Materials and Structures最新文献_第2页

Use of thermogravimetric and differential scanning technique for determining the quality of calcination of kaolinite clays for cement production 利用热重和差示扫描技术确定水泥生产用高岭石粘土的煅烧质量

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-18 DOI: 10.1617/s11527-024-02516-6

Mehnaz Dhar, Shashank Bishnoi

{"title":"Use of thermogravimetric and differential scanning technique for determining the quality of calcination of kaolinite clays for cement production","authors":"Mehnaz Dhar, Shashank Bishnoi","doi":"10.1617/s11527-024-02516-6","DOIUrl":"10.1617/s11527-024-02516-6","url":null,"abstract":"<div><p>To ensure the efficient production of calcined clays at an industrial scale, rapid testing method is required to prevent under or over- calcination and guarantee proper quality control. This study investigates the phase transformation processes of six kaolinitic clays calcined between 400 and 1000 °C, using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. The results confirm that the formation of spinel phase indicates over-calcination as approximately 50% reduction was observed in pozzolanic reactivity at 1000 °C. The influence of various common impurities such as quartz, iron and 2:1 clay mineral on the onset of over- calcination has been studied. The impurities and crystallinity of kaolinite were found to influence only the temperature at which spinel forms and not the quantity. Highly disordered iron rich clays showed approximately 50 °C lower temperature than ordered quartz rich kaolinite clay. DSC proved effective in detecting the presence of spinel, which is not easily identified in other techniques. The combination of TGA and DSC can therefore be used not only to assess and quantify if a clay is properly calcined or not, but also to identify the optimal calcination temperature. Furthermore, practical guidelines for implementing DSC as a quality control tool for calcination are provided that would offer valuable insights for industrial applications.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664474","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

Influence of fibre surface treatment on the performance of ultra high-performance concrete with metallic and non-metallic fibres 纤维表面处理对含有金属和非金属纤维的超高性能混凝土性能的影响

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-15 DOI: 10.1617/s11527-024-02506-8

Nabodyuti Das, Bhaskar Darshan, Prakash Nanthagopalan

{"title":"Influence of fibre surface treatment on the performance of ultra high-performance concrete with metallic and non-metallic fibres","authors":"Nabodyuti Das, Bhaskar Darshan, Prakash Nanthagopalan","doi":"10.1617/s11527-024-02506-8","DOIUrl":"10.1617/s11527-024-02506-8","url":null,"abstract":"<div><p>In ultra-high-performance concrete (UHPC), there is a need to address the challenges due to the presence of fibres on workability, dispersion and bonding with the matrix. This study addresses these concerns by applying treatments on metallic (steel) and non-metallic (glass, basalt, and carbon) fibres using Sodium Hydroxide, Potassium Dichromate, Ethylene Diamine Tetraacetic Acid, and Nitric Acid to enhance UHPC performance. Characterisation techniques such as Scanning Electron Microscopy, X-ray Diffraction, and Atomic Force Microscopy were used to evaluate the impact of these treatments. For UHPC with steel fibres, sodium hydroxide treatment improved workability by 20%, with marginal increase in compressive and flexural strength. UHPC with glass fibres exhibited over a 60% enhancement in workability at 1% fibre content, with flexural strength gaining up to 47%. UHPC with Basalt fibres showed enhanced workability and increased flexural strength up to 43% after treatment. UHPC with Carbon fibres demonstrated a 35% improvement in workability and a 43% increase in flexural strength. Sodium hydroxide treatment was preferred for steel, glass, and carbon fibres, while nitric acid treatment was most effective for basalt fibres. Post-treatment analyses revealed improved surface energy, contact angle, and oxygen/carbon ratios, enhancing the wettability of non-metallic fibres. UHPC with hybrid combinations of metallic and non-metallic fibres were also explored, achieving compressive strengths around 148 MPa and flexural strengths around 22 MPa. The flexural toughness reached 90.4 J and treated hybrid combinations could absorb up to 1353 J of impact energy without scabbing under the ballistic impact in specific test conditions, indicating significant improvement in UHPC's performance. This study provides insights on appropriate treatment for metallic and non-metallic fibres in enhancing the performance of UHPC.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142645752","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

Dynamic mechanical properties of steel fiber-reinforced reactive powder concrete after the exposure to high-temperatures 钢纤维增强活性粉末混凝土在高温下的动态力学性能

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-14 DOI: 10.1617/s11527-024-02497-6

