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Static-based early-damage detection using symbolic data analysis and unsupervised learning methods

João Pedro SANTOS,Christian CREMONA,André D. ORCESI,Paulo SILVEIRA,Luis CALADO

《结构与土木工程前沿（英文）》 2015年 第9卷 第1期   页码 1-16 doi: 10.1007/s11709-014-0277-3

摘要： A large amount of researches and studies have been recently performed by applying statistical and machine learning techniques for vibration-based damage detection. However, the global character inherent to the limited number of modal properties issued from operational modal analysis may be not appropriate for early-damage, which has generally a local character. The present paper aims at detecting this type of damage by using static SHM data and by assuming that early-damage produces dead load redistribution. To achieve this objective a data driven strategy is proposed, consisting of the combination of advanced statistical and machine learning methods such as principal component analysis, symbolic data analysis and cluster analysis. From this analysis it was observed that, under the noise levels measured on site, the proposed strategy is able to automatically detect stiffness reduction in stay cables reaching at least 1%.

关键词： structural health monitoring     early-damage detection     principal component analysis     symbolic data     symbolic dissimilarity measures     cluster analysis     numerical model     damage simulations    

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A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations

《化学科学与工程前沿（英文）》 2022年 第16卷 第6期   页码 874-885 doi: 10.1007/s11705-021-2131-1

摘要： The flow behaviours of cohesive particles in the ring shear test were simulated and examined using discrete element method guided by a design of experiments methodology. A full factorial design was used as a screening design to reveal the effects of material properties of partcles. An augmented design extending the screening design to a response surface design was constructed to establish the relations between macroscopic shear stresses and particle properties. It is found that the powder flow in the shear cell can be classified into four regimes. Shear stress is found to be sensitive to particle friction coefficient, surface energy and Young’s modulus. A considerable fluctuation of shear stress is observed in high friction and low cohesion regime. In high cohesion regime, Young’s modulus appears to have a more significant effect on the shear stress at the point of incipient flow than the shear stress during the pre-shear process. The predictions from response surface designs were validated and compared with shear stresses measured from the Schulze ring shear test. It is found that simulations and experiments showed excellent agreement under a variety of consolidation conditions, which verifies the advantages and feasibility of using the proposed “Sequential Design of Simulations” approach.

关键词： discrete element method     cohesive materials     parameter calibration     ring shear cell     design of experiments    

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Mean wind load induced incompatibility in nonlinear aeroelastic simulations of bridge spans

Zhitian ZHANG

《结构与土木工程前沿（英文）》 2019年 第13卷 第3期   页码 605-617 doi: 10.1007/s11709-018-0499-x

摘要： Mean wind response induced incompatibility and nonlinearity in bridge aerodynamics is discussed, where the mean wind and aeroelastic loads are applied simultaneously in time domain. A kind of incompatibility is found during the simultaneous simulation of the mean wind and aeroelastic loads, which leads to incorrect mean wind structural responses. It is found that the mathematic expectations (or limiting characteristics) of the aeroelastic models are fundamental to this kind of incompatibility. In this paper, two aeroelastic models are presented and discussed, one of indicial-function-denoted (IF-denoted) and another of rational-function-denoted (RF-denoted). It is shown that, in cases of low wind speeds, the IF-denoted model reflects correctly the mean wind load properties, and results in correct mean structural responses; in contrast, the RF-denoted model leads to incorrect mean responses due to its nonphysical mean properties. At very high wind speeds, however, even the IF-denoted model can lead to significant deviation from the correct response due to steady aerodynamic nonlinearity. To solve the incompatibility at high wind speeds, a methodology of subtraction of pseudo-steady effects from the aeroelastic model is put forward in this work. Finally, with the method presented, aeroelastic nonlinearity resulted from the mean wind response is investigated at both moderate and high wind speeds.

关键词： bridge     aerodynamics     nonlinear     aeroelastic model     Pseudo-steady     mean wind loads    

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Molecular level simulations on multi-component systems —a morphology prediction method

C. SCHMIDT, J. ULRICH

《化学科学与工程前沿（英文）》 2013年 第7卷 第1期   页码 49-54 doi: 10.1007/s11705-013-1307-8

摘要： The crystal morphology grown from a solution composed of an organic solvent, solute and additive can be predicted reliably by a computational method. Modeling the supersaturated solution as liquid phase is achieved by employing commercial software. The molecular composition of this solution is a required input parameter. The face specific diffusion coefficient of the solid (crystal surface) and liquid (solution) system is determined using the molecular dynamics procedure. The obtained diffusion coefficient is related to the specific face growth rate via the attachment energy of the pure morphology. The significant improvements are achieved in the morphology prediction because the investigation on the face growth rates in a complex growth environment (as multi-component solutions with additives) can be carried out based on the diffusion coefficients.

