Wyniki wyszukiwania - Biblioteka Nauki

1

Variational Method of Finding Streamlines in Ring Cascades for Creeping Flows

100%

Tesch K. , Banaszek M.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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tom Vol. 15, No 1

71-84

EN

This paper presents a new analytical method of finding streamlines for creeping flows in a ring cascade composed of an infinite number of infinitely thin blades. An analytical solution was obtained by minimizing the dissipation functional by means of the variational calculus. The necessary condition for the optimum of the functional yields the Stokes equation after certain additional assumptions are introduced. We considered different variants of fixing of the inlet and outlet of the cascade.

2

On invariants of fluid mechanics tensors

100%

Tesch K.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2013

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tom Vol. 17, No 3-4

223--230

EN

This paper presents physical interpretations of the first and second invariants of tensors of fluid mechanics. Some examples of elementary applications and meanings are also given.

3

Stability of (Y-Q) characteristic

100%

Pochyly F. , Haluza M.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2008

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tom Z. 10, Vol. 2

149-156

EN

For the impeller pumps is very important to have the stable (Q,Y) characteristic. In this article is derived the influence of dissipative energy on (Q,Y) stability and main results for terms affecting this phenomenon.

4

Matematyczny opis niegładkich charakterystyk konstytutywnych ciał odkształcalnych

100%

Grzesikiewicz W. , Zbiciak A.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2004

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tom z. 23

161-166

PL

W pracy są prezentowane cztery modele ciał odkształcalnych, których charakterystyki konstytutywne opisywane są za pomocą nierówności wariacyjnych. Rozważono dwa ciała sprężyste, których stan odkształceń jest ograniczony (ciało z lockingiem) lub jest ograniczony stan naprężenia (ciało pseudosprężyste). Przedstawiono wariacyjny opis dyssypacyjnych cech ciała plastycznego i nieholonomicznego. Pokazano, iż opis cech rozważanych ciał można przedstawić przy użyciu nieróżniczkowalnych funkcjonałów energii lub dyssypacji. Rozważane formy opisu właściwości sprężysto-dyssypacyjnych umożliwiają modelowanie cech wielu nieklasycznych materiałów stosowanych w budownictwie lub budowie maszyn.

EN

In the paper we present four different models of deformable bodies. The constitutive characteristics of each one are described using variational inequalities. Two various models of elastic materials are presented in the paper. In the first one the strain state is constrained (locking material). In the case of the second one the stress state is constrained (pseudoelastic material). Additionally the variational description of two dissipative materials is presented -plastic material and non-holonomic material. It was proved that the description of these four models can be done using non-differentiable functionals of energy or dissipation. The method we propose can be used in order to formulate constitutive relations of various materials used in civil and mechanical engineering.

5

Dissipation and coupled fields

100%

Kotowski R.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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2004

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tom Z. 81

71-101

EN

The evolution criterion and the variational formulation of the coupled phenomena in the materials with the inner structure are presented. The evolution criterion, as formulated by Glansdorff and Prigogine, allows to find the kinetic potential descrobing a dissipative process. This paper deals with the construction of the kinetic potential for micropolar media embedded in the dielectric fluid and subjected to the coupled field interactions. Generalization deals with the dissipative mechanical, thermal,and electromagnetic processes occurring in the micropolar medium. The formulated criterion is aplied to obtain the equilibrium conditions for micropolar elastic solids, micropolar electromagnetic fluids, and liquid crystals.The variational principle is constructed for micropolar media in external fields of forces on the example of liguid crystals subjected to the influence of thermal and electromagnetic fields. The problem of the dissipative processes produced in liquid crystals by the exernal end internal fields is considered.

6

Energy consumption in mechanical systems using a certain nonlinear degenerate model

88%

Jamroziak K. , Bocian M. , Kulisiewicz M.

Journal of Theoretical and Applied Mechanics

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2013

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tom Vol. 51 nr 4

827--835

EN

In modern engineering materials used for creating effective ballistic shields, the issues of evaluation of their energy consumption are extremely important. The paper presents a new way of solving this problem using a certain degenerate model with dry friction. This metod involves the use of specially derived identification equations which describe the decrease in potential energy of the system during its vibratory motion induced by a single pulse load. Analytical considerations have been verified using a computer simulation technique for selected examples.

