Optimization with Probabilistic Constraints

2011 ◽  
Author(s):  
Shabbir Ahmed
Keyword(s):  
Probabilistic Constraints

Optimization of Tube Hydroforming Process Using Probabilistic Constraints on Failure Modes

2011 ◽  
Vol 62 ◽  
pp. 21-35 ◽  
Author(s):  
Anis Ben Abdessalem ◽  
A. El Hami
Keyword(s):  
Failure Modes ◽  
High Reliability ◽  
Thickness Distribution ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Plastic Instability ◽  
Probabilistic Constraints ◽  
Forming Limit ◽  
Reliability Based Design ◽  
Hydroforming Process

In metal forming processes, different parameters (Material constants, geometric dimensions, loads …) exhibits unavoidable scatter that lead the process unreliable and unstable. In this paper, we interest particularly in tube hydroforming process (THP). This process consists to apply an inner pressure combined to an axial displacement to manufacture the part. During the manufacturing phase, inappropriate choice of the loading paths can lead to failure. Deterministic approaches are unable to optimize the process with taking into account to the uncertainty. In this work, we introduce the Reliability-Based Design Optimization (RBDO) to optimize the process under probabilistic considerations to ensure a high reliability level and stability during the manufacturing phase and avoid the occurrence of such plastic instability. Taking account of the uncertainty offer to the process a high stability associated with a low probability of failure. The definition of the objective function and the probabilistic constraints takes advantages from the Forming Limit Diagram (FLD) and the Forming Limit Stress Diagram (FLSD) used as a failure criterion to detect the occurrence of wrinkling, severe thinning, and necking. A THP is then introduced as an example to illustrate the proposed approach. The results show the robustness and efficiency of RBDO to improve thickness distribution and minimize the risk of potential failure modes.

Dynamic Optimization of Steel Catenary Risers Based on Reliability Using Metamodel

2010 ◽  
Author(s):  
Wenqing Zheng ◽  
Hezhen Yang
Keyword(s):  
Dynamic Optimization ◽  
Computational Cost ◽  
Minimum Cost ◽  
Probabilistic Constraints ◽  
Optimization Approach ◽  
Element Analysis ◽  
Steel Catenary Riser ◽  
Reliability Based Design ◽  
Minimum Cost Design ◽  
Steel Catenary Risers

Reliability based design optimization (RBDO) of a steel catenary riser (SCR) using metamodel is investigated. The purpose of the optimization is to find the minimum-cost design subjecting to probabilistic constraints. To reduce the computational cost of the traditional double-loop RBDO, a single-loop RBDO approach is employed. The performance function is approximated by using metamodel to avoid time consuming finite element analysis during the dynamic optimization. The metamodel is constructed though design of experiments (DOE) sampling. In addition, the reliability assessment is carried out by Monte Carlo simulations. The result shows that the RBDO of SCR is a more rational optimization approach compared with traditional deterministic optimization, and using metamodel technique during the dynamic optimization process can significantly decrease the computational expense without sacrificing accuracy.

scholarly journals Talking in another person’s shoes: Incremental perspective-taking in language processing

2011 ◽  
Vol 2 (1) ◽  
pp. 11-33 ◽  
Author(s):  
Sarah Brown-Schmidt ◽  
Joy E. Hanna
Keyword(s):  
Language Processing ◽  
Perspective Taking ◽  
Careful Consideration ◽  
Probabilistic Constraints ◽  
Sources Of Information ◽  
Visual World ◽  
Integration Model ◽  
Knowledge And Beliefs ◽  
On Line ◽  
Methodological Advance

Language use in conversation is fundamentally incremental, and is guided by the representations that interlocutors maintain of each other’s knowledge and beliefs. While there is a consensus that interlocutors represent the perspective of others, three candidate models, a Perspective-Adjustment model, an Anticipation-Integration model, and a Constraint-Based model, make conflicting predictions about the role of perspective information during on-line language processing. Here we review psycholinguistic evidence for incrementality in language processing, and the recent methodological advance that has fostered its investigation—the use of eye-tracking in the visual world paradigm. We present visual world studies of perspective-taking, and evaluate each model's account of the data. We argue for a Constraint-Based view in which perspective is one of multiple probabilistic constraints that guide language processing decisions. Addressees combine knowledge of a speaker’s perspective with rich information from the discourse context to arrive at an interpretation of what was said. Understanding how these sources of information combine to influence interpretation requires careful consideration of how perspective representations were established, and how they are relevant to the communicative context.

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