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Fracture characteristics and in-situ damage mechanism of PIP-c/Sic composites to various temperatures and loading velocities

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ENGINEERING FRAcTURE MEcHANIcS 2023年第1期286卷

作者： Zhao, Guicheng Jiang, Zhonghe Qu, Zhaoliang Xi, Huifeng Ai, Shigang Beijing Inst Technol Inst Adv Struct Technol Beijing 100081 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

c/Sic composites prepared by polymer infiltration and pyrolysis (PIP) are among the most promising materials for application in ultrahigh-temperature conditions. However, the mechan-ical properties and damage mechanisms of PIP-c/Sic composites at different loading velocities and temperatures have not been systematically studied. In this study, in-plane compression, bending, and in-plane shear experiments were systematically performed at different loading ve-locities and temperatures in an inert atmosphere. The ultimate strengths of the PIP-c/Sic com-posite were determined under different conditions, and the failure modes were revealed. In addition, in-situ X-ray microtomography tension experiments were conducted to study the failure mechanism of the PIP-c/Sic composite. The results showed that the ultimate strengths were considerably affected by the temperature and loading velocity, and the failure modes were dependent on experimental types. The fracture location of the PIP-c/Sic composite is affected by the defect. And the direction of crack propagation is toward the existing cracks and voids.

关键词： c Sic composites High temperature Mechanical properties In -situ tension Failure mechanism

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Boosting sodium-ion storage performance by tailoring intragranular porous WS2/c nanocomposites anode

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APPLIED SURFAcE ScIENcE 2023年第1期616卷

作者： Liu, cheng Zou, Jiaming Yang, Jinzhou Ren, Tieqiang Wu, Hongda Yang, Zhanxu Liaoning Petrochem Univ Sch Petrochem Engn Fushun 113001 Peoples R China Huaiyin Normal Univ Jiangsu Key Lab Chem Low Dimens Mat Huaian 223300 Jiangsu Peoples R China

Two-dimensional layered semiconducting materials, such as tungsten disulfide, have attracted significant research interest over the past few decades. With rational optimization of their chemical constitutions and regulation of electronic configurations, these materials can achieve commercial viability. Herein, the WS2/c hybrid was constructed by organic amine intercalation and in-situ pyrolysis. Intraparticle porous WS2/c was successfully synthesized by dissolving and etching. The specific surface area of the obtained WS2/c was significantly enhanced on the removal of WO3 through alkali etching, which facilitated the Na-insertion/ extraction. Therefore, the obtained porous WS2/c composite delivered a high reversible capacity and improved cycle stability with 346.3 mAh g-1 over 80 cycles at 100 mA g-1. This work proposes an intragranular porous WS2/c composite electrode design which shows a superior sodium storage performance, improved electronic conductivity and enhanced reversible specific capacity. It is expected to present a novel insight for designing other high-capacity sodium-ion and other alkaline ion battery electrode materials.

关键词： Heterostructures Porous WS 2 c Sodium-ion batteries Etching

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Effects of grazing on c:N:P stoichiometry attenuate from soils to plants and insect herbivores in a semi-arid grassland

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OEcOLOGIA 2021年第3期195卷 785-795页

作者： Hassan, Nazim Li, Xiaofei Wang, Jianyong Zhu, Hui Nummi, Petri Wang, Deli Finke, Deborah Zhong, Zhiwei Northeast Normal Univ Sch Environm Key Lab Wetland Ecol & Vegetat Restorat Key Lab Vegetat EcolInst Grassland Sci Changchun 130024 Jilin Peoples R China Jilin Agr Univ Key Lab Sustainable Utilizat Soil Resources Commo Coll Resources & Environm Sci Changchun 130118 Jilin Peoples R China Univ Helsinki Dept Forest Sci Wetland Ecol Grp POB 27 Helsinki 00014 Finland Univ Missouri Div Plant Sci Columbia MO 65211 USA

