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.

One-step green method to prepare progressive burning gun propellant through gradient denitration strategy

Gradiently denitrated gun propellant(GDGP)prepared by a“gradient denitration”strategy is obviously superior in progressive burning performance to the traditional deterred gun propellant.Currently,the preparation of GDGP employed a tedious two-step method involving organic solvents,which hinders the large-scale preparation of GDGP.In this paper,GDGP was successfully prepared via a novelty and environmentally friendly one-step method.The obtained samples were characterized by FT-IR,Raman,SEM and XPS.The results showed that the content of nitrate groups gradiently increased from the surface to the core in the surface layer of GDGP and the surface layer of GDGP exhibited a higher compaction than that of raw gun propellant,with a well-preserved nitrocellulose structure.The denitration process enabled the propellant surface with regressive energy density and good progressive burning performance,as confirmed by oxygen bomb and closed bomb test.At the same time,the effects of different solvents on the component loss of propellant were compared.The result showed that water caused the least component loss.Finally,the stability of GDGP was confirmed by methyl-violet test.This work not only provided environmentally friendly,simple and economic preparation of GDGP,but also confirmed the stability of GDGP prepared by this method.

Development and simulation of a gridded thermionic cathode electron gun for a high-energy photon source

A gridded thermionic cathode electron gun was developed for the linear accelerator of the High Energy Photon Source(HEPS).An electron gun should provide a large maximum bunch charge with a wide adjustable range.To satisfy these requirements,the shape of the electrode was optimized using a multi-objective genetic algorithm.A large bunch charge with an adjustable range was achieved using the grid-limited gun,the flow of which was analyzed using 3-D simulations.The electron gun has been manufactured and tested,and the measured data of the grid-limited current and simulation results are compared and discussed in this study.

Analysis of Corrosion Mechanisms of Low-cement or No-cement Al_(2)O_(3)-MgO Gunning Mix with Special Calcined Alumina in Rotary Slag Test

Al_(2)O_(3)-MgO and Al_(2)O_(3)-spinel low cement castables(LCC-AM and LCC-AS)have been extensively used in steel ladles as working linings.Nevertheless,the use of alumina-magnesia gunning mixes has been mainly kept for maintaining these castable linings,because of high rebound loss,poor green strength,high porosity and short life-span.Thanks to a high BET alumina(MC-G),it is now possible to develop a series of high-performance no-cement or low-cement Al_(2)O_(3)-MgO gunning mixes(NCG-AM or LCG-AM).The paper focuses on the BOF slag resistance of NCG-AM,LCG-AM,LCC-AM and LCC-AS.The corrosion mechanisms of rotary slag samples were studied by scanning electron microscopy(SEM/EDS).The results reveal different microstructures around MgO particles,depending on the four used compositions.Continuous and thicker spinel phases were formed in NCG-AM,which was proved to have the best corrosion resistance after the dynamic slag test.MC-G can provide a high diffusion flux of Al^(3+)in terms of kinetics and hence inhibits Kirkendall porosity around MgO particles.In addition,a continuous spinel phase acts like a pinning nail to reinforce the matrix and thus decreases erosion by slag.In contrast to NCG-AM,the porous spinel phase was found around unreacted MgO particles and some particles were carried away near the interface of LCC-AM and slag.The NCG-AM containing MC-G had been tested in two steel plants,and it extended the service life of the ladles up to 50%.In addition,this study suggests the potential application of NCG-AM as steel ladle linings.

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.

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。

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.

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。

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.

Comparative analysis of the effects of gunpowder and plasma ignition in closed vessel tests

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of a single-base gun propellant,as determined via closed vessel tests.Conventional gunpowder ignition and plasma jet ignition methods were used,and differences in the ignition time were analysed.The influence of the ignition method on the dynamic vivacity is discussed.It is shown that this influence is significant in the first phase of the combustion process,and with respect to the low values of the loading density.In the second phase of the combustion process,and for large values of the loading density,the dynamic vivacity plots for the two ignition methods converge.Regarding the burning law,close values of the exponent were obtained for the two ignition methods.The dynamic vivacity plots determined for plasma ignition reveal stronger dependence on the loading density than those determined for gunpowder ignition.The conclusion is that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants,which results in deviation of the burning process from the geometric burning law.

