Modeling the Elastic Properties of Reticulated Porous Ceramics

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Stephen J. Sedler ◽  
Thomas R. Chase ◽  
Jane H. Davidson
Keyword(s):  
Relative Density ◽  
Elastic Properties ◽  
Bulk Material ◽  
Porous Ceramics ◽  
Cross Sectional ◽  
Exterior Surface ◽  
Plateau Border ◽  
Unit Structure ◽  
Half Angle ◽  
The Impact

A model to predict the elastic material properties of reticulated porous ceramics (RPCs) based on the microstructural geometry is presented. The RPC is represented by a repeating unit structure of truncated octahedrons (tetrakaidecahedrons) with the ligaments represented by the cell edges. The deformations of the ligaments in the cellular structure under applied loads are used to determine the effective moduli and Poisson's ratio of the bulk material. The ligament cross section is represented as having a Plateau border exterior surface with a cusp half-angle that is varied between 0 and 90 deg, and a Plateau border interior void with a cusp half-angle of zero, representative of the ranges seen in RPCs. The ligament cross-sectional area is permitted to vary along its length and the distance between internal and external cusps is assumed constant. The relative density of the foam, corresponding to the length, cusp distances, and external-cusp half-angle of the ligaments, is determined using solid geometry. The relative density has the dominant effect on the moduli, while normalized ligament length varies the moduli by 11–49% at a specified relative density. The impact of the external shape of a ligament on the relative moduli is insignificant. The model is validated through comparisons with the measured elastic properties of RPCs in the literature and new data. The model is the first to consider the effect of the microstructural features of ligaments of RPCs on the elastic moduli of the bulk material.

scholarly journals Overview and comparison of modelling methods for foams

2020 ◽  
pp. 0021955X2096632
Author(s):  
Anna Hössinger-Kalteis ◽  
Martin Reiter ◽  
Michael Jerabek ◽  
Zoltán Major
Keyword(s):  
Relative Density ◽  
Elastic Properties ◽  
Material Properties ◽  
Bulk Material ◽  
Edge Length ◽  
Constitutive Modelling ◽  
The Matrix ◽  
Cell Topology ◽  
Homogenization Methods ◽  
Modelling Methods

Cellular materials, especially foams, are widely used in several applications because of their special mechanical, electrical and thermal properties. Their properties are determined by three factors: bulk material properties, cell topology and shape as well as relative density. The bulk material properties include the mechanical, thermal and electrical properties of the matrix. The cell topology determines if the foam exhibits stretch or bending dominated behaviour. The relative density corresponds to the foaming degree. It is defined by the cell edge length and cell wall thickness. Especially for the linear elastic properties there are many different modelling approaches. In general, these methods can be divided into two groups namely direct modelling, e.g. analytical and finite element models and constitutive modelling, e.g. models which are generated through homogenization methods. This paper presents an overview of the different modelling methods for foams. Furthermore, sensitivity studies are presented which enable the comparison of the models with regard to the estimation of the elastic properties, show the limits of those models and enable the investigation of the influence of the above mentioned factors on the elastic properties. Selected models are validated with experimental data of a low density foam regarding the Young’s modulus.

scholarly journals NUMERICAL SIMULATION OF THE BROKEN ROCK MASS TRANSPORTATION IN A ROTATING PIPELINE

2021 ◽  
Vol 2 (4) ◽  
pp. 141-150
Author(s):  
Guil Nam Khan ◽  
Evgeny P. Rusin
Keyword(s):  
Cross Section ◽  
Bulk Material ◽  
Longitudinal Axis ◽  
Pneumatic Conveying ◽  
Discrete Elements ◽  
Cross Sectional ◽  
Horizontal Pipe ◽  
Angular Velocities ◽  
The Cross ◽  
The Impact

The impact of the angular velocity of a horizontal pipe rotating around its longitudinal axis and the shape of its cross-section on the efficiency of pneumatic conveying of bulk material in it has been numerically investigated by the discrete elements method. The maximum number of non-contact particles, that is, particles being not in contact with other material particles and with the pipe, in the cross section of the pipe during one its revolution, is assumed the condition for effective pneumatic conveying. A method for searching for non-contact particles is proposed, which makes it possible to calculate their number at fixed pipe position angles during its rotation. For various cross-sectional shapes, the optimal angular velocities are determined at which the average number of non-contact particles in the cross-section is maximum. The results of the study can be used to increase the productivity of the removal of products of destruction when drilling horizontal boreholes in rocks and soils.

