PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 12

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  fala
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available remote Laboratory study of the effects of terrestrial coastal forests on the absorption of solitary wave force
Mirzakhani Golnaz, Ghanbari-Adivi Elham, Fattahi Rohollah
Acta Geophysica
|
2024
|
Vol. 72, no. 1
449--465
EN
One of the beach protection techniques is using natural methods based on the coastal ecosystem. Studies show the reducing effect of forest covers on wave destruction intensity in different areas. However, it is not yet well understood how various densities of terrestrial coastal forest (TCF) affect the wave attenuation and reduce their strength. Studying the impact of various forest parameters, such as density, distance, and arrangement type on the wave force attenuation, this research measures the wave forces directly. TCF model was installed in a knife edge flume, which equipped with a load cell and an acoustic Doppler velocimeter. The experiments were performed in two staggered and parallel arrangements consisting of different densities from 12 to 273 stems per unit area. Based on obtained results, TCF had significant effects on the wave force absorption. An increase in the number of trees (density) increased TCF resistance force and the absorbed wave force. In its best, the TCF could absorb the wave force 3.76 times more than the no-TCF case. It could reduce the wave height by up to 81% at the highest density and maximum wave height. The absorbed wave force and drag coefficient rose as the number of rows of trees opposing the flow decreased and the intervals between trees were shortened. Increasing tree density from 12 to 273 stems per unit area increased the drag coefficient by the average of 61.82% for parallel and staggered arrangements, which means an average increase of 9.7% for each TCF row.
2
Content available Plane waves in thermo-viscoelastic material with voids under different theories of thermoelasticity
Tomar S. K., Goyal N., Szekeres A.
International Journal of Applied Mechanics and Engineering
|
2019
|
Vol. 24, no. 3
691--708
EN
Propagation of time harmonic plane waves in an infinite thermo-viscoelastic material with voids has been investigated within the context of different theories of thermoelasticity. The equations of motion developed by Iesan [1] have been extended to incorporate the Lord-Shulman theory (LST) and Green-Lindsay theory (GLT) of thermoelasticity. It has been shown that there exist three coupled dilatational waves and an uncoupled shear wave propagating with distinct speeds. The presence of thermal, viscosity and voids parameters is responsible for the coupling among dilatational waves. All the existing waves are found to be dispersive and attenuated in nature. The phase speeds and attenuation coefficients of propagating waves are computed numerically for a copper material and compared under different theories of thermo-elasticity. The expressions of energies carried along each wave have also been derived. All the computed numerical results have been depicted through graphs. It is found that the influence of CT and GLT is almost same on wave propagation, while LST influences the wave propagation differently.
3
Content available remote On scaling of ship seakeeping
Artyszuk J.
Prace Naukowe Politechniki Warszawskiej. Transport
|
2016
|
z. 112
9--24
EN
The widely accepted linear model of ship motions in waves is considered in frequencydomain, where the steady-state harmonic motions as response to harmonic waves are of interest. The solution of motion transfer functions is presented in dimensionless form with special concern about the dimensionless wave frequency as independent variable. Though some facts are known within ship model testing methodology, this detailed and careful derivation is aimed to enhance in-depth understanding of the seakeeping characteristics of a ship. It is also expected that a transfer functions data exchange between one full-scale ship and another of close geometry yet of different size will be more encouraged.
PL
Na bazie liniowego modelu dynamiki wyprowadzono funkcje przenoszenia sprzężonych kołysań statku na fali harmonicznej. Szczególny nacisk położono na pełne ujęcie bezwymiarowe, z istotną rolą bezwymiarowej częstości fali. Mimo że ta ostatnia jest szeroko stosowana w okrętowych badaniach modelowych, to jest stosunkowo rzadko wykorzystywana w przeliczaniu funkcji przenoszenia między statkami rzeczywistymi o różnych wielkościach, gdy takie charakterystyki są znane. Ma to znaczenie np. w szybkim modelowaniu większej klasy statków i oceny ryzyka eksploatacji, m.in. w systemach nadzoru ruchu. Zarówno sam sposób niniejszego wywodu, jak i dyskusja poszczególnych założeń i kroków ma stanowić przyczynek do lepszego rozumienia analizy bezwymiarowej ('bezwymiarowania') w odniesieniu do kołysań statku, i tym samym służyć zwiększeniu świadomości użytkowników narzędzi analitycznych i decydentów.
