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41.
吴光琼 《水资源与水工程学报》2016,27(2):118-121
针对水位流量关系拟合中相关参数难以确定的不足,利用一种新型群体智能仿生算法——群居蜘蛛优化算法(SSO)优化水位流量关系的相关参数,以云南省丽江仁里站和总管田站水位流量关系拟合为例进行实例研究,并与粒子群优化算法(PSO)、最小二乘法(LSM)拟合结果进行对比。结果表明:SSO算法对仁里站和总管田站水位流量关系拟合的平均相对误差绝对值分别为0.57%、0.53%,拟合精度优于PSO、LSM算法。SSO算法具有收敛速度快、全局寻优能力强等特点,利用SSO算法优化水位流量关系可以获得更好的拟合效果。 相似文献
42.
In inertial navigation system(INS) and global positioning system(GPS) integrated system, GPS antennas are usually not located at the same location as the inertial measurement unit(IMU) of the INS, so the lever arm effect exists, which makes the observation equation highly nonlinear. The INS/GPS integration with constant lever arm effect is studied. The position relation of IMU and GPS’s antenna is represented in the earth centered earth fixed frame, while the velocity relation of these two systems is represented in local horizontal frame. Due to the small integration time interval of INS, i.e. 0.1 s in this work, the nonlinearity in the INS error equation is trivial, so the linear INS error model is constructed and addressed by Kalman filter’s prediction step. On the other hand, the high nonlinearity in the observation equation due to lever arm effect is addressed by unscented Kalman filter’s update step to attain higher accuracy and better applicability. Simulation is designed and the performance of the hybrid filter is validated. 相似文献
43.
在室温下对工业纯铝进行T型等通道挤压变形(T-ECAP),研究了挤压速度(5、12、60、120、180mm/min)和挤压道次(1道次、2道次、4道次)对纯铝微观组织与力学性能的影响.结果表明:不同挤压速度下,1道次挤压变形可以将晶粒细化到1μm以下,但是微观组织存在不均匀性;随着挤压道次的增加,晶粒逐渐细化,4道次时晶粒大小为350nm.在试样的纵向中心位置,显微硬度呈现“两端高,中间低”的漏斗状分布;随着挤压道次的增加,漏斗状的硬度分布逐渐减弱,4道次挤压变形后,硬度逐渐趋于均匀.挤压速度180mm/min时,拉伸强度呈现反常的Hall-Petch关系.随着挤压道次的增加,伸长率逐渐增大,2道次挤压变形后,拉伸强度趋于平稳. 相似文献
44.
采用原位还原碳化反应制备超细WC-10%Co,在1250、1300、1350、1380℃进行预烧结处理,得到的预烧结块体在1450℃、5 MPa氩气条件下进行低压二次烧结;分析对比了预烧结块体和二次烧结块体的显微组织,并对二次烧结合金进行了性能测试.结果表明:不同温度预烧结块体经低压二次烧结后,可有效抑制晶粒异常长大现象,二次烧结后合金具有高的断裂韧性,最高值达16.1MPa·m-1/2.在1 350、1 380℃下预烧结块体经低压二次烧结后均具有均匀的合金组织,其中经过1380℃预烧结块体横向断裂强度为3260 MPa. 相似文献
45.
Yingjie Zhang Tao Wei Alan Xu Pranesh Dayal Daniel J. Gregg 《Journal of the American Ceramic Society》2021,104(11):5981-5989
As potential waste forms for immobilizing actinide-rich radioactive wastes, Eu2Ti2O7 (Eu as a surrogate for minor actinides) pyrochlore glass-ceramics were fabricated via hot isostatic pressing (HIPing) at 1200°C. The structure and microstructure at the reaction interface between the glass-ceramic waste form and the stainless steel (SS) canister under HIPing conditions were carefully investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron single crystal X-ray diffraction (SC-XRD). The interactions at the reaction interface led to the formations of a ~10-µm-thick Cr2O3 layer as the oxidation front of the SS and a layer of a mixed oxide phase (Eu1.25SiCr0.8Ti1.2O7.5) on the glass-ceramic side of the reaction interface. The crystal structure of such a unique mixed oxide phase was revealed indubitably with a combination of synchrotron SC-XRD and TEM assisted with a focused ion beam (FIB) SEM system. The improved structural understanding of the reaction interface will help to support the utilization of HIPing as a versatile hot consolidation process for the treatment of radioactive wastes. 相似文献
46.
介绍了盒形件弯曲模具的设计思路、模具结构 ,着重介绍了弯周边模具主要工作零件设计 ,其中活动凸模横向移动装置是一种较好的弯曲件脱模机构。 相似文献
47.
谷万里 《中国有色金属学会会刊》2006,16(B01):398-401
Nano-sized Al/SiC powders were prepared by mechanical alloying method. Two sorts of SiC particle, i.e., nano-sized and popular micron-sized SiC were utilized. The particle size and microstructure of the milled powder were characterised. Effects of the particle size and agglomerate state of SiC, as well as the microstructure of Al/SiC nanocomposite were studied by SEM and TEM. The results show that nano-sized SiC particles is dispersed in aluminium uniformly after ball milled for only 2 h, whereas the similar process need about 10 h for popular micron-sized SiC particle. The bulk Al/SiC nanocomposite can be fabricated by hot pressing the nano-sized Al/SiC powders at temperature about 723 K under pressure of 100 MPa. 相似文献
48.
Hyung-Jun Chang Heung Nam Han Sang-Hoon Joo Kwang-Hee Lee Kyu Hwan Oh 《International Journal of Machine Tools and Manufacture》2007,47(10):1573-1582
The hot roll pressing of iron powder with several rotating speeds was carried out on a pilot-plant scale. From these experiments, it was confirmed that the surface temperature of roller was increased with increasing its rotating speed. It was also known that the heat transfer coefficient between the iron powder and the roller surface is closely related with the rotating speed of roller. These results were quantitatively described by using a mathematical model which was derived based on the steady-state heat transfer during hot roll pressing. In addition, the densification behavior of iron powder during the hot roll pressing was simulated by a finite element model based on the arbitrary Lagrangian and Eulerian (ALE) method and a yield criterion for metal powder. From these models, the maximum critical rotating speed of roller during the hot roll pressing, in which the roller could hold out against the thermal fracture, could be determined. 相似文献
49.
Thermoelectric properties of mechanically alloyed iron disilicides consolidated by various processes
Mn doped p-type iron disilicide powders have been produced by a mechanical alloying process. As-milled powders were of metastable
state and mostly transformed to β-FeSi2 phase by subsequent isothermal annealing. As-milled powders were consolidated by various processes such as sintering of the
cold compact in vacuum, vacuum hot pressing (VHP), and spray drying/atmospheric plasma thermal spraying. Phase transitions
during the processes were investigated using XRD, EDS, and SEM. As-consolidated specimens consisted of a mixture of α-Fe2Si5 and ε-FeSi phases, which were gradually transformed into a thermoelectric semiconducting α-FeSi2 phase by subsequent isothermal annealing in the vicinity of 845°C in vacuum. However, some residual α and ε phases remained
even after prolonged annealing. Thermoelectric properties were measured as a function of temperature and correlated with phase
transformation. They showed optimum values in the vacuum hot pressed specimen due to a higher fraction of β phase and/or higher
density. 相似文献
50.