Simplified analysis for reflective overpressure on walls of rectangle-section tunnel due to its inner-explosion

Based on the constructing thought of the displacement model of isoparametric finite element, an extended interpolating algorithm is deduced for calculating the overpressure history of an optional point on the walls of the rectangle-section tunnel under an optional point-explosion in its internal space. According to the working principle, the overpressure histories of all nodes on the walls of a tunnel with the equal width and height of 2 m, induced by a reference-charge explosion at each node in this tunnel's cross section, are computed using the LS-DYNA software, and then are gathered to establish a reference database, which makes it possible to set optionally the positions of the explosive and the overpressure-observed point. In addition, some variation factors of peak values and durations of overpressure on the walls, reflecting some changes on the charge weight and the sizes of width and height of the section, are included in this algorithm in order to simulate approximately the overpressure responses on the walls under the optional charge weight and cross-section size. Some example analyses indicate the rapidity and validity of this method, and therefore this will bring it a good prospect in engineering application.     

Effect of Shock Wave on Fabricated Anti-Blast Wall and Distribution Law Around the Wall Under Near Surface Explosion

The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM.The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites,as well as in the comparison between the test and numerical calculation.The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m,the distribution of overpressure behind wall was gained according to variety law based on small-large-small.It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5--2.5 multiples,and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall.     

小药量作用下框支玻璃防爆距离的爆炸试验

在发生爆炸时作为建筑外墙装饰的玻璃首先受到冲击作用,本文分析小药量作用下框支玻璃的安全距离确定方法,并且进行了爆炸荷载作用下框支玻璃的抗爆性能的试验研究.最后提出了小药量爆炸下国内关于玻璃抗爆安全距离计算公式偏保守和可以用爆炸冲击波超压峰值来确定玻璃抗爆安全距离.     

Analysis of blast wave propagation inside tunnel

The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure.     

Experimental Study of Structure Shock Vibration in Soft Caused by Explosion of Conventional Weapons

When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments, The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure.     

Numerical and Experimental Investigation into Plane Charge Explosion Technique

Plane charge explosion technique (PCET) is one of the major techniques frequently used in large-scale blast-resistant structure tests. An FEM model was established, which can simulate the process of air releasing from the blast cavity. The effects of the charge density, the interval of the charge strip, the distance of the charges from the structure, and the mass of backfill soil on the overpressures applied on the tested structures were analyzed by the FEM model. The quantitative relationships between the peak value and the duration of the overpressure and the above-mentioned affecting parameters were established. Agreement between numerical results and the test data was obtained.     

Simulation of Airblast Load and Its Effect on RC Structures

In the analysis of a structure subjected to an explosion event, the determination of the blast load constitutes a crucial step. The effect of the blast load on the structure depends not only on the peak shock overpressure, but also the impulse (hence the duration). For structures with a regular geometry, the blast load may be fairly well estimated using appropriate empirical formulae; however, for more complex situations, a direct simulation using appropriate computational techniques is necessary. This paper presents a numerical simulation study on the prediction of the blast load in free air using a hydrocode, with focus on the sensitivity of the simulated blast load to the mesh grid size. The simulation results are compared with empirical predictions. It is found that the simulated blast load is sensitive to the mesh size, especially in the close-in range, and with a practically affordable mesh grid density, the blast load tends to be systematically underestimated. The study is extended to internal blast cases. An example concrete slab under internal explosion is analyzed using a coupled analysis scheme. The internal blast load from the simulation is examined and the response of the RC slab is commented.     

Experimental Study of Structure Shock Vibration in Soil Caused by Explosion of Conventional Weapons

When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments. The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure.     

