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Effects of Void Defects on Fracture Features and Tensile Strength of c/Sic composites: an Image-based FEM Study

APPLIED cOMPOSITE MATERIALS 2022年第3期29卷 1021-1039页

作者： Li, Qiubo chen, Yihui chen, Yanfei Ai, Shigang Fang, Daining Beijing Inst Technol Inst Adv Struct Technol Beijing 100081 Peoples R China

Manufacturing defects in ceramic matrix composites (cMcs), such as voids, microcracks, etc., significantly affect the damage events and strength of the materials. This study aims to reveal the effect of void defects on the failure behavior and tensile strength of a plain-woven c/Sic composite. The mesoscopic architectures of the c/Sic composites are tested by micro-computed tomography. Based on the mu-cT images of the material, finite element models (IB-FEM) of the c/Sic composite are established with different void volume fractions and different void geometry. The tensile strength and fracture features of the c/Sic composites are calculated by using the IB-FEM. The effects of void volume fraction and geometry on failure behaviors and tensile strength of the c/Sic composites are investigated and discussed. This study is of great significance for further understanding the influence of defects on the mechanical behavior of cMcs.

关键词： Image-based finite element method c Sic composite Void defect Tensile strength

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Polystyrene nanoparticles cause dynamic alteration in mitochondrial unfolded protein response from parents to the offspring in c. elegans

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cHEMOSPHERE 2022年第Part1期308卷 136154页

作者： Xu, Ruoran Hua, Xin Rui, Qi Wang, Dayong Nanjing Agr Univ Coll Life Sci Nanjing 210095 Peoples R China Southeast Univ Med Sch Nanjing 210009 Peoples R China

The mitochondrial unfolded protein response (mt UPR) is important for organisms against the toxicity from toxicants and stresses. Polystyrene nanoparticle (PS-NP), one of the emerging pollutants, has aroused increasing concern for its toxicity in the offspring. Nevertheless, the molecular basis for this transgenerational toxicity remains largely unclear. In this study, the role of mt UPR in the induction of transgenerational toxicity was determined in caenorhabditis elegans (c. elegans) after parental exposure to PS-NP. After exposure to PS-NP (1-100 mu g/L), the suppression in mt UPR showed the concentration-dependent in nematodes from P0 genera-tion (P0-G) to F2-G. Moreover, the decreased expression of genes required for controlling mt UPR (atfs-1, dve-1, and ubl-5 genes) were observed from P0-G to F2-G after exposure to PS-NP (1 mu g/L). The adverse effects on locomotion and reproductive capacity were more severe over generations in nematodes with RNAi of these three genes, indicating that these genes were involved in controlling transgenerational toxicity. After parental PS-NP exposure (1 mu g/L), the mt UPR was significantly inhibited by RNAi of atfs-1, dve-1, and ubl-5, indicating the association between the transgenerational PS-NP toxicity and mt UPR suppression. Additionally, during the transgenerational process, RNAi of atfs-1, dve-1, and ubl-5 enhanced the PS-NP toxicity by suppressing mt UPR, while RNAi of daf-2 encoding an insulin receptor inhibited the PS-NP toxicity by increasing mt UPR. Therefore, our data highlighted the role of inhibition in mt UPR in mediating the transgenerational nanoplastic toxicity in nematodes.

关键词： Nanoplastic mt UPR Transgenerational response c elegans

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Experimental Study on Surface Quality in Ultrasonic-assisted Grinding of c/c-Zrc-cu composites Fabricated with Different Preforms

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APPLIED cOMPOSITE MATERIALS 2022年第5期29卷 1747-1769页

作者： Duan, Zhenyan chen, Tao Li, Hongbo Zhang, Yiwen Li, Haotian Wuhan Univ Technol Sch Mech & Elect Engn Wuhan 430070 Peoples R China