7

Matematyczny opis dyssypacji energii w maszynach roboczych

88%

Grzesikiewicz W.

Problemy Maszyn Roboczych

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2001

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tom Z. 18

41-50

PL

Dyssypacja energii jest jednym z podstawowych procesów energetycznych związanym z funkcjonowaniem maszyn. W pracy przedstawiono wielkości fizyczne, za pomocą których opisuje się dyssypacyjne charakterystyki układów fizycznych. Ponadto są rozpatrywane zasady formułowania matematycznego opisu dyssypacji. Zwrócono uwagę na uniwersalność przytoczonych zasad, które nie zależą od formy dyssypowanej energii. Wiele miejsca poświęcono opisowi rozpraszania energii mechanicznej w rezultacie tarcia suchego.

EN

The dissipation is one of the fundamental energetic processes, connected with the machine operation. In the paper there are presented physicaI quantities, with which the dissipative characteristics of physicaI systems are described. Apart from this, the principles of mathematicaI formuIation of dissipation are considered. A special attention is paid to the energy dissipation by dry friction. It has been, that presented principles are versatile as they do not depend on the form of dissipation.

8

Risk management system references in construction

88%

Tkachenko V. , Klymchuk M. , Tkachenko I. , Ilina T.

Research Papers in Economics and Finance

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2020

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tom 4

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nr 1

21-29

EN

The article examines the basic methods of risk management in construction: risk aversion, localization, dissipation,compensation. The methods are adapted to the specificity of construction companies, taking into account the main directions of their development. For the purpose of effective risk management, formalized functional structuring of risk management in construction is proposed, which will enable the implementation of management functions at two levels – executive and coordinating, with the help of a special structural component in the enterprise management system or a specialized unit in the organizational structure.

9

Simulations of behaviour of granular bodies using a lattice-gas automaton

88%

Kozicki J. , Tejchman J.

Archives of Hydro-Engineering and Environmental Mechanics

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2005

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tom Vol. 52, nr 1

21-37

EN

A lattice-gas automaton of hydrodynamics was used to calculate the kinematics of non-cohesive granular materials during 3 different complex two-dimensional problems: granular pile, granular flow in a vertical channel and granular flow in a parallel/converging silo. In the model, collisions and dissipation of particles were taken into account. The simulation results were qualitatively compared with experimental results.

10

Experimental study of hydraulic response of smooth submerged breakwaters to irregular waves

88%

Mahmoudof S. M. , Hajivalie F.

Oceanologia

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2021

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tom No. 63 (4)

448--462

EN

This paper presents the results of a laboratory experiment on transmission, reflection, and dissipation of irregular waves over smooth impermeable submerged breakwaters. Experiments included 75 JONSWAP-based irregular waves with five different wave characteristics generated at three water depths in a 2D wave flume. The investigated breakwater sections were three rectangular breakwaters with different widths, a toothed rectangular breakwater, and a trapezoidal breakwater with a slope of 1:2. A new comprehensive dimensionless parameter (β) was proposed representing both wave hydrodynamic and breakwater geometry characteristics. This parameter could be employed as a suitable descriptive option to make an accurate estimate of the hydraulic performances of submerged breakwaters. The β parameter is composed of four conventional simple dimensionless variables. However, the results revealed that the relative submergence depth significantly affects the hydraulic responses of submerged breakwaters. The transmission, reflection and dissipation of waves show a logarithmic growth, a logarithmic reduction, and a quadratic decreasing trend against the increasing of β parameter, respectively. The verifications of results revealed the high efficiency of β parameter for data reported by Carevic et al. (2013) with R2 = 0.88 and high agreement with predictions made by Van der Meer et al. (2005) formulation with R2 = 0.93.

11

Dissipation of pore water pressure in the theory of Biot

88%

Kaminski R. , Wozniak M.

Annals of Warsaw Agricultural University. Land Reclamation

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1986

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tom 22

12

Energia dyssypacji pierścienia włóknistego krążka międzykręgowego

75%

Żak M.

