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EN
The aim of the current paper is to investigate a small airplane model propeller of class F2D according to requirements of Fédération Aéronautique Internationale (FAI, or World Air Sports Federation). In some cases, practical tests show that F2D models with flexible propellers produce specific extra noise and increase flight speed in comparison with “rigid” propellers. Therefore, the following hypothesis could be proposed: flexible characteristics of the increased noise are related to the resonant eigenfrequencies of the propeller. The operating range of the F2D class propeller (28,000-35,000 rpm) is close to or equal to the eigenfrequency resonance. The current investigation addresses dynamic/flexible vibrations of elastic propeller during engine run and researches dynamic parameters of the propeller as well as the contribution of these parameters to the model flight characteristics. To resolve this type of a problem, a stand, which allows completing a physical investigation of flexible propeller vibration modes and dynamic characteristics was created.
PL
Celem artykułu jest przedstawienie wyników badań śmigła małego modelu samolotu zaliczanego do klasy F2D (według klasyfikacji Fédération Aéronautique Internationale, FAI). W niektórych przypadkach testy wykazały, że modele F2 z giętkimi śmigłami, w porównaniu do śmigieł sztywnych, wydają dodatkowy hałas i zwiększają prędkość samolotu. Dlatego wysunięto hipotezę, że elastyczne charakterystyki zwiększonego hałasu są powiązane z rezonansem częstotliwości własnych śmigła. Zakres pracy śmigła klasy F2D (28 000-35 000 obr/min) jest zbliżony do jego częstotliwości własnych. Badania dotyczą elastycznych wibracji dynamicznych śmigła giętkiego w czasie rozruchu silnika i są nakierowane na wyznaczanie parametrów dynamicznych i ich wpływu na charakterystyki lotu modelu. Wykonano i opisano stanowisko, na którym przeprowadzono testy modalne drgań giętkiego śmigła. Na tej podstawie uzyskano charakterystyki dynamiczne.
2
Content available remote Simulations of concrete response to impact loading using two regularized models
EN
This paper focuses on a comparison of two regularized continuum models for concrete in the simulations of selected benchmarks of response to impact loading. Their overview is performed in the context of application in dynamics. The first one is the Hoffman viscoplastic consistency model, where the strain rate activates regularization. The second model is derived from the scalar damage theory enhanced by an averaging equation incorporating the Laplacian of an averaged strain measure. Both models are implemented in the FEAP package. The results of some standard wave propagation tests are discussed, considering discretization sensitivity and predicted failure modes. Three examples are pre- sented: the direct tension of a plain and reinforced concrete bar, the split test of a cylinder, and the four-point bending of a reinforced concrete beam. The ability of both models to simulate impact loading is assessed.
3
Content available Przegląd i analiza elektrowni pływowych
PL
W przyszłości dla pozyskiwania energii opartego na zrównoważonym rozwoju istotną rolę może mieć energia pływów morskich. Energia ta jest rezultatem grawitacyjnego oddziaływania Ziemi, Księżyca i Słońca oraz sił odśrodkowych wytwarzanych przez układ Ziemia–Księżyc. Zapory pływowe do produkcji energii elektrycznej wykorzystują energię potencjalną fal. Przy użyciu turbin wodnych do generowania elektryczności można wykorzystać także energię kinetyczną prądów pływowych. Jednak wykorzystanie tego rodzaju technologii do produkcji energii elektrycznej na dużą skalę nie jest na razie ekonomicznie uzasadnione. Należy zauważyć, że rozwój tej technologii jest jeszcze na wczesnym etapie rozwoju. W niniejszym artykule omówiono wytwarzanie energii elektrycznej z pływów morskich przy zastosowaniu różnych technologii. Przeprowadzono wstępne badania symulacyjne przykładowego generatora pływowego oraz zapory pływowej z użyciem programów Computational Fluid Dynamics i SolidWorks. Przedstawiono także niektóre wyzwania związane z projektowaniem i budową systemów konwersji energii pływów morskich.
EN
For a sustainable future, tidal energy can play a vital role. Tidal energy relies on the gravitational pull of the Moon and the Sun along with the centrifugal forces created by the Earth. Tidal barrage uses the potential energy from the tide and has been very successful in electricity production. With the help of a turbine, kinetic energy can also be harnessed from tidal currents to generate electricity. However, it is not economically feasible to use this type of technology for large scale production of electrical energy. It is important to note that the development of this technology is still in the early stage. This research paper provides a preliminary discussion of tidal energy generation using a few different technologies. Initial research has been done using Computational Fluid Dynamics and SolidWorks software on the tidal stream generator and tidal barrage system. Some of the key challenges are also identified in terms of the development of the tidal energy conversion system.
