Extreme Mechanics Letters最新文献

Hydrostatic pressure suppresses the electrical breakdown of flexible-rigid interfaces under deep-sea 静水压力抑制了深海柔性-刚性界面的电击穿

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-28 DOI: 10.1016/j.eml.2025.102353

Dingnan Rao , Fanghao Zhou , Zheng Chen , Tiefeng Li

{"title":"Hydrostatic pressure suppresses the electrical breakdown of flexible-rigid interfaces under deep-sea","authors":"Dingnan Rao , Fanghao Zhou , Zheng Chen , Tiefeng Li","doi":"10.1016/j.eml.2025.102353","DOIUrl":"10.1016/j.eml.2025.102353","url":null,"abstract":"<div><div>High-voltage and high-power electronic components intended for deep-sea applications encounter various challenges, including high hydrostatic pressure, temperature fluctuations, and probable seawater ingress. Consequently, encapsulation of deep-sea electronics that provides both efficient electrical insulation and pressure tolerance is crucial. This study investigates the influence of high hydrostatic pressure up to tens of MPa on the electrical breakdown of the flexible-rigid encapsulation interface, using polydimethylsiloxane and FR-4 glass epoxy as experimental materials. The experimental results show that the interface breakdown strength increases with hydrostatic pressure, in which a rapid increase is observed at 0.1MPa to 0.75MPa, followed by a slower rise at 0.75MPa to 30.0MPa. To explain this phenomenon, the cavity discharge inception field and the enhanced local electric field at contact spots under hydrostatic pressure were calculated based on interfacial contact theory. At relatively lower pressures, cavity discharge predominates in driving the interface breakdown, and the rapid growth of cavity discharge inception field leads to the sharp increase in breakdown strength with hydrostatic pressure. Whereas at higher pressures, the insulation properties of contact spots become the dominant factor. Post-breakdown analyses, including optical microscopy and micro-CT imaging, reveal that high hydrostatic pressure suppresses damage propagation, such as material carbonization, electrode defects, and gas formation. These results indicate that hydrostatic pressure helps suppress the electrical breakdown of the flexible-rigid interface. This study provides insights into the electrical breakdown behavior of flexible-rigid interfaces under high hydrostatic pressure, offering implications for the encapsulation design and optimization of deep-sea electronic components.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102353"},"PeriodicalIF":4.3,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144185435","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

A coarse-grained model for nanocellulose with hydration interfaces revealing the anomalous mechanical enhancement 具有水化界面的纳米纤维素的粗粒度模型揭示了异常的机械增强

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-26 DOI: 10.1016/j.eml.2025.102361

HaoWen Wan , YuanZhen Hou , JiaHao Li , RongZhuang Song , YinBo Zhu , HengAn Wu

{"title":"A coarse-grained model for nanocellulose with hydration interfaces revealing the anomalous mechanical enhancement","authors":"HaoWen Wan , YuanZhen Hou , JiaHao Li , RongZhuang Song , YinBo Zhu , HengAn Wu","doi":"10.1016/j.eml.2025.102361","DOIUrl":"10.1016/j.eml.2025.102361","url":null,"abstract":"<div><div>Considering the humidity-sensitivity of nanocellulose, decoding the micromechanical mechanisms hidden in hydration interface is essential for tailoring the macroscopic properties. However, exiting mechanics frameworks based on molecular modeling remain challenging to predict the hydration interface-mediated mechanical behaviors of nanocellulose at the mesoscale, hindering the correlation from micro-interface to macro-mechanics. Herein, we developed a coarse-grained (CG) model integrating non-covalent interactions and fiber-level hierarchical stacking, which unveils the anomalous mechanical enhancement of nanocellulose with hydration interfaces. The CG model, validated by all-atom (AA) simulations, accurately captured the modulus and strength scale law with overlap length, until the fiber fracture-dominated saturated state. Our results revealed how hydration extent effects the interfacial mechanics, showing that moderate hydration can enhance both toughness and strength by plasticizing hydrogen-bonding networks, while excessive hydration weakening the shear strength. Beyond the limit that AA simulations can predict, an optimal overlap regime (∼120–180 nm) was identified, where hydration-mediated interfaces can enhance the strength and toughness simultaneously. This study established a cross-scale theoretical modeling framework bridging the microscale hydration interface and macroscale mechanical regulation of nanocellulose materials, which can provide the bottom-up rational guidance for designing strong and tough nanocomposites with weak non-covalent interfaces.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"78 ","pages":"Article 102361"},"PeriodicalIF":4.3,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167210","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

Frustrated domes: From planar metamaterials to load-bearing structures 受挫圆顶：从平面超材料到承重结构

