Rheologica Acta最新文献_第9页

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-28 DOI: 10.1007/s00397-023-01390-3

引用次数: 0

Analysis of the rheology of magnetic bidisperse suspensions in the regime of discontinuous shear thickening 磁性双分散悬浮液在不连续剪切增稠状态下的流变学分析

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-23 DOI: 10.1007/s00397-023-01388-x

Georges Bossis, Alain Ciffreo, Yan Grasselli, Olga Volkova

{"title":"Analysis of the rheology of magnetic bidisperse suspensions in the regime of discontinuous shear thickening","authors":"Georges Bossis, Alain Ciffreo, Yan Grasselli, Olga Volkova","doi":"10.1007/s00397-023-01388-x","DOIUrl":"10.1007/s00397-023-01388-x","url":null,"abstract":"<div><p>The phenomenon of discontinuous shear thickening (DST) is observed in suspensions of solid particles with a very high-volume fraction. For suspensions of ferromagnetic particles, this transition can also be triggered by the application of a magnetic field as discussed by Bossis et al. (2016). Here, we explore the rheological behavior of a bidisperse suspension made of magnetic-carbonyl iron (CI) and non-magnetic-calcium carbonate (CC) particles with a brush-like coating of the same superplasticizer molecule. We highlight the synergetic effect of non-magnetic particles whose inclusion in the percolated frictional network amplifies the effect of the magnetic field on the remaining fraction of magnetic particles. In plate-plate geometry, a small fraction of ferromagnetic particles (about 5%) is sufficient to trigger the transition by the application of a magnetic field and optimum for the increase of viscosity. The progressive interpenetration of the coating layers of polymer and the demagnetizing field can explain this behavior.</p><h3>Graphical abstract</h3>\u0000 <figure><div><div><div><picture><source><img></source></picture></div></div></div></figure>\u0000 </div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 4","pages":"205 - 223"},"PeriodicalIF":2.3,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4893398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Rheological transient effects on steady-state contraction flows 稳态收缩流的流变瞬态效应

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-09 DOI: 10.1007/s00397-023-01385-0

Karen Y. Pérez-Salas, Salvador Sánchez, Roberto Velasco-Segura, Gabriel Ascanio, Leopoldo Ruiz-Huerta, Juan P. Aguayo

{"title":"Rheological transient effects on steady-state contraction flows","authors":"Karen Y. Pérez-Salas, Salvador Sánchez, Roberto Velasco-Segura, Gabriel Ascanio, Leopoldo Ruiz-Huerta, Juan P. Aguayo","doi":"10.1007/s00397-023-01385-0","DOIUrl":"10.1007/s00397-023-01385-0","url":null,"abstract":"<div><h2>Abstract\u0000</h2><div><p>It may be assumed that the steady-state kinematics of viscoelastic contraction flows depends on the time-independent rheological properties only. This idea is supported by the large number of references explaining steady simulation results by considering only steady-state material functions. Even with numerical simulations, it would be difficult to prove such a statement wrong. However, using the Bautista-Manero-Puig class of models allows to obtain the same steady rheological response but with different transient evolution. Here, we considered two fluids, one displaying a monotonic trend towards the steady-state and the other with at least one visible overshoot in the material functions. Our results show that for the transient evolution with the overshoot fluid, a significant increase in the steady pressure drop is gathered. In addition, vortex response is quite different for the two fluids. This research gives evidence that the transient evolution in rheometrical functions has great impact on steady-state flow behavior.</p></div></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 4","pages":"171 - 181"},"PeriodicalIF":2.3,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-023-01385-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4383157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Extensional rheology of linear and branched polymer melts in fast converging flows 线性和支化聚合物熔体在快速收敛流中的拉伸流变学

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-09 DOI: 10.1007/s00397-023-01387-y

Yu-Ho Wen, Chen-Chieh Wang, Guo-Sian Cyue, Rong-Hao Kuo, Chia-Hsiang Hsu, Rong-Yeu Chang

