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81.
We investigate the simple modules for the sporadic simple Mathieu groups M22, M23 and M24 as well as those of the automorphism group, the covering groups and the bicyclic extensions of M22 in characteristics 2 and 3. We determine the vertices and sources as well as the Green correspondents of these simple modules. We also find two 3-blocks with elementary abelian defect groups of order 9 in these groups which are Morita equivalent to their Brauer correspondents. 相似文献
82.
83.
PM2.5 in an industrial district of Zhengzhou,China:Chemical composition and source apportionment 总被引:3,自引:0,他引:3
Zhengzhou is a developing city in China,that is heavily polluted by high levels of particulate matter.In this study.fine particulate matter(PM2.5) was collected and analyzed for their chemical composition(soluble ions,elements,elemental carbon(EC) and organic carbon(OC)) in an industrial district of Zhengzhou in 2010.The average concentrations of PM2.5 were 181,122,186 and 211μg/m3 for spring,summer, autumn and winter,respectively,with an annual average of 175μg/m3,far exceeding the PM2.5 regulation of USA National Air Quality Standards(15μg/m3).The dominant components of PM2.5 in Zhengzhou were secondary ions(sulphate and nitrate) and carbon fractions.Soluble ions,total carbon and elements contributed 41%,13%and 3%of PM2.5 mass,respectively.Soil dust,secondary aerosol and coal combustion, each contributing about 26%,24%and 23%of total PM2.5 mass,were the major sources of PM2.5,according to the result of positive matrix factorization analysis.A mixed source of biomass burning,oil combustion and incineration contributed 13%of PM2.5.Fine particulate matter arising from vehicles and industry contributed about 10%and 4%of PM2.5,respectively. 相似文献
84.
In order to identify the day and night pollution sources of PM10 in ambient air in Longyan City,the authors analyzed the elemental composition of respirable particulate matters in the day and night amb... 相似文献
85.
FLUTTER INSTABILITY OF SUPPORTED PIPES CONVEYING FLUID SUBJECTED TO DISTRIBUTED FOLLOWER FORCES 总被引:1,自引:0,他引:1
Lin Wang 《Acta Mechanica Solida Sinica》2012,25(1):46-52
In the past decades,it has been reported that divergence is the expected form of instability for fluid-conveying pipes with both ends supported.In this paper,the form of instability of supported pipes ... 相似文献
86.
87.
The modified discrete KP equation is the Bäcklund transformation for the Hirota’s discrete KP equation or the Hirota-Miwa equation. We construct the modified discrete KP equation with self-consistent sources via source generation procedure and clarify the algebraic structure of the resulting coupled modified discrete KP system by presenting its discrete Gram-type determinant solutions. It is also shown that the commutativity between the source generation procedure and Bäcklund transformation is valid for the discrete KP equation. Finally, we demonstrate that the modified discrete KP equation with self-consistent sources yields the modified differential-difference KP equation with self-consistent sources through a continuum limit. The continuum limit of an explicit solution to the modified discrete KP equation with self-consistent sources also gives the explicit solution for the modified differential-difference KP equation with self-consistent sources. 相似文献
88.
The concept of asynchronous oscillatory response of mechanical systems in free vibrations is addressed as an introduction to a definition of asynchronous modes of vibration. Connection of the asynchronous modes with the localization and other dynamical phenomena is discussed. Then, conditions for the occurrence of asynchronous modes are investigated in depth. It is seen that a non-conservative system, with an asymmetric stiffness matrix – caused, for instance, by circulatory loads, may have an asynchronous mode. Yet, it is also seen that non-conservativeness is not actually mandatory. Two- to four-degree-of-freedom models of a column with a follower force are addressed, allowing for a mathematical modelling and phenomenological discussion. 相似文献
89.
《Wave Motion》2016
Nonlinear Rayleigh wave fields generated by an angle beam wedge transducer are modeled in this study. The calculated area sound sources underneath the wedge are used to model the fundamental Rayleigh sound fields on the specimen surface, which are more accurate than the previously used line sources with uniform or Gaussian amplitude distributions. A general two-dimensional nonlinear Rayleigh wave equation without parabolic approximation is introduced and the solutions are obtained using the quasilinear theory. The second harmonic Rayleigh wave due to material nonlinearity is given in an integral expression with these fundamental Rayleigh waves radiated by the wedge transmitter acting as a forcing function. Multi-Gaussian beam (MGB) models are employed to simplify these integral solutions and to extract the diffraction and attenuation correction terms explicitly. The effect of nonlinearity of generating sources on the second harmonic Rayleigh wave fields is taken into consideration; simulation results show that it will affect the magnitude and diffraction correction of the second harmonic waves in the region close to the Rayleigh wave sound sources. This research provides a theoretical improvement to alleviate the experimental restriction on analyzing the effects of diffraction, attenuation and source nonlinearity when using angle beam wedge transducers as transmitters. 相似文献
90.
设计并实现了一种基于Gm-C二次节(Biquad)结构的6阶切比雪夫Ⅰ型模拟中频带通滤波器,中心频率为46MHz,带宽为2.046MHz.其中Biquad结构中加入了负阻抗单元,增加输出阻抗,实现滤波器的高Q值(品质因数).跨导放大器(Operational transconductance amplifier,OTA)单元使用源极负反馈技术,优化了OTA的线性性能.整个滤波器电路采用0.35μm CMOS工艺实现.经过仿真验证,滤波器的通带纹波是2.704dB,1.5倍带宽处衰减大于21dB.在3.3V电源电压情况下,滤波器的总电流消耗为8.87mA. 相似文献