Heterogeneous manufacturing is a topic that continues to receive attention.As an emerging manufacturing technology,additive manufacturing can provide strong technical support for heterogeneous manufacturing.In this st...Heterogeneous manufacturing is a topic that continues to receive attention.As an emerging manufacturing technology,additive manufacturing can provide strong technical support for heterogeneous manufacturing.In this study,both homogeneous and heterogeneous composite tubular bionic components were fabricated based on the cold metal transition technology,and the influence of deposition current on the microstructure and mechanical properties of the components was studied.The results show that the interface of the as-deposited heterogeneous composite component is well bonded,and there is an obvious mechanical interlocking structure.The compressive yield strength and elongation of the heterogeneous composite components are higher than those of the homogeneous components,and are positively correlated with the deposition current.Due to the fluctuation of element content,there are a large number of fine grain structures at the interface of the heterogeneous composite components,which increases the mechanical properties.展开更多
The rapid development of modern science,technology,and industrialization has promoted the birth of more large and complex engineering structures.When the finite element(FE)method is used for dynamic analysis of these ...The rapid development of modern science,technology,and industrialization has promoted the birth of more large and complex engineering structures.When the finite element(FE)method is used for dynamic analysis of these structures,such as high-rise buildings,aircraft,and ships,the structural FE models often contain millions of degrees of freedom.This will lead to great hardware and computing costs,which is often unacceptable in the engineering field.Therefore,many FE model reduction technologies have been developed,among which dynamic condensation and component mode synthesis are the most widely used methods.This paper reviews the historical processes and general theoretical framework of these two main categories of FE model reduction technologies and briefly summarizes the latest applications of these methods in the engineering field.Current bottlenecks in dynamic condensation and component mode synthesis methods,as well as solutions found in literature,are also briefly discussed.Finally,this paper gives a conclusion and brief prospects for future research.This review aims to comprehensively introduce the two most widely used methods of FE model reduction technologies and hopes to provide suggestions and guidance for developing new model reduction technologies.展开更多
Recent studies for computer vision and deep learning-based,post-earthquake inspections on RC structures mainly perform well for specific tasks,while the trained models must be fine-tuned and re-trained when facing new...Recent studies for computer vision and deep learning-based,post-earthquake inspections on RC structures mainly perform well for specific tasks,while the trained models must be fine-tuned and re-trained when facing new tasks and datasets,which is inevitably time-consuming.This study proposes a multi-task learning approach that simultaneously accomplishes the semantic segmentation of seven-type structural components,three-type seismic damage,and four-type deterioration states.The proposed method contains a CNN-based encoder-decoder backbone subnetwork with skip-connection modules and a multi-head,task-specific recognition subnetwork.The backbone subnetwork is designed to extract multi-level features of post-earthquake RC structures.The multi-head,task-specific recognition subnetwork consists of three individual self-attention pipelines,each of which utilizes extracted multi-level features from the backbone network as a mutual guidance for the individual segmentation task.A synthetical loss function is designed with real-time adaptive coefficients to balance multi-task losses and focus on the most unstably fluctuating one.Ablation experiments and comparative studies are further conducted to demonstrate their effectiveness and necessity.The results show that the proposed method can simultaneously recognize different structural components,seismic damage,and deterioration states,and that the overall performance of the three-task learning models gains general improvement when compared to all single-task and dual-task models.展开更多
Substrate, a typical ultra-slender aluminum alloy structural components with a large aspect ratio and complex internal structure, was traditionally manufactured by re-assembly and sub-welding. In order to realize the ...Substrate, a typical ultra-slender aluminum alloy structural components with a large aspect ratio and complex internal structure, was traditionally manufactured by re-assembly and sub-welding. In order to realize the monoblock casting of the substrate, the Pro/E software was utilized to carry out three-dimensional(3D) modeling of the substrate casting, and the filling and solidification processes were calculated, as well as the location and types of casting defects were predicted by the casting simulation software Anycasting. Results of the filling process simulation show that the metal liquid is distributed into each gap runner evenly and smoothly. There is no serious vortex phenomenon in the mold cavity, and the trajectory of the virtual particles is clear. Results of the solidification process simulation show that shrinkage cavities mainly appear at the junction of gap runners and the rail surface of the substrate. The average deformation is 0.6 mm in X direction, 3.8 mm in Y direction, and 8.2 mm in Z direction. Based on the simulation results, the casting process of the substrate was optimized, and qualified castings were successfully produced, which will provide a reference for the casting process design of other ultraslender aluminum alloy structural components.展开更多
This study investigates structural topology optimization of thermoelastic structures considering two kinds of objectives ofminimumstructural compliance and elastic strain energy with a specified available volume const...This study investigates structural topology optimization of thermoelastic structures considering two kinds of objectives ofminimumstructural compliance and elastic strain energy with a specified available volume constraint.To explicitly express the configuration evolution in the structural topology optimization under combination of mechanical and thermal load conditions,the moving morphable components(MMC)framework is adopted.Based on the characteristics of the MMC framework,the number of design variables can be reduced substantially.Corresponding optimization formulation in the MMC topology optimization framework and numerical solution procedures are developed for several numerical examples.Different optimization results are obtained with structural compliance and elastic strain energy as objectives,respectively,for thermoelastic problems.The effectiveness of the proposed optimization formulation is validated by the numerical examples.It is revealed that for the optimization design of the thermoelastic structural strength,the objective function with the minimum structural strain energy can achieve a better performance than that from structural compliance design.展开更多
