1. On Cases of Instability in Open Structures

1888 ◽  
Vol 14 ◽  
pp. 106-106
Author(s):  
E. Sang
Keyword(s):  
Linear Structures ◽  
Symmetric Structure ◽  
Linear Resistance ◽  
Open Structures ◽  
Extensive Class ◽  
The Subject ◽  
The Stability ◽  
Special Case

AbstractIn the course of some remarks on the design proposed for the Forth Bridge, the author of this paper had enunciated the remarkable theorem, that any symmetric structure built on a rectangular base, and depending on linear resistance alone, is necessarily unstable. The proof of it, given in the eleventh volume of the Transactions of the Royal Scottish Society of Arts, is derived from considerations affecting the special case; but this theorem is only one of an extensive class, and therefore the subject of instability among linear structures in general is here taken up.In the case of regular or semi-regular arrangements, having the corners of an upper supported from the corners of an under polygon, it is shown that when the figures are of odd numbers the structures are stable, while those with even numbers are unstable ; unless indeed the polygons be placed conformably, in which case the stability extends to both classes.

scholarly journals XVI.—On Cases of Instability in Open Structures

1888 ◽  
Vol 33 (2) ◽  
pp. 321-333
Author(s):  
E. Sang
Keyword(s):  
Longitudinal Strain ◽  
Point Of View ◽  
Symmetric Structure ◽  
Open Structures ◽  
Extensive Class ◽  
The Subject ◽  
General Abstract

In the course of some remarks on the scheme proposed for the Forth Bridge, which remarks are published in the eleventh volume of the Transactions of the Royal Scottish Society of Arts, I was led to enunciate, among other theorems, one of a somewhat unexpected character, to the effect that any symmetric structure built on a rectangular basis, having no redundant parts, and depending on longitudinal strain alone, is necessarily unstable. This theorem was established by arguments restricted to the single matter under consideration; it is one of an extensive class, and I now propose to discuss the subject from a general abstract point of view.

A vortex ring on a sphere: the case of total vorticity equal to zero

2019 ◽  
Vol 377 (2158) ◽  
pp. 20190019 ◽  
Author(s):  
Stefanella Boatto ◽  
Carles Simó
Keyword(s):  
Vortex Ring ◽  
Vortex Dynamics ◽  
Polar Vortex ◽  
Nice Property ◽  
Theme Issue ◽  
Central Vortex ◽  
Atmospheric Observations ◽  
The Subject ◽  
The Stability ◽  
Special Case

The stability of a ring of vortices has attracted the interest of researchers for over a century. Recent beautiful observations of polygonal configurations of vortices present in the atmospheres of Jupiter and Saturn, and of polygonal jets in the Earth's atmosphere, have revived the interest in the subject. In the observed cases, the vortex ring is in the presence of a central vortex. We present analytical and numerical results about the linear, spectral and Lyapunov stability of a ring in the presence of polar vortices. Motivated by both atmospheric observations we considered the special case of total vorticity equal to zero. Such a case has also the very nice property of being universal , i.e. not depending on a choice of gauge. We considered the two cases of fixed and non-fixed polar vortices. A ring in the northern (respectively, southern) hemisphere is stabilized by the presence of a northern (respectively, southern) polar vortex of suitable strength, in agreement with what is observed numerically and atmospherically. This article is part of the theme issue ‘Topological and geometrical aspects of mass and vortex dynamics’.

Unbounded Linear Operators

2018 ◽  
Author(s):  
D. E. Edmunds ◽  
W. D. Evans
Keyword(s):  
Hilbert Spaces ◽  
Linear Operators ◽  
Von Neumann ◽  
Limit Circle ◽  
Sectorial Operators ◽  
Closed Operators ◽  
The Stability ◽  
Symmetric Operators ◽  
Unbounded Linear Operators ◽  
Special Case

This chapter is concerned with closable and closed operators in Hilbert spaces, especially with the special classes of symmetric, J-symmetric, accretive and sectorial operators. The Stone–von Neumann theory of extensions of symmetric operators is treated as a special case of results for compatible adjoint pairs of closed operators. Also discussed in detail is the stability of closedness and self-adjointness under perturbations. The abstract results are applied to operators defined by second-order differential expressions, and Sims’ generalization of the Weyl limit-point, limit-circle characterization for symmetric expressions to J-symmetric expressions is proved.

