scholarly journals Identification of Nonlinear Vibrating Structures: Part II—Applications

1987 ◽  
Vol 54 (4) ◽  
pp. 923-929 ◽  
Author(s):  
S. F. Masri ◽  
R. K. Miller ◽  
A. F. Saud ◽  
T. K. Caughey
Keyword(s):  
Structural Characteristics ◽  
Companion Paper ◽  
Dynamic Loads ◽  
High Fidelity ◽  
Data Set ◽  
Reduced Order ◽  
Vibrating Structures ◽  
Convenient Means ◽  
Calibration Problem ◽  
Identification Test

A time-domain procedure for the identification of nonlinear vibrating structures, presented in a companion paper, is applied to a “calibration” problem which incorporates realistic test situations and nonlinear structural characteristics widely encountered in the applied mechanics field. The “data” set is analyzed to develop suitable, approximate nonlinear system representations. Subsequently, a “validation” test is conducted to demonstrate the range of validity of the method under discussion. It is shown that the procedure furnishes a convenient means for constructing reduced-order nonlinear nonparametric mathematical models of reasonably high fidelity in regard to reproducing the response of the test article under dynamic loads that differ from the identification test loads.

scholarly journals Statistical analysis of Stromboli VLP tremor in the band [0.1–0.5] Hz: some consequences for vibrating structures

2006 ◽  
Vol 13 (4) ◽  
pp. 393-400 ◽  
Author(s):  
E. De Lauro ◽  
S. De Martino ◽  
M. Falanga ◽  
M. Palo
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Noise Source ◽  
Volcanic Tremor ◽  
Large Data ◽  
Musical Instruments ◽  
Data Set ◽  
Long Period ◽  
Vibrating Structures ◽  
Analyze Time Series

Abstract. We analyze time series of Strombolian volcanic tremor, focusing our attention on the frequency band [0.1–0.5] Hz (very long period (VLP) tremor). Although this frequency band is largely affected by noise, we evidence two significant components by using Independent Component Analysis with the frequencies, respectively, of ~0.2 and ~0.4 Hz. We show that these components display wavefield features similar to those of the high frequency Strombolian signals (>0.5 Hz). In fact, they are radially polarised and located within the crater area. This characterization is lost when an enhancement of energy appears. In this case, the presence of microseismic noise becomes relevant. Investigating the entire large data set available, we determine how microseismic noise influences the signals. We ascribe the microseismic noise source to Scirocco wind. Moreover, our analysis allows one to evidence that the Strombolian conduit vibrates like the asymmetric cavity associated with musical instruments generating self-sustained tones.

Real estate development in the city of Athens during the financial crisis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Maria Nikitidou ◽  
Fragiskos Archontakis ◽  
Athanasios Tagkalakis
Keyword(s):  
Financial Crisis ◽  
Real Estate ◽  
Structural Characteristics ◽  
House Prices ◽  
Real Estate Market ◽  
Structural Factors ◽  
Data Set ◽  
Content Type ◽  
Capital Financing ◽  
The City

Purpose This study aims to determine how the prices of residential properties in the Greek real estate sector are affected by their structural characteristics and by the prevailing economic factors during recession. Design/methodology/approach Based on 13,835 valuation reports for the city of Athens, covering a period of 11 years (2006–2016), this study develops a series of econometric models, taking into account both structural characteristics of the property market and the macroeconomic relevant variables. Finally, the city of Athens is divided into sub-regions and the different effects of the structural factors in each area are investigated via spatial analysis confirming the validity of the baseline model. Findings Findings show that the size, age, level, parking and storage space can explain the property price movements. Moreover, the authors find evidence that it is primarily house demand variables (e.g. the annual average wage, the unemployment rate, the user cost of capital, financing constraints and expectations about the future course of the house market) that affect house prices in a statistically significant manner and with the correct sign. Finally, using a difference-in-differences approach, this study finds that an increase in house demand (on account of net migration) led to higher house prices in smaller and older than in larger and younger apartments in areas with high concentration of immigrants. Originality/value This study uses a novel data set to help entities, individuals and policy-makers to understand how the recent economic and financial crisis has affected the real estate market in Athens.