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-24 DOI: 10.1016/j.eml.2025.102352

Imtiar Niloy , Lucas Annink , Olivine Silier , Chiara Daraio , Paolo Celli

引用次数: 0

Hexagonal tessellation-based mechanical metamaterials 基于六边形镶嵌的机械超材料

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-21 DOI: 10.1016/j.eml.2025.102356

Reza Moghimimonfared, Andrea Spaggiari, Luigi Grasselli, Luke Mizzi

{"title":"Hexagonal tessellation-based mechanical metamaterials","authors":"Reza Moghimimonfared, Andrea Spaggiari, Luigi Grasselli, Luke Mizzi","doi":"10.1016/j.eml.2025.102356","DOIUrl":"10.1016/j.eml.2025.102356","url":null,"abstract":"<div><div>Mechanical metamaterials based on Euclidean polygonal tessellations represent a new class of architectured materials with the potential to exhibit a wide range of mechanical properties. In this work, we investigate a new class of systems based on the generic hexagonal tessellation with trigonal rotational symmetry and show how this tessellation has the potential to exhibit a wide range of Poisson’s ratios, including auxeticity, as well as a large spectrum of Young’s moduli whilst retaining transverse isotropy. The tessellation was characterized through geometric expressions in order to identify which combination of geometric parameters lead to realizable, concave or convex configurations and Finite Element simulations were used to evaluate the mechanical properties of these tessellations. Furthermore, three additively-manufactured prototypes, representative of the entire Poisson’s ratio range (i.e. negative, zero and positive Poisson’s ratio) were experimentally tested and analysed using Digital Image Correlation. The results obtained from both simulation and experimental approaches demonstrate the mechanical capabilities of these tessellations and indicate how new auxetic metamaterials may be found by exploring the vast design space afforded by Euclidean polygonal tilings.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102356"},"PeriodicalIF":4.3,"publicationDate":"2025-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144137877","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

Molecular Velcro for characterizing hydrogel coating adhesion 表征水凝胶涂层附着力的分子魔术贴

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-19 DOI: 10.1016/j.eml.2025.102357

Yuan Wang , Hui Yuan , Zhikun Miao , Junjie Liu , Xuxu Yang , Yecheng Wang

{"title":"Molecular Velcro for characterizing hydrogel coating adhesion","authors":"Yuan Wang , Hui Yuan , Zhikun Miao , Junjie Liu , Xuxu Yang , Yecheng Wang","doi":"10.1016/j.eml.2025.102357","DOIUrl":"10.1016/j.eml.2025.102357","url":null,"abstract":"<div><div>Rapid advances in hydrogel adhesion have enabled the development of hydrogel coating on various substrates for lubrication, drug delivery, and anti-fouling paints. The quality of adhesion between hydrogel coating and substrate is important in applications, but has been shown to be extremely challenging to assess. Here we develop a general approach to characterizing the adhesion of hydrogel coating, called the molecular Velcro. Such Velcro is a stiff layer, to which polymer chains are grafted through covalent interlinks, and adheres to hydrogel through non-covalent interlinks. We prepare a 35 μm-thick hydrogel coated on a rigid substrate, introduce a pre-cut crack to their interface, and use the molecular Velcro as backing layer to measure the adhesion toughness by 90-degree peel. As the non-covalent adhesion between the molecular Velcro and the hydrogel is instant and tough, and does not affect the mechanical properties of the hydrogel, the crack grows along the interface between the hydrogel and the substrate, or kinks into the hydrogel. Consequently, the adhesion between the hydrogel coating and the substrate is precisely characterized at various coating thicknesses, peel velocities, and crosslink densities. To show the robustness of our approach, we further measure the adhesion toughness of several types of 50 μm-thick hydrogels coated on the same substrate. This work will guide the characterization of adhesion of soft and wet coatings.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102357"},"PeriodicalIF":4.3,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144124235","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

Implicit geometric descriptor-enabled ANN Framework for a unified structure-property relationship in architected nanofibrous materials 基于隐式几何描述符的人工神经网络框架用于构建纳米纤维材料的统一结构-性能关系

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-17 DOI: 10.1016/j.eml.2025.102346