Xinyu Feng, Haiyan Li, Le Li, Chengkun Fan

{"title":"Dynamic mechanical properties of steel fiber-reinforced reactive powder concrete after the exposure to high-temperatures","authors":"Xinyu Feng, Haiyan Li, Le Li, Chengkun Fan","doi":"10.1617/s11527-024-02497-6","DOIUrl":"10.1617/s11527-024-02497-6","url":null,"abstract":"<div><p>The mechanical properties of steel fiber-reinforced reactive-powder concrete (SF-RPC) are examined in this research project under dynamic loading after the exposure to high temperatures (residual conditions). Three mixes with similar compressive strength (143, 156 and 159 MPa on cylinders) and different fiber content by volume (<i>v</i><sub>f</sub> = 1, 2 and 3%) have been investigated, by casting short concrete cylinders (diameter = height = 50 mm), that were tested in compression as such (reference specimens, no thermal treatment) or after being exposed to 200, 400, 600 and 800℃. All tests were performed by means of a split Hopkinson pressure bar (SHPB) with a diameter of 50 mm in order to derive the stress–strain curves in dynamic conditions and to measure other mechanical properties. The Zhu–Wang–Tang’s (ZWT) damage-based constitutive model was improved and extended to take care of the temperature and of the fiber. The stress–strain curves in compression provided by the proposed model fit quite well the experimental curves. Steel fiber is shown to significantly improve the ductility and the energy-absorption capacity of RPC. The compressive strength is markedly strain-rate dependent, as it increases roughly linearly with the strain rate. As expected, high temperature markedly impacts on RPC properties, with an increase of such parameters as compressive strength, toughness and elastic modulus between 200 and 400 °C, followed by a steep decrease. At and above 800 °C the positive effect of the fiber is practically lost. The test results and the proposed constitutive model may contribute to the design codes by improving their provisions on FRC exposed to high temperatures.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142636897","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

The effects of concrete temperature on air void parameters in pumped concrete 混凝土温度对泵送混凝土空隙参数的影响

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-14 DOI: 10.1617/s11527-024-02510-y

Bahaa N. Abdelrahman, M. Tyler Ley

引用次数: 0

Chemical structure analysis of chitosan-modified road bitumen after de-icing salt treatment 除冰盐处理后壳聚糖改性路面沥青的化学结构分析

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-13 DOI: 10.1617/s11527-024-02505-9

Szymon Malinowski

{"title":"Chemical structure analysis of chitosan-modified road bitumen after de-icing salt treatment","authors":"Szymon Malinowski","doi":"10.1617/s11527-024-02505-9","DOIUrl":"10.1617/s11527-024-02505-9","url":null,"abstract":"<div><p>Asphalt pavements are constantly exposed to many destructive environmental factors including de-icing salts. The problem of the negative effect of salt ions on the performance and consequently the durability of road pavements occurs mainly in temperate climates and regions directly neighboring saline water areas. The salt ions react chemically with the bitumen components, which consequently changes their electronic structure and results in a weakening of the intermolecular interactions occurring between them. Therefore, this study focused primarily on an investigation into the potential for inhibiting the destructive erosion process of bitumen by its modification with chitosan. Studies involving changes in the acidity of the eroding solution as well as chemical and surface properties of the eroded bitumen were carried out for three different salts (NaCl, MgCl<sub>2</sub>, CaCl<sub>2</sub>) at varying concentrations, i.e. 5%, 10%, 15% (w/w) after 7 and 28 days of erosion process. Main findings demonstrate that chitosan prevents negative changes in the bitumen physico-chemical properties occurring during the salt erosion process. This effect is especially visible for the bitumen eroded with a solution of MgCl<sub>2</sub> and CaCl<sub>2</sub>. For these salts, chitosan biopolymer reduces the introduction of Cl<sup>−</sup> ions into the bitumen-building hydrocarbon structures and formation of C–Cl bonds, which is demonstrated by a reduction in the pH changes of the eroding solutions. In addition, chitosan biopolymer inhibits leaching of organic matter from the bitumen, prevents C = O groups formation and reduces the negative effects of de-icing salts on the cohesion energy of the bitumen.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-024-02505-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600766","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

Effect of agitation during the early-age hydration on thixotropy and morphology of cement paste 早期水化过程中的搅拌对水泥浆触变性和形态的影响

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-12 DOI: 10.1617/s11527-024-02504-w

