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  • The central theme of this work was to analyze high aspect ratio structure having structural nonlinearity in low subsonic flow and to model nonlinear stiffness by finite element-modal approach. Total stiffness of high aspect ratio wing can be decomposed to linear and nonlinear stiffnesses. Linear stiffness is modeled by its eigenvalues and eigenvectors, while nonlinear stiffness is calculated by the method of combined Finite Element-Modal approach. The nonlinear modal stiffness is calculated by defining nonlinear static load cases first. The nonlinear stiffness in the present work is modeled in two ways, i.e., based on bending modes only and based on bending and torsion modes both. Doublet lattice method (DLM) is used for dynamic analysis which accounts for the dependency of aerodynamic forces and moments on the frequency content of dynamic motion. Minimum state rational fraction approximation (RFA) of the aerodynamic influence coefficient (AIC) matrix is used to formulate full aeroelastic state-space time domain equation. Time domain dynamics analyses show that structure behavior becomes exponentially growing at speed above the flutter speed when linear stiffness is considered, however, Limit Cycle Oscillations (LCO) is observed when linear stiffness along with nonlinear stiffness, modeled by FE-Modal approach is considered. The amplitude of LCO increases with the increase in the speed. This method is based on cantilevered configuration. Nonlinear static tests are generated while wing root chord is fixed in all degrees of freedom and it needs modification if one requires considering full aircraft. It uses dedicated commercial finite element package in conjunction with commercial aeroelastic package making the method very attractive for quick nonlinear aeroelastic analysis. It is the extension of M.Y. Harmin and J.E. Cooper method in which they used the same equations of motion and modeled geometrical nonlinearity in bending modes only. In the current work, geometrical nonlinearities in bending and in torsion modes have been considered.
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  • International Journal of Electronics and Telecommunications (IJET, eISSN 2300-1933, untill 2013 also print ISSN 2081-8491) is a periodical of Electronics and Telecommunications Committee of Polish Academy of Sciences and it is published by Warsaw Science Publishers of PAS. It continues tradition of the Electronics and Telecommunications Quarterly (ISSN 0867-6747) established in 1955 as the Rozprawy Elektrotechniczne. The IJET is a scientific periodical where papers present the results of original, theoretical, experimental and reviewed works. They consider widely recognized aspects of modern electronics, telecommunications, microelectronics, optoelectronics, radioelectronics and medical electronics. The authors are outstanding scientists, well‐known experienced specialists as well as young researchers – mainly candidates for a doctor's degree. The papers present original approaches to problems, interesting research results, critical estimation of theories and methods, discuss current state or progress in a given branch of technology and describe development prospects. All the papers published in IJET are reviewed by international specialists who ensure that the publications are recognized as author's scientific output. The printed periodical is distributed among all those who deal with electronics and telecommunications in national scientific centers as well as in numeral foreign institutions, and it is subscribed by many specialists and libraries. Its electronic version is available at http://ijet.pl. The papers received are published within half a year if the cooperation between author and the editorial staff is efficient. The papers may be submitted to the editorial office by the journal web page http://ijet.pl.,This paper presents active inductor based VCO design for wireless applications based on analysis of active inductor models (Weng-Kuo Cascode active inductor & Liang Regular Cascode active inductor) with feedback resistor technique. Embedment of feedback resistor results in the increment of inductance as well as the quality factor whereas the values are 125.6@2.4GHz (Liang) and 98.7@3.4GHz (Weng-Kuo). The Weng-Kuo active inductor based VCO shows a tuning frequency of 1.765GHz ~2.430GHz (31.7%), while consuming a power of 2.60 mW and phase noise of -84.15 dBc/Hz@1MHz offset. On the other hand, Liang active inductor based VCO shows a frequency range of 1.897GHz ~2.522GHz (28.28%), while consuming a power of 1.40 mW and phase noise of -80.79 dBc/Hz@1MHz offset. Comparing Figure-of-Merit (FoM), power consumption, output power and stability in performance, designed active inductor based VCOs outperform with the stateof- the-art.,
