An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.

Modelling of internal ballistics of gun systems:A review

A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballistics is to estimate the gas pressure into the combustion chamber and the projectile muzzle velocity in order to use the propellant to its higher efficiency while avoiding over-pressure phenomena. Dealing with the internal ballistic problem is a complex undertaking since it requires handling the interaction between different constituents during a transient time lapse with very steep rise of pressure and temperature. Several approaches have been proposed in the literature, based on different assumptions and techniques. Generally, depending on the used mathematical framework, they can be classified into two categories: computational fluid dynamics-based models and lumped-parameter ones. By focusing on gun systems, this paper offers a review of the main contributions in the field by mentioning their advantages and drawbacks. An insight into the limitations of the currently available modelling strategies is provided,as well as some considerations on the choice of one model over another. Lumped-parameter models, for example, are a good candidate for performing parametric analysis and optimisation processes of gun systems, given their minimum requirements of computer resources. Conversely, CFD-based models have a better capacity to address more sophisticated phenomena like pressure waves and turbulent flow effects. The performed review also reveals that too little attention has been given to small calibre guns since the majority of currently available models are conceived for medium and large calibre gun systems.Similarly, aspects like wear phenomena, bore deformations or projectile-barrel interactions still need to be adequately addressed and our suggestion is to dedicate more effort on it.

Mussel-inspired PTW@PDA composites for developing high-energy gun propellants with reduced erosion and enhanced mechanical strength

The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate whisker(PTW,K_(2)Ti_(6)O_(13)),and after was incorporated into gun propellant as erosion-reducing and mechanical-reinforcing fillers.The interfacial characterizations results indicated that as-prepared PTW@PDA composites exhibits an enhanced surface compatible with propellant matrix,thereby facilitating their dispersion into propellants more effectively than raw PTW materials.Compared to original propellants,PTW@PDA-modified propellants exhibited significant less erosion,with a Ti-Kbased protective coating being detected on the eroded steel.And 0.5 wt%and 1.0 wt%addition of PTW@PDA significantly improved impact,compressive and tensile strength of propellants.Despite the inevitably reduction in relative force,PTW@PDA slightly increase propellant burning rate while exerting little adverse impact on propellant dynamic activity.This strategy can provide a promising alternative to develop high-energy gun propellant with less erosion and more mechanical strength.

认知错误是如何发生的?——《枪炮、病菌与钢铁》研究人类发明案例的启示

人类文明的演进,与发明密切相关。对于发明,传统看法是人们的需要促成了发明的产生,换言之,“需要乃发明之母”。这一观点看去天经地义,似无问题。但贾雷德·戴蒙德(Jared Diamond)在《枪炮、病菌与钢铁》一书中,通过对众多发明案例的系统梳理与分析,却得出两个完全不同的认识:一,在众多发明案例中,因需要而产生的发明只占极少一部分,绝大部分发明并非因需要而产生,相反,而是发明催生了需要,即“发明常常是需要之母,而不是相反”。二,将发明归咎于某一天才人物即“英雄史观”往往是后世的杜撰,发明“不是靠孤立的英雄行为”,而是技术长期积累、发展的结果。

真空电子束熔覆装备研制

围绕真空电子束熔覆装备战略需求,聚焦核心功能零部件的研制开发。研究电子束枪技术、机械运动机构及控制技术,真空定量送粉技术等关键技术。电子束熔覆装备由电子束枪系统、机械运动及控制系统、真空系统、真空送粉系统、监视系统、PLC总控系统等组成。研制等离子体空心阴极结构的电子束枪,实现电子束在低真空条件下的正常工作,阴极连续工作时间可超过50h,适合送粉式电子束熔覆及增材制造。优化电磁聚焦系统的设计,通过调整磁场分布来控制电子束的聚焦程度。通过聚焦系统保证电子束流良好的聚焦电流稳定性,聚焦电流测量值较设定值偏差≤0.5%。研究实现了五轴联动运动机构及数控系统,实现空间复杂曲面的熔覆及增材。研究了抽真空及真空送粉系统,实现连续可控送粉。通过PLC控制系统将电子枪、真空系统、运动系统等与控制系统进行集成,进行整体调试和优化。解决系统运行中可能出现的兼容性和稳定性问题。实现上述关键技术的突破,是实现电子束熔覆装备国产化集成制造的必要条件。

