Buckling behaviour of trees under self-weight loading

2019 ◽  
Vol 92 (4) ◽  
pp. 393-405 ◽  
Author(s):  
Mojtaba Dargahi ◽  
Timothy Newson ◽  
John Moore
Keyword(s):  
Management Strategies ◽  
Density Ratio ◽  
Benchmark Problems ◽  
Tree Stability ◽  
Closed Form Solutions ◽  
Circular Column ◽  
Instability Modes ◽  
Longitudinal Stiffness ◽  
Using Data ◽  
Case Validation

Abstract Understanding tree stability under self-weight and applied loads from wind and snow is important when developing management strategies to reduce the risk of damage from these abiotic agents. In this paper, linear buckling analysis was conducted using the finite element method to identify the instability modes of a tree structure under a specified set of loads. A non-prismatic elastic circular column of height H was analysed, taking self-weight into account. Various scenarios were considered: column taper, base rigidity, radial and longitudinal stiffness, ellipticity and crown weight. The effect on the critical buckling height was assessed in each case. Validation against closed form solutions of benchmark problems was conducted satisfactorily. The results indicate that column taper, base rigidity and the stiffness/density ratio are particularly important for this problem. Further comparison was made using data from a 15-year old Pinus radiata stand in New Zealand, which contained both buckled and non-buckled trees. While the model predicted factors of safety against buckling that were close to unity, it was unable to differentiate between buckled and non-buckled trees. Further investigation is needed to examine the reasons why this occurred. Despite this, the current study provides an in-depth numerical investigation, which has aided our understanding of the effects that material properties, geometric properties and boundary conditions have on buckling phenomenon in trees.

scholarly journals A Numerical Approach to Estimate Natural Frequency of Trees with Variable Properties

Forests ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 915
Author(s):  
Mojtaba Dargahi ◽  
Timothy Newson ◽  
John R. Moore
Keyword(s):  
Natural Frequency ◽  
Free Vibration Analysis ◽  
Numerical Approach ◽  
Benchmark Problems ◽  
The Finite Element Method ◽  
Closed Form Solutions ◽  
Circular Column ◽  
Longitudinal Stiffness ◽  
Problem Comparison ◽  
Case Validation

Free vibration analysis of a Euler-Bernoulli tapered column was conducted using the finite element method to identify the vibration modes of an equivalent tree structure under a specified set of conditions. A non-prismatic elastic circular column of height L was analysed, taking distributed self-weight into account. Various scenarios were considered: column taper, base fixity, radial and longitudinal stiffness (E) and density (ρ) and crown mass. The effect on the first natural frequency was assessed in each case. Validation against closed form solutions of benchmark problems was conducted satisfactorily. The results show that column taper, base fixity and E/ρ ratio are particularly important for this problem. Comparison of predictions with field observations of natural sway frequency for almost 700 coniferous and broadleaved trees from the published literature showed that the model worked well for coniferous trees, but less well for broadleaved trees with their more complicated crown architecture. Overall, the current study provides an in-depth numerical investigation of material properties, geometric properties and boundary conditions to create further understanding of vibration behaviour in trees.

Cyber Place Management and Crime Prevention: The Effectiveness of Cybersecurity Awareness Training Against Phishing Attacks

2021 ◽  
pp. 104398622110016
Author(s):  
Sinchul Back ◽  
Rob T. Guerette
Keyword(s):  
Crime Prevention ◽  
Research University ◽  
Management Strategies ◽  
Large Body ◽  
The United States ◽  
Place Management ◽  
Online Setting ◽  
Using Data ◽  
Virtual Domain ◽  
The Impact

