Experimental Analysis of Damping across Joints in Metal Plates

2006 ◽  
Vol 5-6 ◽  
pp. 391-398 ◽  
Author(s):  
S.J.I. Walker ◽  
G.S. Aglietti ◽  
P.R. Cunningham
Keyword(s):  
Experimental Approach ◽  
Dynamic Behaviour ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Advantages And Disadvantages ◽  
Metal Plates ◽  
Engineering Sciences ◽  
Wide Range ◽  
Vibration Problems ◽  
The One

In the current world of engineering, structural vibration problems continue impact the design and construction of a wide range of products. Amid the parameters that determine the dynamic behaviour of a structure the one that takes into account the dissipation of energy resulting in the decay of the vibration is the least understood and the most difficult to quantify [1]. The estimation of damping factors is of interest in most branches of engineering sciences. In the field of aircraft structures the damping directly affects the fatigue life, a parameter which is applied conservatively due to the inherent complexity in modelling the damping of built up structures and the potentially catastrophic consequences of a fatigue failure. One of the most important problems is the limited knowledge of how joints affect the damping of the complete structure. This work therefore addresses this issue and focuses on the damping of joints in metal plates as part of a larger project to investigate the damping of built up structures. Various plate configurations are experimentally investigated using two different approaches. The results from the configurations are compared and discussed along with the advantages and disadvantages of each experimental approach. This enables a link to be identified between the damping magnitudes and the mode shapes and joint stiffnesses.

Theoretical Research on Two Improved Optimal Sensor Placement Methods

2013 ◽  
Vol 351-352 ◽  
pp. 1122-1129 ◽  
Author(s):  
Wei Liu ◽  
Wei Cheng Gao ◽  
Hui Li
Keyword(s):  
Kinetic Energy ◽  
Computational Simulation ◽  
Multiple Input Multiple Output ◽  
Sensor Placement ◽  
Theoretical Research ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Optimal Sensor Placement ◽  
Advantages And Disadvantages ◽  
Improved Methods

Optimal sensor placement technique plays a key role in structural health monitoring and structural vibration control. Based on the advantages and disadvantages of effective independence (EI) and modal kinetic energy (MKE) methods, two improved optimal sensor placement methods which are Effective Independence - Average Acceleration Amplitude (EI-AAA) method and Effective Independence - Modal Kinetic Energy (EI-MKE) method are proposed in this paper. Firstly the formulas are deduced from modal expansion of multiple-input-multiple-output (MIMO) displacement frequency response function matrix. Then a computational simulation of steel cross beam structure has been implemented to demonstrate the feasibility of the two improved methods above. The obtained optimal sensor locations using the two improved methods are compared with those gained by EI method and MKE method. Finally six classical comparison criteria are employed to demonstrate the advantage and disadvantage of these four methods. The results showed that some innovations proposed in this paper are effective and reliable. The two improved optimal sensor placement methods (EI-AAA method and EI-MKE method) can not only make the truncated mode shapes as linearly independent as possible but also enable the measured modal kinetic energy to maintain the maximum value.

scholarly journals On the shape of resolvent modes in wall-bounded turbulence

2019 ◽  
Vol 877 ◽  
pp. 682-716 ◽  
Author(s):  
Scott T. M. Dawson ◽  
Beverley J. McKeon
Keyword(s):  
Differential Operator ◽  
Royal Society ◽  
Resolvent Operator ◽  
Large Scale ◽  
Stokes Equations ◽  
Mode Shapes ◽  
Navier Stokes ◽  
Mathematical Framework ◽  
Engineering Sciences ◽  
Wide Range

This work develops a methodology for approximating the shape of leading resolvent modes for incompressible, quasi-parallel, shear-driven turbulent flows using prescribed analytic functions. We demonstrate that these functions, which arise from the consideration of wavepacket pseudoeigenmodes of simplified linear operators (Trefethen, Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, vol. 461, 2005, pp. 3099–3122. The Royal Society), give an accurate approximation for the energetically dominant wall-normal vorticity component of a class of nominally wall-detached modes that are centred about the critical layer. We validate our method on a model operator related to the Squire equation, and show for this simplified case how wavepacket pseudomodes relate to truncated asymptotic expansions of Airy functions. Following the framework developed in McKeon & Sharma (J. Fluid Mech., vol. 658, 2010, pp. 336–382), we next apply a sequence of simplifications to the resolvent formulation of the Navier–Stokes equations to arrive at a scalar differential operator that is amenable to such analysis. The first simplification decomposes the resolvent operator into Orr–Sommerfeld and Squire suboperators, following Rosenberg & McKeon (Fluid Dyn. Res., vol. 51, 2019, 011401). The second simplification relates the leading resolvent response modes of the Orr–Sommerfeld suboperator to those of a simplified scalar differential operator – which is the Squire operator equipped with a non-standard inner product. This characterisation provides a mathematical framework for understanding the origin of leading resolvent mode shapes for the incompressible Navier–Stokes resolvent operator, and allows for rapid estimation of dominant resolvent mode characteristics without the need for operator discretisation or large numerical computations. We explore regions of validity for this method, and show that it can predict resolvent response mode shape (though not necessary the corresponding resolvent gain) over a wide range of spatial wavenumbers and temporal frequencies. In particular, we find that our method remains relatively accurate even when the modes have some amount of ‘attachment’ to the wall, and that that the region of validity contains the regions in parameter space where large-scale and very-large-scale motions typically reside. We relate these findings to classical lift-up and Orr amplification mechanisms in shear-driven flows.

