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排序方式: 共有274条查询结果,搜索用时 437 毫秒
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用室内击实试验方法对毛乌素沙漠风积砂的压实性能进行研究,发现风积砂在干燥状态及最优含水率状态下均有较好的压实性能(即所谓双峰值),据此对风积砂在干燥状态下碾压的施工方法提供理论支持,从而节约工程成本. 相似文献
263.
针对模糊C均值(FCM)算法聚类结果对初始中心点敏感以及聚类过程中没有考虑到不同密度样本点在聚类过程中影响力不同的缺陷,提出了一种密度峰值和样本点空间邻域信息优化的FCM算法。改进后的算法选择数据集中具有局部密度峰值的样本点或者局部密度较大的样本点作为初始聚类中心,充分考虑样本点邻域之间的关系,增加局部密度值大的样本点在聚类中心迭代计算过程中的影响力,从而达到优化FCM算法聚类效果的目的。理论分析和在人造数据集、加州大学欧文分校(UCI)机器学习数据库中真实数据上的实验结果表明,改进后算法的抗噪性、聚类效果和全局收敛能力均优于传统FCM算法。 相似文献
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WAN Di-qing HE Bo-lin XIONG Guang-yao CHEN Zhao-xia WANG Jin-cheng YANG Gen-cang 《中国有色金属学会会刊》2010,20(Z2)
The dynamic mechanical analyzer (DMA) was applied to investigate the damping properties of Mg-Cu based alloys. The results show that the as-cast hypoeutectic Mg-Cu binary alloys exhibit ultra-high damping capacities, while the eutectic Mg-Cu alloy exhibits low damping capacity. The strain amplitude dependent damping performance reveals that the dislocation damping mainly dominates in Mg-Cu alloys. Furthermore, the influence of eutectic phase on damping mechanisms of Mg-Cu binary alloys was discussed in detail and the effect of Si addition on the damping of Mg-1%Cu based alloy was also reported. Two damping peaks are observed on the temperature dependent spectrum of Mg-Cu based alloys. One is located at room temperature, which is dislocation related peak; and the other is located at moderate temperature, which is caused by the grain boundary sliding. 相似文献
266.
In order to extract the information of 662-keV 137Cs spectra from the overlapping peaks with 583-keV 208Tl,609-keV 214Bi,the overlapping peaks are measured by in-situ γ-ray spectrometer using a NaI(Tl) detector.The spectral model is optimized by the Gaussian fitting algorithm,and the optimized fitting indexes for fitting/original value are from 0.96 to 0.99.Gaussian fitting verified by experiment is feasible for γ-ray spectrum analysis.The full energy peak of 137Cs is extracted correctly from the overlapping peaks,it is important for in-situ γ-ray spectrometer to estimate contamination of 137Cs in radiated environment and nuclear accident. 相似文献
267.
H.B. Wu H.T. Jiang S.W. Yang D. Tang X.L. He 《金属学报(英文版)》2007,20(5):313-326
Cooled in water after isothermal relaxation of deformed austenite for different times, an Nb-bearing microalloyed steel always exhibits synthetic microstructures, in which bainitic ferrite dominates. Dislocation configurations and distributions of strain induced precipitates inside bainitic ferrite of samples relaxed for different times were distinct. When compared with the austenite model steel, which maintained fcc structure even at room temperature, the strain induced precipitates were not found in the sample without relaxation whereas these were distributed outside dislocations in sample relaxed for 1000s. Most of the strain induced precipitates distribute along dislocations and pin dislocations in sample relaxed for appropriate time. After bainitic transformation, the dislocations formed in deformed austenite remain to be pinned by the precipitates. When these samples were reheated to and held at 650 or 700℃, the non-equilibrious microstructures tended to evolve into equilibrious ones. The sample relaxed for 60s displayed the highest thermo-stability, whereas microstructure evolution was the quickest in the sample relaxed for 1000s even though it was the softest prior to reheating. Dislocations inside laths got rid of pinning of precipitates, and their polygonization became the precursor to the evolution of microstructures during reheated and held, followed by gradual disappearance of lath boundaries caused by dislocation climbing. Finally, recrystallization occurred and polygonal ferrite appeared. By hardness measurement, it was found that softening is not a single process occurring during reheated, in which hardness fluctuates with time. There were two peaks in the hardness-time curve of each sample having undergone relaxation, while single peak occured in the curve of the sample not being relaxed. These results indicated that the thermo-stability of microstructures was determined by their history of formation to a considerable degree. 相似文献
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269.
R&D strategies of companies with low and high technological levels are discussed based on the concept of technology convergence and divergence. However, empirically detecting enterprise technology convergence in the distribution of enterprise technology (total productivity increase) over time and identifying key change factors are challenging. This study used a novel statistical indicator that captures the internal technology distribution change with a single number to clearly measure the technology distribution peak as a change in critical bandwidth for enterprise technology convergence and presented it as evidence of each technology convergence or divergence. Furthermore, this study applied the quantitative technology convergence identification method. Technology convergence appeared from the separation of total corporate productivity distribution of 69 IT companies in Korea in 2019–2020 rather than in 2015–2016. Results indicated that when the total technological level was separated from the technology leading and technology catch-up, IT companies were found to be pursuing R&D strategies for technology catch-up. 相似文献
270.
“仿生耳”对接收到的语言信号的特征峰进行提取,经A/D转换,编码,解码等处理,对神经性耳聋患者的残留听神经元进行刺激,使其在一定程度上的恢复语音识别能力。 相似文献