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1

Influence of the specific load on stability and vibrations of the multimember column with internal cracks

Sokół Krzysztof, Kuliński Krzysztof

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2023

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Vol. 71, nr 4

art. no. e146408

EN

Slender systems are mostly studied when Euler’s load or follower load is considered. The use of those types of external loads results in well-known divergence or flutter shape of the characteristic curve. In this study, one takes into account the specific load which allows one to obtain an interesting divergence – pseudo flutter shape of characteristic curves on the external load–vibration frequency plane. The curves can change inclination angle as well as one can observe the change in vibration modes along them. The shape of those curves depends not only on the parameters of the slender system but also on loading heads that induce the specific load. In this study, one considers the slender multimember system in which cracks are present and weaken the host structure. The results of theoretical as well as numerical simulations are focused on the influence of the parameters of the loading heads on vibrations, stability, and loading capacity of the investigated system as well as on the possibility of partial reduction of unwanted crack effect.

2

Robust estimation of the spherical normal distribution

Castilla Elena

Mathematica Applicanda

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2022

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Vol. 50, no. 1

43--63

EN

This paper develops a new family of estimators, the minimum density power divergence estimators, for the parameters of the Spherical Normal Distribution. This family contains the maximum likelihood estimator as a particular case. The robustness is empirically illustrated through a Monte Carlo simulation study and two biological numerical examples. Tools needed to implement these methods are also provided.

PL

Artykuł przedstawia nową rodzinę estymatorów parametrów sferycznego rozkładu normalnego minimalnej dywergencji. Ta rodzina obejmuje estymator największej wiarygodności jako przypadek szczególny. Odporność tych estymatorów jest zilustrowana empirycznie przez badanie symulacyjne Monte Carlo. Zamieszczone przykłady dla danych rzeczywistych dotyczą zagadnień z biologii. Pokazano również narzędzia potrzebne do wdrożenia tych metod.

3

Pomiar poziomu koncentracji potencjału rozwojowego regionów w Polsce: wartość i dynamika w latach 2010-2017 oraz prognoza do 2020 r

Nadolny Michał

Biuletyn Komitetu Przestrzennego Zagospodarowania Kraju PAN

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2019

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No 273

44-58

EN

The aim of the paper is to measure and forecast concentration of regional development potential on a regional basis. The study covered 14 GUS features, which measure the development potential. The forecast, nominal values and processes’ dynamics were calculated for data from 2010 to 2020, using author made method. The study reveals that key factors determining the diversification of the distribution of the potential include the relation of large agglomerations to their regional surroundings. Therefore, we are dealing with growth poles with different impact levels. Since 2010, the process of concentrating potential in Poland has taken different directions. In poorly developed regions, we observe constant distribution values. Most regions, especially those with medium and high levels of economic development, are characterized by a dynamic increase in the level of concentration 5% to 6% annually. This means that the growth poles «move away» from their surroundings and strengthen their position. Simultaneously, they slightly reduce the distance to the strongest developed region in Poland (Mazowsze). By 2020, these trends will remain unchanged, however regions with a moderately low level of development will observe the fastest growth.

4

Solving the stationary hydroaeroelasticity problem for dynamic deflection elements of separation devices

Pavlenko I., Liaposhchenko A., Ochowiak M., Demyanenko M.

Vibrations in Physical Systems

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2018

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Vol. 29

art. no. 2018026

EN

The paper presents a method for expanding the working range of separation elements, where the separation is conducted through the use of inertia particles. The presented dynamic separation elements work as the automatic control system (the regulating action is the elastic energy; the regulation object is the hydraulic resistance). It was taken the first step to the engineering method development for their calculation using analytical dependences of the finite element method. The critical velocity of the gas-liquid flow was determined, that causes a divergence phenomenon of dynamic separation device elements and expressions for generalized forces for the system “gas-liquid flow is a dynamic deflection element.” Two-knot finite elements with two degrees of freedom (transverse displacement and angle of the cross-section rotation) were used for dynamic deflection elements. The given number of degrees of freedom of the mechanical system “gas-liquid flow is a dynamic deflection element” due to the consideration of the transverse deformations of the plate allows simplifying the mathematical model. It was suggested to use aerohydroplastic phenomena of dynamic non-stability of dynamic deflection elements of separating devices, analogous to the method of applying acoustic oscillations to a heterogeneous stream, for the coagulation of dispersed particles in the flow.

