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The Effect of Branching Structure on the Properties of Entangled or Non-covalently Crosslinked Polyisoprene

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Chinese Journal of Polymer Science 2021年第1期39卷 113-121,I0008页

作者： Mo-Kun Chen Rong Zhang Mao-Zhu Tang Guang-Su Huang yun-Xiang xu College of Polymer Science&Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China

The branching structures in natural rubber(NR) were believed to be critical for its superior mechanical properties. However, it is challenging to unravel the branching structure-function relationship of NR due to the complexity of the system. Herein, polyisoprene-(polyisoprene-g-polylactide)(PI-PLA) as model compound containing branching structure was designed and synthesized, which can improve the modulus, strength and viscoelasticity activation energy compared to those of the pristine polyisoprene(PI). The reason is that the branching structure contributes to the entanglement between polyisoprene chains. In order to probe the effect of branching structure on noncovalently crosslinked system, the polyisoprene block of PI-PLA was epoxidized and mixed with Fe3+ ions to introduce coordination bonds. Compared with the linear counterpart, the branching structure obviously enhanced activation energy of coordinated polyisoprenes, remarkably improving the mechanical properies of elastomer.

关键词： Natural rubber Branching structure Noncovalent interaction Polyisoprene

Implementation of high-fidelity neutronics and thermal–hydraulic coupling calculations in HNET

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Nuclear Science and Techniques 2022年第11期33卷 120-132页

作者： Yan-Ling Zhu Xing-Wu Chen Chen Hao Yi-Zhen Wang yun-Lin xu Fundamental Science on Nuclear Safety and Simulation Technology Laboratory Harbin Engineering UniversityHarbin 150001China Institute of Nuclear and New Energy Technology(INET) Tsinghua UniversityBeijing 100084China Purdue University West LafayetteIN 47907USA

To perform nuclear reactor simulations in a more realistic manner,the coupling scheme between neutronics and thermal-hydraulics was implemented in the HNET program for both steady-state and transient *** simplicity,efficiency,and robustness,the matrixfree Newton/Krylov(MFNK)method was applied to the steady-state coupling *** addition,the optimal perturbation size was adopted to further improve the convergence behavior of the *** the transient coupling simulation,the operator splitting method with a staggered time mesh was utilized to balance the computational cost and ***,VERA Problem 6 with power and boron perturbation and the NEACRP transient benchmark were simulated for *** numerical results show that the MFNK method can outperform Picard iteration in terms of both efficiency and robustness for a wide range of ***,the reasonable agreement between the simulation results and the reference results for the NEACRP transient benchmark verifies the capability of predicting the behavior of the nuclear reactor.

关键词： Coupling calculation High-fidelity neutronics Thermal-hydraulics Matrix-free Newton/Krylov method Transient simulation

Understanding livelihood vulnerability:a perspective from Western Sichuan’s ethnic rural settings

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Journal of Mountain Science 2024年第2期21卷 380-396页

作者： YU Yongqian JING Zheng WANG Yan QIU Xiaoping YANG xueting xu yun School of Geography and Resource Science Sichuan Normal UniversityChengdu 610101China Key Laboratory of land Resources Evaluation and Monitoring in Southwest Ministry of EducationSichuan Normal UniversityChengdu 610101China Sichuan County Economic Development Research Center Mianyang Normal UniversityMianyang 621000China Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610041China

To explore the livelihood status and key influencing factors of rural households in the minority areas,we collected flat data from 284 rural households in 32 villages across 12 counties of Western Sichuan from 2021 to *** conducted participatory household survey on the livelihood status of the rural households and try to identify the key factors to influence their livelihood vulnerability using multiple linear *** results showed that:the livelihood situation of the rural households is relatively *** vulnerability varies significantly with the income levels,education levels,and income *** vulnerability of farm households,categorized from low to high livelihood types,follows the sequence:non-agricultural dominant households,non-agricultural households,agricultural dominant households,and pure agricultural *** degree of damage to the natural environment,education costs,loan opportunities,the proportion of agricultural income to annual household income,and the presence of sick people in the household have significant positive effects on the livelihood vulnerability index(LVI)of rural households;while help from relatives and friends,net income per capita,household size,household education,agricultural land area,participation in industrial organizations,number of livestock,purchase of commercial houses,drinking water source,and self-supply of food have significant negative *** on the findings,we believe that local rural households operate in a complex livelihood system and recommend continuous interventions targeting key influences to provide empirical research support for areas facing similar situations.

