[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] 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] The present paper addresses developing the Dynamic Stiffness Method (DSM) for natural frequency analysis of functionally graded beam with piezoelectric patch based on the Timoshenko beam theory and power law of material grading. Governing equations and general solution of free vibration are conducted for the beam element with piezoelectric layer that is modelled as a homogeneous Timoshenko beam. The obtained solution allows establishing dynamic stiffness matrix for modal analysis of FGM beam with bonded piezoelectric distributed sensors/actuators. Effect of thickness and position of the smart sensors/actuators and material parameters on natural frequencies is studied with the aim for dynamic testing and health monitoring of FGM structures. The theoretical developments are validated and illustrated by numerical examples. (paper)

[en] We performed word frequency analysis of the mechanics portion of an algebra-based introductory physics text. We identified about 400 physics and auxiliary words that constitute the core vocabulary of this subject. We present and discuss our findings especially as they inform physics instruction and communication in English, indigenous, and sign languages. This includes the Hawaiian language, our initial motivation for undertaking this work. (paper)

[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] The present paper addresses the problem of free vibration in multiple cracked beams made of functionally graded material (FGM). Governing equations of the beam vibration are established using the Timoshenko beam theory, power law of material grading along the beam thickness and rotational spring model of crack. The actual position of neutral plane differed from the mid-plane due to the material properties variation is also taken into account. The frequency equation obtained in a simple form provides an efficient tool for natural frequency analysis and may also be used for solving the inverse problems such as identification of material properties or cracks in the beams from natural frequencies. Numerical examples have been carried out to validate the proposed theory and to investigate the effect of cracks, material and geometry parameters on natural frequencies of the beams.

[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] Wavelet analysis is a localized time-frequency analysis method,it uses the combination of time domain and frequency domain to show the characteristics of a signal. In this paper uses the wavelet analysis to decompose the vibration signal in different frequency band. And we can get the energy of the signal in different frequency band and the vibration characteristics of the slab by decomposing different frequencies and the different scales of the signal analysis at the different frequency band. According to the signal noise sigma, doing the wavelet threshold noise reduction uses the general threshold, the threshold set by Birge-Massart strategy, the threshold set by penalty strategy and the strategy of the threshold to estimate sample signal, then gets the best scheme. (paper)