scholarly journals ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction—Part I—Influence of the RANS Simulation

Acoustics ◽  
2020 ◽  
Vol 2 (3) ◽  
pp. 539-578
Author(s):  
Carolin Kissner ◽  
Sébastien Guérin ◽  
Pascal Seeler ◽  
Mattias Billson ◽  
Paruchuri Chaitanya ◽  
...  
Keyword(s):  
Turbulence Model ◽  
Analytical Methods ◽  
Companion Paper ◽  
Broadband Noise ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Data Set ◽  
The Past ◽  
Flow Turbulence ◽  
Diverse Data

A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.

scholarly journals Identification of Nonlinear Vibrating Structures: Part I—Formulation

1987 ◽  
Vol 54 (4) ◽  
pp. 918-922 ◽  
Author(s):  
S. F. Masri ◽  
R. K. Miller ◽  
A. F. Saud ◽  
T. K. Caughey
Keyword(s):  
Time Domain ◽  
Parametric Identification ◽  
Companion Paper ◽  
Sufficient Accuracy ◽  
Recursive Least Squares ◽  
Estimation Methods ◽  
Free Oscillations ◽  
Vibrating Structures ◽  
Parameter Estimation Methods ◽  
Identification Techniques

A self-starting multistage, time-domain procedure is presented for the identification of nonlinear, multi-degree-of-freedom systems undergoing free oscillations or subjected to arbitrary direct force excitations and/or nonuniform support motions. Recursive least-squares parameter estimation methods combined with non-parametric identification techniques are used to represent, with sufficient accuracy, the identified system in a form that allows the convenient prediction of its transient response under excitations that differ from the test signals. The utility of this procedure is demonstrated in a companion paper.

The short-term fate of urea applied to barley in a humid climate. II. A simple model

Soil Research ◽  
1984 ◽  
Vol 22 (2) ◽  
pp. 181 ◽  
Author(s):  
DR Scotter ◽  
IH Mohammed ◽  
PEH Gregg
Keyword(s):  
Simple Model ◽  
Plant Uptake ◽  
Field Experiments ◽  
Root Zone ◽  
Companion Paper ◽  
Fertilizer Application ◽  
Fertilizer N ◽  
Humid Climate ◽  
Data Set ◽  
Programmable Calculator

A simple model describing the transformations, leaching and plant uptake of the nitrogen (N) in urea fertilizer applied to a barley crop is presented. The model considers the root zone as a single compartment and uses daily time steps, and so can be run on a small programmable calculator. It consists of separate submodels for water, fertilizer N and native soil N. Data from a field experiment described in a companion paper were used for parameterization, and the model was then tested on another data set from that experiment. The model successfully predicted the effect, on the leaching and plant uptake of fertilizer N, of a large increase in rainfall plus irrigation from 103 mm to 186 mm in the 35 days following sowing and urea application. As an example of the model's utility, it is used to predict that if 30 mm of drainage occurred within 24 h of fertilizer application, about 33% of the fertilizer N would be leached from the root zone in the silt loam soil studied. However, the same amount of drainage occurring a week after fertilizer application would result only in about 8% of the fertilizer N being leached. The complementary roles that process-oriented field experiments and simple mechanistic models can play in soil fertility research are discussed.

scholarly journals GENETIC ALGORITHM-BASED CALIBRATION OF REDUCED ORDER GALERKIN MODELS

