Influence of the embedded structure on the EFP formation of compact terminal sensitive projectile

To improve the damage efficiency of compact terminal sensitive projectile with EFP warhead,it is vital to understand how the embedded structure(ES)affects the EFP forming performance.In this paper,the corresponding numerical investigation is focused on,in which the fluid-structure interaction(FSI)method and the experimental verification are used.Based on the obtained quantitative relations between the forming performance and a(the ratio of height to maximum radius of ES),an optimal design is further provided.The results indicate that:when the embedded structural length and width range 0.1e0.3D and 0.1e0.2D(D:diameter of EFP warhead)at a fixed volume,respectively,EFP forming velocity nearly keeps as a constant,1760 m/s;the height of ES has a dramatical effect on the propagating range of detonation wave,resulting in significant influence on the aerodynamic shape and length-to-diameter ratio of EFP;under the given constraints,the EFP length-diameter ratio can reach the optimal value2.76,when the height of ES is 0.22D.

Minimally invasive open reduction of greater tuberosity fractures by a modified suture bridge procedure

BACKGROUND Most greater tuberosity fractures can be treated without surgery but some have a poor prognosis.The surgical procedures for avulsion fractures of the humeral greater tuberosity include screw fixation,suture anchor fixation,and plate fixation,all of which have treatment-associated complications.To decrease surgical complications,we used a modified suture bridge procedure under direct vision and a minimally invasive small incision to fix fractures of the greater tuberosity of the humerus.AIM To investigate the clinical efficacy and outcomes of minimally invasive modified suture bridge open reduction of greater tuberosity evulsion fractures.METHODS Sixteen patients diagnosed between January 2016 and January 2019 with an avulsion-type greater tuberosity fracture of the proximal humerus and treated by minimally invasive open reduction and modified suture bridges with anchors were studied retrospectively.All were followed up by clinical examination and radiographs at 3 and 6 wk,3,6 and 12 mo after surgery,and thereafter every 6 mo.Outcomes were assessed preoperatively and postoperatively by a visual analog scale(VAS),the University of California Los Angeles(UCLA)shoulder score,the American Shoulder and Elbow Surgeon score(ASES),and range of motion(ROM)for shoulders.RESULTS Seven men and nine women,with an average age of 44.94 years,were evaluated.The time between injury and surgery was 1-2 d,with an average of 1.75 d.The mean operation time was 103.1±7.23 min.All patients achieved bone union within 3 mo after surgery.VAS scores were significantly decreased(P=0.002),and the mean degrees of forward elevation(P=0.047),mean degrees of abduction(P=0.035),ASES score(P=0.092)were increased at 3 wk.The UCLA score was increased at 6 wk(P=0.029)after surgery.The average degrees of external rotation and internal rotation both improved at 3 mo after surgery(P=0.012 and P=0.007,respectively).No procedure-related deaths or incision-related superficial or deep tissue infections occurred.CONCLUSION Modified suture bridge was effective for the treatment of greater tuberosity evulsion fractures,was easier to perform,and had fewer implants than other procedures.

Quasi-steady aerodynamic characteristics of Terminal Sensitive Bullets with short cylindrical portion

The aerodynamic characteristics are vital for short cylindrical Terminal Sensitive Bullets(TSB)with lowaspect ratio,especially in terminal trajectory.Currently,there is little research in terms of the TSB andshort cylinder with two free ends,and particularly in this trajectory,where the scanning angleβand rollangle a vary over a broad range between 0°and 180.In this work wind tunnel experiments are firstconducted to learn the effects of Reynolds number and scanning angle on aerodynamic parameters forshort cylinder with aspect ratio L/D=1.Similar to infinite cylinder,for the short cylinder with two freeends,the drag crisis phenomenon still exists in the critical regime 1.7×10^(5)≤Re≤6.8×10^(5).Then 3Dsimulations are performed to demonstrate the aerodynamic characteristics of short cylinder and TSBover a broad range of Re,L/D,a and 6.The sensitivity analysis of time step and grid are presented as well.whenβ3=0,for short cylinder,the drag crisis phenomenon was also observed in the simulation,but notas obvious as in the wind tunnel test.In some attitudes,there is an obvious Karman vortexin the wake ofshort cylinder and TSB.The correlation between time-averaged aerodynamic coefficients and L/D,Re,a&l is discussed.The vortex shedding frequency and shear layer behavior are obtained for quasi-steadyand unsteady flow.Finally,the effect of end's shape on drag reduction and vortex shedding frequency isanalyzed.

