Preliminary discussion on the ignition mechanism of exploding foil initiators igniting boron potassium nitrate

Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.

A micro-chip exploding foil initiator based on printed circuit board technology

Conventional exploding foil initiator (EFI) in ignition or detonation applications hosts many performance advantages, but was hindered by the bulky, inaccurate, inefficient and expensive shortcomings. We highlight a novel micro-chip exploding foil initiator (McEFI) using printed circuit board (PCB) technology. The structural parameters were determined based on energy coupling relationship at the component interfaces. Next, the prototype McEFI has been batch-fabricated using PCB technology, with a monolithic structure of 7.0 mm (l) × 4.5 mm (w) × 4.0 mm (δ). As expected, this PCB-McEFI illustrated the successful firing validations for explosives pellets. This paper has addressed the cost problem in both military munitions and civil markets wherever reliable, insensitive and timing-dependent ignition or detonation are involved.

Optimization Design of Exploding Foil Bridge Shape

The exploding foil,which is a main influence factor of exploding foil initiator(EFI),was studied to improve the utilization rate of energy in EFI.The burst currents of three bridge foils with different shapes were measured,and the sensitivity of initiation charge made of HNS-IV was tested by slappers.The test results show that,for O-shaped bridge foil,the burst current density is maximal,and the initiating voltage at 50% of firing probability of HNS-IV is minimal.The O-shaped bridge foil can be used to improve the utilization rate of energy in EFI and reduce the firing energy.

EXCITATION OF SPHERICAL SYMMETRIC EXPLODING WAVE WITH MOVING BOUNDARY

In this paper we have given an analytic excitation solution of exploding wave in infinite elastic body with growing spherical inner boundary, and the convergence region of series in this solution determined. Some characters of the displacement wave have also been discussed.

Expansion of Plasma of Electrically Exploding Single Copper Wire Under 4.5kA～9.5kA/Wire

The experimental system for electrically exploding single metal wire has been designed and manufactured. Expansion of the dense plasma column formed from an electrically exploding Cu wire of diameter 30 μm has been studied with a high-speed photographer to obtain the time-dependent radius (R-t) curve. The experimental results demonstrate that the mean expansion rate of the dense plasma column is 1.94 μm/ns, 2.6 μm/ns and 3.75 μm/ns according to the peak pulse current 4.5 kA, 7 kA and 9.5 kA respectively. The results can be beneficial to giving a profound understanding of the early stage of wire-array Z-pinch physics and to improvement on their design.

Migrated Exploding Reflectors in Evaluation of Finite Difference Solution for Inhomogeneous Seismic Models

Earth is inhomogeneous, which means its elastic characteristics change with depth. The seismic method employs the propagation of waves throughout the earth to locate different structures and stratigraphy. Understanding the wave propagation is an important matter in exploration seismology;therefore modeling of seismic wave is an important tool. To validate the interpreted earth model out of the seismic data, seismic synthetic seismograms should be generated in a process named “seismic forward modeling”. Finite difference method is used as one of the most common numerical modeling techniques. In this paper the accuracy of finite difference method in seismic section modeling is explored on different modeled data set of heterogeneous earth. It is shown that finite difference method completes with migration to reposition the events in their correct location. Two different migration methods are used and various velocities are also tested to determine an appropriate migration velocity. Finally the validly of finite difference modeling is examined using a 2D structural similarity index technique.

Electrothermal energy conversion mechanism of micro-scale semiconductor bridge

The response characteristics of resistance is observed by the analysis of experimental data of micro scale semiconductor bridge （MSCB） under different voltage inputs. Two critical voltages are found. One is called exploding voltage, above which the MSCB can be melted and vaporized without generating a plasma, and the other is called producing a plasma voltage, above which the MSCB is entirely vaporized, and then the current flows through the vapor producing the plasma. Based on the non Fourier heat conduction theory, the electrothermal energy conversion model is es tablished for the stage from heating to exploding, and then the correlation of MSCB and time is ob tained by graphic calculation. Importantly, the critical exploding voltage and exploding time are also derivate. With the comparison between the analytical result from the theoretical model and that from experimental data, it has been demonstrated that the theoretical model is reasonable and feasible for designing the exploding voltage and exploding time.

