Materials and Structures最新文献_第5页

Hybrid modeling of piezoresistive pavement using finite element method and artificial neural network

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-06 DOI: 10.1617/s11527-025-02588-y

Tianling Wang, Jianwei Shi, Haopeng Wang, Markus Oeser, Pengfei Liu

{"title":"Hybrid modeling of piezoresistive pavement using finite element method and artificial neural network","authors":"Tianling Wang, Jianwei Shi, Haopeng Wang, Markus Oeser, Pengfei Liu","doi":"10.1617/s11527-025-02588-y","DOIUrl":"10.1617/s11527-025-02588-y","url":null,"abstract":"<div><p>This study aims to establish a hybrid method combining the finite element method (FEM), the mechanical–electrical model, and a back-propagation artificial neural network (BP), to simulate the piezoresistive pavement. First, the tire-pavement FEM model with piezoresistive units was established considering the viscoelasticity of the pavement materials. Subsequently, the mechanical responses of the piezoresistive units under various tire and environmental loads were converted into electrical resistance outputs via the mechanical–electrical model. Finally, BP was trained using simulated data to address challenges associated with the back-calculation of tire loads. Results indicate that the electrical resistance of the piezoresistive unit in complete contact with the tire illustrates an overall rising trend as tire load increases, which is attributed to changes in contact stress. However, the adjacent piezoresistive units display an opposite trend, which can be used to determine the lateral position of the tires. Additionally, electrical resistance shows a non-linear decrease with increasing temperature. The single-hidden-layer BP with 13 neurons was validated to demonstrate higher accuracy compared to multi-hidden-layer BP. Moreover, the Genetic algorithm-optimized single-hidden-layer BP (GA-S-BP) shows further improved performance, achieving an MSE of 1.91 and an MAPE of 8.5%, and a low probability of underestimating tire loads. The GA-S-BP designed in this study can effectively predict tire loads within permissible levels to realize the function of piezoresistive pavement.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-025-02588-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143184839","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

Reviewing experimental studies on latent thermal energy storage in cementitious composites: report of the RILEM TC 299-TES

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-05 DOI: 10.1617/s11527-024-02544-2

Claudia Fabiani, Edurne Erkizia, Didier Snoeck, Magdalena Rajczakowska, Ilda Tole, Renan Rocha Ribeiro, Miguel Azenha, Antonio Caggiano, Anna Laura Pisello

{"title":"Reviewing experimental studies on latent thermal energy storage in cementitious composites: report of the RILEM TC 299-TES","authors":"Claudia Fabiani, Edurne Erkizia, Didier Snoeck, Magdalena Rajczakowska, Ilda Tole, Renan Rocha Ribeiro, Miguel Azenha, Antonio Caggiano, Anna Laura Pisello","doi":"10.1617/s11527-024-02544-2","DOIUrl":"10.1617/s11527-024-02544-2","url":null,"abstract":"<div><p>In recent years, substantial progress has been achieved in the development of multifunctional cement-based composites, targeting improved energy efficiency and environmental sustainability while minimizing material depletion. Leveraging the high thermal capacity of these materials facilitates controlled heat storage and release, providing versatile applications in renewable energy management and heat regulation, influencing structural integrity and long-term resistance. Recent research has integrated phase change materials (PCMs) into these composites to harness their superior thermal energy density. This comprehensive review examines the latest experimental research findings on these hybrid materials, emphasizing their thermo-physical behaviour and influence on structural properties and durability. Furthermore, it provides an overview of PCM characteristics and their integration into cement-based matrices. It critically analyses the interaction between PCMs and the cement matrix, explaining effects on structural performance, hydration processes, and freeze–thaw mechanisms. Furthermore, the paper explores recent experimental techniques and protocols for measuring and assessing the structural and thermo-physical properties of these composites. By identifying key trends, the review aims to provide valuable insights into the design and optimization of cement-based composites with PCMs, ultimately enhancing energy efficiency and resource conservation.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143184773","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

Rapid and economical method for assessing metakaolin quality as SCM for low carbon binders

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-05 DOI: 10.1617/s11527-025-02579-z

