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1.
The stress–strain state of rectangular plates with a variable thickness and constant weight is analyzed. The laws of variation in the thickness are specified to depend on parameters so that the plate weight remains constant for any of their values. To solve the problem, discrete Fourier series are used, which makes it possible to reduce a two-dimensional problem to one-dimensional. Calculation results are presented. 相似文献
2.
介绍了光码分多址系统中常用地址码(一维扩时码、二维码和三维码)的特点,并对它们各自的互相关均值和方差进行了理论分析。基于非相干光码分多址系统中光学相关接收机的基本原理,结合不同的用户地址码,对系统误码率性能进行了分析,得到了接收机最佳判决阈值与地址码基本特性参数和系统同时用户数间的关系。最后,给出了数值仿真结果。结果表明,对于采用特定地址码的光码分多址系统,只有选择合适的接收机判决阈值,系统的误码率性能才能达到最佳。研究结果对光码分多址系统中接收机判决阈值的选取具有一定的参考作用。 相似文献
3.
Let H and K be indefinite inner product spaces. This paper shows that a bijective map φ:B(H)→B(K) satisfies φ(AB B A) =φ(A)φ(5) φ(B) φ(A) for every pair A,B ∈B(H) if and only if either φ(A) = cU AU for all A or φ(A) = cUA U for all A; φsatisfies φ(AB A) = φ(A)φ(B) φ(A) for every pair A,B ∈B(H) if and only if either φ(A) = UAV for all A or φ(A) = UA V for all A, where A denotes the indefinite conjugate of A, U and V are bounded invertible linear or conjugate linear operators with U U = c-1I and V V = cI for some nonzero real number c. 相似文献
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5.
Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films 下载免费PDF全文
Helium-charged nanocrystalline titanium films have been deposited by HeAr magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60℃ to 350℃ while the other deposition'parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 20 angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening. 相似文献
6.
It is well known that potassium ion channels have higher permeability than K ions, and the permeable rate of a single K ion channel is about 108 ions per second. We develop a hierarchical model of potassium ion channel permeation involving ab initio quantum calculations and Brownian dynamics simulations, which can consistently explain a range of channel dynamics. The results show that the average velocity of K ions, the mean permeable time of K ions and the permeable rate of single channel are about 0.92nm/ns, 4.35ns and 2.30 ×10^8 ions/s, respectively. 相似文献
7.
The properties of high-energy ion beams (beamlets) observed in the boundary layer of the plasma sheet of the Earth’s magnetotail during short time intervals (1–2 min) have been considered. Beamlets are induced by nonlinear impulse accelerating processes occurring in the current sheet of the far regions of the geomagnetic tail. Then, moving toward the Earth along the magnetic field lines, they are detected in the magnetotail (in the plasma sheet boundary layer) and in the high-latitude part of the auroral zone in the form of short bursts of high-energy ions (with energies of several tens of keVs). The size of the localization region of the beamlets in the magnetotail and auroral zone has been determined by the epoch-superposition method, and it has been shown that beamlets are concentrated in a narrow region near the plasma sheet boundary, whose latitude size is no more than 0.8δ. This conclusion corroborates the theoretical prediction that the nonadiabatic resonant acceleration of ions occurs in a spatially localized region near the separatrix separating the open magnetic field lines and closed field lines, which contain the hot and isotropic plasmas of the plasma sheet. Based on the CLUSTER multisatellite measurements, the spatial structure of beamlets is analyzed and it has been found that the Alfvén wave arises due to the excitation of fire-hose instability at the instant of the exit of the ion beam from the current sheet to the high-latitude region of the far tail of the Earth’s magnetosphere. The longitudinal (along the magnetic field) and transverse sizes of a beamlet are estimated. It has been found that the beamlet is a dynamic plasma structure whose longitudinal size is several hundred times larger than its transverse size. 相似文献
8.
用A的不变子空间作参数,给出了算子方程AX=XAX的全部解。当A是单射或稠值域时,或者当A是正规算子时,给出了算子方程AX=XA=XAX的全部解。我们还给出正规算子X是算子方程AX=XZ=XAX的解的充分必要条件。 相似文献
9.
10.
本文研究了独立随机变量之和的绝对矩的几个性质, 其中包括$\ep|X+Y|-\ep|X-Y|$的表达式, 这里$X$和$Y$是相互独立的随机变量. 相似文献