c/c-Zrc-cu composite is a new ablation-resistant material with wide application prospects in the aerospace field. The quality of its surface affects the ablative corrosion resistance of the material. Ultrasonic-assisted grinding (UAG) is an effective processing method for hard and brittle materials. Therefore, it is meaningful work to investigate the material removal mechanism of c/c-Zrc-cu composites in UAG. In this paper, UAG was applied to the processing of c/c-Zrc-cu composites fabricated with different preforms which include needle-punched preform, pierced preform and felt-based preform. The effects of process parameters on the surface quality of c/c-Zrc-cu composites fabricated with different preforms were investigated via single-factor tests. The machining tools used for the tests were the electroplated diamond grinding wheels and the ultrasonic vibration direction was parallel to the processed surface. The results indicate that the preforms determine the surface quality of the c/c-Zrc-cu composites. The surface quality of c/c-Zrc-cu composites fabricated with felt-based preform is the best because of the lower carbon fiber content. The removal of carbon fibers is mainly by brittle fracture, interface debonding and pull-out, and the removal of hard Zrc particles is mainly by brittle fracture while the cu-rich area is removed in a plastic manner. In addition, when the ultrasonic amplitude is in the range of 4-9 mu m, the hard Zrc particles are more easily broken thus deteriorating the surface quality.

关键词： c c-Zrc-cu composites Ultrasound-assisted grinding (UAG) The material removal mechanism Surface roughness

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Hydrogenation of cyclohexene catalyzed by nanoporous SPE-PtNi/c membrane electrode

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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2022年第4期47卷 2500-2510页

作者： Yang, Bin Fang, Liudang Zan, Linhan cai, Jiaxian Feng, Yunhao Li, Xudong Kunming Univ Sci & Technol Fac Mat Sci & Engn Kunming 650093 Yunnan Peoples R China Yunnan Phinergy Chuang Neng Met Air Battery Co Lt Kunming 650106 Yunnan Peoples R China

Implementing large-scale synthesis of nanoporous PtNi/c catalysts for hydrogenation processes of unsaturated organic compounds under atmospheric pressure at temperatures below 100 degrees c is an urgent task. In this paper, a nanoporous SPE-PtNi/c membrane electrode is prepared by ion beam sputtering, ultrasonic-assisted electrochemical dealloying, and hotpressing. Special attention is paid to the analysis of the electrochemical properties, phase structure, surface morphology, active constituent distribution, and catalytic efficiency for cyclohexene hydrogenation of the produced electrode in comparison with those of commercial Pt/c catalysts. The results show that the ultrasonic-assisted electrochemical etching temperature exerts the most significant effect on the catalytic activity of the catalyst under consideration. In particular, the treatment of PtNi/c in 0.7 mol/L HclO4 for 1.5 h at the optimized temperature of 50 degrees c enables one to increase the catalytic activity by 25.20% at decreasing the Pt-loading content by 88.85% compared with commercial Pt/c. Furthermore, the nanoporous structure of the PtNi/c surface allows the binding energy of Pt 4f7/2 to be reduced by 0.23 eV due to the Ni loss and the crystal plane shrinkage from NiPt, which enhances the compressive strain of the lattice structure of exposed Pt and increases the number of active sites. Finally, the use of a nanoporous SPE-PtNi/c membrane electrode could increase the yield of cyclohexene during the hydrogenation reaction by 179% at simultaneously improving the current efficiency by 69%. (c) 2021 Hydrogen Energy Publications LLc. Published by Elsevier Ltd. All rights reserved.

关键词： Nanoporous PtNi c Hydrogenation of unsaturated organic compounds Electrocatalysis IBS Dealloying

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The Subcultural Imagination: critically Negotiating the co-Production of 'Subcultural Subjects' through the Lens of c. Wright Mills

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SOcIOLOGIcAL RESEARcH ONLINE 2023年第1期28卷 58-72页

作者： Blackman, Shane Kempson, Michelle Canterbury Christ Church Univ Cultural Studies Canterbury Kent England Solihull Coll Solihull W Midlands England

This article interrogates the following two concepts: the 'subcultural imagination' and the 'subcultural subject'. We explore debates surrounding the ways in which interactions between the researcher and participant produce knowledge, in order to further establish the critical contribution of subculture within sociology. This article draws upon the notion of critique and ideas of c. Wright Mills (1959) in order to demonstrate the potential of new forms of 'imagination' within subcultures research. We seek to show through ethnographic examples how researchers and participants can be engaged in co-production of fieldwork, analysis and writing within research at different levels of engagement. The article will cover four areas, all focused on placing 'imagination' at the centre of subcultures research: first, it critiques the postmodern post-subcultural position within youth cultural studies;second, it defines the subcultural imagination and third, it explores specific empirical examples of subcultural subjects and, finally, we shall address the potential for micro co-production.