Mehnaz Dhar, Shashank Bishnoi

{"title":"Rapid and economical method for assessing metakaolin quality as SCM for low carbon binders","authors":"Mehnaz Dhar, Shashank Bishnoi","doi":"10.1617/s11527-025-02579-z","DOIUrl":"10.1617/s11527-025-02579-z","url":null,"abstract":"<div><p>While the assessment of the quality of clay calcination for use in cements is important to ensure optimal performance, the currently available test methods, such as lime-reactivity, R3, XRD, TGA, etc. do not meet the requirements for a quick and cost-effective quality control at industrial clay calcination units. This paper proposes the use of a combination of methylene blue and density measurements to obtain reliable assessment of the quality of calcination of kaolinite-rich clays. Seven different clays calcined within the temperature range of 400 °C to 1000 °C were studied using these techniques and the results were compared with traditional methods. The results clearly demonstrate that the degree of conversion of kaolinite to metakaolin can be effectively obtained by measuring the residual kaolinite-content using the methylene blue test. A 50% reduction in the methylene blue value indicates the presence of under-calcined clay. Additionally, the formation of the spinel phase, which is the first unreactive product that forms upon over-calcination, can be identified by density measurements, as it is associated with higher density values. The proposed test methods can be implemented at clay-calcination units without the need for expensive equipment and highly-skilled technicians. The methods are seen to be sufficiently quick and reliable for a continuous monitoring of the calcination quality at short intervals.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143184772","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

RILEM TC 309-MCP: recommendation on terminology for mineral carbonation construction products

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-05 DOI: 10.1617/s11527-024-02467-y

Ruben Snellings, Thomas Matschei

引用次数: 0

Electro-mechanical behaviour of mortars reinforced with alternative electrically conductive inclusions

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-04 DOI: 10.1617/s11527-025-02590-4

Niki Trochoutsou, Danny Smyl, Giacomo Torelli

{"title":"Electro-mechanical behaviour of mortars reinforced with alternative electrically conductive inclusions","authors":"Niki Trochoutsou, Danny Smyl, Giacomo Torelli","doi":"10.1617/s11527-025-02590-4","DOIUrl":"10.1617/s11527-025-02590-4","url":null,"abstract":"<div><p>The incorporation of electrically conductive inclusions in structural materials can impart self-sensing functionalities, making them ideal for structural health monitoring applications. However, the use of more sustainable alternatives and their effect on key engineering properties remain largely unexplored, while the adoption of different testing protocols for the characterisation of electrical/self-sensing properties can lead to different results, thus questioning their reliability, even for existing smart composites. This paper investigates systematically the effect of recycled carbon fibres and graphite powder on the mechanical, electrical, transport properties and piezoresistive performance of cementitious mortars. Virgin carbon fibres, at dosages equivalent to those of recycled fibres, were also examined to establish a performance benchmark. Fibre content ranged from 0.05% to 1% vol., while graphite powder was added as sand replacement at contents varying from 0.3% to 3% vol. The effect of existing testing protocols and electrode layout on the piezoresistive performance was also examined, and the associated limitations and challenges are discussed in detail. The results demonstrate the potential of recycled carbon fibres as a cost-effective alternative in smart applications, without compromising electrical and piezoresistive performance. The use of 0.25%vol. of recycled or virgin carbon fibres was found to provide the desirable synergy between structural performance, cost and self-sensing properties, yielding a 50–60% increase in flexural strength, and good piezoresistivity with a gauge factor of 90–110. In contrast, the use of graphite powder resulted in composites with poor self-sensing ability even at the highest content examined (3%vol.), also accompanied by a reduction in compressive strength up to 33%.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-025-02590-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108230","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

Non-destructive lab-scale monitoring of carbonation propagation in cementitious systems using the measurement of intrinsic electrical property

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-03 DOI: 10.1617/s11527-025-02576-2

