Parameter identification, model calibration, and uncertainty quantification are important steps in the model-building process, and are necessary for obtaining credible results and valuable information. Sensitivity ana...Parameter identification, model calibration, and uncertainty quantification are important steps in the model-building process, and are necessary for obtaining credible results and valuable information. Sensitivity analysis of hydrological model is a key step in model uncertainty quantification, which can identify the dominant parameters, reduce the model calibration uncertainty, and enhance the model optimization efficiency. There are, however, some shortcomings in classical approaches, including the long duration of time and high computation cost required to quantitatively assess the sensitivity of a multiple-parameter hydrological model. For this reason, a two-step statistical evaluation framework using global techniques is presented. It is based on （1） a screening method （Morris） for qualitative ranking of parameters, and （2） a variance-based method integrated with a meta-model for quantitative sensitivity analysis, i.e., the Sobol method integrated with the response surface model （RSMSobol）. First, the Morris screening method was used to qualitatively identify the parameters＇ sensitivity, and then ten parameters were selected to quantify the sensitivity indices. Subsequently, the RSMSobol method was used to quantify the sensitivity, i.e., the first-order and total sensitivity indices based on the response surface model （RSM） were calculated. The RSMSobol method can not only quantify the sensitivity, but also reduce the computational cost, with good accuracy compared to the classical approaches. This approach will be effective and reliable in the global sensitivity analysis of a complex large-scale distributed hydrological model.展开更多
Conventional trajectory optimization techniques have been challenged by their inability to handle threats with irregular shapes and the tendency to be sensitive to control variations of aircraft. Aiming to overcome th...Conventional trajectory optimization techniques have been challenged by their inability to handle threats with irregular shapes and the tendency to be sensitive to control variations of aircraft. Aiming to overcome these difficulties, this paper presents an alternative approach for trajectory optimization, where the problem is formulated into a parametric optimization of the maneuver variables under a tactics template framework. To reduce the size of the problem, global sensitivity analysis （GSA） is performed to identify the less-influential maneuver variables. The probability collectives （PC） algorithm, which is well-suited to discrete and discontinuous optimization, is applied to solve the trajectory optimization problem. The robustness of the trajectory is assessed through multiple sampling around the chosen values of the maneuver variables. Meta-models based on radius basis function （RBF） are created for evaluations of the means and deviations of the problem objectives and constraints. To guarantee the approximation accuracy, the meta-models are adaptively updated during optimization. The proposed approach is demonstrated on a typical airground attack mission scenario. Results reveal that the proposed approach is capable of generating robust and optimal trajectories with both accuracy and efficiency.展开更多
In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. ...In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. The proposed method is rigorous and efficient compared to a typical conversion method which merely computes surface integration of solid element nodal stresses to obtain cross-sectional forces. The meta-modeling theory ensures the rigorousness of proposed method by defining a proper distance between beam element and solid element solutions in a function space of continuum mechanics. Results of numerical verification test that is conducted with a simple cantilever beam are used to find the proper distance function for this conversion. Time history analysis of the main tunnel structure of a real ramp tunnel is considered as a numerical example for the proposed conversion method. It is shown that cross-sectional forces are readily computed for solid element solution of the main tunnel structure when it is converted to a beam element solution using the proposed method. Further, envelopes of resultant forces which are of primary importance for the purpose of design, are developed for a given ground motion at the end.展开更多
To investigate the application of meta-model for finite element( FE) model updating of structures,the performance of two popular meta-model,i. e.,Kriging model and response surface model( RSM),were compared in detail....To investigate the application of meta-model for finite element( FE) model updating of structures,the performance of two popular meta-model,i. e.,Kriging model and response surface model( RSM),were compared in detail. Firstly,above two kinds of meta-model were introduced briefly. Secondly,some key issues of the application of meta-model to FE model updating of structures were proposed and discussed,and then some advices were presented in order to select a reasonable meta-model for the purpose of updating the FE model of structures. Finally,the procedure of FE model updating based on meta-model was implemented by updating the FE model of a truss bridge model with the measured modal parameters. The results showed that the Kriging model was more proper for FE model updating of complex structures.展开更多
