scholarly journals Modal testing for model validation of structures with discrete nonlinearities

2015 ◽  
Vol 373 (2051) ◽  
pp. 20140410 ◽  
Author(s):  
D. J. Ewins ◽  
B. Weekes ◽  
A. delli Carri
Keyword(s):  
Model Validation ◽  
Nonlinear Response ◽  
Structural Integrity ◽  
Linear Models ◽  
Recent Literature ◽  
Modal Testing ◽  
Structural Dynamic ◽  
Nonlinear Features ◽  
Using Data ◽  
Further Development

Model validation using data from modal tests is now widely practiced in many industries for advanced structural dynamic design analysis, especially where structural integrity is a primary requirement. These industries tend to demand highly efficient designs for their critical structures which, as a result, are increasingly operating in regimes where traditional linearity assumptions are no longer adequate. In particular, many modern structures are found to contain localized areas, often around joints or boundaries, where the actual mechanical behaviour is far from linear. Such structures need to have appropriate representation of these nonlinear features incorporated into the otherwise largely linear models that are used for design and operation. This paper proposes an approach to this task which is an extension of existing linear techniques, especially in the testing phase, involving only just as much nonlinear analysis as is necessary to construct a model which is good enough, or ‘valid’: i.e. capable of predicting the nonlinear response behaviour of the structure under all in-service operating and test conditions with a prescribed accuracy. A short-list of methods described in the recent literature categorized using our framework is given, which identifies those areas in which further development is most urgently required.

Estimating Nonhierarchical and Nested Log-Linear Models

1981 ◽  
Vol 10 (1) ◽  
pp. 3-49 ◽  
Author(s):  
Jay Magidson ◽  
James H. Swan ◽  
Richard A. Berk
Keyword(s):  
Linear Models ◽  
Recent Literature ◽  
Computer Programs ◽  
Iterative Proportional Fitting ◽  
Nested Models ◽  
Indicator Variables ◽  
Interaction Variables ◽  
Dichotomous Variables ◽  
Using Data ◽  
Log Linear

The recent literature on-log-linear models incorrectly implies that the Iterative Proportional Fitting (IPF) algorithm and associated computer programs such as ECTA can only be used to estimate hierarchical (not nonhierarchical) log-linear models. While ECTA and similar programs are designed for the estimation of hierarchical models, it is shown here that the IPF algorithm (and existing computer programs such as ECTA) can be used to estimate any nonhierarchical model and also many nested log-linear models. The former result follows directly from the symmetry between qualitative/categorical indicator variables and appropriately defined “interaction variables.” The general approach for dichotomous variables is illustrated here using data from the study of “The American Soldier” by Stouffer et al. We also illustrate how the ECTA program can be used to estimate nested models, and show the equivalence between a particular class of nested models and the model of quasi-independence.

scholarly journals A top-level model of case-based argumentation for explanation: Formalisation and experiments

2021 ◽  
pp. 1-36
Author(s):  
Henry Prakken ◽  
Rosa Ratsma
Keyword(s):  
Machine Learning ◽  
Decision Making ◽  
Linear Models ◽  
Evaluation Studies ◽  
Data Sets ◽  
Machine Learning Applications ◽  
Level Model ◽  
Similarities And Differences ◽  
Further Development ◽  
Case Based

This paper proposes a formal top-level model of explaining the outputs of machine-learning-based decision-making applications and evaluates it experimentally with three data sets. The model draws on AI & law research on argumentation with cases, which models how lawyers draw analogies to past cases and discuss their relevant similarities and differences in terms of relevant factors and dimensions in the problem domain. A case-based approach is natural since the input data of machine-learning applications can be seen as cases. While the approach is motivated by legal decision making, it also applies to other kinds of decision making, such as commercial decisions about loan applications or employee hiring, as long as the outcome is binary and the input conforms to this paper’s factor- or dimension format. The model is top-level in that it can be extended with more refined accounts of similarities and differences between cases. It is shown to overcome several limitations of similar argumentation-based explanation models, which only have binary features and do not represent the tendency of features towards particular outcomes. The results of the experimental evaluation studies indicate that the model may be feasible in practice, but that further development and experimentation is needed to confirm its usefulness as an explanation model. Main challenges here are selecting from a large number of possible explanations, reducing the number of features in the explanations and adding more meaningful information to them. It also remains to be investigated how suitable our approach is for explaining non-linear models.