Bhanugoban Maheswaran, Komal Chawla, Abhishek Gupta, Ramathasan Thevamaran

{"title":"Implicit geometric descriptor-enabled ANN Framework for a unified structure-property relationship in architected nanofibrous materials","authors":"Bhanugoban Maheswaran, Komal Chawla, Abhishek Gupta, Ramathasan Thevamaran","doi":"10.1016/j.eml.2025.102346","DOIUrl":"10.1016/j.eml.2025.102346","url":null,"abstract":"<div><div>Hierarchically architected nanofibrous materials, such as the vertically aligned carbon nanotube (VACNT) foams, draw their exceptional mechanical properties from the interplay of nanoscale size effects and inter-nanotube interactions within and across architectures. However, the distinct effects of these mechanisms, amplified by the architecture, on different mechanical properties remain elusive, limiting their independent tunability for targeted property combinations. Reliance on architecture-specific explicit design parameters further inhibits the development of a unified structure–property relationship rooted in those nanoscale mechanisms. Here, we introduce two implicit geometric descriptors — multi-component shape invariants (MCSI) — in an artificial neural network (ANN) framework to establish a unified structure–property relationship that governs diverse architectures. The MCSIs effectively capture the key nanoscale mechanisms that give rise to the bulk mechanical properties such as specific-energy absorption, peak stress, and average modulus. Exploiting their ability to predict mechanical properties for designs that are even outside of the training data, we propose generalized design strategies to achieve desired mechanical property combinations in architected VACNT foams. Such implicit descriptor-enabled ANN frameworks can guide the accelerated and tractable design of complex hierarchical materials for applications ranging from shock-absorbing layers in extreme environments to functional components in soft robotics.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102346"},"PeriodicalIF":4.3,"publicationDate":"2025-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144089585","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

Cylindrical cavity expansion for characterizing mechanical properties of soft materials 表征软质材料力学性能的圆柱腔膨胀

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-14 DOI: 10.1016/j.eml.2025.102343

Jian Li , Zihao Xie , Hannah Varner , S. Chockalingam , Tal Cohen

{"title":"Cylindrical cavity expansion for characterizing mechanical properties of soft materials","authors":"Jian Li , Zihao Xie , Hannah Varner , S. Chockalingam , Tal Cohen","doi":"10.1016/j.eml.2025.102343","DOIUrl":"10.1016/j.eml.2025.102343","url":null,"abstract":"<div><div>The low elastic modulus of soft materials, combined with geometric nonlinearity and rate dependence, presents significant challenges in the characterization of their mechanical response. We introduce a novel method for measuring the mechanical properties of soft materials under large deformations via cylindrical cavity expansion. In this method, a cylindrical cavity is fabricated in the material and expanded by volume-controlled injection of an incompressible fluid with simultaneous measurement of the applied pressure at the cavity wall. The relationship between applied pressure and deformation at the cavity wall is then employed to characterize the nonlinear mechanical properties. This method improves traditional volume-controlled cavity expansion testing and other needle-induced cavity expansion methods by precisely controlling the geometry and size of the initial defect or cavity, significantly enhancing both the accuracy and repeatability of the experimental results. We demonstrate the feasibility of the proposed method and validate it by measuring the mechanical properties of synthetic polydimethylsiloxane (PDMS) and comparing with reported values in the literature. Results indicate that the cylindrical cavity expansion method effectively captures the response of PDMS over a wide range of stiffness (shear modulus ranging from 5 kPa to 300 kPa) and exhibit high repeatability. The proposed method overcomes limitations in characterization of ultra-soft materials using traditional testing methods, such as challenges with fabrication and clamping in uniaxial tension testing and friction and adhesion effects in compression and indentation testing, thus enabling accurate and precise characterization.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102343"},"PeriodicalIF":4.3,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144134765","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

Mode-coupled infinite topological edge state in bulk-lattice-merged mechanical Su–Schrieffer–Heeger chain 块格融合机械Su-Schrieffer-Heeger链中模式耦合无限拓扑边态

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-12 DOI: 10.1016/j.eml.2025.102334

Yeongtae Jang , Seokwoo Kim , Minkyung Kim , Guenil Kim , Eunho Kim , Junsuk Rho

{"title":"Mode-coupled infinite topological edge state in bulk-lattice-merged mechanical Su–Schrieffer–Heeger chain","authors":"Yeongtae Jang , Seokwoo Kim , Minkyung Kim , Guenil Kim , Eunho Kim , Junsuk Rho","doi":"10.1016/j.eml.2025.102334","DOIUrl":"10.1016/j.eml.2025.102334","url":null,"abstract":"<div><div>Band topology has emerged as a powerful tool for designing mechanical engineering systems, from phononic crystals to metamaterials. Various design principles — whether bulk-based or lattice-based — have been proposed and successfully implemented according to unit cell structures. Here, we present a bulk-lattice merged Su–Schrieffer–Heeger (SSH) chain constructed from single-column woodpile metamaterials. This system consists of a lattice array of cylindrical particles, where each particle’s bulk dynamics exhibits local resonance-mode coupling with wave propagation. We demonstrate that topological edge states emerge in direct correspondence with these local resonance modes, manifesting as mode-coupled topological states. Experimentally, we observe the initial emergence of these mode-coupled topological edge states, with their frequencies accurately predicted by nonlinear characteristic equations rooted in continuum dynamics and topological symmetry. Additionally, the system’s weak nonlinearity enables simultaneous frequency shifts, allowing multivariate tunability in its topological states.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102334"},"PeriodicalIF":4.3,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144106868","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