In this work,a hybrid meta-model based design space differentiation（HMDSD）method is proposed for practical problems.In the proposed method,an iteratively reduced promising region is constructed using the expensive p...In this work,a hybrid meta-model based design space differentiation（HMDSD）method is proposed for practical problems.In the proposed method,an iteratively reduced promising region is constructed using the expensive points,with two different search strategies respectively applied inside and outside the promising region.Besides,the hybrid meta-model strategy applied in the search process makes it possible to solve the complex practical problems.Tested upon a serial of benchmark math functions,the HMDSD method shows great efficiency and search accuracy.On top of that,a practical lightweight design demonstrates its superior performance.展开更多
Neural networks are being used to construct meta-models in numerical simulation of structures.In addition to network structures and training algorithms,training samples also greatly affect the accuracy of neural netwo...Neural networks are being used to construct meta-models in numerical simulation of structures.In addition to network structures and training algorithms,training samples also greatly affect the accuracy of neural network models.In this paper,some existing main sampling techniques are evaluated,including techniques based on experimental design theory, random selection,and rotating sampling.First,advantages and disadvantages of each technique are reviewed.Then,seven techniques are used to generate samples for training radial neural networks models for two benchmarks:an antenna model and an aircraft model.Results show that the uniform design,in which the number of samples and mean square error network models are considered,is the best sampling technique for neural network based meta-model building.展开更多
With increasing design demands of turbomachinery,stochastic flutter behavior has become more prominent and even appears a hazard to reliability and safety.Stochastic flutter assessment is an effective measure to quant...With increasing design demands of turbomachinery,stochastic flutter behavior has become more prominent and even appears a hazard to reliability and safety.Stochastic flutter assessment is an effective measure to quantify the failure risk and improve aeroelastic stability.However,for complex turbomachinery with multiple dynamic influencing factors(i.e.,aeroengine compressor with time-variant loads),the stochastic flutter assessment is hard to be achieved effectively,since large deviations and inefficient computing will be incurred no matter considering influencing factors at a certain instant or the whole time domain.To improve the assessing efficiency and accuracy of stochastic flutter behavior,a dynamic meta-modeling approach(termed BA-DWTR)is presented with the integration of bat algorithm(BA)and dynamic wavelet tube regression(DWTR).The stochastic flutter assessment of a typical compressor blade is considered as one case to evaluate the proposed approach with respect to condition variabilities and load fluctuations.The evaluation results reveal that the compressor blade has 0.95% probability to induce flutter failure when operating 100% rotative rate at t=170 s.The total temperature at rotor inlet and dynamic operating loads(vibrating frequency and rotative rate)are the primary sensitive parameters on flutter failure probability.Bymethod comparisons,the presented approach is validated to possess high-accuracy and highefficiency in assessing the stochastic flutter behavior for turbomachinery.展开更多
Our research focuses on creating a meta-model for generating a web mapping application. It was difficult for non-geomatics developers to implement a webmapping application. Indeed, this type of application uses geospa...Our research focuses on creating a meta-model for generating a web mapping application. It was difficult for non-geomatics developers to implement a webmapping application. Indeed, this type of application uses geospatial data that require geomatics skills. For this reason, in order to help non-geomatics developers to set up a webmapping application, we have designed a meta-model that automatically generates a webmapping application using model-driven engineering. The created meta-model is used by non-geomatics developers to explicitly write the concrete syntax specific to the webmapping application using the xtext tool. This concrete syntax is automatically converted into source code using the xtend tool without the intervention of the non-geomatics developers.展开更多
Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEB...Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEBNF syntax definition, a formal predicate logic language can be induced so that meta-modelling can be performed formally by spec- ifying a predicate on the domain of syntactically valid mod- els. In this paper, we investigate the theoretical foundation of this meta-modelling approach. We formally define the se- mantics of GEBNF and its induced predicate logic languages, then apply Goguen and Burstall＇s institution theory to prove that they form a sound and valid formal specification lan- guage for meta-modelling.展开更多
Due to the good balance between high efficiency and accuracy, meta-model based optimization algorithm is an important global optimization category and has been widely applied. To better solve the highly nonlinear and ...Due to the good balance between high efficiency and accuracy, meta-model based optimization algorithm is an important global optimization category and has been widely applied. To better solve the highly nonlinear and computation intensive en- gineering optimization problems, an enhanced hybrid and adaptive meta-model based global optimization （E-HAM） is first proposed in this work. Important region update method （IRU） and different sampling size strategies are proposed in the opti- mization method to enhance the performance. By applying self-moving and scaling strategy, the important region will be up- dated adaptively according to the search results to improve the resulting precision and convergence rate. Rough sampling strategy and intensive sampling strategy are applied at different stages of the optimization to improve the search efficiently and avoid results prematurely gathering in a small design space. The effectiveness of the new optimization algorithm is verified by comparing to six optimization methods with different variables bench mark optimization problems. The E-HAM optimization method is then applied to optimize the design parameters of the practical negative Poisson＇s ratio （NPR） crash box in this work. The results indicate that the proposed E-HAM has high accuracy and efficiency in optimizing the computation intensive prob- lems and can be widely used in engineering industry.展开更多
This paper presents a model-driven 3G service creation approach based on model driven architecture technology. The focus of the paper is the methodology of designing telecommunication service-related meta-model and it...This paper presents a model-driven 3G service creation approach based on model driven architecture technology. The focus of the paper is the methodology of designing telecommunication service-related meta-model and its profile implementation mechanism. This approach enhances the reusability of applications through separation of service logic models from concrete open application programming interface technologies and implementation technologies.展开更多
Three uncertain parameters(peak ground acceleration,soil density,and soil modulus of elasticity)have been studied with regard to their effects on the stability and damage of a circular tunnel during an earthquake.A ti...Three uncertain parameters(peak ground acceleration,soil density,and soil modulus of elasticity)have been studied with regard to their effects on the stability and damage of a circular tunnel during an earthquake.A time history of an actual earthquake in the literature with modification has been adopted in the numerical simulation and analysis of the tunnel responses.Meta-models have been constructed based on an experimental method with quadratic and interaction terms using matlab codes in order to predict the compressive damage,tensile damage,and the overall displacement of the tunnel.The results of the meta-models predicted a highly reasonable response of the tunnel with regard to the maximum principal stresses in the tunnel lining and predicted a remarkable response of the tunnel with respect to the overall displacement of the tunnel.Moreover,the peak ground acceleration was observed to exert the highest effect on the overall displacement of the tunnel,compared to the soil density and soil modulus of elasticity.Furthermore,the metamodels revealed the inverse relationship between the soil modulus of elasticity and the compressive and tensile damages of the tunnel lining.The meta-models exhibited high efficiency of representation of the behavior of the structural system during earthquakes.展开更多
目的:创伤后癫痫(post-traumatic epilepsy,PTE)是创伤性脑损伤(traumatic brain injury,TBI)的常见并发症,严重影响患者预后,早期预测PTE风险对临床管理至关重要,相比成人,儿童PTE相关研究较少,且缺乏临床公认的高预测效能模型。本研...目的:创伤后癫痫(post-traumatic epilepsy,PTE)是创伤性脑损伤(traumatic brain injury,TBI)的常见并发症,严重影响患者预后,早期预测PTE风险对临床管理至关重要,相比成人,儿童PTE相关研究较少,且缺乏临床公认的高预测效能模型。本研究旨在构建并验证适用于儿童TBI患者的PTE风险预测列线图模型。方法:系统检索中国知网、万方、中国生物医学文献数据库、维普、Pubmed、Embase和Web of Science数据库中关于儿童PTE危险因素的研究,检索时限为建库至2024年10月。采用Stata 15.0软件进行Meta分析,根据Meta分析结果提取合并效应量具有显著性的风险因素。回顾性收集2019年1月—2023年12月南京医科大学附属儿童医院外科重症监护病房(surgical intensive care unit,SICU)收治的262例TBI患儿,按7∶3比例随机划分为训练队列和内部验证队列,基于Meta分析筛选的危险因素,利用R软件构建多因素Logistic回归模型并绘制列线图。采用受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)评价模型区分度,Hosmer-Lemeshow检验评估校准度,运用决策曲线分析(decision curve analysis,DCA)评估临床实用性。结果:共纳入13项研究,涉及1371819例TBI患儿。Meta分析显示,中国TBI儿童中PTE的发病率为19%(95%CI:17%~20%)。结合Meta分析筛选结果和临床经验,最终纳入8个危险因素构建模型:格拉斯哥昏迷量表(Glasgow coma scale,GCS)评分、开放性脑损伤、早期痫性发作、意识丧失以及异常颅脑影像学表现(颅内血肿、脑挫伤、硬膜下出血、蛛网膜下腔出血),预测模型在训练队列和内部验证队列的AUC分别为0.801(95%CI:0.735~0.867,P<0.05)和0.831(95%CI:0.728~0.934,P<0.05)。Hosmer-Lemeshow拟合优度检验示模型拟合良好(训练队列:P=0.079;验证队列:P=0.082)。DCA显示该模型具有较高临床净获益。结论:本研究基于Meta分析构建的儿童PTE风险预测模型具有良好的区分度、校准度和临床实用性,可作为TBI儿童发生PTE风险评估的有效工具。展开更多
