In this paper, a wave propagation model is developed to investigate the wave propagation in fluid-filled steel pipe. Based on the Kennard shell equations the investigation is achieved under the conditions of coupling between the shell elastic acoustic field and the interior fluid acoustic field. Tests are conducted on fluid-filled pipeline blockage detection. An active acoustic source is used t...

The Wigner distribution (WD) is perhaps the most prominent quadratic time–frequency signal representation. In this paper, which has mainly tutorial character but also contains some new results, we describe extensions of the WD concept to multidimensional vector signals, nonstationary random processes, linear time-varying systems (deterministic and random), linear signal spaces, and frames. We d...

This work deals with the analysis of chirp signals by means of time-frequency representation. We propose a chirp adapted time-frequency representation (CA) in which the interferences are significantly reduced. This method is applied to the analysis of acoustic echoes of a sphere target. Comparison of the results to other types of time-frequency distribution of the Cohen’s class shows that the i...

In the present study, the effects of arrangement and distribution of multifarious types of defects on fundamental frequency of carbon nanotubes are investigated with respect to different chirality and boundary conditions. Interatomic interactions between each pair of carbon atoms are modeled using two types of non–linear spring–like elements. To obtain more information about the influences of d...

the aim of the present study was the conducting of comparative analysis of allele pool of ukrainian population of thoroughbred horses and the populations from england, usa, russia and south korea using microsatellite loci of dna on the basis of our own researches and literary sources. comparative analysis of allele pool of thoroughbred populations from different countries was conducted using 6 ...

bilingual dictionary use in l2 writing test performance has recently been the subject of debate. opinions differ according to how the trait is understood and whether the system favors the process-oriented or product-oriented views towards the assessment and writing skill. given the need for more empirical support, this study is aimed at investigating the availability of bilingual dictionary use...

This paper reviews the present methods of distributing standard frequency and time signals (SFTS), which include the use of high-frequency, low-frequency, and very-low-frequency radio signals, portable clocks, satellites, and RF cables and Lines. The range of accuracies attained with most of these systems is included along with an indication of the sources of error. Information is also included...