Educational Homogamy Among Married and Unmarried Couples in Europe

2008 ◽  
Vol 30 (1) ◽  
pp. 28-52 ◽  
Author(s):  
Dana Hamplova
Keyword(s):  
Linear Models ◽  
Married Couples ◽  
European Social Survey ◽  
Social Survey ◽  
Educational Homogamy ◽  
Educational Barriers ◽  
Educational Groups ◽  
Institutional Contexts ◽  
Using Data ◽  
Log Linear

In this article, educational homogamy among married and cohabiting couples in selected European countries is examined. Using data from two waves (2002 and 2004) of the European Social Survey, this article compares three cultural and institutional contexts that differ in terms of institutionalization of cohabitation. Evidence from log-linear models yields two main conclusions. First, as cohabitation becomes more common in society, marriage and cohabitation become more similar with respect to partner selection. Second, where married and unmarried unions differ in terms of educational homogamy, married couples have higher odds of overcoming educational barriers (i.e., intermarrying with other educational groups).

scholarly journals ANALYSIS OF CORROSION DEPTH PERCENTAGE ON THE INNER BOTTOM PLATES OF AGING BULK CARRIERS WITH AN AIM TO OPTIMIZE CORROSION MARGIN

Brodogradnja ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 81-95
Author(s):  
Špiro Ivošević ◽  
◽  
Nataša Kovač ◽  
Nikola Momčilović ◽  
Goran Vukelić ◽  
...  
Keyword(s):  
Fuel Consumption ◽  
Alternative Energy ◽  
Structural Integrity ◽  
Linear Models ◽  
Metal Plate ◽  
Fuel Oil ◽  
Corrosion Depth ◽  
Structural Rules ◽  
Bulk Carriers ◽  
Simple Conversion

To ensure the better structural integrity and maximum safety of bulk carriers in the ship design phase, an appropriate corrosion margin is introduced by the classification societies, which should enable the exploitation of ships during the projected 25-year life cycle. The new Common Structural Rules introduce even higher corrosion margin value to ensure the structural integrity of the ship. This directly affects the increase in hull weight and thus the need for more total installed power and higher fuel consumption. Higher fuel consumption results in increased emissions which directly affects environmental pollution. For these reasons, efforts are being made to introduce alternative energy sources, cleaner fuel, ship weight reduction, and the overall economic efficiency of ships. Therefore, using experimental data collected on aging bulk carriers, the paper explores the corrosion margin reduction potential considering its impact on hull weight. Assuming that the corrosive processes occur after four years of operation, a linear model that describes the percentage of plate wear as a function of the as build-in the thickness of inner bottom plates (IBP) of fuel oil tanks (FOT) located on the double bottom of aging bulk carriers, is analyzed. Over the course of 25 years, the IBP segment was monitored on 36 different ships surveys. In this way, 520 input data describing the depth of corrosion were formed. At the same time, records were kept on the mean thickness of the original metal plate, which enabled systematization of the empirical database and grouping of measured values by intervals of original plate thicknesses, and simple conversion of corrosion depth into adequate percentage values. Depth corrosion percentages were represented by standard linear models known in the literature. Based on this analysis, representative numerical and graphical results were obtained. Conclusions from the paper can assist to optimize corrosion margin and the energy efficiency of future vessels.

scholarly journals A Wireless Strain Sensor Network for Structural Health Monitoring

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Chengyin Liu ◽  
Jun Teng ◽  
Ning Wu
Keyword(s):  
Structural Health Monitoring ◽  
Sensor Network ◽  
Health Monitoring ◽  
Evaluation System ◽  
Strain Sensor ◽  
Modal Testing ◽  
Dynamic Strain ◽  
Structural Dynamic ◽  
Structural Health ◽  
Strain Monitoring