Kun Zhang, Alexander Mezhov, Wolfram Schmidt

{"title":"Effect of agitation during the early-age hydration on thixotropy and morphology of cement paste","authors":"Kun Zhang, Alexander Mezhov, Wolfram Schmidt","doi":"10.1617/s11527-024-02504-w","DOIUrl":"10.1617/s11527-024-02504-w","url":null,"abstract":"<div><p>The effect of agitation during the early-age hydration on thixotropy and morphology of cement paste prepared with and without superplasticizers (SP) is investigated by applying penetration test, small amplitude oscillatory shear sweep test (SAOS), isothermal calorimetric test, scanning electron microscopy (SEM) and energy dispersive X-ray analyses (EDX). The results show that the agitation of cement paste during the induction period increases the heat flow rate and destroys existing structures of samples without changing the mineral composition of samples. Yet, if the agitation is applied during the acceleration period, the heat flow rate is significantly lowered and the morphology and mineral composition of samples undergo irreversible change, freshly formed syngenite is destroyed and no longer restored. The penetration force and the static yield stress grow linearly during the induction period and exponentially during the acceleration period. Agitation during the induction period destroys the structure, which causes the static yield stress and the penetration force values becoming nearly equal to zero. However, during the acceleration period, even after agitation the static yield stress and the penetration force exhibit high residual values, which indicates the impact of hydration to the structural build-up.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-024-02504-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600575","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

Thermal behavior of pervious concrete in wet conditions 透水混凝土在潮湿条件下的热行为

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-12 DOI: 10.1617/s11527-024-02509-5

Khaled Seifeddine, Sofiane Amziane, Evelyne Toussaint

{"title":"Thermal behavior of pervious concrete in wet conditions","authors":"Khaled Seifeddine, Sofiane Amziane, Evelyne Toussaint","doi":"10.1617/s11527-024-02509-5","DOIUrl":"10.1617/s11527-024-02509-5","url":null,"abstract":"<div><p>Conventional impervious pavements occupy a large proportion of most cities, due to urbanization and the extensive development of transportation infrastructure. These pavements cause environmental problems such as flooding and urban heat islands. Pervious concrete (PC) is a special type of concrete, characterized by a porous structure that allows water infiltration and has the potential to reduce the effects of urban heat islands through cooling by evaporation. However, due to the low water absorption and retention properties of PC, it cannot effectively meet evaporative cooling needs. This study investigates the thermal behavior of PC in dry and wet laboratory conditions under controlled climatic conditions. Three types of PCs were fabricated: gravel-based PC (PCG) and Pozzolan-based PC (PCP1), having almost the same particle size distribution, and less coarse Pozzolan-based PC with a monodisperse particle size distribution (PCP2). The results show that the surface temperature of pozzolan-based PC is up to 4 °C higher than that of PCG in dry conditions. The partial immersion test shows that the use of pozzolan aggregates in PC mixtures improves the water-absorption properties compared to PCG. In addition, pozzolan-based PC can have a surface temperature up to 11.7 °C lower than PCG during the daytime and up to 3 °C lower during the nighttime. The use of lightweight aggregates with high water-absorption coefficients in the PC mix is only recommended in wet conditions.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600509","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

Study on the skid resistance decay of submerged asphalt pavements based on texture parameters 基于纹理参数的水下沥青路面抗滑性衰减研究

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-11 DOI: 10.1617/s11527-024-02484-x

Li Junjie, Wang Hong, Guo Rongxin, Bao Lingchen, Lv Binjin, Huang Kaiyong, Zhou Bin, Yan Feng

{"title":"Study on the skid resistance decay of submerged asphalt pavements based on texture parameters","authors":"Li Junjie, Wang Hong, Guo Rongxin, Bao Lingchen, Lv Binjin, Huang Kaiyong, Zhou Bin, Yan Feng","doi":"10.1617/s11527-024-02484-x","DOIUrl":"10.1617/s11527-024-02484-x","url":null,"abstract":"<div><p>It is well known that prolonged rainwater erosion can adversely affect the surface texture of asphalt pavements, leading to a rapid decline in their skid resistance. This study utilized a small-scale accelerated loading device, a high-precision 3D scanner, and digital image processing technology to investigate the surface texture wear process and skid resistance decay trends of basalt asphalt pavement and steel slag asphalt pavement under water erosion and traffic load. The results indicate that under submerged conditions, the skid resistance (BPN) of asphalt pavement declines rapidly during the first 500,000 load cycles, and the rate of decline gradually stabilizes after 500,000 cycles. After 1.2 million load cycles, the BPN of basalt pavement decreased by 28.10%, while that of steel slag pavement decreased by 21.18%, indicating that the skid resistance of steel slag pavement is significantly better than that of basalt pavement. Texture parameters—namely, root mean square height, peak material volume, core material volume, void volume of the core, and valley void volume—exhibited the same decay trend as BPN. The average correlation coefficients between BPN and texture parameters were 0.846, 0.848, 0.898, and 0.916, respectively, indicating that texture parameters can be used as evaluation indicators for skid resistance decay. Finally, the decay of pavement skid resistance was predicted using an exponential decay equation.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1617/s11527-024-02484-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598982","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