蒙古高原北部Gun Nuur硅藻属种组成与分布特征

本文通过对蒙古高原北部表层沉积物中硅藻属种的鉴定,探讨硅藻属种的分布特征及对水环境变化的响应。Gun Nuur湖泊中共鉴定出2纲7科12属21种硅藻,以羽纹纲为主,Cymbella cistula、Amphora ovalis、Amphora baltica、Amphora ovalis var.pediculus等为相对优势种,且平均相对含量分别为24.4%、23.8%、16.9%、15.6%,其余属种均少于10.0%。优势硅藻种Cymbella cistula表明了Gun Nuur湖泊主要为淡水、偏碱性水体,pH值为8.0左右,距湖岸较近位置有大量的水生生物发育。Anomoeoneis costata和Anomoeoneis sphaerophora var.sphaerophora、Navicula oblonga反映出湖泊由于蒸发作用而导致水体咸化,湖泊矿化度升高,并且湖水属于Na-Ca/Cl-SO4型。在高纬度气候非常寒冷地区的湖泊中,硅藻生长受到严重的抑制作用。偏"胖"的特征有利于硅藻浮游以适应水体温度的变化,湖泊边沿结冰后向湖泊中心游动。湖泊在冰封后可以阻止风浪作用,并且在低于水温的季节中,冰封可以使湖泊水体在阳光照射条件下保持高于外部环境的温度而有利于硅藻的生长。广盐性、真静水性硅藻Epithemia intermedia反映了这种湖泊长期冰封下静水特征。

Modeling air gun signatures in marine seismic exploration considering multiple physical factors

Based on analyzing the limit of Ziolkowski＇s bubble oscillation formulation,a new model with various physical factors is established to simulate air gun signatures fo marine seismic exploration.The practical effects of physical factors,such as heat transfe across the bubble wall,air gun port throttling,vertical rise of the bubble,fluid viscosity,and the existence of the air gun body were all taken into account in the new model.Compared with Ziolkowski＇s model,the signatures simulated by the new model,with small peak amplitude and rapid decay of bubble oscillation,are more consistent with actual signatures The experiment analysis indicates：（1）gun port throttling controls the peak amplitude of ai gun pulse;（2）since the hydrostatic pressure decreases when the bubble rises,the bubble oscillation period changes;（3）heat transfer and fluid viscosity are the main factors tha explain the bubble oscillation damping.

Fabrication, tribological and corrosion behaviors of detonation gun sprayed Fe-based metallic glass coating

A metallic glass coating with the composition of Fe51.33Cr14.9Mo25.67Y3.4C3.44B1.26 （mole fraction, %） on the Q235 stainless steel was developed by the detonation gun （D-gun） spraying process. The microstructure and the phase aggregate were analyzed by scanning electron microscopy and X-ray diffractometry, respectively. Microhardness, wear resistance and corrosion behavior were assessed using a Vickers microhardness tester, a ball-on-disk wear testing machine and the electrochemical measurement method, respectively. Microstructural studies show that the coatings possess a densely layered structure with the porosity less than 2.1%. The tribological behavior of the coatings examined under dry conditions shows that their relative wear resistance is five times higher than that of the substrate material. Both adhesive wear and abrasive wear contribute to the friction, but the former is the dominant wear mechanism of the metallic glass coatings. The coatings exhibit low passive current density and extremely wide passive region in 3.5% NaCl solution, thus indicating excellent corrosion resistance.

矩阵相乘Cannon并行算法在工作站机群上的实现

矩阵相乘Cannon并行算法是一个基于分布式存储多处理机模型的并行数值算法,文章研究了它在工作站机群上的实现。在满足负载平衡和减少网络间数据传输的条件下,主要探讨了子任务在工作站上的优化分配策略,最后给出了在PVM并行编程环境下的具体实现方法。

Microstructure, mechanical and oxidation characteristics of detonation gun and HVOF sprayed MCrAlYX coatings

Microstructure, mechanical property and oxidation resistance of MCrAlYX coatings prepared by detonation gun (D-gun) and HVOF spraying were investigated. Lamellar microstructure and uniform microstructure formed in D-gun sprayed MCrAlYX coating and HVOF sprayed coating, respectively. Element redistribution and formation of new phase took place during the detonation process. Besides, the porosity of D-gun sprayed coating was much lower than that of HVOF sprayed coating. On the mechanical property, the micro-hardnesses of the two coatings were in the same level (~HV 910). However, D-gun sprayed MCrAlYX coating exhibited larger standard deviation of microhardness due to its lamellar microstructure, and exhibited better bend bonding strength owing to the existence of residual compressive stress between the layers and particles. Meanwhile, due to the much more compact microstructure, D-gun sprayed MCrAlYX coating showed superior oxidation resistance to the HVOF sprayed coating. The continuous dense protective layer can form earlier in D-gun sprayed coating and thus suppress further oxidation and control the oxide thickness at a relatively low level.

