| 151. |
- Wang, Dianzheng, et al.
(author)
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Reduced wear damage of carbon brushes via transfer layer upon W/Cu composite
- 2018
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In: Materials Science and Technology. - : Informa UK Limited. - 0267-0836 .- 1743-2847. ; 34:2, s. 172-178
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Journal article (peer-reviewed)abstract
- An ultrafine (similar to 100 nm) W particle-reinforced Cu matrix composite was fabricated by spark plasma sintering. The tribological properties of the fabricated W/Cu composite were tested by pin-on-disc sliding experiments and compared with those of brass alloy. The wear rate of the carbon brush when sliding against the W/Cu composite (0.102mm(3) s(-1)) was much lower than that with brass (4.83mm(3) s(-1)). Simultaneously, the W/Cu composite possessed higher conductivities and greater surface hardness than brass. The surface roughness of the W/Cu composite was found to play a critical role in improving the robustness of the tribofilm and reducing the volume loss of the carbon brush. The W/Cu composite has promising engineering applications for the long-term wear protection of self-lubricating materials.
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| 152. |
- Wang, Dian-Zheng, et al.
(author)
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Cracking Behavior in Additively Manufactured Pure Tungsten
- 2019
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In: Acta Metallurgica Sinica (English Letters). - : Springer Science and Business Media LLC. - 1006-7191 .- 2194-1289. ; 32:1, s. 127-135
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Journal article (peer-reviewed)abstract
- In this study, near fully dense (96.5%) pure tungsten bulks were additively manufactured and the cracking behavior was investigated. A crack network with a spacing of similar to 100m was observed in the fabricated bulks. It was observed that the laser scanning strategy, which could tailor the microstructure, affected the crack distribution pattern in fabricated tungsten. The calculated surface temperature difference (7300K) was much higher than the cracking criterion (800K) of tungsten, indicating that cracking is almost inevitable in laser additive manufacturing of tungsten. It could be concluded that crack network formed because the cracks emerged in every laser molten track and then interconnected in the layer-by-layer building process.
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| 153. |
- Wang, Hui-Xin, et al.
(author)
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Late Life Leisure Activities and Risk of Cognitive Decline
- 2013
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In: The journals of gerontology. Series A, Biological sciences and medical sciences. - : Oxford University Press (OUP). - 1079-5006 .- 1758-535X. ; 68:2, s. 205-213
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Journal article (peer-reviewed)abstract
- Background. Studies concerning the effect of different types of leisure activities on various cognitive domains are limited. This study tests the hypothesis that mental, physical, and social activities have a domain-specific protection against cognitive decline. Methods. A cohort of a geographically defined population in China was examined in 2003-2005 and followed for an average of 2.4 years. Leisure activities were assessed in 1,463 adults aged 65 years and older without cognitive or physical impairment at baseline, and their cognitive performances were tested at baseline and follow-up examinations. Results. High level of mental activity was related to less decline in global cognition (beta = -.23, p < .01), language (beta = -.11, p < .05), and executive function (beta = -.13, p < .05) in ANCOVA models adjusting for age, gender, education, history of stroke, body mass index, Apolipoprotein E genotype, and baseline cognition. High level of physical activity was related to less decline in episodic memory (beta = -.08, p < .05) and language (beta = -.15, p < .01). High level of social activity was associated with less decline in global cognition (beta = -.11, p < .05). Further, a dose-response pattern was observed: although participants who did not engage in any of the three activities experienced a significant global cognitive decline, those who engaged in any one of the activities maintained their cognition, and those who engaged in two or three activities improved their cognition. The same pattern was observed in men and in women. Conclusions. Leisure activities in old age may protect against cognitive decline for both women and men, and different types of activities seem to benefit different cognitive domains.
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| 154. |
- Wang, Jing, et al.
