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Impact of time lags on diurnal estimates of canopy transpiration and canopy conductance from sap-flow measurements of Populus cathayana in the Qinghai–Tibetan Plateau

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Journal of Forestry Research 2017年第3期28卷 481-490页

作者： Hui Wang Kangning He Runjie Li Zhuping Sheng Yun Tian Jun Wen Bo Chang Key Laboratory of State Forestry Administration on Soil and Water Conservation Beijing Forestry UniversityBeijing 100083China Institute of Water Resources and Hydropower of Qinghai Province Xining 810001China Texas A&M AgriLife Research Texas A&M UniversityEL PasoCollege StationTX 77843USA

Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance （gc） and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to pararneterize Jarvistype models of gc and thus to simulate Ec of Populus cathayana using the Penman-Monteith equation. The results indicate that solar radiation （Rs） and vapor pressure deficit （VPD） are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rs and precedes VPD, and there is a 1-h time shift between Eo and sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in go, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error （RMSEs） between the predicted and measured Ec were 1.91×10^-3 （with the time lag） and 3.12×10^-3cm h^-1 （without the time lag）. More importantly, Ec simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error （MRE） of only 8.32% and the mean absolute error （MAE） of 1.48 × 10^-3 cm h^-1.

关键词： Canopy transpiration Model - Populuscathayana Qinghai-Tibetan Plateau Sap flow time lags

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A Neighborhood Search Algorithm for One-machine Scheduling Problem with time lags

A Neighborhood Search Algorithm for One-machine Scheduling P...

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2009中国控制与决策会议

作者： Zhao Ruiguo~1,Li Jiejia~2 1.LiaoNing Urban Construction School,Shenyang 110015,China 2.College of Information & Control Engineering,Shenyang institute of Architectural and Civil Engineering,Shenyang 110168,China

The one-machine scheduling problem with time lags while minimizing the completion time is NP-hard.The problem typically arises in a manufacturing where the next job has to be carried out in a specific time window after the completion of the immediately proceeding job.Scheduling the jobs is to find a shortest path that passes all the nodes and meets all precedence constraints and time lags constraints on AON(Activity-On-Node) net.A nonlinear mathematic optimization model is established based on AON net.A neighborhood search algorithm is proposed to convert the nonlinear model into a linear programming model that could be solved by standard software. Computational results prove that the proposed neighborhood search algorithm is effective.

关键词： One-machine Scheduling time lags Neighborhood Search Algorithm and AON Net

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Grey interpolation approach for small time-lag samples based on grey dynamic relation analysis

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Journal of Systems Engineering and Electronics 2018年第1期29卷 105-115页

作者： WANG Junjie DANG Yaoguo XU Ning DING Song College of Economics and Management Nanjing University of Aeronautics and Astronautics College of Management Science and Engineering Nanjing Audit University

Given a non-equidistant sequence or an equidistant series with one or more outliers, a grey interpolation approach considering the time lags is established for producing the missing data or correcting the abnormal values. To accomplish this, a new grey incidence model, called the grey dynamic incidence model GDIM(t), is constructed for determining whether the factors are effective to the known factor and what the time lag is between a useful factor and the specified sequence. Based on the results of the GDIM(t) model, two programming problems are designed to obtain the upper and lower bounds of the unknown or abnormal values which are regarded as grey numbers. The solutions based on the particle swarm optimization(PSO) for the nonlinear programming problems are given. To explain how it can be used in practice, this new grey interpolation approach is applied to correct an abnormal value in the sequence of an agriculture environment problem.

关键词： grey interpolation grey relational analysis time lags programming problems

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