Evaluating the effect of retarder on cement hydration and setting delay under hot weather curing condition using non-destructive methods 采用无损方法评估缓凝剂对高温天气固化条件下水泥水化和凝结延迟的影响

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-11 DOI: 10.1617/s11527-024-02496-7

Young Hwan Bae, Yu-Rhee Ahn, Yubin Jun, Hong Jae Yim

{"title":"Evaluating the effect of retarder on cement hydration and setting delay under hot weather curing condition using non-destructive methods","authors":"Young Hwan Bae, Yu-Rhee Ahn, Yubin Jun, Hong Jae Yim","doi":"10.1617/s11527-024-02496-7","DOIUrl":"10.1617/s11527-024-02496-7","url":null,"abstract":"<div><p>Hot weather concreting has gained significant attention in recent years due to the increasing annual mean temperature. The accelerated hydration process under high temperature curing conditions can lead to premature hydration products, therefore, retarding admixtures are recommended to control the setting time. Various non-destructive methods were analyzed to estimate the setting time of cement-based materials. However, the evaluation of delayed cement hydration with added retarding admixtures has not been reported. This study aims to monitor the two non-destructive methods, electrical resistivity and ultrasonic pulse velocity, during the initial 24 h in cement pastes with added calcium lignosulfonate, the most common retarder. The setting time of cement pastes, cured at temperatures of 20, 30, and 40 ℃, was evaluated based on the rise time of these non-destructive measurements. Further, the effect of added retarder on the setting delay in cement paste was discussed and compared with the Vicat needle test. The results of X-ray diffraction and thermogravimetric analysis at the rising time of electrical resistivity revealed that the use of the retarding admixture induces delayed hydration reaction of C<sub>3</sub>S, C<sub>2</sub>S, and C<sub>3</sub>A, key hydration products influencing the setting delay.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598981","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

Study on the influence of roughness and coarse aggregate area on UHPC-NC interface bonding performance 粗糙度和粗集料面积对 UHPC-NC 界面粘结性能的影响研究

IF 3.4 3区工程技术

Materials and Structures Pub Date : 2024-11-09 DOI: 10.1617/s11527-024-02507-7

Wen Sun, Jiangjiang Zhang, Shenqi Yang, Xiaolong Chen, Jing Wu, Qiong Wu, Yanhua Yang

{"title":"Study on the influence of roughness and coarse aggregate area on UHPC-NC interface bonding performance","authors":"Wen Sun, Jiangjiang Zhang, Shenqi Yang, Xiaolong Chen, Jing Wu, Qiong Wu, Yanhua Yang","doi":"10.1617/s11527-024-02507-7","DOIUrl":"10.1617/s11527-024-02507-7","url":null,"abstract":"<div><p>The aim of this study is to clarify the effect of roughening the surface of normal concrete (NC) substrates on the interfacial bonding performance, and the effect of substrate surface roughness and coarse aggregate area on the interfacial bonding performance was investigated by digital image technology. The results showed that the shear damage model of the roughened ultra-high performance concrete (UHPC) and NC composite specimens was divided into linear elasticity, yielding, and damage stages; the failure loads of the gouge interface group and the high-pressure water jet interface group were elevated by 18.3–33.9% and 43.0–140.0%, respectively, compared with those of the smooth interface group. In addition, the chiselled interface group and high-pressure water jetting interface group obtained an overall failure load of 44.2–50.0% and 53.4–90.0%, respectively; the exposed area of coarse aggregate on the substrate surface and the roughness of the concrete surface of the substrate showed a linear correlation with the interfacial shear strength, and the presence of coarse aggregate provided more mechanical anchorage points at the interface and increased the contact area with the UHPC. Substrate surface roughness increased the probability of steel fibre insertion into the groove of the substrate, and the formation of pin effect and bridge effect at the interface improved the shear slip capacity and bond strength at interface failure; substrate concrete surface roughness is a key parameter affecting the secondary damage of the UHPC-NC interface, and the degree of interface damage increased linearly with the increase of roughness.</p></div>","PeriodicalId":691,"journal":{"name":"Materials and Structures","volume":"57 10","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142598911","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