Review of user parameter-free robust adaptive beamforming algorithms

This paper provides a comprehensive review of user parameter-free robust adaptive beamforming algorithms. We present the ridge regression Capon beamformers (RRCBs), the mid-way (MW) algorithm, and the convex combination (CC) as well as the general linear combination (GLC) approaches. The purpose of these methods is to mitigate the effect of small sample size and steering vector errors on the standard Capon beamformer (SCB). We also present sparsity based iterative beamforming algorithms, namely the iterative adaptive approach (IAA), maximum likelihood based IAA (referred to as IAA-ML) and M-SBL (multi-snapshot sparse Bayesian learning), which exploit sparsity to estimate the signal parameters. We provide a thorough evaluation of these beamforming methods in terms of power and spatial spectrum estimation accuracies, output signal-to-interference-plus-noise ratio (SINR) and resolution under various scenarios including coherent, non-coherent and distributed sources, steering vector mismatches, snapshot limitations and low signal-to-noise ratio (SNR) levels. Furthermore, we discuss the computational complexities of the algorithms and provide insights into which algorithm is the best choice under which circumstances.     

The room temperature annealing kinetics of stacking faults in cold worked alpha brasses

The room temperature annealing kinetics of stacking faults in cold worked alpha brasses were investigated by an X-ray diffraction technique. It was observed that the stacking fault probability in Cu-10 Zn alloy increases as a logarithmic function of time. This phenomena is associated with the segregation of zinc atoms to stacking faults. The ther mo mechanically treated (CW at RT, +720 h at RT, +18 h at 423 K and WQ) Cu-10 Zn alloy and also the Cu-20 Zn alloy showed an “abnormal narrowing” of stacking faults at room temperature. In order to explain this behavior, it was postulated that the partial dislocations relax under the action of the depleted area left behind them. In the Cu-30 Zn alloy the stacking fault probability showed a logarithmic decrease with respect to annealing time. This was interpreted as the relaxation of partial dislocations into their minimum energy configuration under the uniform solute impedance effect. A thermodynamic treatment of segregation to stacking faults was advanced for real multi-component solid solutions. The segregation of zinc atoms to the stacking faults in alpha brasses was calculated as a function of composition at room temperature using an IBM-360 computer. It was found that the maximum segregation to the stacking faults occurs in the Cu-6 Zn alloy.     

The room temperature annealing kinetics of stacking faults in cold worked alpha brasses

The room temperature annealing kinetics of stacking faults in cold worked alpha brasses were investigated by an X-ray diffraction technique. It was observed that the stacking fault probability in Cu-10 Zn alloy increases as a logarithmic function of time. This phenomena is associated with the segregation of zinc atoms to stacking faults. The ther mo mechanically treated (CW at RT, +720 h at RT, +18 h at 423 K and WQ) Cu-10 Zn alloy and also the Cu-20 Zn alloy showed an “abnormal narrowing” of stacking faults at room temperature. In order to explain this behavior, it was postulated that the partial dislocations relax under the action of the depleted area left behind them. In the Cu-30 Zn alloy the stacking fault probability showed a logarithmic decrease with respect to annealing time. This was interpreted as the relaxation of partial dislocations into their minimum energy configuration under the uniform solute impedance effect. A thermodynamic treatment of segregation to stacking faults was advanced for real multi-component solid solutions. The segregation of zinc atoms to the stacking faults in alpha brasses was calculated as a function of composition at room temperature using an IBM-360 computer. It was found that the maximum segregation to the stacking faults occurs in the Cu-6 Zn alloy.     

Stimuli-accelerated polymeric drug delivery systems

The controlled delivery of active pharmaceutical ingredients to the site of disease represents a major challenge in drug therapy. Particularly when drugs have to be transported across biological barriers, suitable drug delivery systems are of importance. In recent years responsive delivery systems have been developed which enable a controlled drug release depending on internal or external stimuli such as changes in pH, redox environment or light and temperature. In some studies delivery systems with reactivity against two different stimuli were established either to enhance the response by synergies of the stimuli or to broaden the window of possible trigger events. In the present review numerous exciting developments of pH-, light- and redox-cleavable polymers suitable for the preparation of smart delivery systems are described. The review discusses the different stimuli that can be used for a controlled drug release of polymer-based delivery systems. It puts a focus on the different polymers described for the preparation of stimuli-sensitive systems, their preparation techniques as well as their stimuli-responsive degradation. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.     

Dynamic bond exchangeable thermoset vitrimers in 3D-printing

Dynamic bond exchanging vitrimers have emerged recently due to their malleability, self-heal ability, recyclability, and mechanical stability. Likewise, 3D printing is consciously introduced at different platforms for ease of fabrication, high throughput, cost-effectiveness, and waste reduction. These two distinctive techniques have recently made their consensus performance, resulting from a phenomenal change in the printing field. Conventionally, thermoplastic inks have been primarily used in 3D printing, owing to their effortless processability. At the same time, thermosets were utilized for their superior mechanical strength. However, these two essential properties have been required to be presented in the printed material. In that scenario, thermoset vitrimer materials have been introduced in 3D printing, where malleability and mechanical stability have been observed in the same material. Thus, this article details the recent vitrimer material included with the different 3D printing system systems with their reported results to understand and make them widespread. Eventually, the outlook and perspectives could be helpful to understand and enhance this specific field.