Influence of Vanadium Microalloying on Microstructure and Property of Laser-Cladded Martensitic Stainless Steel Coating.

Martensitic stainless steel (MSS) coatings with different vanadium (V) contents (0-1.0 wt%) by microalloying have been successfully fabricated utilizing a unique laser cladding technique. The microstructure and properties of the resulting MSS coatings, with and without element V addition, have been carefully investigated by various advanced techniques, including XRD, SEM, TEM, microhardness tester, universal material testing machine, and electrochemical workstation. It was found that the V-free coating was mainly composed of martensite (M) and ferrite (F), trace M23C6 and M2N, while the V-bearing coatings consisted of M, F, M23C6, and VN nano-precipitates, and their number density increased with the increase of V content. The V microalloying can produce a significant impact on the mechanical properties of the resulting MSS laser-cladded specimens. As the V content increased, the elongation of the specimen increased, while the tensile strength and microhardness increased firstly and then decreased. Specifically, the striking comprehensive performance can be optimized by microalloying 0.5 wt% V in the MSS coating, with microhardness, tensile strength, yield strength, and elongation of 500.1 HV, 1756 MPa, 1375 MPa, and 11.9%, respectively. However, the corrosion resistance of the specimens decreased successively with increasing V content. The microstructure mechanisms accounting for the property changes have been discussed in detail.

A New Filtering System for Using a Consumer Depth Camera at Close Range.

Using consumer depth cameras at close range yields a higher surface resolution of the object, but this makes more serious noises. This form of noise tends to be located at or on the edge of the realistic surface over a large area, which is an obstacle for real-time applications that do not rely on point cloud post-processing. In order to fill this gap, by analyzing the noise region based on position and shape, we proposed a composite filtering system for using consumer depth cameras at close range. The system consists of three main modules that are used to eliminate different types of noise areas. Taking the human hand depth image as an example, the proposed filtering system can eliminate most of the noise areas. All algorithms in the system are not based on window smoothing and are accelerated by the GPU. By using Kinect v2 and SR300, a large number of contrast experiments show that the system can get good results and has extremely high real-time performance, which can be used as a pre-step for real-time human-computer interaction, real-time 3D reconstruction, and further filtering.

Face validation of the Virtual Electrosurgery Skill Trainer (VEST©).

BACKGROUND: Electrosurgery is a modality that is widely used in surgery, whose use has resulted in injuries, OR fires and even death. The SAGES has established the FUSE program to address the knowledge gap in the proper and safe usage of electrosurgical devices. Complementing it, we have developed the Virtual Electrosurgery Skill Trainer (VEST(©)), which is designed to train subjects in both cognitive and motor skills necessary to safely operate electrosurgical devices. The objective of this study is to asses the face validity of the VEST(©) simulator. METHODS: Sixty-three subjects were recruited at the 2014 SAGES Learning Center. They all completed the monopolar electrosurgery module on the VEST(©) simulator. At the end of the study, subjects assessed the face validity with questions that were scored on a 5-point Likert scale. RESULTS: The subjects were divided into two groups; FUSE experience (n = 15) and no FUSE experience (n = 48). The median score for both the groups was 4 or higher on all questions and 5 on questions on effectiveness of VEST(©) in aiding learning electrosurgery fundamentals. Questions on using the simulator in their own skills lab and recommending it to their peers also scored at 5. Mann-Whitney U test showed no significant difference (p > 0.05) indicating a general agreement. 46% of the respondents preferred VEST compared with 52% who preferred animal model and 2% preferred both for training in electrosurgery. CONCLUSION: This study demonstrated the face validity of the VEST(©) simulator. High scores showed that the simulator was visually realistic and reproduced lifelike tissue effects and the features were adequate enough to provide high realism. The self-learning instructional material was also found to be very useful in learning the fundamentals of electrosurgery. Adding more modules would increase the applicability of the VEST(©) simulator.

Face and construct validation of a next generation virtual reality (Gen2-VR) surgical simulator.

INTRODUCTION: Surgical performance is affected by distractors and interruptions to surgical workflow that exist in the operating room. However, traditional surgical simulators are used to train surgeons in a skills laboratory that does not recreate these conditions. To overcome this limitation, we have developed a novel, immersive virtual reality (Gen2-VR) system to train surgeons in these environments. This study was to establish face and construct validity of our system. METHODS AND PROCEDURES: The study was a within-subjects design, with subjects repeating a virtual peg transfer task under three different conditions: Case I: traditional VR; Case II: Gen2-VR with no distractions and Case III: Gen2-VR with distractions and interruptions. In Case III, to simulate the effects of distractions and interruptions, music was played intermittently, the camera lens was fogged for 10 s and tools malfunctioned for 15 s at random points in time during the simulation. At the completion of the study subjects filled in a 5-point Likert scale feedback questionnaire. A total of sixteen subjects participated in this study. RESULTS: Friedman test showed significant difference in scores between the three conditions (p < 0.0001). Post hoc analysis using Wilcoxon signed-rank tests with Bonferroni correction further showed that all the three conditions were significantly different from each other (Case I, Case II, p < 0.0001), (Case I, Case III, p < 0.0001) and (Case II, Case III, p = 0.009). Subjects rated that fog (mean 4.18) and tool malfunction (median 4.56) significantly hindered their performance. CONCLUSION: The results showed that Gen2-VR simulator has both face and construct validity and that it can accurately and realistically present distractions and interruptions in a simulated OR, in spite of limitations of the current HMD hardware technology.

Development of a Virtual Reality Simulator for Natural Orifice Translumenal Endoscopic Surgery (NOTES) Cholecystectomy Procedure.

The first virtual-reality-based simulator for Natural Orifice Translumenal Endoscopic Surgery (NOTES) is developed called the Virtual Translumenal Endoscopic Surgery Trainer (VTESTTM). VTESTTM aims to simulate hybrid NOTES cholecystectomy procedure using a rigid scope inserted through the vaginal port. The hardware interface is designed for accurate motion tracking of the scope and laparoscopic instruments to reproduce the unique hand-eye coordination. The haptic-enabled multimodal interactive simulation includes exposing the Calot's triangle and detaching the gall bladder while performing electrosurgery. The developed VTESTTM was demonstrated and validated at NOSCAR 2013.

A framework for providing cognitive feedback in surgical simulators.

Providing cognitive feedback in a virtual reality simulator during training is essential for subjects to correct and learn proper techniques. In this work, we have developed a framework to identify key skills and cognitive knowledge required to perform a task and methods to provide to the user. The framework was verified by implementing a test case scenario with the peg transfer task of the FLS.

Modeling and control of tissue compression and temperature for automation in robot-assisted surgery.

Robotic surgery is being used widely due to its various benefits that includes reduced patient trauma and increased dexterity and ergonomics for the operating surgeon. Making the whole or part of the surgical procedure autonomous increases patient safety and will enable the robotic surgery platform to be used in telesurgery. In this work, an Electrosurgery procedure that involves tissue compression and application of heat such as the coaptic vessel closure has been automated. A MIMO nonlinear model characterizing the tissue stiffness and conductance under compression was feedback linearized and tuned PID controllers were used to control the system to achieve both the displacement and temperature constraints. A reference input for both the constraints were chosen as a ramp and hold trajectory which reflect the real constraints that exist in an actual surgical procedure. Our simulations showed that the controllers successfully tracked the reference trajectories with minimal deviation and in finite time horizon. The MIMO system with controllers developed in this work can be used to drive a surgical robot autonomously and perform electrosurgical procedures such as coaptic vessel closures.