Non-parametric optimization of time-averaged quantities under small, time-varying forcing:

This study demonstrates a global, non-parametric, non-iterative optimization of time-mean value of a kind of index vibrated by time-varying forcing. It is based on the fact that the (steady) forced vibration of non-autonomous ordinary differential equation systems is well approximated by an analytical solution when the amplitude of forcing is sufficiently small and its base state without forcing is stable and steady. It is applied to optimize a time-averaged heat-transfer rate on a two-dimensional thermal convection field in a square cavity with horizontal temperature difference, and the globally optimal way of vibrational forcing, i.e. the globally optimal, spatial distribution of vibrational heat and vorticity sources, is first obtained. The maximized vibrational thermal convection corresponds well to the state of internal gravity wave resonance. In contrast, the minimized thermal convection is weak, keeping the boundary layers on both sidewalls thick.

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Global, Non-Parametric, Non-Iterative Optimization of Time-Averaged Quantities under Small, Time-Varying Forcing: An Application to a Thermal Convection Field

10.20944/preprints201809.0099.v2 ◽

2019 ◽

Author(s):

Hideshi ISHIDA ◽

Shiho Ihara ◽

Chiharu Okema ◽

Shohei Yamada ◽

Genta Kawahara

Keyword(s):

Thermal Convection ◽

Internal Gravity Wave ◽

Mean Value ◽

Small Time ◽

Time Varying ◽

Square Cavity ◽

Iterative Optimization ◽

Wave Resonance ◽

Ordinary Differential Equation Systems ◽

Non Parametric

This study demonstrates a global, non-parametric, non-iterative optimization of time-mean value of a kind of index vibrated by time-varying forcing. It is based on the fact that the (steady) forced vibration of non-autonomous ordinary differential equation systems is well approximated by an analytical solution when the amplitude of forcing is sufficiently small and its base state without forcing is linearly stable and steady. It is applied to optimize a time-averaged heat-transfer rate on a two-dimensional thermal convection field in a square cavity with horizontal temperature difference, and the globally optimal way of vibrational forcing, i.e. the globally optimal, spatial distribution of vibrational heat and vorticity sources, is first obtained. The maximized vibrational thermal convection corresponds well to the state of internal gravity wave resonance. In contrast, the minimized thermal convection is weak, keeping the boundary layers on both sidewalls thick.

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Has tourism driven house prices in Germany? Time-varying evidence since 1870

Tourism Economics ◽

10.1177/13548166211008832 ◽

2021 ◽

pp. 135481662110088

Author(s):

Sefa Awaworyi Churchill ◽

John Inekwe ◽

Kris Ivanovski

Keyword(s):

World War Ii ◽

Historical Data ◽

House Prices ◽

Housing Prices ◽

Time Varying ◽

Data Set ◽

Time Series Modelling ◽

The Impact ◽

Tourism Flows ◽

Non Parametric

Using a historical data set and recent advances in non-parametric time series modelling, we investigate the nexus between tourism flows and house prices in Germany over nearly 150 years. We use time-varying non-parametric techniques given that historical data tend to exhibit abrupt changes and other forms of non-linearities. Our findings show evidence of a time-varying effect of tourism flows on house prices, although with mixed effects. The pre-World War II time-varying estimates of tourism show both positive and negative effects on house prices. While changes in tourism flows contribute to increasing housing prices over the post-1950 period, this is short-lived, and the effect declines until the mid-1990s. However, we find a positive and significant relationship after 2000, where the impact of tourism on house prices becomes more pronounced in recent years.

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Wavelet multi-resolution approximation of time-varying frame structure

Advances in Mechanical Engineering ◽

10.1177/1687814018795596 ◽

2018 ◽

Vol 10 (8) ◽

pp. 168781401879559 ◽

Cited By ~ 2

Author(s):

Min Xiang ◽

Feng Xiong ◽

Yuanfeng Shi ◽

Kaoshan Dai ◽

Zhibin Ding

Keyword(s):

Parameter Estimation ◽

Degrees Of Freedom ◽

Structural Parameters ◽

Identification Problem ◽

Frame Structure ◽

Structural Parameter ◽

Time Varying ◽

Engineering Structures ◽

Time Frequency ◽

Non Parametric

Engineering structures usually exhibit time-varying behavior when subjected to strong excitation or due to material deterioration. This behavior is one of the key properties affecting the structural performance. Hence, reasonable description and timely tracking of time-varying characteristics of engineering structures are necessary for their safety assessment and life-cycle management. Due to its powerful ability of approximating functions in the time–frequency domain, wavelet multi-resolution approximation has been widely applied in the field of parameter estimation. Considering that the damage levels of beams and columns are usually different, identification of time-varying structural parameters of frame structure under seismic excitation using wavelet multi-resolution approximation is studied in this article. A time-varying dynamical model including both the translational and rotational degrees of freedom is established so as to estimate the stiffness coefficients of beams and columns separately. By decomposing each time-varying structural parameter using one wavelet multi-resolution approximation, the time-varying parametric identification problem is transformed into a time-invariant non-parametric one. In solving the high number of regressors in the non-parametric regression program, the modified orthogonal forward regression algorithm is proposed for significant term selection and parameter estimation. This work is demonstrated through numerical examples which consider both gradual variation and abrupt changes in the structural parameters.