Enterprise systems must have the structure to adapt the change of business environment. When rebuilding enterprise system to meet the extended operational boundaries, the concept of IT city planning is applicable and ...Enterprise systems must have the structure to adapt the change of business environment. When rebuilding enterprise system to meet the extended operational boundaries, the concept of IT city planning is applicable and effective. The aim of this paper is to describe the architectural approach from the integrated information infrastructure (In3) standpoint and to propose for applying the 'City Planning' concept for rebuilding 'inter-application spaghetti' enterprise systems. This is mainly because the portion of infrastructure has increased with the change of information systems from centralized systems to distributed and open systems. As enterprise systems have involved heterogeneity or architectural black box in them, it may be required the integration framework (meta-architecture) as a discipline based on heterogeneity that can provide comprehensive view of the enterprise systems. This paper proposes 'EII Meta-model' as the integration framework that can optimize the overall enterprise systems from the IT city planning point of view. EII Meta-model consists of 'Integrated Information Infrastructure Map (In3-Map)', 'Service Framework' and 'IT Scenario'. It would be applicable and effective for the viable enterprise, because it has the mechanism to adapt the change. Finally, we illustrate a case of information system in an online securities company and demonstrate applicability and effectiveness of EII Meta-model to meet their business goals.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 41271003)the National Basic Research Program of China (Grants No. 2010CB428403 and 2010CB951103)
文摘Parameter identification, model calibration, and uncertainty quantification are important steps in the model-building process, and are necessary for obtaining credible results and valuable information. Sensitivity analysis of hydrological model is a key step in model uncertainty quantification, which can identify the dominant parameters, reduce the model calibration uncertainty, and enhance the model optimization efficiency. There are, however, some shortcomings in classical approaches, including the long duration of time and high computation cost required to quantitatively assess the sensitivity of a multiple-parameter hydrological model. For this reason, a two-step statistical evaluation framework using global techniques is presented. It is based on （1） a screening method （Morris） for qualitative ranking of parameters, and （2） a variance-based method integrated with a meta-model for quantitative sensitivity analysis, i.e., the Sobol method integrated with the response surface model （RSMSobol）. First, the Morris screening method was used to qualitatively identify the parameters＇ sensitivity, and then ten parameters were selected to quantify the sensitivity indices. Subsequently, the RSMSobol method was used to quantify the sensitivity, i.e., the first-order and total sensitivity indices based on the response surface model （RSM） were calculated. The RSMSobol method can not only quantify the sensitivity, but also reduce the computational cost, with good accuracy compared to the classical approaches. This approach will be effective and reliable in the global sensitivity analysis of a complex large-scale distributed hydrological model.
基金supported by Open Research Foundation of Science and Technology on Aerospace Flight Dynamics Laboratory (No. 2012afd1010)
文摘Conventional trajectory optimization techniques have been challenged by their inability to handle threats with irregular shapes and the tendency to be sensitive to control variations of aircraft. Aiming to overcome these difficulties, this paper presents an alternative approach for trajectory optimization, where the problem is formulated into a parametric optimization of the maneuver variables under a tactics template framework. To reduce the size of the problem, global sensitivity analysis （GSA） is performed to identify the less-influential maneuver variables. The probability collectives （PC） algorithm, which is well-suited to discrete and discontinuous optimization, is applied to solve the trajectory optimization problem. The robustness of the trajectory is assessed through multiple sampling around the chosen values of the maneuver variables. Meta-models based on radius basis function （RBF） are created for evaluations of the means and deviations of the problem objectives and constraints. To guarantee the approximation accuracy, the meta-models are adaptively updated during optimization. The proposed approach is demonstrated on a typical airground attack mission scenario. Results reveal that the proposed approach is capable of generating robust and optimal trajectories with both accuracy and efficiency.
