Modal Analysis of Nonviscously Damped Beams

2006 ◽  
Vol 74 (5) ◽  
pp. 1026-1030 ◽  
Author(s):  
S. Adhikari ◽  
M. I. Friswell ◽  
Y. Lei
Keyword(s):  
Natural Frequencies ◽  
Past History ◽  
Kernel Functions ◽  
Mode Shapes ◽  
Damping Force ◽  
The Past ◽  
Convolution Integrals ◽  
Special Cases ◽  
History Of ◽  
Damping Model

Linear dynamics of Euler–Bernoulli beams with nonviscous nonlocal damping is considered. It is assumed that the damping force at a given point in the beam depends on the past history of velocities at different points via convolution integrals over exponentially decaying kernel functions. Conventional viscous and viscoelastic damping models can be obtained as special cases of this general damping model. The equation of motion of the beam with such a general damping model results in a linear partial integro-differential equation. Exact closed-form equations of the natural frequencies and mode shapes of the beam are derived. Numerical examples are provided to illustrate the new results.

Lancaster’s Method of Damping Identification Revisited

2002 ◽  
Vol 124 (4) ◽  
pp. 617-627 ◽  
Author(s):  
Sondipon Adhikari
Keyword(s):  
Transfer Functions ◽  
Past History ◽  
A Priori ◽  
Kernel Functions ◽  
Mode Shapes ◽  
Viscous Damping ◽  
Damping Matrix ◽  
Convolution Integrals ◽  
History Of ◽  
Damped Systems

Identification of damping is an active area of research in structural dynamics. In one of the earliest works, Lancaster [1] proposed a method to identify the viscous damping matrix from measured natural frequencies and mode shapes. His method requires the modes to be normalized in a particular way, which in turn a priori needs the very same viscous damping matrix. A method, based on the poles and residues of the measured transfer functions, has been proposed to overcome this basic difficulty associated with Lancaster’s method. This approach is then extended to a class of nonviscously damped systems where the damping forces depend on the past history of the velocities via convolution integrals over some kernel functions. Suitable numerical examples are given to illustrate the modified Lancaster’s method developed here.

A Reduced Second-Order Approach for Linear Viscoelastic Oscillators

2010 ◽  
Vol 77 (4) ◽  
Author(s):  
Sondipon Adhikari
Keyword(s):  
Past History ◽  
Kernel Functions ◽  
Second Order ◽  
Order System ◽  
Closed Form Expression ◽  
Internal Variables ◽  
Dynamical Response ◽  
Convolution Integrals ◽  
History Of ◽  
Second Order Systems

This paper proposes a new approach for the reduction in the model-order of linear multiple-degree-of-freedom viscoelastic systems via equivalent second-order systems. The assumed viscoelastic forces depend on the past history of motion via convolution integrals over kernel functions. Current methods to solve this type of problem normally use the state-space approach involving additional internal variables. Such approaches often increase the order of the eigenvalue problem to be solved and can become computationally expensive for large systems. Here, an approximate reduced second-order approach is proposed for this type of problems. The proposed approximation utilizes the idea of generalized proportional damping and expressions of approximate eigenvalues of the system. A closed-form expression of the equivalent second-order system has been derived. The new expression is obtained by elementary operations involving the mass, stiffness, and the kernel function matrix only. This enables one to approximately calculate the dynamical response of complex viscoelastic systems using the standard tools for conventional second-order systems. Representative numerical examples are given to verify the accuracy of the derived expressions.

Analysis of Asymmetric Nonviscously Damped Linear Dynamic Systems

2003 ◽  
Vol 70 (6) ◽  
pp. 885-893 ◽  
Author(s):  
S. Adhikari ◽  
N. Wagner
Keyword(s):  
State Space ◽  
Past History ◽  
Kernel Functions ◽  
Extended State ◽  
State Space Approach ◽  
Linear Dynamic Systems ◽  
Convolution Integrals ◽  
History Of ◽  
Damped Systems ◽  
Space Approach

Multiple-degree-of-freedom linear asymmetric nonviscously damped systems are considered. It is assumed that the nonviscous damping forces depend on the past history of velocities via convolution integrals over exponentially decaying kernel functions. An extended state-space approach involving a single asymmetric matrix is proposed. The nature of the eigensolutions in the extended state space has been explored. Some useful results relating the modal matrix in the extended state space and the modal matrix in the original space has been derived. Numerical examples are provided to illustrate the results.

