Global output‐feedback stabilization for a class of stochastic nonlinear systems via sampled‐data control

In this paper, the global sampled‐data output‐feedback stabilization problem is considered for a class of stochastic nonlinear systems. First, based on output‐feedback domination technique and emulation approach, a systematic design procedure for sampled‐data output‐feedback controller is proposed for a class of stochastic lower‐triangular nonlinear systems. It is proved that the proposed sampled‐data output‐feedback controller will stabilize the given stochastic nonlinear system in the sense of mean square exponential stability. Because of the domination nature of the proposed control approach, it is shown that the proposed control approach can also be used to handle the global sampled‐data output‐feedback stabilization problems for a more general class of stochastic non‐triangular nonlinear systems. Finally, simulation examples are given to demonstrate the effectiveness of the proposed method. Copyright © 2017 John Wiley & Sons, Ltd.     

Improved learning of I2C distance and accelerating the neighborhood search for image classification

Image-to-class (I2C) distance is a novel measure for image classification and has successfully handled datasets with large intra-class variances. However, due to the lack of a training phase, the performance of this distance is easily affected by irrelevant local features that may hurt the classification accuracy. Besides, the success of this I2C distance relies heavily on the large number of local features in the training set, which requires expensive computation cost for classifying test images. On the other hand, if there are small number of local features in the training set, it may result in poor performance.In this paper, we propose a distance learning method to improve the classification accuracy of this I2C distance as well as two strategies for accelerating its NN search. We first propose a large margin optimization framework to learn the I2C distance function, which is modeled as a weighted combination of the distance from every local feature in an image to its nearest-neighbor (NN) in a candidate class. We learn these weights associated with local features in the training set by constraining the optimization such that the I2C distance from image to its belonging class should be less than that to any other class. We evaluate the proposed method on several publicly available image datasets and show that the performance of I2C distance for classification can significantly be improved by learning a weighted I2C distance function. To improve the computation cost, we also propose two methods based on spatial division and hubness score to accelerate the NN search, which is able to largely reduce the on-line testing time while still preserving or even achieving a better classification accuracy.     

基于Euler-Bernoulli方程微悬臂梁弛豫分析

为探讨微机电系统中悬臂梁结构弛豫动力学特性,本文基于Euler-Bernoulli方程,计入空气滑膜阻尼对悬臂梁弛豫过程的影响,采用分离变量法导出悬臂梁挠度弛豫表达式;给出临界阻尼、过阻尼、欠阻尼梁挠度弛豫算例;利用ANSYS中瑞利阻尼模型对微悬臂梁临界阻尼、过阻尼、欠阻尼弛豫进行仿真,挠度弛豫过程在梁固定端附近与理论差异较大,仿真数据与理论偏差随挠度增加.     

分体空调冷凝水回收利用实验研究

针对分体空调冷凝水的浪费和无规律排放,回收冷凝水用于预冷冷凝器进风具有实际的节能潜力,笔者通过制作的一套冷凝水回收预冷装置,将该装置应用于某实验室单体空调,并进行了3种工况下的试验测试,分别为未装预冷装置、提供足够冷水预冷装置,以及空调器提供自身冷凝水预冷装置。计算和分析结果表明装有预冷装置前后,无论提供足够冷水还是自身产生的冷凝水,其性能系数COP分别提高了12.94%和9.52%。同时发现冷凝水产生量与需水量具有一定的差距,仅为需水量的56.26%。最后,结合试验现状和结果,对该预冷装置的应用和推广给出了相应的建议。     

某改建公路水泥路面板荷载应力与数值研究

利用ABAQUS对某改建公路的路面结构方案A和方案B进行研究,建立具有完整路面宽度的三维有限元模型,水泥路面接缝采用弹簧单元进行模拟,以便划分出不同大小尺寸的水泥混凝土板.然后载入标准轴载、超载20%、超载40%、超载60%时荷载,计算在均质稳定路基情况下水泥混凝土板的拉应力以及弯沉变化,分析A、B两个方案路面结构的优劣.     

应力吸收层结合料流变特性研究

应力吸收层的抗裂抗渗功能对其改性沥青结合料提出了更高的要求,但长期以来,国内外对应力吸收层结合料的研究相对较少,尤其是对其流变特性的研究,而改性沥青在不同温度下的流变性能与其实际的路用性能关系密切。选取两种应力吸收层改性沥青、两种普通改性沥青和一种基质沥青,根据SHRP规范推荐的试验方法,对比研究了5种沥青老化前后的高温、中温和低温流变性能。结果表明,应力吸收层结合料具有较好的抗老化性能,并具有良好的低温抗裂和中温抗疲劳性能。研究成果为应力吸收层的推广应用提供了试验依据。     

A state dependent sampling for linear state feedback

In this work, a new state-dependent sampling control enlarges the sampling intervals of state feedback control. We consider the case of linear time invariant systems and guarantee the exponential stability of the system origin for a chosen decay rate. The approach is based on LMIs obtained thanks to sufficient Lyapunov–Razumikhin stability conditions and follows two steps. In the first step, we compute a Lyapunov–Razumikhin function that guarantees exponential stability for all time-varying sampling intervals up to some given bound. This value can be used as a lower-bound of the state-dependent sampling function. In a second step, an off-line computation provides a mapping from the state-space into the set of sampling intervals: the state is divided into a finite number of regions, and to each of these regions is associated an allowable upper-bound of the sampling intervals that will guarantee the global (exponential or asymptotic) stability of the system. The results are based on sufficient conditions obtained using convex polytopes. Therefore, they involve some conservatism with respect to necessary and sufficient conditions. However, at each of the two steps, an optimization on the sampling upper-bounds is proposed. The approach is illustrated with numerical examples from the literature for which the number of actuations is shown to be reduced with respect to the periodic sampling case.     

惩戒解雇事由研究

《劳动合同法》第39条对惩戒解雇的规定在实际应用中出较多问题.理论上,如何合理界定归于雇员的原因,使用人单位的自由用工权与劳动者的劳动权达到平衡,是惩戒解雇事由需要重点解决的问题.我国应从劳动法的视角建构起用人单位惩戒解雇的法律规则,并完善相关的权利救济制度,使用人单位的自由用工权与劳动者的劳动权达到平衡.     

建筑电气与智能化专业的建筑消防与安防课程的研究与实践

本文探讨了建筑消防与安防课程的建设问题.在天津城市建设学院建筑类院校的背景下,在建筑电气与智能化的专业属性下,从教学内容的更新、教学体系的优化,以及教学方法的改革等不同方面,对该课程的建设进行了分析和研究.     

Effect of straw mixing amount on mechanical properties of admixture-adding hollow block

The bonding mechanism between straw and concrete was analyzed through testing the compressive strength and flexural strength of hollow block, with different straw amount and different dosage and types of admixtures. The test results show that the mechanical properties of hollow blocks reduced after adding straws, and the more straws was added, the more hollow block density decreased. But adding Al₂(SO₄)₃ and CaCl₂ could improve the dense degree between rice straw and concrete. And when the proportion of straw mixing amount was 10%, the flexural strength of the early strength agent (2% Al₂(SO₄)₃, CaCl₂) added hollow block reached as maximal as 3.1 MPa, while the compressive strength was 9.1 MPa, consisting with the strength grade of common concrete hollow block MU7.5.