基于OSG和Bullet的船舶碰撞响应三维仿真

针对目前在航海模拟器中缺少对船舶碰撞响应的三维仿真,提出在航海模拟器中基于开源场景图形(Open Scene Graph,OSG)渲染引擎开发的三维视景中加入Bullet物理引擎的技术方案.根据刚体动力学、接触与碰撞动力学和能量守恒定律,基于Bullet刚体碰撞响应模型,建立船舶三维碰撞动力学模型;运用Projected Gauss-Seidel迭代算法,得到碰撞后船舶实时的六自由度位置姿态参数;根据碰撞检测阶段获取的碰撞点位置参数,实时绘制划痕并添加爆炸特效.该方案已成功应用于航海模拟器视景系统中,渲染效果良好.

基于Bullet物理引擎的机器人仿真实验平台设计

为适应新时代工业机器人实验教学的蓬勃发展,设计了一种基于Bullet物理引擎的机器人仿真实验平台。该平台使用Bullet作为仿真引擎,具备运动学解算、碰撞检测与轨迹可视化的功能,使用Lua脚本作为主逻辑控制语言,调用仿真引擎功能函数。使用基于数据流的节点图作为主实验交互平台,将计算模块和通信模块封装为功能节点,通过图形连接定义运算逻辑。应用实例表明,该平台功能完善,可扩展性强,兼具脚本语言的灵活性与图形化语言的便捷性,适用于机器人的多种实验场景。

Calculation and Test of Hitting Force of Firing Bullet on the Bulletproof Helmet

In this paper the hit force of firing bullet on bulletproof helmet has been computed and the test device has been described. The device is divided into two parts: 1) The bullet, helmet and mould are in one system, using moment theorem to calculate the hit force; 2) The mould, sensor and support pole are in one system, using the method in reference [1] that measures the dynamic strain and displacement of simulate target of bulletproof clothes. We compute the transfigure energy and momentum energy when hitting the mould, the work done by the sensor and the expend energy of support pole. We get the hit force of helmet using energy balance principle. The result is according with the test and has been used to design the GGK93T bulletproof helmet and other serial products.

Control of exterior ballistic properties of spin-stabilized bullet by optimizing internal mass distribution

This paper introduces a novel approach for controlling the exterior ballistic properties of spin-stabilized bullets by optimizing their internal mass distributions. Specifically, the properties of interest are the bullets’ stability characteristics that are examined through dynamic and gyroscopic stability parameters.New analytical expressions for aerodynamic quantities are also derived to address the compressibility of air. These expressions are utilized in a bullet model that enables efficient computation of the stability parameters for a given mass distribution. The bullet model is used in the formulation of nonlinear optimization problems that provide optimal mass distributions with respect to given goals, i.e., desired stability characteristics. The bullet types investigated in this paper are a long range bullet and a limited range training bullet. In the optimization of the mass distribution of the long range bullet, the goal is that the bullet stays stable for as long as possible. The mass distribution of the training bullet is optimized such that the bullet is stable at launch but becomes unstable shortly afterwards. The global optimal solutions obtained with the new approach fulfill the desired stability characteristics better than currently used uniformly filled bullets. Overall, the optimization approach reveals a new goal focused philosophy for bullet design compared to current trial and error design practices.

Experimental study of bullet-proofing capabilities of Kevlar, of different weights and number of layers, with 9mm projectiles

Kevlar is the most commonly used material as armour for protection against bullets used in hand guns because of its impact resistance, high strength and low weight. These properties make Kevlar an ideal material to be used in bullet-proof vests as compared to other materials. In the present study, different numbers of layers of Kevlar with different weights are tested to determine the weights and the number of layers needed to design a safe bullet-proof vest. For this purpose, several ballistic tests were performed on combinations of ballistic gel and Kevlar layers of different weights. Ballistic impacts are generated by 9 mm Parabellum ammunition. The objective is to assess the characteristics of high-speed ballistic penetration into a combination of a gel and Kevlar and determine the number of layers needed to safely stop the 9 mm bullet and thereby contribute to the design of safe bullet-proof vests. The tests provide information on the distances the bullets can travel in a gel/Kevlar medium before they are stopped and to identify the resistance capabilities of Kevlar of different grams per square meter(GSM). The tests were conducted with the use of a chronograph in a controlled test environment. Specifically, results identify the number of layers of Kevlar required to stop a 9 mm Parabellum projectile, and the effectiveness of using different number of layers of GSM Kevlar material.