Characteristics of a plasma flow field produced by a metal array bridge foil explosion

To improve the energy utilization efficiency of metal bridge foil explosion, and increase the function range of plasmas, array bridge foil explosion experiments with different structures were performed. A Schlieren photographic measurement system with a double-pulse laser source was used to observe the flow field of a bridge foil explosion. The evolution laws of plasmas and shock waves generated by array bridge foil explosions of different structures were analyzed and compared. A multi-phase flow calculation model was established to simulate the electrical exploding process of a metal bridge foil. The plasma equation of state was determined by considering the effect of the changing number of particles and Coulomb interaction on the pressure and internal energy. The ionization degree of the plasma was calculated via the Saha-Eggert equation assuming conditions of local thermal equilibrium. The exploding process of array bridge foils was simulated, and the superposition processes of plasma beams were analyzed. The variation and distribution laws of the density, temperature, pressure, and other important parameters were obtained. The results show that the array bridge foil has a larger plasma jet diameter than the single bridge foil for an equal total area of the bridge foil. We also found that the temperature, pressure, and density of the plasma jet＇s center region sharply increase because of the superposition of plasma beams.

On New Solutions of Classical Yang-Mills Equations with Cylindrical Sources

Strong fields generated by big electric currents are examined within the framework of the Yang-Mills nonlinear generalization of the Maxwell electrodynamics proposed in our earlier papers. First we consider the case of stationary currents and find a new exact solution to the Yang-Mills equations. Then we study a Yang-Mills field inside a thin circular cylinder with nonstationary plasma and find expressions for field strengths in it. Obtained results are applied to interpret several puzzling natural phenomena.

Similarity of Rayleigh-Taylor Instability Development on Scales from 1 mm to One Light Year

In this paper, we describe three different phenomena occurring on scales of 1 mm, 100 km, and almost a light year. The smallest scale is a laboratory experiment. The intermediate scale is a rocket-borne space experiment and the largest is an exploding star. In each case, deceleration creates a situation that is unstable to the Rayleigh-Taylor instability. The similarity exists in the spatial and in the Fourier domains;that is, not only are there obvious spatial similarities but the power spectra of the two phenomena are also nearly identical. The data compare favorably to published simulations.

Effect of change of sand properties on travel distance of ricocheted debris

The debris from exploded buildings can ricochet after colliding with the ground,thus increasing the debris travel distance and danger from any associated impacts or collisions.To reduce this danger,the travel distance of ricocheted debris must be accurately predicted.This study analyzed the change in the travel distance of ricocheted concrete debris relative to changes in the properties of a sand medium.Direct shear tests were conducted to measure the change in internal friction angle as a function of temperature and water content of the sand.Finite element analysis(FEA)was then applied to these variables to predict the speed and angle of the debris after ricochet.The FEA results were compared with results of low-speed ricochet experiments,which employed variable temperature and water content.The travel distance of the debris was calculated using MATLAB,via trajectory equations considering the drag coefficient.As the internal friction angle decreased,the shear stress decreased,leading to deeper penetration of the debris into the sand.As the loss of kinetic energy increased,the velocity and travel distance of the ricocheted debris decreased.Changes in the ricochet velocity and travel distance of the debris,according to changes in the internal friction angle,indicated that the debris was affected by the environment.

基于PHP的成绩快速输入系统的设计

教师往往需要将学生完成作业的情况输入到电子表格中。但是,由于原始文档中存在多个班级,学生完成作业的顺序较为混乱,且数据量较大,直接输入费时费力。针对该问题,提出利用PHP设计成绩快速输入系统的解决思路。首先将学生的学号信息导入到MySQL数据库,然后通过PHP页面的文本框接收输入的学号字符串并自动增加新的作业字段,接着通过explode函数对字符串进行分割并提取学号,再根据学号与数据库对比更新当前作业所在字段,最后将数据表导出到电子表格。实践表明,该系统运行速度较快,稳定可靠,能够极大地提高工作效率。

Huge Star Explodes in Brightest Supernova Yet Seen

在浩瀚的宇宙空间,一颗比我们的太阳重150倍的恒星发生爆炸,结果是形成了一个超新星。令人稍感不安的是,爆炸点离我们的银河系和地球并不很遥远。

The Worn-out Power Battery Recycling Market About to Explode

Although a number of new energy automobile enterprises promise consumers that the battery’s service life and quality guarantee period may last about 10 years,the average life expectancy of power batteries is in fact more than 5 years if considering the usage environment and other factors.This means that the power battery recycling market is about to explode in 2018.