Understanding the processing of limiting nutrients among organisms is an important goal of community ecology. Less known is how human disturbances may alter the stoichiometric patterns among organisms from different trophic levels within communities. Here, we investigated how livestock grazing affects the c:N:P ecological stoichiometry of soils, plants (Leymus chinensis), and grasshoppers (Euchorthippus spp.) in a semi-arid grassland in northeastern china. We found that grazing significantly enhanced soil available N and leaf N content of the dominant L. chinensis grass by 15% and 20%, respectively. Grazing also reduced (soluble) c:N of L. chinensis leaves by 22%. However, grazing did not affect total c, N, or P contents nor their ratios in Euchorthippus grasshoppers. Our results reveal that the effects of grazing disturbances on elemental composition attenuated from lower to higher trophic levels. These findings support the theory that organisms from higher trophic levels have relatively stronger stoichiometric homeostasis compared to those from lower trophic levels. Moreover, grasshopper abundance dropped by 66% in the grazed areas, and they reduced the feeding time on their host L. chinensis grass by 43%, presumably to limit the intake of excess nitrogen from host plants. The energetic costs associated with the maintenance of elemental homeostasis likely reduced grasshopper individual performance and population abundance in the grazed areas. A comprehensive investigation of stoichiometric properties of organisms across trophic levels may enable a better understanding of the nature of species interactions, and facilitate predictions of the consequences of future environmental changes for a community organization.

关键词： Stoichiometric homeostasis Population dynamics c N P Plant– insect interactions

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Hierarchical dumbbell-like Fe3O4/c electrode for the supercapacitor

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MATERIALS LETTERS 2023年 331卷

作者： Lan, Jian Hou, Hongying Liu, Xianxi Yu, Xiaohua Rong, Ju chen, Fangshu Kunming Univ Sci & Technol Fac Mat Sci & Engn Kunming 650093 Peoples R China Kunming Univ Sci & Technol Fac Mech & Elect Engn Kunming 650093 Peoples R China Kunming Univ Sci & Technol Law Sch Kunming 650093 Peoples R China

Hierarchical dumbbell-like Fe3O4/c powder was synthesized for the supercapacitor electrode by the sol-vothermal reaction and subsequent calcination. Resultantly, the reversible capacitances of the three-electrode and symmetric two-electrode capacitors were 490.2 F/g and 210.2 F/g, respectively, higher than those in lit-eratures, possibly due to the unique hierarchical dumbbell-like structure with the easier access and penetration of the electrolyte to the electrode. Moreover, the symmetric Fe3O4/c two-electrode system exhibited the remark-able cycle stability at 5.0 A/g and high energy density of 34.3 Wh/kg at 1003.9 W/kg, indicating high feasibility for the application in high-performance supercapacitor.

关键词： Hierarchical dumbbell c Nanoparticles Supercapacitor Energy storage and conversion

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Machine Learning Model to Predict Ventilator Associated Pneumonia in patients with Traumatic Brain Injury: The c.5 Decision Tree Approach

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BRAIN INJURY 2021年第9期35卷 1095-1102页

作者： Abujaber, Ahmad Fadlalla, Adam Gammoh, Diala Al-Thani, Hassan El-Menyar, Ayman Hamad Med Corp Nursing Doha Qatar Qatar Univ Management Informat Syst Business & Econ Fac Doha Qatar Univ Cent Florida Ind Engn Orlando FL USA Hamad Med Corp Dept Surg Trauma Surg Doha Qatar Hamad Med Corp Dept Surg Clin Res Trauma Surg Doha Qatar Weill Cornell Med Coll Dept Clin Med Doha Qatar

Background There is paucity in the literature to predict the occurrence of Ventilator Associated Pneumonia (VAP) in patients with Traumatic Brain Injury (TBI). We aimed to build a c.5. Decision Tree (c.5 DT) machine learning model to predict VAP in patients with moderate to severe TBI. Methods This was a retrospective study including all adult patients who were hospitalized with TBI plus head abbreviated injury scale (AIS) >= 3 and were mechanically ventilated in a level 1 trauma center between 2014 and 2019. Results A total of 772 eligible patients were enrolled, of them 169 had VAP (22%). The c.5 DT model achieved moderate performance with 83.5% accuracy, 80.5% area under the curve, 71% precision, 86% negative predictive value, 43% sensitivity, 95% specificity and 54% F-score. Out of 24 predictors, c.5 DT identified 5 variables predicting occurrence of VAP post-moderate to severe TBI (Time from injury to emergency department arrival, blood transfusion during resuscitation, comorbidities, Injury Severity Score and pneumothorax). conclusions This study could serve as baseline for the quest of predicting VAP in patients with TBI through the utilization of c.5. DT machine learning approach. This model helps provide timely decision support to caregivers to improve patient's outcomes.