An extended Euler-Bernoulli beam principle in multi-component metamaterial towards tunable Poisson’s ratio 面向泊松比可调的多组分超材料中欧拉-伯努利光束原理的扩展

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-10 DOI: 10.1016/j.eml.2025.102347

Jingyi Zhang , Yuheng Liu , Haibao Lu , Ran Tao

{"title":"An extended Euler-Bernoulli beam principle in multi-component metamaterial towards tunable Poisson’s ratio","authors":"Jingyi Zhang , Yuheng Liu , Haibao Lu , Ran Tao","doi":"10.1016/j.eml.2025.102347","DOIUrl":"10.1016/j.eml.2025.102347","url":null,"abstract":"<div><div>In this paper, a multi-component mechanical metamaterial was proposed to achieve tunable nominal modulus and Poisson’s ratio to extend the potential and practical applications in smart materials and structures. Based on the Euler-Bernoulli beam theory, a universal model was formulated for the multi-component metamaterial to explore the constitutive relationship between the model parameters and mechanical properties. The theoretical model reveals that the Poisson’s ratio of the multi-component metamaterial could be quantitatively regulated over a broad range by manipulating the moduli of its constituent components. On this basis, a bi-component metamaterial composed of polylactic acid (PLA) and thermoplastic polyurethane (TPU), featuring distinct temperature-dependent moduli and geometric configurations, was manufactured and exhibited thermally tunable mechanical behavior. Parametric finite element simulations were conducted to investigate the synergistic effect of temperature-dependent moduli and geometric parameters on the stable mechanical behaviors of the bi-component metamaterial, with the results validated by experimental measurements. This study examines the design principle that combines material parameters (temperature-dependent moduli) and structural parameters (geometric parameters) for the multi-component mechanical metamaterial. The methodologies and insights presented in this paper provide new perspectives and technical approaches for the innovative applications of metamaterials in aerospace, biomedical, and microelectronic fields.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102347"},"PeriodicalIF":4.3,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143947712","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

Kinematic folding propagation in degree-4 origami strips 4度折纸条的运动折叠传播

IF 4.3 3区工程技术

Extreme Mechanics Letters Pub Date : 2025-05-09 DOI: 10.1016/j.eml.2025.102337

Rinki Imada , Akito Adachi , Shingo Terashima , Eiji Iwase , Tomohiro Tachi

{"title":"Kinematic folding propagation in degree-4 origami strips","authors":"Rinki Imada , Akito Adachi , Shingo Terashima , Eiji Iwase , Tomohiro Tachi","doi":"10.1016/j.eml.2025.102337","DOIUrl":"10.1016/j.eml.2025.102337","url":null,"abstract":"<div><div>Degree-4 origami strips, one-DOF mechanisms constructed by sequentially connecting degree-4 origami vertices, have inspired origami-based engineering design. However, thorough kinematic analyses were limited to a special subset of degree-4 origami strips that exhibit uniform folding along the sequence. In this study, we show how folding propagates non uniformly, i.e., gets attenuated or amplified, in a general degree-4 origami strip. We introduce the concept of kinematic folding propagation and analyze it by studying discrete dynamical systems. Our results reveal that, despite its simple structure, the strip exhibits diverse folding propagation behaviors, strongly influenced by design parameters such as sector angles and topology of the crease patterns. We show that the propagation behavior is topologically linear when adjacent vertices are connected via opposite creases. We compute and visualize folding motions, including strips that transition from a flat-folded state to a helical shape through uniform or nonuniform (attenuated/amplified) propagation upon actuation of the boundary crease. Additionally, we demonstrate folding propagation in physical models using 3D-printed prototypes with thick panels. Furthermore, we show that topologically nonlinear propagation emerges when adjacent creases are used to connect adjacent vertices. We also discuss folding propagation in curved-crease origami that is achieved by taking a continuum limit of the strip. Our findings establish kinematic folding propagation as a core functionality enabled by nonuniform folding, thereby laying the foundation for programmable origami.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102337"},"PeriodicalIF":4.3,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143935134","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