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471.
《European Journal of Mechanics - B/Fluids》2000,19(5):547-557
An account is given of the working life of the recently decommissioned axisymmetric turbulent-boundary-layer windtunnel in the Hermann-Föttinger-Institut of the Technische Universität Berlin, and some principal investigations conducted in it. 相似文献
472.
《International Journal of Solids and Structures》1999,36(23):3517-3539
Thermal residual-stresses introduced during manufacture and their effect on the natural frequencies and vibration modes of stringer stiffened composite plates is investigated. The principal idea in the work is to include stiffeners on the perimeter of a composite plate in which the laminate design of the stiffeners and plate are different. Such an arrangement yields manufacturing induced thermal residual-stresses; these stresses result from the difference in manufacturing and operating temperatures as well as the difference in thermal expansion coefficients and elastic properties of the plate and the stiffeners. The analysis is based on an enhanced Reissner–Mindlin plate theory and involves two separate calculations. In the first, the thermal residual-stress state is determined for an unconstrained plate. In the second, the free vibration problem is solved; thermal effects from the first calculation are included by way of nonlinear membrane-bending coupling which in turn defines the free vibration reference state. The problem is solved using a 16-node bi-cubic Lagrange element in a finite element formulation. Three different plate-stiffener geometries are used to illustrate the effects of stringer size, stringer placement and temperature difference. Two principal results are obtained: first, it is shown that thermal residual-stresses can have a significant effect on the natural frequencies; secondly, thermal residual-stresses can be tailored to increase natural frequencies. Therefore it is concluded that an evaluation of these stresses and a judicious analysis of their effects must be included in the design of this class of composite structures. 相似文献
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475.
基于概率假设密度滤波平滑器的检测前跟踪算法 总被引:1,自引:0,他引:1
基于概率假设密度滤波(PHD)的检测前跟踪(TBD)技术可以有效解决未知弱小多目标检测问题。PHD-TBD算法粒子权重计算受量测噪声影响明显,导致目标数估计存在起伏现象,制约了PHD-TBD算法性能。对PHD-TBD技术进行研究,引进概率假设密度滤波平滑器,提出基于平滑的PHD-TBD算法。该算法对当前帧目标数估计时,综合利用前向递推和后向平滑结果对粒子权重进行更新,在一定程度上克服了随机量测噪声的影响。通过仿真验证,该算法能够有效发现目标,准确估计目标数目和位置,性能有较大提高。 相似文献
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《Radiation Physics and Chemistry》2007,76(3):542-545
A four-body classical trajectory Monte Carlo (CTMC) method is applied in the study of single and double ionization cross-sections of the silicon K-shell. The calculations are based on the independent particle model. As projectiles, we consider protons with energies between 0.25 and 4.5 MeV. Our CTMC results are compared with the existing theoretical and experimental data. 相似文献
479.
Silicon carbide nanotubes (SiCNTs) were prepared by chemical vapor deposition (CVD). Methyltrichlorosilane (MTS) was selected as the SiC gaseous source and, ferrocence and thiophene as the catalyst and the cocatalyst, respectively. The influences of pyrolysis temperature, the content of catalyst and the cocatalyst, and the mole ratio between H2 and MTS, on the shape of the pyrolysis products were investigated, respectively. The products were characterized by SEM, EDX, XRD and HRTEM, respectively. Novel type of multi-walled SiCNTs, with 30~80 nm and 15~20 nm outer and inner diameters, respectively, were observed. 相似文献
480.
《Nonlinear Analysis: Theory, Methods & Applications》2005,60(7):1331-1350
In this paper, we investigate a system of delayed lattice differential equations with partial monotonicity. By using Schauder's fixed point theorem, a new cross-iteration scheme is given to establish the existence of traveling wave solutions. Our main results can deal with the existence of traveling wave solution for a class of delayed reaction diffusion system with partial monotonicity and generalize the results of Wu and Zou (J. Differential Equations 135 (1997) 315–357). 相似文献