5
Content available remote On a certain example of a motor vehicle braking in a turn simulation
EN
In this paper selected phenomena during vehicle curvilinear motion have been presented in different road conditions as an attempt to consider the certain attitude towards the aspects of traffic safety related to motor vehicles. As an attempt to analyze the vehicle response to the external disturbances in different road conditions and maneuvers this work is one of several ideas of analysis of motor vehicle dynamics. In general, research was based on simulations in the MSC Adams/Car software, version 2005r2. The following results may also serve e.g. as a basis of motor vehicle stability examination. The curvilinear motion of a vehicle seems important from the point of view of the maneuvers concerning the change in the direction of motion.
PL
W artykule przedstawiono wybrane zjawiska podczas ruchu krzywoliniowego pojazdu w różnych warunkach drogowych jako próbę podejścia do wybranych aspektów bezpieczeństwa ruchu drogowego związanych z pojazdami silnikowymi. Jako próba analizy reakcji pojazdu na zakłócenia zewnętrzne spowodowane głównie warunkami drogowymi i manewrami praca ta jest jedną z wielu koncepcji analizy dynamiki pojazdów silnikowych. Badania opierały się na symulacjach w oprogramowaniu MSC Adams/Car, wersja 2005r2. Poniższe wyniki mogą również służyć np. jako podstawa badania stateczności pojazdu silnikowego. Krzywoliniowy ruch pojazdu wydaje się ważny z punktu widzenia manewrów dotyczących zmiany kierunku ruchu.
6
Content available remote Modeling the inspection robot with magnetic pressure pad
EN
This article presents the process of designing a robot with a magnetic pressure pad for inspections of ferromagnetic ventilation ducts. In compliance with the assumptions, the CAD design of the robot was developed in a 3D programming environment. The designing proces brought about a mathematical model of the robot with one pair of magnetic drive modules, including simulation in a MATLAB/Simulink environment. The model accounted for parameters such as rolling resistance force, transverse resistance moment, magnetic attraction force, solid moment of inertia, and other factors. The magnetic pressure pad allowed for moving the robot in magnetic ventilation systems irrespective of slopes and shapes of ducts.
EN
Dynamic characteristics of the vibration screening machinery is influenced by synchronization between induction motors. Therefore, estimating the synchronous state between the motors is a crucial process for designing the vibration screening machinery. In this paper, two rotors excited with paralleled and counterrotating motors in a far resonance system are concerned. To master the synchronization of the system, the dynamic model is firstly established; then, the synchronous condition of the system is derived with the Poincar´e method; subsequently, the synchronous stability of the system is discussed by the Hamilton principle; finally, some computation simulations are implemented to verify correctness of theoretical analysis. The research result shows that the system actuated by rotors of the identical mass is planar motion as the stable phase difference between the rotors is stabilized in the zero phase. The system actuated by nonequivalent mass rotors exhibits spatial motion as the stable phase difference stabilizes in a nonzero phase.
EN
Harmful cyanobacterial efflorescence is of growing global concern and its prediction and management require a better understanding of the growth control factors and dominance of cyanobacteria. The Zit-Emba reservoir located in the North-East of Algeria, was constructed to provide drinking water, irrigation, and fishing. The vertical and seasonal distribution variation of cyanobacteria community associated with environmental factors was comprehensively investigated from April 2016 to December 2016 at five depths, based on a seasonal sampling. The cyanobacteria communities of this reservoir are composed of seven genera belonging to five orders. The average proportion of Microcystis to total cyanobacteria population was 43%, followed by Woronichinia 21%, Planktothrix 16%, Dolichospermum 13%, Oscillatoria 5%, and the remainder (Merismopedia, Spirulina) 2%. The average cyanobacterial abundance was 2702 cells/mL, ranging from 360 to 65 795 cells/mL and this abundance exceeds the alert level 1 throughout the year. The most recurrent periods of increase took place from spring to summer and autumn. However, the vertical distributions of cyanobacteria displayed a similar profile each season, and abundances tended to decrease with depth. The results of the statistical analysis suggested that the most abundant of cyanobacterial genera were positively related to chlorophyll-a and water temperature and negatively with the concentrations of NO3-N, NH4-N, and NO2-N. This demonstration of toxigenic cyanobacteria in this drinking water production dam involves regular monitoring of the cyanobacterial communities and cyanotoxins in raw water.
