公共政策的学术研究同其他社会科学一样,都追求对因果机制的解释。然而,现实世界的公共政策过程往往非常复杂,传统的量化研究方法很难完全解释因果机制。近年来,因果过程追踪(Causal Process Tracing,简称CPT)作为一种基于溯因推理逻辑...公共政策的学术研究同其他社会科学一样,都追求对因果机制的解释。然而,现实世界的公共政策过程往往非常复杂,传统的量化研究方法很难完全解释因果机制。近年来,因果过程追踪(Causal Process Tracing,简称CPT)作为一种基于溯因推理逻辑的实证研究方法,在多方法研究(multi-method research)中得到越来越广泛的应用。该方法使用严密的案例内推断来追踪事件,透过过程分析撬开将原因和结果联系起来的因果机制,具有识别并纠正虚假因果关联以及遗漏变量偏误等内生性问题等方法论优势,有助于弥合质性研究和量化研究的鸿沟。因果过程追踪方法不受意识形态的限制,其包容的理论多元性为公共政策研究提供了独特的分析视角和框架,具有较高的推介价值。在梳理因果过程追踪方法发展脉络的基础上,本文选取了近期发表在著名国际学术期刊上的4篇关于因果过程追踪方法的学术论文,着重评介这一方法在公共政策学术研究中的价值和操作策略,以期推动中国公共政策研究的方法论多元化。展开更多
For complex chemical processes,process optimization is usually performed on causal models from first principle models.When the mechanism models cannot be obtained easily,restricted model built by process data is used ...For complex chemical processes,process optimization is usually performed on causal models from first principle models.When the mechanism models cannot be obtained easily,restricted model built by process data is used for dynamic process optimization.A new strategy is proposed for complex process optimization,in which latent variables are used as decision variables and statistics is used to describe constraints.As the constraint condition will be more complex by projecting the original variable to latent space,Hotelling T^2 statistics is introduced for constraint formulation in latent space.In this way,the constraint is simplified when the optimization is solved in low-dimensional space of latent variable.The validity of the methodology is illustrated in pH-level optimal control process and practical polypropylene grade transition process.展开更多
An integrated method for identifying the propagation of multi-loop process oscillations and their source location is proposed in this paper. Oscillatory process loop variables are automatically selected based on the c...An integrated method for identifying the propagation of multi-loop process oscillations and their source location is proposed in this paper. Oscillatory process loop variables are automatically selected based on the component-related ratio index and a mixing matrix, both of which are obtained in data preprocessing by spectral independent component analysis. The complex causality among oscillatory process variables is then revealed by Granger causality test and is visualized in the form of causality diagram. The simplification of causal connectivity in the diagram is performed according to the understanding of process knowledge and the final simplest causality diagram, which represents the main oscillation propagation paths, is achieved by the automated cutting-off thresh-old search, with which less significant causality pathways are filtered out. The source of the oscillation disturbance can be identified intuitively through the final causality diagram. Both simulated and real plant data tests are presented to demonstrate the effectiveness and feasibility of the proposed method.展开更多
In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke＇s peak factor is directly related to an explicit me...In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke＇s peak factor is directly related to an explicit measure of structural reliability against a Gaussian response process. We review the use of this factor for time-variant reliability design by comparing it to the conven- tional Davenport＇s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process. Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of the Common- wealth Advisory Aeronautical Research Council （CAARC） standard tall building to validate the applicability of the Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses for dynamic service- ability performance design of modem tall buildings.展开更多
文摘公共政策的学术研究同其他社会科学一样,都追求对因果机制的解释。然而,现实世界的公共政策过程往往非常复杂,传统的量化研究方法很难完全解释因果机制。近年来,因果过程追踪(Causal Process Tracing,简称CPT)作为一种基于溯因推理逻辑的实证研究方法,在多方法研究(multi-method research)中得到越来越广泛的应用。该方法使用严密的案例内推断来追踪事件,透过过程分析撬开将原因和结果联系起来的因果机制,具有识别并纠正虚假因果关联以及遗漏变量偏误等内生性问题等方法论优势,有助于弥合质性研究和量化研究的鸿沟。因果过程追踪方法不受意识形态的限制,其包容的理论多元性为公共政策研究提供了独特的分析视角和框架,具有较高的推介价值。在梳理因果过程追踪方法发展脉络的基础上,本文选取了近期发表在著名国际学术期刊上的4篇关于因果过程追踪方法的学术论文,着重评介这一方法在公共政策学术研究中的价值和操作策略,以期推动中国公共政策研究的方法论多元化。
基金Supported by the National Natural Science Foundation of China(61174114)the Research Fund for the Doctoral Program of Higher Education in China(20120101130016)+1 种基金the Natural Science Foundation of Zhejiang Province(LQ15F030006)the Educational Commission Research Program of Zhejiang Province(Y201431412)
文摘For complex chemical processes,process optimization is usually performed on causal models from first principle models.When the mechanism models cannot be obtained easily,restricted model built by process data is used for dynamic process optimization.A new strategy is proposed for complex process optimization,in which latent variables are used as decision variables and statistics is used to describe constraints.As the constraint condition will be more complex by projecting the original variable to latent space,Hotelling T^2 statistics is introduced for constraint formulation in latent space.In this way,the constraint is simplified when the optimization is solved in low-dimensional space of latent variable.The validity of the methodology is illustrated in pH-level optimal control process and practical polypropylene grade transition process.
基金Supported by the National Natural Science Foundation of China （60974061）.
文摘An integrated method for identifying the propagation of multi-loop process oscillations and their source location is proposed in this paper. Oscillatory process loop variables are automatically selected based on the component-related ratio index and a mixing matrix, both of which are obtained in data preprocessing by spectral independent component analysis. The complex causality among oscillatory process variables is then revealed by Granger causality test and is visualized in the form of causality diagram. The simplification of causal connectivity in the diagram is performed according to the understanding of process knowledge and the final simplest causality diagram, which represents the main oscillation propagation paths, is achieved by the automated cutting-off thresh-old search, with which less significant causality pathways are filtered out. The source of the oscillation disturbance can be identified intuitively through the final causality diagram. Both simulated and real plant data tests are presented to demonstrate the effectiveness and feasibility of the proposed method.
基金Project supported by the National Natural Science Foundation of China (No. 51008275)the China Postdoctoral Science Foundation (No.201104736)
文摘In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke＇s peak factor is directly related to an explicit measure of structural reliability against a Gaussian response process. We review the use of this factor for time-variant reliability design by comparing it to the conven- tional Davenport＇s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process. Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of the Common- wealth Advisory Aeronautical Research Council （CAARC） standard tall building to validate the applicability of the Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses for dynamic service- ability performance design of modem tall buildings.