scholarly journals Teaching in Vocational Schools: Educational Alignment versus the Promotion of Talents

2013 ◽  
Vol 1 (1) ◽  
pp. 9-13
Author(s):  
Tina Koppitz
Keyword(s):  
Professional Identity ◽  
Education System ◽  
Teaching And Learning ◽  
The Other ◽  
Learning Theories ◽  
Learning Program ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Educational Alignment ◽  
The One

Teaching and learning has fundamentally changed in the last thirty years. In this period, a wide range of novel teaching theories has been established. Recent research states that a teachers professional identity consists of a cognitive, psychological and also a social perspective. The identity of a teacher emerges when s/he interacts with his/her students or other people. As a result of these interactions, teachers treat the questions “who are they? and who do they want to become?. These questions pose different views on educational methodologies today. On the one side some professionals argue for learning in a community which supports establishing an average basis of knowledge among all pupils. This approach especially helps the struggling pupils, since a key component is that pupils learn from each other and align their knowledge. On the other side, however, others vote for an individual learning program. Here, in particular talents are promoted. The question is, what approach is more promising for the society of tomorrow. This work deals with the underlying theories, discusses the advantages and disadvantages of these learning theories and, as an example, additionally incorporates a focused view on the Austrian education system

scholarly journals THE GAZE OF SCHROEDINGER’S CAT: EYE-TRACKING IN PSYCHOLINGUISTICS

2018 ◽  
Author(s):  
Tatiana Chernigovskaya ◽  
◽  
Svetlana Alexeeva ◽  
Anzhalika Dubasava ◽  
Tatiana Petrova ◽  
...  
Keyword(s):  
Visual Perception ◽  
Eye Tracking ◽  
Language Processing ◽  
Experimental Studies ◽  
Text Type ◽  
Advantages And Disadvantages ◽  
Cognitive Studies ◽  
New Information ◽  
Wide Range ◽  
The One

The book addresses the study of reading mechanisms and visual perception using the method of eye-tracking. The authors conduct their research in the Laboratory for Cognitive Studies of Saint Petersburg State University that was the first in Russia to utilize eye-tracking in experimental studies of language more than 15 years ago. Psycholinguistic experiments aimed at analyzing reading in Russian are described; a systematic description of factors which influence reading process at different stages and linguistic levels from a single letter to a coherent text is provided. The mechanisms of separate graphemes recognition, activation and competition processes in word recognition, contextual integration processes, syntactic parsing, and anaphora resolution in eye-tracking experiments are described. The influence of the text type on its processing is demonstrated, the advantages and disadvantages of the infographics compared to verbal text are described, the relationship between visual perception of images and their verbalization is discussed. The significant role of context is highlighted: on the one hand, it helps the reader to anticipate new information, and on the other hand, it enables different multiple interpretations of a sentence or text. In the book a virtual assistant — Schroedinger’s cat — is used as a model of a subject who processes and transmits information. The book will appeal to linguists and cognitive psychologists who use eye-tracking in their research, as well as for the wide range of those who are interested in objective methods of studying language processing and human behavior.

Kinematic Analysis of a Novel Rimless Wheel With Independently Actuated Spokes

2005 ◽  
Author(s):  
Doug Laney ◽  
Dennis Hong
Keyword(s):  
Contact Point ◽  
Point Contact ◽  
Static Stability ◽  
Advantages And Disadvantages ◽  
Contact Points ◽  
Straight Line ◽  
Wide Range ◽  
Kinematic Analyses ◽  
General Mobility ◽  
The One

One of the major limitations of mobile robots for unstructured environments is their lack of general mobility. Wheeled, treaded, and legged robots each have their advantages and disadvantages, but they all lack the flexibility to be able to cope with a wide range of terrain. The actuated spoke wheel concept is presented in this paper as an alternative locomotive method that allows multiple modes of motion, which give it the ability to stride quickly using one contact point per wheel, walk with static stability with two contact points per wheel, or assume a stable stance using three contact points per wheel. This paper presents the preliminary kinematic analyses of the actuated spoke wheel with no-slip constraints at the ground contacts for a robot using a two actuated spoke wheel configuration. Straight-line motion and considerations for turning are discussed for the one- and two-point contact schemes followed by recommendations for future study.