9
EN
The paper discusses mechanical properties of modern wheeled mobile robots including aspects of kinematics and dynamics. Relevant features of these robots and of used types of wheels are considered. Robots are categorized into six groups according to kinematic structures, which can be obtained using various types of wheels. For each group mechanical properties, which characterize the robots are discussed. Various variants of the robots within particular groups are described and some examples of existing solutions are given. Individual variants of the robots are compared and assessed taking into account the possessed features.
EN
The paper describes the dynamics of a composite cantilever beam with an active element. The vibrations of the kinematically excited beam are controlled with the use of a Macro Fiber Composite actuator. A proportional control algorithm is considered. During the analysis, actuator is powered by a time-varying voltage signal that is changed proportionally to the beam deflection. The MFC element control system with the implemented algorithm allowed for changing the stiffness of the tested structure. This is confirmed by the numerical and experimental results. Resonance curves for the beam with and without control are determined. The results show a very good agreement in qualitative terms.
EN
Equipment set for studying dynamics characteristics of vehicles as automatic control objects is presented. Dynamics characteristics of various mobile objects were studied at test site. Experimental procedure, electronic data processing using a method of adjustable equivalent model is provided. Research data and received mathematical models are provided.
PL
Przedstawiono sprzęt przeznaczony do badania dynamicznych cech pojazdów jako obiektów kontrolowanych automatycznie.
EN
The article describes the method for the multi-objective optimization of a proposed medical robot model, which has been considered in the form of a serial kinematic chain. In the assumed approach, the finite element method was used in order to model the flexibility of manipulator links. To speed up the optimization process, the response surface method was applied, defining the so-called metamodel. In order to uncover the optimal solution, a multi-objective genetic algorithm was used, guaranteeing the optimality of the manipulator model in the Pareto sense. The optimization process was carried out by analysing the selected case of the manipulator’s dynamics. The proposed optimization method allows us to minimize the mass of the manipulator while additionally ensuring the highest possible stiffness of its structure and sufficient strength of its parts. Furthermore, it offers the possibility to eliminate the natural frequency of vibrations of the model close to the resonant frequency.
EN
In tumbling mill drives, increased dynamic loads may occur in open gearing, which may cause an increase in the vibratory activity of the drive assembly and in dynamic loads in the mechanical drive system as a whole. Today, no adequate method is available for calculating the dynamic loads in the open gearing of tumbling mills. The article is devoted to the development of a method for dynamic load calculation, which takes into account the parameters of the drive system. The authors have proposed a mathematical model and a technique that allows for the identification of dynamic loads from experimental data and controlling the vibratory activity of the mechanical drive system of a tumbling mill at the design stage.
EN
A new method of designing tip-point trajectories for industrial manipulators with structural flexibility and friction in their supports and joints is presented in the paper. The method is based upon the formulation of the reference dynamics model of the manipulator model. The reference dynamics models are derived off-line for desired trajectories, i.e. trajectory patterns are delivered in constraint equation forms. A library of reference dynamics models can be generated off-line and serve for verification of desired motions feasibility, ability of reaching required velocities and accelerations in order to obtain the desired trajectories, and estimate power needed for desired motions execution. It enables off-line tests of a system model behavior when it moves a desired trajectory. Also, the reference dynamics enables verification of vibrations that may accompany desired motions, since at the stage of defining a desired trajectory, e.g. for performing a servicing task, a system behavior is unknown. The paper is dedicated to reference dynamics analysis, for a multi-link manipulator model, for which friction in joints is modeled by the LuGre model, the manipulator links are rigid but light and prone to vibrations. The results of the reference dynamics analysis are presented in a series of simulation studies.
EN
The objects of consideration are thin linearly elastic Kirchhoff-Love-type circular cylindrical shells having a periodically microheterogeneous structure in circumferential and axial directions (biperiodic shells). The aim of this contribution is to formulate and discuss a new averaged general asymptotic-tolerance model for the analysis of selected dynamic problems for the shells under consideration. This model is derived by applying the combined modelling which includes two techniques: the asymptotic modelling procedure and a certain extended version of the known tolerance non-asymptotic modelling technique based on a new notion of weakly slowly-varying function. Contrary to the starting exact shell equations with highly oscillating, non-continuous and periodic coefficients, governing equations of the averaged combined model have constant coefficients depending also on a cell size. The differences between the general combined model proposed here and the corresponding known standard combined model derived by means of the more restrictive concept of slowly-varying functions are discussed.