{"title":"Extensional rheology of linear and branched polymer melts in fast converging flows","authors":"Yu-Ho Wen, Chen-Chieh Wang, Guo-Sian Cyue, Rong-Hao Kuo, Chia-Hsiang Hsu, Rong-Yeu Chang","doi":"10.1007/s00397-023-01387-y","DOIUrl":"10.1007/s00397-023-01387-y","url":null,"abstract":"<div><p>Extensional rheology of a variety of linear and branched polymer melts is investigated using entry flow measurements and 15:1 axisymmetric contraction flow simulations. Using a Cogswell model analysis, we show that log−log plots of entrance pressure drop versus wall shear stress display three distinct power-law regimes, the intermediate one of which is observed beyond a critical stress associated with the onset of chain stretching effects. Our observations suggest that this stress threshold is a chain architecture-dependent property characteristic of entangled polymers. Converging flow methods are used to analyze the excess pressure losses to predict the uniaxial extensional viscosity. As the temperature is increased, the progressive shift of the kink to higher strain rates seen in the flow curves can be captured by a proposed Trouton ratio model, where the characteristic time of the fluid is assumed to follow the empirical William–Landel–Ferry (WLF) equation. Experimental pressure drops in converging flows for Weissenberg numbers up to about 10<sup>5</sup> are used to evaluate predictions of an extended generalized Newtonian fluid (GNF-X) model, where a weighted viscosity for mixed flows has recently been derived and a weighting function classifies flows intermediate between shear and shearfree flows. Judging from its success in predicting the nonlinear extensional response of both linear and branched polymers, as well as its ability to differentiate the respective flow patterns, the GNF-X model should be useful for simulations of commercial polymer processing.</p><h3>Graphical abstract</h3>\u0000 <figure><div><div><div><picture><source><img></source></picture></div></div></div></figure>\u0000 </div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 4","pages":"183 - 204"},"PeriodicalIF":2.3,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4379320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Study of the tunable mechanical and swelling properties of magnetic sensitive calcium alginate nanocomposite hydrogels 磁敏海藻酸钙纳米复合水凝胶的可调力学和溶胀性能研究

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-02 DOI: 10.1007/s00397-023-01384-1

Alberto Varela-Feijoo, Alain Ponton

{"title":"Study of the tunable mechanical and swelling properties of magnetic sensitive calcium alginate nanocomposite hydrogels","authors":"Alberto Varela-Feijoo, Alain Ponton","doi":"10.1007/s00397-023-01384-1","DOIUrl":"10.1007/s00397-023-01384-1","url":null,"abstract":"<div><p>Nanocomposite hydrogels were elaborated by the addition of citrated magnetic nanoparticles (MNPs) in sodium alginate aqueous solutions ionically crosslinked by in situ release of calcium ions from calcium carbonate (CaCO<sub>3</sub>) with gradual hydrolysis of <span>d</span>-glucono-δ lactone (GDL). The sol-gel transition was studied by time-resolved mechanical spectroscopy (TRMS) in the linear viscoelastic region. The power law frequency dependence of the storage and loss moduli allowed to determine the gelation time (<i>t</i><sub>g</sub>), the power law relaxation exponent (Δ), and the gel stiffness (<i>S</i>) at the critical gel (gel at <i>t</i><sub>g</sub>) for different calcium and MNP concentrations. The effect of an applied magnetic field on these parameters was also studied for the first time. The obtained results show an effect of the concentration of both calcium and MNPs on the kinetics (<i>t</i><sub>g</sub>) and properties at the critical gel (<i>S</i> and Δ) obtaining faster kinetics and harder critical gels for higher calcium and lower MNP concentrations. Moreover, the application of the magnetic field allows to modulate the viscoelastic properties before the gel point, but no effect was observed on the structural properties of the critical gel. Finally, this work highlights how the shear viscoelastic, compressive, and swelling properties of totally gelled nanocomposite hydrogels can be successfully modulated when MNPs are introduced in the calcium alginate matrices with a good agreement between all these properties and with the properties of the critical gels.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 2-3","pages":"157 - 170"},"PeriodicalIF":2.3,"publicationDate":"2023-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4078406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Modular material properties in bimodal blends of amine functionalized polyolefins 胺功能化聚烯烃双峰共混物的模块材料性能

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-02-01 DOI: 10.1007/s00397-023-01386-z

Benjamin M. Yavitt, Ziyue Zhang, Damon J. Gilmour, Laurel L. Schafer, Savvas G. Hatzikiriakos

