Microstructure and anti-corrosion performance of laser cladded Nb-modified Ni-based alloy coatings

In this work, Ni-based alloy coatings incorporated with Nb mass fractions of 0%, 3%, 6%, and 9% were successfully fabricated by laser cladding. The morphology, chemical composition, and phases of the obtained Nb-modified Ni-based coatings were characterized, and the effects of Nb contents on their electrochemical performance and immersion rates in 3.5 wt% NaCl solution were analyzed. The results show that the Ni-based coating with low Nb exhibits the most compact and refined microstructure, the best electrochemical passivation, and the lowest immersion corrosion rate of 3.30 × 10−3 mm/year. However, with increasing Nb content, the Laves phase is accumulated, and dendritic growth is promoted, which significantly decreases the coating passive stability and worsens the anti-corrosion performance.

Application of a self-injection locked cyan laser for Barium ion cooling and spectroscopy

Compact, high power lasers with narrow linewidth are important tools for the manipulation of quantum systems. We demonstrate a compact, self-injection locked, Fabry-Perot semiconductor laser diode with high output power at 493 nm. A high quality factor magnesium fluoride whispering gallery mode resonator enables both high passive stability and 1 kHz instantaneous linewidth. We use this laser for laser-cooling, in-situ isotope purifcation, and probing barium atomic ions confined in a radio-frequency ion trap. The results here demonstrate the suitability of these lasers in trapped ion quantum information processing and for probing weak coherent optical transitions.

Mini-Invasive Extraarticular Stabilization of the Cranial Cruciate Deficient Stifle in Dogs

The purpose of this work was to describe three mini-invasive techniques for extraarticular stabilization of the deficient stifle based of bone anchores inserted in quasi-isometric sites.Suture stabilization of the stifle consisted of placing a monofilament nylon leader line or polyethylene suture between femoral site adjacent to the distal poles of the fabella, and tibial site immediately cranial to the long digital extensor tendon, using two anchor types. Each stifle was tested (cranial drawer test and tibial compression test) before and after arthroscopic transection of the cranial cruciate ligament and after performing the assigned procedure. Surgical approach, order of procedural steps, drill hole entrance and exit points, and techniques for anchors placement, tensioning, and securing were described.The results of the cranial drawer test and tibial compression test do not show statistically significant differences between the three applied techniques. All three techniques provide passive stability to the deficient stifle.

Passive stability enhancement with sails of a hovering flapping twin-wing robot

Hovering flapping wing flight is intrinsically unstable in most cases and requires active flight stabilization mechanisms. This paper explores the passive stability enhancement with the addition of top and bottom sails, and the capability to predict the stability from a very simple model decoupling the roll and pitch axes. The various parameters involved in the dynamical model are evaluated from experiments. One of the findings is that the damping coefficient of a bottom sail (located in the flow induced by the flapping wings) is significantly larger than that of a top sail. Flight experiments have been conducted on a flapping wing robot of the size of a hummingbird with sails of various sizes and the observations regarding the flight stability correlate quite well with the predictions of the dynamical model. Twelve out of 13 flight experiments are in agreement with stability predictions.

Wing morphing allows gulls to modulate static pitch stability during gliding

A gliding bird's ability to stabilize its flight path is as critical as its ability to produce sufficient lift. In flight, birds often morph the shape of their wings, but the consequences of avian wing morphing on flight stability are not well understood. Here, we investigate how morphing the gull elbow joint in gliding flight affects their static pitch stability. First, we combined observations of freely gliding gulls and measurements from gull wing cadavers to identify the wing configurations used during gliding flight. These measurements revealed that, as wind speed and gusts increased, gulls flexed their elbows to adopt wing shapes characterized by increased spanwise camber. To determine the static pitch stability characteristics of these wing shapes, we prepared gull wings over the anatomical elbow range and measured the developed pitching moments in a wind tunnel. Wings prepared with extended elbow angles had low spanwise camber and high passive stability, meaning that mild perturbations could be negated without active control. Wings with flexed elbow angles had increased spanwise camber and reduced static pitch stability. Collectively, these results demonstrate that gliding gulls can transition across a broad range of static pitch stability characteristics using the motion of a single joint angle.