Reflection of a longitudinal travelling wave from the notch in a rod

2007 ◽  
Vol 5 ◽  
pp. 212-220 ◽  
Author(s):  
M.A. Ilgamov ◽  
A.G. Khakimov
Keyword(s):  
Inverse Problem ◽  
Longitudinal Wave ◽  
Travelling Wave ◽  
Observation Point ◽  
Reflected Waves ◽  
Reflected Wave ◽  
Using Data

This article investigates the reflection of a longitudinal wave from the transverse notch and its movement along an infinite rod. The dependence is obtained between the reflected wave and parameters of the notch. The statement of the inverse problem allows defining the coordinate of the notch and the parameter that contains its depth and length using data on both the incident and reflected waves at the observation point.

Reflection of a longitudinal travelling wave from the notch in a rod plunged into viscous liquid

2010 ◽  
Vol 7 ◽  
pp. 129-142
Author(s):  
M.A. Ilgamov ◽  
A.G. Khakimov
Keyword(s):  
Inverse Problem ◽  
Viscous Liquid ◽  
Travelling Wave ◽  
Observation Point ◽  
Reflected Waves ◽  
Damping Characteristics ◽  
Deformed State ◽  
Using Data ◽  
Surrounding Liquid

The article investigates the reflection of a longitudinal damped travelling wave from the transverse notch and its movement along an infinite rod plunged into viscous liquid. The simplest model for the stress deformed state in the notch zone is applied. The solution is found to depend on the parameters of the liquid and damping characteristics in the material of the rod and the surrounding liquid. The solution to the inverse problem makes it possible to define the coordinate of the notch and the parameter that contains its depth and length using data on both the incident and reflected waves at the observation point.

Reflection of a short bending travelling wave from distributed mass attached to a pipeline

2012 ◽  
Vol 9 (2) ◽  
pp. 134-138 ◽  
Author(s):  
A.G. Khakimov
Keyword(s):  
Inverse Problem ◽  
Travelling Wave ◽  
Observation Point ◽  
Reflected Wave

Consideration is given to the reflection of distributed mass attached to a pipeline and the movement of a short bending travelling wave. The solution is shown to depend on the initial coordinate of the distributed mass and its magnitude. The solution to the inverse problem makes it possible to define the initial coordinate of the distributed mass and its magnitude using the data on the reflected wave at the observation point.

Towards Behaviour Recognition with Unlabelled Sensor Data

2013 ◽  
pp. 86-110
Author(s):  
Sook-Ling Chua ◽  
Stephen Marsland ◽  
Hans W. Guesgen
Keyword(s):  
Machine Learning ◽  
Data Mining ◽  
Inverse Problem ◽  
Sensor Data ◽  
Training Set ◽  
Learning Methods ◽  
Machine Learning Methods ◽  
Using Data ◽  
Symbolic Approach ◽  
Behaviour Recognition

The problem of behaviour recognition based on data from sensors is essentially an inverse problem: given a set of sensor observations, identify the sequence of behaviours that gave rise to them. In a smart home, the behaviours are likely to be the standard human behaviours of living, and the observations will depend upon the sensors that the house is equipped with. There are two main approaches to identifying behaviours from the sensor stream. One is to use a symbolic approach, which explicitly models the recognition process. Another is to use a sub-symbolic approach to behaviour recognition, which is the focus in this chapter, using data mining and machine learning methods. While there have been many machine learning methods of identifying behaviours from the sensor stream, they have generally relied upon a labelled dataset, where a person has manually identified their behaviour at each time. This is particularly tedious to do, resulting in relatively small datasets, and is also prone to significant errors as people do not pinpoint the end of one behaviour and commencement of the next correctly. In this chapter, the authors consider methods to deal with unlabelled sensor data for behaviour recognition, and investigate their use. They then consider whether they are best used in isolation, or should be used as preprocessing to provide a training set for a supervised method.

Arterial waves in humans during peripheral vascular surgery

2001 ◽  
Vol 101 (6) ◽  
pp. 749-757 ◽  
Author(s):  
Ashraf W. KHIR ◽  
Michael Y. HENEIN ◽  
Tat KOH ◽  
Saroj K. DAS ◽  
Kim H. PARKER ◽  
...  
Keyword(s):  
Vascular Surgery ◽  
Wave Speed ◽  
Lv Function ◽  
Peripheral Vascular ◽  
Reflected Waves ◽  
Peripheral Vascular Surgery ◽  
Aortic Clamping ◽  
Compression Waves ◽  
Reflected Wave ◽  
Catheter Tip