This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this wo...This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this work,a set of morphable components are introduced as the basic building blocks for topology optimization,and the optimized structural layout can be found by optimizing the parameters characterizing the locations and geometries of the components explicitly.The degree of freedom(DOF)elimination technique is also employed to delete unnecessary DOFs at each iteration.Since the proposed approach solves the corresponding optimization problems in an explicit way,some challenging issues(e.g.,the large computational burden related to finite element analysis and sensitivity analysis,the localized eigenmodes in low material density regions,and the impact of excitation frequency on the optimization process)associated with the traditional approaches can be circumvented naturally.Numerical results show that the proposed approach is effective for solving topology optimization problems involving structural dynamic behaviors,especially when high-frequency responses are considered.展开更多
Although opportunistic maintenance strategies are widely used for multi-component systems, all opportunistic mainte- nance strategies only consider economic dependence and do not take structural dependence into accoun...Although opportunistic maintenance strategies are widely used for multi-component systems, all opportunistic mainte- nance strategies only consider economic dependence and do not take structural dependence into account. An opportunistic main- tenance strategy is presented for a multi-component system that considers both structural dependence and economic dependence. The cost relation and time relation among components based on structural dependence are developed. The maintenance strategy for each component of a multi-component system involves one of five maintenance actions, namely, no-maintenance, a minimal maintenance action, an imperfect maintenance action, a perfect maintenance action, and a replacement action. The maintenance action is determined by the virtual age of the component, the life expectancy of the component, and the age threshold values. Monte Carlo simulation is designed to obtain the optimal oppor- tunistic maintenance strategy of the system over its lifetime. The simulation result reveals that the minimum maintenance cost with a strategy that considers structural dependence is less than that with a strategy that does not consider structural dependence. The availability with a strategy that considers structural dependence is greater than that with a strategy that does not consider structural dependence under the same conditions.展开更多
A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small com...A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small compared to the structural scale. Different length scales should be adopted considering the efficiency and computational cost. In the principle of physics, different length scales are stipulated to correspond to different time scales. This concept lays the foundation of the framework for this multiple-time-scale algorithm. A multiple-time-scale algorithm, which involves different time steps for different regions, while enforcing the compatibility of displacement, force and stress fields across the interface, is proposed. Furthermore, a defected beam component is studied as a numerical sample. The structural component is divided into two regions： a coarse one and a fine one; a micro-defect exists in the fine region and the finite element sizes of the two regions are diametrically different. Correspondingly, two different time steps are adopted. With dynamic load applied to the beam, stress and displacement distribution of the defected beam is investigated from the global and local perspectives. The numerical sample reflects that the proposed algorithm is physically rational and computationally efficient in the potential damage simulation of civil structures.展开更多
This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite eleme...This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite elements models）. Procedure for composition of a model based on usual production process is used in CBFEM. Its results are compared to those obtained by component method for portal frame eaves moment connection with good agreement. Design of moment resistant column base is demonstrated by a case loaded by two directional bending moments and normal force. Interaction of several connections in one complex joint is explained in the last example. This paper aims to provide structural engineers with a new tool to effectively analyze and design various joints of steel structures.展开更多
The aim of this study was to analyze the physicochemical and structural characteristics of the Venn components of wheat gliadin to provide theoretical basis of gliadin for processing in dough and Chinese steamed bread...The aim of this study was to analyze the physicochemical and structural characteristics of the Venn components of wheat gliadin to provide theoretical basis of gliadin for processing in dough and Chinese steamed bread. Eight Venn components, Gli-8, Gli-9, Gli-10, Gli-11, Gli-12, Gli-13, Gli-14, and Gli-15, were extracted from wheat gliadin based on their solubility. The results of physicochemical characteristics showed that the differences in the contents, TDS,electrical conductivity, particle size and zeta potential of Venn components were significant, respectively. The content of Gli-15 in gliadin was the highest, and the content of Gli-9 was the lowest. The TDS value of Gli-9 was the highest(336.0), and the TDS value of Gli-15 was the lowest(52.0). The electrical conductivity of Gli-9 was the highest,which was 7.54 times the lowest value of Gli-11. The zeta potential of Gli-9 was -25.2 mV, and the zeta potential of the Gli-15 was -7.64 mV. However, the difference in the p H values was not significant. The results of UV spectrum and FTIR analysis showed that the secondary structures of the Venn components had significant differences. The results of the XRD patterns indicated that the Venn components might not be a single substance. The results of CLSM images implied that the molecular interactions among the components were varied. Hence, the results could provide research materials and basic data for deep processing and utilization of gliadin.展开更多