关键词： Machine learning ventilator-associated pneumonia traumatic brain injury c 5 decision tree model

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Type specimen sequencing, multilocus analyses, and species delimitation methods recognize the cosmopolitan corallina berteroi and establish the northern Japanese c. yendoi sp. nov. (corallinaceae, Rhodophyta)

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JOURNAL OF PHYcOLOGY 2021年第5期57卷 1659-1672页

作者： calderon, Martha S. Bustamante, Danilo E. Gabrielson, Paul W. Martone, Patrick T. Hind, Katharine R. Schipper, Soren R. Mansilla, Andres Univ Magallanes Lab Ecosistemas Marinos Antarticos & Subantartico Punta Arenas Chile Inst Ecol & Biodiversidad IEB Santiago Chile Univ Nacl Toribio Rodriguez Mendoza Inst Invest Desarrollo Sustentable Ceja de Selva Chachapoyas Peru Univ Nacl Toribio Rodriguez Mendoza Dept Civil & Environm Engn FICIAM Chachapoyas Peru Univ N Carolina Biol Dept & Herbarium Coker Hall CB 3280 Chapel Hill NC 27599 USA Univ British Columbia Bot Dept Vancouver BC V6T 1Z4 Canada Univ British Columbia Biodivers Res Ctr Vancouver BC V6T 1Z4 Canada Univ Victoria Dept Biol POB 1700 Stn CSC Victoria BC V8W 2Y2 Canada

A partial rbcL sequence of the lectotype specimen of corallina berteroi shows that it is the earliest available name for c. ferreyrae. Multilocus species delimitation analyses (ABGD, SPN, GMYc, bPTP, and BPP) using independent or concatenated cOI, psbA, and rbcL sequences recognized one, two, or three species in this complex, but only with weak support for each species hypothesis. conservatively, we recognize a single worldwide species in this complex of what appears to be multiple, evolving populations. Included in this species, besides c. ferreyrae, are c. caespitosa, the morphologically distinct c. melobesioides, and, based on a partial rbcL sequence of the holotype specimen, c. pinnatifolia. corallina berteroi, not c. officinalis, is the cosmopolitan temperate species found thus far in the NE Atlantic, Mediterranean Sea, warm temperate NW Atlantic and NE Pacific, cold temperate SW Atlantic (Falkland Islands), cold and warm temperate SE Pacific, NW Pacific and southern Australia. Also proposed is c. yendoi sp. nov. from Hokkaido, Japan, which was recognized as distinct by 10 of the 13 species discrimination analyses, including the multilocus BPP.

关键词： coralline algae corallina caespitosa c ferreyrae c melobesioides c pinnatifolia multilocus phylogeny new species species boundaries

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Effects of pyrocarbon interphase on microstructure and properties of c/SiBcN composites

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MATERIALS RESEARcH EXPRESS 2023年第2期10卷 025603页

作者： Jia, Yan cheng, Haifeng chen, Si'an Natl Univ Def Technol Coll Aerosp Sci & Engn Sci & Technol Adv Ceram Fibers & Composites Lab Changsha 410073 Peoples R China

c/SiBcN composites are expected to be widely used in aerospace applications because of their excellent high-temperature stability. However, the interfacial reactions have significantly limited their practical application. A pyrocarbon (Pyc) interphase can improve the interfacial reactions of c/SiBcN composites. In this study, Pyc interphases of different thicknesses (0.1 mu m, 0.25 mu m, and 0.5 mu m) were introduced via chemical vapor deposition (cVD) process. The interface bonding of c/SiBcN composites with 0.1 mu m and 0.25 mu m thick interphases was relatively weak and the composites with 0.5 mu m interphase exhibited strong interface bonding. After heat treatment at 1600 degrees c, the mechanical properties of the c/SiBcN composites with the 0.5 mu m thick interphase was maintained at 131 MPa, and it was maintained at 105 MPa even after heat treatment at 1900 degrees c, indicating their excellent high-temperature mechanical properties. In short, 0.5 mu m thick Pyc interphase can effectively improve the interfacial reaction of the c/SiBcN composites, facilitating their application in high-temperature environments.

关键词： ceramic matrix composites c SiBcN composite chemical vapor deposition mechanical properties

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Preparation of Hollow Tubular TiO2/c Photocatalyst and Study on Photocatalytic Degradation Process and Mechanism of Dyes

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JOURNAL OF NATURAL FIBERS 2023年第1期20卷 56-70页

作者： Wang Shuhua Islam, Tohid Bao, Zhanxia Taiyuan Univ Technol Coll Text Engn 209 Daxue St Yuci 030600 Shanxi Peoples R China

Hollow tubular structure TiO2/c photocatalyst was prepared by carbonization at 400celcius with cotton fabric as initial carrier and tetrabutyltitanate as precursor. The structure of the samples was characterized by SEM and XRD. The results show that anatase crystal TiO2 with good crystallization is formed, TiO2 was uniformly distributed on the surface of the hollow tubular carbon material. The photocatalytic degradation performance was measured by using the methylene blue as the target dyes. When the dosage of TiO2/c was 1.7 g/L, the degradation rate of methylene blue solution was high up to 97.5%. The effective degradation of dyes was realized by using the strong adsorption property of hollow carbon materials and the high photocatalytic activity of anatase titanium dioxide. Due to the repeated adsorption of carbon materials to dyes and the continuous degradation of titanium dioxide to dyes, TiO2/c photocatalyst could be regenerated in situ.