EN
The article presents the research carried out on the experimental construction of a crane, where a hoist with an AC motor without a motor control system was used as an excitation signal for the girder. The purpose of the described research is to determine the relationship between the values of the dynamic surplus factor when lifting the load with the loose rope in the initial phase of lifting and the distance of the hoist from the supporting structure. The data was obtained based on the force tests in a steel wire rope and subsequent determination of the values of stresses and deflections accompanying the selected test cases for different positions of the vibration inductor using the FE method.
17
Content available Assessment of comfort of use of footbridges
EN
To assess the comfort of use of the structures designed for human use during its vibrations it is necessary to know the requirement of the comfort criteria for the specific type of the structure. In the paper the issue of evaluation of the footbridges vibrations acceptability along with proposal of comfort criteria for the footbridges elaborated on the basis of survey researches were presented. The proposal of the vibration comfort criteria taking into account frequency of vibrations occurrence (frequent, rare and exceptional events) were characterized and compared with propositions of other authors, standards and recommendations.
EN
The paper contains a preliminary study of the transport market dynamics model, including its cyclical fluctuations. An additional goal is to enable a quantitative examination of the impact of transport congestion on the economic development and the effects of underinvestment in transport.
EN
The paper presents physical and mathematical model of the modified remote-controlled the artillery-missile system (AMS) system of the Wróbel II type that is intended to be located on a warship. The proposed system is used for independent detection, tracking and counteracting the means of air attack at short distances. Moreover, principle of operation of SAR is presented and analysis of the system’s dynamics was carried out. The results of investigations are given in a graphical form.
PL
W pracy przedstawiono model fizyczny i matematyczny zmodyfikowanego, zdalnie sterowanego systemu artyleryjsko-rakietowego (SAR) typu Wróbel II przeznaczonego do posadowienia na okręcie. Proponowany system przeznaczony jest do autonomicznego wykrywania, śledzenia oraz zwalczania środków napadu powietrznego na bliskich odległościach. Ponadto w artykule przedstawiono zasadę działania SAR oraz przeprowadzono analizę jego dynamiki. Wyniki badań przedstawiono w postaci graficznej.
EN
Urban shrinkage has been a remarkable phenomenon in city development, both domestic and foreign, which cannot be convincingly explained by growth theory. This paper studies the theoretical foundation and connotation of urban shrinkage, as well as its internal dynamic mechanism and external spatial mechanism. Thereby reaches the conclusion that both shrinkage and expansion is a natural historical process of the urban development. Compared to the urban shrinkage in highly industrialized countries which features generalizability and regularity, the case in China is quite different due to the under-development of urbanization and industrialization. Therefore we referred to the regularity, and further used internal dynamic mechanism and external spatial mechanism to identify and classify China’s shrinking cities, then discussed several patterns and drives, and finally proposed some policy suggestion and urban planning thoughts for sustainable development regarding various types of urban shrinkage.
PL
Kurczenie się miast jest niezwykłym zjawiskiem w historii rozwoju miast na całym świecie, którego nie da się przekonująco wytłumaczyć teorią wzrostu. Niniejszy artykuł analizuje teoretyczne podstawy i konotacje kurczenia się miast, a także mechanizmy ich wewnętrznej dynamiki i zewnętrznej przestrzeni. Na tej podstawie można postawić tezę, że zarówno kurczenie się, jak i rozszerzanie miast to naturalny proces historyczny rozwoju miast. Porównując kurczenie się miast w krajach silnie uprzemysłowionych, charakteryzujące się pewną regularnością, przypadek Chin jest odmienny, z uwagi na słabszy poziom urbanizacji i uprzemysłowienia. Dlatego też odnieśliśmy się do regularności i następnie zastosowaliśmy mechanizmy wewnętrznej dynamiki i zewnętrznej przestrzeni. W ten sposób zidentyfikowaliśmy i sklasyfikowaliśmy chińskie kurczące się miasta, aby następnie poddać dyskusji kilka wzorców. Przeprowadzona dyskusja pozwala na zaproponowanie sugestii politycznych i wskazówek dla urbanistyki w kontekście rozwoju zrównoważonego, uwzględniając różne typy kurczących się miast.
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