Structural strain under external environmental loads is one of the main monitoring parameters in structural health monitoring or dynamic tests. This paper presents a wireless strain sensor network (WSSN) design for monitoring structural dynamic strain field. A precision strain sensor board is developed and integrated with the IRIS mote hardware/software platform for multichannel strain gauge signal conditioning and wireless monitoring. Measurement results confirm the sensor’s functionality regarding its static and dynamic characterization. Furthermore, in order to verify the functionality of the designed wireless strain sensor for dynamic strain monitoring, a cluster-star network evaluation system is developed for strain modal testing on an experimental steel truss structure. Test results show very good agreement with the finite element (FE) simulations. This paper demonstrates the feasibility of the proposed WSSN for large structural dynamic strain monitoring.

Sustainability engagement’s impact on tourism sector performance: linear and nonlinear models

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Amina Buallay ◽  
Jasim Al-Ajmi ◽  
Elisabetta Barone
Keyword(s):  
Significant Relationship ◽  
Linear Models ◽  
Performance Indicator ◽  
Nonlinear Models ◽  
Sustainability Reporting ◽  
Analytical Framework ◽  
Content Type ◽  
Return On Equity ◽  
Using Data ◽  
The Relationship

PurposeThis study aims to investigate the relationship between the level of sustainability reporting and tourism sector’s performance (operational, financial and market).Design/methodology/approachUsing data culled from 1,375 observations from 37 different countries for ten years (2008–2017), an independent variable derived from the environmental, social and governance (ESG score) is regressed against dependent performance indicator variables (return on assets (ROA), return on equity (ROE) and Tobin's Q (TQ)). Two types of control variables complete the regression analysis in this study: firm-specific and macroeconomic.FindingsThe findings elicited from the empirical results of the linear models demonstrate that there is a significant relationship between ESG and operational performance (ROA) and market performance (TQ). However, there is no significant relationship between ESG and financial performance (ROE). Furthermore, the results of the nonlinear models suggest that the relationship between sustainability performance and firm's profitability and valuation is nonlinear (inverted U-shape).Originality/valueThe models in this study presents a valuable analytical framework for exploring sustainability reporting as a driver of performance in the tourism sector's economies. In addition, this study highlights the tourism sector's management lacunae manifesting in terms of the weak nexus between each component of ESG and tourism sector's performance.

A Terminological and Ontological Analysis of the NCI Thesaurus

2005 ◽  
Vol 44 (04) ◽  
pp. 498-507 ◽  
Author(s):  
B. Smith ◽  
L. Goldberg ◽  
W. Ceusters
Keyword(s):  
Recent Literature ◽  
Good Practice ◽  
Representation System ◽  
Ontology Design ◽  
Formal Definitions ◽  
On Line ◽  
Ontological Analysis ◽  
Knowledge Representation System ◽  
Further Development ◽  
Principles Of Good Practice

Summary Objective: The National Cancer Institute Thesaurus is described by its authors as “a biomedical vocabulary that provides consistent, unambiguous codes and definitions for concepts used in cancer research” and which “exhibits ontology-like properties in its construction and use”. We performed a qualitative analysis of the Thesaurus in order to assess its conformity with principles of good practice in terminology and ontology design. Materials and Methods: We used both the on-line browsable version of the Thesaurus and its OWL-representation (version 04.08b, released on August 2, 2004), measuring each in light of the requirements put forward in relevant ISO terminology standards and in light of ontological principles advanced in the recent literature. Results: We found many mistakes and inconsistencies with respect to the term-formation principles used, the underlying knowledge representation system, and missing or inappropriately assigned verbal and formal definitions. Conclusion: Version 04.08b of the NCI Thesaurus suffers from the same broad range of problems that have been observed in other biomedical terminologies. For its further development, we recommend the use of a more principled approach that allows the Thesaurus to be tested not just for internal consistency but also for its degree of correspondence to that part of reality which it is designed to represent.

scholarly journals Translational Roadmap for the Organs-on-a-Chip Industry toward Broad Adoption