A knowledge-based system in structural component design based on fracture mechanics is developed in this paper. The system consists of several functional parts: a general inference engine, a set of knowledge bases and...A knowledge-based system in structural component design based on fracture mechanics is developed in this paper. The system consists of several functional parts: a general inference engine, a set of knowledge bases and data-bases, an interpretation engine, a bases administration system and the interface. It can simulate a human expert to make analysis and design scheme mainly for four kinds of typical structural components widely used in shipbuilding industry: pressure vessels, huge rotation constructions, pump-rod and welded structures. It is an open system which may be broadened and perfected to cover a wider range of engineering application through the modification and enlargement of knowledge bases and data-bases. It has a natural and friendly interface that may be easily operated. An on-line help service is also provided.展开更多
By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as red...By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as reduce the structural weight.To achieve this purpose,a two-step procedure is developed to design and optimize the innovative structures.Initially,the classical topology optimization is utilized to find the optimal material layout and primary load carrying paths.Afterwards,the solid-lattice hybrid structures are reconstructed using the finite element mesh based modeling method.And lattice-based optimization is performed to obtain the optimal crosssection area of the lattice structures.Finally,two typical aerospace structures are optimized to demonstrate the effectiveness of the proposed optimization framework.The numerical results are quite encouraging since the solid-lattice hybrid structures obtained by the presented approach show remarkably improved performance when compared with traditional designs.展开更多
To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly ...To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.展开更多
A topology optimization approach for designing the layout of plate structures is proposed in this article.In this approach,structural mechanical behavior is analyzed under the framework of Kirchhoff plate theory,and s...A topology optimization approach for designing the layout of plate structures is proposed in this article.In this approach,structural mechanical behavior is analyzed under the framework of Kirchhoff plate theory,and structural topology is described explicitly by a set of moving morphable components.Compared to the existing treatments where structural topology is generally described in an implicit manner,the adopted explicit geometry/layout description has demonstrated its advantages on several aspects.Firstly,the number of design variables is reduced substantially.Secondly,the obtained optimized designs are pure black-and-white and contain no gray regions.Besides,numerical experiments show that the use of Kirchhoff plate element helps save 95-99%computational time,compared with traditional treatments where solid elements are used for finite element analysis.Moreover the accuracy of the proposed method is also validated through a comparison with the corresponding theoretical solutions.Several numerical examples are also provided to demonstrate the effectiveness of the proposed approach.展开更多
Kernel independent component analysis(KICA) is a newly emerging nonlinear process monitoring method,which can extract mutually independent latent variables called independent components(ICs) from process variables. Ho...Kernel independent component analysis(KICA) is a newly emerging nonlinear process monitoring method,which can extract mutually independent latent variables called independent components(ICs) from process variables. However, when more than one IC have Gaussian distribution, it cannot extract the IC feature effectively and thus its monitoring performance will be degraded drastically. To solve such a problem, a kernel time structure independent component analysis(KTSICA) method is proposed for monitoring nonlinear process in this paper. The original process data are mapped into a feature space nonlinearly and then the whitened data are calculated in the feature space by the kernel trick. Subsequently, a time structure independent component analysis algorithm, which has no requirement for the distribution of ICs, is proposed to extract the IC feature.Finally, two monitoring statistics are built to detect process faults. When some fault is detected, a nonlinear fault identification method is developed to identify fault variables based on sensitivity analysis. The proposed monitoring method is applied in the Tennessee Eastman benchmark process. Applications demonstrate the superiority of KTSICA over KICA.展开更多
The current electromagnetic environment brings a growing demand for efficient microwave absorption(MA)materials.Ti_(3)C_(2)T_(x)MXene,one of the 2D transition-metal carbides,is considered to be a promising MA material...The current electromagnetic environment brings a growing demand for efficient microwave absorption(MA)materials.Ti_(3)C_(2)T_(x)MXene,one of the 2D transition-metal carbides,is considered to be a promising MA material owing to its superior dielectric properties and structural processability.In order to further improve the MA performance and environmental adaptability of Ti_(3)C_(2)T_(x)MXene,Ti_(3)C_(2)T_(x)MXene-based MA materials enhanced by composition and structure design have been extensively studied and the regu-lation ideas for its MA properties can be outlined as component optimization and structure manipulation strategies based on the microwave absorption mechanism.Herein,we briefly introduced the microwave absorption mechanism and focused on the design strategies of Ti_(3)C_(2)T_(x)MXene-based MA materials based on recent advances.In addition,the prospects of Ti_(3)C_(2)T_(x)MXene-based MA materials were also discussed.展开更多
As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in ...As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in electronic circuit design.This study uses numerical simulations to investigate the heat dissipation characteristics of electronic components in air-cooled servers.By adjusting airflow speed,heat sink configurations,and the arrangement of straight-fin heat sinks,we optimize heat dissipation performance and analyze the mechanisms at different airflow speeds.The results show that,at the same airflow speed,the temperature of the heat sink is lower than that of the electronic components,creating a temperature gradient that enhances heat transfer.Compared to a front-to-back arrangement of two straight-fin heat sinks,placing the heat sinks parallel to each other results in a lower maximum component temperature and better temperature uniformity.Heat sinks with fins significantly improve heat dissipation.The heat sink with semicylindrical fins on the rib surface provides the best cooling performance.Moreover,compared to natural convection,the maximum temperature of the electronic components decreases by 56.17%and 61%when the incoming flow velocity is 6 m/s with two parallel flat ribbed heat sinks and front-to-back arrangement,respectively.展开更多
Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with ot...Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with other elements, and the environment. It is subsequently composed of many components, only some of which take part in the couplings. In this paper we present a framework to detect the component correlation pattern. Firstly, the interested trajectories are decomposed into components by using decomposing methods such as the Fourier expansion and the Wavelet transformation. Secondly, the cross-correlations between the components are calculated, resulting into a component cross-correlation matrix(network).Finally, the dominant structure in the network is identified to characterize the coupling pattern in the system. Several deterministic dynamical models turn out to be characterized with rich structures such as the clustering of the components. The pattern of correlation between respiratory(RESP) and ECG signals is composed of five sub-clusters that are mainly formed by the components in ECG signal. Interestingly, only 7 components from RESP(scattered in four sub-clusters) take part in the realization of coupling between the two signals.展开更多
A deep-sea riser is a crucial component of the mining system used to lift seafloor mineral resources to the vessel.Even minor damage to the riser can lead to substantial financial losses,environmental impacts,and safe...A deep-sea riser is a crucial component of the mining system used to lift seafloor mineral resources to the vessel.Even minor damage to the riser can lead to substantial financial losses,environmental impacts,and safety hazards.However,identifying modal parameters for structural health monitoring remains a major challenge due to its large deformations and flexibility.Vibration signal-based methods are essential for detecting damage and enabling timely maintenance to minimize losses.However,accurately extracting features from one-dimensional(1D)signals is often hindered by various environmental factors and measurement noises.To address this challenge,a novel approach based on a residual convolutional auto-encoder(RCAE)is proposed for detecting damage in deep-sea mining risers,incorporating a data fusion strategy.First,principal component analysis(PCA)is applied to reduce environmental fluctuations and fuse multisensor strain readings.Subsequently,a 1D-RCAE is used to extract damage-sensitive features(DSFs)from the fused dataset.A Mahalanobis distance indicator is established to compare the DSFs of the testing and healthy risers.The specific threshold for these distances is determined using the 3σcriterion,which is employed to assess whether damage has occurred in the testing riser.The effectiveness and robustness of the proposed approach are verified through numerical simulations of a 500-m riser and experimental tests on a 6-m riser.Moreover,the impact of contaminated noise and environmental fluctuations is examined.Results show that the proposed PCA-1D-RCAE approach can effectively detect damage and is resilient to measurement noise and environmental fluctuations.The accuracy exceeds 98%under noise-free conditions and remains above 90%even with 10 dB noise.This novel approach has the potential to establish a new standard for evaluating the health and integrity of risers during mining operations,thereby reducing the high costs and risks associated with failures.Maintenance activities can be scheduled more efficiently by enabling early and accurate detection of riser damage,minimizing downtime and avoiding catastrophic failures.展开更多
We used 39 SSR markers to analyze the genetic structure of 304 major Chinese inbred rice varieties, and to compare changes in the indica or japonica components in these varieties that have been widely cultivated from ...We used 39 SSR markers to analyze the genetic structure of 304 major Chinese inbred rice varieties, and to compare changes in the indica or japonica components in these varieties that have been widely cultivated from the 1950s to the 1990s in China. The genetic structure analysis showed that these rice varieties were distinctly divided into two populations,＇ indica and japonica. The sub-structure of indica varieties was more complex than that of japonica ones. Among the various lines, late-season indica and early season japonica varieties had simpler genetic backgrounds. The seasonal ecotypes were not quite consistent with the subtypes of genetic structure. Twelve SSR loci with specific differentiation between indica and japonica were used to calculate the indica/japonica components. The differences in indica/japonica components among the five decades were not significant, except for late-season indica varieties in the 1990s, which had a significantly higher japonica component. These results will help to understand the genetic structure of the major Chinese inbred rice varieties and will be useful for indica-japonica hybrid breeding in China.展开更多
基金supported by the National Natural Science Foundation of China(52375372)the National Key Laboratory of Particle Transport and Separation Technology(KWKF-2024-3).
文摘Heterogeneous manufacturing is a topic that continues to receive attention.As an emerging manufacturing technology,additive manufacturing can provide strong technical support for heterogeneous manufacturing.In this study,both homogeneous and heterogeneous composite tubular bionic components were fabricated based on the cold metal transition technology,and the influence of deposition current on the microstructure and mechanical properties of the components was studied.The results show that the interface of the as-deposited heterogeneous composite component is well bonded,and there is an obvious mechanical interlocking structure.The compressive yield strength and elongation of the heterogeneous composite components are higher than those of the homogeneous components,and are positively correlated with the deposition current.Due to the fluctuation of element content,there are a large number of fine grain structures at the interface of the heterogeneous composite components,which increases the mechanical properties.
基金supported by grants from the National Natural Science Foundation of China(Grant No.11802069)China Postdoctoral Science Foundation(No.3236310534)Heilongjiang Provincial Postdoctoral Science Foun-dation(No.002020830603).