(author)
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Impact of centennial-scale solar activity reduction on the weakened Asian monsoon event at 9.2 ka BP
- 2023
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In: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 628
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Journal article (peer-reviewed)abstract
- The weakened Asian monsoon event at 9.2 ka has been documented in many proxy-based reconstructions, but its underlying causes are uncertain. In this study, we investigated this event from a regional monsoon perspective by analysing simulations of Holocene transient solar activity forcing using the Community Earth System Model and high-resolution proxies. Our results revealed two separate periods of decreasing precipitation in the western North Pacific (WNP) and South Asian (SA) monsoons from 9.5 to 9.2 ka, each lagging behind two remarkable weakening events (0.38 and 0.21 W m−2) in solar forcing. However, there was no significant change in East Asian summer monsoon precipitation at 9.2 ka based on our experiment. Moisture budget analysis indicated that the dynamic effects term (i.e., anomalous descending motion) figured prominently in decreasing WNP and SA monsoon precipitation. Such a change was affected by an anomalous WNP anticyclone, which was maintained by the ‘wind-evaporation-sea surface temperature’ feedback during the decay phase of the centennial-scale El Niño-like event. The development of centennial El Niño-like conditions was caused by a reduction in solar irradiance. Reduced solar irradiance induced cooling over northern Australia, generating anomalous zonal sea level pressure gradients and westerlies over the tropical Pacific, ultimately resulting in the development of an El Niño-like pattern.
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| 155. |
- Wang, Ke, et al.
(author)
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Experimental Study on the Dynamics of a Thin Liquid Film under Shearing Force
- 2017
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In: Jixie Gongcheng Xuebao/Journal of Mechanical Engineering. - : Chinese Journal of Mechanical Engineering. - 0577-6686. ; 53:24, s. 70-76
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Journal article (peer-reviewed)abstract
- The "scales-separation" phenomenon indicates that high heat-flux boiling and boiling crisis is dominated by micro-hydrodynamics of liquid microlayer on the heater surface. The techniques for liquid film measurement such as acoustic methods, nucleonic techniques, electrical methods, and optical methods are discussed in detail. Accordingly, a confocal optical sensor system is used to detect the dynamics of liquid film sheared by the co-flowing air from above in a horizontal aluminum channel. The impact of the gas shearing on film behaviors is analyzed and the integrity of liquid film is discussed in detail. The results indicate that the liquid film thickness decreases due to the entrainment and shows a linear or nonlinear variation under different flow conditions. Additionally, for a specific surface, the critical film thickness for an integral film is found to have no relation with the gas and liquid flow rates but the fluctuation of the liquid film increases with the increasing gas velocity.
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| 156. |
- Wang, Lei, et al.
(author)
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Photo-healable ion gel with high mechanical property, fatigue resistance and shear resistance using a coumarin group containing diblock copolymer in an ionic liquid
- 2022
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In: European Polymer Journal. - : Elsevier. - 0014-3057 .- 1873-1945. ; 165
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Journal article (peer-reviewed)abstract
- Ion gels, polymer networks swollen with ionic liquid (IL), are ideal materials for application in flexible electronic devices. It remains a challenge to fabricate an ion gel with photo-healing, high mechanical properties, fatigue resistance and shear resistance. Herein, a well-defined diblock copolymer polystyrene-b-poly(methyl acrylate-r-7-(2′-methacryloyloyloxyethoxy)-4-methylcoumarin) (PS-b-P(DMA-r-MAOEMC), brief name: SMM, PS: IL-phobic segment and P(DMA-r-MAOEMC): IL-philic segment) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. For comparison, a random copolymer P(DMA-r-MAOEMC) (MM) also be prepared. In dilute solution, the SMM can form spherical micelles with PS-core surrounded by P(DMA-r-MAOEMC) corona chains in an IL, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfone)amide ([C2mim][NTf2]). In a suitable polymer concentration, the SMM and MM can form ion gels in [C2mim][NTf2] under 365 nm UV light irradiation through photo-dimerization of coumarin groups in corona MM polymer chains of spherical micelles and photo-dimerization of coumarin groups in MM random polymer chains, respectively. Compared with the MM ion gel, the SMM ion gel has high mechanical properties, shear resistance and relatively high fatigue resistance. Under 254 nm UV light irradiation, photo-induced gel to jammed micelles transition for the SMM ion gel and photo-induced gel to sol transition for the MM ion gel occur due to photo-cleavage of dimer in polymer chains. Photo-induced jammed micelles - gel transition for the SMM ion gel and photo-induced sol - gel transition for the MM ion gel are reversible by alternating 365 nm and 254 nm UV light irradiation, whereby photo-healable materials can be fabricated. Compared to the MM ion gel, the SMM ion gel has high photo-healing efficiency. The electrochemical property of the SMM ion gel can be recovered completely after photo-healing.
