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.

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.

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.

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 re- suits 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 ge- latin interaction with the rifle bullet were conducted by changing the bullet parameters, such as at- tack 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 tem- porary cavities increase, the gelatin energy and energy transmission ratio increases; With the in- crease 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 influ- ence on the instable moment of the bullet and length of the narrow wound channel. The instable mo- ment delays and narrow wound channel increases when the warhead＇s tip flattens. The instable mo- ment moves forward a little and the narrow wound channel shortens a little when location of mass center moves back.

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.

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 axe 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 0.72×10^6 m/s to 0.80×10^6 m/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.

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。

A shield of defense:Developing ballistic composite panels with effective electromagnetic interference shielding absorption

The primary goal of this study is to develop cost-effective shield materials that offer effective protection against high-velocity ballistic impact and electromagnetic interference(EMI)shielding capabilities through absorption.Six fiber-reinforced epoxy composite panels,each with a different fabric material and stacking sequence,have been fabricated using a hand-layup vacuum bagging process.Two panels made of Kevlar and glass fibers,referred to as(K-NIJ)and(G-NIJ),have been tested according to the National Institute of Justice ballistic resistance protective materials test NIJ 0108.01 Standard-Level IIIA(9 mm×19 mm FMJ 124 g)test.Three panels,namely,a hybrid of Kevlar and glass(H-S),glass with ceramic particles(C-S),and glass with recycled rubber(R-S)have been impacted by the bullet at the center,while the fourth panel made of glass fiber(G-S)has been impacted at the side.EMI shielding properties have been measured in the X-band frequency range via the reflection-transmission method.Results indicate that four panels(K-NIJ,G-NIJ,H-S,and G-S)are capable of withstanding high-velocity impact by stopping the bullet from penetrating through the panels while maintaining their structural integrity.However,under such conditions,these panels may experience localized delamination with variable severity.The EMI measurements reveal that the highest absorptivity observed is 88% for the KNIJ panel at 10.8 GHz,while all panels maintain an average absorptivity above 65%.All panels act as a lossy medium with a peak absorptivity at different frequencies,with K-NIJ and H-S panels demonstrating the highest absorptivity.In summary,the study results in the development of a novel,costeffective,multifunctional glass fiber epoxy composite that combines ballistic and electromagnetic interference shielding properties.The material has been developed using a simple manufacturing method and exhibits remarkable ballistic protection that outperforms Kevlar in terms of shielding efficiency;no bullet penetration or back face signature is observed,and it also demonstrates high EMI shielding absorption.Overall,the materials developed show great promise for various applications,including the military and defense.

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。

基于组合赋权与灰色聚类的枪弹品质评估

针对枪弹品质无法定量评估、枪弹数据利用率低等问题,提出一种基于主客观组合赋权与灰色聚类的枪弹品质评估模型。该模型采用线性加权将主客观赋权法所得权重相结合,以提高评估方法中指标赋权的科学性,构造隶属度函数,再利用灰色聚类的方法得出综合影响因数,从而得到枪弹的品质判断结果。以12.7 mm穿甲燃烧弹开展评估,并进行立靶密集度试验。结果表明,该方法具有较好的区分度,密集度指标R100,I类(12.77 cm)约域类(15.02 cm)约芋类(18.92 cm),验证了方法的有效性。

基于改进YOLOv8s算法的胸环靶弹孔检测技术

为了解决传统胸环靶弹孔检测技术在自然条件下易受光照强度、复杂背景影响的问题,设计了一种基于YOLOv8s的改进算法。首先,在数据集的制作过程中引入图形分割将背景与胸环靶分离,避免了复杂环境对弹孔识别精度的影响。其次,为提升模型对弹孔的检测能力,在C2f中引入CBAM注意力机制,通过对空间和通道特征赋予不同的权值提高网络对弹孔目标的识别能力;增加检测尺度为160×160的小目标输出层,减少了弹孔特征在下采样过程中的信息损失并降低弹孔漏检的概率;考虑到原有卷积层对小目标不敏感,采用SPD-Conv模块替换原有卷积层,提取更多的特征信息提升检测精度。最后,将边界框损失函数更改为WIoU以减弱正负样本数量不均衡的影响,提高了预测框的回归精度。在自制胸环靶数据集的实验结果表明:改进算法的准确率P为96.9%、召回率R为96.4%、平均精度mAP50为98.0%,相较于原算法,分别提升8.8百分点、25.4百分点、15.3百分点。实验结果证明改进的YOLOv8s模型在复杂环境和密集弹孔的检测方面具有更好的性能。

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。

弹幕语言的语码转换探析——以韩剧TV中的弹幕语言为例

弹幕语言是网络语言新形式之一,存在着形式多样的句内语码转换现象。以韩剧TV中的弹幕语言为例,弹幕语言语码转换的语表形式主要表现在四个方面:方言与普通话的语码转换、英语与普通话的语码转换、韩语与普通话的语码转换、多语间的语码转换。弹幕语言语码转换的语用功能则表现在七个方面:信息传递功能、顺应功能、评价功能、委婉表达功能、共情功能、戏谑功能、填补功能。韩语影视剧和综艺节目网络言语社区是一个典型的网络言语社区,它可以作为上位概念,包含具有类似功能、表达习惯、心理认同的其他网络语言社区。弹幕语言的语码转换是该社区群体成员身份标记和心理认同的外显形式。通过使用语码转换,该网络言语社区的内部一致性与排他性特点得到凸显。

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。