scholarly journals Dynamic multi-patch isogeometric analysis of planar Euler-Bernoulli beams

2021 ◽  
Author(s):  
Duy Vo ◽  
Aleksandar Borković ◽  
Pruettha Nanakorna ◽  
Tinh Quoc Bui
Keyword(s):  
Dynamic Analysis ◽  
Degrees Of Freedom ◽  
Simple Relation ◽  
Bernoulli Beam ◽  
Control Variables ◽  
Cross Sectional ◽  
Beam Structures ◽  
And Performance ◽  
And Control ◽  
Euler Bernoulli Beam

This study presents a novel isogeometric Euler-Bernoulli beam formulation for in-plane dynamic analysis of multi-patch beam structures. The kinematic descriptions involve only displacements of the beam axis, which are approximated by non-uniform rational B-spline (NURBS) curves. Translational displacements of the control points are here considered as control variables. The motivation of this work is to propose a penalty-free method to handle in-plane dynamic analysis of multi-patch beam structures. A simple relation between cross-sectional rotations at the ends of the beams and control variables is derived, allowing the incorporation of the end rotations as degrees of freedom. This improved setting can straightforwardly tackle beam structures with many rigid multi-patch connections, a major challenging issue when using existing isogeometric Euler-Bernoulli beam formulations. Additionally, rotational boundary conditions are conveniently prescribed. Numerical examples with complicated beam structures such as circular arches and frames with kinks are considered to show the accuracy and performance of the developed formulation. The computed results are verified with those derived from the conventional finite element method, and the superior convergence properties of the proposed formulation are illustrated. We additionally discuss about the possible extension of the present approach to spatial beam structures.

scholarly journals Soft Spherical Tensegrity Robot Design Using Rod-Centered Actuation and Control

2016 ◽  
Author(s):  
Lee-Huang Chen ◽  
Kyunam Kim ◽  
Ellande Tang ◽  
Kevin Li ◽  
Richard House ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Space Exploration ◽  
Robot Design ◽  
The Novel ◽  
Flexible Design ◽  
Spherical Robot ◽  
Potential Benefits ◽  
And Performance ◽  
And Control

This paper presents the design, analysis and testing of a fully actuated modular spherical tensegrity robot for co-robotic and space exploration applications. Robots built from tensegrity structures (composed of pure tensile and compression elements) have many potential benefits including high robustness through redundancy, many degrees of freedom in movement and flexible design. However to fully take advantage of these properties a significant fraction of the tensile elements should be active, leading to a potential increase in complexity, messy cable and power routing systems and increased design difficulty. Here we describe an elegant solution to a fully actuated tensegrity robot: The TT-3 (version 3) tensegrity robot, developed at UC Berkeley, in collaboration with NASA Ames, is a lightweight, low cost, modular, and rapidly prototyped spherical tensegrity robot. This robot is based on a ball-shaped six-bar tensegrity structure and features a unique modular rod-centered distributed actuation and control architecture. This paper presents the novel mechanism design, architecture and simulations of TT-3, the first untethered, fully actuated cable-driven six-bar tensegrity spherical robot ever built and tested for mobility. Furthermore, this paper discusses the controls and preliminary testing performed to observe the system’s behavior and performance.

scholarly journals Knowledge, Performance, and Attitude Towards Mask Use to Prevent and Control COVID-19 Outbreak Among a Group of Iranian People: A Cross-sectional Study

2021 ◽  
Vol In Press (In Press) ◽  
Author(s):  
Abdolhamid Tajvar ◽  
Teamur Aghamolaei ◽  
Shokrollah Mohseni ◽  
Anahita Fakherpour ◽  
Zabihollah Damiri ◽  
...  
Keyword(s):  
Cross Sectional Study ◽  
Online Questionnaire ◽  
Cross Sectional ◽  
Educational Levels ◽  
Final Score ◽  
Knowledge And Attitude ◽  
And Performance ◽  
And Control ◽  
Do So ◽  
Good Attitude

Background: Due to the pandemic, COVID-19 cases and deaths are increasing unexpectedly and precipitately. More importantly, asymptomatic carriers could infect healthy people through sneezing, coughing, and talking. Therefore, mask usage is required to prevent and control COVID-19. Objectives: This study was aimed at examining the knowledge, attitude, and performance levels (KAP) of the Iranian population regarding mask usage to prevent and control the COVID-19 outbreak during a one-month period from early April to early May 2020. Methods: A researcher-made, validated, and reliable questionnaire consisting of 30 questions on knowledge, attitude, and performance regarding mask usage was utilized. Data collection was performed through the online method. To do so, the online questionnaire link was provided for the participants via social networks. The correct and wrong answers were scored 1 and 0 points, respectively. The final score of each dimension was calculated and classified as 0 - 50% (low), 51 - 75% (moderate), and 75% > (good). Results: A total of 1581 participants took part in the study. Although the participants had good attitude (74%) and performance (70.80%), but only 13.70% of them had good knowledge regarding mask usage. Also, significant differences were found between the participants’ knowledge and higher educational levels (P < 0.001). There were significant associations between the participants’ age, gender, educational level, and job and their knowledge and attitude levels (P < 0.05). Besides, female participants had higher performance scores than did male participants (P < 0.001). The participants with governmental jobs had significantly higher performance than unemployed ones (P < 0.001). Conclusions: The participants obtained low KAP scores; therefore, it is required to train and inform the society and enhance their KAP levels via social media regarding the importance of mask usage, including proper donning, doffing, cleaning, disinfection, and safely and hygienic disposal procedures of masks to prevent and control COVID-19.

