Ламинарный хаос в связанных системах с запаздыванием

The possibility of the existence of laminar chaos in coupled time-delayed feedback systems is investigated. The cases of unidirectional and mutual coupling of time-delay systems are considered. It is shown for the first time that laminar chaos can exist not only in a system with a variable delay time, but also in a system with a constant delay time, if it is coupled with a system in the regime of laminar chaos.

A New Multi-Step Method for Solving Delay Differential Equations using Lagrange Interpolation

This paper presents 2-step p-th order (p = 2,3,4) multi-step methods that are based on the combination of both polynomial and exponential functions for the solution of Delay Differential Equations (DDEs). Furthermore, the delay argument is approximated using the Lagrange interpolation. The local truncation errors and stability polynomials for each order are derived. The Local Grid Search Algorithm (LGSA) is used to determine the stability regions of the method. Moreover, applicability and suitability of the method have been demonstrated by some numerical examples of DDEs with constant delay, time dependent and state dependent delays. The numerical results are compared with the theoretical solution as well as the existing Rational Multi-step Method2 (RMM2).

NON-DESTRUCTIVE INSPECTION BY INFRARED THERMOGRAPHY OF RESISTANCE SPOT WELDS USED IN AUTOMOTIVE INDUSTRY

Resistance spot welding (RSW) is one of the main joining technologies of thin sheets in the automotive industry. Key factors affecting the strength of the RSW joint are the nugget diameter, asymmetry, expulsions, intended surfaces, and the presence of cracks. Despite its broad use, the RSW joint quality verification is limited only to destructive testing and a limited number of non-destructive testing (NDT) methods. Most of the testing is done destructively by sampling, which assesses only systematic defects. Ultrasonic Testing (UT) is the most used NDT method to detect non-systematic defects in the RSW joints, however the probability of the defect detection of conventional testing techniques is not fully satisfactory. Other approaches were invented to deal with this situation. The article uses the currently most used NDT approach of the UT testing as a benchmark to evaluate the ability of thermographic testing to detect defective welds of the resistance spot welding in an on-line mode. The article demonstrates that the infrared thermography may find systematic process errors that are not detectable by other NDT methods by an analysis of different temperature drops measured after a constant delay time caused by different cooling dynamics of satisfactory and non-satisfactory weld joints.

Analysis of Stability Control of a Power System with a Distributed Constant Circuit Model

From the load cut off tests on generators, it is well known that the power disturbance is transmitted from the test point to the other points with constant delay time. The phenomena shows that the electric power system has a similar dynamic characteristic to the distributed constant circuits. In this paper, the electric power system is expressed with the distributed constant circuit, so that the main disturbance characteristics are obtained without difficulty. Moreover, the method of suppressing the plural disturbances is discussed by employing the active sink method.

Experimental confirmation of superposition from small-scale explosions

An in situ experimental program in alluvium is implemented and analyzed to test linear superposition. After separating stochastic and deterministic propagation path effects, direct superposition is experimentally validated at 20 m for two 5-lb charges spaced as close as 2 m in alluvium. The charges are separated by the scaled range of 147 m/kt1/3 and observed at the scaled range of 1470 m/kt1/3. Finite-spatial source effects are observed and simulated in the plane passing through two charges separated by 2 to 10 m. The deterministic single-burst waveforms are used to model the multiple-burst data. The effects observed and simulated include direct superposition below the corner frequency, shift to lower corner frequency with increasing charge separation, and spectral scalloping. For charges closely spaced (up to 4 m, observed at 20 and 24 m), the primary effect on the waveform is replicated by a constant delay time between two identical waveforms. For charges spaced by 10 m (observed at 20 and 30 m), the effects of propagation path differences must be included. These effects result in smoothed spectra.