Comparison between trap and self-heating induced mobility degradation in AlGaN/GaN HEMTs

Mobility degradation due to scattering from radiation-induced defects is compared to that produced by self-heating in proton-irradiated AlGaN/GaN HEMTs using experiments and simulations. After irradiation, the mobility in the 2DEG is limited by scattering from charged traps and is temperature-limited near the gate–drain access region.     

Phase Transition Control for High Performance Ruddlesden–Popper Perovskite Solar Cells

Ruddlesden–Popper reduced‐dimensional hybrid perovskite (RDP) semiconductors have attracted significant attention recently due to their promising stability and excellent optoelectronic properties. Here, the RDP crystallization mechanism in real time from liquid precursors to the solid film is investigated, and how the phase transition kinetics influences phase purity, quantum well orientation, and photovoltaic performance is revealed. An important template‐induced nucleation and growth of the desired (BA)₂(MA)₃Pb₄I₁₃ phase, which is achieved only via direct crystallization without formation of intermediate phases, is observed. As such, the thermodynamically preferred perpendicular crystal orientation and high phase purity are obtained. At low temperature, the formation of intermediate phases, including PbI₂ crystals and solvate complexes, slows down intercalation of ions and increases nucleation barrier, leading to formation of multiple RDP phases and orientation randomness. These insights enable to obtain high quality (BA)₂(MA)₃Pb₄I₁₃ films with preferentially perpendicular quantum well orientation, high phase purity, smooth film surface, and improved optoelectronic properties. The resulting devices exhibit high power conversion efficiency of 12.17%. This work should help guide the perovskite community to better control Ruddlesden–Popper perovskite structure and further improve optoelectronic and solar cell devices.     

Pressure influence on crystallization kinetics during injection molding

This work presents the measurement of the temperature at the center of the cavity during the molding of PP material using an embedded thermocouple probe. The measured temperature curves show a plateau shape related to the crystallization phenomenon. Measurements, done at various pressures show an increase in the crystallization plateau temperature depending on the cavity pressure. The change in the measured crystallization temperature allows the identification of the pressure dependence on the Hoffman-Lauritzen crystallization kinetics parameters: T_m and T_g. The T_m pressure dependence leads to a good agreement with the data of reported studies that used other experimental devices. The obtained results also show a decrease in cavity pressure duration related to the increase in the gate freezing speed as a result of the pressure increase. The identified pressure dependence laws for T_m and T_g introduced in the crystallization kinetics and the thermal model, allow to describe a temperature change in good agreement with the temperature measured down to the crystallization plateau.     

Single- and Two-Layer Coatings of Metal Blends onto Carbon Steel: Mechanical, Wear, and Friction Characterizations

Single- and two-layer coatings were deposited onto carbon steel using a high-velocity oxy-fuel deposition gun. The two-layer coating consisted of a top layer of tungsten carbide cobalt/nickel alloy blend that provides wear resistance and a bottom layer of iron/molybdenum blend that provides corrosion resistance. The morphological changes in the single- and two-layer coatings were examined using scanning electron microscopy. The residual stresses formed on the surface of various coatings were determined from x-ray diffraction data. Nanomechanical properties were measured using the nanoindentation technique. Microhardness and fracture toughness were measured incorporating the microindentation tests. Macrowear and macrofriction characteristics were measured using the pin-on-disk testing apparatus. The goal of this study was to ensure that the mechanical properties, friction, and wear resistance of the two-layer coating are similar to that of the single-layer coating.     

Interface Mutation Test Adequacy Criterion: An Empirical Evaluation

An experiment was conducted to evaluate an inter-procedural test adequacy criterion named Interface Mutation. Program SPACE, developed for the European Space Agency (ESA), was used in this experiment. The development record available for this program was used to find the faults uncovered during its development. Using this information the test process was reproduced starting with a version of SPACE containing several faults and then applying Interface Mutation. Thus we could evaluate the fault revealing effectiveness of Interface Mutation. Results from the experiment suggest that (a) the application of Interface Mutation favors the selection of fault revealing test cases when they exist and (b) Interface Mutation tends to select fault revealing test cases more efficiently than in the case where random selection is used.     

Detecting inappropriate access to electronic health records using collaborative filtering

Many healthcare facilities enforce security on their electronic health records (EHRs) through a corrective mechanism: some staff nominally have almost unrestricted access to the records, but there is a strict ex post facto audit process for inappropriate accesses, i.e., accesses that violate the facility’s security and privacy policies. This process is inefficient, as each suspicious access has to be reviewed by a security expert, and is purely retrospective, as it occurs after damage may have been incurred. This motivates automated approaches based on machine learning using historical data. Previous attempts at such a system have successfully applied supervised learning models to this end, such as SVMs and logistic regression. While providing benefits over manual auditing, these approaches ignore the identity of the users and patients involved in a record access. Therefore, they cannot exploit the fact that a patient whose record was previously involved in a violation has an increased risk of being involved in a future violation. Motivated by this, in this paper, we propose a collaborative filtering inspired approach to predicting inappropriate accesses. Our solution integrates both explicit and latent features for staff and patients, the latter acting as a personalized “fingerprint” based on historical access patterns. The proposed method, when applied to real EHR access data from two tertiary hospitals and a file-access dataset from Amazon, shows not only significantly improved performance compared to existing methods, but also provides insights as to what indicates an inappropriate access.