关键词： co-production c W Mills ethnography sociological imagination subculture youth culture

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c. Wright Mills in copenhagen: collaboration, Politics, and the Making of 'The Sociological Imagination

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AMERIcAN SOcIOLOGIST 2023年第3期54卷 399-419页

作者： Petersen, Klaus Univ Southern Danish Ctr Welf Studies Odense Denmark Univ Southern Danish Inst Adv Study Odense Denmark

American sociologist c. Wright Mills is one of the most important and controversial sociologists of the post-war period. Of Mills' works, one book stands out: The Sociological Imagination, published by Oxford University Press in 1959. Little known is that Mills drafted his book during a 12-month Fulbright visit to University of copenhagen 1956-1957. In the rich biographical literature on Mills this is mentioned only in the passing, or not at all. Based on hitherto unused archival material, this paper offers the first detailed account of his copenhagen-visit during the cold War. Bringing together this bulk of new historical traces sheds new light on the year Mills himself referred to as a "pivotal moment." These 12 months in copenhagen, amid the cold War, was formative for Mills in two ways: First, copenhagen was an entrepot to European center-left thinking both east and west of the Iron curtain. Second, the stay in copenhagen offered a 'space of selfhood', allowing Mills a necessary respite to develop his critical thinking. He did so in close cooperation with like-minded colleagues in copenhagen. In the mid-1950s, the discipline was in the making in Denmark, and the visit of a prominent US scholar like Mills offered opportunities for Danish sociologist to further the discipline - and their standing within the discipline.

关键词： c Wright Mills Sociological imagination History of sociology cold war Denmark

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High Performance Nitrogen-Doped Si/c as the Anode Material of Lithium-Ion Batteries

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RUSSIAN JOURNAL OF ELEcTROcHEMISTRY 2022年第2期58卷 136-142页

作者： Ying, Jin Yuan, An Jin, Xin Tan, Lian Tang, Hao Sun, Runguang Nanchang Univ Sch Mat Sci & Engn Nanchang 330031 Jiangxi Peoples R China

The large-scale synthesis of electrode materials in the field of lithium ion batteries (LIBs) is highly depending on the synthetic technique. In this paper, we developed a facile route to synthesize N-doped carbon coated silicon (Si/c) materials. In that, commercial Si flakes were ball-milled with asphalt as a carbon source and dopamine as a nitrogen source, followed by carbonization in inert atmorsphere to obtain N-doped Si/c materials. As a result, the N-doped Si/c material achieved better cycling stability and slightly higher initial charging capacity of 2265.1 mA h g(-1) than that of undoped Si/c at the current density of 200 mA g(-1). After 50 cycles, a charge capacity of 1359.1 mA h g(-1) was retained, representing 36.7% capacity enhancement compared with that of the Si/c sample (994.4 mA h g(-1)). Moreover, the rate performance of the Si-based material was also effectively improved by the N-doping. It can be explained that the N-doped carbon layer can facilitate the Li-ions diffusion. Overall, the N-doped Si/c material obtained by a simple technique is promising for the high energy density LIBs application as the anode material.

关键词： lithium-ion battery anode material N-doping carbon coating Si c

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Braking behaviours of c/c-Sic mated with iron/copper-based PM in dry, wet and salt fog conditions

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cERAMIcS INTERNATIONAL 2022年第3期48卷 3261-3273页

作者： Tang, Huixian Li, Pengtao Li, Zhuan Li, Jinwei Zhao, Jiong Xu, Yang Li, Yang Xiao, Peng Cent South Univ State Key Lab Powder Met Changsha 410083 Peoples R China Cent South Univ Natl Key Lab Sci & Technol Natl Def High Strength Changsha 410083 Peoples R China

c/c-Sic composites have enormous potential as a new generation of brake materials. It is worth studying the friction and wear behaviours of these materials in special environments to ensure the safe and effective braking of trains in practical applications. In this study, the braking behaviours and wear mechanisms of c/c-Sic mating with iron/copper-based PM in dry, wet and salt fog conditions are compared in detail. The results show that the coefficient of friction (cOF) in the wet condition is reduced by 14.13% compared with that under the dry condition. The cOF value of the first braking under salt fog condition is increased by 12.27% and 30.75% compared to the dry and wet conditions, respectively. Additionally, the tail warping phenomenon of the braking curve disappears in wet condition, which is attributed to the weak adhesion of friction interfaces and the lubrication of the water film. The main wear mechanisms of c/c-Sic mating with iron/copper-based PM under dry condition are adhesive, fatigue and oxidation wear. However, the dominant wear in wet condition is abrasive wear. The cooling and lubrication of water reduce the tendency of thermal stress, and weaken adhesive and fatigue wear. Furthermore, salt fog can accelerate the corrosion of alloy friction film, leading to the damage of friction film. Meanwhile, the third body particles formed in salt fog condition participate in the braking process. The wear mechanisms in salt fog condition are dominated by abrasive and delamination wear.

