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81.
根据鼠笼异步风力发电机(SCIM)无功功率对机端电压和有功功率的表达式,修正了原-对偶内点法中的雅可比矩阵和海森矩阵,协调了算法的计算精度与迭代效率。采用连续潮流法计算了不同节点的穿透功率极限,得到SCIM和恒功率因数控制的双馈感应风力发电机(DFIG)不同穿透率下的可用输电能力(ATC)值。仿真结果表明,联络区域节点接入风电场大幅提升送电区与受电区间的ATC,而对于送电区的风电接入情况结论相反;DFIG的功率因数对ATC有较大的影响;通过合理的补偿措施可解决某些并网方式下算法收敛于局部最优解的问题,多节点电压越限为陷入局部最优的主因。 相似文献
82.
Limeng Liu Feng Ye Siwei Zheng Bo Peng Wei Luo Zhiguo Zhang Yu Zhou 《Journal of the European Ceramic Society》2012,32(10):2487-2494
Translucent α-SiAlON ceramics were synthesized by hot pressing and spark plasma sintering. The in-line transmittance of the visible-infrared light through the α-SiAlON ceramics was discussed in correlation with the SiAlON compositions, rare earth dopant types, microstructures, and the refractive index anisotropy of the α-SiAlON grains. The results showed that the α-SiAlON ceramics had a refractive index about 2.17 and a refractive index anisotropy about 0.014. The birefringent losses due to the index anisotropy were the main reason for the severe transmission degradation in the visible light regions in the transmission curves. Accordingly, smaller grain sizes could be used to counteract the large birefringent losses to improve the in-line transmittance of the short wavelength light. 相似文献
83.
Limeng Yin Song Wei Zhangliang Xu Yanfei Geng 《Journal of Materials Science: Materials in Electronics》2013,24(4):1369-1374
Solder joints in electronic packaging systems are becoming smaller and smaller to meet the miniaturization requirements of electronic products and high density interconnect technology. Furthermore, many properties of the real solder joints at the microscale level are obviously different from that of bulk solder materials. Creep, as one of the key mechanical properties at elevated temperatures, can impair the reliability of miniature solder joints in electronic devices. However, there is a lack of knowledge about the comparative creep properties of microscale solder joints of different sizes. Most previous studies have focused on the creep properties of bulk solder materials or solder joints of the same size. In this research, to determine whether a size effect exists for creep properties of solder joints or not, we characterized the creep behaviors of Sn–3.0Ag–0.5Cu lead-free solder joints under tensile loading modes using microscale butt-joint specimens with a copper-wire/solder/copper-wire sandwich structure with two different sizes. Also, the creep failure mechanisms were investigated. Experimental results show that the creep activation energy and creep stress exponent are very similar for both sizes of solder joint. However, under the same testing conditions, the joints with a larger size exhibit a much higher steady-state creep rate and a shorter creep lifetime than the smaller joints. 相似文献
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Yavari F Chen L Zandiatashbar A Yu Z Koratkar N 《Journal of nanoscience and nanotechnology》2012,12(4):3165-3169
Both one-dimensional carbon nanotubes as well as two-dimensional graphene sheets have been extensively investigated as nanofillers in composites. However there are very few reports on their combined use in composite materials. Here we report the mechanical properties including Young's modulus, tensile strength and fatigue properties of an epoxy polymer reinforced with various combinations of graphene and carbon nanotube fillers- i.e., nanotubes alone, graphene alone and a mixture of graphene and nanotubes. We find that at low nanofillers loadings (< 0.1% weight), the graphene fillers performed better than both singlewalled as well as multiwalled carbon nanotubes. However, interestingly it was the combination of carbon nanotubes with graphene that yielded the greatest improvement in mechanical properties. Optical microscopy of thin micro-tomed slices of the composites indicated that in the presence of the nanotubes the graphene sheets appear to have aggregated into chains forming a network structure. Such long range ordering of the nanofillers is very unusual in a nanocomposite system and is likely responsible for the enhanced mechanical properties. 相似文献
86.
Limeng Liu Feng Ye Yu Zhou Zhiguo Zhang Qinglong Hou 《Journal of the European Ceramic Society》2010,30(12):2683-2689
Yb- and Y-doped α-SiAlON ceramics were effectively bonded by spark plasma sintering in less than 20 min without using any interlayer materials at 1650–1700 °C. The microstructures and mechanical properties of the joints were investigated by means of SEM, STEM, EDX, and three-point bending tests. The results showed that α-SiAlON joint formation was accompanied by fundamental rare earth diffusion. The intergranular liquids in the α-SiAlON ceramics at the bonding temperatures provided the diffusion paths for the species. α-SiAlON grain growth across the joining interfaces modified the joint microstructures to secure high bonding strength. 相似文献
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89.
为掌握渭南市道路积尘分布特征及影响因素, 获取道路积尘本地化参数和道路扬尘的管控依据, 基于光散射
法利用道路积尘负荷车载式快速监测系统对渭南市城市道路积尘负荷进行了测定, 分析了不同类型道路的积尘负荷
特征, 并研究了车流量、车重及道路抑尘方式等与积尘负荷的关系。研究结果表明, 渭南市道路积尘负荷平均值为
1.13 g·m−2, 不同类型道路积尘负荷大小呈支路 (1.79 g·m−2) > 次干道 (1.22 g·m−2) > 省道 (1.08 g·m−2) > 主干道 (0.94
g·m−2) > 国道 (0.71 g·m−2) 的特征; 车流量和车速变化与道路积尘负荷值均呈负相关, 即车流量和车速越大, 积尘负荷
值越小; 此外, 洒水能有效降低道路积尘负荷值, 但保持时间较短, 因此建议改变重洒水弱清扫的作业模式, 重点关注
清扫除尘。 相似文献
90.