Robust-mode analysis of hydrodynamic flows

2017 ◽  
Vol 31 (10) ◽  
pp. 1742007
Author(s):  
Sukesh Roy ◽  
James R. Gord ◽  
Jia-Chen Hua ◽  
Gemunu H. Gunaratne
Keyword(s):  
Financial Markets ◽  
Mode Analysis ◽  
Complex Flows ◽  
High Resolution Data ◽  
Principle Components Analysis ◽  
Cellular Flame ◽  
Low Pass ◽  
Components Analysis ◽  
Injector Flows ◽  
Traditional Approaches

The emergence of techniques to extract high-frequency high-resolution data introduces a new avenue for modal decomposition to assess the underlying dynamics, especially of complex flows. However, this task requires the differentiation of robust, repeatable flow constituents from noise and other irregular features of a flow. Traditional approaches involving low-pass filtering and principle components analysis have shortcomings. The approach outlined here, referred to as robust-mode analysis, is based on Koopman decomposition. Three applications to (a) a counter-rotating cellular flame state, (b) variations in financial markets, and (c) turbulent injector flows are provided.

scholarly journals Principle components of thermal regimes in mountain river networks

2018 ◽  
Author(s):  
Daniel J. Isaak ◽  
Charles H. Luce ◽  
Gwynne L. Chandler ◽  
Dona L. Horan ◽  
Sherry P. Wollrab
Keyword(s):  
Winter Season ◽  
Mode Analysis ◽  
River Networks ◽  
Physical Processes ◽  
Principle Components Analysis ◽  
Mountain Environments ◽  
Abstract Description ◽  
Thermal Regimes ◽  
Components Analysis ◽  
Flowing Waters

Abstract. Description of thermal regimes in flowing waters is key to understanding physical processes, enhancing predictive abilities, and improving bioassessments. Spatially and temporally sparse datasets, especially in logistically challenging mountain environments, have limited studies on thermal regimes but inexpensive sensors coupled with crowd-sourced data collection efforts provide efficient means of developing large datasets for robust analyses. Here, thermal regimes are assessed using annual monitoring records spanning a five-year period (2011–2015) at 226 sites across several contiguous montane river networks in the northwestern U.S. Regimes were summarized with 28 metrics and principle components analysis (PCA) was used to determine those metrics which best explained thermal variation on a reduced set of orthogonal axes. Four principle components (PC) accounted for 93.4 % of the variation in the temperature metrics, with the first PC (49 % of variance) associated with metrics that represented magnitude and variability and the second PC (29 % of variance) associated with metrics representing the length and intensity of the winter season. Another variant of PCA, T-mode analysis, was applied to daily temperature values and revealed two distinct phases of spatial variance – a homogeneous phase during winter when daily temperatures at all sites were

scholarly journals Insomnia among Egyptian Samples of University Students and Employees

2014 ◽  
Vol 8 (2) ◽  
pp. 377
Author(s):  
Ahmed Abdel-Khalek ◽  
Maysa al Nyal ◽  
Hanan Saeed
Keyword(s):  
University Students ◽  
Prevalence Rate ◽  
Age Groups ◽  
Female Students ◽  
Principle Components Analysis ◽  
Female Employees ◽  
Males And Females ◽  
Components Analysis ◽  
Male University Students ◽  
Two Age Groups

The aim of this study was to estimate the prevalence of insomnia, differences between males and females, and between two age groups, and to explore the factorial structure of the Arabic Scale of Insomnia (ASI). Samples of university students (n=500) and employees (n=457) of both sexes were recruited. Female university students obtained the highest mean total score on the ASI, followed by female employees, male university students, and finally male employees. The salient significant differences were between female students and male employees and between male and female employees. Despite the differences in the prevalence rate of insomnia between the four groups, they all agreed on that the least prevalence rate was for the item: “I feel depressed when it is time for me to go to bed, whereas the highest prevalence rate was for the item: “My interrupted sleep annoys me.” Principle components analysis yielded three factors for each group. Most of their names were not identical. The most salient finding of this study was the statistically significant sex differences in insomnia in favor of women. It was concluded that is it important to introduce counseling for those who obtained high scores on the ASI. 

scholarly journals Indigenous Land and Sea Management Programs (ILSMPs) Enhance the Wellbeing of Indigenous Australians

2019 ◽  
Vol 17 (1) ◽  
pp. 125 ◽  
Author(s):  
Silva Larson ◽  
Natalie Stoeckl ◽  
Diane Jarvis ◽  
Jane Addison ◽  
Daniel Grainger ◽  
...  
Keyword(s):  
Environmental Management ◽  
Indigenous People ◽  
Indigenous Communities ◽  
Indigenous Australians ◽  
Future Design ◽  
Principle Components Analysis ◽  
Wide Range ◽  
Components Analysis ◽  
Language Schools ◽  
Indigenous Land