Arezou Babaahmadi, Luping Tang, Liming Huang, Sahar Iftikhar, Ingemar Löfgren

{"title":"Non-destructive lab-scale monitoring of carbonation propagation in cementitious systems using the measurement of intrinsic electrical property","authors":"Arezou Babaahmadi, Luping Tang, Liming Huang, Sahar Iftikhar, Ingemar Löfgren","doi":"10.1617/s11527-025-02576-2","DOIUrl":"10.1617/s11527-025-02576-2","url":null,"abstract":"<div><p>Monitoring carbonation in concrete is crucial for assessing the long-term durability of structures, particularly as sustainability efforts increasingly incorporate supplementary cementitious materials (SCMs) to reduce clinker content. While beneficial, SCMs alter the pore structure and pore solution chemistry, necessitating advanced methods to evaluate carbonation progression. Traditional techniques, such as splitting specimens and using pH indicators like phenolphthalein to detect changes in alkalinity, are destructive and primarily designed for ordinary Portland cement (OPC), limiting their effectiveness for SCM-incorporated systems. This paper presents the development of a novel lab-scale carbonation monitoring method based on conductivity measurements in the cementitious matrix. The proposed method examines how carbonation impacts the electrical conductivity of concrete, enabling in-situ monitoring of carbonation propagation in mortar specimens using mini-sensors embedded within the material. These mini-sensors consist of 10 sets of stainless steel 4-point Winner electrodes, spaced 2.54 mm apart, ensuring accurate conductivity measurements. By strategically placing these mini-sensors within the cementitious matrix, real-time measurements can be carried out, allowing for continuous monitoring of carbonation progression. The method provides new insights into how carbonation impacts the electrical properties of concrete, revealing dynamic changes such as a distinct peaking behavior in conductivity at the reactive carbonation front. This feature enables identification of partial carbonation front, which traditional colorimetric methods cannot detect. The results validate the method's effectiveness for OPC system and indicate its applicability when SCMs are incorporated.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-025-02576-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108235","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

Experimental evaluation of size effect on the fracture response of glass textile reinforced concrete

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-02-03 DOI: 10.1617/s11527-025-02584-2

Ramakrishna Samanthula, Ravindra Gettu, Sachin Paul

{"title":"Experimental evaluation of size effect on the fracture response of glass textile reinforced concrete","authors":"Ramakrishna Samanthula, Ravindra Gettu, Sachin Paul","doi":"10.1617/s11527-025-02584-2","DOIUrl":"10.1617/s11527-025-02584-2","url":null,"abstract":"<div><p>Textile Reinforced Concrete (TRC) is a strain-hardening cementitious composite that integrates bi-directional fabric reinforcement within a fine-grained concrete matrix, enabling the development of thin, lightweight structural and non-structural systems. This study investigates the influence of specimen thickness on the uniaxial tensile behaviour of TRC panels, using panels of varying thicknesses—10, 20, and 40 mm, reinforced with coated E-glass textiles. Two sets of TRC panels were analysed: (i) panels with a constant reinforcement ratio and (ii) panels with the same number of textile layers. The displacement and cracking behaviour including crack patterns, spacing, and openings at different strain levels, were assessed using axial extensometers and 2D Digital Image Correlation. The findings reveal a reduction in the first-crack stress with increasing panel thickness, which is consistent with the Weibull model. Additionally, a decrease in ultimate stress and textile efficiency is observed in larger panels though the reinforcement ratio is constant. Such reduction is attributed to a shift in failure mechanisms, from textile fracture to extensive debonding in some of the specimens, as the number of reinforcement layers increases, possibly due to the increase in defects with larger interface (bond) area. Thinner panels exhibit higher crack density, reduced crack spacing, and finer crack widths, at comparable strain levels. For the same number of layers, thicker panels experience wider cracks at a given nominal strain; longer yarn lengths that bridge the cracks are mobilised leading to a Weibull-type size effect, which reduces the load-carrying capacity of the textiles.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 2","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108236","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

Impact of RAP as recycled aggregate on durability-related parameters of structural concrete

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-01-30 DOI: 10.1617/s11527-025-02582-4

Nicoletta Russo, Andrea Filippi, Maddalena Carsana, Federica Lollini, Elena Redaelli

{"title":"Impact of RAP as recycled aggregate on durability-related parameters of structural concrete","authors":"Nicoletta Russo, Andrea Filippi, Maddalena Carsana, Federica Lollini, Elena Redaelli","doi":"10.1617/s11527-025-02582-4","DOIUrl":"10.1617/s11527-025-02582-4","url":null,"abstract":"<div><p>In view of promoting the recycling of construction and demolition waste, the re-utilization of Recycled Asphalt Pavement (RAP) as aggregate in structural concrete has been recently proposed and investigated. Although many studies are available on the physical and mechanical characterisation of concrete containing RAP, little is still known about how medium- to long-term durability performances are affected by the partial or total replacement of natural aggregates with RAP aggregate. In this experimental study, several durability-related properties were assessed, with the aim of investigating the possible use of RAP as partial or total replacement of natural aggregates for reinforced concrete applications. In particular, concretes were obtained with increasing RAP contents (from reference mixtures with natural aggregate only, to complete substitution with RAP aggregate), two different cement types (Portland-limestone and pozzolanic), and two water/cement ratios (0.45 and 0.65), representative of two exposure classes for chloride and carbonation induced corrosion. Water sorptivity through capillary suction and water absorption were investigated, together with the resistance to the penetration of carbonation, both under accelerated and natural exposure, and the resistance to the penetration of chlorides, under natural diffusion. Relationships between physical and mechanical properties, such as total open porosity and compressive strength, and durability-related properties were also investigated. Results showed that sorptivity experienced a neat decrease for increasing RAP contents, due to the hydrophobic nature of RAP aggregate, while water absorption was less affected. Resistance to the penetration of carbonation and chlorides were both more clearly affected by other mix design variables, such as w/c ratio and cement type, rather than RAP content.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-025-02582-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109930","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