{"title":"Modular material properties in bimodal blends of amine functionalized polyolefins","authors":"Benjamin M. Yavitt, Ziyue Zhang, Damon J. Gilmour, Laurel L. Schafer, Savvas G. Hatzikiriakos","doi":"10.1007/s00397-023-01386-z","DOIUrl":"10.1007/s00397-023-01386-z","url":null,"abstract":"<div><p>The rheological properties of associating polymers are driven by a combination of entanglements and dynamic intermolecular interactions between chains. Binary mixtures of aminopolyolefin associating polymers with low and high molecular weight (<i>M</i><sub><i>w</i></sub>) were prepared at systematic mass fractions. The ability to tune rheological, mechanical, and adhesive properties was investigated. A transition from viscoelastic liquid to elastic solid is traversed between the limits of low and high <i>M</i><sub><i>w</i></sub> by controlling the ratio of the two components. As the fraction of high <i>M</i><sub><i>w</i></sub> increases, the mechanical properties (Young’s modulus, tensile strength) increase. Transitions between cohesive and adhesive bonding to low surface energy substrates are also observed, while the peel and lap shear strength can be tuned by the molecular weight. Due to the high density of polar amine groups, recoverable adhesion on poly(tetrafluoroethylene) is facilitated by the inherent self-healing ability of the associating polymers. The adhesion strength recovers monotonically with healing time. Controlling the ratio of low and high <i>M</i><sub><i>w</i></sub> could be used to accurately control material properties from two simple component feedstocks, replicating the behavior of an individual monomodal sample.\u0000</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 2-3","pages":"145 - 156"},"PeriodicalIF":2.3,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4384566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems 结构化同轴测量系统中有效间隙扩展的实验与仿真测定与校正

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-01-16 DOI: 10.1007/s00397-023-01383-2

Sebastian Josch, Steffen Jesinghausen, Christopher Dechert, Hans-Joachim Schmid

{"title":"Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems","authors":"Sebastian Josch, Steffen Jesinghausen, Christopher Dechert, Hans-Joachim Schmid","doi":"10.1007/s00397-023-01383-2","DOIUrl":"10.1007/s00397-023-01383-2","url":null,"abstract":"<div><p>The use of structured measuring systems to prevent wall slip is a common approach to obtain absolute rheological values. Typically, only the minimum distance between the measuring surfaces is used for further calculation, implying that no flow occurs between the structural elements. But this assumption is misleading, and a gap correction is necessary. To determine the radius correction <span>(Delta r)</span> for specific geometries, we conducted investigations on three Newtonian fluids (two silicon oils and one suspension considered to be Newtonian in the relevant shear rate range). The results show that <span>(Delta r)</span> is not only shear- and material-independent, but geometry-dependent, providing a Newtonian flow behaviour in a similar viscosity range. Therefore, a correction value can be determined with only minute deviations in different Newtonian fluids. As the conducted laboratory measurements are very time-consuming and expensive, a CFD-approach with only very small deviations was additionally developed and compared for validation purposes. Therefore, simulation is an effective and resource-efficient alternative to the presented laboratory measurements to determine <span>(Delta r)</span> for the correction of structured coaxial geometries even for non-Newtonian fluids in the future.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 2-3","pages":"129 - 143"},"PeriodicalIF":2.3,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-023-01383-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4645078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Yield stresses of concentrated suspensions of rigid particles in the volume fraction range of 0.62 to 0.78 via steady torsional flow 体积分数在0.62 ~ 0.78范围内的刚性颗粒浓悬浮液的稳态扭流屈服应力

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2023-01-13 DOI: 10.1007/s00397-022-01382-9

Li Quan, Jing He, Stephanie S. Lee, Dilhan M. Kalyon

{"title":"Yield stresses of concentrated suspensions of rigid particles in the volume fraction range of 0.62 to 0.78 via steady torsional flow","authors":"Li Quan, Jing He, Stephanie S. Lee, Dilhan M. Kalyon","doi":"10.1007/s00397-022-01382-9","DOIUrl":"10.1007/s00397-022-01382-9","url":null,"abstract":"<div><p>The ubiquitous wall slip behavior of viscoplastic fluids renders the characterization of their yield stress values a challenge but also presents an opportunity. Here, a new process for the determination of the yield stresses of viscoplastic fluids is introduced and demonstrated on concentrated suspensions subjected to steady torsional flow, i.e., parallel-disk viscometry based on the understanding of apparent wall slip. Four viscoplastic suspensions (particles with a maximum packing fraction, <i>ϕ</i><sub><i>m</i></sub>, of 0.86 mixed with a Newtonian binder at the volume fraction, <i>ϕ,</i> range of 0.62 to 0.78) were used. It is demonstrated that a step change in the slope of the torque versus apparent shear rate (or the rotational speed) occurs at a critical torque that corresponds to the yield stress of the suspension. Below the critical torque the behavior is governed by apparent slip and plug flow while above the critical torque the behavior is governed by continuous deformation and apparent slip. The yield stresses of the four concentrated suspensions were verified by comparisons with those obtained from other methods including from wall slip velocities at various shear stresses.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 2-3","pages":"111 - 127"},"PeriodicalIF":2.3,"publicationDate":"2023-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4539760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Rheological characterization of viscoplastic fluid flow in a pipe with wall slip using in situ particle image velocimetry 用原位粒子图像测速法研究粘塑性流体在有壁面滑移的管道中的流变特性

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2022-12-16 DOI: 10.1007/s00397-022-01379-4

