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171.
米国发 《武汉理工大学学报(材料科学英文版)》2009,24(3):424-427
The microstructure and mechanical properties of rapidly solidified Al-Cr alloys were investigated by XRD, TEM and microhardness
testing instrument. The results indicate that the matrix of rapidly solidified Al-Cr alloys is α-Al solid solution when the Cr content is lower than 4 wt%. However, when the Cr content is above 4 wt%, the microstructures
of rapidly solidified Al-Cr alloys are different along cross section. The microstructure of alloy contacting copper roller
consists of α-Al and a few intermetallic compounds. With the increase of distance from copper roller, the matrix consists of α-Al and spherical intermetallic compounds which conglomerate in α-Al matrix. These intermetallic compounds are Al7Cr, Al11Cr and Al4Cr. The tensile strength has the maximal value when the Cr content is about 8 wt%. The annealed microstructures show that
supersaturated α-Al solid solution dissolved with increasing anneal temperature. The starting temperature of the second phase precipitated
from the supersaturated α-Al solid solution desponds on the supersaturation. Meanwhile, the microhardness of rapidly solidified Al-Cr alloy reaches
maximal value after annealing at 300 °C.
Funded by the Innovation Fund for Outstanding Scholar of Henan Province (No. 0621000700) 相似文献
172.
Jong‐Chul Yoon Hyeong Ryeol Kam Jeong‐Mo Hong Shin Jin Kang Chang‐Hun Kim 《Computer Graphics Forum》2009,28(7):1853-1859
We propose a fast and effective technique to improve sub‐grid visual details of the grid based fluid simulation. Our method procedurally synthesizes the flow fields coming from the incompressible Navier‐Stokes solver and the vorticity fields generated by vortex particle method for sub‐grid turbulence. We are able to efficiently animate smoke which is highly turbulent and swirling with small scale details. Since this technique does not solve the linear system in high‐resolution grids, it can perform fluid simulation more rapidly. We can easily estimate the influence of turbulent and swirling effect to the fluid flow. 相似文献
173.
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175.
为分析一类含间隙结构的振动特性及为保护特定子结构而预留间隙的合理性,根据其振动试验结果,采用假设模态法的思想,将该类带间隙的非线性结构按其子结构的一阶弯曲模态简化为带间隙的单自由度与二自由度弹簧-质量系统,分析了不同激励条件下间隙对系统动力学响应的影响.分析结果表明:此类结构中,间隙具有阻碍振动传递的性质,预留间隙是合理的. 相似文献
176.
天线外定标是实现星载SAR天线方向图在轨测试的主要手段。天线方向图的准确测量,对星载SAR图像的应用具有重要作用。分布目标辐射定标在星载SAR天线方向图测试中受到广泛重视。亚马逊热带雨林的后向散射系数呈现大面积的均匀性和稳定性,故成为分布目标定标最主要的定标场。该文在分布目标定标原理的基础上,对基于亚马逊热带雨林的星载SAR天线方向图测量算法进行了研究,提出了采用K.Pearson统计量非参数假设检验的一致性处理算法,并采用Levenberg-Marquard算法(LM算法)估计俯仰向天线方向图模型参数。仿真数据验证了算法的可靠性和准确性。 相似文献
177.
Shijing Mo Xiuqiao Zhao Yan Chen Liang Liu Ruiwei Wang Qinghong Xu 《Materials Chemistry and Physics》2013
An organic–inorganic hybrid zirconium phosphonate (noted as ZrNCP) with window type porous structure was synthesized by using β–alanine–N,N-dimethylidenephosphonic acid and zirconium dichloride oxide octahydrate. The sample possesses regular flake morphology, and these flakes have porous framework structure, which were characterized by SEM, HRTEM, N2 sorption, XRD, TGA–DSC, elemental analysis, XPS, and FT-IR spectroscopy techniques. The as-prepared ZrNCP can be used as catalyst to oxidation of formaldehyde after Fe3+ was intercalated and coordinated with nitrogen and carbonyl groups inside the porous walls of ZrNCP. 90.1% of oxidized efficiency was obtained when the catalyst was added into formaldehyde solution (40% water solution) at 80 °C. 相似文献
178.