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Estimating a Non-parametric, Colored Noise Model for Linear, Slowly Time-varying Systems

2008 IEEE Instrumentation and Measurement Technology Conference ◽

10.1109/imtc.2008.4547093 ◽

2008 ◽

Cited By ~ 1

Author(s):

J. Lataire ◽

R. Pintelon

Keyword(s):

Colored Noise ◽

Noise Model ◽

Time Varying ◽

Time Varying Systems ◽

Non Parametric

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ЭФФЕКТИВНОСТЬ МЕТОДОВ ОПРЕДЕЛЕНИЯ ГРУППОВЫХ СИСТЕМ ПРЕДПОЧТЕНИЙ ДИСПЕТЧЕРОВ НА ОПАСНОСТИ ХАРАКТЕРНЫХ ОШИБОК, СОВЕРШАЕМЫХ В ПРОЦЕССЕ УПРАВЛЕНИЯ ВОЗДУШНЫМ ДВИЖЕНИЕМ

Aerospace technic and technology ◽

10.32620/aktt.2018.6.12 ◽

2018 ◽

pp. 93-103

Author(s):

Алексей Николаевич Рева ◽

Шахин Шахвели-оглы Насиров ◽

Бала Мушгюль-оглы Мирзоев

Keyword(s):

Decision Making ◽

Parametric Optimization ◽

Professional Activity ◽

Air Traffic Controllers ◽

Main Emphasis ◽

Decision Making Processes ◽

Complex Decision Making ◽

Coefficient Of Concordance ◽

Complex Decision ◽

Non Parametric

The human factor problem should be solved by identifying, qualifying and preventing the erroneous actions of the air traffic controllers. It is presented two schemes explaining the structure of human qualimetry factor and the interaction of the components of the ICAO safety concept, where the main emphasis is on an aviation personnel’ attitude to dangerous actions or conditions, which is revealed by the qualimetry of the decision-making processes’ characteristics: the attitude towards risk (the main dominants and fuzzy assessments), levels of claims, dangerous qualities and preferences systems. The preferences systems are considered as ordered characteristics and indicators of professional activity, which are subjectively compared with the positions of influence on flight safety. The spectrum of n = 21 characteristic errors was formed considering the recommendations of ICAO, EUROCONTROL and accident statistics. It is determined that procedures of collecting the information of errors danger contribute their recognition, memorization, and avoidance: controllers who passed the test according to the proposed method before training made by one third fewer errors in its process. Two criteria for assessing group preferences are realized: the level of consensus (known as Kendall’s coefficient of concordance) and the severity of the ranking, determined by the presence of "related" ranks, for which a special indicator is introduced. It is defined that this indicator should be determined both for the sample of respondents and for the preferences group systems of developed with the chosen method of individual opinions’ aggregation. It was performed the comparative analysis of complex decision-making strategies of effectiveness in the construction of a preferences group systems m = 65 controllers: sum and averaging of ranks, classical criteria (Wald's, Savage's and Laplace's criterion), optimal prediction, applying the non-parametric optimization of the preferences group systems. The non-parametric optimization of the group system of pre-readings was carried out by Kemeny median and it was proved that it was the closest to all the results obtained by other methods and strategies

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Non-parametric Optimization Using Subspace-Based Objective Functions

10.1007/978-3-030-74258-4_22 ◽

2021 ◽

pp. 339-357

Author(s):

Angelo Aloisio ◽

Riccardo Cirella ◽

Massimo Fragiacomo ◽

Rocco Alaggio

Keyword(s):

Parametric Optimization ◽

Objective Functions ◽

Non Parametric

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Lateral Dynamics of Walking-Like Mechanical Systems and Their Chaotic Behavior

International Journal of Bifurcation and Chaos ◽

10.1142/s0218127419300246 ◽

2019 ◽

Vol 29 (09) ◽

pp. 1930024

Author(s):

Sergej Čelikovský ◽

Volodymyr Lynnyk

Keyword(s):

Stability Region ◽

Inverted Pendulum ◽

Chaotic Behavior ◽

Mechanical Systems ◽

Small Time ◽

Time Varying ◽

External Forcing ◽

Double Support ◽

Lateral Dynamics ◽

Detailed Mathematical Analysis

A detailed mathematical analysis of the two-dimensional hybrid model for the lateral dynamics of walking-like mechanical systems (the so-called hybrid inverted pendulum) is presented in this article. The chaotic behavior, when being externally harmonically perturbed, is demonstrated. Two rather exceptional features are analyzed. Firstly, the unperturbed undamped hybrid inverted pendulum behaves inside a certain stability region periodically and its respective frequencies range from zero (close to the boundary of that stability region) to infinity (close to its double support equilibrium). Secondly, the constant lateral forcing less than a certain threshold does not affect the periodic behavior of the hybrid inverted pendulum and preserves its equilibrium at the origin. The latter is due to the hybrid nature of the equilibrium at the origin, which exists only in the Filippov sense. It is actually a trivial example of the so-called pseudo-equilibrium [Kuznetsov et al., 2003]. Nevertheless, such an observation holds only for constant external forcing and even arbitrary small time-varying external forcing may destabilize the origin. As a matter of fact, one can observe many, possibly even infinitely many, distinct chaotic attractors for a single system when the forcing amplitude does not exceed the mentioned threshold. Moreover, some general properties of the hybrid inverted pendulum are characterized through its topological equivalence to the classical pendulum. Extensive numerical experiments demonstrate the chaotic behavior of the harmonically perturbed hybrid inverted pendulum.

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