4
Content available The effect of an underwater explosion on a ship
Szturomski B.
Zeszyty Naukowe Akademii Marynarki Wojennej
|
2015
|
R. 56 nr 2 (201)
57--73
EN
This article contains a synthetic account of an underwater explosion and its effects. It presents diagrams of the gas bubble radius in the function of explosive charge mass and detonation depth as well the values of pressure on the front of a shock wave in the function of range and mass of TNT charge: 1, 10, 50, 250, 1000 kg (following T. L. Geers and K. S. Hunter). It also presents a classification of underwater explosions and their effect on a ship’s hull. It includes the classification of modern sea mines throughout the world and also contains a diagram which can be used to estimate the effects of a shockwave on a ship’s hull in the function of TNT charge mass, following the Cole’s formulas.
PL
W artykule zamieszczono syntetyczny opis wybuchu podwodnego i jego skutki. Przedstawiono wykresy promienia pęcherza gazowego w funkcji masy ładunku i głębokości detonacji oraz wartości ciśnienia na froncie fali uderzeniowej w funkcji odległości i masy ładunku TNT wynoszącej 1, 10, 50, 250, 1000 kg (według T. L. Geersa i K. S. Huntera). Przedstawiono klasyfikację wybuchów podwodnych i ich oddziaływanie na kadłub okrętu. Przedstawiono klasyfikację współczesnych min morskich świata. Opracowano wykres umożliwiający szacowanie skutków oddziaływania fali uderzeniowej na kadłub okrętu w funkcji masy ładunku TNT według wzorów Cole’a.
5
Content available Zmiany ramienia prostującego w zjawisku czystej utraty stateczności statku na fali
Chorab P.
TTS Technika Transportu Szynowego
|
2015
|
R. 22, nr 12
290--296, CD
PL
W artykule przedstawione zostało zjawisko czystej utraty stateczności statku na fali. Zaprezentowano wyniki obliczeń wynikające z modelu defektu statecznościowego utraty stateczności statku na fali dla kryteriów oceny stateczności drugiej generacji. Przeanalizowano zmiany ramienia prostującego statku na fali dla różnych położeń grzbietu fali względem kadłuba statku i wybranych stanów załadowania statku. Wyniki obliczeń wykonanych oprogramowaniem Maxsurf/Hydromax zaprezentowano na załączonych wykresach.
EN
The paper presents phenomenon of pure loss of stability of the ship on a wave. The results of the calculations were presented from the model of stability defect pure loss of the ship's stability on the wave for assessing the stability by the criteria second generation. Analyzed ware variations of righting arms the ship on a wave, for wave crest in different positions relative to the hull of the ship and selected loading conditions of the ship. The results of calculations carried out by software Maxsurf/Hydromax were presented in the at-tached charts.
6
Content available remote Dynamical system analysis of unstable flow phenomena in centrifugal blower
Garcia D., Stickland M., Liśkiewicz G.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
2014
|
nr 145
43--46
EN
Methods of dynamical system analysis were employed to analyze unsteady phenomena in the centrifugal blower. Pressure signals gathered at different control points were decomposed into their Principal Components (PCs) by means of Singular Spectrum Analysis (SSA). Certain number of PCs was considered in the analysis based on their statistical correlation. Projection of the original signal onto its PCs allowed to draw the phase trajectory that clearly separated non-stable blower working conditions from its regular operation.
7
Ultrasonic Mixer For Fullerene Solution In Transformer Oils
Kalus P.
