Concurrent Formation of Metallic Glass During Laser Forward Transfer 3D Printing

In recent years, bulk metallic glasses (BMGs) have drawn much research attention and are shown to be of industrial interest due to their superior mechanical properties and resistance to corrosion. In spite of the interest in harnessing MG for microelectromechanical systems devices, there are limitations in manufacturing such micrometer‐scale structures. A novel approach for the fabrication of 3D MG structures using laser‐induced forward transfer (LIFT) is demonstrated. Inherent tremendous cooling rates associated with the metal LIFT process (≈10¹⁰ k s^?1) make the formation of a variety of BMGs accessible, including also various binary compositions. In this work, it is demonstrated that LIFT printing of ZrPd‐based metallic glass microstructures can also be performed under ambient conditions. X‐ray diffraction analysis of the printed structures reveals > 95% of amorphous metal phase. Taking advantage of the properties of BMG, high quality printing of high aspect ratio BMG pillars, and microbridges are demonstrated. It is also shown how a composite, amorphous‐crystalline metal structure with a required configuration can be fabricated using multimaterial LIFT printing. The inherent high resolution of the method combined with the noncontact and multimaterial printing capacity makes LIFT a valuable additive manufacturing technique to produce metallic glass‐based devices.     

Application of spectral features’ ratios for improving classification in partially calibrated hyperspectral imagery: a case study of separating Mediterranean vegetation species

Efficient real-time discrimination of image objects is greatly affected by their radiometry, which is only partly accounted for by image scene calibration. Such calibration treats mainly variations in flux density in the generalized imaged scene plane rather than on the objects’ surface. The proposed methodology uses ratios between secondary parameterizations: e.g., absorption features and spectral derivatives. Clustering in the ratios’ parameter space may allow differentiation between image objects despite limitations regarding their relative calibration. The usefulness of this approach was demonstrated in the challenging task of separating Mediterranean vegetation species using imaging spectroscopy.     

75 m/s simulation and experiment of two-stage reluctance coilgun

Magnetic launchers are divided into three main techniques, with one of them being the reluctance coilgun. The projectile in this method is rather simple and the obtained velocity is relatively low, which is its main disadvantage. Also, theoretical simulations for high velocity usually predict much higher velocities than that of the experiments. The aim of this work is to demonstrate an accurate simulation of a two-stage coilgun and show experimental validation of high launching velocity. A two-stage coilgun was designed and optimized by numerical simulations. Accordingly, it was implemented and tested experimentally. As an outcome, the highest reported velocity of 75 m/s was obtained both in the simulation and experiment. This outcome contributes to the understanding that adding stages can increase the launching velocity by carefull implementation of the initial position of the projectile, together with proper timing of the second stage. It is concluded that with this approach a multi-stage coilgun can reach even higher velocity.