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1
Content available remote Theoretical construction of stable traversable wormholes
100%
Open Physics
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2010
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tom 8
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nr 3
364-368
EN
It is shown in this paper that it is possible, at least in principle, to construct a traversable wormhole that is stable to linearized radial perturbations by specifying relatively simple conditions on the shape and redshift functions.
2
Content available remote The stability study of a plane engine
100%
EN
We study the dynamical properties of a plane engine vibrations modelled by a system of ODE.
EN
Stability problems concerning the functional equations of the form f(2x + y) = 4ƒ(x) + ƒ(y) + ƒ(x + y) - ƒ(x - y), and ƒ(2x + y) + ƒ(2x -y) = 8ƒ(x) + 2ƒ(y) are investigated. We prove that if the norm of the difference between the LHS and the RHS of one of equations (1) or (2), calculated for a function g is say, dominated by a function φ in two variables having some standard properties then there exists a unique solution ƒ of this equation and the norm of the difference between g and ƒ is controlled by a function depending on φ.
4
Content available Stability of free-floating ship. Part II
100%
EN
This is the second part of the paper published in Polish Maritime Research no. 2/2005, dealing with the calculation problem of righting arms of the free-floating ship, i.e. longitudinally balanced at any heel angle. In such case the righting arms are ambiguous as they depend on a way the heeling moment acts. Two cases were considered: when the heeling moment is parallel to the ship plane of symmetry, and the case when it performs the least work, i.e. when the moment is parallel to the main axis of ship waterline. It was demonstrated that angular translations (heel and trim) are then the Euler angles associated with a relevant reference axis. Some cases of the incorrect defining and using of those angles in today design practice were indicated. The most important features of the curve of righting arms of free-floating ship were demonstrated.
5
Content available Stability of free-floating ship. Part I
100%
EN
Problem of calculation of righting arms of the free-floating ship, i.e. longitudinally balanced at any heel angle, was formulated. In such a case of particular interest for a ship in the damage condition, the righting arms are ambiguous as they depend on a way the heeling moment acts. Two cases were considered: when the heeling moment is parallel to the ship plane of symmetry, and the case when it performs the least work, i.e. when the moment is parallel to the main axis of ship waterplane. It was demonstrated that angular translations (heel and trim) are then the Euler angles associated with a relevant reference axis. Some cases of the incorrect defining and using of those angles in today design practice were indicated. The most important features of the curve of righting arms of free-floating ship were demonstrated.
6
Content available On the stability for pancyclicity
100%
EN
A property P defined on all graphs of order n is said to be k-stable if for any graph of order n that does not satisfy P, the fact that uv is not an edge of G and that G + uv satisfies P implies $d_G(u) + d_G(v) < k$. Every property is (2n-3)-stable and every k-stable property is (k+1)-stable. We denote by s(P) the smallest integer k such that P is k-stable and call it the stability of P. This number usually depends on n and is at most 2n-3. A graph of order n is said to be pancyclic if it contains cycles of all lengths from 3 to n. We show that the stability s(P) for the graph property "G is pancyclic" satisfies max(⎡6n/5]⎤-5, n+t) ≤ s(P) ≤ max(⎡4n/3]⎤-2,n+t), where t = 2⎡(n+1)/2]⎤-(n+1).
7
Content available remote On the stability of orthogonal additivity
100%
EN
We deal with the stability of the orthogonal additivity equation, presenting a new approach to the proof of a 1995 result of R, Ger and the second author. We sharpen the estimate obtained there. Moreover, we work in more general settings, providing an axiomatic framework which covers much more cases than considered before by other authors.
EN
The aim of this paper is to study the superstability problem of the d’Alembert type functional equation f(x+y+z)+f(x+y+σ(z))+f(x+σ(y)+z)+f(σ(x)+y+z)=4f(x)f(y)f(z) $$f(x + y + z) + f(x + y + \sigma (z)) + f(x + \sigma (y) + z) + f(\sigma (x) + y + z) = 4f(x)f(y)f(z)$$ for all x, y, z ∈ G, where G is an abelian group and σ : G → G is an endomorphism such that σ(σ(x)) = x for an unknown function f from G into ℂ or into a commutative semisimple Banach algebra.
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2000
|
tom Vol. 48, nr 4
587-593
EN
This paper gives a necessary and sufficient condition for the Hurwitz stability of interval matrices [formulas], where [formula] are symmetrizable by the matrix [formula]. This result is a generalization of the papers [3], [4], where it was assumed that the matrices [formula] are symmetric.
PL
Zwrócono uwagę na niektóre problemy związane ze stabilnością ruchu, a w szczególności na uniwersalność metody Lapunowa, podkreślono możliwości tej metody, która w połączeniu z metodą linearyzacji nie tyle daje odpowiedź czy ruch układu jest stabilny, czy nie, ale również może dawać odpowiedź na wiele pytań dotyczących obszaru stabilności i szybkości zaniku procesów przejściowych, zamieszczono dwa przykłady, które są ilustracją rozważań teoretycznych.
EN
Some problems associated with the stability of motion, in particular the universality of the direct Lapunow's method. Possibilities of this method which, combined with the linearization method, not only answers whether or not the motion of a system is stable, but also can answer many questions concerned with the area of stability and the rate of decay of transients. Two examples ilustrate the theoretical considerations.
EN
In the past photoactive pigments have been surface passivated to reduce the photoactivity and thereby to avoid chalking. In new applications highly photoactive types of these pigments are used on glass or ceramic substrates for self cleaning and pollution reduction purposes. This initiated attempts to develop photoactivity test devices. In this contribution a test chamber method is presented which is based on a previous setup. The samples are placed in a chamber where various climatic and atmospheric conditions can be applied and controlled including exposure to model pollutants. During irradiation by UV light a FTIR spectrometer records the amount of pollutants and their decomposition products. This technique does not only allow to follow the photoactivity of the pigment and pigmented coating regarding the decomposition of model pollutants, but also to determine the photocatalytic stability of coatings by detecting products of the decomposition of the polymeric binder.