Aktualne Problemy Biomechaniki

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2010

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tom z. 4

285--288

PL

Znajomość właściwości mechanicznych pierścienia włóknistego krążka międzykręgowego odgrywa istotne znaczenie w określeniu przyczyn powstawania zmian degeneracyjnych w czasie pracy kręgosłupa. Badania zewnętrznej struktury poprawnego fizjologicznie krążka międzykręgowego przeprowadzono w teście jednoosiowego rozciągania. Z otrzymanych charakterystyk mechanicznych wyznaczono zmiany wartości siły oraz energię dyssypacji.

EN

Knowledge of mechanical properties of annulus fibrosus play essential role to understanding effect of degenerative changes in the intervertebral disc at work of the spine. Samples of outer annulus fibrosus nondegenerate discs were tested destructively in uniaxial tensile tests. From the mechanical characteristics curves were determined: value of load and energy dissipation.

13

Effect of radiatlon and viscous dissipation on convection flow in a vertical porous channel

75%

Malashetty M. S. , Swamy M.

International Journal of Applied Mechanics and Engineering

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2007

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tom Vol. 12, no 4

1049-1060

EN

The effect of radiation on a combined free and forced convection flow of a Boussinesq fluid through a vertical porous channel with viscous and Darcy dissipation is investigated analytically. The temperature of the walls is assumed to be equal and vary linearly with the height of the wall. Closed form solutions are obtained using a perturbation method valid for smalI values of the Eckert number. The effects of radiation, the porous parameter and Prandtl number on the velocity, temperature, flow rate and rate of heat transfer are presented graphically.

14

Review of Lattice Boltzmann Method Applied to Computational Aeroacoustics

75%

Shao W. , Li J.

Archives of Acoustics

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2019

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tom Vol. 44, No. 2

215--238

EN

This paper presents the research studies carried out on the application of lattice Boltzmann method (LBM) to computational aeroacoustics (CAA). The Navier-Stokes equation-based solver faces the difficulty of computational efficiency when it has to satisfy the high-order of accuracy and spectral resolution. LBM shows its capabilities in direct and indirect noise computations with superior space-time resolution. The combination of LBM with turbulence models also work very well for practical engineering machinery noise. The hybrid LBM decouples the discretization of physical space from the discretization of moment space, resulting in flexible mesh and adjustable time-marching. Moreover, new solving strategies and acoustic models are developed to further promote the application of LBM to CAA.

15

Assessment of Napropamide Dissipation and its Effect on Soil Enzymatic Activity

75%

Onyszko M. , Telesiński A. , Płatkowski M. , Stręk M. , Śnioszek M.

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tom Vol. 18, nr 6

64--70

EN

This paper assesses the dissipation of napropamide and its impact on the activity of dehydrogenases, alkaline phosphatase, acid phosphatase, and urease in sandy clay loam. The experiment was carried out on soil samples with organic carbon content of 12.08 g·kg-1, total nitrogen content of 0.97 g·kg-1, and pH 5.24 with the following variable factors: (a) dose of Devrinol 450 SC formation (containing 450 g of naprop-amide in dm3): 0 (control), 0.5, 1, 2, 4, 8, and 16-fold hold of field dose; (b) day of experiment: 1, 7, 14, 28, 56, and 112. The half-life of napropamide ranged from 33.50 to 71.42 days. The use of napropamide at the dose recommended by the manufacturer and at the dose reduced by half appeared to exhibit low toxicity in relation to enzymes determined. In contrast, the application of elevated napropamide doses decreased the values of biochemical parameters of the soil in most cases. The Pearson’s correlation coefficients showed statistically significant negative correlation between the content of napropamide residues and the enzymatic activity of the soil.

16

Mechanics of seabed liquefaction and resolidification

75%

Sawicki A.