关键词： Livelihood Vulnerability Rural households Ethnic areas

Evaluation of the effects of combined endoscopic variceal ligation and splenectomy with pericardial devascularization on esophageal varices

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World Journal of Gastroenterology 2006年第42期12卷 6889-6892页

作者： Bo Liu Mei-Hai Deng Nan Lin Wei-Dong Pan yun-Biao Ling Rui-yun xu Department of Hepatobiliary Surgery Third Affiliated Hospital Sun Yat-Sen University Guangzhou 510630 Guangdong Province China

AIM: To detect the hemodynamic alterations in collateral circulation before and after combined endoscopic variceal ligation (EVL) and splenectomy with pericardial devascularization by ultrasonography, and to evaluate their effect using hemodynamic parameters. METHODS: Forty-three patients with esophageal varices received combined EVL and splenectomy with pericardial devascularization for variceal eradication. The esophageal vein structures and azygos blood flow (AZBF) were detected by endoscopic ultrasonography and color Doppler ultrasound. The recurrence and rebleeding of esophageal varices were followed up. RESULTS: Patients with moderate or severe varices in the esophageal wall and those with severe peri- esophageal collateral vein varices had improvements after treatment, while the percentage of patients with severe para-esophageal collateral vein varices decreased from 54.49% to 2.33%, and the percentage of patients with detectable perforating veins decreased from 79.07% to 4.65% (P < 0.01). Color Doppler flowmetry showed a significant decrease both in AZBF (43.00%, P < 0.05) and in diameter of the azygos vein (28.85%, P < 0.05), while the blood flow rate was unchanged. The recurrence rate of esophageal varices was 2.5% (1/40, mild), while no re-bleeding cases were recorded. CONCLUSION: EVL in combination with splenectomy with pericardial devascularization can block the collateral veins both inside and outside of the esophageal wall, and is more advantagious over splenectomy in combination with pericardial devascularization or EVL in preventing recurrence and re-bleeding of varices.

关键词： Esophageal varices Endoscopic ultrasound Color Doppler ultrasonography Endoscopic variceal ligation splenectomy with pericardial devascularization

Promoted Comprehensive Properties of Polyisoprene Rubber with Extremely High Fatigue Resistance Enabled by Oligopeptide Aggregates

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Chinese Journal of Polymer Science 2023年第8期41卷 1250-1260,I0008页

作者： Yu He Ran xu Rong Zhang Chang-Cheng Wang Shi-Qi Li Jian Cao Mao-Zhu Tang yun-Xiang xu College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China

For decades,the preparation of polyisoprene rubber that can match the comprehensive properties of natural rubber(NR)has been *** sacrificial bonds have been used to promote the strength and toughness of rubbers,little is known about their effects on fatigue resistance,which is important in dynamic ***,terminal block and randomly functionalized polyisoprene rubbers tethered with di-alanine,tri-alanine and tetra-alanine were *** results showed that the flow activation energy,aggregates ordering and energy dissipation of the hydrogen-bonded aggregates increase with the elongation of oligopeptide length(XA,X=2,3,4),therefore resulting in enhanced mechanical strength and toughness of corresponding ***,the tear strengths are barely affected by oligopeptide lengths in block samples,but promoted from dipeptide to tetrapeptide in random samples,probably due to the well dispersed oligopeptide *** importantly,it is found that the tight binding aggregates of oligopeptides are critical for the excellent fatigue resistance,which is absent in polyisoprene and natural *** loose aggregates dissociate and recombine repeatedly under cyclic loading and the tight aggregates keep the network integrated and ***,the largest hysteresis of PIP-4A-V with the longest oligopeptide length give the lowest heat generation,which is contrary to the traditional sacrificial ***,the oligopeptide aggregates have repeatable energy dissipation properties and cycle life comparable to or even surpassing those of the linked proteins in NR,resulting in similar tensile strength,fracture toughness,and better fatigue resistance relative to *** deep insight on the role of oligopeptide aggregates is very useful for the engineering rubbers served in dynamic environments.

关键词： Polyisoprene Hydrogen bonding Oligopeptides Fatigueresistance

Maps to Ordered Topological Vector Spaces and Stratifiable Spaces

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Journal of Mathematical Research with Applications 2018年第1期38卷 77-84页

作者： Erguang YANG yun xu School of Mathematics & Physics Anhui University of Technology

In the paper [Monotone countable paracompactness and maps to ordered topological vector spaces, Top. Appl., 2014, 169(3): 51–70], Yamazaki initiated the study on maps with values into ordered topological vector spaces. Characterizations of monotonically countably paracompact spaces and some other spaces in terms of maps to ordered topological vector spaces were obtained. In this paper, following Yamazaki's method, we present some characterizations of stratifiable spaces and k-semi-stratifiable spaces in terms of maps with values into ordered topological vector spaces.