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  • Archives of Acoustics is an English-language peer-reviewed quarterly journal publishing original research papers from all areas of acoustics and abstracts from some specialised acoustical conferences. It gives free internet access to its full content (abstracts of research papers) to current issues. Archives of Acoustics, the peer-reviewed quarterly journal publishes original research papers from all areas of acoustics like: acoustical measurements and instrumentation, acoustics of musics, acousto-optics, architectural, building and environmental acoustics, bioacoustics, electroacoustics, linear and nonlinear acoustics, noise and vibration, physical and chemical effects of sound, physiological acoustics, psychoacoustics, quantum acoustics, speech processing and communication systems, speech production and perception, transducers, ultrasonics, underwater acoustics. Earlier issues are available on the old website http://acoustics.ippt.gov.pl/index.php/aa/issue/archive,The article describes the method of controlling the recovered grade based on measuring the intensity of volume ultrasonic oscillations and Lamb waves covering a fixed distance through the test medium and on a metal plate contacting the test medium at various time points of deliberate motion of ground materials. The authors suggest a method of determining density of ground ore particles in the pulp periodically after isolating the pulp flow in the vertical part of the measuring vessel based on measuring attenuation change values in Lamb waves covering a fixed distance on a plate contacting the medium under study and high frequency volume ultrasonic oscillations that have come through it within a certain time period. There are given dependencies of amplitudes of measuring channels based on volume ultrasonic oscillations and surface Lamb waves, size distribution according to solid phase pulp particles for various types of ores under study, a set of curves for determining the recovered grade with regard to various types of ores under study.,
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  • Two fundamental challenges in investigation of nonlinear behavior of cantilever beam are the reliability of developed theory in facing with the reality and selecting the proper assumptions for solving the theory-provided equation. In this study, one of the most applicable theory and assumption for analyzing the nonlinear behavior of the cantilever beam is examined analytically and experimentally. The theory is concerned with the slender inextensible cantilever beam with large deformation nonlinearity, and the assumption is using the first-mode discretization in dealing with the partial differential equation provided by the theory. In the analytical study, firstly the equation of motion is derived based on the theory of large deformable inextensible beam. Then, the partial differential equation of motion is discretized using the Galerkin method via the assumption of the first mode. An exact solution to the obtained nonlinear ordinary differential equation is developed, because the available semi analytical and approximated methods, due to their limitations, are not always sufficiently reliable. Finally, an experiment set-up is developed to measure the nonlinear frequency of oscillations of an aluminum beam within a domain of initial displacement. The results show that the proposed analytical method has excellent convergence with experimental data.
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  • The Geodesy and Cartography is a semi-annually scientific journal publishing peer-reviewed articles with original solutions of theoretical, experimental or applicable problems in the field of geodesy, surveying engineering, cartography and GIS, cadastre and land management, photogrammetry, remote sensing and related disciplines. The Geodesy and Cartography is published under the umbrella of the Committee on Geodesy of the Polish Academy of Sciences (PAS). Printed version ISSN 2080-6736, On-line version ISSN 2300-2581,This paper summarizes the activity of the chosen Polish geodetic research teams in 2015–2018 in the fields of Earth: rotation, dynamics as well as magnetic field. It has been prepared for the needs of the presentation on the 27th International Union of Geodesy and Geodynamics General Assembly, Montreal, Canada. The part concerning Earth rotation is mostly focused on the use of modelling of diurnal and subdiurnal components of Earth rotation by including low frequency components of polar motion and UT1 in the analysis, study of free oscillations in Earth rotation derived from both space-geodetic observations of polar motion and the time variation of the second degree gravitational field coefficients derived from Satellite Laser Ranging (SLR) and Gravity Recovery and Climate Experiment (GRACE) observations, new methods of monitoring of Earth rotation, as well as studies on applications of the Ring Laser Gyroscope (RLG) for direct and continuous measurements of changes in Earth rotation and investigations of the hydrological excitation of polar motion. Much attention was devoted to the GRACE-derived gravity for explaining the influence of surface mass redistributions on polar motion. Monitoring of the geodynamical phenomena is divided into study on local and regional dynamics using permanent observations, investigation on tidal phenomena, as well as research on hydrological processes and sea level variation parts. Finally, the recent research conducted by Polish scientists on the Earth’s magnetic field is described.,
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