平端板连接组合节点性能研究

本主要分析了平端板连接组合节点在对称弯矩作用下的工作性能。对平端板连接组合节点用ANSYS进行了三维有限元分析，并用试验结果进行了验证。利用有限元分析程序．进行了一系列的参数分析，探讨了平端板连接组合节点在单调荷栽作用下的工作性能及其影响因素。     

Reliability sensitivity analysis based on multi-hyperplane combination method

For a nonlinear limit state function, the first-order reliability method （FORM） may cause large errors in the computation of not only the reliability index or failure probability but also the reliability sensitivity. In order to obtain more the accurate results of the reliability sensitivity analysis, a number of hyperplanes are built near the design point by first-order Tayler series expansion, which replace the known nonlinear limit state hypersurface, and an equivalent computational method is utilized to construct an equivalent hyperplane of the obtained hyperplanes. And the reliability sensitivities can be estimated more accurately by the derived equations based on the equivalent hyperplane. An example shows that the method is effective and feasible.     

Controllability and observability covariance matrices for the analysis and order reduction of stable nonlinear systems

This paper presents a framework for nonlinear systems analysis that is based upon controllability and observability covariance matrices. These matrices are introduced in the paper and it is shown that gramians for linear systems form special cases of the covariance matrices. The covariance matrices can be transformed via a balancing-like transformation and nonlinearity measures are defined based upon these transformed covariance matrices. Subsequently, the covariance matrices are used for reduction of the nonlinear model. It is shown that the model reduction procedure reduces to balanced model truncation for linear systems for impulse inputs. Furthermore, it is also shown that several model reduction procedures that were developed by other researchers, and assumed to be independent from one another, are related. The findings are illustrated with an example.     

球面磨床专用夹具非线性接触夹紧性能分析

运用ANSYS Workbench对球面磨床的专用夹具部件进行多工况的非线性接触分析,研究夹具各个零件之间的接触状态,分析夹具整体结构和球体的变形量、极限应力、扭转角度以及结合面之间滑移量,确定夹紧螺栓预紧力,校核夹紧机构的可靠性。此方法为球面磨床专用夹具的设计与校核提供参考。     

汽车悬架弹簧多级减振刚度的应用性能分析

介绍了汽车非线性减振悬架的性能特点.根据非线性悬架特点设计了一种四级减振刚度弹簧;根据非线性曲线的特点,把汽车的不同工况分解为四减振区域,并分别把每一个减振区域匹配出不同刚度的线性弹性刚度,相当于用一次曲线去逼近空气弹簧的多次刚度曲线,这样就能得到吸振能力非常接近空气弹簧的弹性特性.进一步计算了四级减振刚度悬架汽车的减振频率、静挠度、振幅、阻尼特性.计算结果表明,四级减振刚度悬架比单刚度悬架舒适性能有很大的提高.     

Linearization technique using bipolar transistor at 5 GHz low noise amplifier

A CMOS low noise amplifier (LNA) used in wireless communication systems, such as WLAN and CDMA, must have low noise figure, high linearity, and sufficient gain. Several techniques have been proposed to improve the linearity of CMOS LNA circuits. The proposed low noise amplifier achieves high third-order input intercept point (IIP3) using multi-gated configuration technique, by using two transistors, the first is the main CMOS transistor, and the second is bipolar transistor in TSMC 0.18 m technology. Bipolar transistor is used to cancel the third-order component from MOS transistor to fulfill high linearity operation. This work is designed and fabricated in TSMC 0.18 m CMOS process. At 5 GHz, the proposed LNA achieves a measurement results as 16 dBm of IIP3, 10.5 dB of gain, 2.1 dB of noise figure, and 8 mW of power consumption.     

气动比例系统的智能混合控制

针对气动比例系统的非线性特征,将神经网络模糊控制引入到专家控制中,与专家系统相结合形成一种综合的实时智能混合控制系统,该控制系统既具有专家控制的逻辑推理、理性、抽象智能行为,又具有神经模糊控制的直觉推理、感性、形象智能行为,这两者结合采取并行控制与知识共享的策略,既能满足系统的快速性和灵活性,又能保证系统的运行平稳性。将设计的智能混合控制器引入到系统模型当中,通过与其他不同控制策略对阶跃信号的系统仿真进行比较,证明该控制系统跟踪性能强,响应速度快,兼顾快速性和灵活性,系统运行平稳,反映出良好的静态和动态特性。通过试验验证针对该气动比例系统的非线性特征设计的智能混合控制策略是正确和有效的。     

Nonlinear optical properties of two oxazine dyes in aqueous solution and polyacrylamide hydrogel using single beam Z-scan

The nonlinear optical properties of the two oxazine dyes, i.e. oxazine 720 (OX720) and oxazine 750 (OX750), in aqueous solution and in polyacrylamide hydrogel (PAA) matrix were studied by Z-scan technique using CW He–Ne laser at 632.8 nm. All the polymeric and aqueous samples showed a negative nonlinearity and large nonlinear refractive index of the order of 10⁻⁸ cm²/W. The concentration-dependent nonlinear refractive index was also investigated. In the case of PAA–dye systems, two types of transit (fast) and steady state (slow) nonlinear effects were observed. It is believed that these effects are due to the thermo-optical induced refractive index gradient and a concentration gradient induced by a temperature gradient present in a medium.     

A re-examination of stationarity of energy consumption: Evidence from new unit root tests

In this paper, we re-examine the stochastic behaviour of per capita total primary energy consumption across 178 countries around the world. For this purpose, in addition to conventional unit root tests, we apply newly developed tests that allow for nonlinear adjustments and structural breaks in the data generating process. The results of the unit root tests show that allowing for structural breaks and nonlinearity result in more frequent rejection of the null hypothesis of unit root, suggesting that most of the series under consideration follow a stationary process. These findings imply that both energy economists and policy makers must be careful and take account of possible nonlinearities and structural breaks in their analyses of energy consumption. In addition, the results imply that government interventions into the energy markets in most countries have no effect in the long run, although the short-run effects of the interventions depend on the size and the direction of interventions.     

高非线性度布尔函数的构造

布尔函数的非线性度是衡量及其密码学意义的重要标志,而非线性度和其它密码学强度指标,如代数次数,扩散性,相关免疫性等存在着制约关系,本文研究了高非线性度布尔函数的构造,讨论非线性度和其它密码学准则之间的折关系,给出高非线性度,高代数次数,高非线性平衡相关免疫以及具有较好扩散性的高非线性度布尔函数的几种构造方法。