文摘In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. The proposed method is rigorous and efficient compared to a typical conversion method which merely computes surface integration of solid element nodal stresses to obtain cross-sectional forces. The meta-modeling theory ensures the rigorousness of proposed method by defining a proper distance between beam element and solid element solutions in a function space of continuum mechanics. Results of numerical verification test that is conducted with a simple cantilever beam are used to find the proper distance function for this conversion. Time history analysis of the main tunnel structure of a real ramp tunnel is considered as a numerical example for the proposed conversion method. It is shown that cross-sectional forces are readily computed for solid element solution of the main tunnel structure when it is converted to a beam element solution using the proposed method. Further, envelopes of resultant forces which are of primary importance for the purpose of design, are developed for a given ground motion at the end.
基金Sponsored by the National Key Technology Research and Development Program of China(Grant No.2011BAK02B02)
文摘To investigate the application of meta-model for finite element( FE) model updating of structures,the performance of two popular meta-model,i. e.,Kriging model and response surface model( RSM),were compared in detail. Firstly,above two kinds of meta-model were introduced briefly. Secondly,some key issues of the application of meta-model to FE model updating of structures were proposed and discussed,and then some advices were presented in order to select a reasonable meta-model for the purpose of updating the FE model of structures. Finally,the procedure of FE model updating based on meta-model was implemented by updating the FE model of a truss bridge model with the measured modal parameters. The results showed that the Kriging model was more proper for FE model updating of complex structures.
基金Project supported by the Plan for the growth of young teachers,the National Natural Science Foundation of China(No.51505138)the National 973 Program of China(No.2010CB328005)+1 种基金Outstanding Youth Foundation of NSFC(No.50625519)Program for Changjiang Scholars
文摘In this work,a hybrid meta-model based design space differentiation（HMDSD）method is proposed for practical problems.In the proposed method,an iteratively reduced promising region is constructed using the expensive points,with two different search strategies respectively applied inside and outside the promising region.Besides,the hybrid meta-model strategy applied in the search process makes it possible to solve the complex practical problems.Tested upon a serial of benchmark math functions,the HMDSD method shows great efficiency and search accuracy.On top of that,a practical lightweight design demonstrates its superior performance.
基金Specialized Research Fund for the Doctoral Program of Higher Education,China (No.20010227012)
文摘Neural networks are being used to construct meta-models in numerical simulation of structures.In addition to network structures and training algorithms,training samples also greatly affect the accuracy of neural network models.In this paper,some existing main sampling techniques are evaluated,including techniques based on experimental design theory, random selection,and rotating sampling.First,advantages and disadvantages of each technique are reviewed.Then,seven techniques are used to generate samples for training radial neural networks models for two benchmarks:an antenna model and an aircraft model.Results show that the uniform design,in which the number of samples and mean square error network models are considered,is the best sampling technique for neural network based meta-model building.
基金co-supported by the National Natural Science Foundation of China(Grants 51975028 and 52105136)China Postdoctoral Science Foundation(Grant 2021M690290)the National Science and TechnologyMajor Project(Grant J2019-Ⅳ-0016-0084).