Iterative Methods for Eigenvalues of Viscoelastic Systems

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Sondipon Adhikari ◽  
Blanca Pascual
Keyword(s):  
Past History ◽  
Iterative Algorithms ◽  
Kernel Functions ◽  
Degree Of Freedom ◽  
Internal Variables ◽  
State Space Approach ◽  
Convolution Integrals ◽  
Complex Eigenvalues ◽  
History Of ◽  
Space Approach

This paper proposes a new iterative approach for the calculation of eigenvalues of single and multiple degree-of-freedom viscoelastic systems. The Biot model of viscoelasticity is assumed. With this model, the viscoelastic forces depend on the past history of motion via convolution integrals over exponentially decaying kernel functions. Current methods to solve this type of problem normally use the state-space approach involving additional internal variables. Such approaches often increase the order of the eigenvalue problem to be solved and can become computationally expensive for large systems. The method proposed in this paper is aimed to address this issue. In total, five iterative algorithms for the real and complex eigenvalues of single and multiple degree-of-freedom systems have been proposed. The results are obtained in terms of explicit closed-form expressions. This enables one to approximately calculate the eigenvalues of complex viscoelastic systems using the eigenvalues of the underlying elastic systems. Representative numerical examples are given to verify the accuracy of the derived expressions.

Obituary notices of fellows deceased

1877 ◽  
Vol 25 (171-178) ◽  
Keyword(s):  
Past History ◽  
The Past ◽  
The Earth ◽  
History Of ◽  
Reign Of Terror ◽  
Accurate Observation

George Poulett Scrope. It is scarcely possible at the present day to realize the conditions of that intellectual “reign of terror” which prevailed at the commencement of the present century, as the consequence of the unreasoning prejudice and wild alarm excited by the early progress of geological inquiry. At that period, every attempt to explain the past history of the earth by a reference to the causes still in operation upon it was met, not by argument, but by charges of atheism against its propounder; and thus Hutton’s masterly fragment of a ‘Theory of the Earth,’ Playfair’s persuasive‘ Illustrations,’ and Hall’s records of accurate observation and ingenious experiment had come to be inscribed m a social Index Expurgatorius ,and for a while, indeed, might have seemed to be consigned to total oblivion. Equally injurious suspicions were aroused against the geologist who dared to make allusion to the important part which igneous forces have undoubtedly played in the formation of certain rocks; for the authority of Werner had acquired an almost sacred cha­racter; and “ Vulcanists ” and “ Huttonians ” were equally objects of aversion and contempt. To two men who have very recently—and within a few months of one another—passed away from our midst, science is indebted for boldly en­countering and successfully overcoming this storm of prejudice. Hutton and his friends lived a generation too soon ; and thus it was reserved tor Lyell and Scrope to carry out the task which the great Scotch philosopher had failed to accomplish, namely, the removal of geology from the domain of speculation to that of inductive science.

scholarly journals Tingkat Kesiapan Kali Pepe untuk Dikembangakan sebagai Kawasan Wisata Berbasis Sungai di Kota Surakarta

Arsitektura ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 67
Author(s):  
Nurul Widowati ◽  
Winny Astuti ◽  
Murtanti Jani Rahayu
Keyword(s):  
Quantitative Research ◽  
Past History ◽  
River Flooding ◽  
Know How ◽  
The Past ◽  
Institutional Infrastructure ◽  
Strategic Location ◽  
Readiness Level ◽  
History Of ◽  
The Government

<div><p><em>Surakarta is a city that has the potential of the river. But in the process, these rivers suffered environmental degradation as a function instead of the banks into slums and squatter, and functions of rivers that serve as places of waste disposal. Government’s city of Surakarta has done various setup area of the river. One of the targeted structuring Pepe-River is often known by the name Kali Pepe. Kali Pepe is the river which has the most strategic location because it divides the centre of city and the river has a past history of Surakarta. Kali Pepe is the witness of history where culture and trade activities in the rapidly growing city of Surakarta in the past with the ecological function and physical function as transportation trade.Setuping Kali Pepe, according to the Mayor of Surakarta, is directed to serve as recreation/tourism area. Since the Surakarta Mayor initiated the year 2015 that Kali Pepe as a tourist area. The initiated moves the government and society in order to more actively participate in developing the area into a tourist area. This research would like to know how the readiness level of the Kali Pepe area to be developed as a tourist area-based streams. The components of preparedness were seen from aspect of attractions or natural tourist attraction, artificial attractions, acessesiblity, institutional, infrastructure supporting tourism, and the behavior of the flooding of the river. This research is quantitative research in methods of scoring analysis. The result of this research has shown that Kali Pepe less readiness to be developed as a tourist area-based stream. Aspects of accessibility and infrastructure supporting tourism were an aspect which has a readiness. But for this aspect of the attraction, institutional and river flooding behavior is still in the stage of less readiness.</em></p><p> </p><p><strong><em>Keywords:</em></strong><em> readiness, tourist areas, river tours</em></p></div>

scholarly journals CAGAR BUDAYA SANG PENUTUR MASA SILAM CULTURAL HERITAGE THE TELLER OF THE PAST

