Topography Optimization of Shell Structures Under Transient Loading: A Comparative Approach

2012 ◽  
Author(s):  
Juan Camilo Medina ◽  
Andrés Tovar
Keyword(s):  
Sensitivity Analysis ◽  
Stochastic Approximation ◽  
State Of The Art ◽  
Computational Effort ◽  
Shell Structures ◽  
Comparative Approach ◽  
Shell Elements ◽  
Physical Approximation ◽  
Key Issues ◽  
Topography Optimization

Topography optimization is an innovative technique that can significantly improve the response of certain type of structures. The most challenging aspect of topography optimization is the sensitivity analysis. In this manuscript two methods to approximate the sensitivities for problems in topography optimization are introduced. The gradient is supplanted with either a stochastic approximation, or a physical approximation. Initially, an overview of the state-of-the-art in topography optimization is presented, and some key issues are explored. Subsequently, the technique is outlined, and the proposed methods are introduced. Furthermore, a numerical example in which a structure composed of shell elements is subject to a blast load is provided. This example is solved employing stochastic gradient approximation, and approximate gradient. They are compared to the widely used finite differences approximation. It is possible to observe that the proposed method significantly reduces the computational effort required to solve the problem, while considerably improving the objective function.

BUCKLING AND POST-BUCKLING OF ISOTROPIC AND COMPOSITE STIFFENED PANELS: A REVIEW ON ANALYSIS AND EXPERIMENT (2000-2012)

2021 ◽  
Vol 157 (A1) ◽  
Author(s):  
X-Y Ni ◽  
B G Prusty ◽  
A K Hellier
Keyword(s):  
State Of The Art ◽  
Shell Structures ◽  
Structural Elements ◽  
Engineering Structures ◽  
Broad Perspective ◽  
Stiffened Panels ◽  
Plate And Shell ◽  
Stiffened Structures ◽  
Post Buckling ◽  
Key Issues

Stiffened panels made out of isotropic or anisotropic materials are being extensively used as structural elements for aircraft, maritime, and other structures. In order to maintain stiffness and strength with light weight, new design techniques must be employed when utilising these materials. Their stability, ultimate strength and loading capacity are the key issues pertaining to these engineering structures which have attracted a number of investigators to undertake in- depth research, either in an academic or actual engineering context. This paper provides an extensive review of the research which has been conducted in recent years (2000-2012) on the buckling and post-buckling response of isotropic and composite stiffened plate and shell structures related to analysis and experiment. The key objective of this review article is to collate the research performed in the area of buckling and post-buckling behaviour of stiffened structures, thereby giving a broad perspective of the state-of-the-art in this field.

Buckling and Post-Buckling of Isotropic and Composite Stiffened Panels: A Review on Analysis and Experiment (2000-2012)

2015 ◽  
Vol 157 (A1) ◽  
pp. 9-30
Keyword(s):  
State Of The Art ◽  
Shell Structures ◽  
Structural Elements ◽  
Engineering Structures ◽  
Broad Perspective ◽  
Stiffened Panels ◽  
Plate And Shell ◽  
Stiffened Structures ◽  
Post Buckling ◽  
Key Issues

"Stiffened panels made out of isotropic or anisotropic materials are being extensively used as structural elements for aircraft, maritime, and other structures. In order to maintain stiffness and strength with light weight, new design techniques must be employed when utilising these materials. Their stability, ultimate strength and loading capacity are the key issues pertaining to these engineering structures which have attracted a number of investigators to undertake indepth research, either in an academic or actual engineering context. This paper provides an extensive review of the research which has been conducted in recent years (2000-2012) on the buckling and post-buckling response of isotropic and composite stiffened plate and shell structures related to analysis and experiment. The key objective of this review article is to collate the research performed in the area of buckling and post-buckling behaviour of stiffened structures, thereby giving a broad perspective of the state-of-the-art in this field."

Some new results and current challenges in the finite element analysis of shells

Acta Numerica ◽  
2001 ◽  
Vol 10 ◽  
pp. 215-250 ◽  
Author(s):  
Dominique Chapelle
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Shell Structures ◽  
Engineering Practice ◽  
Element Analysis ◽  
Shell Elements ◽  
Shell Models ◽  
The Finite Element Analysis ◽  
Shell Finite Element ◽  
Mathematical Analyses

