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1

Investigation on self‑healing of neat and polymer modified asphalt binders

Wang C., Xue L., Xie W., Cao W.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

27--36

EN

The paving asphalts have long been recognized to be capable of self-healing. The objective of this study was to evaluate the healing potential of asphalt binders and investigate its relationship with molecular characteristics in terms of composition and structures. Five neat and styrene–butadiene–styrene (SBS) modified asphalt binders were characterized using the recently developed linear amplitude sweep-based healing test. The data were analyzed based on the viscoelastic continuum damage theory to establish healing master curves and determine the healing rate HR. Chemical evaluation methods included saturates, aromatics, resins, and asphaltenes fractionation, gel permeation chromatography, and nuclear magnetic resonance spectroscopy. Results indicated that the presence of more light/low-polarity fractions of saturates and aromatics or higher concentrations of small molecules promoted healing, as these molecules were expected to have higher mobility facilitating molecular diffusion across crack interfaces. Lower percentages of aromatic ring structures and more aliphatic chains corresponded to higher healing rates. The SBS-modified asphalt binders contained higher concentrations of aromatic rings, but still provided comparable healing potential with the neat asphalts.

2

Plantar pressure analysis of above-knee amputee with a developed microprocessor-controlled prosthetic knee

Cao W., Yu H., Meng Q., Li S.

Acta of Bioengineering and Biomechanics

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2018

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Vol. 20, no. 4

33--40

EN

Human gait motion analysis was one useful method for lower limb prosthesis study. The most often measured parameters were plantar pressure, kinetic and kinematic parameters. It was indispensable for prosthetic knee design and performance assessment. The aim of this study was to analysis the plantar pressure in traumatic above-knee amputee equipped with a developed microprocessor-controlled prosthetic knee. Methods: The maximum force of forefoot and rearfoot, the average vertical reaction force and pressure and the centre of pressure (COP) offset trajectories of ten above-knee amputees under different walking speeds were obtained. Results: Both forefoot and rearfoot force were bigger in intact leg than prosthetic leg. As the speed increased, the pressure increased in both sides. Forefoot bore more pressure than rearfoot in both legs. The average vertical pressure and force both increased along with the increase of speed. The force and pressure of intact side were always bigger than the prosthetic side. The trend of COP and gait line of the prosthetic and intact side had no significant difference. The length of the gait line of prosthetic side was greater than the intact side. Conclusions: The results of this study exhibited reduced plantar pressure in the prosthetic side. The typical butterfly diagrams were produced during different walking speeds. It indicated that the stability of the microprocessor-controlled prosthetic knee could be guaranteed.

3

Flexible diamond-like carbon film prepared by hydrothermal electrochemical method

Tao Y., Yi D., Zhu B., Cao W.

Materials Science Poland

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2017

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Vol. 35, No. 3

447--453

EN

Diamond-like carbon (DLC) thin films were prepared by hydrothermal electrochemical method in one-step process. The structural characterization of these films was carried out by scanning electron microscopy (SEM), Raman spectroscopy, and infrared reflectance spectroscopy (IR). It was found that there was an increased sp2 carbon content but decreased sp3 carbon and hydrogen contents with an increase in current density. The flexibility and internal stresses of the DLC films were affected by hydrogen, sp3 amorphous carbon and ordered crystalline sp2 carbon contents. The highly flexible DLC films with high sp3 carbon and hydrogen contents were prepared at a current density of 0.001 mA/cm2.

4

Electrostatic Hazards Assessment of Nitramine Explosives: Resistivity, Charge Accumulation and Discharge Sensitivity

Peng Q., Cao W., Zhou W., He Z., Jiang W., Chen W.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 3

755--769

EN

The electrostatic hazards of nitramine explosives (RDX, HMX) were assessed in this paper. The resistivities of different particle-size RDX and HMX were tested by a device designed and manufactured according to the standard ISO/IEC 80079-20-2:2016. This work shows that the resistivities of uncompacted RDX and HMX increase as the particle size decreases. Charging characteristics test experiments were also carried out using a so-called sieve method. Using this method, the influence of aperture size on charge accumulation of RDX was studied, and the characteristics of electrostatic accumulation of different particle-size RDX and HMX sieved with 50 mesh standard sieve were compared. The results show that the absolute value of the charge accumulation increases as the mesh number increases (i.e. the aperture size decreases), and increases as the particle size is decreased, indicating that nano-sized RDX and nano-sized HMX accumulate static electricity more easily than conventional micron-sized ones. Finally, the electrostatic discharge (ESD) sensitivity of nano-sized RDX and nano-sized HMX was investigated. Nano-sized nitramine explosives were found to have a higher ESD sensitivity than micron-sized ones.

5

Spatial and seasonal variations of large tintinnid ciliates in Shenhu Bay of China

Wang Y., Zhang W., Lin Y., Zheng L., Cao W., Yang J.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 3

292--302

EN

In this study, the spatial distribution and seasonal variation of large tintinnids (>76 μm) were investigated in Shenhu Bay during three seasons of 2012. Of the 36 species identified, 9 were dominant (i.e. Tintinnopsis radix, Leprotintinnus simplex, Tintinnopsis japonica, Tintinnopsis tubulosoides, Leprotintinnus nordqvisti, Tintinnopsis beroidea, Stenosemella parvicollis, Tintinnidium primitivum, Tintinnopsis nana). A clear seasonal shift of the taxonomic composition as well as the lorica size of the dominant species was observed. The highest numbers of tintinnid species occurred in spring, while the highest abundance and biomass occurred in summer. Clustering indicated that the seasonal variations of the community structure were more obvious than spatial variations. Spearman correlation analysis revealed that density of phytoplankton prey had a significant impact on the tintinnid abundance. Redundancy analysis (RDA) illustrated that temperature, salinity and the nutrient level were the most important abiotic factors affecting the spatial and seasonal pattern of tintinnid communities in Shenhu Bay.

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Spatial pattern of the planktonic ciliate community and its relationship with the environment in spring in the northern Beibu Gulf, South China Sea

Wang Y., Zhang W., Lin Y., Zheng L., Cao W., Yang J.

Oceanological and Hydrobiological Studies

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2013

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Vol. 42, No. 4

470--479

EN

Surface water samples were collected from 19 sites in the northern Beibu Gulf in April 2011. Species composition and abundance of planktonic ciliates were investigated. They were combined with environmental data to obtain the spatial pattern of the ciliate community and its relationship with the environment. A total of 36 species belonging to 13 genera and 3 orders (Oligotrichida, Haptorida and Tintinnida) were identified, including 10 dominant species. All 19 samples were divided into three groups using cluster analysis and multidimensional scaling (MDS) on the basis of the ciliate species composition and abundance. Group 1 was the least abundant. The species of the order Oligotrichida dominated in Group 2. In contrast, Mesodinium species were of increased importance in Group 3. Redundancy analysis (RDA) revealed that ciliate communities were more closely related to the level of nitrogen (total nitrogen, nitrate nitrogen, nitrite nitrogen) and phosphorus (total phosphorus, active phosphorus) rather than other variables. As the levels of nitrogen and phosphorus increased, communities dominated by species from the order Oligotrichida were replaced by those dominated by Mesodinium species.