Zeszyty Naukowe. Elektryka / Politechnika Opolska
|
2009
|
z. 62
25-26
EN
In the paper, the design of an ultrasonic mixer is presented. The device is used for mixing fullerenes in transformer oil using ultrasonic waves. The main part is a microprocessor-controlled oscillator that uses direct digital synthesis providing ultra-precise frequency control in wide bandwidth.
8
Physical and numerical aspects of dispersion phenomenon in solids under impact loading
Glema A.
Foundations of Civil and Environmental Engineering
|
2006
|
No. 7
127-146
EN
Dispersion as the material property is discussed in the paper. The definition, origination and dispersion analysis are presented. The dispersive and non-dispersive constitutive models are studied. The mechanical problem of inelastic deformation of solids is considered. The evolution of viscoplastic flow describes material hardening and softening with formation of strain localization zone. Wave character and dispersion are recognized as fundamental elements in formulation and solution in dynamic, rate dependent processes with strain localization and shear band propagation. The physical and numerical aspects of dispersion clarify the development of deformation, stress or energy distribution and verify the solution procedure. The paper exposes the importance of dispersion phenomenon that should be carefully investigated in class of solid mechanics problems. The numerical results confirm the role of dispersion effects.
9
Numerical modeling of wave propagation and interaction in bars
Jankowiak T., Klepaczko J., Łodygowski T.
Foundations of Civil and Environmental Engineering
|
2006
|
No. 7
187-199
EN
In the first part, the paper presents analytical solution of symmetric longitudinal impact of a semi-infinite circular bar. In the second part the Maple code is used in order to solve the differential equations, derived and solved by Skalak [1]. Based on this analytical solution, a verification is performed by Finite Element code. The calibration of parameters like the artificial viscosity and the mesh size is done. The initial FE calibration is used, together with cumulative fracture criterion, to verify the laboratory test results presented by Klepaczko [2,3,4,7]. The finite element solution is focused on the new experimental technique to test semi-brittle materials in dynamic tension via spalling. The technique which is based on Hopkinson pressure bar has been developed in LPMM-Metz [4].
10
Content available remote Dźwięki i fale [rec.]
Linde B.
Postępy Fizyki
|
2005
|
T. 56, z. 6
278-279
PL
Recenzja książki: Rufin Makarewicz - Dźwięki i fale, Wydawnictwo Naukowe UAM, Poznań 2004, s. 268.
11
Content available Możliwość stochastycznej niestabilności drgań narzędzi rolniczych w glebie
Chigarev A., Chigarev Y., Nowowiejski R.
Inżynieria Rolnicza
|
2005
|
R. 9, nr 3
103--110
PL
Badano zmiany właściwości agrotechnicznych gleby wynikające z obciążenia siłami dynamicznymi od maszyn i narzędzi rolniczych. Jako model mechaniczny rozważany jest uogólniony model ośrodka lepko-sprężystego. Dane doświadczalne były podstawą wyboru tego modelu. Stwierdzono, że zarówno porowatość gleby jak i przepuszczalność powietrzna pogarszały się, gdy gleba była obciążana dynamicznie. Gęstość gleby wzrastała w porównaniu z obciążeniem statycznym. Omawiana jest stabilność fali w glebie. Stabilność aproksymacji liniowej jest zapewniona przez warunek prędkości minimalnej wzdłuż osi.
EN
The changes of agro-technical properties of soil resulting from dynamic forces exerted by agricultural implements and machines were studied. A generalised model of viscous-elastic medium was taken as a mechanical model. Experimental data were the basis for the choice of this model. It was found that both soil porosity and its air permeability worsened when the soil was under dynamic load. As for soil density, it increased compared with static load. The stability of wave propagation in soil was discussed. Stability of the linear approximation is guaranteed by the condition of minimum velocity along the axis.
12
Występowanie zjawiska przemocy i innych dysfunkcji osobowych wśród żołnierzy zasadniczej służby wojskowej
Znojek B.
Zeszyty Naukowe / Wyższa Szkoła Oficerska Sił Powietrznych
|
2002
|
Nr 1
110--122
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.