矩阵相乘Cannon并行算法在工作站机群上的实现

矩阵相乘Cannon并行算法是一个基于分布式存储多处理机模型的并行数值算法,本文研究了它在工作站机群上的实现。在满足负载平衡和减少网络间数据传输的条件下,主要探讨了子任务在工作站上的优化分配策略,最后给出了在pvm并行编程环境下的具体实现方法。

StimGun复合射孔技术的应用

随着油气井勘探开发的深入,低孔、低渗、致密岩性的非常规油气层在油气储量中占较大的比例,由于其储层性质差,勘探开发难度大,采用常规射孔很难取得理想的效果。StimGun复合射孔技术是在射孔枪起爆后,推进剂燃烧产生高能气体,高能气体进入射孔孔道并在射孔孔眼周围形成多径向裂缝,从而沟通了天然裂缝,改善了油气流动通道,提高渗流能力。介绍了该技术的工作原理和技术优势,并通过现场试验、总结和完善,形成了一套满足于不同地质条件的、集安全施工设计和作业效果评价为一体的stimgun复合射孔技术。该技术成功应用于四川LG区块的射孔作业中,能有效的控制裂缝高度,达到清楚地层污染而又不出水的效果,对地透气性地层具有较好的改造作用,取得较好的作业效果。

双螺杆捏合方式制备的三基发射药的流变性研究

为掌握三基发射药连续化捏合工艺中药料的流变特性,提高工艺模型的准确性,按照三基发射药代料配方制备了预混药料,使用双螺杆挤出机对预混药料进行捏合,并通过专用双料筒毛细管流变仪测试捏合后药料的流变特性。分别改变双螺杆挤出机的螺杆转速和捏合温度、药料的固含量和溶剂比,分析以上变量对三基发射药流变学参数的影响规律。结果表明:双螺杆捏合后,药料的本构方程与Carreau-Yasuda本构模型拟合程度较高;一定范围内,螺杆转速或捏合温度的提高会使捏合后的药料的剪切黏度降低;同时,螺杆转速的提高会使药料的停留时间减少,而过短的停留时间会导致捏合后的药料的黏度上升;固含量的增加或溶剂比的减小会使捏合后的药料的剪切黏度增大,而黏度增大会使药料的停留时间增长,一定程度上使药料受到更充分的捏合作用。

Simulation Study on the Feasibility of Gun-Launched Missile Against Attack Helicopters

The feasibility of providing the tank a limited anti helicopter ability with gun launched missile is studied. A type of simulation model of gun launched missile against attack helicopters is established. The simulation and the parameter optimization of missile control system under various circumstances are done. The gun launched missile can directly hit the helicopters in the typical tracks, all the missdistances are less than 1?m and the maximum overload is less than available overload. Gun launched missile is a feasible choice for tanks against attack helicopters.

MARIE:One-Stage Object Detection Mechanism for Real-Time Identifying of Firearms

Security and safety remain paramount concerns for both governments and individuals worldwide.In today’s context,the frequency of crimes and terrorist attacks is alarmingly increasing,becoming increasingly intolerable to society.Consequently,there is a pressing need for swift identification of potential threats to preemptively alert law enforcement and security forces,thereby preventing potential attacks or violent incidents.Recent advancements in big data analytics and deep learning have significantly enhanced the capabilities of computer vision in object detection,particularly in identifying firearms.This paper introduces a novel automatic firearm detection surveillance system,utilizing a one-stage detection approach named MARIE(Mechanism for Realtime Identification of Firearms).MARIE incorporates the Single Shot Multibox Detector(SSD)model,which has been specifically optimized to balance the speed-accuracy trade-off critical in firearm detection applications.The SSD model was further refined by integrating MobileNetV2 and InceptionV2 architectures for superior feature extraction capabilities.The experimental results demonstrate that this modified SSD configuration provides highly satisfactory performance,surpassing existing methods trained on the same dataset in terms of the critical speedaccuracy trade-off.Through these innovations,MARIE sets a new standard in surveillance technology,offering a robust solution to enhance public safety effectively.