APPLICATION OF HOT-PRESS SINTERING TECHNIQUE TO EXPLOSIVE CHARGE LINER OF PETROLEUM PERFORATION BULLET

介绍了一种制备石油射孔弹的药形罩的新方法，采用粉末冶金技术，热压烧结工艺制备石油射孔弹的药形罩，并对药形罩的烧结工艺进行了研究。实验结果表明，采用该工艺制备的石油射孔弹药形罩可以满足要求。

ANALYSIS OF AERODYNAMIC CHARACTERISTIC ON GLIDE BULLET TO INCREASE RANGE

This paper mainly calculates, analyzes and compares the aerodynamic characteristics of two kinds of bullets, one has wing, and the other has no wing. The calculated results indicate that the lift force of the glide bullet with wing is much bigger than that has no wing, and it reached the aim to increase range.

COMPUTER SIMULATION OF THE MOTION OF THE BULLET BELT OF AIRPLANE GUN

ＣＯＭＰＵＴＥＲＳＩＭＵＬＡＴＩＯＮＯＦＴＨＥＭＯＴＩＯＮＯＦＴＨＥＢＵＬＬＥＴＢＥＬＴＯＦＡＩＲＰＬＡＮＥＧＵＮＺｈａｎｇＤｉｎｇｇｕｏ（章定国）（ＲｅｃｅｉｖｅｄＭａｒｃｈ１７，１９９５；ＣｏｍｍｕｎｉｃａｔｅｄｂｙＷｕＲｕｉｆｅｎｇ）Ａｂｓｔｒ...

Dynamics of plasma bullets by nanosecond pulsed micro-hollow cathode discharge within air

In this paper,the air plasma jet produced by micro-hollow cathode discharge(MHCD)is investigated.The discharge is powered by a positive nanosecond pulse high voltage supply.The waveforms of the discharge,the images of the jet,the evolution of the plasma bullet and the reactive species are obtained to analyze the characteristics of the MHCD plasma jet.It is found that the length of the plasma jet is almost proportional to the air flow rate of 2–6 slm.Two plasma bullets appear one after another during a single period of the voltage waveform,and both of the two plasma bullets are formed during the positive pulse voltage off.The propagation velocity of the two plasma bullets is on the order of several hundred m/s,which is approximate to that of the air flow.These results indicate that the gas flow has an important influence on the formation of this MHCD plasma jet.

Interactions between optical bullets with different velocities in the three-dimensional cubic-quintic complex Ginzburg-Landau equation

By using the three-dimensional complex Ginzburg-Landau equation with cubic-quintic nonlinearity,this paper numerically investigates the interactions between optical bullets with different velocities in a dissipative system.The results reveal an abundance of interesting behaviours relating to the velocities of bullets:merging of the optical bullets into a single one at small velocities;periodic collisions at large velocities and disappearance of two bullets after several collisions in an intermediate region of velocity.Finally,it also reports that an extra bullet derives from the collision of optical bullets when optical bullets are at small velocities but with high energies.

N_2 Mole Fraction Dependence of Plasma Bullet Propagation in Premixed He/N_2 Plasma Needle Discharge at Atmospheric Pressure

In this work, a computational modeling study on the mechanism of the acceleration behavior of a plasma bullet in needle-plane configuration is presented. Above all, in our model,two sub-models of time-dependent plasma dynamics and laminar flow are connected using a oneway coupled method, and both the working gas and the surrounding gas around the plasma jet are assumed to be the same, which are premixed He/N2 gas. The mole fractions of the N2（NMF）ingredient are set to be 0.01%, 0.1% and 1% in three cases, respectively. It is found that in each case, the plasma bullet accelerates with time to a peak velocity after it exits the nozzle and then decreases until getting to the treated surface, and that the velocity of the plasma bullet increases at each time moment with the peak value changing from 0.72×106m/s to 0.80×106m/s but then drops more sharply when the NMF varies from 0.01% to 1%. Besides, the electron impact ionizations of helium neutrals and nitrogen molecules are found to have key influences on the propagation of a plasma bullet instead of the penning ionization.

