POD方法在转子系统降维中的应用(英文)

将POD(Proper Orthogonal Decomposition)方法应用到转子动力系统中.建立一端松动的7个自由度非线性转子模型,考虑到混沌信号中包含各种不稳定的周期轨道,因此含有较多的系统信息,利用POD方法从混沌信号中获得一组POMs,并将原系统投影到该组POMs(Proper Orthogonal Modes)上,得到原系统4个自由度的近似等效模型,通过降维前后模型的定性性质比较,包括轴心轨迹、相图、分岔图等的比较可以看出降维后系统较好的保持了原系统的动力学特性,说明POD方法对于该模型降维是有效的.     

汞污染对水鳖的毒害影响

用不同浓度的Ｈｇ＾２＋溶液培育水鳖,研究Ｈｇ＾２＋对水鳖叶片中叶绿素含量、叶绿素ａ／ｂ值、ＳＯＤ、ＣＡＴ、ＰＯＤ活性以及可溶性蛋白含量的影响。随着Ｈｇ＾２＋浓度的增加,水鳖叶片中叶绿素含量、叶绿素ａ／ｂ值、ＣＡＴ活性逐渐减小,而ＳＯＤ、ＰＯＤ活性、可溶性蛋白含量则先升后降。研究表明,Ｈｇ＾２＋处理破坏了水鳖叶片中的抗氧化酶系,造成活性氧过量积累,最终导致植物死亡。     

茉莉酸对葡萄幼苗耐热性的影响

用50μmol/L茉莉酸（JA）处理葡萄幼苗,能减缓高温胁迫下一些胁变反应,如：可溶性蛋白含量的降低,电解质渗透率的增强.高温下,与未经JA处理的幼苗相比,JA处理能使幼苗保持较高抗氧酶活性,在一定程度上抑制了抗氧化酶活性的降低,并延缓了葡萄幼苗的热致死时间.     

2D Burgers equation with large Reynolds number using POD/DEIM and calibration

Model order reduction of the two‐dimensional Burgers equation is investigated. The mathematical formulation of POD/discrete empirical interpolation method (DEIM)‐reduced order model (ROM) is derived based on the Galerkin projection and DEIM from the existing high fidelity‐implicit finite‐difference full model. For validation, we numerically compared the POD ROM, POD/DEIM, and the full model in two cases of Re = 100 and Re = 1000, respectively. We found that the POD/DEIM ROM leads to a speed‐up of CPU time by a factor of O(10). The computational stability of POD/DEIM ROM is maintained by means of a careful selection of POD modes and the DEIM interpolation points. The solution of POD/DEIM in the case of Re = 1000 has an accuracy with error O(10^?3) versus O(10^?4) in the case of Re = 100 when compared with the high fidelity model. For this turbulent flow, a closure model consisting of a Tikhonov regularization is carried out in order to recover the missing information and is developed to account for the small‐scale dissipation effect of the truncated POD modes. It is shown that the computational results of this calibrated ROM exhibit considerable agreement with the high fidelity model, which implies the efficiency of the closure model used. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of variation in signal amplitude and transit time on reliability analysis of ultrasonic time of flight diffraction characterization of vertical and inclined cracks

The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted.     

Non‐intrusive reduced‐order modeling for multiphase porous media flows using Smolyak sparse grids

In this article, we describe a non‐intrusive reduction method for porous media multiphase flows using Smolyak sparse grids. This is the first attempt at applying such an non‐intrusive reduced‐order modelling (NIROM) based on Smolyak sparse grids to porous media multiphase flows. The advantage of this NIROM for porous media multiphase flows resides in that its non‐intrusiveness, which means it does not require modifications to the source code of full model. Another novelty is that it uses Smolyak sparse grids to construct a set of hypersurfaces representing the reduced‐porous media multiphase problem. This NIROM is implemented under the framework of an unstructured mesh control volume finite element multiphase model. Numerical examples show that the NIROM accuracy relative to the high‐fidelity model is maintained, whilst the computational cost is reduced by several orders of magnitude. Copyright © 2016 John Wiley & Sons, Ltd.     

黑臭河水治理与水生植物生理响应的灰色分析

以上海城区黑臭河水的生物-生态处理工艺为研究对象,采用灰色理论分析水生植物在黑臭河水治理过程中的生理响应顺序,为科学解释污染物净化机制提供依据.结果显示,植物的生理特性对COD和NH+4-N去除的优先级关联排序均为POD>CAT>Chla>SP>Chlb,表明反应体系对黑臭河水中COD和NH+4-N的去除主要是通过微生...     

Experimental study of the cavitation noise and vibration induced by the choked flow in a Venturi reactor

In this paper, the cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating flow in a Venturi reactor are investigated experimentally under different cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale cavitation flow structure, is applied to investigate the choked cavitating flow dynamics. The POD results show that two mechanisms, re-entrant jet flow mechanism and shock wave mechanism, govern the shedding and collapse of cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various cavitation regions induced by the choked cavitating flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for cavitation applications such as water treatment.     

过氧化物酶同工酶在南瓜分类中的应用

采用垂直平板聚丙烯酰胺凝胶电泳技术对南瓜属6个不同品种南瓜的过氧化物酶（POD）同工酶进行了分析研究，并采用聚类分析法对其亲缘关系进行比较，结果表明：6个不同品种南瓜根POD共分离出10条酶带，其中E2，E3，E4和E6分离清晰，活性较强，为6个品种所共有。     

稀土拮抗污水对小麦幼苗过氧化物同工酶的影响

利用聚丙烯酰胺凝胶垂直板电泳方法，研究了小麦种子采用不同浓度的Ce（ON）3处理前后，用污水处理厂处理前后污水浇灌下生长出的小麦幼苗叶的过氧化物酶（POD）酶谱的变化．结果表明，污水中的重金属离子胁迫能促进POD的表达，而稀土元素对重金属离子有拮抗作用，使小麦幼苗叶的POD同工酶酶带发生变化．