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21.
The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of ?31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < ?10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. 相似文献
22.
通过馏分切割、温和加氢相结合对中低温煤焦油进行精制处理,精制后的原料采用分级热聚制备中间相炭微球。考察了精制处理条件对原料性质、中间相炭微球宏观外貌及微晶结构的影响。采用FTIR、GC-MS、族组成、元素分析对原料进行表征,采用SEM、XRD对中间相炭微球进行表征。结果表明:中低温煤焦油中300~430℃馏分油是制备中间相炭微球的较佳馏分。300~430℃馏分油中正庚烷可溶物(HS)质量分数高达84.76%,吡啶不溶物(PI)质量分数低至0.23%,杂原子含量低,芳烃化合物的环数为2~4环。300~430℃馏分油在TH=350℃、p=8MPa、t=1.5h、剂油比1∶40(质量比)的条件下温和加氢得到的精制原料,经420℃热聚6h得制备的中间相炭微球宏观外貌、微晶结构较好。中低温煤焦油基炭微球的粒径范围为5~15μm,小球表面光滑,微观结构为地球仪型,经1450℃高温煅烧后,石墨化度达到12.33%。 相似文献
23.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
24.
根据微化工技术发展的主要趋势,针对4-溴-3-甲基苯甲醚间歇非均相合成技术存在的问题,以微筛孔反应器与玻璃微珠填充床为核心功能微设备单元构建了模块化微反应系统,并在此模块化微反应系统内对液-液非均相连续溴化合成4-溴-3-甲基苯甲醚开展研究。通过优化操作条件,在溴浓度( )为17.5%(质量分数)、溴与间甲基苯甲醚摩尔比( /nM)为1.01、反应起始温度(T)为 0℃、停留时间为0.78 min条件下,4-溴-3-甲基苯甲醚的收率大于98%,多溴代副产物的含量仅为1%。与传统间歇溴化反应相比,模块化微反应系统内连续溴化反应具有十分明显的优势:可将间歇过程连续化,在保证安全的基础上极大地提升了反应的效率(时空收率为6.5×104 kg/(m3·h));另外,该过程是由传质控制的,微反应器的传质性能优异,可极大地改善产品的选择性(多溴代副产物的量减少50%)。该研究为4-溴-3-甲基苯甲醚的连续高效安全合成提供了技术和设备依据。 相似文献
25.
Yihua Feng Peidong Yuan Li Wang Jiyun Zhang Jiahui Zhang Xuan Zhou 《International Journal of Applied Ceramic Technology》2020,17(3):1108-1118
Surface texture is considered an important measure to improve the cutting performance of a tool. In this study, we have prepared three types of textured and conventional tools on the rake face by an in-situ formed method. During the experiment, the best parameters of three types of textured tools were selected for dry cutting AISI 1045 steel at different cutting speeds. Cutting forces, cutting temperatures, workpiece surface roughness, and tool wear were measured during the cutting process. The results showed that textured tools have significantly reduced cutting force, cutting temperature, and tool wear, and the roughness of the workpiece was improved compared with the conventional tool. The micro-pit texture tool has less stress contact region than the micro-groove width texture tool, but the micro-groove width texture tool exhibiting the best cutting performance. This investigation clearly showed that the textured tool prepared by the in-situ formed method has improved cutting performance. 相似文献
26.
通过于都县黄麟地区1:5万土地质量地球化学调查,基本査明该地区农作物中硒元素及其他元素的地球化学特征,综合分析岀绿色富硒土壤分布,并优选出绿色富硒地块,为特色农产品基地建设的开发与利用提供理论依据。 相似文献
27.
Ting Cui Ling Xu Feng Ding Ahmed Alsaedi Tasawar Hayat 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1658-1676
Parameter estimation plays an important role in the field of system control. This article is concerned with the parameter estimation methods for multivariable systems in the state-space form. For the sake of solving the identification complexity caused by a large number of parameters in multivariable systems, we decompose the original multivariable system into some subsystems containing fewer parameters and study identification algorithms to estimate the parameters of each subsystem. By taking the maximum likelihood criterion function as the fitness function of the differential evolution algorithm, we present a maximum likelihood-based differential evolution (ML-DE) algorithm for parameter estimation. To improve the parameter estimation accuracy, we introduce the adaptive mutation factor and the adaptive crossover factor into the ML-DE algorithm and propose a maximum likelihood-based adaptive differential evolution algorithm. The simulation study indicates the efficiency of the proposed algorithms. 相似文献
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