Criminologists and crime prevention practitioners recognize the importance of geographical places to crime activities and the role that place managers might play in effectively preventing crime. Indeed, over the past several decades, a large body of work has highlighted the tendency for crime to concentrate across an assortment of geographic areas, where place management tends to be absent or weak. Nevertheless, there has been a paucity of research evaluating place management strategies and cybercrime within the virtual domain. The purpose of this study was to investigate the effectiveness of place management techniques on reducing cybercrime incidents in an online setting. Using data derived from the information technology division of a large urban research university in the United States, this study evaluated the impact of an anti-phishing training program delivered to employees that sought to increase awareness and understanding of methods to better protect their “virtual places” from cybercrimes. Findings are discussed within the context of the broader crime and place literature.

scholarly journals Pan-European sustainable forest management indicators for assessing Climate-Smart Forestry in Europe

2020 ◽  
pp. 1-10
Author(s):  
G. Santopuoli ◽  
C. Temperli ◽  
I. Alberdi ◽  
I. Barbeito ◽  
M. Bosela ◽  
...  
Keyword(s):  
Forest Management ◽  
Sustainable Forest Management ◽  
Management Strategies ◽  
Forest Policy ◽  
The State ◽  
Forest Damage ◽  
Tree Species Composition ◽  
Mitigation And Adaptation ◽  
Management Indicators ◽  
Using Data

The increasing demand for innovative forest management strategies to adapt to and mitigate climate change and benefit forest production, the so-called Climate-Smart Forestry, calls for a tool to monitor and evaluate their implementation and their effects on forest development over time. The pan-European set of criteria and indicators for sustainable forest management is considered one of the most important tools for assessing many aspects of forest management and sustainability. This study offers an analytical approach to selecting a subset of indicators to support the implementation of Climate-Smart Forestry. Based on a literature review and the analytical hierarchical approach, 10 indicators were selected to assess, in particular, mitigation and adaptation. These indicators were used to assess the state of the Climate-Smart Forestry trend in Europe from 1990 to 2015 using data from the reports on the State of Europe’s Forests. Forest damage, tree species composition, and carbon stock were the most important indicators. Though the trend was overall positive with regard to adaptation and mitigation, its evaluation was partly hindered by the lack of data. We advocate for increased efforts to harmonize international reporting and for further integrating the goals of Climate-Smart Forestry into national- and European-level forest policy making.

scholarly journals Income management strategies of older couples in Canada

2012 ◽  
Vol 38 (3-4) ◽  
pp. 1 ◽  
Author(s):  
Christine Laporte ◽  
Grant Schellenberg
Keyword(s):  
Educational Attainment ◽  
Common Law ◽  
Management Strategies ◽  
General Social Survey ◽  
Older Couples ◽  
Social Survey ◽  
Female Partners ◽  
Using Data

In this study, the income management strategies of Canadian couples are examined using data from the 2007 General Social Survey. The extent to which “older” couples, in which at least one spouse or partner is aged 45 or older, employ an allocative, pooled, or separate strategy is explored.Results show that the income management strategies used by these couples are correlated with relationship characteristics, such as common-law status, duration of relationship, and presence of children. As well, the likelihood of using a separate approach is positively correlated with levels of educational attainment and with the amount of income received by wives or female partners.

Differences in the Management of Perforated Appendicitis in Children by Race and Insurance Status

2017 ◽  
Vol 83 (9) ◽  
pp. 996-1000 ◽  
Author(s):  
Randi L. Lassiter ◽  
Robyn M. Hatley
Keyword(s):  
Household Income ◽  
Percutaneous Drainage ◽  
Management Strategies ◽  
Disease Process ◽  
Perforated Appendicitis ◽  
Black Children ◽  
Primary Diagnosis ◽  
Insurance Status ◽  
Similar Disease ◽  
Using Data