The purpose of this study was to investigate the effect of aortic clamping on arterial waves during peripheral vascular surgery. We measured pressure and velocity simultaneously in the ascending aorta, in ten patients (70±5 years) with aortic-iliac disease intra-operatively. Pressure was measured using a catheter tip manometer, and velocity was measured using Doppler ultrasound. Data were collected before aortic clamping, during aortic clamping and after unclamping. Hydraulic work in the aortic root was calculated from the measured data, the reflected waves were determined by wave-intensity analysis and wave speed was determined by the PU-loop (pressure-velocity-loop) method; a new technique based on the ‘water-hammer’ equation. The wave speed is approx. 32% (P < 0.05) higher during clamping than before clamping. Although the peak intensity of the reflected wave does not alter with clamping, it arrives 30ms (P < 0.05) earlier and its duration is 25% (P < 0.05) longer than before clamping. During clamping, left ventricule (LV) hydraulic systolic work and the energy carried by the reflected wave increased by 27% (P < 0.05) and 20% (P < 0.05) respectively, compared with before clamping. The higher wave speed during clamping explains the earlier arrival of the reflected waves suggesting an increase in the afterload, since the LV has to overcome earlier reflected compression waves. The longer duration of the reflected wave during clamping is associated with an increase in the total energy carried by the wave, which causes an increase in hydraulic work. Increased hydraulic work during clamping may increase LV oxygen consumption, provoke myocardial ischaemia and hence contribute to the intra-operative impairment of LV function known in patients with peripheral vascular disease.

Ultrasound Tomography Imaging of Defects Using Neural Networks

1992 ◽  
Vol 4 (5) ◽  
pp. 758-771 ◽  
Author(s):  
Denis M. Anthony ◽  
Evor L. Hines ◽  
David A. Hutchins ◽  
J. T. Mottram
Keyword(s):  
Neural Networks ◽  
Inverse Problem ◽  
Artificial Neural Networks ◽  
Longitudinal Wave ◽  
Time Of Flight ◽  
Simplified Model ◽  
Gray Scale ◽  
Ultrasound Tomography ◽  
Tomography Imaging ◽  
Ultrasound Propagation

Simulations of ultrasound tomography demonstrated that artificial neural networks can solve the inverse problem in ultrasound tomography. A highly simplified model of ultrasound propagation was constructed, taking no account of refraction or diffraction, and using only longitudinal wave time of flight (TOF). TOF data were used as the network inputs, and the target outputs were the expected pixel maps, showing defects (gray scale coded) according to the velocity of the wave in the defect. The effects of varying resolution and defect velocity were explored. It was found that defects could be imaged using time of flight of ultrasonic rays.

scholarly journals Probabilistic forecasting of plausible debris flows from Nevado de Colima (México) using data from the Atenquique debris flow, 1955

2018 ◽  
Author(s):  
Andrea Bevilacqua ◽  
Abani K. Patra ◽  
Marcus I. Bursik ◽  
E. Bruce Pitman ◽  
José Luis Macías ◽  
...  
Keyword(s):  
Inverse Problem ◽  
Debris Flow ◽  
Hazard Assessment ◽  
Hazard Analysis ◽  
Multiple Models ◽  
Probabilistic Forecasting ◽  
Flow Models ◽  
Using Data ◽  
Averaged Models ◽  
The Impact

Abstract. We detail a new prediction-oriented procedure aimed at volcanic hazard assessment based on geophysical mass flow models constrained with heterogeneous and poorly defined data. Our method relies on an itemized application of the empirical falsification principle over an arbitrarily wide envelope of possible input conditions. We thus provide a first step towards a objective and partially automated experimental design construction. In particular, instead of fully calibrating model inputs on past observations, we create and explore more general requirements of consistency, and then we separately use each piece of empirical data to remove those input values that are not compatible with it, hence defining partial solutions to the inverse problem. This has several advantages compared to a traditionally posed inverse problem: (i) the potentially non-empty inverse images of partial solutions of multiple possible forward models characterize the solutions to the inverse problem; (ii) the partial solutions can provide hazard estimates under weaker constraints, potentially including extreme cases that are important for hazard analysis; (iii) if multiple models are applicable, specific performance scores against each piece of empirical information can be calculated. We apply our procedure to the case study of the Atenquique volcaniclastic debris flow, which occurred on the flanks of Nevado de Colima volcano (México), 1955. We adopt and compare three depth averaged models currently implemented in the TITAN2D solver, available from vhub.org. The associated inverse problem is not well-posed if approached in a traditional way. We show that our procedure can extract valuable information for hazard assessment, allowing the exploration of the impact of synthetic flows similar to those that occurred in the past, but different in plausible ways. The implementation of multiple models is thus a crucial aspect of our approach, as they can allow the covering of other plausible flows. We also observe that model selection is inherently linked to the inversion problem.