This article, a companion to the article by Philippe G. Ciarlet on the mathematical modelling of shells also in this issue of Acta Numerica, focuses on numerical issues raised by the analysis of shells.Finite element procedures are widely used in engineering practice to analyse the behaviour of shell structures. However, the concept of ‘shell finite element’ is still somewhat fuzzy, as it may correspond to very different ideas and techniques in various actual implementations. In particular, a significant distinction can be made between shell elements that are obtained via the discretization of shell models, and shell elements – such as the general shell elements – derived from 3D formulations using some kinematic assumptions, without the use of any shell theory. Our first objective in this paper is to give a unified perspective of these two families of shell elements. This is expected to be very useful as it paves the way for further thorough mathematical analyses of shell elements. A particularly important motivation for this is the understanding and treatment of the deficiencies associated with the analysis of thin shells (among which is the locking phenomenon). We then survey these deficiencies, in the framework of the asymptotic behaviour of shell models. We conclude the article by giving some detailed guidelines to numerically assess the performance of shell finite elements when faced with these pathological phenomena, which is essential for the design of improved procedures.

scholarly journals Machine learning-based feature importance approach for sensitivity analysis of steel frames

2021 ◽  
Author(s):  
Hyeyoung Koh ◽  
Hannah Beth Blum
Keyword(s):  
Machine Learning ◽  
Sensitivity Analysis ◽  
Feature Selection ◽  
Large Scale ◽  
Failure Modes ◽  
Model Development ◽  
Predictive Performance ◽  
Computational Effort ◽  
Structural Systems ◽  
Feature Importance

This study presents a machine learning-based approach for sensitivity analysis to examine how parameters affect a given structural response while accounting for uncertainty. Reliability-based sensitivity analysis involves repeated evaluations of the performance function incorporating uncertainties to estimate the influence of a model parameter, which can lead to prohibitive computational costs. This challenge is exacerbated for large-scale engineering problems which often carry a large quantity of uncertain parameters. The proposed approach is based on feature selection algorithms that rank feature importance and remove redundant predictors during model development which improve model generality and training performance by focusing only on the significant features. The approach allows performing sensitivity analysis of structural systems by providing feature rankings with reduced computational effort. The proposed approach is demonstrated with two designs of a two-bay, two-story planar steel frame with different failure modes: inelastic instability of a single member and progressive yielding. The feature variables in the data are uncertainties including material yield strength, Young’s modulus, frame sway imperfection, and residual stress. The Monte Carlo sampling method is utilized to generate random realizations of the frames from published distributions of the feature parameters, and the response variable is the frame ultimate strength obtained from finite element analyses. Decision trees are trained to identify important features. Feature rankings are derived by four feature selection techniques including impurity-based, permutation, SHAP, and Spearman's correlation. Predictive performance of the model including the important features are discussed using the evaluation metric for imbalanced datasets, Matthews correlation coefficient. Finally, the results are compared with those from reliability-based sensitivity analysis on the same example frames to show the validity of the feature selection approach. As the proposed machine learning-based approach produces the same results as the reliability-based sensitivity analysis with improved computational efficiency and accuracy, it could be extended to other structural systems.

scholarly journals Relation-Aware Transformer for Portfolio Policy Learning

2020 ◽  
Author(s):  
Ke Xu ◽  
Yifan Zhang ◽  
Deheng Ye ◽  
Peilin Zhao ◽  
Mingkui Tan
Keyword(s):  
Portfolio Selection ◽  
State Of The Art ◽  
Asset Price ◽  
Sequential Patterns ◽  
Portfolio Decisions ◽  
Price Series ◽  
Crypto Currency ◽  
Key Issues ◽  
Multiple Assets ◽  
Portfolio Policy

Portfolio selection is an important yet challenging task in AI for FinTech. One of the key issues is how to represent the non-stationary price series of assets in a portfolio, which is important for portfolio decisions. The existing methods, however, fall short of capturing: 1) the complicated sequential patterns for asset price series and 2) the price correlations among multiple assets. In this paper, under a deep reinforcement learning paradigm for portfolio selection, we propose a novel Relation-aware Transformer (RAT) to handle these aspects. Specifically, being equipped with our newly developed attention modules, RAT is structurally innovated to capture both sequential patterns and asset correlations for portfolio selection. Based on the extracted sequential features, RAT is able to make profitable portfolio decisions regarding each asset via a newly devised leverage operation. Extensive experiments on real-world crypto-currency and stock datasets verify the state-of-the-art performance of RAT.

Entrepreneurship and fintech development: comparing reward and equity crowdfunding

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ciro Troise ◽  
Diego Matricano ◽  
Elena Candelo ◽  
Mario Sorrentino
Keyword(s):  
Design Methodology ◽  
State Of The Art ◽  
Methodological Approach ◽  
Point Of View ◽  
Comparative Approach ◽  
Current Debate ◽  
Content Type ◽  
Equity Crowdfunding ◽  
Research Propositions ◽  
Practical Implications