文摘The rapid development of modern science,technology,and industrialization has promoted the birth of more large and complex engineering structures.When the finite element(FE)method is used for dynamic analysis of these structures,such as high-rise buildings,aircraft,and ships,the structural FE models often contain millions of degrees of freedom.This will lead to great hardware and computing costs,which is often unacceptable in the engineering field.Therefore,many FE model reduction technologies have been developed,among which dynamic condensation and component mode synthesis are the most widely used methods.This paper reviews the historical processes and general theoretical framework of these two main categories of FE model reduction technologies and briefly summarizes the latest applications of these methods in the engineering field.Current bottlenecks in dynamic condensation and component mode synthesis methods,as well as solutions found in literature,are also briefly discussed.Finally,this paper gives a conclusion and brief prospects for future research.This review aims to comprehensively introduce the two most widely used methods of FE model reduction technologies and hopes to provide suggestions and guidance for developing new model reduction technologies.
基金National Key R&D Program of China under Grant No.2019YFC1511005the National Natural Science Foundation of China under Grant Nos.51921006,52192661 and 52008138+2 种基金the China Postdoctoral Science Foundation under Grant Nos.BX20190102 and 2019M661286the Heilongjiang Natural Science Foundation under Grant No.LH2022E070the Heilongjiang Province Postdoctoral Science Foundation under Grant Nos.LBH-TZ2016 and LBH-Z19064。
文摘Recent studies for computer vision and deep learning-based,post-earthquake inspections on RC structures mainly perform well for specific tasks,while the trained models must be fine-tuned and re-trained when facing new tasks and datasets,which is inevitably time-consuming.This study proposes a multi-task learning approach that simultaneously accomplishes the semantic segmentation of seven-type structural components,three-type seismic damage,and four-type deterioration states.The proposed method contains a CNN-based encoder-decoder backbone subnetwork with skip-connection modules and a multi-head,task-specific recognition subnetwork.The backbone subnetwork is designed to extract multi-level features of post-earthquake RC structures.The multi-head,task-specific recognition subnetwork consists of three individual self-attention pipelines,each of which utilizes extracted multi-level features from the backbone network as a mutual guidance for the individual segmentation task.A synthetical loss function is designed with real-time adaptive coefficients to balance multi-task losses and focus on the most unstably fluctuating one.Ablation experiments and comparative studies are further conducted to demonstrate their effectiveness and necessity.The results show that the proposed method can simultaneously recognize different structural components,seismic damage,and deterioration states,and that the overall performance of the three-task learning models gains general improvement when compared to all single-task and dual-task models.
文摘Substrate, a typical ultra-slender aluminum alloy structural components with a large aspect ratio and complex internal structure, was traditionally manufactured by re-assembly and sub-welding. In order to realize the monoblock casting of the substrate, the Pro/E software was utilized to carry out three-dimensional(3D) modeling of the substrate casting, and the filling and solidification processes were calculated, as well as the location and types of casting defects were predicted by the casting simulation software Anycasting. Results of the filling process simulation show that the metal liquid is distributed into each gap runner evenly and smoothly. There is no serious vortex phenomenon in the mold cavity, and the trajectory of the virtual particles is clear. Results of the solidification process simulation show that shrinkage cavities mainly appear at the junction of gap runners and the rail surface of the substrate. The average deformation is 0.6 mm in X direction, 3.8 mm in Y direction, and 8.2 mm in Z direction. Based on the simulation results, the casting process of the substrate was optimized, and qualified castings were successfully produced, which will provide a reference for the casting process design of other ultraslender aluminum alloy structural components.
基金Financial supports for this research were provided by the National Nat-ural Science Foundation of China(Nos.11672057,12002278,U1906233)the National Key R&D Program of China(2017YFC0307201)+1 种基金the Key R&D Program of Shandong Province(2019JZZY010801)the Fundamental Research Funds for the Central Universities(NWPU-G2020KY05308)。
文摘This study investigates structural topology optimization of thermoelastic structures considering two kinds of objectives ofminimumstructural compliance and elastic strain energy with a specified available volume constraint.To explicitly express the configuration evolution in the structural topology optimization under combination of mechanical and thermal load conditions,the moving morphable components(MMC)framework is adopted.Based on the characteristics of the MMC framework,the number of design variables can be reduced substantially.Corresponding optimization formulation in the MMC topology optimization framework and numerical solution procedures are developed for several numerical examples.Different optimization results are obtained with structural compliance and elastic strain energy as objectives,respectively,for thermoelastic problems.The effectiveness of the proposed optimization formulation is validated by the numerical examples.It is revealed that for the optimization design of the thermoelastic structural strength,the objective function with the minimum structural strain energy can achieve a better performance than that from structural compliance design.
基金Financial support from the National Natural Science Foundation of China (11821202,11872141,11922204,12002073)the National Key Research and Development Plan (2020YFB1709401)+1 种基金the Fundamental Research Funds for the Central Universities[DUT20RC (3)020]the 111 Project (B14013)is gratefully acknowledged.
