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1.
基于分形盒维数和多重分形的爆破地震波信号分析   总被引:5,自引:3,他引:5  
为深入研究爆破地震波特性,采用分形盒维数和多重分形理论相结合的数学方法,通过其算法的理论推导和MATLAB软件编程计算得到地震波信号的盒维数值和多重分形谱图,对地震波信号的分形特征进行了分析。研究表明:盒维数D值的大小反映了地震波曲线的复杂程度和频率结构特征,说明盒维数只是对地震波信号整体性的描述;多重分形能够更加精细地描述地震波信号的局部特征,其谱图描述了不同奇异性指数α的概率信息。因此提出使用分形盒维数和多重分形相结合的信号分析方法,获取爆破地震波信号的整体强弱、频谱结构特征和局部的奇异性等重要信息。  相似文献   

2.
国内外纳米科技研究应用现状及发展趋势分析   总被引:9,自引:0,他引:9  
介绍了国内外纳米材料及其技术在电子工业、环保工业、建材工业、金属工业、文物保护、医学等领域的开发应用现状 ,并对纳米科技未来的发展趋势和市场前景进行了预测和展望  相似文献   

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通过分析近场声全息中传播波和倏逝波的声场分布与声源大小、辐射频率及测量距离的关系,得出了传播波和倏逝波在空间声场中的变化规律、影响因素以及两者之间的对应关系,确定了可利用的倏逝波传播距离。在此基础上,提出了一种改进的远场声全息方法:首先利用传统远场声全息方法重建声源,然后通过传播波与倏逝波的关系,得出声源面上相应的倏逝波成分,两者叠加获取接近于近场声全息的重建结果。最后,通过仿真和实验验证了这一结果。  相似文献   

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太阳电池用多晶硅及其吸杂研究现状   总被引:3,自引:0,他引:3  
综述了几类主要的太阳电池用多晶硅及其吸杂研究现状.评述了当前太阳电池领域涉及到的几类多晶硅如铸造多晶硅、冶金法多晶硅、西门子法多晶硅等的优缺点.详细描述了多晶硅的吸杂类型、吸杂过程、吸杂影响因素等.给出了本课题组关于冶金法多晶硅吸杂实验的一些初步研究结果.展望了多晶硅及其吸杂技术的发展.  相似文献   

7.
叶轮机械弯扭叶片的研究现状及发展趋势   总被引:42,自引:1,他引:42  
弯扭叶片在20世纪90年代已在英、美等发达国家较普遍地得到应用,在我国也成功地应用于蒸汽轮机,在航空发动机涡轮中的应用也有了良好的开端。文章就叶片弯曲降低能量损失的机理以及静态和动态实验对采用弯曲叶片的效果做了综合评述,对压气机采用弯曲叶片的科研进展,以及遇到的难点也作了概要的介绍。根据我们的设计经验,在文章的最后总结了弯曲叶片级设计时应遵循的几条原则。  相似文献   

8.
新型功能梯度材料研究现状及发展方向   总被引:10,自引:0,他引:10  
介绍了功能梯度材料的研究现状及发展方向,针对功能梯度材料研究的核心问题——材料合成技术,综述了低温制备工艺研究现状,最后对功能梯度材料进行了展望。  相似文献   

9.
The current decomposition methods are not suitable for electromechanical product; the smallest decomposition units obtained by these methods are static parts or components, which cannot reflect the characteristics of electromechanical product that ‘action determines motion, and motion determines function'. Meta-action is the smallest action to realize the function of electromechanical product, and it is reasonable to regard meta-action as the smallest decomposition unit of electromechanical product. Meta-action unit is the smallest structural unit to ensure the normal operation of meta-action, and it is also the smallest carrier of electromechanical product quality characteristics. Meta-action unit modeling technology is the basis of other subsequent research, so it is necessary to study it. In this paper, detailed criteria for meta-action decomposition and meta-action unit separation are formulated, and the standardized structural model, symbolized conceptual model, and assembly model of meta-action unit are also studied, which provide a basis for mechanical, kinematic, and failure mechanism research of electromechanical product. A CNC (computer numerical control) machine tool made in China is taken as an example for meta-motion decomposition and meta-action unit modeling, and the results verify the applicability and correctness of the method proposed in this paper. The proposed method is also applicable to other types of electromechanical product.  相似文献   