Archives of Mechanics

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2014

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tom Vol. 66, nr 5

307–-328

EN

The problem of pore water pressure changes in the seabed is considered. Two mechanisms of pore pressure changes are distinguished. The first is caused by external excitations, such as earthquakes, when pore pressure is gradually generated, leading to liquefaction. The second mechanism is caused by water waves, and it leads to cyclic changes in pore water pressure and the mean effective stress. Under certain conditions, when the effective stress path tends to exceed the failure condition, the regrouping of effective stresses takes place, as the soil should accommodate to new conditions. Then, the mechanism of resolidification of the seabed is described. It is concluded that after resolidification, the seabed is in a virgin state, as liquefaction erases the previous history of the seabed structure. A critical discussion of selected existing approaches to the problem of pore-pressure changes and the mechanism of liquefaction is presented in detail, in the form of extensive appendices. Some of these appendices deal with the crucial aspects of the mechanics of liquefaction such as, for example, the drained/undrained conditions.

17

Theory of space-time dissipative elasticity and scale effects

75%

Lurie S. A. , Belov P. A.

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2013

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tom 2

166-178

EN

In this article a model of irreversible dynamic thermoelasticity of an ideal continuua is constructed from an elasticity theory of asymmetrical, transversely isotropic in time direction, dissipative defectless 4D-continuum. In the model the fourth component of the 4D-displacement vector is locally irregular time R. The kinematic model comprises 3D-tensor of distortion, 3Dvector of velocity, 3D-gradient vector of local irregular time and entropy in unified tensor object which is an asymmetrical 4D-tensor of distortion of second rank. Consequently, the force model comprises 3D-tensor of stress, 3D-vector of impulses, 3D-vector of heat flow and temperature in unified tensor object which is an asymmetrical 4D-stress tensor of second rank. Hooke’s law equations have been formulated which connect components of asymmetrical 4D-tensors of stress and distortion. Physical interpretations have been given to the tensors’ components of thermomechanical properties of formulated continuum. Therefore, the article formulate an irreversible dynamic thermoelasticity covariant model of ideal (defectless) continua in which basic kinematic and force variables are components of unified tensor objects and theory is represented by 4D-vector equation. Sedov’s equation has been derived and resulted into Euler’s equations, space projections of which determine motion equations, and time projection determines heat conductivity equation as well as the whole spectrum of the space-time boundary value problems. The proposed theory allows one to describe the scale effects in the thermal processes and opens prospects for studying the scale effects of the coupled dynamic thermoelasticity and its nanoscience applications. A temperature-scale refinement can also broaden the range of applicability of the law of heat conduction in solids to allow for design of small-sized components, devices and nano-systems.

18

Dissipation of methomyl residues in tomato fruits, soil and water using LC-MS/MS

75%

El-Hefny D. , Abdallah I. , Helmy R. , Mahmoud H. , El-Hefny D. , Abdallah I. , Helmy R. , Mahmoud H.

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19

Analiza teoretyczna procesu kutrowania w aspekcie termodynamicznym

75%

Szeląg M.

Inżynieria Rolnicza

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2011

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tom R. 15, nr 4

257-264

PL

W pracy przedstawiono analizę teoretyczną procesu kutrowania i wynikające stąd efekty termodynamiczne. Wyróżniony układ roboczy, złożony z misy kutra wypełnionej farszem mięsnym i zespołu noży, rozpatrywany jest jako termodynamiczny układ otwarty, przyrównywany do układu tribologicznego. Dokonano podziału pracy tarcia i oporów tarcia na część cieplną i mechaniczną rozpatrywanego układu.

EN

The paper presents theoretical analysis of the process involving cutting meat by means of mechanical cutters and resultant thermodynamic effects. Separated working system, consisting of cutter pan filled with meat stuffing and a set of knives, is considered as a thermodynamic open system compared to a tribological system. The researchers divided friction work and frictional resistance into thermal and mechanical part of the discussed system.

20

Investigation of dispersive shock wave in two-phase injector

75%

Kwidziński R. , Trela M.

Archives of Thermodynamics

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2004

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tom Vol. 25, no. 3

27-45

EN

The paper concerns modelling of dissipation in a shock wave in one-component two-phase bubbly flow. Coefficient of macroscopic viscosity is proposed to describe energy dissipation in terms of homogeneous model. The value of macroscopic viscosity is calculated from entropy production in boundary layer around a bubble. Introduction of the macroscopic viscosity allowed for paper description of dispersive shock wave observed in supercritical steam injector.