The Life Cycle Hypothesis and Uncertainty: Analyzing Aging Savings Relationship in Tunisia

This research empirically checks the effect of uncertainty on aging-saving link that is indirectly captured by an auxiliary variable: the unemployment. It looks at the nexus population aging and savings by bringing out the unemployment context importance in determination saving behavior notably in a setting of unavailability of unemployment allowance. To better estimate population aging, it considers the old-age dependency ratio besides the total dependency one, which is the usually indicator used. Applying the Structural VAR model, the variance decomposition technique and the response impulse function, on Tunisia during 1970–2019, it puts on show that elderly do not dissave in a context of enduring unemployment and unavailability of unemployment allowance. Unemployment is an important factor able to shaping the saving behavior and to distort the life cycle hypothesis’s prediction. Consequently, the life cycle hypothesis cannot be validated under uncertainty. Hence, aging does not to alter savings systematically. The nature of aging-saving relationship is upon to social and economic context.

Free vibrations of a thin-walled curvilinear section of an oil-trunk pipeline during ground laying

In this article authors obtained solutions to determine the ground curved sections free vibrations of thin-walled large-diameter pipelines with a liquid flow, based on a geometrically nonlinear version of the semi-momentless toroidal shells medium bending theory by V.Z. Vlasov and V.V. Novozhilov. The pipeline is a toroidal shell, the design scheme is presented in the form of a half torus. Angle β = 1800. The shell is laid on an elastic foundation and makes contact with the ground along a narrow strip. The problem of the soil pressure influence on the shell along a narrow strip is solved as a contact problem, using Fourier's series and an impulse function. The shell is exposed to the cooperative effect of the internal operating pressure, the liquid flowing pressure, the elastic soil foundation, and changes in the geometric characteristics. Motion equations of the middle shell surface are obtained taking into account the geometric and mechanical characteristics, and all the components of the shell material inertial forces. The hinged fastening of the shell ends is taken as the limiting condition. Using the semi-momentless shell theory assumptions, displacements in the longitudinal and circumferential directions are obtained. The solution to the problem of determining the free vibrations comes down to solving the problem of determining AB matrix values. The solutions obtained make it possible to determine the free vibrations frequencies at various wavenumbers values in the longitudinal and circumferential directions, and also make it possible to determine the internal operating pressure contribution, the soil bed coefficient, and geometric characteristics to the pipeline free vibrations frequencies.

Rapid Prediction of Strong Ground Motions from Major Earthquakes: An Example in the Wudu Basin, Sichuan, China

ABSTRACT Rapid prediction of ground motions of major earthquakes can assist emergency response and postseismic damage assessment. Numerical simulations can perform such prediction. However, they need a large number of calculations based on real data and depend on large-scale computation resources, limiting practice of real-time prediction. To solve this problem, this article proposes a new prediction method based on a 3D transfer function, which is obtained by solving the site seismic response to three impulse function excitations that can be calculated by different pre-event 3D physics-based numerical simulations. This approach only needs one seismic record in the study area and can quickly (near-real time) predict ground motions in the whole study area. We verify the proposed approach with an Mw 5.7 aftershock of the 2008 Mw 7.9 Wenchuan earthquake in the Wudu basin, Sichuan Province, China. The results show that this method is feasible and has sufficient accuracy in nearly real-time prediction of seismic ground motions.

Simulative study of raised cosine impulse function with Hamming grating profile based Chirp Bragg grating fiber

This work simulate the raised Cosine impulse function with Hamming grating profile based chirp Bragg grating fiber. The transmittivity/reflectivity, the grating ref index of the chirp grating fiber variations, real/imaginary coupling coefficient variations and the cross section monitor of the mesh transmission variations are simulated and clarified versus the length of grating. The transmission/reflection spectrum, input grating pulse width intensity spectrum, and the output grating pulse width intensity against the grating wavelength are demonstrated clearly. All the obtained results are demonstrated with the OptiGrating simulation software version 12. The transmittivity/reflectivity of chirp grating fiber, the grating ref index of chirp grating fiber, the cross section monitor of the mesh transmission and the real/imaginary coupling coefficient variations are simulated and demonstrated against the grating performance parameters.

Research on Feature Extraction Method of Engine Misfire Fault Based on Signal Sparse Decomposition

Engine vibration signals are easy to be interfered by other noise, causing feature signals that represent its operating status get submerged and further leading to difficulty in engine fault diagnosis. In addition, most of the signals utilized to verify the extraction method are derived from numerical simulation, which are far away from the real engine signals. To address these problems, this paper combines the priority of signal sparse decomposition and engine finite element model to research a novel feature extraction method for engine misfire diagnosis. Firstly, in order to highlight resonance regions related with impact features, the vibration signal is performed with a high-pass filter process. Secondly, the dictionary with clear physical meaning is constructed by the unit impulse function, whose parameters are associated with engine system modal characteristics. Afterwards, the signals that indicate the engine operating status are accurately reconstructed by segmental matching pursuit. Finally, a series of precise simulation signals originated from the engine dynamic finite element model, and experimental signals on the automotive engine are used to verify the proposed method’s effectiveness and antinoise performance. Additionally, comparisons with wavelet decomposition further show the proposed method to be more reliable in engine misfire diagnosis.