文摘This work presents a moving morphable component(MMC)-based framework for solving topology optimization problems considering both single-frequency and band-frequency steady-state structural dynamic responses.In this work,a set of morphable components are introduced as the basic building blocks for topology optimization,and the optimized structural layout can be found by optimizing the parameters characterizing the locations and geometries of the components explicitly.The degree of freedom(DOF)elimination technique is also employed to delete unnecessary DOFs at each iteration.Since the proposed approach solves the corresponding optimization problems in an explicit way,some challenging issues(e.g.,the large computational burden related to finite element analysis and sensitivity analysis,the localized eigenmodes in low material density regions,and the impact of excitation frequency on the optimization process)associated with the traditional approaches can be circumvented naturally.Numerical results show that the proposed approach is effective for solving topology optimization problems involving structural dynamic behaviors,especially when high-frequency responses are considered.
基金supported by the Postdoctoral Science Foundation of China(20080431380)
文摘Although opportunistic maintenance strategies are widely used for multi-component systems, all opportunistic mainte- nance strategies only consider economic dependence and do not take structural dependence into account. An opportunistic main- tenance strategy is presented for a multi-component system that considers both structural dependence and economic dependence. The cost relation and time relation among components based on structural dependence are developed. The maintenance strategy for each component of a multi-component system involves one of five maintenance actions, namely, no-maintenance, a minimal maintenance action, an imperfect maintenance action, a perfect maintenance action, and a replacement action. The maintenance action is determined by the virtual age of the component, the life expectancy of the component, and the age threshold values. Monte Carlo simulation is designed to obtain the optimal oppor- tunistic maintenance strategy of the system over its lifetime. The simulation result reveals that the minimum maintenance cost with a strategy that considers structural dependence is less than that with a strategy that does not consider structural dependence. The availability with a strategy that considers structural dependence is greater than that with a strategy that does not consider structural dependence under the same conditions.
基金supports from NSFC(No.11302078)China Postdoctoral Science Foundation(No.2013M531139)Shanghai Postdoctoral Sustentation Fund(No.12R21412000)
文摘A multiple-time-scale algorithm is developed to numerically simulate certain structural components in civil structures where local defects inevitably exist. Spatially, the size of local defects is relatively small compared to the structural scale. Different length scales should be adopted considering the efficiency and computational cost. In the principle of physics, different length scales are stipulated to correspond to different time scales. This concept lays the foundation of the framework for this multiple-time-scale algorithm. A multiple-time-scale algorithm, which involves different time steps for different regions, while enforcing the compatibility of displacement, force and stress fields across the interface, is proposed. Furthermore, a defected beam component is studied as a numerical sample. The structural component is divided into two regions： a coarse one and a fine one; a micro-defect exists in the fine region and the finite element sizes of the two regions are diametrically different. Correspondingly, two different time steps are adopted. With dynamic load applied to the beam, stress and displacement distribution of the defected beam is investigated from the global and local perspectives. The numerical sample reflects that the proposed algorithm is physically rational and computationally efficient in the potential damage simulation of civil structures.
文摘This paper introduces CBFEM （component-based finite element model） which is a new method to analyze and design connections of steel structures. Design focused CM （component model） is compared to FEM （finite elements models）. Procedure for composition of a model based on usual production process is used in CBFEM. Its results are compared to those obtained by component method for portal frame eaves moment connection with good agreement. Design of moment resistant column base is demonstrated by a case loaded by two directional bending moments and normal force. Interaction of several connections in one complex joint is explained in the last example. This paper aims to provide structural engineers with a new tool to effectively analyze and design various joints of steel structures.
基金The authors thanks for the financial support of the National Key Research and Development Program(2016YFD0400203)the National Natural Science Foundation of China(Project No.31771897,31871852,and 31772023).
文摘The aim of this study was to analyze the physicochemical and structural characteristics of the Venn components of wheat gliadin to provide theoretical basis of gliadin for processing in dough and Chinese steamed bread. Eight Venn components, Gli-8, Gli-9, Gli-10, Gli-11, Gli-12, Gli-13, Gli-14, and Gli-15, were extracted from wheat gliadin based on their solubility. The results of physicochemical characteristics showed that the differences in the contents, TDS,electrical conductivity, particle size and zeta potential of Venn components were significant, respectively. The content of Gli-15 in gliadin was the highest, and the content of Gli-9 was the lowest. The TDS value of Gli-9 was the highest(336.0), and the TDS value of Gli-15 was the lowest(52.0). The electrical conductivity of Gli-9 was the highest,which was 7.54 times the lowest value of Gli-11. The zeta potential of Gli-9 was -25.2 mV, and the zeta potential of the Gli-15 was -7.64 mV. However, the difference in the p H values was not significant. The results of UV spectrum and FTIR analysis showed that the secondary structures of the Venn components had significant differences. The results of the XRD patterns indicated that the Venn components might not be a single substance. The results of CLSM images implied that the molecular interactions among the components were varied. Hence, the results could provide research materials and basic data for deep processing and utilization of gliadin.
基金Heilongjiang Natural Science Foundation of China(E9803).
文摘A knowledge-based system in structural component design based on fracture mechanics is developed in this paper. The system consists of several functional parts: a general inference engine, a set of knowledge bases and data-bases, an interpretation engine, a bases administration system and the interface. It can simulate a human expert to make analysis and design scheme mainly for four kinds of typical structural components widely used in shipbuilding industry: pressure vessels, huge rotation constructions, pump-rod and welded structures. It is an open system which may be broadened and perfected to cover a wider range of engineering application through the modification and enlargement of knowledge bases and data-bases. It has a natural and friendly interface that may be easily operated. An on-line help service is also provided.