Bankenwettbewerb und die Stabilität von Finanzsektoren

2021 ◽  
Vol 70 (1) ◽  
pp. 1-36
Author(s):  
Toni Richter
Keyword(s):  
Economic Policy ◽  
Precise Measurement ◽  
Policy Discourse ◽  
Competitive Effect ◽  
Too Big To Fail ◽  
Financial Systems ◽  
The Subject ◽  
State Of Research ◽  
The Stability ◽  
Elementary Basis

Abstract Since the financial crisis of 2008 and intensified during the corona crisis, the interdependence between the stability of the financial systems and the prevailing degree of competition (DC) has been the subject of scientific and economic policy discourse on fragmented markets and „too-big-to-fail“ banks. In theory and empiricism, two fundamentally contrary causal concepts are opposed, the elementary basis of which is the precise measurement of the DC: Competition-stability- versus Fragility-Hypothesis. Based on the recent state of research, it can be shown that alternative DC-Measurements consistently show significantly different competitive conditions and in consequence the evidence for or against a stability-enhancing competitive effect seems to be predetermined by the chosen DC-Measurement.

Adhesion of Fine Particles at Solid/Solution Interfaces

MRS Bulletin ◽  
1990 ◽  
Vol 15 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Nikola Kallay
Keyword(s):  
Fine Particles ◽  
Plane Surface ◽  
Solid Surfaces ◽  
Liquid Media ◽  
Latex Dispersions ◽  
Colloid Particles ◽  
The Subject ◽  
Kinetic Investigations ◽  
The Stability ◽  
Kinetics Of

The adhesion of particles at solid surfaces in liquid media has attracted the attention of scientists because of its various applications as well as the theoretical significance of the processes involved. Early studies were characterized either by poorly defined systems or limited by the properties of a few morphologically well-defined model colloids, such as latex dispersions. Consequently, results were either of semiquantitative nature or were related to some specific cases, which eluded general conclusions. New methods for preparing uniform particles of different compositions, shapes, and sizes make it possible to approach the problem in a more comprehensive manner. For example, to demonstrate difficulties caused by polydispersity, it is sufficient to mention that the electrostatic interaction energy between a plane surface and a particle is approximately proportional to the particle radius, yet the rate of deposition depends exponentially on the height of the energy barrier.In principle, static and dynamic approaches may be employed in the study of particle adhesion. The static method yields the force required to detach an adhered particle, while kinetic investigations of attachment and detachment give the rates of the respective processes. Both methods offer information on the stability of the system in terms of the bond strength of adhered solids. For small colloid particles, which are the subject of thermal random Brownian motion, the dynamic approach is more appropriate. This article emphasizes the kinetics of deposition and detachment of small colloid particles in liquid media.

THE ROLE OF ACCOUNTING AND CONTROL IN THE MANAGEMENT OF ECONOMIC SECURITY OF AN ORGANIZATION

2021 ◽  
Vol 7 (2) ◽  
pp. 165-178
Author(s):  
Nicolay T. Labyntsev ◽  
Lyubov F. SHILOVA ◽  
Ocsana V. Chukhrova
Keyword(s):  
Economic Security ◽  
Accounting Profession ◽  
Economic Management ◽  
Economic Interests ◽  
Doing Business ◽  
The Subject ◽  
The Stability ◽  
High Level ◽  
And Control