Study of structure of flows of a technological apparatus using the theory of random functions

The object of research is the structure of flows in the absorber of hydrogen chloride. One of the most problematic areas in the study of flow hydrodynamics in chemical-technological devices are both technological and technical difficulties, when the device is exposed to random disturbances and/or the supply of a standard indicator is impossible due to a violation of the technological regulations. A method for studying the hydrodynamic structure of flows in a shelf absorber of hydrogen chloride of the «Korobon-KA» type (Germany) in the normal operation of a chemical apparatus using the theory of random functions is proposed. An industrial experiment was carried out on the operating equipment to determine the input and output concentrations of the components of the gas flow. The absorber of hydrogen chloride is considered as a one-dimensional object, at the input of which a random function acts – the concentration of hydrogen chloride in the input stream, and at the output there is a random variable – the concentration of hydrogen chloride in the output stream. The method for determining hydrogen chloride and chlorine in a gas stream is based on the absorption of chlorine by a solution of potassium iodide, followed by titration of the released iodine with sodium thiosulfate. In parallel, portions of acid were sampled at the inlet and outlet, and then the density and temperature of the hydrochloric acid solutions were determined. An algorithm for calculating the impulse function estimates is developed. The obtained experimental data are smoothed. As a result of processing the experimental data, autocorrelation and cross-correlation functions were obtained, the Wiener-Hopf equation was solved, and the impulse weight function was obtained. Having calculated the moments of the obtained impulse weight function, it was proved that the structure of flows in the «Korobon-KA» absorber can be satisfactorily described by the ideal displacement model. The calculations were carried out in software environments MathCAD, Matlab. According to the results obtained, the proposed method for determining the hydrodynamic structure of flows will find application in the study of chemical-technological devices, when the object is exposed to random disturbances and the supply of a standard indicator is impossible due to violation of technological regulations. This makes it possible to find the parameters of flow hydrodynamics in the apparatus in the mode of its normal operation.

Lamb Wave Scattering Analysis for Interface Damage Detection between a Surface-Mounted Block and Elastic Plate

Since stringers are often applied in engineering constructions to improve thin-walled structures’ strength, methods for damage detection at the joints between the stringer and the thin-walled structure are necessary. A 2D mathematical model was employed to simulate Lamb wave excitation and sensing via rectangular piezoelectric-wafer active transducers mounted on the surface of an elastic plate with rectangular surface-bonded obstacles (stiffeners) with interface defects. The results of a 2D simulation using the finite element method and the semi-analytical hybrid approach were validated experimentally using laser Doppler vibrometry for fully bonded and semi-debonded rectangular obstacles. A numerical analysis of fundamental Lamb wave scattering via rectangular stiffeners in different bonding states is presented. Two kinds of interfacial defects between the stiffener and the plate are considered: the partial degradation of the adhesive at the interface and an open crack. Damage indices calculated using the data obtained from a sensor are analyzed numerically. The choice of an input impulse function applied at the piezoelectric actuator is discussed from the perspective of the development of guided-wave-based structural health monitoring techniques for damage detection.

Quantifying Information without Entropy: Identifying Intermittent Disturbances in Dynamical Systems

A system’s response to disturbances in an internal or external driving signal can be characterized as performing an implicit computation, where the dynamics of the system are a manifestation of its new state holding some memory about those disturbances. Identifying small disturbances in the response signal requires detailed information about the dynamics of the inputs, which can be challenging. This paper presents a new method called the Information Impulse Function (IIF) for detecting and time-localizing small disturbances in system response data. The novelty of IIF is its ability to measure relative information content without using Boltzmann’s equation by modeling signal transmission as a series of dissipative steps. Since a detailed expression of the informational structure in the signal is achieved with IIF, it is ideal for detecting disturbances in the response signal, i.e., the system dynamics. Those findings are based on numerical studies of the topological structure of the dynamics of a nonlinear system due to perturbated driving signals. The IIF is compared to both the Permutation entropy and Shannon entropy to demonstrate its entropy-like relationship with system state and its degree of sensitivity to perturbations in a driving signal.

Vibration Analysis of Deep Groove Ball Bearings With Local Defect Using a New Displacement Excitation Function

Bearings are vital parts of many mechanical equipment, the vibration signal analysis of bearings with local defects is important in guiding the fault diagnosis. In this paper, a dynamic analysis method is proposed to investigate the vibration response of the deep groove ball bearings (DGBBs) with local defect using a new displacement excitation function based on the Hertz contact theory and Newton's second law. The DGBB is modeled as a two degrees-of-freedom system, and an additional friction force in the defect zone, the influence of centrifugal force, the gravity of rolling elements, and lubrication traction/slip force between rolling elements and raceway are considered. And this model is used to study the dynamic signals of DGBB under different fault sizes and rotation speeds. Results indicate that the simulation signal has many continuous impacts and change over the time which is closer to the actual situation compared with the one-shot impulse function such as rectangular or half-sine or piecewise function when the rolling elements passed through the defect zone. Finally, the validity of the proposed model is verified by experiments. The simulated and experimental results indicate that the proposed model would achieve a more appropriate and accurate dynamic simulation.