rates for added plant residues to two contrasting soils, red earth (Ferrasol) and black earth (Acrisol) were estimated. The treatments included straw addition + buried, (T1); straw addition + mineral N (T2); and straw addition + tillage, (T3). Sampling was done every 15 days. Straw decomposition rate was affected by external mineral N sources (Urea 46% N). Addition of an external N source significantly increased decomposition rates. The study could not, however, fully account for the effect of tillage on residues because of the limited effect of the tillage method due to the artificial barrier to mechanical interference supplied by the mesh bags. It is concluded that using few decomposer parameters, decomposition rates and consequently SOM trends in a soil system can be monitored and quantification of the influence of perturbations on decomposition rate of added substrates possible.

关键词： management factors residue decomposition rate maize cotton red soil black soil

Improved Prediction and Reduction of Sampling Density for Soil Salinity by Different Geostatistical Methods

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Agricultural Sciences in China 2007年第7期6卷 832-841页

作者： LI Yan SHI Zhou WU ci-fang LI Hong-yi LI Feng Institute of Land Science and Property Management College of Southeast Land Management Zhejiang University Hangzhou 310029 P. R. China Institute of Agricultural Remote Sensing and Information Technology Application College of Environmental and Resource Sciencea Zhejiang University Hangzhou 310029 P.R. China Department of Environmental Engineering Zhejiang University Hangzhou 310029 P.R. China

The spatial estimation for soil properties was improved and sampling intensities also decreased in terms of incorporated auxiliary data. In this study, kriging and two interpolation methods were proven well to estimate auxiliary variables： cokriging and regression-kriging, and using the salinity data from the first two stages as auxiliary variables, the methods both improved the interpolation of soil salinity in coastal saline land. The prediction accuracy of the three methods was observed under different sampling density of the target variable by comparison with another group of 80 validation sample points, from which the root-mean-square error （RMSE） and correlation coefficient （r） between the predicted and measured values were calculated. The results showed, with the help of auxiliary data, whatever the sample size of the target variable may be, cokriging and regression-kriging performed better than ordinary kriging. Moreover, regression-kriging produced on average more accurate predictions than cokriging. Compared with the kriging results, cokriging improved the estimations by reducing RMSE from 23.3 to 29% and increasing r from 16.6 to 25.5%, regression-kriging improved the estimations by reducing RMSE from 25 to 41.5% and increasing r from 16.8 to 27.2%. Therefore, regression-kriging shows promise for improved prediction for soil salinity and reduction of soil sampling intensity considerably while maintaining high prediction accuracy. Moreover, in regression-kriging, the regression model can have any form, such as generalized linear models, non-linear models or tree-based models, which provide a possibility to include more ancillary variables.

关键词： auxiliary data prediction precision sampling density soil salinity kriging

Optimised Spatial Sampling Scheme for Soil Electriclal Conductivity Based on Variance Quad-Tree (VQT) Method

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Agricultural Sciences in China 2007年第12期6卷 1463-1471页

作者： LI Yan SHI Zhou WU ci-fang LI Feng LI Hong-yi Institute of Land Science and Property Management College of Southeast Land Management Zhejiang University Hangzhou 310029 P.R.China Institute of Agricultural Remote Sensing and Information Technology Application College of Environmental and Resource Sciences Zhejiang University Hangzhou 310029 P.R.China Department of Environmental Engineering Zhe.iiang University Hangzhou 310029 P.R.China

The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.

关键词： variance quad-tree (VQT) sampling scheme spatial variability kriging interpolation precision agriculture

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注入式混合型有源电力滤波器稳定性研究

电力自动化设备 2007年第12期27卷 21-25页

作者：汤赐湖南大学电气与信息工程学院湖南长沙410082

在介绍注入式混合型有源电力滤波器的拓扑结构及控制策略的基础上,提出了该有源电力滤波器的数学模型,并利用该模型对系统的稳定性进行深入分析。从谐波抑制效果出发,有源电力滤波器放大倍数K的取值越大越好;但是系统中的延时环节、电... 详细信息

在介绍注入式混合型有源电力滤波器的拓扑结构及控制策略的基础上,提出了该有源电力滤波器的数学模型,并利用该模型对系统的稳定性进行深入分析。从谐波抑制效果出发,有源电力滤波器放大倍数K的取值越大越好;但是系统中的延时环节、电网电感参数和无源电力滤波器参数均限制了K的取值范围,从而共同决定了有源电力滤波器实际能够投入的最大容量。分析表明:系统中的延时越小、无源电力滤波器及电网的电感参数越大,则最大放大倍数Kmax越大,谐波抑制效果越好;无源部分对Kmax影响有限。实验结果证明了理论分析的正确性。

关键词：注入式混合型有源电力滤波器稳定性

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