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The microstructures of in-situ synthesized TiC by Ti-CNTs reaction in Cu melts

Xu Xuexia, Wang Yong, Wang Qing, Dong Guozhen, Li Wenbin, Li Guowei, Lv YaDong, Zhang Jin, Ding Haimin

Materials Science Poland

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2022

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Vol. 40, No. 1

145--158

EN

In order to study the influence of the carbon nanotubes (CNTs) as a source of carbon on the microstructure of in-situ synthesized TiC in Cu melts, CNTs and Ti powders were introduced into melted Cu to prepare TiC-reinforced Cu matrix composites. The influence of Ti/C ratio and Si on the microstructures and properties of the composites were also examined. It is found that CNTs can be effectively wetted through the Ti-C reaction and successfully introduced into Cu melt to synthesize TiC. In examining the changes in Ti/C ratio, it was found that an increase in the Ti content may result in the decrease of TiC agglomeration and improvement of TiC dispersion, while simultaneously causing an increase in the TiC particle size. Besides, while the addition of Si into Ti-CNTs mixture can also improve the distribution of TiC, the effect is weak compared with that of increasing the content of Ti. It was also found that the highest hardness (238.8 HV) is achieved by the Cu-Ti-C composite with the highest Ti/C ratio, while the electrical conductivities of all the prepared composites are relatively low, which should be due to the insufficient reaction between Ti and CNTs.

2

Dynamic performance and stability analysis of an active inerter-based suspension with time-delayed acceleration feedback control

Wang Yong, Jin Xian-Yu, Zhang Yun-Shun, Ding Hu, Chen Li-Qun

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 2

art. no. e140687

EN

An active inerter-based suspension with acceleration feedback control is proposed in this paper, the time delay generated in the controllers and actuators is considered, which constitutes the time-delayed active inerter-based (TDA-IB) suspension. The dynamic equation of the TDA-IB suspension is established and is a neutral type of delay differential equation (NDDE) in which the time delay exists in the highestorder derivative. The stability analysis is conducted by calculating the number of unstable characteristic roots based on the definite integral stability method, the stable and unstable regions are determined. The effect of time delay and feedback gain on the dynamic performance of the TDA-IB suspension under harmonic, random, and shock excitations is studied in detail and compared with the parallel-connected inerterbased (PC-IB) and traditional suspensions. The results show that the TDA-IB suspension is asymptotically stable for smaller feedback gain and time delay, through increasing the feedback gain, the stable regions shrink, and a smaller time delay could cause the system to become unstable. Furthermore, the time delay could regulate the resonance peak around the unsprung mass natural frequency and generate multiple high-frequency resonance peaks. If the time delay is chosen appropriately and falls into the stable range, the TDA-IB suspension could improve the dynamic performance for the suspension stroke and dynamic tire load while having a deterioration for the vehicle body acceleration compared with the PC-IB and traditional suspensions.

3

Dynamic characteristics of underframe semi-active inerter-based suspended device for high-speed train based on LQR control

Wang Yong, Li Hao-Xuan, Meng Hao-Dong, Wang Yang

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2022

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Vol. 70, nr 4

art. no. e141722

EN

The underframe passive inerter-based suspended device, based on the inerter-spring-damper vibration attenuation structure, could improve the dynamic performance of the train body, but its parameters are fixed and cannot meet the dynamic performance requirements under different operating conditions. Therefore, a semi-active inerter-based suspended device based on the linear quadratic regulator (LQR) control strategy is proposed to further enhance the dynamic performance. The rigid-flexible coupling vertical dynamic model of the train body and an underframe semi-active inerter-based suspended device are established. The structural parameters of the semi-active inerter-based suspended device are adjusted using LQR control strategy. Dynamic response of the system is obtained using the virtual excitation method. The dynamic characteristic of the system is evaluated using the Sperling index and compared with those of the passive and semi-active traditional suspended devices as well as the passive inerter-based suspended devices. The vertical vibration acceleration of the train body and Sperling index using the semi-active inerter-based suspended device is the smallest among the four suspended devices, which denotes the advantages of using the inerter and LQR control strategy. The semi-active inerter-based suspended device could decrease the vertical vibration acceleration of the train body and further suppress its elastic vibration in the lower frequency band, more effectively than the other three suspended devices. Overall, the semi-active inerter-based suspended device could significantly reduce elastic vibration of the train body and improve its dynamical performance.

4

Diversity and Composition of Rhizosphere Fungal Community in Pure and Mixed Forests of South China

Wen Xinmiao, Wang Renjie, Jiang Yi, Deng Xiaojun, Wei Shuoxin, Liu Xiongsheng, Wang Yong

Polish Journal of Ecology

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2021

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Vol. 69, nr 2

111--123

EN

Rhizosphere fungal communities are of critical importance for forest health. Microbial diversity varies with forest types due to tree species. In order to examine the influence of forest types and species composition on fungal community diversity in rhizosphere soil, the field sampling was conducted in the pure and mixed forest stands of Castanopsis hystrix in a subtropical region of China. Soil samples were taken from four forest types: Castanopsis hystrix pure forests (CH), Castanopsis hystrix × Pinus elliottii mixed forests (CHPE), Castanopsis hystrix × Michelia macclurei mixed forests (CHMM), and Castanopsis hystrix × Mytilaria laosensis mixed forests (CHML), and the species composition and structure of rhizosphere fungal community were examined by using high-throughput sequencing approach for 18S rRNA genes. The results showed that the amount of OTUs (operational taxonomic units) were 288, 331, 334 and 293 in CHML, CHMM, CHPE and CH stands, respectively, and these fungal communities were affiliated with 13 phyla, 28 classes, 85 orders, 87 families, and 131 genera. The fungal diversity was greater in CHMM and CHPE stands than in CH stands. The compositions were similar in CHMM and CHPE stands while those were significantly different in CHML and CH stands. The cladograms and co-expression network analysis showed that Ascomycota, Basidiomycota, Mortierellomycota and Rozellomycota were the dominant phyla. The study results implied that mixed forests might have a high potential for improving the microbial community diversity with formation of key species of microbial taxa due to the favorable microclimate and quality of litter composition occuring in mixed forests.

5

Classification of high resolution satellite images using improved U-Net

Wang Yong, Zhang Dongfang, Dai Guangming

International Journal of Applied Mathematics and Computer Science

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2020

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Vol. 30, no. 3

399--413

EN

Satellite image classification is essential for many socio-economic and environmental applications of geographic information systems, including urban and regional planning, conservation and management of natural resources, etc. In this paper, we propose a deep learning architecture to perform the pixel-level understanding of high spatial resolution satellite images and apply it to image classification tasks. Specifically, we augment the spatial pyramid pooling module with image-level features encoding the global context, and integrate it into the U-Net structure. The proposed model solves the problem consisting in the fact that U-Net tends to lose object boundaries after multiple pooling operations. In our experiments, two public datasets are used to assess the performance of the proposed model. Comparison with the results from the published algorithms demonstrates the effectiveness of our approach.