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排序方式: 共有1597条查询结果,搜索用时 15 毫秒
1.
This paper addresses stability and l2‐gain for discrete‐time switched systems with unstable modes based on slow/fast mode‐dependent average dwell time (MDADT) switching strategies. Firstly, by employing a class of multiple discontinuous Lyapunov functions (MDLFs) and developing a kind of alternative switching signals, the sufficient conditions on stability are established for the system without external disturbances under a slow/fast MDADT switching scheme with a tighter bounds on the dwell time. Furthermore, by defining indicator functions and exploring the features of slow/fast MDADT switching, the weighted l2‐gain conditions are achieved for the system with external disturbances. Particularly, the criteria of stability and l2‐gain are also established for the corresponding discrete‐time switched linear systems with unstable modes via the MDLFs method and the slow/fast MDADT switching strategy. Finally, two numerical examples are presented to illustrate the advantages of the proposed methods.  相似文献   
2.
This article is concerned with the polynomial filtering problem for a class of nonlinear stochastic systems governed by the Itô differential equation. The system under investigation involves polynomial nonlinearities, unknown‐but‐bounded disturbances, and state‐ and disturbance‐dependent noises ((x,d)‐dependent noises for short). By expanding the polynomial nonlinear functions in Taylor series around the state estimate, a new polynomial filter design method is developed with hope to reduce the conservatism of the existing results. In virtue of stochastic analysis and inequality technique, sufficient conditions in terms of parameter‐dependent linear matrix inequalities (PDLMIs) are derived to guarantee that the estimation error system is input‐to‐state stable in probability. Moreover, the desired polynomial matrix can be obtained by solving the PDLMIs via the sum‐of‐squares approach. The effectiveness and applicability of the proposed method are illustrated by two numerical examples with one concerning the permanent magnet synchronous motor.  相似文献   
3.
In this article, a unified mode‐dependent average dwell time (MDADT) stability result is investigated, which could be applied to switched systems with an arbitrary combination of stable and unstable subsystems. Combined with MDADT analysis method, we classified subsystems into two categories: switching stable subsystems and switching unstable subsystems. State divergence caused by switching unstable subsystems could be compensated by activating switching stable subsystems for a sufficiently long time. Based on the above considerations, a new globally exponentially stability condition was proposed for discrete‐time switched linear systems. Under the premise of not resolving the LMIs, the MDADT boundary of the new stability condition is allowed to be readjusted according to the actual switching signal. Furthermore, the new stability result is a generalization of the previous one, which is more suitable for the case of more unstable subsystems. Some simulation results are given to show the advantages of the theoretic results obtained.  相似文献   
4.
Team members can request and provide backup from one to other members, which can help teams with high workload achieve dynamic workload optimization at the group level. However, studies on this issue are limited, especially on real‐world high‐risk operations. This study explored how to approach air traffic controllers make backup decisions in the dependent parallel approach operation. In this study, we focused on how individual difference factors can influence the controller's backup willingness and decision. Forty licensed controllers performed 32 simulated scenarios varied in their own task load, the backup recipients' task load, and shorter taxing possibility. We also measured their job satisfaction and work experience. Multilevel regression analyses showed that controllers with a higher level of job satisfaction were more likely to provide help to their colleagues. Moreover, when their job satisfaction was high, they were less sensitive to the seemingly inappropriate request, but they only used their additional resources to help others. The findings were discussed in the literature of teamwork and aviation safety.  相似文献   
5.
This paper investigates the problem of finite time stability of linear time‐varying system with delay. By constructing an augmented time‐varying Lyapunov functional and using the Wirtinger‐type inequality deductively, delay‐dependent finite time stability conditions are derived and presented in terms of differential linear matrix inequalities (DLMIs). Then, the DLMIs are transformed into a series of recursive linear matrix inequalities (RLMIs) by discretizing the time interval into equally spaced time distances, and an algorithm is given to solve the RLMIs. Examples illustrate the feasibility and effectiveness of the proposed method.  相似文献   
6.
