基于小波变换的血压信号特征提取方法研究

该文针对传统的人体血压信号特征提取方法的不足,提出了一种了基于小波变换的人体血压信号特征量提取方法。人体的血压信号是一种非平稳的低频信号,使用Marr小波对人体血压信号进行小波变换的时间一尺度分解,可以得到人体血压信号的模极大值曲线;通过选择合适的分解尺度,可以有效地滤除噪声,对人体血压数据进行消噪处理;进一步滤除奇异性极大值点,可以提取出动脉波动位置和动脉波动幅度信息。文中给出了算法的完整实现,并利用实际采集的人体血压数据验证了该算法,得到了波峰模极大值点和心脏跳动所发生的精确时刻,为人体血压信号的参数识别奠定了基础。     

悬索式跨越架用纤维绳索非线性本构关系试验研究

悬索式跨越架在跨越电力线路施工中应用广泛,其承载索及封网绳多采用超高分子量聚乙烯纤维绳索和聚酯纤维绳索.由于进行悬索式跨越架动力学仿真计算纤维绳索所涉及的非线性本构关系尚无公开资料,各单位在进行仿真计算时采用弹性模量固定值来替代非线性应力—应变关系曲线,导致计算结果与实际情况不符.针对上述问题,对这两种常用规格的纤维绳...     

材料力学性能与液压胀接性能的关系

应用弹塑性力学的基本原理分析了材料的力学性能与液压胀接性能的关系,根据应力-应变曲线分析了胀接原理,给出了可实现胀接的必要条件,为选择合理的管子和管板材料提供理论依据。     

含气率对缓冲液囊轴向刚度特性影响的研究

液体有效体积弹性模量是影响液压系统性能的一个重要物理参数。针对一种液囊缓冲装置,分析了不同液囊含气率对液体体积模量影响,结果显示在液囊压力不是太高的情况下(<10MPa),随着液囊压力的不断增大,液体有效体积模量也在不断增大;当含气率<0.10%时,含气率越高,相同压力下的有效体积模量越小;当液囊压力增大到一定值之后,有效体积模量逐渐趋于一个稳定值;且含气率越高,有效体积模量达到稳定值所需的压力越大;当含气率>0.10%时,含气率越高,有效体积模量随压力变化曲线的线性特性越明显;在相同液囊压力的情况下,含气率越高,有效体积模量越小。液囊含气率对缓冲液囊轴向刚度及压力变化特性影响的仿真结果显示,随着载荷的不断增大,不同含气率下的液囊轴向刚度不断增大,最后趋于一个稳定值;含气率越大,轴向刚度趋于稳定值所需载荷越大,且刚度曲线的非线性越明显。液囊压力与载荷曲线呈现出了良好的线性特性;当含气率<0.10%时,不同含气率下(包括纯液体)的液囊压力与载荷曲线基本重合;当含气率>0.10%时,随着含气率的增大,液囊压力与载荷曲线的曲率逐渐减小;不同曲线间的曲率差值总体较小。液囊的初始充压以及内壳轴向位移一定时,液囊受载存在对应的"临界载荷",载荷数值不受液体体积模量及液囊含气率的影响。     

循环荷载作用下岩石疲劳变形及特性试验研究

通过开展恒定加卸载速率,不同偏应力条件下的循环加卸载试验,研究了轴向应变、径向应变以及体积应该随循环次数的演化过程,得到了在不同偏应力条件下岩石的平均变形模量随循环次数与偏应力的变化关系,进而分析了循环荷载作用下岩石疲劳变形及特性。研究结果表明：（1）偏应力在50MPa之前,轴向应变、径向应变、体积应变以及变形模量随着循环次数的变化基本稳定,反之,表现出发散的趋势;（2）偏应力在80MPa作用下的平均变形模量较1IOMPa作用下的大,这是岩石内部裂隙增加和扩张的结果;（3）在不同偏应力条件下,平均变形模量随着偏应力的增大逐渐增大且趋于收敛。     

Laboratory investigation of boundary effect on pressure-settlement behavior of foundation soil with limited thickness involving geosynthetics