PL
Pigmenty fotoaktywne były dawniej pasywowane powierzchniowo w celu zmniejszenia ich aktywności fotokatalitycznej i tym samym uniknięcia kredowania. W nowych zastosowaniach pigmenty o dużej aktywności fotokatalitycznej wykorzystuje się na podłoża szklane i ceramiczne, w celu uzyskania właściwości samoczyszczących i odporności na zabrudzenia. Takie wykorzystanie pigmentów zainicjowało próby opracowania urządzeń do badania fotoaktywności. Przedstawiono komorową metodę badawczą, opartą na wcześniej opracowanym urządzeniu. Próbki umieszcza się w komorze, w której można modelować i kontrolować różne warunki atmosferyczne, obejmujące narażenia na modelowe zanieczyszczenia. Za pomocą spektrometru FTIR rejestruje się, podczas naświetlania próbek promieniami UV, ilość zanieczyszczeń i produktów ich rozkładu. Metoda ta pozwala nie tylko na śledzenie fotokatalitycznej aktywności pigmentu i pigmentowanych powłok na podstawie rozkładu modelowych zanieczyszczeń, ale również na oznaczenie fotokatalitycznej stabilności powłok, poprzez wykrywanie produktów rozkładu polimeru spoiwa.
12
Content available Stability of selenium diet supplement
80%
EN
Selenium is one of the trace elements playing a crucial role in a proper function of living organisms. Selenium intake varies, largely based on the selenium content of food. The daily Se intake recommended for adults amounts to 55 μg per day. The mean level of selenium in the population varies considerably between countries. Recent studies on the selenium dietary intakes in Poland showed that it is not sufficient to meet the daily requirement for this microelement so it is strongly recommended to employ selenium supplementation. The commercial product SEL-BRCA1®  being a selenium diet supplement was subjected to chemical and microbial analysis to determine its stability in storage time and conditions. Basing on the obtained results it can be stated that the stability of studied supplement, stored in the closed bottles, can be confirmed for the period of time up to 45 months after the production date and it is not recommended to store opened bottles for the period of time longer than 12 months. The studied supplement showed a very high microbial stability what underscores its usefulness as human medicines.
13
Content available remote Some families of pseudo-processes
80%
EN
We introduce several types of notions of dis persive, completely unstable, Poisson unstable and Lagrange uns table pseudo-processes. We try to answer the question of how many (in the sense of Baire category) pseudo-processes with each of these properties can be defined on the space $ℝ^m$. The connections are discussed between several types of pseudo-processes and their limit sets, prolongations and prolongational limit sets. We also present examples of applications of the above results to pseudo-processes generated by differential equations.
14
Content available remote New stability results of picard iteration for contractive type mappings
80%
EN
There exists several concepts of stability for fixed point iterative methods in literature. The aim of this paper is to compare two such concepts, namely one due to Harder and the second one due to Rus, in the class of contractive mappings.
15
Content available remote Extended continuous block backward differentiation formula for stiff systems
80%
EN
We present an Extended Continuous Block Backward Differentiation Formula (ECBBDF) of order k+1 for the numerical solution of stiff ordinary differential equations. This is achieved by constructing an Extended Continuous Backward Differentiation formula (ECBDF) together with the additional methods from its first derivative and are combined to form a single block of methods that simultaneously provide the approximate solutions for the stiff Initial Value Problems (IVPs). The error constant and stability property of the (ECBBDF) is discussed. We use the specific cases k = 4 and k = 5 to illustrate the process. The performance of the method is demonstrated on some numerical examples to show the accuracy and efficiency advantages of the method.
16
Content available remote Stability of positive continuous-time linear systems with delays
80%
|
2009
|
tom Vol. 57, nr 4
395-398
EN
The asymptotic stability of positive continuous-time linear systems with delays is addressed. It is shown that: 1) the asymptotic stability of the positive systems with delays is independent of their delays, 2) the checking of the asymptotic stability of the positive systems with delays can be reduced to checking of the asymptotic stability of positive systems without delays. Simple stability conditions for the positive systems with delays are give and illustrated by numerical examples.
EN
Adopting a longitudinal design, this study investigates the effects of foreign language anxiety on foreign language proficiency over time within English and Japanese learning contexts. It also explores the stability of anxiety in English and Japanese over time and the stability of anxiety across English and Japanese. Chinese university students (N=146), who were simultaneously learning Japanese and English, participated in this study. Data were collected twice over a 2-month interval, using the Foreign Language Classroom Anxiety Scale, the English Proficiency Scale, and the Japanese Proficiency Scale. Results showed that anxiety changes had a significantly negative, but weak, correlation with the development of overall proficiency and the proficiency in sub- skills such as reading or speaking, for both English and Japanese, suggesting the interference of anxiety with proficiency levels. Anxiety in Japanese tended to decrease significantly over time, but no significant change was found for English. Furthermore, no significant difference between anxiety in Japanese and English was found at either testing time.
18
Content available remote Unbounded stability of two-term recurrence sequences modulo $2^k$
80%
EN
In this paper, the observer-based control for a class of uncertain linear systems is considered. Exponential stabilizability for the system is studied and reduced-order observer is discussed. Numerical examples are given to illustrate obtained results.
20
Content available remote Stabilization of nucleated polypropylene
80%
EN
The stabilizing packages have been worked out to obtain nucleated polypropylene of high thermal stability. It was shown that the proposed stabilizing package applied to nucleated polypropylene allows to remanufacture polypropylene wastes formed during moulding.
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