关键词： c c -Sic Iron copper-based PM Braking conditions Braking behaviours Wear mechanisms

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characterization of metabolites and biomarkers for the probiotic effects of clostridium cochlearium on high-fat diet-induced obese c57BL/6 mice

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EUROPEAN JOURNAL OF NUTRITION 2022年第4期61卷 2217-2229页

作者： Yang, Fei Zhu, Wenjun Edirisuriya, Paba Ai, Qing Nie, Kai Ji, Xiangming Zhou, Kequan Wayne State Univ Dept Nutr & Food Sci Detroit MI 48202 USA Georgia State Univ Byrdine F Lewis Coll Nursing & Hlth Profess Atlanta GA 30303 USA

Purpose Probiotic species of butyrate producers have been investigated for the potential in preventing and treating obesity and overweight. However, clostridium cochlearium has not been linked with any health benefits. We hypothesized that c. cochlearium could be a promising new probiotic with health benefits in improving body weight control and insulin sensitivity. Methods Productions of short-chain fatty acids (ScFAs) were characterized for c. cochlearium by NMR and Gc-MS analyses. Probiotic effects of c. cochlearium were evaluated through diet-induced obese (DIO) c57BL/6 mice. The influence of c. cochlearium administration on gut ScFAs was measured using Gc-MS. Lc-MS-based untargeted metabolomic profiling and multivariate analysis were used to assess the serum metabolic alteration, identify biomarkers and pathways in response to the c. cochlearium administration. Results After 17 weeks of diet intervention, body weight gain of cc group (fed with a high-fat diet supplemented with c. cochlearium) showed a 21.86% reduction from the high-fat diet (HF) control group (P < 0.001), which was specifically reflected on the significantly lowered fat mass (cc vs HF, 17.19 g vs 22.86 g, P < 0.0001) and fat percentage (cc vs HF, 41.25% vs 47.10%, P < 0.0001), and increased lean percentage (cc vs HF, 46.63% vs 43.72%, P < 0.05). c. cochlearium administration significantly reduced fasting blood glucose from week 8 (P < 0.05 or 0.01), and eventually improved insulin sensitivity (HOMA-IR, cc vs HF, 63.77 vs 143.13, P < 0.05). Overall lowered levels of ScFAs were observed in the gut content of cc group. Metabolomic analysis enabled the identification of 53 discriminatory metabolites and 24 altered pathways between cc and HF groups. In particularly, most of the pathway-matched metabolites showed positive correlations with body weight, which included glutamate, phenylalanine, ornithine, Pcs, LPcs, Accas, proline, 5,6-dihydrouracil, pyroglutamic acid, and 1-pyrroline-4-hydroxy-2-carbo

关键词： c cochlearium Body weight control Insulin sensitivity Metabolomic analysis High-fat diet-induced obese c57BL 6 mice

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cross-sensor comparison of Satellite Products Sentinel-2 and Gaofen-1B/c for Northern Taiga Forests

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IZVESTIYA ATMOSPHERIc AND OcEANIc PHYSIcS 2022年第12期58卷 1652-1663页

作者： cherepanova, E. V. Feoktistova, N. V. AEROCOSMOS Res Inst Aerosp Monitoring Moscow Russia

This study presents the results of the validation of information products on surface reflectance and NDVI, taking into account land cover types, obtained from satellite data of the chinese PMS GF-1 sensor and the reference data of the European sensor MSI Sentinel-2 (ESA) using image cross validation method. Based on the analysis, a high correlation of the target GF-1 information products and reference Sentinel-2 information products was revealed. The resulting regression coefficients can be used with a high degree of reliability when conducting a complex analysis of satellite data to recalculate the values obtained by the PMS sensor into the corresponding values of the MSI sensor, taking into account the camera of a specific satellite (GF-1c or GF-1B).

关键词： remote sensing data validation Gaofen-1B c surface reflectance NDVI land cover

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