Plate loading tests were conducted to investigate the effect of a bottom boundary condition on the pressure-settlement behavior of a footing on sand with a limited thickness involving geosynthetics. Seven boundary materials including geosynthetics were used to create different boundary conditions at the bottom of the sand. Interface direct shear tests were conducted first to determine the interface friction angles between these boundary materials and sand, followed by plate loading tests to determine their pressure-settlement curves. Test results show that the sand with a limited thickness by a rigid bottom boundary had a higher bearing capacity than that with a larger thickness. The ultimate bearing capacity of the footing on the sand with a limited thickness generally increased with the increase of the interface friction angle. Geosynthetics provided better lateral restraint than other materials. An equation was developed to describe the relationship of the bearing capacity ratio of the sand with a limited thickness to that with a large thickness versus the soil thickness and the interface interaction coefficient. The effect of the boundary material on the back-calculated modulus of the sand was also evaluated.     

基于小波分析的传感器故障检测研究

针对航空发动机控制系统传感器故障检测在强噪声环境下易误报的问题,设计了基于模极大值原理的传感器故障检测方法.首先介绍基于小波奇异性进行故障检测的基本原理,之后根据信号和噪声奇异指数不同的特点判断噪声模极大值.对传感器典型故障,给出基于模极大值原理的传感器故障检测算法,并根据小波变换模极大值在不同尺度下的分布来完成故障的检测.通过某型涡扇发动机控制系统传感器故障检测仿真实验表明,小波变换能很好地刻画信号的奇异性特征,该滤波算法消噪效果明显,故障检测准确度高.     

Mechanical properties of roller compacted concrete containing rice husk ash with original and recycled asphalt pavement material

This study focused on the effects of rice husk ash (RHA) on the mechanical properties of roller compacted concrete (RCC) designed with original and reclaimed asphalt pavement (RAP) materials. The RCC mixes were produced by partial substitution of cement with RHA at varying amounts of 3% and 5%. Four aggregate combinations including the mix with original aggregate, coarse RAP + fine original aggregate, coarse original aggregate + fine RAP and total RAP were considered. The main experimental design consisted of the compressive strength and three points bending tests. Bending test was used to measure the modulus of rupture, material’s energy absorbency and analyse the fatigue response of RCC mixes. All tests were performed after 7, 28 and 120 days curing except the fatigue test that performed on 120 days specimens. Adding RHA resulted in higher optimum moisture content (OMC) and lower maximum dry density. Furthermore, adding RAP with different dimensions reduced the OMC and maximum dry density. The material’s flexibility improved upon replacing 3% cement by RHA. However, the energy absorbency reduced by increasing the RHA content to 5%. The fatigue life of RCC mixes containing RAP material was lower than the conventional one. Furthermore, replacing the coarse aggregate by RAP led to higher fatigue life than the fine aggregate. There was a strong relationship (R² > 0.90) between the energy absorbency and fatigue response of RCC mixes. At higher stress ratios of 0.72, the mix with higher energy absorbency behaved better under repeated loadings. Besides, a reverse relationship was found between the fatigue life and material porosity. Adding 3% RHA reduced the porosity especially after 120 days curing and improved the fatigue resistance. However, the addition of RHA to 5% resulted in higher porosities and lower fatigue lives.     

一种适用于浅海信道的盲均衡算法研究

针对多径衰落浅海水声信道，采用分数间隔判决反馈均衡器，提出了一种非线性结构的盲均衡算法。该算法不仅有效克服了水声通信中普遍存在的码间干扰效应，而且还进一步抑制了浅海信道引入的严重码内干扰现象，获得了更快的收敛速度和更小的剩余误差，提高了浅海水声通信的有效性和可靠性。仿真结果表明，该算法的性能优于通常的波特间隔均衡器，因而具有重要的工程应用价值。     

一种适用于水声信道盲均衡算法及仿真

对于高阶QAM信号,常数模算法的收敛误差不为零,而多模算法的收敛速度慢,提出了一种混合常数模算法,并将该算法应用于水声信道盲均衡。该算法根据均衡器输出信号模值与其判决模值之间的距离,设置一判决域。根据该判决域,算法的迭代过程在常数模和多模算法之间自动切换,且收敛后自动切换到多模算法。该算法收敛速度快,且均方误差小,特别适合高于高阶QAM信号的盲均衡,通过对水声信道均衡的计算机仿真,验证了该算法的优点及对多途干扰抑制的有效性。