10.
基于射线理论的海底混响建模研究   总被引:2,自引:1,他引:2       下载免费PDF全文
以海底混响为研究对象,在深入剖析混响形成机理的基础上,以射线理论作为研究方法,从网络模型的角度出发,建立起一种具有直观物理意义的海底混响模型。结合“互易性”提出了收发合置情况下的非相干海底混响信号模型,进一步简化后用于混响信号的预报以及混响平均强度的计算。仿真结果显示了该方法的有效性。  相似文献   

11.
Diffusion is often used as the model for real diffusion phenomena, as well as the used approach for non‐diffusive phenomena, the latter due to its relative simplicity, to the existence of many mathematical tools to solve the resulting differential equations, and to its robustness if a numerical solution is to be obtained. When searching for the solution of a practical problem, the involved phenomena and processes are usually complex or/and the real phenomena is other than diffusion, and some comments need to be addressed if a diffusive model is adopted. This work concerns mainly on the author’s experience on the transport phenomena field (fluid dynamics and heat and mass transfer), including the numerical simulation of systems and processes, where the diffusive model is often used even to model non‐diffusive phenomena. It is thus a report of some ill‐answered questions that the author has experienced, related with the use of the diffusion model. Different ill‐answered questions, related with the diffusion modeling, in different fields or problems, could be equally founded.  相似文献   

12.
Macroscopic traffic crash analyses have been conducted to incorporate traffic safety into long-term transportation planning. This study aims at developing a multivariate Poisson lognormal conditional autoregressive model at the macroscopic level for crashes by different transportation modes such as motor vehicle, bicycle, and pedestrian crashes. Many previous studies have shown the presence of common unobserved factors across different crash types. Thus, it was expected that adopting multivariate model structure would show a better modeling performance since it can capture shared unobserved features across various types. The multivariate model and univariate model were estimated based on traffic analysis zones (TAZs) and compared. It was found that the multivariate model significantly outperforms the univariate model. It is expected that the findings from this study can contribute to more reliable traffic crash modeling, especially when focusing on different modes. Also, variables that are found significant for each mode can be used to guide traffic safety policy decision makers to allocate resources more efficiently for the zones with higher risk of a particular transportation mode.  相似文献   

13.
A RAM (reliability, availability and maintenance) model has been built for the GE Industrial, Plastics Lexan® plant in Bergen op Zoom, The Netherlands. It was based on a Reliability Block Diagram with a Monte Carlo simulation engine. The model has been validated against actual plant data from two different sources, and against local expert opinions, resulting in a satisfactory simulation model. The model was used to assess two key decisions that were (to be) made by GE Industrial, Plastics concerning operation and shutdown policies of the plant. The model results showed that the operation and maintenance could be further improved, and that in doing so the annual production loss could be reduced further.  相似文献   

14.
粉状纳米材料的表面研究进展与展望   总被引:11,自引:2,他引:9  
吴润  谢长生 《材料导报》2000,14(10):43-46
粉状纳米材料表面是决定其性能的关键性因素之一。用热物理法,化学法和机械制造法都可制得纳米粉,但其表面却有所不同。热物理法能得到表面比较纯净的纳米粉。纳米粉表面与其成分、结构和形态有关,它对纳米粉的化学和物理性能有着决定性的影响。因此,粉状纳粉材料应用前景也决取于其表面研究的进展。  相似文献   

15.
Results on theoretical and experimental studies on Cs beam optics using quadrupole and hexapole magnets and a combination of both, are reported. The efficiency of the deflection system and the velocity distribution in the beam have been computed for extended beam sources and compared with experimental results. An appropriate combination of magnets yielded a strong beam with a narrow relative half-width velocity range of about 7 percent. Design problems of Cs standards are discussed. A new wedge-shaped analyzer flop-in magnet is under study. Frequency shifting effects due to Majorana transitions are reported and the frequency shifting mechanism is discussed.  相似文献   