Kebudayaan ◽  
2019 ◽  
Vol 14 (1) ◽  
pp. 27-42
Author(s):  
I Made Sutaba
Keyword(s):  
Cultural Heritage ◽  
Past History ◽  
Literature Study ◽  
The Past ◽  
Past Life ◽  
History Of ◽  
Research Goal ◽  
The Many ◽  
Religious Aspects ◽  
Typology Analysis

Archaeological researches in Indonesia have discovered a number of various historical and archaeological artifacts that belong to cultural heritage. As historical evidences, this cultural heritage is an important source of the plural information and messages of the past life of our society. It is remarkable that this cultural heritage has some problems for example problem of typology, function, meanings, and the other for the society. Studying the problems, it is interesting to do research on its function as a teller of the past history that contained various aspects of the life of our society that not yet studied until today. By learning the problems, this research goal is to find the answer of the problems. To reach this goal, we do this research gradually by collecting data through literature study and field observation along with interviews. The next step is analysis carried out through methods of typology analysis, contextual, functional analysis, ethno archaeological and ethno historical approach. Finally the result showed that the function of our cultural heritage is as teller of the many-sided aspects of the past history of our artifacts such as technological aspects, social, and religious aspects but it is impossible to get full completed information due to some reasons. Keywords: archaeological and historical artifacts, cultural heritages, teller of the past.  AbstrakPenyelidikan arkeologi di Indonesia sudah berhasil menemukan artefak sejarah dan arkeologi yang beraneka ragam, yang tergolong sebagai warisan budaya. Sebagai bukti-bukti sejarah, warisan budaya ini adalah sumber informasi dan pesan-pesan kehidupan masyarakat masa lalu yang bersifat pluralistik. Menarik perhatian, bahwa warisan budaya ini mempunyai permasalahan yaitu, permasalahan tipologi, fungsi dan makna dalam kehidupan masyarakat. Mempelajari masalah ini, sangat menarik untuk melakukan penelitian mengenai fungsinya sebagai penutur sejarah masa silam, yang mengandung aneka ragam, aspek kehidupan masyarakat, yang belum dikaji sampai sekarang. Dengan mencermati permasalahan ini, maka tujuan penelitian ini, adalah untuk meneliti permasalahan tadi. Untuk mencapai tujuan ini, penulis melakukan penelitian secara bertahap melalui pengumpulan data dengan metode kajian pustaka dan observasi lapangan yang disertai dengan wawancara. Langkah selanjutnya, adalah melakukan analisis dengan analisis tipologi, kontekstual, analisis fungsional, pendekatan etnoarkeologi dan etnohistori. Hasil penelitian ini menunjukkan bahwa cagar budaya itu berfungsi sebagai penutur kehidupan masa silam yang mengandung aspek yang bersfiat jamak, adalah aspek teknologi, sosial dan religi, tetapi tidak mungkin untuk mendapat informasi yang lengkap karena berbagai faktor.Kata kunci: peninggalan sejarah dan purbakala, warisan budaya, penutur masa silam.

scholarly journals Predictors of proximity to others in colony housed shelter cats (Felis silvestris catus)

2016 ◽  
pp. 24 ◽  
Author(s):  
Malini Suchak ◽  
Michael Piombino ◽  
Kalina Bracco
Keyword(s):  
Past History ◽  
Individual Variability ◽  
Felis Silvestris Catus ◽  
Future Studies ◽  
The Past ◽  
Close Proximity ◽  
History Of ◽  
Adult Cats ◽  
Stress Behaviors ◽  
High Degree

Colony housing of cats allows shelters to maximize the number of cats housed in limited space. Most research on colony-housed cats examines stress in relation to group size or enclosure size.  While this is important for evaluating welfare, it is equally important to understand how cats are interacting socially in these colonies. We observed 259 adult cats housed in groups of two to eight individuals. Scan samples were used to assess how frequently individual cats were in close proximity to other cats. These data were used to measure individual differences in sociability and patterns of proximity to certain partners. We used information about the past history of the cat, which was collected upon admission to the shelter to identify predictors of time spent in proximity. There was a high degree of inter-individual variability in sociability. Strays tended to spend less time in proximity to other cats, and this effect was most pronounced in females.However, none of the information collected upon admission predicted patterns of proximity to certain partners, or which cats spent time in association witheach other. Future studies should explore the implications of differences in sociability by associating observations of social behavior and stress behaviors.

MEASURING SOLAR DIAMETER WITH 2012 VENUS TRANSITS

2013 ◽  
Vol 23 ◽  
pp. 451-453 ◽  
Author(s):  
COSTANTINO SIGISMONDI
Keyword(s):  
Past History ◽  
Logarithmic Derivative ◽  
Solar Limb ◽  
Absolute Calibration ◽  
The Sun ◽  
Solar Diameter ◽  
The Past ◽  
History Of ◽  
Better Than

The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement of the solar diameter with the Venus transit of 5/6 June 2012 with an unprecedented accuracy, and with absolute calibration given by the ephemerides.

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