Effect of Beam Oscillations on Formation of Defects in Electron Beam Welding of Copper Plate

In the present study, electron beam welding bead-on-plate of electrolytic pitched copper (ETP-Cu) plate was carried out to study the behavior of different defects formed in the weld by varying the beam oscillation amplitudes. The defects like spattering, spiking and porosity were considered in this study. Spattering and spiking phenomena were determined with visual inspection and image analysis software, respectively. Porosity measurement was conducted with X-ray tomography. Spattering was found to decrease with the oscillation amplitude up to the optimized value and then, it showed an increasing effect with it. Spatters in the weld also contributed to the pore formation in the weld by the inside pores available in it. Spiking was found to be more dynamic, and not directly related to the oscillation amplitude. But, in general, it was increasing with the increase of amplitude. Spiking was found to have a linear relationship with mean diameter of pores, which implied that a weld with the sharper spikes was more prone to large size root pores in the weld. Mean diameter and volume fraction of the pores were tending to increase with oscillation amplitude; however, there were discontinuities in the trend at the optimized amplitude value. An optimized value of oscillation amplitude was found to be useful for suppressing these defects in the weld. However, a random oscillation amplitude could be more detrimental to the quality of the weld joint.

Ring oscillator physically unclonable function using sequential ring oscillator pairs for more challenge-response-pairs

<span>The ring oscillator physically unclonable function (ROPUF) is one of the several types of PUF that has great potential to be used for security purposes. An alternative ROPUF design is proposed with two major differences. Firstly, the memristor is included in the ring oscillators as it is claimed to produce a more random oscillation frequency. Other reasons are its memory-like properties and variable memristance, relative compatibility with CMOS, and small size. Secondly, a different method of generating the response is implemented whereby a sequence of selection of ring oscillator pairs are used to generate a multiple bit response, rather than using only one ring oscillator pair to generate a single bit response. This method significantly expands the set of challenge-response pairs. The proposed memristor-based ROPUF shows 48.57%, 51.43%, and 51.43% for uniqueness, uniformity, and bit-aliasing, respectively. Also, modelling by support vector machine (SVM) on the proposed memristor-based ROPUF only shows 61.95% accuracy, thereby indicating strong resistance against SVM.</span>

ON THE TRANSCENDENCE OF SOME INFINITE SERIES

The paper deals with a criterion for the sum of a special series to be a transcendental number. The result does not make use of divisibility properties or any kind of equation and depends only on the random oscillation of convergence.

Random oscillation in systems subject to the excitation of a class of coloured noises

In the paper the higher order stochastic averaging method is developed to a class of colored noise excitations when the corresponding forming filter has only finite negative eigenvalues. The second approximate probability density function to the Duffing system subject to the exponentially correlated process is obtained. Numerical application is carried out to investigate the independence of mean square amp1itude on the bandwidth parameter.