基金supported by National Key Research and Development Program(No.2017YFB1102800)Key Project of NSFC(Nos.51790171 and 51761145111)NSFC for Excellent Young Scholars(No.11722219)。
文摘By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as reduce the structural weight.To achieve this purpose,a two-step procedure is developed to design and optimize the innovative structures.Initially,the classical topology optimization is utilized to find the optimal material layout and primary load carrying paths.Afterwards,the solid-lattice hybrid structures are reconstructed using the finite element mesh based modeling method.And lattice-based optimization is performed to obtain the optimal crosssection area of the lattice structures.Finally,two typical aerospace structures are optimized to demonstrate the effectiveness of the proposed optimization framework.The numerical results are quite encouraging since the solid-lattice hybrid structures obtained by the presented approach show remarkably improved performance when compared with traditional designs.
基金National Natural Science Foundation of China under Grant Nos.51738007,51808099the Fundamental Research Funds for the Central Universities under Grant No.DUT20RC(3)005。
文摘To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.
基金the National Key Research and Development Plan(Grant 2016YFB0201601)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant 11821202)+5 种基金the National Natural Science Foundation of China(Grants 11872138,11702048,11872141,11732004 and 11772076)Program for Changjiang Scholars,Innovative Research Team in University(PCSIRT),and111 Project(Grant B14013)Young Elite Scientists Sponsorship Program by CAST(Grant 2018QNRC001)Liaoning Natural Science Foundation Guidance Plan(Grant 20170520293)Fundamental Research Funds for the Central Universities,China.
文摘A topology optimization approach for designing the layout of plate structures is proposed in this article.In this approach,structural mechanical behavior is analyzed under the framework of Kirchhoff plate theory,and structural topology is described explicitly by a set of moving morphable components.Compared to the existing treatments where structural topology is generally described in an implicit manner,the adopted explicit geometry/layout description has demonstrated its advantages on several aspects.Firstly,the number of design variables is reduced substantially.Secondly,the obtained optimized designs are pure black-and-white and contain no gray regions.Besides,numerical experiments show that the use of Kirchhoff plate element helps save 95-99%computational time,compared with traditional treatments where solid elements are used for finite element analysis.Moreover the accuracy of the proposed method is also validated through a comparison with the corresponding theoretical solutions.Several numerical examples are also provided to demonstrate the effectiveness of the proposed approach.
基金Supported by the National Natural Science Foundation of China(61273160)the Natural Science Foundation of Shandong Province of China(ZR2011FM014)+1 种基金the Doctoral Fund of Shandong Province(BS2012ZZ011)the Postgraduate Innovation Funds of China University of Petroleum(CX2013060)
文摘Kernel independent component analysis(KICA) is a newly emerging nonlinear process monitoring method,which can extract mutually independent latent variables called independent components(ICs) from process variables. However, when more than one IC have Gaussian distribution, it cannot extract the IC feature effectively and thus its monitoring performance will be degraded drastically. To solve such a problem, a kernel time structure independent component analysis(KTSICA) method is proposed for monitoring nonlinear process in this paper. The original process data are mapped into a feature space nonlinearly and then the whitened data are calculated in the feature space by the kernel trick. Subsequently, a time structure independent component analysis algorithm, which has no requirement for the distribution of ICs, is proposed to extract the IC feature.Finally, two monitoring statistics are built to detect process faults. When some fault is detected, a nonlinear fault identification method is developed to identify fault variables based on sensitivity analysis. The proposed monitoring method is applied in the Tennessee Eastman benchmark process. Applications demonstrate the superiority of KTSICA over KICA.
基金financially supported by the Natural Science Foundation of Shandong Province(No.ZR2019YQ24)the Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Inno-vation Team of Structural-Functional Polymer Composites),and the Special Financial of Shandong Province(Structural Design of High-efficiency Electromagnetic Wave-absorbing Composite Mate-rials and Construction of Shandong Provincial Talent Teams(No.37000022P990304116449)).
文摘The current electromagnetic environment brings a growing demand for efficient microwave absorption(MA)materials.Ti_(3)C_(2)T_(x)MXene,one of the 2D transition-metal carbides,is considered to be a promising MA material owing to its superior dielectric properties and structural processability.In order to further improve the MA performance and environmental adaptability of Ti_(3)C_(2)T_(x)MXene,Ti_(3)C_(2)T_(x)MXene-based MA materials enhanced by composition and structure design have been extensively studied and the regu-lation ideas for its MA properties can be outlined as component optimization and structure manipulation strategies based on the microwave absorption mechanism.Herein,we briefly introduced the microwave absorption mechanism and focused on the design strategies of Ti_(3)C_(2)T_(x)MXene-based MA materials based on recent advances.In addition,the prospects of Ti_(3)C_(2)T_(x)MXene-based MA materials were also discussed.
基金supported by the key technology project of China Southern Power Grid Corporation(GZKJXM20240009).