2011 ◽  
Vol 16 (1) ◽  
pp. 233-247 ◽  
Author(s):  
Witold Stankiewicz ◽  
Robert Roszaka ◽  
Marek Morzyńskia
Keyword(s):  
Genetic Algorithm ◽  
Bluff Body ◽  
Calibration Procedure ◽  
Galerkin Projection ◽  
Reduced Order Models ◽  
Data Set ◽  
Reduced Order ◽  
Low Dimensional ◽  
Fluid Behaviour ◽  
Proper Orthogonal

Low-dimensional models, allowing quick prediction of fluid behaviour, are key enablers of closed-loop flow control. Reduction of the model's dimension and inconsistency of high-fidelity data set and the reduced-order formulation lead to the decrease of accuracy. The quality of Reduced-Order Models might be improved by a calibration procedure. It leads to global optimization problem which consist in minimizing objective function like the prediction error of the model. In this paper, Reduced-Order Models of an incompressible flow around a bluff body are constructed, basing on Galerkin Projection of governing equations onto a space spanned by the most dominant eigenmodes of the Proper Orthogonal Decomposition (POD). Calibration of such models is done by adding to Galerkin System some linear and quadratic terms, which coefficients are estimated using Genetic Algorithm.

scholarly journals Search for Non-Gaussianities in the WMAP Data with the Scaling Index Method

2011 ◽  
Vol 2011 ◽  
pp. 1-21 ◽  
Author(s):  
G. Rossmanith ◽  
H. Modest ◽  
C. Räth ◽  
A. J. Banday ◽  
K. M. Górski ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Microwave Background ◽  
Index Method ◽  
Data Set ◽  
Local Type ◽  
Statistical Measures ◽  
Wmap Data ◽  
Statistical Isotropy ◽  
Scaling Index ◽  
Scaling Index Method

In the recent years, non-Gaussianity and statistical isotropy of the Cosmic Microwave Background (CMB) was investigated with various statistical measures, first and foremost by means of the measurements of the WMAP satellite. In this paper, we focus on the analyses that were accomplished with a measure of local type, the so-calledScaling Index Method(SIM). The SIM is able to detect structural characteristics of a given data set and has proven to be highly valuable in CMB analysis. It was used for comparing the data set with simulations as well as surrogates, which are full-sky maps generated by randomisation of previously selected features of the original map. During these investigations, strong evidence for non-Gaussianities as well as asymmetries and local features could be detected. In combination with the surrogates approach, the SIM detected the highest significances for non-Gaussianity to date.

Estimation of Local Ice Pressure Using Up-Crossing Rate

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Chuanke Li ◽  
Ian J. Jordaan ◽  
Rocky S. Taylor
Keyword(s):  
Probabilistic Method ◽  
Companion Paper ◽  
Offshore Structures ◽  
Maximum Pressure ◽  
Local Pressure ◽  
Data Set ◽  
Pressure Area ◽  
Rate Method ◽  
Ice Pressure ◽  
Maximum Method

Ice load estimation is required in the design of ships and offshore structures for arctic and subarctic conditions. This paper focuses on the estimation of local ice pressures. The “event-maximum” method for local ice pressure analysis is a probabilistic method based on the maximum pressure of a given event; other local peaks in the data are not included. To study how this may affect local ice pressure estimates, a new probabilistic method based on the up-crossing rate was developed. Field data from 1982 Polar Sea arctic trials in the Beaufort Sea are processed as a time series. Up-crossing rates at different local pressure levels are obtained for local areas of interest. A relationship between up-crossing rate and local pressure-area results is established. Results from the analysis of full-scale data using the event-maximum method are presented for the selected data set; a more comprehensive set of results for the analysis of available ship-ice interaction data is presented in a companion paper. For a sample case, local ice pressure estimates obtained using the up-crossing rate method are compared with results obtained using the event-maximum method. The local pressure-area relationship is found to be similar for both the up-crossing rate method and the event-maximum method. For design curves based on the data set considered, estimates using the event-maximum method were more conservative than those obtained using the up-crossing rate method. The up-crossing rate approach is promising; analysis of additional data sets is recommended to allow broader comparison of the methods.

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