A survey of deep learning-based 3D shape generation

Deep learning has been successfully used for tasks in the 2D image domain.Research on 3D computer vision and deep geometry learning has also attracted attention.Considerable achievements have been made regarding feature extraction and discrimination of 3D shapes.Following recent advances in deep generative models such as generative adversarial networks,effective generation of 3D shapes has become an active research topic.Unlike 2D images with a regular grid structure,3D shapes have various representations,such as voxels,point clouds,meshes,and implicit functions.For deep learning of 3D shapes,shape representation has to be taken into account as there is no unified representation that can cover all tasks well.Factors such as the representativeness of geometry and topology often largely affect the quality of the generated 3D shapes.In this survey,we comprehensively review works on deep-learning-based 3D shape generation by classifying and discussing them in terms of the underlying shape representation and the architecture of the shape generator.The advantages and disadvantages of each class are further analyzed.We also consider the 3D shape datasets commonly used for shape generation.Finally,we present several potential research directions that hopefully can inspire future works on this topic.

Interactive modeling of lofted shapes from a single image

Modeling the complete geometry of general shapes from a single image is an ill-posed problem.User hints are often incorporated to resolve ambiguities and provide guidance during the modeling process. In this work, we present a novel interactive approach for extracting high-quality freeform shapes from a single image. This is inspired by the popular lofting technique in many CAD systems, and only requires minimal user input. Given an input image, the user only needs to sketch several projected cross sections, provide a"main axis", and specify some geometric relations. Our algorithm then automatically optimizes the common normal to the sections with respect to these constraints,and interpolates between the sections, resulting in a high-quality 3 D model that conforms to both the original image and the user input. The entire modeling session is efficient and intuitive. We demonstrate the effectiveness of our approach based on qualitative tests on a variety of images, and quantitative comparisons with the ground truth using synthetic images.

3D computational modeling and perceptual analysis of kinetic depth effects

Humans have the ability to perceive kinetic depth effects, i.e., to perceived 3 D shapes from 2 D projections of rotating 3 D objects. This process is based on a variety of visual cues such as lighting and shading effects. However, when such cues are weak or missing, perception can become faulty, as demonstrated by the famous silhouette illusion example of the spinning dancer. Inspired by this, we establish objective and subjective evaluation models of rotated3 D objects by taking their projected 2 D images as input. We investigate five different cues: ambient luminance, shading, rotation speed, perspective, and color difference between the objects and background.In the objective evaluation model, we first apply3 D reconstruction algorithms to obtain an objective reconstruction quality metric, and then use quadratic stepwise regression analysis to determine weights of depth cues to represent the reconstruction quality. In the subjective evaluation model, we use a comprehensive user study to reveal correlations with reaction time and accuracy, rotation speed, and perspective. The two evaluation models are generally consistent, and potentially of benefit to inter-disciplinary research into visual perception and 3 D reconstruction.

Fitting quadrics with a Bayesian prior

Quadrics are a compact mathematical formulation for a range of primitive surfaces. A problem arises when there are not enough data points to compute the model but knowledge of the shape is available. This paper presents a method for fitting a quadric with a Bayesian prior. We use a matrix normal prior in order to favour ellipsoids when fitting to ambiguous data. The results show the algorithm copes well when there are few points in the point cloud,competing with contemporary techniques in the area.