Conservation and environmental management have been reported as offering opportunities to substantially improve the wellbeing of Indigenous people. Using the holistic wellbeing impact evaluation (W-IE) approach—well suited for use in Indigenous communities—we interviewed 190 Indigenous Australians across four communities. All communities were involved in the Indigenous land and sea management programs (ILSMPs). Our study explored the conceptualisation of ‘wellbeing’ by participants. In particular, we were interested in the aspects of wellbeing perceived to be affected by ILSMPs. Out of the 26 wellbeing factors explored, ‘Health centres’; ‘Language’; ‘Schools’; and ‘Safe community’ emerged as being of highest importance to the largest percentage of the respondents. When grouped using principle components analysis (PCA), the ‘Community and society’ domain emerged as the most important; accounting for 52% of the overall importance of all wellbeing factors. The second most important domain was the ‘Country and culture’, contributing 31%. Lastly, ‘Economic aspects’ contributed only 17%. Respondents believed that ILSMPs have played a considerable causal role in improving wellbeing, by positively changing factors most important to them. Specifically, 73% of perceived causal links were related to improvements in the ‘Country and Culture’ and 23% to ‘Community and Society’ domain. We thus conclude that land management for Indigenous people is much more than ecological or environmental management with ILSMPs, perceived to cause a wide range of cultural and social benefits. We also propose ways in which the future design of such programs could be improved to further increase benefits.

Examining social, physical, and environmental dimensions of tornado vulnerability in Texa

2016 ◽  
Vol 14 (2) ◽  
pp. 139
Author(s):  
Laura Siebeneck, PhD
Keyword(s):  
Vulnerability Index ◽  
Census Bureau ◽  
Source Information ◽  
Principle Components Analysis ◽  
Emergency Managers ◽  
The Social ◽  
Vulnerability Model ◽  
The Us ◽  
Components Analysis ◽  
Us Census

Objective: To develop a vulnerability model that captures the social, physical, and environmental dimensions of tornado vulnerability of Texas counties. Design: Guided by previous research and methodologies proposed in the hazards and emergency management literature, a principle components analysis is used to create a tornado vulnerability index. Data were gathered from open source information available through the US Census Bureau, American Community Surveys, and the Texas Natural Resources Information System.Setting: Texas counties.Results: The results of the model yielded three indices that highlight geographic variability of social vulnerability, built environment vulnerability, and tornado hazard throughout Texas. Further analyses suggest that counties with the highest tornado vulnerability include those with high population densities and high tornado risk.Conclusions: This article demonstrates one method for assessing statewide tornado vulnerability and presents how the results of this type of analysis can be applied by emergency managers towards the reduction of tornado vulnerability in their communities.

Lomer Dislocations in Al: Deformation Field Analysis

1994 ◽  
Vol 47 (6S) ◽  
pp. S321-S325
Author(s):  
Rob Phillips
Keyword(s):  
High Resolution ◽  
Microscopic Analysis ◽  
Field Analysis ◽  
Atomistic Simulations ◽  
Image Simulation ◽  
Strain Fields ◽  
High Resolution Data ◽  
Trial Structure ◽  
Traditional Approaches

We examine two issues that arise in connection with the description of dislocations in metals. First, the experiments of Mills and Stadelmann on Lomer dislocations in Al are considered in light of atomistic simulations of their core structures. It is shown that the results of such a microscopic analysis are consistent with those obtained earlier on the basis of image simulation. Secondly, we examine these Lomer dislocations using the recently developed technique of Computational Fourier Transform Moire` (CFTM) analysis. This technique allows for a determination of the strain fields near a defect directly from a high-resolution image without the necessity of obtaining a trial structure for the defect, complementing traditional approaches to the interpretation of high-resolution data.

Three-dimensional direct numerical simulation of a turbulent lifted hydrogen jet flame in heated coflow: a chemical explosive mode analysis

2010 ◽  
Vol 652 ◽  
pp. 45-64 ◽  
Author(s):  
T. F. LU ◽  
C. S. YOO ◽  
J. H. CHEN ◽  
C. K. LAW
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Near Field ◽  
Three Dimensional ◽  
Mode Analysis ◽  
Scalar Dissipation ◽  
Complex Flows ◽  
Jet Flame ◽  
Auto Ignition ◽  
Grid Points

A chemical explosive mode analysis (CEMA) was developed as a new diagnostic to identify flame and ignition structure in complex flows. CEMA was then used to analyse the near-field structure of the stabilization region of a turbulent lifted hydrogen–air slot jet flame in a heated air coflow computed with three-dimensional direct numerical simulation. The simulation was performed with a detailed hydrogen–air mechanism and mixture-averaged transport properties at a jet Reynolds number of 11000 with over 900 million grid points. Explosive chemical modes and their characteristic time scales, as well as the species involved, were identified from the Jacobian matrix of the chemical source terms for species and temperature. An explosion index was defined for explosive modes, indicating the contribution of species and temperature in the explosion process. Radical and thermal runaway can consequently be distinguished. CEMA of the lifted flame shows the existence of two premixed flame fronts, which are difficult to detect with conventional methods. The upstream fork preceding the two flame fronts thereby identifies the stabilization point. A Damköhler number was defined based on the time scale of the chemical explosive mode and the local instantaneous scalar dissipation rate to highlight the role of auto-ignition in affecting the stabilization points in the lifted jet flame.

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