This article revises the mission and the name of the accounting profession in the context of strengthening the economic security of enterprises under the conditions of digitalization of the economy. The authors note that in the contemporary conditions of economic management, enterprises should form and ensure the functioning of the economic security of the enterprise at the proper level. The necessity of in-depth research of economic security at microlevel was considered, the factors influencing the stability of the enterprise were highlighted. High level of economic security of the subject of management consists in guaranteeing him maximum effective and stable functioning now and in future. Subjects of economic security were individual enterprises, and objects — their economic interests. The main goals of ensuring economic security of the enterprise in the part of accounting were singled out, the tasks of accounting policy, aimed at ensuring economic security, were determined. The prospects of the accounting profession in the process of ensuring economic security and reliable safe presentation of the results of doing business in reporting are substantiated. The study contains proposals on the revision of requirements for the qualifications of accountants in order to emphasize their activities aimed at strengthening the economic security of the enterprise.

Existence of Periodic Solution for Equation of Motion of Simple Beams With Harmonically Variable Length

1995 ◽  
Author(s):  
Ebrahim Esmailzadeh ◽  
Gholamreza Nakhaie-Jazar ◽  
Bahman Mehri
Keyword(s):  
Periodic Solution ◽  
Fixed Point ◽  
Nonlinear Function ◽  
Axial Direction ◽  
Equation Of Motion ◽  
The Other ◽  
Sufficient Condition ◽  
Vibrating String ◽  
The Stability ◽  
Special Case

Abstract The transverse vibrating motion of a simple beam with one end fixed while driven harmonically along its axial direction from the other end is investigated. For a special case of zero value for the rigidity of the beam, the system reduces to that of a vibrating string with the corresponding equation of its motion. The sufficient condition for the periodic solution of the beam is then derived by means of the Green’s function and Schauder’s fixed point theorem. The criteria for the stability of the system is well defined and the condition for which the performance of the beam behaves as a nonlinear function is stated.

Kinematic Investigation of the Deployable Bennett Loop

2006 ◽  
Vol 129 (6) ◽  
pp. 602-610 ◽  
Author(s):  
J. Eddie Baker
Keyword(s):  
Full Advantage ◽  
Spatial Displacement ◽  
Learning Tool ◽  
Working Mechanism ◽  
Efficient Treatment ◽  
Kinematic Characteristics ◽  
The Subject ◽  
The Many ◽  
Special Case

Despite the many studies devoted to it and its value as a learning tool, the Bennett linkage has never been employed as a working mechanism. It has recently found favor, however, among structural analysts as a possible unit in deployable networks owing to the potential for true spatial displacement without flexure. Although the loop can be analyzed in this application by means of purely geometrical methods, a wealth of kinematic examinations is available for more efficient treatment. The particular form that the chain must adopt as a deployable object and the special case of the linkage demanded by the purpose constitute the subject of the present exposition, which takes full advantage of prior analyses of the chain’s kinematic characteristics.

scholarly journals New DTC strategy of multi-machines single-inverter systems for electric vehicle traction applications

2020 ◽  
Vol 11 (2) ◽  
pp. 641
Author(s):  
Taibi Ahmed ◽  
Hartani Kada ◽  
Allali Ahmed
Keyword(s):  
Electric Vehicle ◽  
Control Strategy ◽  
Control Structure ◽  
Synchronous Machines ◽  
Permanent Magnet Synchronous Machines ◽  
Structure Control ◽  
The Subject ◽  
Simulation Results ◽  
The Stability ◽  
Traction System

In high power traction system applications two or more machines are fed by one converter. This topology results in a light, more compact and less costly system. These systems are called multi-machines single-converter systems. The problems posed by different electrical and mechanical couplings in these systems (MMS) affect various stages of the systems and require control strategy to reduce adverse effects. Control of multi-machines single-converter systems is the subject of this paper. The studied MMS is an electric vehicle with four in-wheel PMS motors. A three-leg inverter supplies two permanent magnet synchronous machines which are connected to the front right and rear right wheels, and another inverter supplies the left side. Several methods have been proposed for the control of multi-machines single-inverter systems, the master-slave control structure seems best adapted for our traction system. In this paper, a new control structure based on DTC method is used for the control of bi-machine traction system of an EV. This new control has been implanted in simulation to analyze its robustness in the presence of the various load cases involved in our electric vehicle traction chain. Simulation results indicated that this structure control allowed the stability of the traction system.