文摘With increasing design demands of turbomachinery,stochastic flutter behavior has become more prominent and even appears a hazard to reliability and safety.Stochastic flutter assessment is an effective measure to quantify the failure risk and improve aeroelastic stability.However,for complex turbomachinery with multiple dynamic influencing factors(i.e.,aeroengine compressor with time-variant loads),the stochastic flutter assessment is hard to be achieved effectively,since large deviations and inefficient computing will be incurred no matter considering influencing factors at a certain instant or the whole time domain.To improve the assessing efficiency and accuracy of stochastic flutter behavior,a dynamic meta-modeling approach(termed BA-DWTR)is presented with the integration of bat algorithm(BA)and dynamic wavelet tube regression(DWTR).The stochastic flutter assessment of a typical compressor blade is considered as one case to evaluate the proposed approach with respect to condition variabilities and load fluctuations.The evaluation results reveal that the compressor blade has 0.95% probability to induce flutter failure when operating 100% rotative rate at t=170 s.The total temperature at rotor inlet and dynamic operating loads(vibrating frequency and rotative rate)are the primary sensitive parameters on flutter failure probability.Bymethod comparisons,the presented approach is validated to possess high-accuracy and highefficiency in assessing the stochastic flutter behavior for turbomachinery.
文摘Our research focuses on creating a meta-model for generating a web mapping application. It was difficult for non-geomatics developers to implement a webmapping application. Indeed, this type of application uses geospatial data that require geomatics skills. For this reason, in order to help non-geomatics developers to set up a webmapping application, we have designed a meta-model that automatically generates a webmapping application using model-driven engineering. The created meta-model is used by non-geomatics developers to explicitly write the concrete syntax specific to the webmapping application using the xtext tool. This concrete syntax is automatically converted into source code using the xtend tool without the intervention of the non-geomatics developers.
文摘Meta-modelling plays an important role in model driven software development. In this paper, a graphic exten- sion of BNF （GEBNF） is proposed to define the abstract syn- tax of graphic modelling languages. From a GEBNF syntax definition, a formal predicate logic language can be induced so that meta-modelling can be performed formally by spec- ifying a predicate on the domain of syntactically valid mod- els. In this paper, we investigate the theoretical foundation of this meta-modelling approach. We formally define the se- mantics of GEBNF and its induced predicate logic languages, then apply Goguen and Burstall＇s institution theory to prove that they form a sound and valid formal specification lan- guage for meta-modelling.
基金supported by the Research Project of State Key Laboratory of Mechanical System and Vibration(Grant Nos.MSV201507&MSV201606)the National Natural Science Foundation of China(Grant No.51375007)+3 种基金the Natural Science Foundation of Jiangsu Province(Grant No.SBK2015022352)the Fundamental Research Funds for the Central Universities(Grant No.NE2016002)the Open Fund Program of the State Key Laboratory of Vehicle Lightweight Design,P.R.China(Grant No.20130303)the Visiting Scholar Foundation of the State Key Lab of Mechanical Transmission in Chongqing University(Grant Nos.SKLMT-KFKT-2014010&SKLMT-KFKT-201507)
文摘Due to the good balance between high efficiency and accuracy, meta-model based optimization algorithm is an important global optimization category and has been widely applied. To better solve the highly nonlinear and computation intensive en- gineering optimization problems, an enhanced hybrid and adaptive meta-model based global optimization （E-HAM） is first proposed in this work. Important region update method （IRU） and different sampling size strategies are proposed in the opti- mization method to enhance the performance. By applying self-moving and scaling strategy, the important region will be up- dated adaptively according to the search results to improve the resulting precision and convergence rate. Rough sampling strategy and intensive sampling strategy are applied at different stages of the optimization to improve the search efficiently and avoid results prematurely gathering in a small design space. The effectiveness of the new optimization algorithm is verified by comparing to six optimization methods with different variables bench mark optimization problems. The E-HAM optimization method is then applied to optimize the design parameters of the practical negative Poisson＇s ratio （NPR） crash box in this work. The results indicate that the proposed E-HAM has high accuracy and efficiency in optimizing the computation intensive prob- lems and can be widely used in engineering industry.
文摘This paper presents a model-driven 3G service creation approach based on model driven architecture technology. The focus of the paper is the methodology of designing telecommunication service-related meta-model and its profile implementation mechanism. This approach enhances the reusability of applications through separation of service logic models from concrete open application programming interface technologies and implementation technologies.
