The effects of friction were observed in electric guitar strings passing over an electric guitar saddle. The effects of changing the ratio of the diameter of the winding to the diameter of the core of the string, the angle through which the string is bent, and the length on either side of the saddle were measured. Relative tensions were deduced by plucking and measuring the frequencies of vibration of the two portions of string. Coefficients of friction consistent with the capstan equation were calculated and were found to be lower than 0.26 for wound strings (nickel plated steel windings on steel cores) and lower than 0.17 for unwound (tin plated steel) strings. The largest values of friction were associated with strings of narrower windings and wider cores and this may be due to the uneven nature of the contact between the string and saddle for wound strings or due the surface of the windings deforming more, encouraging fresh (and therefore higher friction) metal to metal contact. It is advised to apply lubrication under the saddle to string contact point after first bringing the string up to pitch rather than before in order to prevent this fresh metal to metal contact.

The exact measurement of multiphase flow is an important and essential task in the oil and petrochemical related industries. Several methods have already been proposed in this field. In the existing methods, flow rate measurement depends on the fluid flow pattern. Flow pattern recognition requiring calibration has created instability in such systems. In this paper, a imple and reliable method is proposed which is based on ultrasonic tomography. It is free from calibration and instability problems that existing methods have. The obtained data from a 32-digit array of ultrasonic sensors have been used and the two-phase flow rate including liquid and gas phases have been calculated through a simple algebraic algorithm. Simulation results show that while applying this method the measurement technique is independent from the fluid flow pattern and the system error is decreased. For the proposed algorithm, the average amount of the spatial imaging error (SIE) for a bubble at different positions inside the pipe is about 5%.