scholarly journals Det första nationella provet i samhällskunskap - en studie i bedömarsamstämmighet

2018 ◽  
Vol 12 (4) ◽  
pp. 13
Author(s):  
Arne Löfstedt
Keyword(s):  
Interrater Reliability ◽  
Intraclass Correlation ◽  
Ninth Graders ◽  
National Agency ◽  
Final Grade ◽  
The Subject ◽  
And Mathematics ◽  
The Stability ◽  
National Tests ◽  
National Test

Skolämnet samhällskunskap som eget ämne existerar i princip enbart i de nordiska länderna. I många andra länder delar flera skolämnen på ämnesinnehållet, till exempel geografi och civics. Ämnesinnehållet är stort och genomgår ständig förändring. År 2013 genomfördes de första nationella proven i samhällskunskap i Sverige för årskurs 9. Med tanke på ämnets karaktär kan det vara speciellt viktigt att undersöka om dessa prov är ”rättvisa.” Avsikten med denna studie är att undersöka en aspekt av denna ”rättvisa”, nämligen interbedömarstabilitet, dvs om samma elevsvar ger upphov till samma bedömning oavsett bedömare. Skolverket i Sverige genomförde 2009 en större studie av de ämnen som då genomförde nationella prov och föreliggande studie försöker dels efterlikna och dels bygga ut upplägget från Skolverket. Studien genomfördes på de första nationella proven i samhällskunskap 2013. Genom att pröva olika reliabilitetsmått inom kategorierna ”consensus estimates”, och ”consistency estimates” analyseras resultaten, bland annat diskuteras måttet intraclass correlation. Syftet är också, då detta var de första proven, att skapa en ram för återkommande studier av Interbedömarreliabilitet. Upplägget med en större mängd lärare som genomför totalt tre bedömningar av de utvalda hela proven försöker också efterlikna bedömningssituationen ute på skolorna såtillvida att det var relativt många lärare med i studien, och de kom från olika skolor spridda över Sverige. Genom detta testas också bedömningsanvisningarnas stabilitet. Själva genomförandet var omfattande och tog två hela dagar. Resultaten pekar på en god överensstämmelse för provbetyget, det sammanfattande omdöme eleverna får. Studien avses att återupprepas under kommande år.Nyckelord: Samhällskunskap, nationella prov, interbedömarreliabilitet, intraclass correlationThe first national test in samhällskunskap – a study of interrater reliabilityAbstractThe Swedish school subject Samhällskunskap (Societal knowledge) exists basically only in the Nordic countries. In other countries a number of different subjects, such as geography and civics, share the content. The content of the subject is constantly changing, depending on how society is changing. The first national tests in Samhällskunskap for all Swedish ninth graders took place in 2013. A large part of the test contains constructed responses.  Given the characteristics of the subject we consider it especially important to investigate whether these tests are “fair” or not. The intent of this study is to investigate one aspect of “fairness”, interrater reliability, meaning the degree to which the same student responses are scored equally by different raters.  In 2009, the National Agency of Education in Sweden conducted a large study of the subjects Swedish, English and Mathematics. Our study aims to mimic and further develop the design of the study from 2009. Our study was carried out on the first national tests in 2013. The results were analyzed by exploring different reliability measures within the categories consensus estimates, and consistency estimates. As the 2013 tests were the first tests of its kind in Sweden the purpose was also to create a framework for regular studies of interrater reliability. The rater design with a relatively large number of teachers from all over the country, each assessing a total of three complete student test responses aimed at mimicking the way the tests are assessed in schools. This also allowed us to study the stability of our assessment rubrics. The study itself was extensive and took two days to perform. The results indicate a large compliance when it comes to the final grade of the test. The study is meant to be repeated in the coming years.Keywords: Social science, civics, national testing, interrater reliability, intraclass correlation

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