Effect of rifle bullet parameters on the penetration into ballistic gelatin

To understand the effects of the rifle bullet parameters on the bullet-gelatin interaction quantitatively,a finite element model of bullet penetrating gelatin was set up and computational results are compared with experimental ones.The penetration of the rifle bullet into the gelatin was simulated by the nonlinear finite element method.The quantitative analysis of the changes in the gelatin interaction with the rifle bullet were conducted by changing the bullet parameters,such as attack angle on gelatin,initial velocity,warhead's tip and location of mass center of bullet.Results demonstrate that with the increase of the attack angle,instable moment of the bullet moves forward,the length of narrow wound channel shortens,and when penetration is completed diameters of temporary cavities increase,the gelatin energy and energy transmission ratio increases;With the increase of the impact velocity,instable moment of the bullet moves forward,the maximum forces acting on the gelatin and the gelatin energy increase remarkably;the length of narrow wound channel shortens,diameters of temporary cavities increase when penetration is completed,the gelatin energy and energy transmission ratio increase;The warhead's tip and location of mass center have a influence on the instable moment of the bullet and length of the narrow wound channel.The instable moment delays and narrow wound channel increases when the warhead's tip flattens.The instable moment moves forward a little and the narrow wound channel shortens a little when location of mass center moves back.

Formation Mechanism of the Ring-shaped Structure of Plasma Bullet

The formation of plasma bullets’ring-shaped structure in atmospheric pressure helium is analyzed by using a coupled fluid model.The model consists of a two-dimension neutral gas flow module and a one-dimension plasma dynamics module.The obtained radial distributions of the electron’s number density and the nitrogen’s metastable number density have different structures under different types of reactions or air contents in the model.It shows that total electron impact ionization plays an important role in sustaining the discharge,and together with Penning process,they lead to the shifted-off structure of electron number density.Meanwhile,the ring structure of plasma bullets forms mainly due to the excitation reaction of nitrogen molecule on air contents.

新能源汽车PC灯罩的注塑模具设计

针对某款新能源汽车聚碳酸酯(PC)灯罩的结构特点,模具采用一模两腔“L+R”形式的型腔布局。通过对产品成型的CAE分析,模具采用两组针阀式的热流道结构。根据产品外表面局部多处内凹的特征,对定模设计了结构紧凑的“弹块+斜导柱”的脱模结构,并通过机械拉钩机构保证弹块工作的可靠性。由于产品为透明塑件,因此对产品内表面的质量要求也高,又由于其结构较为复杂,产品有多处安装定位特征,对动模采用“斜导柱+滑块+成型块”的联动抽芯结构。在顶出系统方面采用了“方直顶杆+导向块+大顶块”的方式,成功解决产品顶出困难的问题。在冷却系统方面,各个大弹块及大顶块中都设有直径8 mm的独立水路,其余部位设计为直径11.5 mm的水路,将产品包在中间,组成“随形水路”。模具投产后,各抽芯及顶出机构运行平稳,产品各项参数均符合要求,证明各机构设计合理,安全有效。

弹幕视频网站盈利模式分析——以B站为例

随着互联网的迅速发展,关注视频网站的群体数量与日俱增,与传统视频网站相比,青少年群体更热衷使用弹幕视频网站,B站仅靠几年时间便发展成为此类网站的佼佼者。本文基于弹幕网站平台的用户特征,研究其基于广告、游戏、直播与电商等多种业务模型的盈利模式,分析B站运行中可能遇到的广告收入不稳定、视频内容审核、竞争压力等问题,提出加强品牌建设,严格审核,打造优质内容的建议,仅供参考。

基于改进YOLOv5的复杂环境下小目标弹孔识别

为实现能够在不同光照、阴影遮挡、弹孔重叠等复杂环境下对靶面弹孔的高效精准地识别,提出一种基于改进YOLOv5的实例分割算法。模型以YOLOv5主干网络为基础,融合了含有ASPP模块的分割解码器,实现对弹孔小目标的实例分割;对目标检测端输出参数进行解耦,降低回归参数与类别概率的耦合影响,提高识别精度;调整模型的输出尺度,删减预测大目标的特征层,增加融合低层信息的极小目标预测层,以此提升检测召回率与精确率。对于经过数据集训练后的模型,在测试集下的检测精度达到92.42%,检测速度达到25.15帧/s。与原网络YOLOv5、Mask RCNN、Deeplabv3+等网络的对比试验表明,所提模型在复杂环境下具有较高的检测精度与检测速度,满足实际训练中的精确性与实时性要求。