Ag effects on the elastic modulus values of nanoporous Au foams

2009 ◽  
Vol 24 (4) ◽  
pp. 1600-1606 ◽  
Author(s):  
A.M. Hodge ◽  
R.T. Doucette ◽  
M.M. Biener ◽  
J. Biener ◽  
O. Cervantes ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Relative Density ◽  
Elastic Properties ◽  
Nitrate Solution ◽  
The Other ◽  
Nitrate Salt ◽  
Depth Sensing ◽  
Cross Sectional ◽  
Sectional Analysis ◽  
Ligament Size

To study both the effect of Ag and the relative density on the elastic properties of nanoporous Au (np-Au) foams, partially as well as fully dealloyed np-Au samples with various ligament sizes were prepared. Additionally, Ag-coated np-Au samples were synthesized by immersing np-Au in a 1 M Ag nitrate solution, followed by drying and thermal decomposition of the deposited Ag nitrate salt to Ag, NO2, and O2. Cross-sectional analysis revealed that this method yields a homogeneous Ag distribution and that the Ag concentration can be adjusted within the range of 0 to 20 at.%. Mechanical testing was performed by depth-sensing nanoindentation. It was observed that the effect of the relative density on the elastic properties of np-Au seems to be much stronger than predicted by the Gibson and Ashby relationship: Even Ag contents as low as 1 at.% can significantly change the modulus values. On the other hand, the elastic modulus of np-Au seems to be independent of the ligament size.

Multidisciplinary team decision is rare and decreasing in percutaneous vascular interventions despite positive impact on in-hospital outcomes

VASA ◽  
2019 ◽  
Vol 48 (3) ◽  
pp. 262-269 ◽  
Author(s):  
Christian-Alexander Behrendt ◽  
Tilo Kölbel ◽  
Thea Schwaneberg ◽  
Holger Diener ◽  
Ralf Hohnhold ◽  
...  
Keyword(s):  
Multidisciplinary Team ◽  
Positive Impact ◽  
Cross Sectional Study ◽  
Invasive Treatment ◽  
Cross Sectional ◽  
Hospital Outcomes ◽  
Vascular Intervention ◽  
Medical Specialties ◽  
Team Decision ◽  
The Impact

Abstract. Background: Worldwide prevalence of peripheral artery disease (PAD) is increasing and peripheral vascular intervention (PVI) has become the primary invasive treatment. There is evidence that multidisciplinary team decision-making (MTD) has an impact on in-hospital outcomes. This study aims to depict practice patterns and time changes regarding MTD of different medical specialties. Methods: This is a retrospective cross-sectional study design. 20,748 invasive, percutaneous PVI of PAD conducted in the metropolitan area of Hamburg (Germany) were consecutively collected between January 2004 and December 2014. Results: MTD prior to PVI was associated with lower odds of early unsuccessful termination of the procedures (Odds Ratio 0.662, p < 0.001). The proportion of MTD decreased over the study period (30.9 % until 2009 vs. 16.6 % from 2010, p < 0.001) while rates of critical limb-threatening ischemia (34.5 % vs. 42.1 %), patients´ age (70 vs. 72 years), PVI below-the-knee (BTK) (13.2 % vs. 22.4 %), and rates of severe TASC C/D lesions BTK (43.2 % vs. 54.2 %) increased (all p < 0.001). Utilization of MTD was different between medical specialties with lowest frequency in procedures performed by internists when compared to other medical specialties (7.1 % vs. 25.7 %, p < 0.001). Conclusions: MTD prior to PVI is associated with technical success of the procedure. Nonetheless, rates of MTD prior to PVI are decreasing during the study period. Future studies should address the impact of multidisciplinary vascular teams on long-term outcomes.

Factors Influencing Academic Stress on Students of University of Economics and Business - Vietnam National University

2020 ◽  
Vol 36 (3) ◽  
Author(s):  
Nham Phong Tuan ◽  
Nguyen Ngoc Quy ◽  
Nguyen Thi Thanh Huyen ◽  
Hong Tra My ◽  
Tran Nhu Phu
Keyword(s):  
Academic Stress ◽  
Stress Factors ◽  
Negative Effects ◽  
Cross Sectional ◽  
Stress Scale ◽  
Perceptions And Attitudes ◽  
National University ◽  
Questionnaire Surveys ◽  
The University ◽  
The Impact

The objective of this study is to investigate the impact of seven factors causing academic stress on students of University of Economics and Business - Vietnam National University: Lack of leisure time, Academic performance, Fear of failure, Academic overload, Finances, Competition between students, Relationships with university faculty. Based on the results of a practical survey of 185 students who are attending any courses at the University of Economics and Business - Vietnam National University, the study assesses the impact of stress factors on students. The thesis focuses on clarifying the concept of "stress" and the stress level of students, while pointing out its negative effects on students. This study includes two cross-sectional questionnaire surveys. The first survey uses a set of 16 questions to assess students’ perceptions and attitudes based on an instrument to measure academic stress - Educational Stress Scale for Adolescents (ESSA). The second survey aims to test internal consistency, the robustness of the previously established 7-factor structure. Henceforth, the model was brought back and used qualitatively, combined with Cronbach’s Alpha measurement test and EFA discovery factor analysis. This study was conducted from October 2019 to December 2019. From these practical analyzes, several proposals were made for the society, the school and the students themselves.