文摘Three uncertain parameters(peak ground acceleration,soil density,and soil modulus of elasticity)have been studied with regard to their effects on the stability and damage of a circular tunnel during an earthquake.A time history of an actual earthquake in the literature with modification has been adopted in the numerical simulation and analysis of the tunnel responses.Meta-models have been constructed based on an experimental method with quadratic and interaction terms using matlab codes in order to predict the compressive damage,tensile damage,and the overall displacement of the tunnel.The results of the meta-models predicted a highly reasonable response of the tunnel with regard to the maximum principal stresses in the tunnel lining and predicted a remarkable response of the tunnel with respect to the overall displacement of the tunnel.Moreover,the peak ground acceleration was observed to exert the highest effect on the overall displacement of the tunnel,compared to the soil density and soil modulus of elasticity.Furthermore,the metamodels revealed the inverse relationship between the soil modulus of elasticity and the compressive and tensile damages of the tunnel lining.The meta-models exhibited high efficiency of representation of the behavior of the structural system during earthquakes.
文摘目的:创伤后癫痫(post-traumatic epilepsy,PTE)是创伤性脑损伤(traumatic brain injury,TBI)的常见并发症,严重影响患者预后,早期预测PTE风险对临床管理至关重要,相比成人,儿童PTE相关研究较少,且缺乏临床公认的高预测效能模型。本研究旨在构建并验证适用于儿童TBI患者的PTE风险预测列线图模型。方法:系统检索中国知网、万方、中国生物医学文献数据库、维普、Pubmed、Embase和Web of Science数据库中关于儿童PTE危险因素的研究,检索时限为建库至2024年10月。采用Stata 15.0软件进行Meta分析,根据Meta分析结果提取合并效应量具有显著性的风险因素。回顾性收集2019年1月—2023年12月南京医科大学附属儿童医院外科重症监护病房(surgical intensive care unit,SICU)收治的262例TBI患儿,按7∶3比例随机划分为训练队列和内部验证队列,基于Meta分析筛选的危险因素,利用R软件构建多因素Logistic回归模型并绘制列线图。采用受试者工作特征(receiver operating characteristic,ROC)曲线下面积(area under the curve,AUC)评价模型区分度,Hosmer-Lemeshow检验评估校准度,运用决策曲线分析(decision curve analysis,DCA)评估临床实用性。结果:共纳入13项研究,涉及1371819例TBI患儿。Meta分析显示,中国TBI儿童中PTE的发病率为19%(95%CI:17%~20%)。结合Meta分析筛选结果和临床经验,最终纳入8个危险因素构建模型:格拉斯哥昏迷量表(Glasgow coma scale,GCS)评分、开放性脑损伤、早期痫性发作、意识丧失以及异常颅脑影像学表现(颅内血肿、脑挫伤、硬膜下出血、蛛网膜下腔出血),预测模型在训练队列和内部验证队列的AUC分别为0.801(95%CI:0.735~0.867,P<0.05)和0.831(95%CI:0.728~0.934,P<0.05)。Hosmer-Lemeshow拟合优度检验示模型拟合良好(训练队列:P=0.079;验证队列:P=0.082)。DCA显示该模型具有较高临床净获益。结论:本研究基于Meta分析构建的儿童PTE风险预测模型具有良好的区分度、校准度和临床实用性,可作为TBI儿童发生PTE风险评估的有效工具。
文摘Enterprise systems must have the structure to adapt the change of business environment. When rebuilding enterprise system to meet the extended operational boundaries, the concept of IT city planning is applicable and effective. The aim of this paper is to describe the architectural approach from the integrated information infrastructure (In3) standpoint and to propose for applying the 'City Planning' concept for rebuilding 'inter-application spaghetti' enterprise systems. This is mainly because the portion of infrastructure has increased with the change of information systems from centralized systems to distributed and open systems. As enterprise systems have involved heterogeneity or architectural black box in them, it may be required the integration framework (meta-architecture) as a discipline based on heterogeneity that can provide comprehensive view of the enterprise systems. This paper proposes 'EII Meta-model' as the integration framework that can optimize the overall enterprise systems from the IT city planning point of view. EII Meta-model consists of 'Integrated Information Infrastructure Map (In3-Map)', 'Service Framework' and 'IT Scenario'. It would be applicable and effective for the viable enterprise, because it has the mechanism to adapt the change. Finally, we illustrate a case of information system in an online securities company and demonstrate applicability and effectiveness of EII Meta-model to meet their business goals.
