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Number of results: 147
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Abstract

The motion planning problem consists in finding a control function which drives the system to a desired point. The motion planning algorithm derived with an endogenous configuration space approach assumes that the motion takes place in an arbitrary chosen time horizon. This work introduces a modification to the motion planning algorithm which allows to reach the destination point in time, which is shorter than the assumed time horizon. The algorithm derivation relies on the endogenous configuration space approach and the continuation (homotopy) method. To achieve the earlier destination reaching a new formulation of the task map and the task Jacobian are introduced. The efficiency of the new algorithm is depicted with simulation results.
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Abstract

The paper presents a simple, systematic and novel graphical method which uses computer graphics for prediction of limit cycles in two dimensional multivariable nonlinear system having rectangular hysteresis and backlash type nonlinearities. It also explores the avoidance of such self-sustained oscillations by determining the stability boundary of the system. The stability boundary is obtained using simple Routh Hurwitz criterion and the incremental input describing function, developed from harmonic balance concept. This may be useful in interconnected power system which utilizes governor control. If the avoidance of limit cycle or a safer operating zone is not possible, the quenching of such oscillations may be done by using the signal stabilization technique which is also described. The synchronization boundary is laid down in the forcing signal amplitudes plane using digital simulation. Results of digital simulations illustrate accuracy of the method for 2×2 systems.
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Abstract

The minimum energy control problem for the positive descriptor discrete-time linear systems with bounded inputs by the use of Weierstrass-Kronecker decomposition is formulated and solved. Necessary and sufficient conditions for the positivity and reachability of descriptor discrete-time linear systems are given. Conditions for the existence of solution and procedure for computation of optimal input and the minimal value of the performance index is proposed and illustrated by a numerical example.
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Abstract

In this article, an engineering/physical dynamic system including losses is analyzed inrelation to the stability from an engineer’s/physicist’s point of view. Firstly, conditions for a Hamiltonian to be an energy function, time independent or not, is explained herein. To analyze stability of engineering system, Lyapunov-like energy function, called residual energy function is used. The residual function may contain, apart from external energies, negative losses as well. This function includes the sum of potential and kinetic energies, which are special forms and ready-made (weak) Lyapunov functions, and loss of energies (positive and/or negative) of a system described in different forms using tensorial variables. As the Lypunov function, residual energy function is defined as Hamiltonian energy function plus loss of energies and then associated weak and strong stability are proved through the first time-derivative of residual energy function. It is demonstrated how the stability analysis can be performed using the residual energy functions in different formulations and in generalized motion space when available. This novel approach is applied to RLC circuit, AC equivalent circuit of Gunn diode oscillator for autonomous, and a coupled (electromechanical) example for nonautonomous case. In the nonautonomous case, the stability criteria can not be proven for one type of formulation, however, it can be proven in the other type formulation.
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Abstract

A novel 4-D chaotic hyperjerk system with four quadratic nonlinearities is presented in this work. It is interesting that the hyperjerk system has no equilibrium. A chaotic attractor is said to be a hidden attractor when its basin of attraction has no intersection with small neighborhoods of equilibrium points of the system. Thus, our new non-equilibrium hyperjerk system possesses a hidden attractor. Chaos in the system has been observed in phase portraits and verified by positive Lyapunov exponents. Adaptive backstepping controller is designed for the global chaos control of the non-equilibrium hyperjerk system with a hidden attractor. An electronic circuit for realizing the non-equilibrium hyperjerk system is also introduced, which validates the theoretical chaotic model of the hyperjerk system with a hidden chaotic attractor.
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Abstract

This article presents a hybrid control system for a group of mobile robots. The components of this system are the supervisory controller(s), employing a discrete, event-driven model of concurrent robot processes, and robot motion controllers, employing a continuous time model with event-switched modes. The missions of the robots are specified by a sequence of to-be visited points, and the developed methodology ensures in a formal way their correct accomplishment.
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Abstract