关键词： crystallization     morphology     molecular dynamics     solution    

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machine learning models to explore the solution space of large nonlinear systems underlying flowsheet simulations

《化学科学与工程前沿（英文）》 2022年 第16卷 第2期   页码 183-197 doi: 10.1007/s11705-021-2073-7

摘要： Flowsheet simulations of chemical processes on an industrial scale require the solution of large systems of nonlinear equations, so that solvability becomes a practical issue. Additional constraints from technical, economic, environmental, and safety considerations may further limit the feasible solution space beyond the convergence requirement. A priori, the design variable domains for which a simulation converges and fulfills the imposed constraints are usually unknown and it can become very time-consuming to distinguish feasible from infeasible design variable choices by simply running the simulation for each choice. To support the exploration of the design variable space for such scenarios, an adaptive sampling technique based on machine learning models has recently been proposed. However, that approach only considers the exploration of the convergent domain and ignores additional constraints. In this paper, we present an improvement which particularly takes the fulfillment of constraints into account. We successfully apply the proposed algorithm to a toy example in up to 20 dimensions and to an industrially relevant flowsheet simulation.

关键词： machine learning     flowsheet simulations     constraints     exploration    

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Kinetic Monte Carlo simulations of plasma-surface reactions on heterogeneous surfaces

Daniil Marinov

《化学科学与工程前沿（英文）》 2019年 第13卷 第4期   页码 815-822 doi: 10.1007/s11705-019-1837-9

摘要： Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications. Plasma-surface interactions are complex and relatively poorly understood. Experiments performed over the last decade by several groups prove that interactions of reactive species with relevant plasma-facing materials are characterized by distributions of adsorption energy and reactivity. In this paper, we develop a kinetic Monte Carlo (KMC) model that can effectively handle chemical kinetics on such heterogenous surfaces. Using this model, we analyse published adsorption-desorption kinetics of chlorine molecules and recombination of oxygen atoms on rotating substrates as a test case for the KMC model.

关键词： plasma-surface interaction     kinetic Monte Carlo     plasma nano technology    

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Atomistic simulations of plasma catalytic processes

Erik C. Neyts

《化学科学与工程前沿（英文）》 2018年 第12卷 第1期   页码 145-154 doi: 10.1007/s11705-017-1674-7

摘要： There is currently a growing interest in the realisation and optimization of hybrid plasma/catalyst systems for a multitude of applications, ranging from nanotechnology to environmental chemistry. In spite of this interest, there is, however, a lack in fundamental understanding of the underlying processes in such systems. While a lot of experimental research is already being carried out to gain this understanding, only recently the first simulations have appeared in the literature. In this contribution, an overview is presented on atomic scale simulations of plasma catalytic processes as carried out in our group. In particular, this contribution focusses on plasma-assisted catalyzed carbon nanostructure growth, and plasma catalysis for greenhouse gas conversion. Attention is paid to what can routinely be done, and where challenges persist.

关键词： atomic scale simulation     plasma-catalyst    

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Windborne debris damage prediction analysis

Fangfang SONG, Jinping OU,

《结构与土木工程前沿（英文）》 2010年 第4卷 第3期   页码 326-330 doi: 10.1007/s11709-010-0067-5

摘要： Windborne debris is one of the most important causes of the envelop destruction according to the post-damage investigations. The problem of windborne debris damage could be summarized as three parts, including windborne debris risk analysis, debris flying trajectories, and impact resistance of envelope analysis. The method of debris distribution is developed. The flying trajectories of compact and plate-like debris are solved by using a numerical method according to the different aerodynamic characteristics. The impact resistance of the envelopes is also analyzed. Besides, the process of windborne debris damage analysis is described in detail. An example of industrial building is given to demonstrate the whole method by using the observed data of typhoon Chanchu (2006). The method developed in this paper could be applied to risk assessment of windborne debris for structures in wind hazard.

关键词： typhoon     windborne debris     structural envelopes     damage estimation    

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Corrosion damage assessment and monitoring of large steel space structures

Bo CHEN, You-Lin XU, Weilian QU,

《结构与土木工程前沿（英文）》 2010年 第4卷 第3期   页码 354-369 doi: 10.1007/s11709-010-0088-0

摘要： Large steel space structures, when exposed to a harsh corrosive environment, are inevitably subjected to atmospheric corrosion and stress corrosion cracking. This paper proposes a framework for assessing the corrosion damage of large steel space structures subjected to both stress corrosion cracking and atmospheric corrosion. The empirical model for estimating atmospheric corrosion based on measured information is briefly introduced. The proposed framework is applied to a real large steel space structure built in the southern coastal area in China to assess its corrosion damage and investigate the effects of atmospheric corrosion on stress corrosion cracking. Based on the results, the conceptual design of the corrosion monitoring system of large steel space structures is finally conducted as the first step for a real corrosion monitoring system.