This study was conducted to assess whether race and socioeconomic status influence the management method used to treat pediatric perforated appendicitis. Nonelective pediatric admissions with a primary diagnosis of appendicitis were analyzed using data from the 2001–2010 Nationwide Inpatient Sample. Bivariate and multivariate analyses were used to determine the association between race, insurance status, median household income, rural/metropolitan location, and the risk adjusted odds of undergoing surgery, laparoscopic appendectomy, percutaneous drainage, or neither surgery nor percutaneous drainage. A total of 46,211 admissions of perforated appendicitis were identified. Surgery was performed in 90.5 per cent of them. Black children were less likely to have surgery [adjusted odds ratio (AOR) = 0.53] and more likely to be managed non-surgically with percutaneous drainage (AOR = 1.79). Self-pay patients were less likely to have laparoscopic surgery (AOR = 0.80). Children from rural counties were more likely to undergo surgery than those from larger metropolitan areas (AOR = 1.30). Higher estimated household income did not predict the method of treatment. Although previous studies have attributed racial disparities in outcomes for appendicitis to different rates of perforation and access to care, these findings demonstrate significantly dissimilar management strategies for patients presenting with a similar disease process.

Gender Differences in Youth Exposure to Community Violence: A Partial Test of Power-Control Theory

2019 ◽  
Vol 15 (2) ◽  
pp. 123-146
Author(s):  
Maria João Lobo Antunes ◽  
Eileen M. Ahlin ◽  
Amanda D. Emmert ◽  
Michelle Manasse
Keyword(s):  
Gender Differences ◽  
Control Theory ◽  
Power Control ◽  
Community Violence ◽  
Parenting Practices ◽  
Management Strategies ◽  
Behavioral Outcomes ◽  
Family Management ◽  
Exposure To Community Violence ◽  
Using Data

Youths’ exposure to community violence increases their risk for harmful emotional and behavioral outcomes. Several family management strategies protect youth against exposure though there is scant literature exploring whether their application is gendered. Using data from the Project on Human Development in Chicago Neighborhoods, we draw from power-control theory to assess gender differences in family management strategies and the extent to which this accounts for boys’ greater exposure to neighborhood violence. Controlling for neighborhood contextual factors and youth covariates of exposure to violence, findings suggest that parents adopt gendered parenting practices, which in turn helps clarify why boys are more likely to report exposure to community violence.

scholarly journals Causes and Outcomes of Admission and Investigation of Tuberculosis in Adults with Advanced HIV in South African Hospitals: Data from the TB Fast Track Trial

2021 ◽  
Author(s):  
Peter Beckwith ◽  
Mpho Tlali ◽  
Salome Charalambous ◽  
Gavin J. Churchyard ◽  
Katherine L. Fielding ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Fast Track ◽  
Management Strategies ◽  
Case Fatality ◽  
Risk Of Death ◽  
Tb Treatment ◽  
Common Causes ◽  
Hiv Positive Adults ◽  
Using Data ◽  
Poor Outcomes

Tuberculosis (TB) remains the leading cause of hospitalization and in-hospital mortality in HIV-positive adults. Using data from hospital and clinic files, research databases, and autopsy, we describe causes and outcomes of admissions, and assess investigations for TB among adults with advanced HIV who were hospitalized after enrollment into the TB Fast Track trial in South Africa (2013–2015). A total of 251 adults [median CD4 count, 37.5 cells/μL; interquartile range, 14–68 cells/µL; 152 (60.6%) on antiretroviral therapy] experienced 304 admissions. Ninety-five of 251 of the first admissions (37.8%) were TB related; the next most common causes were AIDS-related illnesses (41 of 251, 16.3%) and surgical causes (21 of 251, 8.4%). Of those admitted with previously undiagnosed TB, 60% had CD4 counts less than 50 cells/µL. Overall, 137 of 251 individuals (54.6%) died in the hospital or within 90 days of their first discharge. Case fatality rates were particularly high for those admitted with TB (66%) and bacterial infections (80%). In 144 admissions for whom anti-TB treatment had not been started before admission, a sputum-based TB investigation was recorded in only 12 of 57 admissions (21.1%) in whom one or more TB symptom was recorded (24 of 57 started on treatment), and 6 of 87 admissions (6.9%) in whom no TB symptoms were recorded (14 of 87 started on treatment). Hospitalized adults with advanced HIV are at high risk of death. TB was a common cause of hospitalization but was under-investigated, even in those with symptoms. In addition to early identification of TB and other AIDS-related illnesses during hospitalization of adults with advanced HIV, improved pre-hospital management strategies are needed to interrupt disease progression and reduce poor outcomes in this already vulnerable population.