定射角射孔工艺在大位移定向井中的应用与实践

通过对萨中开发区112#断层区块构造特征和开发井网情况的深入研究,部署距离断层50 m平行断层面钻井的大位移定向井。考虑射孔油层保护要求,结合定射角射孔工艺原理,确定射孔工艺、射孔输送方式及匹配的射孔枪、弹等射孔参数,选用合理的射孔液,采用负压射孔工艺、确定合理负压值,保证了定射角射孔工艺效果。实现了单井日增液17.6 t,日增油4.2 t,年节电约2.56×10^(4) kWh,创造较好的经济效益,保证了油田开发效果。

基于U型线圈的弹链信息交联信号获取方法

弹链运动轨迹中感应装定引信无法穿过圆形结构的装定线圈、随着引信数据量增大,用于信息感应装定的窗口在装定时间不变的情况下就显得仓促、甚至不足以满足现状。另外装定的操作程序复杂导致反应时间过长。针对这些问题,提出了基于U型线圈感应装定装置的弹链信息交联信号获取方法。该方法利用U型线圈磁力线的垂直方向与引信的水平方向运动路径有效交集,分析了感应窗口内的磁场均匀性、信号波形的幅度余量和空间的特征,通过调整复杂的发射线圈形状,采用多匝、多组线圈,组合发送信号;增大线圈的发射空间获取最大感应信号,从而改变了接收线圈上感应信号电压曲线的混合叠加形状。研究结果表明:通过线圈的U型结构变化,极大改善了线圈的耦合效果,U型线圈形成的有限感应装定空间最大幅度变化在±20%、达到均匀一致性,装定窗口明显增大到[±10 mm,±10 mm,±5 mm];感应装定时间余量满足±20%变化。数据量在1 s内达到4 k字节;U型的发射线圈满足弹链上引信的特殊运动轨迹,U型的装定电压门限设置为14V,发射线圈产生的更大的装定窗口。

典型小口径自动步枪热散形成原因分析与结果预估

热散现象是小口径自动步枪在连续射击后出现的射弹散布异常现象,对热枪状态命中率和作战效能有重要影响,形成机理尚不完全清楚。通过冷热枪对比试验发现,热枪状态下枪管向铜材料弹头壳传热,弹头壳温度升高、材料变软,弹与枪相互作用,使弹头出膛速度偏角和弹轴摆角大幅度增大,这是热散的主要原因。基于试验获得的热散机理,提出一种典型小口径自动步枪热散分析计算方法。该方法采用分段建模和参数传递方法,通过建立热枪状态枪管温度场和应力场分析模型、弹-枪相互作用热力耦合计算模型和随机外弹道及射弹散布计算模型,实现了热枪状态射击密集度的定量分析计算。计算结果与试验结果基本一致,为小口径自动步枪热散问题定量分析提供了有效预估策略。

步枪弹侵彻背部穿硬防护人体靶标钝击效应研究

针对枪弹侵彻穿防弹衣人体背部产生脊柱脊髓钝性损伤,建立了DBP10式5.8 mm步枪弹侵彻NIJⅢ级SiC/UHMWPE防弹插板的数值模型,采用JHB本构和基于Abaqus二次开发的VUMAT本构分别模拟SiC陶瓷和UHMWPE层合板;开展了5.8 mm步枪弹侵彻NIJⅢ级SiC/UHMWPE防弹插板的数值模拟,通过基于高速摄影的弹道实验结果对比验证了数值模型的准确性;基于枪弹侵彻防弹插板的数值模拟结果,开展了5.8 mm步枪弹以910 m/s入靶速度侵彻背部穿硬防护人体躯干靶标的数值模拟,明确了步枪弹击中防弹衣后压力波在肌肉-脊柱内的传导规律,还原了枪弹侵彻过程中人体典型器官(心、肝、肺、胃等)的应力波传递过程。结果表明:人体背部在枪弹钝击作用下会在脊椎椎骨上产生瞬时高应力,可能导致椎骨骨折、椎间盘突出和脊柱不稳定;致伤点T10椎体后方脊髓最大应力为1.04 MPa,可能导致脊髓改变;对脊髓上应力与加速度线性回归分析表明,压力与加速度呈正相关。