5

Vibrations and Stability of a Column Subjected to the Specific Load Realized by Circular Elements of Heads

Tomski L., Uzny S.

Mechanics and Mechanical Engineering

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2013

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Vol. 17, nr 2

197--206

EN

Research into columns subjected to a specific load considering a constructional solution consisting of circular elements is an aim of the paper. The boundary problem of stability and free vibrations of the considered system for a generalised load by a force directed towards the positive pole was formulated on the basis of Hamilton’s principle. The boundary conditions concerning the load by a follower force directed towards the positive pole were deduced on the basis of the boundary conditions of the column subjected to a generalised load by a force directed towards the positive pole. In this paper, the load by the follower force was treated as a special case of the generalised load by a force directed towards the positive pole. Apart from the formulation of and solution to the boundary problem of the columns subjected to the specific load, the results of numerical computations connected to the static problem and free vibrations of the considered systems were also presented.

6

On asymmetric I and I∗-divergence

Ghosal S., Pal S. K.

Demonstratio Mathematica

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2013

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Vol. 46, nr 1

137--147

EN

In this paper we introduce and study the concepts of I-divergence and I∗-divergence of sequences as well as double sequences in an asymmetric metric spaces. We investigate the interrelationship between I-divergence and I∗-divergence and show that they are equivalent under some condition and prove some basic properties of these concepts.

7

Przyczyny rozbieżności bilansu zużycia wody

Koral W.

Wodociągi - Kanalizacja

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2008

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nr 12

36-38

8

Dokładne wyznaczanie rozbieżności

Karnasiewicz P.

Studia Informatica

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2008

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Vol. 29, nr 4A

31-42

PL

Rozbieżność jest pewną miarą jakości rozkładów próbek wyrażoną jako supremum. Przybliżone wyznaczanie tego supremum polega generalnie na porównywaniu objętości dużej liczby losowo wybranych zbiorów ze z góry obranej rodziny do liczby próbek, które w tych zbiorach się zawierają. W niniejszej pracy została wyprowadzona i przedstawiona numeryczna metoda dokładnego wyznaczania rozbieżności z użyciem najpopularniejszych rodzin zbiorów.

EN

Discrepancy is a measure of quality of samples distribution expressed as a supremum. In general, estimating this supremum relies on comparing volumes of many randomly chosen sets from some given family to quantity of samples belonging to these sets. In this paper, a numerical method of precise determinating discrepancy using the most popular families of sets will be introduced.

9

Influence of Selected Machine and Material Parameters on the Stitch Length and Its Irregularity

Vobolis J., Jucienė M., Punys J., Vaitkevičius V.

Fibres & Textiles in Eastern Europe

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2003

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Vol. 11, no. 3 (42)

50--55

EN

One of the main demands for sewing garment quality is good-looking seams, the appearance of which is greatly influenced by the stability of stitch length. The method and equipment for measuring stitch length in the seam are presented. The article reveals the influence of fabric tensile stiffness, friction force, and sewing speed upon the stability of stitch length. Experimental results evidently prove that the mean stitch length decreases and the stitch length variance increases as the fabric tensile stiffness grows. However, the mean stitch length increases and the stitch length variance tends to decrease as the fabric external friction grows. The rotational speed of the main shaft also has a great influence on the process. The increase in the rotational speed of the main shaft increases both the mean stitch length and the stitch length variance. Thus, in order to obtain good-looking seams it is very important to evaluate the forces acting in the sewing process, sewing speed, etc.

PL

Jednym z podstawowych wymogów w stosunku do jakości szytej odzieży jest dobrze wyglądający ścieg, którego wygląd w dużej mierze zależy od stabilności jego długości. W artykule zaprezentowano metodę i oprzyrządowanie do pomiaru długości ściegu w szwie, nierównomierność ściegu ma tendencję do wzrostu przy wzroście sztywności tkaniny. Natomiast przy wzroście sił tarcia średnia długość ściegu i jego nierównomierność wzrasta. Prędkość obrotowa wału głównego również ma duży wpływ na proces szycia. Jej wzrost powoduje zarówno wzrost średniej długości ściegu, jak i nierównomierność i grubości. Dlatego też, aby otrzymać dobrze wyglądający szew, ważne jest określenie szybkości szycia i sił występujących w tym procesie.