Thin-Walled Structures最新文献

{"title":"Inverse design of cylindrical curved shell metasurface for elastic wave modulation based on PSO-BP model","authors":"Jialin Wu ,&nbsp;Lingyun Yao ,&nbsp;Hui Chen","doi":"10.1016/j.tws.2025.113253","DOIUrl":"10.1016/j.tws.2025.113253","url":null,"abstract":"<div><div>Nowadays, there is a lack of systematic and comprehensive theory regarding the propagation of elastic wave on cylindrical curved shells metasurface, largely due to the complex three-dimensional structural parameters on cylindrical curved shells. As a new powerful tool for predictive modeling, machine learning method can be learned and updated constantly, and is being used to design complex metasurface structures for controlling elastic wave propagation. In this work, an inverse design method was proposed to deal with the design of cylindrical curved shell metasurface with different curvatures. Firstly, machine learning technique was utilized to construct a mapping between structural parameters and properties of elastic wave propagation. Transmittance and phase shift properties under multiple outputs are initially predicted using multiple variable geometric parameters as inputs to machine learning network. Subsequently, particle swarm optimization (PSO) algorithm is utilized on original network to improve the quality of the predictions. Finally, the constructed models are used to design the unitary metasurface with high transmittance and special phase shifts, which are combined to realize the various modulation functions of elastic wave. Experimental results disclose that the network trained based on a large data set has high prediction accuracy. It is demonstrated the proposed method can not only be used to explore more elastic wave propagation laws in cylindrical curved shells, but also lays foundation for future functions of vibration isolation, energy focusing related to these structures.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113253"},"PeriodicalIF":5.7,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143760048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Customized preparation of super martensitic stainless steel from duplex stainless steel and low alloy steel through double-wire arc additive manufacturing","authors":"Weiyao Tian ,&nbsp;Haoyu Kong ,&nbsp;Chencun Zhu ,&nbsp;Chunyu Wang ,&nbsp;Qi Sun ,&nbsp;Yibo Liu ,&nbsp;Qingjie Sun","doi":"10.1016/j.tws.2025.113252","DOIUrl":"10.1016/j.tws.2025.113252","url":null,"abstract":"<div><div>Super martensitic stainless steel (SMSS), known for its excellent properties, was widely used in marine engineering, hydropower, and petrochemical fields. This study employed double-wire arc additive manufacturing, utilizing ER2209 and ER70-G welding wires as raw materials to fabricate a thin-walled structure with SMSS composition instead of traditional martensitic stainless steel welding wire or powder. This objective of this study was to explore a convenient material preparation method that reduced dependence on raw materials, thereby enhancing production efficiency and lowering costs. The produced SMSS exhibited a well-formed appearance with a uniform composition and no macro defects. The microstructure of the top layer consisted of δ-ferrite and fresh martensite, while other areas displayed a microstructure of martensite and austenite due to thermal cycle effects. The average microhardness of the prepared SMSS was 377.9 ± 15.5 HV, with a tensile strength of 1235.5 ± 11.4 MPa and an elongation of 16.7 ± 1.0 %, demonstrating a favorable combination of mechanical properties. During the deformation of the fabricated SMSS, a phase transformation from austenite to martensite occurred, resulting in material strengthening. This innovative material processing method may facilitate the customized preparation of high-performance SMSS thin-walled structures.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113252"},"PeriodicalIF":5.7,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143760062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial Distribution and Code Revision of Solar-induced Temperature Difference of Hyperbolic Thin-Walled Structures Based on Field Measurements","authors":"Hongxin Wu ,&nbsp;Shitang Ke ,&nbsp;Jie Yang ,&nbsp;Xian'an Hou ,&nbsp;Wen Sun ,&nbsp;Yaojun Ge","doi":"10.1016/j.tws.2025.113250","DOIUrl":"10.1016/j.tws.2025.113250","url":null,"abstract":"<div><div>The distribution principles for solar-induced temperature differences in hyperbolic cooling towers differ in different countries. The current Chinese code about solar-induced temperature difference in cooling towers, originating from 1980s measurements of a singular 105-meter structure at Qinling Power Plant, fails to account for regional climatic variances and dimensional scaling effects. A non-contact 3D thermographic monitoring framework was developed through infrared thermography, with calibration protocols validated via solar irradiation experiments on precast concrete slabs to address this limitation. Subsequently, continuous diurnal monitoring of solar-induced temperature difference was performed on five geometrically distinct hyperbolic cooling towers in China's \"cold and severely cold areas\". Using statistical analysis of the measured data, the gradient distribution, time-domain evolution, spatial distribution patterns, and characteristics of the sunlit inner wall were