The purpose of this paper is to depict the effect of diffusion and internal heat source on a two-temperature magneto-thermoelastic medium. The effect of magnetic field on two-temperature thermoelastic medium within the three-phase-lag model and Green-Naghdi theory without energy dissipation i discussed. The analytical method used to obtain the formula of the physical quantities is the normal mode analysis. Numerical results for the field quantities given in the physical domain are illustrated on the graphs. Comparisons are made with results of the two models with and without diffusion as well as the internal heat source and in the absence and presence of a magnetic field.
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Abstract

The work deals with the heat analysis of generalized Burgers nanofluid over a stretching sheet. The Rosseland approximation is used to model the non-linear thermal radiation and incorporated non-uniform heat source/sink effect. The governing equations reduced to a set of nonlinear ordinary differential equations under considering the suitable similarity transformations. The obtained ordinary differential equations equations are solved numerically by Runge-Kutta-Fehlberg order method. The effect of important parameters on velocity, temperature and concentration distributions are analyzed and discussed through the graphs. It reveals that temperature increases with the increase of radiation and heat source/sink parameter.
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Abstract

In this study a cooling ejector cycle coupled to a compression heat pump is analyzed for simultaneous cooling and heating applications. In this work, the influence of the thermodynamic parameters and fluid nature on the performances of the hybrid system is studied. The results obtained show that this system presents interesting performances. The comparison of the system performances with hydrofluorocarbons (HFC) and natural fluids is made. The theoretical results show that the a low temperature refrigerant R32 gives the best performance.
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Abstract

The present work focuses on analyses of the autoignition delay time predicted by the large eddy simulation (LES) method by applying different subgrid scales (SGS) models and two different discretization schemes. The analysed flow configuration is a two-phase chemically reacting turbulent flow with monodispersed evaporating fuel droplets. The impact of numerical procedure is investigated in a 3D flow domain with a temporally evolving mixing layer that constituted between the streams of fuel and oxidizer that moved in opposite directions. The upper stream of cold gas carries a dispersed fuel spray (ethanol at 300 K). The lower stream is a hot air at 1000 K. Three commonly used in LES, SGS models are investigated, namely: classical Smagorinsky model, model proposed by Vreman and the #27;-model proposed by Nicoud. Additionally, the impact of two discretization schemes, i.e., total variation diminishing (TVD) and weighted essentially nonoscillatory (WENO) is analysed. The analysis shows that SGS model and discretization scheme can play a crucial role in the predictions of the autoignition time. It is observed that for TVD scheme the impact of SGS model is rather small. On the contrary, when the WENO scheme is applied the results are much more dependent on the SGS model.
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Abstract

The paper presents the results of the design analysis and experimental investigations of the microturbine set consisting of the microturbine with partial admission and permanent magnet generator. The microturbine was designed for operation with the vapour of ethanol as a working fluid. Microturbine unit was tested for different parameters of the working fluid and varying the electrical load. The examples and the comparison between experiment results and numerical simulations are shown and discussed in the paper.
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Abstract

The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 μm, 571 μm, 750 μm, and 823 μm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.
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Abstract

The designing of transmultiplexer systems relies on determining filters for the transmitter and receiver sides of multicarrier communication system. The perfect reconstruction conditions lead to the bilinear equations for FIR filter coefficients. Generally there is no way of finding all possible solutions. This paper describes methods of finding a large family of solutions. Particular attention is devoted to obtaining algorithms useful in fixed-point arithmetic needed to design the integer filters. As a result, the systems perform perfect reconstruction of signals. Additionally, a simple method is presented to transform any transmultiplexer into an unlimited number of different transmultiplexers. Finally, two examples of integer filters that meet perfect reconstruction conditions are shown. The first illustrates a FIR filter which does not require multiplications. The frequency properties of filters and signals are discussed for the second example.
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Abstract

The long-ranging Early to Middle Triassic coniform conodont form-genus Cornudina Hirschmann occurs abundantly in the Anisian of NW Turkey, Northern Tethys. Although suggested to represent the P1 element of an apparatus of the Order Ozarkodinida Dzik, questions concerning the apparatus of Cornudina remain. A description of the probable phylogenetic trends in the P1 elements of Cornudina is attempted and the role of the form-genera Ketinella Gedik and Kamuellerella Gedik, as the alternative ramiform skeletal elements in the Cornudina multi-element apparatus, is investigated. The newly described, Gedikella quadrata gen. nov., sp. nov., is an S element, Kamuellerella rectangularis sp. nov., is either an S3 or an S4 element, and Ketinella goermueshi sp. nov., is an M element.
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Abstract