scholarly journals Project-based maturity assessment model for smart transformation in Taiwanese enterprises

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254522
Author(s):  
Tzu-Chieh Lin ◽  
Kung Jeng Wang
Keyword(s):  
Project Management ◽  
Management Strategies ◽  
Assessment Model ◽  
Smart Manufacturing ◽  
Maturity Model ◽  
Maturity Level ◽  
Implementation Barriers ◽  
External Resources ◽  
Maturity Assessment ◽  
Using Data

As smart technology proliferates, enterprises must engage not only in the transformation of intelligence but contend with pressure do so as soon as possible. Smart transformation is critical for manufacturing enterprises in the development of smart manufacturing. This study addressed the gap between maturity models and project management by designing an effective assessment framework for smart transformation. It adopts the Smart Industry Readiness Index, created by the Singapore Economic Development Board, as a maturity assessment model to analyze enterprises’ smart transformation and formulate project management strategies. Enterprises can use this model to examine the maturity level of their transformation and assess scope for improvement in their project strategies and implementation barriers. This study focuses on Taiwanese enterprises using data collected from 165 valid questionnaires and subjected to a cluster analysis. Enterprises were divided into three categories. The results reveal that, first, most enterprises’ smart transformation is at an immature or medium-maturity level, and is therefore amenable to further improvement. Second, inconsistent with research findings, many enterprises invest in transformation projects but fail to advance these projects to maturity. Third, most enterprises’ project management plans fail to meet actual transformation needs. Using the thematically oriented maturity model proposed in this study, Taiwanese enterprises can effectively evaluate the maturity of their transformation projects. In conclusion, the study highlights that Taiwanese enterprises must identify more effective external resources to strengthen their competitiveness.

A Survey With Numerical Assessment of Classical and Refined Theories for the Analysis of Sandwich Plates

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
E. Carrera ◽  
S. Brischetto
Keyword(s):  
Higher Order ◽  
Benchmark Problems ◽  
Geometrical Parameters ◽  
Closed Form Solutions ◽  
Simply Supported ◽  
Numerical Assessment ◽  
Shell Analysis ◽  
Out Of Plane ◽  
The Face ◽  
Free Vibration Response

A large variety of plate theories are described and assessed in the present work to evaluate the bending and vibration of sandwich structures. A brief survey of available works is first given. Such a survey includes significant review papers and latest developments on sandwich structure modelings. The kinematics of classical, higher order, zigzag, layerwise, and mixed theories is described. An exhaustive numerical assessment of the whole theories is provided in the case of closed form solutions of simply supported panels made of orthotropic layers. Reference is made to the unified formulation that has recently been introduced by the first author for a plate/shell analysis. Attention has been given to displacements, stresses (both in-plane and out-of-plane components), and the free vibration response. Only simply supported orthotropic panels loaded by a transverse distribution of bisinusoidal pressure have been analyzed. Five benchmark problems are treated. The accuracy of the plate theories is established with respect to the length-to-thickness-ratio (LTR) geometrical parameters and to the face-to-core-stiffness-ratio (FCSR) mechanical parameters. Two main sources of error are outlined, which are related to LTR and FCSR, respectively. It has been concluded that higher order theories (HOTs) can be conveniently used to reduce the error due to LTR in thick plate cases. But HOTs are not effective in increasing the accuracy of the classical theory analysis whenever the error is caused by increasing FCSR values; layerwise analysis becomes mandatory in this case.

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