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Zhangye, China

Du Y.-F.,Lanzhou University of Technology | Li C.-F.,Lanzhou University of Technology | Li C.-F.,Hexi College | Li H.,Lanzhou University of Technology
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

Based on the non-uniqueness of control force matrix for structural active control pole assignment, an optimal pole assignment algorithm was proposed. The main difference between the performances of the algorithm and the classical LQR optimal active control was that structural active control weighted matries Q and R did not affect the proposed algorithm, so the new algorithm had obvious physical or engineering significance. Firstly, compared to the relationships among mathematical models of structural active control systems, based on the uniqueness of the transfer function matrix, the optimal zero-pole assignment was achieved in a complex plane. Secondly, the target transfer function matrix used to calculate its minimum state equation was established based on the expectative zero-pole, then the optimal pole assignment for structural active control was achieved. Finally, this algorithm's effectiveness and practicability were proved through an example.

Guo Y.-Y.,Hexi College | Yu H.-Y.,Hexi College | Kong D.-S.,Hexi College | Yan F.,Hexi College | Zhang Y.-J.,Hexi College
Photosynthetica | Year: 2016

The present study aimed to determine effects of drought stress on Lycium ruthenicum Murr. seedlings. Our results showed that mild drought stress was beneficial to L. ruthenicum seedling growth. The height, basal diameter, crown, leaf number, stem dry mass, leaf and root dry mass increased gradually when the soil water content declined from 34.7 to 21.2%. However, with further decrease of the soil water content, the growth of L. ruthenicum seedlings was limited. After 28 d of treatment, the L. ruthenicum seedlings were apparently vulnerable to drought stress which resulted in significant leaf shedding and low growth. However, growth was restored after rehydration. Drought treatments led to a decrease in contents of chlorophyll (Chl) a, b, and Chl (a+b) and increase in the Chl a/b ratio. After rewatering, the Chl content recover to the level of the control plants. Under drought stress, minimal fluorescence and nonphotochemical quenching coefficient increased, thereby indicating that L. ruthenicu seedling could protect PSII reaction centres from damage. Maximum fluorescence, maximum quantum yield, actual quantum yield of PSII photochemistry, and photochemical quenching decreased, which suggested that drought stress impacted the openness of PSII reaction centres. A comparison of these responses might help identify the drought tolerance mechanisms of L. ruthenicum. This could be the reference for the planting location and irrigation arrangements during the growing period of L. ruthenicum. © 2016 The Institute of Experimental Botany

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