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| 157. |
- Wang, Xue Jing, et al.
(author)
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Autonomic ganglionic injection of α-synuclein fibrils as a model of pure autonomic failure α-synucleinopathy
- 2020
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1
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Journal article (peer-reviewed)abstract
- α-Synucleinopathies are characterized by autonomic dysfunction and motor impairments. In the pure autonomic failure (PAF), α-synuclein (α-Syn) pathology is confined within the autonomic nervous system with no motor features, but mouse models recapitulating PAF without motor dysfunction are lacking. Here, we show that in TgM83+/− mice, inoculation of α-Syn preformed fibrils (PFFs) into the stellate and celiac ganglia induces spreading of α-Syn pathology only through the autonomic pathway to both the central nervous system (CNS) and the autonomic innervation of peripheral organs bidirectionally. In parallel, the mice develop autonomic dysfunction, featured by orthostatic hypotension, constipation, hypohidrosis and hyposmia, without motor dysfunction. Thus, we have generated a mouse model of pure autonomic dysfunction caused by α-Syn pathology. This model may help define the mechanistic link between transmission of pathological α-Syn and the cardinal features of autonomic dysfunction in α-synucleinopathy.
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| 158. |
- Wang, Yafei, et al.
(author)
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A Data-Driven Scheme for Quantitative Analysis of Texture
- 2020
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In: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 51:2, s. 940-950
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Journal article (peer-reviewed)abstract
- Texture is the orientation distribution of crystallites in polycrystalline materials. Given the discrete orientations, Schaeben suggested to adopt statistics for quantitative analysis of texture from discrete orientations, and he also conceived a clustering algorithm to facilitate the applications of statistical methods (H. Schaeben, J Appl Crystal 26:112-121, 1993). This data-driven scheme becomes more urgent and more necessary for the oncoming fourth paradigm: data-intensive scientific discovery, which follows after experimental science, theoretical science, and computational science paradigm. This research adopts a density-based clustering algorithm, DBSCAN, to process the orientation data from an austenitic stainless steel 316 L sample fabricated by selective laser melting. It is validated that the algorithm can robustly identify the orientation cluster (or texture component or preferred orientation). The statistical methods can successfully quantify the features of the identified orientation cluster with quantified uncertainty (statistical significance), which is often lacked in the general method of orientation distribution function. It is believed that this data-driven scheme can be applied to the many aspects of texture analysis.
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| 159. |
- Wang, Yafei, et al.
(author)
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Band-Like Distribution of Grains in Selective Laser Melting Track Under Keyhole Mode
- 2019
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In: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer Science and Business Media LLC. - 1073-5615 .- 1543-1916. ; 50:2, s. 1035-1041
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Journal article (peer-reviewed)abstract
- Grain structure in the melt pool under keyhole mode is complex due to complicated solidified conditions, especially in consideration of the intense fluid flow. This paper aims to clarify grain structure and grain growth mechanism in melt pool under keyhole mode in selective laser melting. The microstructure from transverse cross section and longitudinal cross section near the centerline of 316L single tracks was characterized. In the longitudinal cross section, band-like grain structure formed. It is found that fluid flow can refine the grains, and large columnar grains grow towards crystallographic < 110 > direction.
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| 160. |
- Wang, Yafei, et al.
(author)
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Construction of Cellular Substructure in Laser Powder Bed Fusion
- 2019
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In: Metals. - : MDPI AG. - 2075-4701.
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Journal article (peer-reviewed)abstract
- Cellular substructure has been widely observed in the sample fabricated by laser powder bed fusion, while its growth direction and the crystallographic orientation have seldom been studied. This research tries to build a general model to construct the substructure from its two-dimensional morphology. All the three Bunge Euler angles to specify a unique growth direction are determined, and the crystallographic orientation corresponding to the growth direction is also obtained. Based on the crystallographic orientation, the substructure in the single track of austenitic stainless steel 316L is distinguished between the cell-like dendrite and the cell. It is found that, with the increase of scanning velocity, the substructure transits from cell-like dendrite to cell. When the power is 200 W, the critical growth rate of the transition in the single track can be around 0.31 ms(-1).
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