The Upper Greensand Formation, mostly capped by the Chalk, crops out on the edges of a broad, dissected plateau in Devon, west Dorset and south Somerset and has an almost continuous outcrop that runs from the Isle of Purbeck to the Vale of Wardour in south Wiltshire. The Formation is well exposed in cliffs in east Devon and the Isle of Purbeck, but is poorly exposed inland. It comprises sandstones and calcarenites with laterally and stratigraphically variable amounts of carbonate cement, glauconite and chert. The sedimentology and palaeon- tology indicate deposition in marginal marine-shelf environments that were at times subject to strong tidal and wave-generated currents. The formation of the Upper Greensand successions in the region was influenced by penecontemporaneous movements on major fault zones, some of which are sited over E-W trending Variscan thrusts in the basement rocks and, locally, on minor faults. Comparison of the principal sedimentary breaks in the succession with the sequence boundaries derived from world-wide sea-level curves suggests that local tec- tonic events mask the effects of any eustatic changes in sea level. The preserved fauna is unevenly distributed, both laterally and stratigraphically. Bivalves, gastropods and echinoids are common at some horizons but are not age-diagnostic. Ammonites are common at a few stratigraphically narrowly defined horizons, but are rare or absent throughout most of the succession. As a result, the age of parts of the succession is still poorly known
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Abstract

The Maastrichtian sediments of northern Iraq are rich in larger benthic foraminifera. Among them, the genus Loftusia is well-known one because of its significant palaeogeographic distribution across the Mediterranean and Middle East. In this study, observations of abnormal test shapes, species recognition criteria and endoskeleton characteristics of Loftusia are discussed, based on the new material from north-eastern Iraq. The following species of Loftusia are described: Loftusia elongata Cox, L. persica Brady, Loftusia morgani Douvillé, L. anatolica Meriç, L. matsumarui Meriç and Görmüs, L. minor B Cox, L. ketini B Meriç and L. kahtaensis Meriç, Loftusia minor A Cox, L. oktayi Meriç and L. baykali Meriç. The predominant species are Loftusia elongata, L. morgani and L. baykali. Skewed abnormal individuals and epidermal parts of the endoskeleton structure are also interesting aspects to note. Quantitative data obtained for Loftusia allow us to better understand and interpret species identification criteria, abnormal occurrences and the endoskeleton structure.
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Abstract

In the Polish sector of the Magura Nappe have long been known and exploited carbonate mineral waters, saturated with carbon dioxide, known as the “shchava (szczawa)”. These waters occur mainly in the Krynica Subunit of the Magura Nappe, between the Dunajec and Poprad rivers, close to the Pieniny Klippen Belt (PKB). The origin of these waters is still not clear, this applies to both “volcanic” and “metamorphic” hypotheses. Bearing in mind the case found in the Szczawa tectonic window and our geological and geochemical studies we suggest that the origin of the carbon dioxide may be linked with the thermal/pressure alteration of organic matter of the Oligocene deposits from the Grybów Unit. These deposits, exposed in several tectonic windows of the Magura Nappe, are characterized by the presence of highly matured organic matter – the origin of the hydrocarbon accumulations. This is supported by the present-day state of organic geochemistry studies of the Carpathian oil and gas bed rocks. In our opinion origin of the carbon-dioxide was related to the southern, deep buried periphery of the Carpathian Oil and Gas Province. The present day distribution of the carbonated mineral water springs has been related to the post-orogenic uplift and erosion of the Outer (flysch) Carpathians.
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Abstract