identified. After that, the meridional distribution, the circumferential distribution, and the maximum temperature difference were quantified. Finally, The distribution rules of solar-induced temperature difference of the large hyperbolic cooling tower considering the sunward inner wall were refined. It is found that solar-induced temperature differences should be considered in \"cold and severely cold areas\" in China. The distribution rules of solar-induced temperature difference of large hyperbolic cooling tower are three-section gradient distribution along the thickness, approximately constant along the meridional direction, semicircle asymmetric trigonometric distribution along the circumferential direction on the outer wall, and negative temperature difference at the sunward inner wall. The comparative analysis demonstrated a 1.73-5.00% escalation in structural reinforcement when applying measured solar-induced temperature difference data versus conventional code specifications. The conclusion deepens the understanding of the solar-induced temperature difference distribution of large hyperbolic cooling towers, which also provides the measured basis for revising the cooling tower codes.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113250"},"PeriodicalIF":5.7,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Higher strength of double-double over traditional quad laminates in equal-stiffness design of single lap joint","authors":"Yizhou Huang ,&nbsp;Cheng Qiu ,&nbsp;Zongkai He ,&nbsp;Yile Hu ,&nbsp;Guangyong Sun ,&nbsp;Jinglei Yang","doi":"10.1016/j.tws.2025.113255","DOIUrl":"10.1016/j.tws.2025.113255","url":null,"abstract":"<div><div>Double-Double (DD) is a novel laminate design concept that not only reduces design variables and simplifies the manufacturing process but also exhibits unique homogenization properties. While theory suggests that for any QuaDriaxial (QUAD or QD) laminate, DD can provide a corresponding laminate configuration with equivalent stiffness, the mechanical behavior of their Single-Lap Joint (SLJ) still requires further investigation. In this study, a DD SLJ equivalent to the quasi-isotropic QD SLJ commonly used in fuselage structures is designed by ensuring equivalence in the in-plane stiffness matrix. While the experimental results show nearly identical in-plane stiffness, the tensile strength of the DD SLJ is approximately 13 % higher than that of the Quad SLJ. Additionally, DD SLJ exhibit reduced out-of-plane deformation compared to Quad SLJ. Both theoretical and numerical analyses are conducted to elucidate the underlying mechanisms responsible for the superior mechanical behavior of DD SLJ. The findings indicate that the observed differences are primarily due to variations in bending stiffness, despite identical in-plane stiffness matrices. The results further demonstrate that the smaller bending deformation of DD laminates leads to reduced interfacial peeling forces, making DD SLJ less susceptible to failure. Finally, a comparison of different staggered ways of DD laminates indicated no significant differences in strength or stiffness. The study demonstrates that DD SLJ, designed with equivalent in-plane stiffness matrices, not only achieve the same tensile stiffness as QD SLJs but also exhibit higher strength. This highlights the great potential of DD laminates for application in the single-lap joints of aircraft structures.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113255"},"PeriodicalIF":5.7,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic field and magnetic induction spatial distribution and stress-magnetic variation models of natural gas pipelines magnetized","authors":"Zhaoyang Han,&nbsp;Guangyuan Weng,&nbsp;Xinlei Xing,&nbsp;Yao Zhai,&nbsp;Le Wang,&nbsp;Xiyu Zhu,&nbsp;Bo Wang","doi":"10.1016/j.tws.2025.113254","DOIUrl":"10.1016/j.tws.2025.113254","url":null,"abstract":"<div><div>This study investigates the numerical relationship between the magnetic properties of pipeline steel and the stress-magnetic induction in natural gas pipelines through magnetic simulation and experimental research, based on multi-physical field coupling. A finite-element models for magnetomechanical interactions in natural gas pipelines, constructed from steel grades X52, X56, X60, X65, X70, and X80, was developed utilizing COMSOL Multiphysics software. The simulations were conducted under seven different internal pressures (0 MPa, 2 MPa, 4 MPa, 6 MPa, 8 MPa, 10 MPa, and 12 MPa) and three pipe diameters (300 mm, 406 mm, and 670 mm). These simulations facilitate the analysis of magnetic field and magnetic induction distributions within the spatial area of the pipelines. The study also examined the technical parameters for magnetization saturation across the various steel grades. A numerical relationship curve of stress and magnetic induction relative to pipeline length, termed the <em>σB-L</em> curve, was established. The reliability of the simulation results and the numerical model was validated using pipelines made from X80 and X70 steel grades. The findings confirm that the characteristics of the saturated magnetic field distribution and magnetic induction in natural gas pipelines are consistent across different steel grades. A consistent linear relationship exists between the peak internal pressure of the pipeline and the magnetic flux density. Additionally, under locally uniform magnetic fields, the trends in stress and magnetic induction density changes are parallel both along the length and across the cross-sectional direction of the pipeline. The <em>σB-L</em> curve accurately represents the magnetic coupling relationship. Experimental validation indicated that the <em>σB-L</em> curve derived from the numerical simulations provides high accuracy in assessing the magnetic-coupling stress, with a maximum error of less than 5%. This establishes a reliable theoretical basis for non-destructive, online stress detection in operational natural gas pipelines.