Heavy metals stabilization in lead zinc mine tailings by using mechanical, mechano-chemical, and microwave oven activation; tailing waste utilization in building materials

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-01-28 DOI: 10.1617/s11527-024-02567-9

Karim Nawaz, Guangwei Yu, Muhammad Noman, Fang Jintao, Wisal Ahmad

{"title":"Heavy metals stabilization in lead zinc mine tailings by using mechanical, mechano-chemical, and microwave oven activation; tailing waste utilization in building materials","authors":"Karim Nawaz, Guangwei Yu, Muhammad Noman, Fang Jintao, Wisal Ahmad","doi":"10.1617/s11527-024-02567-9","DOIUrl":"10.1617/s11527-024-02567-9","url":null,"abstract":"<div><p>Lead–zinc mine tailings are hazardous waste that is produced by mining activities. Poor tailings management can lead to heavy metals leaching into the groundwater or surrounding environment if not properly managed. In this study, lead zinc mine tailings were treated using several activation methods to stabilize their heavy metals. Thus, in this study, several activation methods like mechanical, mechano-chemical, and microwave oven activation were applied to stabilize the heavy metals and reuse them effectively in construction. Toxicity-characteristic leaching procedures were performed to analyze the leaching concentration based on USEPA standard limits. A modified sequential extraction procedure (BCR) was used to determine the detailed distribution of heavy metals. 20% of tailings were replaced with cement. Tailings aggregates used in construction reduce the cost of construction and minimize the emissions of CO<sub>2</sub> to the environment as cement consumption is reduced. Characterizations supported the stabilized structure of concrete after activation methods were applied. Overall, it was concluded that activation methods can treat tailings powders and make them suitable for safe utilization in construction. Mechanical activation (200 rpm), mechano-chemical-activation (Graphene Oxide, 0.03%), and microwave oven activation (high power) for 40 minutes was selected for successful applications for concrete based on tailings due to their better-stabilizing effects and cementous properties.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109508","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

Assessment of Populus tremuloides (Michx) mechanical characteristics for glulam production

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2025-01-27 DOI: 10.1617/s11527-025-02585-1

Oscar Eric Gabriel Legrais, Pierre Blanchet, Clément Boudaud, Antoine Cogulet, João Vítor Felippe Silva

{"title":"Assessment of Populus tremuloides (Michx) mechanical characteristics for glulam production","authors":"Oscar Eric Gabriel Legrais, Pierre Blanchet, Clément Boudaud, Antoine Cogulet, João Vítor Felippe Silva","doi":"10.1617/s11527-025-02585-1","DOIUrl":"10.1617/s11527-025-02585-1","url":null,"abstract":"<div><p>This project aimed to document the mechanical properties, the bonding, and joint performance of trembling aspen to improve its use in Engineered wood products. It also aimed to study the bending characteristic and investigate the failure behavior of full-size beams made of trembling aspen. Non-destructive and destructive tests were conducted on lamellae of trembling aspen (<i>Populus tremuloides</i> Michx) following the ASTM D198. Full-size beams were manufactured following the manufacturing principles outlined in the CSA-O122, the standard for glulam production in Canada, to evaluate the performance of finger jointing, block-shear and delamination, and to establish the glulam's bending strength. Mechanical tests on trembling aspen assessed a 5th percentile value of 13.8 MPa in tension, and 40.9 MPa in bending with a mean modulus of elasticity of 10,343 MPa. The relationship between dynamic and static modulus of elasticity was analyzed and showed a strong correlation, with low relative error, and its feasibility for machine stress rating. The test conducted on the finger joint shows a characteristic value of bending strength of 31.8 MPa. The block-shear and delamination align with the requirement from the standards CSA-O122. The investigation of the bending performance on the glulam made of trembling aspen achieved a mean strength resistance of 30.3 MPa, once modified to be compared with the values from the standard, is lower than the MOR value required from the standard. In addition to the mean modulus of elasticity determined of 9013 MPa, it is also lower than the value from the standard.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"58 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109753","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