Asymmetric Bifurcation of Initially Curved Nanobeam

2015 ◽  
Vol 82 (9) ◽  
Author(s):  
X. Chen ◽  
S. A. Meguid
Keyword(s):  
Symmetry Breaking ◽  
Degrees Of Freedom ◽  
Surface Elasticity ◽  
Beam Theory ◽  
Surface Effects ◽  
Beam Model ◽  
Bernoulli Beam ◽  
Reduced Order ◽  
Euler Bernoulli Beam ◽  
Bifurcation Behavior

In this paper, we investigate the asymmetric bifurcation behavior of an initially curved nanobeam accounting for Lorentz and electrostatic forces. The beam model was developed in the framework of Euler–Bernoulli beam theory, and the surface effects at the nanoscale were taken into account in the model by including the surface elasticity and the residual surface tension. Based on the Galerkin decomposition method, the model was simplified as two degrees of freedom reduced order model, from which the symmetry breaking criterion was derived. The results of our work reveal the significant surface effects on the symmetry breaking criterion for the considered nanobeam.

Medium Frequency Vibration Analysis of Beam Structures Modeled by the Timoshenko Beam Theory

2020 ◽  
Author(s):  
Yichi Zhang ◽  
Bingen Yang
Keyword(s):  
Shear Deformation ◽  
Timoshenko Beam ◽  
Vibration Analysis ◽  
Beam Theory ◽  
Timoshenko Beam Theory ◽  
Bernoulli Beam ◽  
Beam Structure ◽  
Medium Frequency ◽  
Beam Structures ◽  
Euler Bernoulli Beam

Abstract Vibration analysis of complex structures at medium frequencies plays an important role in automotive engineering. Flexible beam structures modeled by the classical Euler-Bernoulli beam theory have been widely used in many engineering problems. A kinematic hypothesis in the Euler-Bernoulli beam theory is that plane sections of a beam normal to its neutral axis remain normal when the beam experiences bending deformation, which neglects the shear deformation of the beam. However, as observed by researchers, the shear deformation of a beam component becomes noticeable in high-frequency vibrations. In this sense, the Timoshenko beam theory, which describes both bending deformation and shear deformation, may be more suitable for medium-frequency vibration analysis of beam structures. This paper presents an analytical method for medium-frequency vibration analysis of beam structures, with components modeled by the Timoshenko beam theory. The proposed method is developed based on the augmented Distributed Transfer Function Method (DTFM), which has been shown to be useful in various vibration problems. The proposed method models a Timoshenko beam structure by a spatial state-space formulation in the s-domain, without any discretization. With the state-space formulation, the frequency response of a beam structure, in any frequency region (from low to very high frequencies), can be obtained in an exact and analytical form. One advantage of the proposed method is that the local information of a beam structure, such as displacements, bending moment and shear force at any location, can be directly obtained from the space-state formulation, which otherwise would be very difficult with energy-based methods. The medium-frequency analysis by the augmented DTFM is validated with the FEA in numerical examples, where the efficiency and accuracy of the proposed method is present. Also, the effects of shear deformation on the dynamic behaviors of a beam structure at medium frequencies are illustrated through comparison of the Timoshenko beam theory and the Euler-Bernoulli beam theory.

Influence of Axial Force and Initial Curvature on the Flexural Deflection of Euler-Bernoulli Beam Structures Solved by DQEM Using EDQ

2006 ◽  
Author(s):  
Chang-New Chen
Keyword(s):  
Axial Force ◽  
Offshore Structures ◽  
Differential Quadrature ◽  
Analysis Model ◽  
Bernoulli Beam ◽  
Beam Structures ◽  
Initial Curvature ◽  
Differential Quadrature Element Method ◽  
Governing Differential Equation ◽  
Euler Bernoulli Beam

The influence of axial force and initial curvature on the flexural deflection of Euler-Bernoulli beam structures is analyzed by differential quadrature element method (DQEM) using extended differential quadrature (EDQ). The DQEM uses the differential quadrature to discretize the governing differential equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient. The theory presented in the paper can be used to effectively obtain accurate results in analyzing the offshore structures.

