The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train col...The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track.To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs,a high-speed maglev train-viaduct coupling model,which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct,is established.Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results.After that,the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures,and the most disadvantageous combination of control loop failures is obtained.The results show that when a single control loop fails,it only has a great influence on the failed electromagnet,and the maglev response of adjacent electromagnets has no obvious change and no collision occurs.But there is a risk of rail collisions when the dual control loop fails.展开更多
Eurofer97 steel is a primary structural material for applications in fusion reactors. Laser welding is a promising technique to join Eurofer97 plasma-facing components and overcome remote handling and maintenance chal...Eurofer97 steel is a primary structural material for applications in fusion reactors. Laser welding is a promising technique to join Eurofer97 plasma-facing components and overcome remote handling and maintenance challenges. The interaction of the induced residual stress and the heterogeneous microstructure degrades the mechanical performance of such fusion components. The present study investigates the distribution of residual stress in as-welded and post-heat treated Eurofer97 joints. The mechanistic connections between microstructure, material properties, and residual stress are also studied. Neutron diffraction is used to study the through-thickness residual stress distribution in three directions,and neutron Bragg edge imaging(NBEI) is applied to study the residual strain in high spatial resolution.The microstructures and micro-hardness are characterised by electron backscatter diffraction and nanoindentation, respectively. The M-shaped residual stress distribution through the thickness of the as-welded weldment is observed by neutron diffraction line scans over a region of 1.41 × 10 mm^(2). These profiles are cross-validated over a larger area(∼56 × 40 mm^(2)) with the higher spatial resolution by NBEI. The micro-hardness value in the fusion zone of the as-welded sample almost doubles from 2.75 ± 0.09 GPa to 5.06 ± 0.29 GPa due to a combination of residual stress and cooling-induced martensite. Conventional post weld heat treatment(PWHT) is shown to release ∼90% of the residual stress but not fully restore the microstructure. By comparing its hardness with that of stress-free samples, it is found that the microstructure is the primary contribution to the hardening. This study provides insight into the prediction of structural integrity for critical structural components of fusion reactors.展开更多
Despite the long-established rocking-chair theory of lithium-ion batteries(LIBs),developing novel characterization methodology with higher spatiotemporal resolution facilitates a better understanding of the solid elec...Despite the long-established rocking-chair theory of lithium-ion batteries(LIBs),developing novel characterization methodology with higher spatiotemporal resolution facilitates a better understanding of the solid electrolyte interphase studies to shape the reaction mechanisms.In this work,we develop a Xenon ion plasma focused ion beam(Xe+PFIB)-based characterization technique to probe the cross-sectional interface of both ternary cathode and graphite anode electrodes,with the focus on revealing the chemical composition and distribution underneath the electrode surface by in-depth analysis of secondary ions.Particularly,the lithium fluoride is detected in the pristine cathode prior to contact with the electrolyte,reflecting that the electrode degradation is in the form of the loss of lithium inventory during electrode preparation.This degradation is related to the hydrolysis of the cathode material and the decomposition of the PVDF binder.Through the quantitative analysis of the transition-metal degradation products,manganese is found to be the dominant element in the newly formed inactive fluoride deposition on the cathode,while no transition metal signal can be found inside the anode electrode.These insights at high resolution implemented via a PFIB-based characterization technique not only enrich the understanding of the degradation mechanism in the LIBs but also identify and enable a high-sensitivity methodology to obtain the chemical survey at the subsurface,which will help remove the capacity-fade observed in most LIBs.展开更多
Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of den...Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of dentine and enamel was imaged by transmission electron microscopy （TEM） of samples prepared by focused ion beam （FIB） milling. High resolution TEM was carried out in the vicinity of a crack tip in dentine. An intricate ＂random weave＂ pattern of hydroxyapatile crystallites was observed and this provided a possible explanation for toughening of the mineralized dentine tissue at the nano-scale. The results reported here provide the basis for improved understanding of the rela- tionship between the multi-scale nature and the mechanical properties of hierarchically structured biomaterials, and will also be useful for the development of better prosthetic and dental restorative materials.展开更多
桥梁作为重要的基础设施,由于长期受到自然环境和日常负荷的影响,桥梁结构可能面临严重的安全隐患,因此对桥梁结构健康状态进行实时监测和预测变得尤为迫切。在现有研究中,对于复杂的桥梁结构健康状态预测,仍然存在预测值易错、稳定性...桥梁作为重要的基础设施,由于长期受到自然环境和日常负荷的影响,桥梁结构可能面临严重的安全隐患,因此对桥梁结构健康状态进行实时监测和预测变得尤为迫切。在现有研究中,对于复杂的桥梁结构健康状态预测,仍然存在预测值易错、稳定性差和实时性不足等问题。为了解决上述问题,提出基于堆叠门控循环单元(GRU)编解码器的SGRUA(Stacked GRU with Attention and Auto-Cycle)模型,通过更好地捕捉时间序列数据中的长期依赖关系和重要特征来提高预测的准确性和稳定性,并利用较少的参数量来提高预测速度使得预测实时化。首先对真实桥梁监测数据进行缺失值填补、异常值检测与处理,以保证数据满足时序预测的完整性和可用性要求;随后利用SGRUA模型对桥梁动应变指数进行时序预测,通过对比实验和消融实验证明了模型的有效性。实验结果表明,与TSMixer时序预测模型相比,SGRUA模型在桥梁B数据集上的均方根误差(RMSE)、平均绝对误差(MAE)、平均绝对百分比误差(MAPE)和对称平均绝对百分比误差(SMAPE)指标下降了11.07%、11.02%、11.00%和10.96%,为桥梁结构健康监测与预测领域提供了一种新的有效方法,同时为其他类似结构的健康监测问题提供了有益的探索与启示。展开更多
基金Project(2021zzts0775) supported by the Independent Exploration and Innovation Project for Graduate Students of Central South University,ChinaProject(2021JJ30053) supported by the Hunan Natural Science Foundation,China。
文摘The risk of failure of the control loop can occur when a high-speed maglev train runs on viaduct.Meanwhile,the failure of the levitation magnets which balances the gravity of the maglev train could cause the train collision with track.To study the dynamic response of the train and the viaduct when the levitation magnet control loop failure occurs,a high-speed maglev train-viaduct coupling model,which includes a maglev controller fitted by measured force-gap data and considers the actual structure of train and viaduct,is established.Then the accuracy and effectiveness of the established approach are validated by comparing the computed dynamic responses and frequencies with the measurement results.After that,the dynamic responses of maglev train and viaduct are discussed under normal operation and control loop failures,and the most disadvantageous combination of control loop failures is obtained.The results show that when a single control loop fails,it only has a great influence on the failed electromagnet,and the maglev response of adjacent electromagnets has no obvious change and no collision occurs.But there is a risk of rail collisions when the dual control loop fails.
文摘Eurofer97 steel is a primary structural material for applications in fusion reactors. Laser welding is a promising technique to join Eurofer97 plasma-facing components and overcome remote handling and maintenance challenges. The interaction of the induced residual stress and the heterogeneous microstructure degrades the mechanical performance of such fusion components. The present study investigates the distribution of residual stress in as-welded and post-heat treated Eurofer97 joints. The mechanistic connections between microstructure, material properties, and residual stress are also studied. Neutron diffraction is used to study the through-thickness residual stress distribution in three directions,and neutron Bragg edge imaging(NBEI) is applied to study the residual strain in high spatial resolution.The microstructures and micro-hardness are characterised by electron backscatter diffraction and nanoindentation, respectively. The M-shaped residual stress distribution through the thickness of the as-welded weldment is observed by neutron diffraction line scans over a region of 1.41 × 10 mm^(2). These profiles are cross-validated over a larger area(∼56 × 40 mm^(2)) with the higher spatial resolution by NBEI. The micro-hardness value in the fusion zone of the as-welded sample almost doubles from 2.75 ± 0.09 GPa to 5.06 ± 0.29 GPa due to a combination of residual stress and cooling-induced martensite. Conventional post weld heat treatment(PWHT) is shown to release ∼90% of the residual stress but not fully restore the microstructure. By comparing its hardness with that of stress-free samples, it is found that the microstructure is the primary contribution to the hardening. This study provides insight into the prediction of structural integrity for critical structural components of fusion reactors.
