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[en] Highlights: • Flow patterns in large cylinder arrays are experimentally studied. • Different flow patterns occur after the first row due to lower turbulence levels. • Bistable flows are identified in the array at a given transversal spacing ratio. • Trends are identified for the turbulence energy distribution along the rows. • The last row is at higher risk of vibration due to turbulent buffeting. - Abstract: Studies on flow-induced vibrations in large tube bundles are usually focused solely on frequency analysis, without considering the flow patterns which are responsible for the fluid forces. Furthermore, investigations which involve variations in the spacing ratios do not separate transversal and longitudinal proximity effects. The purpose of this article is to separately analyze the influence of the transversal (T/D) and longitudinal (L/D) spacing ratios of a confined in-line cylinder array with five rows on the flow characteristics and to identify flow patterns. The laser Doppler anemometry technique was employed to acquire the mean velocity and its fluctuations in the transversal and longitudinal directions between the cylinder rows. Strouhal numbers and regimes reported in the literature were identified in the experiments. The same regime did not always persist along all cylinder rows for a given spacing ratio, as a result of the combined longitudinal and transversal proximity effects and also of the generation of turbulence by the array. For the smallest T/D ratio, a quasi-steady behavior associated with the biased flow pattern was noted in the experimental set-up and flip-flopping was observed in one case. Additionally, the flow characteristics in these arrays diverged from tube bundle classifications described in the literature. The behavior of the fluid forces and susceptibility to vibrations in the array were predicted based on the turbulence intensity of the incident flow of the cylinders. The results reinforced the need to extend flow pattern investigations to arrays with more cylinder rows and to consider both transversal and longitudinal proximity effects, when studying flow-induced vibrations.
[en] The original article was published with two typographical errors found in the unit of Y-axis in Figs. 4 and 5 of the original article. The author would like readers to know that the units should be changed from “mm/hr” to “mm/day”. This correction stands to correct the original article.
[en] The purpose of this paper is to investigate components of surface roughness in turning with respect to the tool configuration and the changes of working conditions. Tool configurations of SNMG120404, SNMG120408 and DNMG150404, DNMG150408 are used, and working conditions such as cutting speed 3nd feed are varied. That is, the changes of cutting speed and feed were 150, 200, 250 m/min and 0.05, 0.1, 0.3 mm/rev, respectively. From the results obtained by the frequency analysis with spectrum, it is noted that the surface roughness was influenced most significantly by the feed. It is also observed that the vibration of bite had an effect on both the surface roughness and the surface waviness. Moreover, the influence of surface roughness increases as the feed decreases. Lastly, the vibration of the spindle was found to have little influence on the surface roughness in normal cases and the tool configuration was not the components of the surface roughness
[en] This paper is to analyze the surface roughness in wet and dry surface grinding in which working conditions are table feed, cross feed and down feed. FFT analyzer is used to identify the surface roughness and the data of surface roughness are stored and displayed using an interfaced computer. In results, components affecting surface roughness exist within 200Hz with respect the conditions and methods of grinding operation. Also, with increase of table feed, cross feed and down feed, the value of surface roughness increases. Of them, cross feed has first influence on surface roughness. In dry, more precise surface can be obtained than one in wet
[en] UBV Light Curves of the eclipsing binary system PV Cassiopaiae have been investigated using recently developed frequency-domain techniques. This analysis is based on Kopal's new theory of the study of the light variations, between minima as well as within eclipses, of eclipsing binaries whose components undistorted or distorted by axial rotation and mutual tidal action. A method for the distinguishing of the photometric proximity and eclipse effects directly from the obersved data is also presented. In this method no rectification is needed. The automated method has been tested succesfully on the light curves of PV Cassiopeiae. Finally, a comparative discussion is given of Kopal's and Kitamura's methods of the light curves analysis. (orig.)
[en] We consider some properties of the coordinate sequences of linear recurrences over Galois rings which characterize the possibility of regarding them as pseudo-random sequences. We study the periodicity properties, linear complexity and frequency characteristics of these sequences. Up to now, these parameters have been studied mainly in the case when the linear recurring sequence has maximal possible period. We investigate the coordinate sequences of linear recurrences of not necessarily maximal period. We obtain sharpened and generalized estimates for the number of elements and r-patterns on the cycles and intervals of these sequences
[en] In this article, we introduce vector-valued multiresolution analysis and the biorthogonal vector-valued wavelets with four-scale. The existence of a class of biorthogonal vector-valued wavelets with compact support associated with a pair of biorthogonal vector-valued scaling functions with compact support is discussed. A method for designing a class of biorthogonal compactly supported vector-valued wavelets with four-scale is proposed by virtue of multiresolution analysis and matrix theory. The biorthogonality properties concerning vector-valued wavelet packets are characterized with the aid of time-frequency analysis method and operator theory. Three biorthogonality formulas regarding them are presented.
[en] I present a forward analysis of the rotational frequency splittings of solar p-modes measured by Brown and Morrow to obtain information on the variation of the Sun's angular velocity with depth and co-latitude. This approach entails computing frequency splittings for chosen models of the solar rotation and comparing them to the observed splittings. It is called a forward method to contrast it with inversion techniques, which use the measured frequency splittings directly to produce a single function for the angular velocity. An advantage of the forward approach is that it allows one to develop intuition about the sensitivities of the splitting coefficients to various changes in the nature and magnitude of the angular velocity. The results of the preliminary analysis conducted in Morrow give the impression that models with surface rotation throughout the convection zone are more promising than models with angular velocity constant on cylinders. The more formal approach of this paper is able to substantiate this impression and to consider the splittings from a series of more elaborate models for the solar rotation
[en] Full Text : Vibration spectra of TiInS2 crystals in terahertz areas have been received and analyzed. The observable low-frequency vibration band has been connected with the libration oscillation of the minelayers (boson peak). Connection of coherent low-frequency fluctuation with disorder character of structure of a crystal has been shown. The conclusion about presence of topological disorder which has been shown at level of a layered subsystem becomes
[en] In this paper the existence of the corner frequency value for the seismic moment distribution is investigated, analysing worldwide data. Pareto based distributions, usually considered as the most suitable to this type of data, are fitted to the most recent data, available in a global earthquake catalog. Despite the undeniable finite nature of the seismic moment data, we conclude that no corner frequency can be established considering the available data set