关键词： stratifiable spaces k-semi-stratifiable spaces maps to ordered topological vector spaces lower(upper) semi-continuity

Study on Seepage Characteristics of Composite Bucket Foundation Under Eccentric Load

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China Ocean Engineering 2021年第1期35卷 123-134页

作者： CHEN Qing-shan ZHANG Pu-yang DING Hong-yan LE Cong-huan xu yun-long State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Key Laboratory of Coast Civil Structure Safety(Tianjin University) Ministry of EducationTianjin 300072China

Under the effect of eccentric loads,when the suction pressure of the composite bucket foundation is leveled,the seepage failure is very easy to *** seepage failure occurrence causes the foundation to settle unevenly and impairs the bearing *** study uses ABAQUS finite element software to establish a composite bucket foundation model for finite element *** model simulates the seepage of the foundation penetrating process under eccentric load to reveal the induced seepage characteristics of the bucket *** most vulnerable position of seepage failure under the eccentric loading is *** suction formulas for different offset eccentric moment strategies are derived and compared with existing literature *** the derived formula is supplemented and corrected according to the pressure difference between adjacent *** can be drawn:(1)Under eccentric loads,the critical suction decreases about 7%−10%.(2)The pressure difference between adjacent cabins impacts significantly on the seepage field,and the critical suction,at most,can be reduced by 17.56%.(3)the offset strategies have little effect on the seepage *** and appropriate strategies can be selected to meet the requirement of leveling in engineering project.

关键词： composite bucket foundation eccentric load seepage failure critical suction

Adaptive fractional window increment of TCP in multihop ad hoc networks

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 820-827页

作者： Liang-hui DING Wen-jun ZHANG Xin-bing WANG Liang QIAN You-yun xu Department of Electronic Engineering Shanghai Jiao Tong University Shanghai 200240 China

We propose an adaptive fractional window increasing algorithm (AFW) to improve the performance of the fractional window increment (FeW) in (Nahm et al., 2005). AFW fully utilizes the bandwidth when the network is idle, and limits the op-erating window when the network is congested. We evaluate AFW and compare the total throughput of AFW with that of FeW in different scenarios over chain, grid, random topologies and with hybrid traffics. Extensive simulation through ns2 shows that AFW obtains 5% higher throughput than FeW, whose throughput is significantly higher than that of TCP-Newreno, with limited modi-fications.

关键词： TCP Multihop Adaptive fractional window increasing algorithm (AFW)

Isolation, purification and structural characterization of a water-soluble polysaccharide HM41 from Halenia elliptica ***

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Chinese Chemical Letters 2016年第6期27卷 979-983页

作者： Chun-Lan Liu Yang Li Gui-yun xu Ya-Shuang Li College of Life and Environmental Science Minzu University of ChinaBeijing 100081China Beijing Engineering Research Center of Food Environment and Public Health Minzu University of ChinaBeijing 100081China Institute of Chemistry Chinese Academy of SciencesBeijing 100080China

A water-soluble polysaccharide, HM（41）, was obtained from Halenia elliptica D. Don by acidic ethanol fractionation and gel filtration. Its homogeneity was confirmed by chromatography using multiple systems. HM（41） was composed of rhamnose（Rha）, arabinose（Ara）, xylose（Xyl）, mannose（Man）,galactose（Gal）, glucose（Glc） with a molar ratio of 1.0：5.5：1.8：3.0：9.4：21. The average molecular weight of HM（41） was approximately 1.17 ＊ 10~4. Periodate oxidation, Smith degradation, methylation and GC, IR,NMR, XRD, GC–MS analysis were used for the structural analysis of HM（41）. Its main chain was composed mainly of β-（1→4）Gal, β-（1→4）Glc and β-（1→6）Glc. β-（1 →4）Gal were substituted at 6-O and on average there were 14 branches among 23 main chain residues;（1→ 4）Glc had no branch;（1→6）Glc were substituted at 3-O and on average there were 9 branches among 14 main chain residues. The side chain was composed of（1→3,6）-Rha,（1→4）/（1→5）-Ara,（1 →4）/（1→5）-Xyl,（1→4,6）-Man and（1→2）-Glc. The terminal residue was composed of Ara, Xyl, Man, Gal, and Glc. Then, we demonstrated that HM and HM（41） had strong scavenging activities in vitro hydroxyl. Overall, HM and HM（41） may have potential applications in the antioxidants for medical and food industry.

关键词： Halenia elliptica D.Don Polysaccharide Isolation purification Structural analysis Antioxidant activities