In present paper, a new model is proposed and embedded into the finite element software ABAQUS to estimate the time dependent failure probability of the solid oxide fuel cell stack. The results show that sealant is the potential failure region of the solid oxide fuel cell stack, while the failure probability of the anode, electrolyte and cathode are very small within the operation time of 50,000 h. The creep and damage distribution of the components reflect that the proposed model can reasonably predict the time dependent failure probability of the solid oxide fuel cell stack. Increasing either the characteristic strain, Weibull modulus or decreasing the operating temperature can decrease the failure probability of the SOFC stack. For the sealant, to ensure the high temperature integrity of the SOFC stack, the characteristic strain should be larger than 0.01 or Weibull modulus should be higher than 8.0 under the operating temperature of 600 °C.  相似文献   
7.
李铁  李柯萱  皮希宇  方闯 《煤炭学报》2018,43(11):3115-3121
为探索开采速度对采空区顶板破断特征影响的力学机制,设定不同加载速率,开展砂岩3点弯曲和声发射试验,研究砂岩弯曲折断过程的力学行为及其受加载速度影响的时间效应和折断前兆特征。结果表明,加载速率越快,砂岩显著初始损伤声发射发生的应力条件越高,积累的应变能越高;岩石折断前,前兆声发射时间长度与加载速率呈指数负相关,加载速度越快,前兆声发射时间越短,可预测性越差;加载速率与砂岩折断声发射峰值能量及破坏载荷呈指数正相关,与砂岩折断声发射峰值计数呈指数负相关,加载速度越快,岩石折断所需的破坏荷载越大,峰值声发射计数越少,一次性释放的能量越高。上述岩石弯曲声发射特征值是加载速率的函数,存在时间效应。从机理上解释了煤矿开采速度越高,顶板岩体动力灾害危险性相对越高,可预测性越差的原因。  相似文献   
8.
Influence of the two different anion structures viz. bis(fluorosulfonyl)imide (FSI?) and bis(trifluoromethanesulfonyl) imide (TFSI?), on the thermophysical, dielectric and electrochemical properties of ZrO2-nanoparticle tethered pyrrolidinium based nanoscale hybrid ionic fluids (NHIFs) was investigated. Thermal and mechanical properties of NHIFs were found to depend strongly upon the structure of anions and TFSI? comprising NHIF showed better thermal and mechanical stability then its FSI? analogue. Temperature dependent electrical conductivity, dielectric and electrochemical properties of different NHIFs were studied. FSI-NHIF displayed higher ionic conductivity, associated with faster structural relaxation dynamics. At all the measured temperature, FSI-NHIF displayed superior electrochemical cycling performance than its TFSI-equivalent. While, electrochemical cell with TFSI-NHIF showed 81% capacitance retentivity after 5000 charge/discharge cycles, FSI-NHIF cell was found to retain >90% of its initial specific capacitance value after the same. Results obtained from the study optimize the applicability of pyrrolidinium based hybrid ionic fluids as electrolytes in secondary energy storage devices.  相似文献   
9.
We study the square‐root LASSO method for high‐dimensional sparse linear models with weakly dependent errors. The asymptotic and non‐asymptotic bounds for the estimation errors are derived. Our results cover a wide range of weakly dependent errors, including α‐mixing, ρ‐mixing, ?‐mixing, and mdependent types. Numerical simulations are conducted to show the consistency property of square‐root LASSO. An empirical application to financial data highlights the importance of the results and method.  相似文献   
10.
考虑区间变量的耦合性,基于多椭球模型提出了一种高效的耦合区间-随机混合可靠性分析方法。为解决耦合区间变量导致的可靠性分析计算效率低的问题,采用序列迭代分析方法,将混合可靠性分析的双层耦合循环分解为概率分析与区间分析,并结合多项式插值法提出了一种适用于极限状态函数关于耦合区间变量单调与非单调两种工况的高效区间分析算法。算例结果表明,所提的混合可靠性分析方法具有较好的计算精度与计算效率。  相似文献   
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