钝感高能硝胺发射药内弹道性能的预测

为了分析钝感高能硝胺发射药内弹道性能的影响因素,基于密闭爆发器试验和14.5 mm弹道测试构建了高能硝胺发射药的内弹道模型,采用粒子群算法拟合了模型修正系数,进而基于模型理论计算分析了燃烧渐增性因子Pr及装药量ω对弹丸初速V_(0)和最大膛压p_(m)的影响。结果表明:基于经典内弹道理论预测高能硝胺发射药动态燃烧特性时,需考虑燃速修正系数χ和火药力利用系数η。与静态燃烧相比,动态燃烧的等效燃速相对增长可超过10%。同时,由于能量耗散的影响,理论计算中仅80%左右的火药力可有效转换为弹丸动能。发射药内弹道性能受Pr、ω、χ和η的耦合影响。作为主要机制,发射药静态燃烧性能和装药量显著影响着内弹道性能;V_(0)和ω线性正相关,p_(m)可表征为ω的指数函数;Pr决定了不同关联式中的系数。然而,在不同工艺条件下,χ和η的波动使内弹道性能变化,增大了拟合关联式的预测偏差。

响应面法优化球扁药脱硝工艺研究

为探索工艺参数对球扁药脱硝反应的影响规律,利用响应面法的Box-Behnken设计优化球扁药脱硝工艺。在单因素实验基础上,分析了脱硝剂质量分数、反应温度和反应时间对梯度硝基球扁药爆热的影响;利用显微拉曼技术研究了梯度硝基球扁药的微观结构组成;并采用密闭爆发器实验对脱硝前、后球扁药的定容燃烧性能进行研究。单因素实验和响应面法优化结果均表明,影响梯度硝基球扁药性能的工艺参数主次顺序为:反应温度、反应时间、脱硝剂质量分数。通过响应面法建立的脱硝工艺参数与梯度硝基球扁药爆热之间的模型相关系数为0.9785,且实验验证所得爆热与响应面模型预测的爆热基本吻合,表明优化得到的响应面模型具有可靠性和有效性。拉曼表征结果表明,梯度硝基球扁药表层硝酸酯基的分布由表及里呈梯度递增趋势。通过调节工艺参数,使得梯度硝基球扁药的爆热和燃烧渐增性大范围可控,为梯度硝基球扁药性能的精准调控提供了技术和理论支持。

论Cannon算法在并行计算机上的运用研究

Cannon算法是一种较为便捷的并行算法,多用于计算机上的运用,采用这种算法能够大大提高计算机的运行效率,使得用户能够更好的使用计算机资源。本文主要从Cannon算法的基本原理,结合实际计算机运用,探讨Cannon算法在计算机环境中运行的最佳效果。

水稻镁离子螯合酶调控蛋白Gun4羧基末端的功能分析

植物叶绿素生物合成途径(镁分支)中的第一个酶是镁离子螯合酶,它由I(ChlI)、D(ChlD)和H(ChlH)三个亚基组成.各亚基不仅参与叶绿素的生物合成,而且还与叶绿体到细胞核的反向信号传导有关.Gun4是一个卟啉结合蛋白,它能提高植物镁离子螯合酶的活性,在缺乏Gun4的条件下,镁离子螯合酶整个复合物非常不稳定,不足以开始催化反应.我们以前的研究发现,Gun4的C末端几个氨基酸具有重要作用.在本文中,通过缺失突变,获得了C端缺失了8个氨基酸残基突变的Gun4(Gun4L).酵母双杂交与GST-pull down实验发现,Gun4L仍能与H亚基相互作用,原核表达和纯化Gun4L和镁离子螯合酶各亚基后,重组镁离子螯合酶的酶活分析证实,Gun4L对镁离子螯合酶的活性失去了激活作用.

我国警察使用电击枪的法律规制

电击枪用于控制违法犯罪行为时具有低致命性、有效性和多功能性等特点。关于电击枪在警察武力体系中的法律定位存在致命性武力说和非致命性武力说两种观点。我国立法宜将其界定为非(低)致命性武力手段及独立的警械种类。对于我国警察使用电击枪的法律规制,需要明确立法形式和立法内容,对警察使用电击枪的情形、条件和程序作出明确细致的规定,充分发挥电击枪在警察现场执法中的使用效能。