16.
刘衍  钟胜 《工业工程》2014,17(4):116-122
针对我国大型综合医院人满为患,高峰时段患者就诊通道忙闲不均,存在安全隐患的问题,本文开发了患者就诊路径调度0-1规划模型,以平衡各种通道资源的利用。以四川大学华西医院为例进行了实证分析,验证了该模型的有效性和应用价值。  相似文献   

17.
The products of ecological textile have represented nowadays the new trend of global consumption and production of textile while become an important means for some countries to utilize "green barrier" as a limitation of import of textile products. Following the entrance of China into the WTO, the position of "green barrier "becomes significantly important in the trade of textile products. As China is a big country of textile production,speeding up the research on standards for products of ecological textile, countering the latest situation appearing in international trade of textile, to take as quickly as possible responsive measures is a very urgent problem in port, to enhancing the ability of international market competition and to promoting the stable development of foreign oriented economy.  相似文献   

18.
在诸如风致飞射物撞击等刚体冲击作用下,建筑夹层玻璃因自身脆性特征极易破坏。针对这个问题提出了在刚体冲击下夹层玻璃破坏状态的预测方法,综合考虑了玻璃构型、中间胶层、支撑条件及尺寸等多种设计参数。首先针对多类夹层玻璃进行往复刚体冲击试验,建立567组PVB及210组SGP的两种不同中间胶层的夹层玻璃试验数据库;随后基于鲸鱼优化下的核极限学习机(WOA-KELM)机器学习算法,建立夹层玻璃破坏状态的预测模型,并与支持向量机(Support Vector Machine, SVM)及最小二乘支持向量机(Least Squares Support Vector Machine, LSSVM)建立的相应预测模型进行对比分析。结果表明, WOA-KELM模型破坏状态预测精度达88.45%,能较好地预测夹层玻璃的破坏,满足工程应用的需求,且预测模型精度及实时性均优于其他模型。  相似文献   

19.
Goray LI  Seely JF 《Applied optics》2002,41(7):1434-1445
The near-normal-incidence efficiencies of a 2400-groove/mm holographic master grating, a replica grating, and a multilayer grating are modeled in the soft-x-ray-extreme-ultraviolet (EUV) regions and are compared with efficiencies that are measured with synchrotron radiation. The efficiencies are calculated by the computer program PCGrate, which is based on a rigorous modified integral method. The theory of our integral method is described both for monolayer and multilayer gratings designated for the soft-x-ray-EUV-wavelength range. The calculations account for the groove profile as determined from atomic force microscopy with a depth scaling in the case of the multilayer grating and an average random microroughness (0.7 nm) for the short wavelengths. The refractive indices of the grating substrate and coatings have been taken from different sources because of the wide range of the wavelengths (4.5-50 nm). The measured peak absolute efficiency of 10.4% in the second diffraction order at a wavelength of 11.4 nm is achieved for the multilayer grating and is in good agreement with a computed value of approximately 11.5%. Rigorous modeling of the efficiencies of three similar gratings is in good overall agreement with the measured efficiency over a wide wavelength region. Additional calculations have indicated that relatively high normal incidence efficiency (of at least several percent) and large angular dispersion in the higher orders can be achieved in the 4.5-10.5-nm range by application of various multilayer coatings.  相似文献   

20.
叶片的联合弯扭气动成型概念是王仲奇教授和前苏联的费里鲍夫 (Г .А .Филиппов)于 6 0年代初提出的。叶片沿高度的周向弯曲 ,增加了叶轮机械气动设计的自由度。理论分析和试验研究表明 ,应用了这一概念而设计出的“正弯”涡轮导叶 ,可以形成两端高、中部低的沿叶高静压分布 ,从而将两端端壁低能的边界层流体吸入叶片中部而降低能量损失。这种“正弯”涡轮导叶还可以使叶片两端压力面和吸力面之间的压差减小 ,从而降低与此有关的二次流损失。利用这个设计自由度 ,可以有效控制叶根反动度 ,从而消除动叶根部分离 ,改善整个涡轮的流…  相似文献   

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