Review of studies on the computational diagnosis of local defects of structural elements

2019 ◽  
Vol 14 (1) ◽  
pp. 1-9
Author(s):  
A.G. Khakimov
Keyword(s):  
Inverse Problem ◽  
Traveling Wave ◽  
Unit Length ◽  
Central Area ◽  
Relative Mass ◽  
Torsional Vibrations ◽  
Observation Site ◽  
Air Cavity ◽  
Reflected Wave ◽  
Local Defects

Rods, beams, shafts, pipelines, round plates. membranes are parts of structures in which local defects such as cracks, dents, cavities, local corrosion can be formed. Provides an overview of the research A. G. Khakimov for the diagnosis of local defects. It is received: 1. The two eigenfrequencies of the longitudinal oscillations can determine the location and the notch parameter characterizing its size. 2. The three lower eigenfrequencies of the longitudinal oscillations can determine the initial coordinate and the value of the attached distributed mass to the stepped rod, as well as the ratio of the areas. 3. The solution of the inverse problem for extended rods allows us to determine the coordinate of the incision and the parameter containing its depth and length, according to the incident and reflected waves at the observation site. 4. The reflection from the air cavity and the passage of a longitudinal damped traveling wave in a pipeline immersed in a viscous liquid are determined, and the solution of the inverse problem allows to determine the coordinate of the air cavity and its length according to the reflected wave at the observation site. 5. The initial coordinate and the length of the longitudinal through radial section of the hollow shaft are determined by the two eigenfrequencies of torsional vibrations. 6. The coordinate, length and parameter of the drill string notch are determined by the three eigenfrequencies of the torsional vibrations. 7. The reflection from the distributed mass attached to the pipeline and the passage of the flexural traveling wave are considered. The dependence of the solution on the initial coordinate of the distributed mass and its magnitude is obtained, and the inverse problem of determining the initial coordinate of the distributed mass and its magnitude from the data of the reflected wave at the observation point is solved. 8. The radius and thickness of the thin central region of the membrane are determined by the two eigenfrequencies of the transverse vibrations. 9. The radius, thickness of the thinned central area of the plate and the value of the attached distributed mass are determined by the three natural frequencies of the bending oscillations. 10. By three frequencies of bending vibrations it is possible to determine the velocity parameter, the relative mass of the product per unit length of the pipeline and the relative mass of sediments on the walls of the pipeline and, as a consequence, the mass flow of liquid through the pipeline.

Joint wave-equation traveltime inversion of diving/direct and reflected waves for the P- and S-wave velocity macromodel building

Geophysics ◽  
2021 ◽  
pp. 1-145
Author(s):  
Zhiming Ren ◽  
Qianzong Bao ◽  
Bingluo Gu
Keyword(s):  
Wave Velocity ◽  
Velocity Model ◽  
S Wave ◽  
Direct Wave ◽  
Reflected Waves ◽  
Traveltime Inversion ◽  
Long Wavelength ◽  
Velocity Models ◽  
Reflected Wave ◽  
Background Models

Full waveform inversion (FWI) suffers from the local minima problem and requires a sufficiently accurate starting model to converge to the correct solution. Wave-equation traveltime inversion (WETI) is an effective tool to retrieve the long-wavelength components of the velocity model. We develop a joint diving/direct and reflected wave WETI (JDRWETI) method to build the P- and S-wave velocity macromodels. We estimate the traveltime shifts of seismic events (diving/direct waves, PP and PS reflections) through the dynamic warping scheme and construct a misfit function using both the time shifts of diving/direct and reflected waves. We derive the adjoint wave equations and the gradients with respect to the background models based on the joint misfit function. We apply the kernel decomposition scheme to extract the kernel of the diving/direct wave and the tomography kernels of PP and PS reflections. For an explosive source, the kernels of diving/direct wave and PP reflections and the kernel of PS reflections are used to compute the P- and S-wave gradients of the background models, respectively. We implement JDRWETI by a two-stage inversion workflow: first invert the P- and S-wave velocity models using the P-wave gradients and then improve the S-wave velocity model using the S-wave gradients. Numerical tests on synthetic and field datasets reveal that the JDRWETI method successfully recovers the long-wavelength components of P- and S-wave velocity models, which can be used for an initial model for the subsequent elastic FWI. Moreover, the proposed JDRWETI method prevails over the existing reflection WETI method and the cascaded diving/direct and reflected wave WETI method, especially when large velocity errors are present in the shallow part of the starting models. The JDRWETI method with the two-stage inversion workflow can give rise to reasonable inversion results even for the model with different P- and S-wave velocity structures.

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