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113254"},"PeriodicalIF":5.7,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transverse coupled resonances for ultrathin lightweight acoustic metamaterials","authors":"G. Sal-Anglada ,&nbsp;D. Yago ,&nbsp;J. Cante ,&nbsp;J. Oliver ,&nbsp;T. Pàmies ,&nbsp;D. Roca","doi":"10.1016/j.tws.2025.113219","DOIUrl":"10.1016/j.tws.2025.113219","url":null,"abstract":"<div><div>Innovations in acoustic metamaterials increasingly focus on optimizing sound insulation capabilities while addressing manufacturing and integration challenges. Previous studies have explored coupled resonance mechanisms in multilayered structures, where resonators are aligned along the direction of wave propagation. While these approaches provide enhanced sound transmission loss (STL) over broadband frequency ranges, they often require increased panel thickness to achieve the desired insulation. This study introduces a novel approach based on transverse coupled resonances, where the resonators are arranged in the same plane, i.e., perpendicular to wave propagation, by exploiting bending effects in the metamaterial design. By implementing these mechanisms in a single layer, the resulting panel’s thickness and weight are significantly reduced, simplifying the manufacturing process. The proposed transverse coupled-resonances acoustic metamaterial (TCAM) is validated numerically and experimentally using impedance tube measurements, with prototypes achieving 60 dB of attenuation over a broad frequency range around 1000 Hz. Further parametric studies show the potential for enhanced sound attenuation at even lower frequencies with thinner and lighter designs, paving the way for customizable soundproofing solutions tailored to specific application requirements.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113219"},"PeriodicalIF":5.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143739370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improving porosity distribution and mechanical performance of multilayer sandwich composites using a new strategy of gradient curing cycles during internal thermal expansion molding process","authors":"Yunfei Peng,&nbsp;Maojun Li,&nbsp;Xujing Yang,&nbsp;Bingjie Sun,&nbsp;Shilong Lv","doi":"10.1016/j.tws.2025.113244","DOIUrl":"10.1016/j.tws.2025.113244","url":null,"abstract":"<div><div>This work introduces a novel gradient curing cycle strategy for optimizing resin impregnation flow in the internal thermal expansion molding process, aimed at significantly improving porosity distribution and enhancing mechanical performance. The proposed strategy meticulously aligns the foaming characteristics of thermal expansion foam with the curing behavior of prepregs, effectively surpassing conventional curing temperature limitations. By allowing a controlled temperature hold above the resin gelation point, this approach leverages continuous and stable foam expansion to achieve superior results. A key innovation of this work lies in demonstrating the capability of the gradient curing cycle to produce CFRP with ultra-low porosity levels as low as 0.1 % sandwich composite structures. This advancement enables a systematic investigation into the spatial evolution of inter-bundle voids and elucidates the underlying mechanism for void suppression. Furthermore, the strategy enhances the bending fracture toughness and shear strength of CFRP by 22.6 % and 6.5 %, respectively, marking a significant leap in performance compared to traditional internal thermal expansion molding methods. The findings of this work establish a solid foundation for extending the application of complex components fabricated via the internal thermal expansion molding process to more demanding operational environments and increasingly complex working conditions.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"212 ","pages":"Article 113244"},"PeriodicalIF":5.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143726108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Feasibility study on the pultrusion of V-shaped profiles using CCF/PEEK prepreg tape","authors":"Kai Liu ,&nbsp;Wenzhe Song ,&nbsp;Zhongde Shan ,&nbsp;Congze Fan ,&nbsp;Yiwei Chen ,&nbsp;Feng Gao ,&nbsp;Yuejie Wen ,&nbsp;Jing-Hua Zheng","doi":"10.1016/j.tws.2025.113224","DOIUrl":"10.1016/j.tws.2025.113224","url":null,"abstract":"<div><div>The pultrusion process enables the continuous and efficient production of high-strength, lightweight composite materials, making it a key technology for the manufacturing of lightweight, high-performance structural components. This paper studies the effects of pultrusion temperature and velocity on the structural properties of pultruded continuous carbon fiber reinforced Poly-Ether-Ether-Ketone (CCF/PEEK) V-shaped profiles. Using CCF/PEEK prepreg