关键词： large steel space structure     atmospheric corrosion     stress corrosion cracking     corrosion damage     damage assessment     monitoring system    

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Latest progress in numerical simulations on multiphase flow and thermodynamics in production of natural

Lin ZUO, Lixia SUN, Changfu YOU

《能源前沿（英文）》 2009年 第3卷 第2期   页码 152-159 doi: 10.1007/s11708-009-0017-x

摘要： Natural gas hydrates are promising potential alternative energy resources. Some studies on the multiphase flow and thermodynamics have been conducted to investigate the feasibility of gas production from hydrate dissociation. The methods for natural gas production are analyzed and several models describing the dissociation process are listed and compared. Two prevailing models, one for depressurization and the other for thermal stimulation, are discussed in detail. A comprehensive numerical method considering the multiphase flow and thermodynamics of gas production from various hydrate-bearing reservoirs is required to better understand the dissociation process of natural gas hydrate, which would be of great benefit to its future exploration and exploitation.

关键词： numerical simulation     natural gas hydrate     dissociation     thermodynamics     multiphase flow    

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Detection of damage locations and damage steps in pile foundations using acoustic emissions with deep

Alipujiang JIERULA, Tae-Min OH, Shuhong WANG, Joon-Hyun LEE, Hyunwoo KIM, Jong-Won LEE

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 318-332 doi: 10.1007/s11709-021-0715-y

摘要： The aim of this study is to propose a new detection method for determining the damage locations in pile foundations based on deep learning using acoustic emission data. First, the damage location is simulated using a back propagation neural network deep learning model with an acoustic emission data set acquired from pile hit experiments. In particular, the damage location is identified using two parameters: the pile location ( ) and the distance from the pile cap ( ). This study investigates the influences of various acoustic emission parameters, numbers of sensors, sensor installation locations, and the time difference on the prediction accuracy of and . In addition, correlations between the damage location and acoustic emission parameters are investigated. Second, the damage step condition is determined using a classification model with an acoustic emission data set acquired from uniaxial compressive strength experiments. Finally, a new damage detection and evaluation method for pile foundations is proposed. This new method is capable of continuously detecting and evaluating the damage of pile foundations in service.

关键词： pile foundations     damage location     acoustic emission     deep learning     damage step    

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Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

《机械工程前沿（英文）》 2007年 第2卷 第4期   页码 399-403 doi: 10.1007/s11465-007-0069-8

摘要： Fracture is a common defect in sheet metal forming and it is essentially caused by tensile instability. This paper analyzes some experiments and theories for building forming limit diagrams of sheet metal and points out the advantages and disadvantages of current experiments and theories. According to this, a method that integrates the finite element simulation and experiment was used to research the forming limit diagrams of the sheet metal under complex strain paths. Taking the rear hanger that undergoes twice stamping as an example, the strain paths of the dangerous point of the rear hanger is investigated. Finally, the forming method of the rear hanger is confirmed. Results indicate that finite element method (FEM) can achieve the complex strain paths and different strain paths will have great impacts on the result of the sheet metal forming.

关键词： dangerous     forming method     different     hanger     forming    

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Improving simulations of sulfate aerosols during winter haze over Northern China: the impacts of heterogeneous

Meng Gao,Gregory R. Carmichael,Yuesi Wang,Dongsheng Ji,Zirui Liu,Zifa Wang

《环境科学与工程前沿（英文）》 2016年 第10卷 第5期 doi: 10.1007/s11783-016-0878-2

摘要： Incorporating the missing heterogeneous oxidation of S(IV) by NO into the WRF-Chem model. Sulfate production is not sensitive to increase in SO emission. The newly added reaction reproduces sulfate concentrations well during winter haze. We implemented the online coupled WRF-Chem model to reproduce the 2013 January haze event in North China, and evaluated simulated meteorological and chemical fields using multiple observations. The comparisons suggest that temperature and relative humidity (RH) were simulated well (mean biases are -0.2K and 2.7%, respectively), but wind speeds were overestimated (mean bias is 0.5 m?s ). At the Beijing station, sulfur dioxide (SO ) concentrations were overpredicted and sulfate concentrations were largely underpredicted, which may result from uncertainties in SO emissions and missing heterogeneous oxidation in current model. We conducted three parallel experiments to examine the impacts of doubling SO emissions and incorporating heterogeneous oxidation of dissolved SO by nitrogen dioxide (NO ) on sulfate formation during winter haze. The results suggest that doubling SO emissions do not significantly affect sulfate concentrations, but adding heterogeneous oxidation of dissolved SO by NO substantially improve simulations of sulfate and other inorganic aerosols. Although the enhanced SO to sulfate conversion in the HetS (heterogeneous oxidation by NO ) case reduces SO concentrations, it is still largely overestimated by the model, indicating the overestimations of SO concentrations in the North China Plain (NCP) are mostly due to errors in SO emission inventory.