文摘As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in electronic circuit design.This study uses numerical simulations to investigate the heat dissipation characteristics of electronic components in air-cooled servers.By adjusting airflow speed,heat sink configurations,and the arrangement of straight-fin heat sinks,we optimize heat dissipation performance and analyze the mechanisms at different airflow speeds.The results show that,at the same airflow speed,the temperature of the heat sink is lower than that of the electronic components,creating a temperature gradient that enhances heat transfer.Compared to a front-to-back arrangement of two straight-fin heat sinks,placing the heat sinks parallel to each other results in a lower maximum component temperature and better temperature uniformity.Heat sinks with fins significantly improve heat dissipation.The heat sink with semicylindrical fins on the rib surface provides the best cooling performance.Moreover,compared to natural convection,the maximum temperature of the electronic components decreases by 56.17%and 61%when the incoming flow velocity is 6 m/s with two parallel flat ribbed heat sinks and front-to-back arrangement,respectively.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11875042 and 11505114)the Shanghai Project for Construction of Top Disciplines (Grant No. USST-SYS-01)。
文摘Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with other elements, and the environment. It is subsequently composed of many components, only some of which take part in the couplings. In this paper we present a framework to detect the component correlation pattern. Firstly, the interested trajectories are decomposed into components by using decomposing methods such as the Fourier expansion and the Wavelet transformation. Secondly, the cross-correlations between the components are calculated, resulting into a component cross-correlation matrix(network).Finally, the dominant structure in the network is identified to characterize the coupling pattern in the system. Several deterministic dynamical models turn out to be characterized with rich structures such as the clustering of the components. The pattern of correlation between respiratory(RESP) and ECG signals is composed of five sub-clusters that are mainly formed by the components in ECG signal. Interestingly, only 7 components from RESP(scattered in four sub-clusters) take part in the realization of coupling between the two signals.
基金the National Key Research and Development Program of China(No.2023 YFC2811600)the National Natural Science Foundation of China(Nos.52301349,52088102)+1 种基金the Major Science and Technology Innovation Program of Qingdao(No.223-3-hygg-10-hy)the Qingdao Science Foundation for Post-doctoral Scientists(Nos.QDBSH20220202070,QDBSH20220201015)。
文摘A deep-sea riser is a crucial component of the mining system used to lift seafloor mineral resources to the vessel.Even minor damage to the riser can lead to substantial financial losses,environmental impacts,and safety hazards.However,identifying modal parameters for structural health monitoring remains a major challenge due to its large deformations and flexibility.Vibration signal-based methods are essential for detecting damage and enabling timely maintenance to minimize losses.However,accurately extracting features from one-dimensional(1D)signals is often hindered by various environmental factors and measurement noises.To address this challenge,a novel approach based on a residual convolutional auto-encoder(RCAE)is proposed for detecting damage in deep-sea mining risers,incorporating a data fusion strategy.First,principal component analysis(PCA)is applied to reduce environmental fluctuations and fuse multisensor strain readings.Subsequently,a 1D-RCAE is used to extract damage-sensitive features(DSFs)from the fused dataset.A Mahalanobis distance indicator is established to compare the DSFs of the testing and healthy risers.The specific threshold for these distances is determined using the 3σcriterion,which is employed to assess whether damage has occurred in the testing riser.The effectiveness and robustness of the proposed approach are verified through numerical simulations of a 500-m riser and experimental tests on a 6-m riser.Moreover,the impact of contaminated noise and environmental fluctuations is examined.Results show that the proposed PCA-1D-RCAE approach can effectively detect damage and is resilient to measurement noise and environmental fluctuations.The accuracy exceeds 98%under noise-free conditions and remains above 90%even with 10 dB noise.This novel approach has the potential to establish a new standard for evaluating the health and integrity of risers during mining operations,thereby reducing the high costs and risks associated with failures.Maintenance activities can be scheduled more efficiently by enabling early and accurate detection of riser damage,minimizing downtime and avoiding catastrophic failures.
基金supported by the Special Fund for Agro-scientific Research in the Public Interest(Grant No. 200903008-05)the Basic Research Budget of China National Rice Research Institute (Grant No. 2009RG001-3)the Crop Genetic Resource Protection Program of Ministry of Agriculture,China (Grant No. NB2130135)
文摘We used 39 SSR markers to analyze the genetic structure of 304 major Chinese inbred rice varieties, and to compare changes in the indica or japonica components in these varieties that have been widely cultivated from the 1950s to the 1990s in China. The genetic structure analysis showed that these rice varieties were distinctly divided into two populations,＇ indica and japonica. The sub-structure of indica varieties was more complex than that of japonica ones. Among the various lines, late-season indica and early season japonica varieties had simpler genetic backgrounds. The seasonal ecotypes were not quite consistent with the subtypes of genetic structure. Twelve SSR loci with specific differentiation between indica and japonica were used to calculate the indica/japonica components. The differences in indica/japonica components among the five decades were not significant, except for late-season indica varieties in the 1990s, which had a significantly higher japonica component. These results will help to understand the genetic structure of the major Chinese inbred rice varieties and will be useful for indica-japonica hybrid breeding in China.