tape as the raw material, the pultrusion was conducted at eight different temperatures ranging from 230 °C to 370 °C and at five velocities from 10 cm/min to 30 cm/min. V-shaped profiles with a thickness of 0.3 mm, a single-side width of 15 mm, and an angle of 60° were produced. Forming angle, surface roughness and cross-section morphology of the pultruded profiles were examined. Additionally, the bending load capacity of the pultruded V-shaped profiles was tested using a set of self-designed testing fixtures. Results show that below the melting temperature, i.e. 343 °C, as the pultrusion temperature increases from 230 to 330 °C, the formed profile angle gradually approach the target angle, i.e. 60° and the bending load capacity increased to 99.4 N. However, above the melting temperature, significant damage occurs with the apparent rough and irregular surface of the pultruded profiles, where the surface roughness increased to 20.3 μm at 370 °C, due to the extreme flow of the melted PEEK thermoplastic matrix and the friction between the exposed fibers with the die. The pultrusion velocity has a minor impact on performance. More importantly, an evaluation method, is proposed based on the penalty function, to add industrial selection of the optimum processing parameters for achieving a designed performance. With minor consideration of the surface roughness, the optimum process parameters are suggested as 330 °C with the designed velocity range from 10–30 cm/min. While the surface roughness is considered a dominant parameter, the pultrusion temperature is suggested to be reduced. Such study is expected to provide scientific guidance for future production of the beam structures using high performance CCF/PEEK prepreg tape and are expected to be applied as lightweight truss structures in aerospace applications.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113224"},"PeriodicalIF":5.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tensile performance of concrete-filled double skin steel tubular members using recycled aggregate concrete","authors":"Hui-Wen Tian,&nbsp;Wei Li,&nbsp;Long-Hai Lai","doi":"10.1016/j.tws.2025.113248","DOIUrl":"10.1016/j.tws.2025.113248","url":null,"abstract":"<div><div>This study investigates the axial tensile behavior of concrete-filled double-skin steel tubular (CFDST) members with recycled aggregate concrete (RAC). Axial tension tests were performed to obtain the failure modes, load and strain responses. A finite element (FE) model was developed to analyze the impact of key parameters and the interaction between the steel tubes and sandwiched RAC. The applicability of the tensile strength calculation method in the current standard, initially designed for normal CFDST members, was also evaluated for RAC-filled counterparts. Results demonstrated that RAC-filled CFDST members exhibited excellent ductility under axial tension. The confinement provided by the infilled RAC effectively enhanced the tensile strength of the steel tube. The evaluation confirmed that the current calculation method accurately predicted the tensile resistance of CFDST members using RAC.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113248"},"PeriodicalIF":5.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143748593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of progressive damage behavior of uncured GLARE: An integrated study using in-situ acoustic emission and multi-scale simulation","authors":"Meng Zhang ,&nbsp;Shenglun Zhang ,&nbsp;Bing Hu ,&nbsp;Dongdong Yan ,&nbsp;Shichen Liu ,&nbsp;Yao Wang ,&nbsp;Yong Li","doi":"10.1016/j.tws.2025.113222","DOIUrl":"10.1016/j.tws.2025.113222","url":null,"abstract":"<div><div>This study investigates the progressive damage evolution and formability of thin-walled structural material- uncured GLARE laminates under complex stress states through a combination of Nakajima tests, in-situ acoustic emission (<em>AE</em>), and multi-scale simulation techniques. A mutation phenomenon caused by internal fiber premature cracking was observed both in punch force and strain field evolution, which was substantiated by a pronounced surge in AE energy accumulation. A novel systematic multi-scale simulation framework, integrated macro-, meso‑, and micro-scale, was developed to analyze the wrinkling and cracking mechanism. Macro-scale analysis demonstrated that increasing specimen width induces a significant reduction in stress triaxiality from 0.67 to -0.73 at the edge regions of aluminum alloy layers, directly responsible for wrinkling defect initiation. In contrast, fabric shear angle variations remained below 5°, confirming their negligible contribution compared to triaxiality-driven defect. Subsequent meso‑scale simulations revealed polar fiber turns the compression-tension to the biaxial tension status with width increasing, while micro-scale analyses tracked progressive damage accumulation patterns. This work delivers a robust predictive methodology and practical guidelines for accurately forecasting deformation-induced defects, thereby facilitating more reliable process optimization and component design for uncured GLARE laminates.</div></div>","PeriodicalId":49435,"journal":{"name":"Thin-Walled Structures","volume":"213 ","pages":"Article 113222"},"PeriodicalIF":5.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143792158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}