Yamid J. García-Blanco, Vitor Y. Urazaki, Ángel. D. J. Rivera, Luis H. Quitian, Eduardo M. Germer, Admilson T. Franco

{"title":"Rheological characterization of viscoplastic fluid flow in a pipe with wall slip using in situ particle image velocimetry","authors":"Yamid J. García-Blanco, Vitor Y. Urazaki, Ángel. D. J. Rivera, Luis H. Quitian, Eduardo M. Germer, Admilson T. Franco","doi":"10.1007/s00397-022-01379-4","DOIUrl":"10.1007/s00397-022-01379-4","url":null,"abstract":"<div><p>The current experimental study investigates the rheological characterization of Carbopol gel solutions into a pipe flow using in situ visualization. The shear rate and shear stress profiles for different pressure-driven values are presented and correlated to obtain new steady-state flow curves compared with rheometrical data performed with cross-hatched parallel plate (CHPP) and smooth concentric cylindrical (SCC) geometries at a rotational rheometer. The rheological behavior for the test performed by the in situ visualization was well fitted by the generalized Herschel-Bulkley model, and different values for the coefficient of consistency (<i>K</i>), flow behavior index (<i>n</i>), and yield stress (<i>τ</i><sub>0</sub>) were fitted for the three gel solutions due to the presence of wall slip behavior. The discrepancies between the values of the rheological parameters suggest that conventional rheometrical measurements, which avoid the slippage of the fluid, lead to an overestimation of these parameters, and as a consequence, these discrepancies are extended to the dimensionless numbers calculated for the hydrodynamic flow description. Also, the experimental plug core velocity was compared with the analytical value obtained by the rotational rheometer tests to calculate an equivalent slip velocity, and such velocity depicts a quasi-linear trend with the wall shear stress. This is supported by the apparent viscosity profiles along the pipe diameter, suggesting that the slippage is an inherent characteristic of polymer gel solutions, and it is disseminated by the presence of layers near the pipe wall where the Newtonian like-behavior is presented. Finally, applying in situ visualization technique assures a better rheological characterization and accurate description of the flow conditions for fluids with complex behavior.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 2-3","pages":"93 - 110"},"PeriodicalIF":2.3,"publicationDate":"2022-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4644303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Stretch-orientation-induced reduction of friction in well-entangled bidisperse blends: a dual slip-link simulation study 良好纠缠双分散共混物中拉伸取向诱导的摩擦减少:双滑移连接模拟研究

IF 2.3 3区工程技术

Rheologica Acta Pub Date : 2022-12-15 DOI: 10.1007/s00397-022-01378-5

Souta Miyamoto, Takeshi Sato, Takashi Taniguchi

{"title":"Stretch-orientation-induced reduction of friction in well-entangled bidisperse blends: a dual slip-link simulation study","authors":"Souta Miyamoto, Takeshi Sato, Takashi Taniguchi","doi":"10.1007/s00397-022-01378-5","DOIUrl":"10.1007/s00397-022-01378-5","url":null,"abstract":"<div><p>We investigated the rheological properties of bidisperse entangled-polymer blends under high-deformation-rate flows by slip-link simulations with a friction reduction mechanism. The friction reduction mechanism induced by the stretch and orientation (SORF) is important to predict the viscoelasticity under uniaxial elongational flows. To test the applicability of this mechanism for bidisperse systems, we incorporated an expression of friction reduction (Yaoita et al. <i>Macromolecules</i> 45:2773–2782 2012) into the Doi-Takimoto slip-link model (DT model) (Doi and Takimoto <i>Philos Trans R Soc Lond A</i> 361:641–652 2003). For six experimental bidisperse systems, i.e., four polystyrene blends and two polyisoprene blends, the extended DT model where the order parameter of the friction reduction mechanism is evaluated through the component averages succeeds in reproducing the data under uniaxial elongation and shear. This success is due to the suppression of the stretch of the longer chains using the statistical average over each component. Through this study, the SORF expression improves the rheological prediction for bidisperse entangled polymer melts under uniaxial elongational flows with strain rates comparable to or larger than the inverse of the Rouse relaxation time of the longer chains. Additionally, the predictions with the SORF using the component average for the stretches reproduce the steady viscosities because under elongational flows, the states of the components with different molecular weights clearly differ from each other depending on their Rouse relaxation time. The finding means that for chain dynamics, the friction coefficient is determined by the state of the surrounding polymer chains and the state of the chain.</p></div>","PeriodicalId":755,"journal":{"name":"Rheologica Acta","volume":"62 1","pages":"57 - 70"},"PeriodicalIF":2.3,"publicationDate":"2022-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00397-022-01378-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4600729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1