The Telbesmi Formation, at the northern margin of the Arabian Plate, Turkey, is composed of alternating darkbrown, pinky-brown fluvial arkosic sandstone/mudstones with thin-bedded cherty limestones and channel conglomerates. The formation contains rare and poorly diversified trace fossils. The siltstone/sandstone beds of levels 1 and 2 of the formation yielded, however, a moderately diverse assemblage composed of: Cochlichnus isp., Palaeophycus isp., Planolites beverleyensis, Teichichnus isp. and ?Treptichnus rectangularis. This assemblage, made up of traces left by deposit feeding organisms, represents the Scoyenia ichnofacies. Treptichnus rectangularis and Palaeophycus isp., of the assemblage, can be considered markers for the base of the Cambrian in southeast Turkey.
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Abstract

Early Palaeocene through early Eocene silicoflagellate assemblages were examined from five southern subtropical through subpolar deep-sea sites: DSDP Holes 208 and 524, and ODP Holes 700B, 752A, and 1121B. For each site, the taxonomic composition of the silicoflagellate assemblage is documented in detail; Pseudonaviculopsis gen. nov., Dictyocha castellum sp. nov. and Stephanocha? fulbrightii sp. nov. are proposed, along with several new combinations. More importantly, however, these observations enable a considerable refinement to the existing Palaeocene–Eocene silicoflagellate biostratigraphic zonation that for the first time uses datums calibrated to the Geomagnetic Polarity Timescale. The Corbisema aspera Interval Zone occurs immediately above the K/Pg boundary and is here described from Seymour Island. The Corbisema hastata Partial Range Zone extends from near the K/Pg boundary to late early Palaeocene and has been observed in Hole 208. The Pseudonaviculopsis disymmetrica Acme Zone occurs in Holes 208 and 700B. The Dictyocha precarentis Partial Range Zone, observed in Holes 208, 700B, 752A and 1121B, is subdivided into D. precarentis, Naviculopsis primativa, N. cruciata and Pseudonaviculopsis constricta subzones. The Naviculopsis constricta Partial Range Zone occurs in Holes 524, 700B, 752A and 1121B. This study is also the first to consider syn- and/or diachroneity in Palaeogene silicoflagellate biostratigraphy.
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Abstract

The Nencki Institute of Experimental Biology of the Polish Academy of Sciences in Warsaw, one of the largest nonacademic biological research centres in Poland, celebrates its 100th anniversary. The Institute was established in 1918 by the Scientific Society of Warsaw. In 1945, after World War II, it was re-established in Łódź and in 1952 incorporated into the newly founded Polish Academy of Sciences. During the period of 1953–1955 a newly erected building at 3 Pasteur Street in Warsaw became the home of the Nencki Institute. Today, the Nencki Institute strives for excellence in basic research in the broad sense of biological sciences. Neurosciences and biological and molecular basic of civilization diseases represent two main research areas of the Institute in the context of the society needs to improve the quality of life. One of the strategic activities of the Institute is investments in bio- imaging.This has recently resulted in inclusion of the Institute in the EUROBIOIMAGING project of the European Strategy Forum on Research Infrastructures (ESFRI). An excellent example of a synergy of basic and innovative studies is the Neurobiology Centre established at the Nencki Institute in 2010–2013 as part of a strategic project entitled the CePT. Additionally, the Nencki Institute trains nearly 200 PhD students under various programmes, including the H2020.
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Abstract

This review compiles the pioneers of biological sciences who have been born and educated on the territories, which has got political independence as Poland state in 1918. Their work and passing knowledge to the next generations had a great impact not only on the progress in science but also on a newly formed Polish society. Many of these contributions laid foundations for chemistry, physics, biochemistry, genetics and other biological sciences.
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Abstract

The article is a modified Polish version of my Director’s report published in the “Annual Report 2017–March 2018” of the International Institute of Molecular and Cell Biology in Warsaw (www.iimcb.gov.pl). After 20 years of being in charge of the Institute and a few months before the end of my final term as its director, I summarize our achievements, failures, lost opportunities and recall how it all began. I also give the names of people who formed organizing team of the Institute in the nineties, names of the first International Advisory Board members and names of the Institutes’ directors who will be in charge of it since July 2018.
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Abstract

Professor Piotr Pierański, an outstanding Polish physicists, excellent researcher and brilliant lecturer, passed away on the 23rd February 2018. The article quotes some recollections of his numerous friends and coworkers wordwide.
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