Influence of Axial Force on the Vibration of Euler-Bernoulli Beam Structures Solved by DQEM Using EDQ

2006 ◽  
Author(s):  
Chang-New Chen
Keyword(s):  
Boundary Conditions ◽  
Axial Force ◽  
Differential Quadrature ◽  
Analysis Model ◽  
Bernoulli Beam ◽  
Beam Structures ◽  
Differential Quadrature Element Method ◽  
Quadrature Element Method ◽  
Euler Bernoulli Beam ◽  
Element Boundary

The influence of axial force on the vibration of Euler-Bernoulli beam structures is analyzed by differential quadrature element method (DQEM) using extended differential quadrature (EDQ). The DQEM uses the differential quadrature to discretize the governing differential eigenvalue equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.

Influence of Axially Distributed Force on the Vibration of Euler-Bernoulli Beam Structures Solved by DQEM Using EDQ

2007 ◽  
Author(s):  
Chang-New Chen
Keyword(s):  
Boundary Conditions ◽  
Numerical Algorithm ◽  
Differential Quadrature ◽  
Analysis Model ◽  
Bernoulli Beam ◽  
Beam Structures ◽  
Differential Quadrature Element Method ◽  
Quadrature Element Method ◽  
Euler Bernoulli Beam ◽  
Element Boundary

The influence of axially distributed force on the vibration of Euler-Bernoulli beam structures is analyzed by differential quadrature element method (DQEM) using extended differential quadrature (EDQ). The DQEM uses the differential quadrature to discretize the governing differential eigenvalue equation defined on each element, the transition conditions defined on the inter-element boundary of two adjacent elements and the boundary conditions of the beam. Numerical results solved by the developed numerical algorithm are presented. The convergence of the developed DQEM analysis model is efficient.

scholarly journals Budgetary Control and Performance: the Case of Councils in Mezam and Momo Divisions of Cameroon

2018 ◽  
Vol 7 (3) ◽  
pp. 36
Author(s):  
Samuel Tanjeh Mukah
Keyword(s):  
Public Sector ◽  
Control Variables ◽  
Public Sector Management ◽  
North West ◽  
The North ◽  
West Region ◽  
Budgetary Control ◽  
And Performance ◽  
And Control ◽  
The Relationship

The pursuit of quality service delivery in the public sector management in Cameroon necessitated the decentralisation of public sector management by transferring more power and resources to the local councils. This is in a bid to make them more self-governing. These councils are expected to meet the aspirations of their municipalities by carrying out approved projects efficiently and effectively. In this regard, this paper sets out to investigate the relationship between budgetary control and performance of local councils in Mezam and Momo Divisions of the North West Region of Cameroon, and the challenges these councils encounter in the process of budgetary control. Data was collected through a survey and analysed using the Ordinary Least Square (OLS) estimation technique to regress the relationship between the budgetary control variables and council performance. The empirical results showed that the key budgetary control variables (planning, participation, monitoring and control, motivation, communication, and responsibility) have a positively and statistically significant effect on performance of the councils. Effective performance of local councils in Mezam and Momo Divisions of the North West Region of Cameroon could then be attributed to effective presence of budgetary control requiring the availability of financial resources rationally allocated, qualified and experienced personnel, participation of all responsibility center managers in the planning and control processes, and regular communication and motivation of the council staff. 

Preliminary Study of a Centrifugal Compressor With Counter-Rotating Impellers: Design and Performances Study

2020 ◽  
Author(s):  
Abed Cheikh Brahim ◽  
Khelladi Sofiane ◽  
Deligant Michael ◽  
El Marjani Abdel ◽  
Farid Bakir
Keyword(s):  
Centrifugal Compressor ◽  
Degrees Of Freedom ◽  
Numerical Data ◽  
Centrifugal Impeller ◽  
Through Flow ◽  
Aerodynamic Performances ◽  
Preliminary Study ◽  
And Performance ◽  
And Control ◽  
Selection Of

Abstract Turbomachinery with double counter-rotating impellers offer more degrees of freedom in the choice of design and control parameters compared to conventional machines. For these innovative machines, the literature review shows that more published works are available concerning axial type turbomachines than centrifugal ones. This work deals with a preliminary design and performance analysis applied to two counter-rotating impellers of a centrifugal compressor. We present here the design practice developed based on 0D/1D models, also coupled with optimization and stream-curvature through-flow methods to satisfy the selected design-criteria. An analyze of aerodynamic performances results are made and compared to those available experimental and numerical data of a baseline configuration, composed of one centrifugal-impeller and a volute. The compressor studied here includes a first conventional impeller with an axial inlet and a mixed or centrifugal outlet. The second impeller is designed parametrically and can be considered as a rotating-diffuser with a radial or mixed inlet and outlet. Ultimately, the numerical simulation results of a selection of candidate solutions are discussed.

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