2020 ◽  
Vol 7 (3) ◽  
pp. 112 ◽  
Author(s):  
Vanessa Allwardt ◽  
Alexander J. Ainscough ◽  
Priyalakshmi Viswanathan ◽  
Stacy D. Sherrod ◽  
John A. McLean ◽  
...  
Keyword(s):  
Technology Development ◽  
Technology Readiness ◽  
Disruptive Technology ◽  
Discovery Process ◽  
Drug Discovery Process ◽  
Commercial Viability ◽  
Performance Benchmarks ◽  
Using Data ◽  
Further Development

Organs-on-a-Chip (OOAC) is a disruptive technology with widely recognized potential to change the efficiency, effectiveness, and costs of the drug discovery process; to advance insights into human biology; to enable clinical research where human trials are not feasible. However, further development is needed for the successful adoption and acceptance of this technology. Areas for improvement include technological maturity, more robust validation of translational and predictive in vivo-like biology, and requirements of tighter quality standards for commercial viability. In this review, we reported on the consensus around existing challenges and necessary performance benchmarks that are required toward the broader adoption of OOACs in the next five years, and we defined a potential roadmap for future translational development of OOAC technology. We provided a clear snapshot of the current developmental stage of OOAC commercialization, including existing platforms, ancillary technologies, and tools required for the use of OOAC devices, and analyze their technology readiness levels. Using data gathered from OOAC developers and end-users, we identified prevalent challenges faced by the community, strategic trends and requirements driving OOAC technology development, and existing technological bottlenecks that could be outsourced or leveraged by active collaborations with academia.

scholarly journals Invariant Causal Prediction for Nonlinear Models

2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Christina Heinze-Deml ◽  
Jonas Peters ◽  
Nicolai Meinshausen
Keyword(s):  
Linear Models ◽  
Causal Model ◽  
Nonlinear Models ◽  
Causal Structure ◽  
Nonparametric Tests ◽  
Population Projections ◽  
World Population ◽  
Residual Distribution ◽  
Using Data

AbstractAn important problem in many domains is to predict how a system will respond to interventions. This task is inherently linked to estimating the system’s underlying causal structure. To this end, Invariant Causal Prediction (ICP) [1] has been proposed which learns a causal model exploiting the invariance of causal relations using data from different environments. When considering linear models, the implementation of ICP is relatively straightforward. However, the nonlinear case is more challenging due to the difficulty of performing nonparametric tests for conditional independence.In this work, we present and evaluate an array of methods for nonlinear and nonparametric versions of ICP for learning the causal parents of given target variables. We find that an approach which first fits a nonlinear model with data pooled over all environments and then tests for differences between the residual distributions across environments is quite robust across a large variety of simulation settings. We call this procedure “invariant residual distribution test”. In general, we observe that the performance of all approaches is critically dependent on the true (unknown) causal structure and it becomes challenging to achieve high power if the parental set includes more than two variables.As a real-world example, we consider fertility rate modeling which is central to world population projections. We explore predicting the effect of hypothetical interventions using the accepted models from nonlinear ICP. The results reaffirm the previously observed central causal role of child mortality rates.

Integrity Assessment of Pressure Components With Local Hot Spots

2005 ◽  
Vol 127 (2) ◽  
pp. 137-142 ◽  
Author(s):  
R. Seshadri
Keyword(s):  
Hot Spots ◽  
Structural Integrity ◽  
Refractory Lining ◽  
Assessment Method ◽  
Pressure Vessels ◽  
Industrial Processes ◽  
Integrity Assessment ◽  
Piping Systems ◽  
Further Development ◽  
Level 2

Local hot spots can occur in some pressure vessels and piping systems used in industrial processes. The hot spots could be a result of, for instance, localized loss of refractory lining on the inside of pressure components or due to a maldistribution of process flow within vessels containing catalysts. The consequences of these hot spots on the structural integrity of pressure components are of considerable importance to plant operators. The paper addresses structural integrity issues in the context of codes and standards design framework. Interaction of hot spots, as is the case when multiple hot spots occur, is addressed. An assessment method, suitable for further development of a Level 2 “Fitness-for-Service” methodology, is discussed and applied to a commonly used pressure component configuration.

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