Mo Chen Xiaojuan Wang Mingshu He Lei Jin Khalid Javeed Xiaojun Wang 《计算机、材料和连续体(英文)》2020,64(2):941-959
Attacks on websites and network servers are among the most critical threats in
network security. Network behavior identification is one of the most effective ways to
identify malicious network intrusions. Analyzing abnormal network traffic patterns and
traffic classification based on labeled network traffic data are among the most effective
approaches for network behavior identification. Traditional methods for network traffic
classification utilize algorithms such as Naive Bayes, Decision Tree and XGBoost.
However, network traffic classification, which is required for network behavior
identification, generally suffers from the problem of low accuracy even with the recently
proposed deep learning models. To improve network traffic classification accuracy thus
improving network intrusion detection rate, this paper proposes a new network traffic
classification model, called ArcMargin, which incorporates metric learning into a
convolutional neural network (CNN) to make the CNN model more discriminative.
ArcMargin maps network traffic samples from the same category more closely while
samples from different categories are mapped as far apart as possible. The metric learning
regularization feature is called additive angular margin loss, and it is embedded in the
object function of traditional CNN models. The proposed ArcMargin model is validated
with three datasets and is compared with several other related algorithms. According to a
set of classification indicators, the ArcMargin model is proofed to have better
performances in both network traffic classification tasks and open-set tasks. Moreover, in
open-set tasks, the ArcMargin model can cluster unknown data classes that do not exist in
the previous training dataset. 相似文献
179.
Josef Jirák Ladislav Koudelka Jaroslav Pospíšil Petr Mošner Lionel Montagne Laurent Delevoye 《Journal of Materials Science》2007,42(20):8592-8598
Glasses of the ternary system ZnO–Bi2O3–P2O5 were prepared and studied in two compositional series 50ZnO–xBi2O3–(50 − x)P2O5 and (50 − y)ZnO–yBi2O3–50P2O5. Two distinct glass-forming regions were found in the 50ZnO–xBi2O3–(50 − x)P2O5 glass series with x = 0–10 and 20–35 mol.% Bi2O3. All prepared Bi2O3-containing glasses reveal a high chemical durability. Small additions of Bi2O3 (∼5 mol.%) improve thermal stability of glasses. All glasses crystallize on heating within the temperature range of 505–583 °C.
Structural studies by Raman and 31P MAS NMR spectroscopies showed the rapid depolymerisation of phosphate chains within the first region with x = 0–15 and the presence of isolated Q0 phosphate units within the second region with x = 20–35. Raman studies showed that bismuth is incorporated in the glass structure in BiO6 units and their vibrational bands were observed within the spectral region of 350–700 cm−1. The evolution of properties and the spectroscopic data are both in accordance with a network former effect of Bi2O3. 相似文献
180.
The use of large quantities of chemical fertilizers is usually associated with environmental problems. A lot of work has been done on the concentrations of heavy metals and radionuclides in chemical fertilizers, but little work has focused on the occurrence of semi-volatile organic compounds (SVOCs). In this study the occurrence of 43 SVOCs listed as priority pollutants in 22 widely used-fertilizers of China was determined by gas chromatography coupled with mass spectrometry. Twenty-six SVOCs were detected with different detection frequencies and concentrations. The most abundant compounds were phthalic acid esters (PAEs; ranging from 1.17 to 2795 microg kg(-1) dry weight, d.w.) and nitroaromatics (up to 9765 microg kg(-1) d.w.), followed by polycyclic aromatic hydrocarbons (PAHs; <140 microg kg(-1) d.w.) and halogenated hydrocarbons (<900 microg kg(-1) d.w.). Chlorobenzenes and haloethers occurred generally at low concentrations. There are large variations in concentrations of various compounds in different fertilizers, and the total concentrations of each class of contaminants varied widely, too. The highest levels of sum concentration for 16 PAHs, for 6 PAEs and for nitroaromatics were found in organic fertilizer containing pesticide and soil amendments. Concentrations of SVOCs in coated fertilizers (the controlled release fertilizer with coating) were considerably higher than those in the corresponding fertilizers without coating. The occurrence frequencies of SVOCs in the straight fertilizers (containing only one of the major plant nutrients) were lower than in the other fertilizers. 相似文献