关键词： cotton fabric carbonization TiO2 c dyes degradation photocatalytic activity

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Stability of c:N:P Stoichiometry in the Plant-Soil continuum along Age classes in Natural Pinus tabuliformis carr. Forests of the Eastern Loess Plateau, china

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FORESTS 2023年第1期14卷 44页

作者： chen, Haoning Xiang, Yun Yao, Zhixia Zhang, Qiang Li, Hua cheng, Man Shanxi Univ Inst Loess Plateau Coll Environm &Resource Sci Taiyuan 030006 Peoples R China Shanxi Agr Univ Coll Resources & Environm Jinzhong 030801 Peoples R China

Ecological stoichiometry is useful for revealing the biogeochemical characteristics of flows of nutrients and energy between plant and soil, as well as the important implications behind these ecological phenomena. However, the ecological stoichiometric linkages among leaf, litter, soil, and enzymes in the natural forests of the Loess Plateau remain largely unknown. Here, leaf, litter, and soil samples were collected from four age classes of natural Pinus tabuliformis carr. (P. tabuliformis) to explore the deep linkages among these components. We measured the total carbon (c), total nitrogen (N), and total phosphorus (P) concentrations of leaf and litter, as well as the concentrations of soil organic c, total N, total P, nitrate N, ammonium N, available P, and the activities of beta-1,4-glucosidase (a c-acquiring enzyme), beta-1,4-N-acetylglucosidase (an N-acquiring enzyme), and alkaline phosphatase (a P-acquiring enzyme) in the topsoil (0-20 cm). The average leaf N:P was 6.9 indicated the growth of P. tabuliformis was constrained by N according to the relative resorption theory of nutrient limitation. The c:N, c:P, and N:P ratios in leaf, litter, and soil and the enzyme activity were not significantly different among age classes (p > 0.05). Litter c:N (43.3) was closer to the ratio of leaf c:N (48.8), whereas the litter c:P (257.7) was obviously lower than the ratio of leaf c:P (338.15). We calculated the stoichiometric homeostasis index (1/H) of leaf responses to soil elements and enzyme activities and found that the relationship between leaf c:P and soil c:P was homeostatic (p < 0.05), whereas the remaining indices showed the leaf stoichiometries were strictly homeostatic (p > 0.05). correlation analysis showed both litter c:P and N:P were positively correlated with leaf and soil c:P, while the stoichiometric ratios of soil elements and enzymes were obviously irrelevant with leaf stoichiometries (p > 0.05). Partial least squares path modeling indicated that litter

关键词： c N P stoichiometry natural Pinus tabuliformis carr plant-soil continuum age classes

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Effect of mullite content on microstructure and ablation behavior of mullite modified c/c-Sic-Hfc composites

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cORROSION ScIENcE 2023年第1期222卷

作者： Tan, Qing Jiao, Xiaoyang He, Qinchuan Wang, Yiqun Yin, Xuemin Chengdu Univ Technol Coll Mat & Chem & Chem Engn Chengdu 610059 Peoples R China Northwestern Polytech Univ Sch Mat Sci & Engn Xian 710072 Peoples R China

Mullite modified c/c-Sic-Hfc composites were prepared via precursor infiltration and pyrolysis (PIP). The effects of mullite modification with different contents on the composition, microstructure, and ablation behavior of the composites were investigated. Results showed that inadequate and excessive mullite limited the improvement of the ablation resistance. At 8.88 wt% mullite, the composites exhibited relatively good ablation resistance with mass and linear ablation rates of 0.44 mg/s & BULL;cm2 and 6.39 & mu;m/s. The addition of moderate mullite content promoted the formation of a dense Hf-Si-O multiphase oxide layer on the ablated surface without causing an excessive increase in surface temperature.

关键词： c c-Sic-Hfc composites Mullite Precursor infiltration and pyrolysis Microstructure Ablation behavior

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