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81.
82.
A new chaotic genetic hybrid algorithm(CGHA) based on float point coding was put forward in this paper.Firstly,it used chaos optimization to search coarsely and produced a better initial population.Then,a power function carrier was adopted to improve the ergodicity and the sufficiency of the chaos optimization.Secondly,the genetic algorithm(GA) was used to search finely and guaranteed the population's evolution.To avoid the search being trapped in local minimum,a chaos degenerate mutation operator was desig... 相似文献
83.
电解质溶液中圆柱表面附近分布的电磁力可有效改变圆柱流体边界层,控制圆柱绕流。对剪切来流情形下圆柱绕流及其电磁控制进行了实验和计算研究。实验在转动水槽中进行,通过吊杆将装有电磁激活板的圆柱插在槽内液体中。吊杆上的应变片用于测试圆柱的阻力,注入适当的染料用来显示流场。数值模拟时,流场的基本方程为指数极坐标中考虑场力的Navier-Stokes方程,计算采用交替方向隐式格式和快速傅里叶变换格式。研究结果表明:剪切来流的绕流流场中,圆柱的尾涡向流速小的一侧偏移,升力和阻力周期性振荡,且升力的均值不为0,指向流速较小的一侧;电磁力作用后,圆柱的尾迹呈一条线向流速较小的一侧偏移,阻力减小且不再振荡,升力增大至稳定,指向流速较小的一侧。 相似文献
84.
30CrMnSiA绝热剪切带显微观察与分析 总被引:1,自引:0,他引:1
采用分离式霍普金森装置对30CrMnSiA的片式帽型试样进行动态剪切,利用光学显微、扫描电镜、透射电镜、显微硬度等金相分析方法对材料绝热剪切带的微观结构演化过程进行分析。研究发现,随着加载应变率的增大,剪切带发生由形变带到转变带的变化趋势,转变带呈"白亮"色,带内由尺寸约为50 nm的低位错、等轴晶粒组成,这是典型的再结晶晶粒特征。转变带形成过程可分为剪切变形、晶粒细化、晶粒断裂旋转、动态再结晶4个阶段。 相似文献
85.
文章通过计算机仿真,估算出理想条件下椭球体在2m / s直线运动时球体周围的剪强
及受激生物发光的流体体积,利用受激剪强初始值结论得出运动物体受激发光特性,并通过管流冲击物体实验证了仿真的结论。 相似文献
86.
A 10-MHz face shear (FS) square micromechanical resonator based on silicon-on-insulator (SOI) technology is presented in this paper. In order to examine the improvement of quality factor as well as motional resistance Rx in this structure, the center-stem anchor is employed in this study. The benefit of anchoring the square in the center, which is the nodal point, is that the energy losses through the anchor can be minimized. Hence, a quality factor value of 2.0 million and the motional resistance of 8.2 kΩ can be obtained with an FS mode resonator via finite element (FE) simulation. The results show the significance of the FS mode in this design, not only in its structure but also in its square-extensional mode and Lame-mode. Additionally, an SOI-based fabrication process is proposed to support the design. 相似文献
87.
The shear strength behavior and microstructural effects after aging for 100 h and 1,000 h at 150°C are reported for near-eutectic
Sn-Ag-Cu (SAC) solder joints (joining to Cu) made from Sn-3.5Ag (wt.%) and a set of SAC alloys (including Co- and Fe-modified
SAC alloys). All joints in the as-soldered and 100-h aged condition experienced shear failure in a ductile manner by either
uniform shear of the solder matrix (in the strongest solders) or by a more localized shear of the solder matrix adjacent to
the Cu6Sn5 interfacial layer, consistent with other observations. After 1,000 h of aging, a level of embrittlement of the Cu3Sn/Cu interface can be detected in some solder joints made with all of the SAC alloys and with Sn-3.5Ag, which can lead to
partial debonding during shear testing. However, only ductile failure was observed in all solder joints made from the Co-
and Fe-modified SAC alloys after aging for 1,000 h. Thus, the strategy of modifying a strong (high Cu content) SAC solder
alloy with a substitutional alloy addition for Cu seems to be effective for producing a solder joint that retains both strength
and ductility for extended isothermal aging at high temperatures. 相似文献
88.
89.
90.
Taewon SeoSchool of Mechanical Eng. Andong National Univ. South KoreaWang Xing-kui Wang Guang-qianDepartment of Hydraulic Eng. Tsinghua Univ. Beijing P.R.China 《水动力学研究与进展(B辑)》1998,(3)
This study condiders spatially developing free shear layers at moderateReynolds numbers that are formed by the merging of two free streams initially separatedby a splitter plate.To study the nonlinear interactions between the two-and three-dimen-sional fundamental and subharmonic modes in the spatially developing shear layer,the se-lected five modes represent the minimum number that needs to be considered.The objec-tive of this study is to investigate the nonlinear effects arising from the interactions be-tween two-and three-dimensional large-scale coherent structures in a free shear layer.Our attention is focused on the energy exchange mechanisms between the various modes,and the effects of the nonlinear evolution of the phases of the interacting modes.It isshown that depending on the initial modal phase angles the downstream growth of theshear layer and the associated local entrainment can be strongly affected by the presence ofthese nonlinear interactions.This high sensitivity of the shear layer growt 相似文献