The impact of the use of a footrest on the quality of chest compressions. A prospective, randomized, cross-sectional study

2018 ◽  
Vol 31 (3) ◽  
Author(s):  
Jolanta Majer ◽  
Sandra Pyda ◽  
Jerzy Robert Ladny ◽  
Antonio Rodriguez-Nunez ◽  
Lukasz Szarpak
Keyword(s):  
Cross Sectional Study ◽  
Sectional Study ◽  
Chest Compressions ◽  
Cross Sectional ◽  
The Impact

Awareness of symptomatic differences Covid-19, SARS, Swine Flu, Common cold among dental students

2020 ◽  
Vol 11 (SPL1) ◽  
pp. 1026-1033
Author(s):  
Nivedha Valliammai Mahalingam ◽  
Abilasha R ◽  
Kavitha S
Keyword(s):  
Infectious Diseases ◽  
Undergraduate Students ◽  
Common Cold ◽  
Emerging Infectious Diseases ◽  
Dental Students ◽  
Swine Flu ◽  
Viral Diseases ◽  
Surveillance Systems ◽  
Cross Sectional ◽  
The Impact

Enormous successes have been obtained against the control of major epidemic diseases, such as SARS, MERS, Ebola, Swine Flu in the past. Dynamic interplay of biological, socio-cultural and ecological factors, together with novel aspects of human-animal interphase, pose additional challenges with respect to the emergence of infectious diseases. The important challenges faced in the control and prevention of emerging and re-emerging infectious diseases range from understanding the impact of factors that are necessary for the emergence, to development of strengthened surveillance systems that can mitigate human suffering and death. The aim of the current study is to assess the awareness of symptomatic differences between viral diseases like COVID-19, SARS, Swine flu and common cold among dental students that support the prevention of emergence or re-emergence. Cross-sectional type of study conducted among the undergraduate students comprising 100 Subjects. A questionnaire comprising 15 questions in total were framed, and responses were collected in Google forms in SPSS Software statistical analysis. The study has concluded that dental students have an awareness of the symptomatic differences between infectious viral disease. The study concluded that the awareness of symptomatic differences between viral diseases like COVID-19, SARS, Swine flu, Common cold is good among the dental students who would pave the way for early diagnosis and avoid spreading of such diseases. A further awareness can be created by regular webinars, seminars and brainstorming sessions among these healthcare professionals.

Relationship between Code of Corporate Governance and Corporate Financial Performance (An Empirical Study of Food Companies Listed on KSE)

GIS Business ◽  
2017 ◽  
Vol 12 (4) ◽  
pp. 01-09
Author(s):  
Asma Rafique Chughtai ◽  
Afifa Naseer ◽  
Asma Hassan
Keyword(s):  
Corporate Governance ◽  
Stock Exchange ◽  
Securities And Exchange Commission ◽  
Executive Directors ◽  
Agency Conflicts ◽  
Cross Sectional ◽  
Return On Equity ◽  
Governance Practices ◽  
Code Of Corporate Governance ◽  
The Impact

The crucial role that implementation of Code of Corporate Governance plays on protecting the rights of minorities, shareholders, local as well as foreign investors cannot be denied. Companies all over the world are required to implement their respective Code of Corporate Governance for avoiding agency conflicts between companies management and stakeholders and for assuring transparency in accountability. This paper aims at exploring the impact of implementation of corporate governance practices (designed by Securities and Exchange Commission of Pakistan) have on the financial position of companies. For explanatory variables of the study, composition of the board as per the Code of Corporate Governance that comprises of presence of independent, executive and non-executive directors has been taken into consideration. Return on equity has been taken as an indicator of firms profitability i.e. the dependent variable. For this study, companies listed on food producing sector of Karachi Stock Exchange have been screened for excogitation of the relationship. It is an empirical research based on nine years data from 2007–2015. Using Hausman Test for selecting the data analysis technique between Fixed or Random, Fixed Cross Sectional Panel Analysis has been used for analysis of the data collected. Findings indicate that presence of independent, executive and non-executive directors as per the code requirements levies a significant impact on the profitability of companies indicated by return on equity. It is, thus concluded that companies should ensure compliance with code of governance practices to reduce not only the agency issues but also to increase their profitability.

Diversity and the Performance of Selected Financial Institutions of Asia

2018 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Shafaque Fatima ◽  
Saqib Sharif
Keyword(s):  
Financial Institutions ◽  
Positive Impact ◽  
Financial Institution ◽  
Gender Diversity ◽  
Business Case ◽  
Ordinary Least Squares ◽  
Cross Sectional ◽  
Age Diversity ◽  
The Impact ◽  
Nationality Diversity

Linking with the business case for diversity, this study examines whether the top management team (TMT) and the board of directors (BODs) diversity has a positive impact on financial institution (FI) performance in select countries of Asia least researched domain. We use data from 119 financial institutions across Asia for the year 2015, initially 1,447 institutions; however, incomplete data was excluded from final analysis. We use three proxies for diversity, that is, nationality diversity, gender diversity, and age diversity of TMT and BODs. To investigate the impact of TMT and BODs diversity, cross-sectional ordinary least-squares estimation is applied, using Return on Average Assets (ROAA%) as a measure of performance.  We find that nationality diversity and age diversity is positively and significantly related to FIs performance. Our evidence indicates that executives and board members with diverse exposure and younger age improve FIs profitability. However, there is no significant relationship between gender and FIs performance.

Sign in / Sign up

Export Citation Format

Share Document