Multi-scale modeling and simulation of crystallization during cooling in short fiber reinforced composites

To explore the crystallization during the cooling stage in short fiber reinforced composites, a multi-scale model in which macroscopic temperature and microscopic crystal morphology are related with each other is built up. According to this multi-scale model, the algorithm of coupling finite volume method with pixel coloring method is proposed. The finite volume method is used on the coarse grid to calculate the macroscopic temperature and the pixel coloring method is employed on the fine grid to capture the morphology of crystallization. Roles of cooling rate, initial temperature as well as the nucleation rate per unit fiber surface are investigated. To our knowledge this is the first time that a fully coupled multi-scale model and a multi-scale algorithm have been applied to the crystallization of short fiber reinforced composites.     

Design of NPR DFT-Modulated Filter Banks via Iterative Updating Algorithm

In this paper, an efficient algorithm is proposed to design nearly-perfect-reconstruction (NPR) DFT-modulated filter banks. First, the perfect-reconstruction (PR) condition of the oversampled DFT-modulated filter banks in the frequency domain is transformed into a set of quadratic equations with respect to the prototype filter (PF) in the time domain. Second, the design problem is formulated as an unconstrained optimization problem that involves PR condition and stopband energy of the PF. With the gradient vector of the objective function, an efficient iterative algorithm is presented to design the PF, which is updated with linear matrix equations at each iteration. The algorithm is identified as a modified Newton’s method, and its convergence is proved. Numerical examples and comparison with many other existing methods are included to demonstrate the effectiveness of the proposed method.     

石油贸易计价货币的国际政治经济博弈

石油贸易不是简单的商品贸易,它体现出更多的政治属性和金融属性,这也是世界大国在国际石油贸易计价货币上博弈的重要原因。美国在二战后,凭借经济实力的增长和布雷顿森林体系的建立,确立了"石油美元"的地位,并从中获得了大量好处。然而随着美元的持续贬值、"双赤字"问题以及"新特里芬悖论"等原因,"石油美元"体制日渐衰落。欧元、卢布、日元等欲成为新的石油贸易计价垄断货币。国际石油贸易的多元货币计价体制必将变为现实,其未来发展有几种可能,一是以多个大国货币作为计价基准,构建石油贸易的"多元混合货币"计价体制;二是以"国际石油货币"为基准;三是以特别提款权(SDR)作为计价基准。面对石油定价和交易货币的激烈争夺,中国应充分利用当前世界市场上大量的石油贸易盈余,既要创造有利于投资的金融和法律环境,又要避免给我国金融市场和国家经济安全造成负面影响。同时,应寻求建立自己的能源期货交易机构,以更有效地参与国际能源期货交易。     

Spectral derivative feature coding for hyperspectral signature analysis

This paper presents a new approach to hyperspectral signature analysis, called spectral derivative feature coding (SDFC). It is derived from texture features used in texture classification to dictate gradient changes among adjacent bands in characterizing spectral variations so as to improve better spectral discrimination and classification. In order to evaluate its performance, two known binary coding methods, spectral analysis manager (SPAM) and spectral feature-based binary coding (SFBC) are used to conduct comparative analysis. Experimental results demonstrate that the proposed SDFC performs more effectively in capturing spectral characteristics than do SPAM and SFBC.     

负反馈放大电路的方框图分析法中的基本放大电路的输入输出端口的选择

本文研究了负反馈放大电路的方框图分析法中的基本放大电路的输入输出端口的选择问题,给出了一个选择原则:若所选择的基本放大电路的输入输出端口不会导致放大电路的负反缋组态的改变,则这样的选择是合适的.反之则是不合适的。文中针对可能的4种组态的负反馈电路验证了这个选择原则.     

云南澜沧老厂银铅锌矿床成因研究

通过矿床地质特征、遥感图象解译、隐伏岩体预测、包体成分、成矿温度及稳定同位素等研究,认为老厂银铅锌矿床与金铜系列隐伏岩体有关,成矿时代为 50～86 Ma,成矿溶液以初始岩浆水为主,伴有雨水参与,成矿物质具多来源性,矿床属中温略偏高温的热液矿床。     

丙烯丙烷分离塔使用热泵节能的研究

精馏装置中使用热泵是节能的重要途径之一，本文以吉林化学工业公司某大型装置为对象，使用热泵作为节能手段，对过程进行了分析，根据具体情况采用开式节流闪蒸压缩的方式。优化结果表明普遍热力学效率可由原来的２０％提高至７０％；热泵的效能系数为５．７７；节能的经济效益达２００余万元／年。     

正交场摆动器自由电子激光器

本文给出了用正交场作为自由电子激光器摆动场的设想,并用流体动力学理论研究了使用正交场摆动器的自由电子激光器.文中通过理论分析论证了在所研究的系统中存在自由电子激光不稳定性,从而肯定了正交场可以用作摆动场的设想.     

考虑空间电荷梯度效应的静电电子回旋谐振脉塞的线性理论

本文给出了一个比较完整的关于静电电子回旋谐振脉塞的流体动力学线性理论,考虑了空间电荷梯度效应对静电电子回旋谐振脉塞不稳定性的影响.研究发现,空间电荷梯度效应主要对谐振点Ω=0附近的脉塞不稳定性产生影响.对 TE_(mn)工作模式,当 B_⊥较大时,空间电荷梯度效应对脉塞不稳定性的贡献将几乎与不考虑它存在时系统中的脉塞不稳定性相互抵消;当β_⊥较小时,空间电荷梯度效应成为系统中对脉塞不稳定性的主要贡献者.对于 TM_(mn)工作模式,研究发现,空间电荷梯度效应对系统中的脉塞不稳定性的贡献与不考虑它的存在时系统中的脉塞不稳定性,在β_″>k_″C/ω且 k_″>0时相互加强, 在β_″<β_″C/ω或β_″>k_″C/ω且 k_″<0时相互减弱.另外,在一定的工作参量条件下,空间电荷梯度效应也会成为系统中对 TM_(mn)模脉塞不稳定性的主要贡献者.最后,本文还发现,在考虑了空间电荷梯度效应后,如下的结论仍然成立:当电子注模Ω=0与冷波导模ω~2—k_″~2C~2—k_c~2C~2=0色散曲线相切时,只存在 TE_(mn)模脉塞不稳定性,而不存在 TM_(mn)模脉塞不稳定性.     

用z—80单板机控制图象信息采集和处理过程

本文介绍了一种用Z—80单板机控制测量电视系统的图象信息采集和处理过程的方法,阐述了设计思想并给出了系统工作流程图。