Grain refinement and strength enhancement in Mg wrought alloys: A review

Low absolute strength becomes one major obstacle for the wider applications of low/no rare-earth(RE) containing Mg alloys. This review firstly demonstrates the importance of grain refinement in improving strength of Mg alloys by comprehensively comparing with other strategy, e.g., precipitation strengthening. Dynamic recrystallization(DRX) plays a crucial role in refining grain size of Mg wrought alloys.Therefore, secondly, the DRX models, grain nucleation mechanisms and the related grain refinement abilities in Mg alloys are summarized,including phase boundary, twin boundary and general boundary induced recrystallization. Thirdly, the newly developed low-RE containing Mg alloy, e.g., Mg-Ce, Mg-Nd and Mg-Sm based alloys, and the RE-free Mg alloys, e.g., Mg-Al, Mg-Zn, Mg-Sn and Mg-Ca based alloy,are reviewed, with the focus on enhancing the mechanical properties mainly via the grain refinement strategy. At the last section, the perspectives and outstanding issues concerning high-performance Mg wrought alloys are also proposed. This review is meant to promote the deep understanding on the critical role of grain refinement in Mg alloys and provide reference for the development of other high strength and low-cost Mg alloys which are fabricated by the conventional extrusion/rolling processing.

A Novel Robotic Bronchoscope System for Navigation and Biopsy of Pulmonary Lesions

Transbronchial biopsy sampling,as a minimally invasive method with relatively low risk,has been proved to be a promising treatment in the field of respiratory surgery.Although several robotic bronchoscopes have been developed,it remains a great challenge to balance size and flexibility,while integrating multisensors to realize navigation during complex airway networks.This paper proposes a novel robotic bronchoscope system composed by end effector with relatively small size,relevant actuation unit,and navigation system with path planning and surgical guidance capability.The main part of the end effector is machined by bidirectional groove on a nickel-titanium tube,which can realize bending,rotation,and translation 3 degrees of freedom.A prototype of the proposed robotic bronchoscope system is designed and fabricated,and its performance is tested through several experiments to verify the stiffness,flexibility,and navigation performance.The results show that the proposed system is with good environment adaptiveness,and it can become a promising biopsy method through natural cavity of the human body.

Surgical instruments hyalinization:Occlusion removal in minimally invasive endoscopic surgery

Minimal invasion is an important trend in surgery.However,the endoscope,as one of the key devices for monitoring the process of minimally invasive surgery,is limited by its size and working space it operates in,which result in a considerably narrow field of view.In particular,when a surgical instrument enters through the tool channel,the instrument occupies most of the area in an endoscopic image.This hampers the surgeon’s field of view and has a negative impact on the surgery.This study proposes a novel method for removing the occlusion caused by surgical instruments in endoscopic images by making foreground occlusions on endoscopic images transparent using image restoration and interframe information filling.Compared with unprocessed images,this method can provide a clearer field of view that is necessary for minimally invasive endoscopic surgeries and improve the quality of surgeries.Clinical endoscopic images are used to verify the feasibility of the proposed method,and the results show that the proposed method improves the visual effect of endoscopic images by removing surgical-instrument occlusions.This demonstrates the considerable potential of the proposed method for use in clinical applications.