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

Hybrid polymer composite materials. Part 2. Preparation technology

2020 ◽  
pp. 8-13
Keyword(s):  
Composite Materials ◽  
Impact Toughness ◽  
Polymer Composites ◽  
The Other ◽  
Polymer Materials ◽  
Hybrid Polymer ◽  
Preparation Technology ◽  
Advantages And Disadvantages ◽  
Hybrid Polymer Composite ◽  
The One

The main methods (pressing and winding) of the processing of hybrid polymer composites to obtain items were examined. Advantages and disadvantages of the methods were noted. Good combinations of different-module fibers (carbon, glass, boron, organic) in hybrid polymer materials are described, which allow one to prepare materials with high compression strength on the one hand, and to increase fracture energy of samples and impact toughness on the other hand.

The Management of Post-Tonsillectomy Morbidity in Patients With Sleep Apnoea

2019 ◽  
Vol 70 (10) ◽  
pp. 3738-3740
Keyword(s):  
Day Surgery ◽  
Sleep Apnoea ◽  
Integrative Approach ◽  
Multicenter Studies ◽  
Therapeutic Modalities ◽  
Advantages And Disadvantages ◽  
Obstructive Sleep ◽  
Wide Range ◽  
The Impact ◽  
Surgery Center

The Tonsillectomy in children or adults is an intervention commonly encountered in the ENT (Ear Nose and Throat) and Head and Neck surgeon practice. The current tendency is to perform this type of surgery in major ambulatory surgery centers. Two objectives are thus pursued: first of all, the increase of the patient quality of life through the reintegration into the family as quickly as possible and secondly, the expenses associated with continuous hospitalization are reduced. Any tertiary (multidisciplinary) sleep center must ensure the complete diagnosis and treatment (including surgery) of sleep respiratory disorders. Under these conditions the selection of patients and especially the implementation of the specific protocols in order to control the postoperative complications it becomes essential. The present paper describes our experience of tonsillectomy as treatment for selected patients with chronic rhonchopathy (snoring) and mild to moderate obstructive sleep apnoea. It was presented the impact of antibiotics protocols in reducing the main morbid outcomes following tonsillectomy, in our day surgery center. The obtained results can also be a prerequisite for the integrative approach of the patients with sleep apnoea who were recommended surgical treatment. Considering the wide range of therapeutic modalities used in sleep apnoea, each with its specific advantages and disadvantages, more extensive and multicenter studies are needed. Keywords: post-tonsillectomy morbidity, day surgery center, sleep disorders

A Review of Drug Side Effect Identification Methods

2020 ◽  
Vol 26 (26) ◽  
pp. 3096-3104 ◽  
Author(s):  
Shuai Deng ◽  
Yige Sun ◽  
Tianyi Zhao ◽  
Yang Hu ◽  
Tianyi Zang
Keyword(s):  
Side Effects ◽  
Future Research ◽  
Drug Side Effects ◽  
Important Indicator ◽  
Advantages And Disadvantages ◽  
Key Points ◽  
Network Methods ◽  
Future Research Directions ◽  
The One ◽  
Approved Drugs

Drug side effects have become an important indicator for evaluating the safety of drugs. There are two main factors in the frequent occurrence of drug safety problems; on the one hand, the clinical understanding of drug side effects is insufficient, leading to frequent adverse drug reactions, while on the other hand, due to the long-term period and complexity of clinical trials, side effects of approved drugs on the market cannot be reported in a timely manner. Therefore, many researchers have focused on developing methods to identify drug side effects. In this review, we summarize the methods of identifying drug side effects and common databases in this field. We classified methods of identifying side effects into four categories: biological experimental, machine learning, text mining and network methods. We point out the key points of each kind of method. In addition, we also explain the advantages and disadvantages of each method. Finally, we propose future research directions.

scholarly journals Modes of Interaction in Naturally Occurring Medical Encounters With General Practitioners: The “One in a Million” Study

2021 ◽  
pp. 104973232199379
Author(s):  
Olaug S. Lian ◽  
Sarah Nettleton ◽  
Åge Wifstad ◽  
Christopher Dowrick
Keyword(s):  
General Practitioners ◽  
Narrative Analysis ◽  
Mode Competition ◽  
General Applicability ◽  
Naturally Occurring ◽  
Wide Range ◽  
The One ◽  
Narrative Mode ◽  
Modes Of Interaction

In this article, we qualitatively explore the manner and style in which medical encounters between patients and general practitioners (GPs) are mutually conducted, as exhibited in situ in 10 consultations sourced from the One in a Million: Primary Care Consultations Archive in England. Our main objectives are to identify interactional modes, to develop a classification of these modes, and to uncover how modes emerge and shift both within and between consultations. Deploying an interactional perspective and a thematic and narrative analysis of consultation transcripts, we identified five distinctive interactional modes: question and answer (Q&A) mode, lecture mode, probabilistic mode, competition mode, and narrative mode. Most modes are GP-led. Mode shifts within consultations generally map on to the chronology of the medical encounter. Patient-led narrative modes are initiated by patients themselves, which demonstrates agency. Our classification of modes derives from complete naturally occurring consultations, covering a wide range of symptoms, and may have general applicability.

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