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111.
S.A. Jalali M. Banazadeh E. Tafakori A. Abolmaali 《Journal of Constructional Steel Research》2011,67(8):1261-1271
Seismic performance of Steel Moment-Resisting Frames (SMRFs) with generic Locally-Reinforced (LR) connections has been investigated incorporating both earthquake-induced and modeling uncertainties. The LR connections were numerically modeled following the suggestions made by previous researches and were used to numerically model three buildings with various heights which were designed regarding the specifications of current standards. For reflecting the record-to-record (RTR) variability, the Incremental Dynamic Analysis (IDA) procedure was utilized within the Performance-Based Earthquake Engineering (PBEE) methodology. In this regard, the structures’ performance in a multitude of structural response levels was probabilistically assessed in “considering” and “neglecting” conditions of modeling uncertainties. For performing the modeling uncertainty analysis, a number of modeling parameters that best reflected the structures’ variability due to lack of knowledge were selected as random variables. Perturbing the modeling variables from their median values, a set of sensitivity IDAs were performed and a polynomial response surface was established. Incorporation of the response surface in conjunction with Monte Carlo simulation led, finally, to a fully probabilistic performance evaluation of the studied structures in varied structural response levels. The effect of modeling uncertainties in altering the predicted performances was found to be insignificant in the range of buildings and structural elements studied in this article. 相似文献
112.
Lixian Zhang Peng Shi Changhong Wang Huijun Gao 《International Journal of Adaptive Control and Signal Processing》2006,20(6):291-304
In this paper, the problem of robust H∞ filtering for switched linear discrete‐time systems with polytopic uncertainties is investigated. Based on the mode‐switching idea and parameter‐dependent stability result, a robust switched linear filter is designed such that the corresponding filtering error system achieves robust asymptotic stability and guarantees a prescribed H∞ performance index for all admissible uncertainties. The existence condition of such filter is derived and formulated in terms of a set of linear matrix inequalities (LMIs) by the introduction of slack variables to eliminate the cross coupling of system matrices and Lyapunov matrices among different subsystems. The desired filter can be constructed by solving the corresponding convex optimization problem, which also provides an optimal H∞ noise‐attenuation level bound for the resultant filtering error system. A numerical example is given to show the effectiveness and the potential of the proposed techniques. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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114.
The effect of uncertainties in Kuhn-Mark-Houwink-Sakurada (KMHS) constants on weight average and number average molecular weights and molecular weight distributions of some poly(ethyl methacrylate) samples have been investigated. Parameters were computed by the Weiss and Cohn-Ginsberg method. Whereas errors introduced in Mw, Mn and HI values due to uncertainty in the K value are insignificant, uncertainties in the KMHS exponent present a serious problem. Deviations of ± 3% around a particular a value cause a ± 20% error in Mw and ± 15% error in Mn, values. The effect of deviations in the KMHS exponent on the HI values is dependent on the polydisperity of the sample investigated. 相似文献
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116.
R.N. Jacobs L.A. Almeida J. Markunas J. Pellegrino M. Groenert M. Jaime-Vasquez N. Mahadik C. Andrews S.B. Qadri T. Lee M. Kim 《Journal of Electronic Materials》2008,37(9):1480-1487
It is well known that the large lattice mismatch (>14%) associated with CdTe/Si, CdTe/Ge, and CdTe/GaAs composite substrates,
is a great contributor to large dislocation densities and other defects that limit the performance of HgCdTe-based infrared
detectors. Though thermal expansion mismatch is another possible contributor to material defects, little work has been done
towards documenting and understanding its effects in these systems. Here, we perform studies to determine the relative contributions
of lattice and thermal mismatch to CdTe film characteristics, including dislocation density and residual stress. Unannealed
and thermally cycled films are characterized using x-ray diffraction, defect decoration, and Nomarski and transmission electron
microscopy. For CdTe/Si, the residual stress is consistently observed to be tensile, while for CdTe/Ge and CdTe/GaAs, a compressive
residual film stress is measured. We show based on theoretically predicted stress levels that the experimental measurements
imply the dominance of thermal mismatch in the residual stress characteristics. 相似文献
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118.
最近电压稳定临界点的两层规划模型和信赖域算法 总被引:1,自引:1,他引:0
考虑了负荷变化的不确定性,提出负荷分布范围的棱锥状模型。建立了求解最近电压稳定临界点的非线性二层规划模型,提出一种求解该问题的信赖域方法。该方法先计算已知负荷增长方向上的电压稳定临界点,然后建立只有上、下界约束的近似模型,基于信赖域方法的思想迭代搜索最近电压稳定临界点,求取临界点时考虑了发电机无功出力的限制。算例分析表明,该算法收敛速度快、鲁棒性好,全局寻优能力强,并可找出系统电压稳定的薄弱区域和母线。 相似文献
119.
This paper focuses on the current control of a permanent magnet synchronous motor (PMSM) for electric drives with model uncertainties and external disturbances. To improve the performance of the PMSM current loop in terms of the speed of response, tracking accuracy, and robustness, a hybrid control strategy is proposed by combining the adaptive sliding mode control and sliding mode disturbance observer (SMDO). An adaptive law is introduced in the sliding mode current controller to improve the dynamic response speed of the current loop and robustness of the PMSM drive system to the existing parameter variations. The SMDO is used as a compensator to restrain the external disturbances and reduce the sliding mode control gains. Experiments results demonstrate that the proposed control strategy can guarantee strong anti-disturbance capability of the PMSM drive system with improved current and speed-tracking performance. 相似文献
120.