关键词： Sulfate aerosols     Winter haze     WRF-Chem     Northern China    

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Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0702-6

摘要： The creep life of an aeroengine recuperator is investigated in terms of continuum damage mechanics by using finite element simulations. The effects of the manifold wall thickness and creep properties of brazing filler metal on the operating life of the recuperator are analyzed. Results show that the crack initiates from the brazing filler metal located on the outer surface of the manifold with the wall thickness of 2 mm and propagates throughout the whole region of the brazing filler metal when the creep time reaches 34900 h. The creep life of the recuperator meets the requirement of 40000 h continuous operation when the wall thickness increases to 3.5 mm, but its total weight increases by 15%. Decreasing the minimum creep strain rate with the enhancement of the creep strength of the brazing filler metal presents an obvious effect on the creep life of the recuperator. At the same stress level, the creep rupture time of the recuperator is enhanced by 13 times if the mismatch between the minimum creep rate of the filler and base metal is reduced by 20%.

关键词： creep     life assessment     brazed joint     continuum damage mechanics     aeroengine recuperator    

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Bacterial inactivation, DNA damage, and faster ATP degradation induced by ultraviolet disinfection

Chao Yang, Wenjun Sun, Xiuwei Ao

《环境科学与工程前沿（英文）》 2020年 第14卷 第1期 doi: 10.1007/s11783-019-1192-6

摘要： • Long amplicon is more effective to test DNA damage induced by UV. • ATP in bacteria does not degrade instantly but does eventually after UV exposure. • After medium pressure UV exposure, ATP degraded faster. The efficacy of ultraviolet (UV) disinfection has been validated in numerous studies by using culture-based methods. However, the discovery of viable but non-culturable bacteria has necessitated the investigation of UV disinfection based on bacterial viability parameters. We used quantitative polymerase chain reaction (qPCR) to investigate DNA damage and evaluated adenosine triphosphate (ATP) to indicate bacterial viability. The results of qPCR effectively showed the DNA damage induced by UV when using longer gene amplicons, in that sufficiently long amplicons of both 16S and gadA indicated that the UV induced DNA damages. The copy concentrations of the long amplicons of 16S and gadA decreased by 2.38 log/mL and 1.88 log/mL, respectively, after exposure to 40 mJ/cm2 low-pressure UV. After UV exposure, the ATP level in the bacteria did not decrease instantly. Instead it decreased gradually at a rate that was positively related to the UV fluence. For low-pressure UV, this rate of decrease was slow, but for medium pressure UV, this rate of decrease was relatively high when the UV fluence reached 40 mJ/cm2. At the same UV fluence, the ATP level in the bacteria decreased at a faster rate after exposure to medium-pressure UV.

关键词： UV disinfection     DNA damage     qPCR     ATP    

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标题 作者 时间 类型 操作

Static-based early-damage detection using symbolic data analysis and unsupervised learning methods

João Pedro SANTOS,Christian CREMONA,André D. ORCESI,Paulo SILVEIRA,Luis CALADO

期刊论文

A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations

期刊论文

Mean wind load induced incompatibility in nonlinear aeroelastic simulations of bridge spans

Zhitian ZHANG

期刊论文

Molecular level simulations on multi-component systems —a morphology prediction method

C. SCHMIDT, J. ULRICH

期刊论文

machine learning models to explore the solution space of large nonlinear systems underlying flowsheet simulations

期刊论文

Kinetic Monte Carlo simulations of plasma-surface reactions on heterogeneous surfaces

Daniil Marinov

期刊论文

Atomistic simulations of plasma catalytic processes

Erik C. Neyts

期刊论文

Windborne debris damage prediction analysis

Fangfang SONG, Jinping OU,

期刊论文

Corrosion damage assessment and monitoring of large steel space structures

Bo CHEN, You-Lin XU, Weilian QU,

期刊论文

Latest progress in numerical simulations on multiphase flow and thermodynamics in production of natural

Lin ZUO, Lixia SUN, Changfu YOU

期刊论文

Detection of damage locations and damage steps in pile foundations using acoustic emissions with deep

Alipujiang JIERULA, Tae-Min OH, Shuhong WANG, Joon-Hyun LEE, Hyunwoo KIM, Jong-Won LEE

期刊论文

Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

期刊论文

Improving simulations of sulfate aerosols during winter haze over Northern China: the impacts of heterogeneous

Meng Gao,Gregory R. Carmichael,Yuesi Wang,Dongsheng Ji,Zirui Liu,Zifa Wang

期刊论文

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

期刊论文

Bacterial inactivation, DNA damage, and faster ATP degradation induced by ultraviolet disinfection

Chao Yang, Wenjun Sun, Xiuwei Ao

期刊论文