A Comparative Study on the Excitation of Large Volume Airgun Source with Different Combinations in Hutubi,Xinjiang,China

In order to study the excitation of large-volume airgun source with different combinations in Hutubi,Xinjiang,China,we conducted a targeted experiment.The method of timefrequency analysis is used to study the signals recorded by a seismometer on the shore of the excited pool,and it is concluded that different gun combinations will lead to different frequency of bubble pulse signals.Besides,linear combination method is used to analyze the signal-to-noise ratios of signals excited by different gun combinations which was recorded by seismic stations around the airgun source.In order to improve the signal-tonoise ratios,it is more effective to increase the activation energy(the number of excited guns at the same time)than to stack the excited signals with smaller energy repeatedly.

The Time-frequency Characteristic of a Large Volume Airgun Source Wavelet and Its Influencing Factors

Through analyzing the near-field hydrophone records of the airgun experiment in the Jiemian reservoir,Fujian,we study the time-frequency characteristic of airgun source wavelet and the influence of gun depth and firing pressure,and explain the process of bubble oscillation based on the Johnson( 1994) bubble model. The data analysis shows that:( 1) Airgun wavelet is composed of primary pulse and bubble pulse. The primary pulse,which is of large amplitude,short duration and wide frequency band,is usually used in shallow exploration. The bubble pulse,which is concentrated in the low-frequency range,is usually used in deep exploration with deep vertical penetration and far horizontal propagation.( 2) The variation of primary pulse amplitude with gun depth is very small,bubble pulse amplitude and the dominant frequency increase,and peak-bubble ratio and bubble period decrease. When the gun depth is 10 m,primary pulse amplitude and peakbubble ratio are maximum,which is suitable for shallow exploration; when gun depth is25 m,bubble pulse amplitude is large, and peak-bubble ratio is minimum, which is suitable for deep exploration.( 3) The primary pulse amplitude,bubble pulse amplitude,peak-bubble ratio,and bubble period increase and the dominant frequency decreases with increased firing pressure.

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.

基于GUN工具的嵌入式软件编译体系的设计与实现

提出一种使用GUN工具构建可靠灵活的编译体系的理论和方法。首先分析了需求,并且根据需求,系统的阐述构建该编译体系的原理、原则和方法。

Beam and image experiment of beam deflection electron gun for distributed X-ray sources

Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.

Formation and corrosion behavior of Fe-based amorphous metallic coatings prepared by detonation gun spraying

Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of thermally sprayed deposits with the porosity below 2%. Both crystallization and oxidation occurred obviously during spraying process, so that the amorphous fraction of the coatings decreased to 54% compared with fully amorphous alloy ribbons of the same component. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings exhibit extremely wide passive region and low passive current density in 3.5% NaCl (mass fraction) and 1 mol/L HCl solutions, which illustrates excellent ability to resist localized corrosion.

Experimental Simulation for Fracture of Gun Propellant Charge Bed

The simulation of compression and fracture of charge bed in chamber is one of the key problems in the study of launch safety of gun propellant charge. A new kind of experimental device that can be used for simulation is given. Its structure and operational principle are introduced. Using a semi-closed vessel as a source of compression force, the device can simulate any kind of dynamic environment in a gun propellant charge. Using the low temperature inert gas （N2） as the compression medium, the device can not only ensure that the simulation is real, but also protect the fragmentized propellant from combustion after experiment. Using the device, many simulation experiments have been accomplished, and dynamic environment of propellant fracture is acquired. With the experiments, fragmentized propellant for the compression and fracture of charge bed is obtained. Results of experiments show that the new device can be used to study the principle of the compression and fracture of charge bed.