基金The electrochemical part of the research done at Oak Ridge National Laboratory,managed by UT Battelle,LLC,for the U.S.Department of Energy(DOE)under contract DE-AC05-00OR22725,was sponsored by the Office of Energy Efficiency and Renewable Energy(EERE)Vehicle Technologies OfficeT.S.acknowledges the support from the EPSRC project(EP/P001521/1)“Integrated Plasma Source Focused Ion Beam with Scanning Electron Microscope.”Y.Z.acknowledges support from EPSRC project(EP/V002260/1),UK National Measurement System and ISCF Measurement Fellowship.
文摘Despite the long-established rocking-chair theory of lithium-ion batteries(LIBs),developing novel characterization methodology with higher spatiotemporal resolution facilitates a better understanding of the solid electrolyte interphase studies to shape the reaction mechanisms.In this work,we develop a Xenon ion plasma focused ion beam(Xe+PFIB)-based characterization technique to probe the cross-sectional interface of both ternary cathode and graphite anode electrodes,with the focus on revealing the chemical composition and distribution underneath the electrode surface by in-depth analysis of secondary ions.Particularly,the lithium fluoride is detected in the pristine cathode prior to contact with the electrolyte,reflecting that the electrode degradation is in the form of the loss of lithium inventory during electrode preparation.This degradation is related to the hydrolysis of the cathode material and the decomposition of the PVDF binder.Through the quantitative analysis of the transition-metal degradation products,manganese is found to be the dominant element in the newly formed inactive fluoride deposition on the cathode,while no transition metal signal can be found inside the anode electrode.These insights at high resolution implemented via a PFIB-based characterization technique not only enrich the understanding of the degradation mechanism in the LIBs but also identify and enable a high-sensitivity methodology to obtain the chemical survey at the subsurface,which will help remove the capacity-fade observed in most LIBs.
基金supported by EPSRC through grants"Multi-disciplinary Centre for In-situ Processing Studies(CIPS)"(EP/I020691),"Micromechanical Modelling and Experimentation"(EP/G004676),and "New Dimensions of Engineering Science at Large Facilities"(EP/H003215)
文摘Human dental hard tissues are dentine, cementum, and enamel. These are hydrated mineralised composite tissues with a hierarchical structure and versatile thermo-mechanical properties. The hierarchical structure of dentine and enamel was imaged by transmission electron microscopy （TEM） of samples prepared by focused ion beam （FIB） milling. High resolution TEM was carried out in the vicinity of a crack tip in dentine. An intricate ＂random weave＂ pattern of hydroxyapatile crystallites was observed and this provided a possible explanation for toughening of the mineralized dentine tissue at the nano-scale. The results reported here provide the basis for improved understanding of the rela- tionship between the multi-scale nature and the mechanical properties of hierarchically structured biomaterials, and will also be useful for the development of better prosthetic and dental restorative materials.
文摘桥梁作为重要的基础设施,由于长期受到自然环境和日常负荷的影响,桥梁结构可能面临严重的安全隐患,因此对桥梁结构健康状态进行实时监测和预测变得尤为迫切。在现有研究中,对于复杂的桥梁结构健康状态预测,仍然存在预测值易错、稳定性差和实时性不足等问题。为了解决上述问题,提出基于堆叠门控循环单元(GRU)编解码器的SGRUA(Stacked GRU with Attention and Auto-Cycle)模型,通过更好地捕捉时间序列数据中的长期依赖关系和重要特征来提高预测的准确性和稳定性,并利用较少的参数量来提高预测速度使得预测实时化。首先对真实桥梁监测数据进行缺失值填补、异常值检测与处理,以保证数据满足时序预测的完整性和可用性要求;随后利用SGRUA模型对桥梁动应变指数进行时序预测,通过对比实验和消融实验证明了模型的有效性。实验结果表明,与TSMixer时序预测模型相比,SGRUA模型在桥梁B数据集上的均方根误差(RMSE)、平均绝对误差(MAE)、平均绝对百分比误差(MAPE)和对称平均绝对百分比误差(SMAPE)指标下降了11.07%、11.02%、11.00%和10.96%,为桥梁结构健康监测与预测领域提供了一种新的有效方法,同时为其他类似结构的健康监测问题提供了有益的探索与启示。