Purpose Starting from the state-of-the-art of Fintech development, this study aims to propose some research propositions comparing reward-crowdfunding (RCF) and equity-crowdfunding (ECF). In this sense, the present research provides a comprehensive analysis of fintech development and – to conceptualize the comparison between RCF and ECF – it focuses on campaigns’ characteristics, aims and post-campaigns scenarios. Design/methodology/approach All the research propositions related to the comparison between RCF and ECF are rooted in dedicated literature. The methodological approach adopted in the present paper can be referred to theorizing. Findings This study suggests that five key elements characterize the development of fintech: regulation, infrastructure, technologies, finance and innovations. The research provides nine propositions: four related to the campaigns’ characteristics; two related to the use of crowdfunding models by entrepreneurs; and three related to the performance of crowdfunded companies. Practical implications By offering nine research propositions, this study is expected to foster and support the investigation of fintech development from an entrepreneurial and managerial point of view. Originality/value To the best of authors’ knowledge, this study is among the first to explore the fintech development and to propose a comparative approach between RCF and ECF. This research contributes to the current debate on fintech development as well as on the comparison between crowdfunding models.

Machinima

2016 ◽  
pp. 149-181
Author(s):  
Tracy Harwood
Keyword(s):  
State Of The Art ◽  
Final Analysis ◽  
Growth Trajectories ◽  
Music Video ◽  
Review Of Literature ◽  
Channels Of Distribution ◽  
Video Advertising ◽  
Screen Capture ◽  
Key Issues ◽  
Cultural Movement

This chapter presents an overview of machinima, an important socio-cultural movement that originated in the 1990s gameplay movement known as demoscene. The chapter presents a review of literature and key issues related to its evolution. Modes of its production (perfect capture, screen capture, asset compositing, bespoke machinimation) are described, along with the range of different genres that have emerged, including fan vid, parody, documentary, music video, advertising, reportage, reenactment, activist, pre-visualization and artistic forms. Thereafter, the chapter identifies channels of distribution and growth trajectories for each. The chapter then presents four key phases of the emergence of machinima, identifying the key actors and roles of organizations within each phase. As a movement that continues to evolve, the discussion presented is by no means a final analysis, thus the aim of the chapter is to present a ‘state of the art' overview of its emergence and development.

Storytelling-Based Edutainment Applications

2011 ◽  
pp. 190-214 ◽  
Author(s):  
Anja Hoffman ◽  
Stefan Gobel ◽  
Oliver Schneider ◽  
Ido Iurgel
Keyword(s):  
Digital Storytelling ◽  
State Of The Art ◽  
Key Issues ◽  
Art Analysis ◽  
Learning Issues ◽  
Technical Platform ◽  
Narrative Learning

Within this chapter, the authors — all members of the Digital Storytelling group at ZGDV Darmstadt e.V. — provide an overview of the potential of storytelling-based edutainment applications and approaches for narrative learning applications. This covers not only online applications, but also off-line edutainment components, as well as hybrid scenarios combining both types. The chapter is structured into five parts. At the beginning, a global scenario of edutainment applications for museums is introduced and key issues concerning the establishment of edutainment applications and the level of interactivity for online applications are highlighted. These open and relevant issues are discussed within a technology-oriented, state-of-the art analysis concentrating on the authoring process, storytelling aspects, dramaturgy and learning issues. Based on this brief STAR analysis, storytelling methods and concepts, as well as a technical platform for the establishment of storytelling-based edutainment applications, are described. The strengths and weaknesses of these approaches are discussed within the context of the edutainment projects, art-E-fact and DinoHunter Senckenberg. Finally, the major results are summarized in a short conclusion and further research and application-driven trends (context: museums) are pointed out.

scholarly journals Parametric Sensitivity Analysis for Importance Measure on Failure Probability and Its Efficient Kriging Solution

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Yishang Zhang ◽  
Yongshou Liu ◽  
Xufeng Yang
Keyword(s):  
Sensitivity Analysis ◽  
Failure Probability ◽  
Computational Effort ◽  
Importance Measure ◽  
Sensitivity Index ◽  
Reliability Engineering ◽  
Parametric Sensitivity ◽  
Distribution Parameters ◽  
The Moment ◽  
Sensitivity Indicator

The moment-independent importance measure (IM) on the failure probability is important in system reliability engineering, and it is always influenced by the distribution parameters of inputs. For the purpose of identifying the influential distribution parameters, the parametric sensitivity of IM on the failure probability based on local and global sensitivity analysis technology is proposed. Then the definitions of the parametric sensitivities of IM on the failure probability are given, and their computational formulae are derived. The parametric sensitivity finds out how the IM can be changed by varying the distribution parameters, which provides an important reference to improve or modify the reliability properties. When the sensitivity indicator is larger, the basic distribution parameter becomes more important to the IM. Meanwhile, for the issue that the computational effort of the IM and its parametric sensitivity is usually too expensive, an active learning Kriging (ALK) solution is established in this study. Two numerical examples and two engineering examples are examined to demonstrate the significance of the proposed parametric sensitivity index, as well as the efficiency and precision of the calculation method.

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