爆炸冲击作用下拱顶式储油罐结构的动力响应(英文)

为研究大型钢制拱顶式储油罐在可燃气体爆炸作用下的破坏和变形特征,对多个储油罐缩比模型进行爆炸实验. 并利用 ANSYS/LS-DYNA 软件,建立了缩比为 1: 25 的 5 000 m3储油罐数值模型,对模型在爆炸冲击作用下的破坏过程进行数值模拟. 实验与数值结果表明: 爆炸冲击波对储油罐缩比模型具有瞬间突跃增压的冲击特性,罐壁迎爆面驻点区域超压峰值最高; 迎爆面中部驻点区首先屈服并带动相邻部分达到屈服状态,同时在变形区周围明显形成不规则的塑性铰环,导致罐壁产生内凹屈曲. 在此过程中,罐内液体既对罐壁产生一定的冲击作用,也能吸收和耗散部分爆炸能量.     

砖混房屋顶层墙体裂缝原因及预防措施

针对我国目前砖混房屋顶层墙体出现的裂缝问题,从理论和施工上进行了分析,主要概括为荷载,温度变化,不均匀沉降等几种原因,探讨预防开裂的几种控制措施:设计人员必须严格按规范进行设计,施工人员认真抓好施工中每一个环节,把好质量关、材料关,注意施工程序和特殊部位构造处理。     

Test and Analysis of an Existing Tunnel Vibration Induced by Blasting Construction of Diaphragm Wall

According to the blasting construction of the diaphragm wall of Puxi approaching section of East Fuxing Road river-crossing tunnel,the monitoring project of the vibration of the existing tunnel induced by the blasting construction is put forward,which includes the sensors' location,monitor method and the vibration monitoring system.Based on the monitoring data of the explosion vibration,the vibration wave forms,velocities,acceleration responses,main frequencies and fields of measure points are analyzed under the conditions of three locations and different charge quantities.According to the safety-judging standard of explosion vibration,the conclusion that the existing tunnel is safe under the explosion vibration is then drawn.Furthermore,the spectrum characteristics of three explosion vibrations and the spectrum changing properties of explosion vibration wave transmitting in different directions are concluded,which can provide reference to similar projects.     

求解单调变分不等式的两类近似邻近点算法比较

将Solodov和Svaiter于2000年发表的Error bounds for proximal point subproblems and associated inexact proximal point algorithms一文中提出的方法进行推广,得到2类近似邻近点算法．这2类算法都是预测校正方法,预测点满足相同的非精确准则,不同之处在于校正步的下降方向．为了使每次迭代产生的迭代点更加靠近解点,在校正步均采用了最优步长的技巧．在一定条件下,可以证明这2种邻近点算法是全局收敛的．并且,从理论上证明了采用算法2每一步所产生的下降量的下界大于算法1的,所以算法2比算法1能更快地收敛到解点．数值试验也表明了这一点．     

带电圆环点电荷系统振动分析

利用电磁学理论建立了带电圆环点电荷系统振动方程,讨论了系统在不同条件下的稳定性,对非线性振动系统,利用Maple计算绘图,分别作出了回复力和能量随位移的变化曲线、相图,求出了非线性振动系统的周期．     

导电椭球与点电荷间的相互作用

本文采用基于电势多极展开的电像法求解像电荷的大小、位置和系统在空间中的电势．计算了带电导体椭球与点电荷之间的相互作用力．     

Resuspension of wall deposits in spray dryers

Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.     

用Dijkstra算法求解最优切割方式的模型

从待加工的长方体中加工出一个已知尺寸、位置预定的长方体，需寻找一种最优切割方式，利用图论中的Dijkstra算法可得到上述问题的数学模型和求解方法，同时对一组具体数据给出了最优解并进行了讨论，     

基于Diffserv模型的队列调度加权优化算法

在Diffserv模型的基础上提出了一种基于WRR调度算法的加权优化算法，给出了该算法的实现方法．加权优化算法是根据网络中各业务数据的实际流量动态的调整其对应的权值。还能根据该节点的实际负载状况，提供动态的带宽分配。     

Review:Resuspension of wall deposits in spray dryers

Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.     

Splitting PMMA with Mini Cutting Explosives

In order to improve the present aviation ejection escape system, the application of explosion cutting technique to aviation escape system is proposed to weaken the strength of canopy before ejecting it. A series of mini cutting explosives are designed to investigate the process of splitting PMMA plate. The phenomenon of spallation in PMMA is observed. The effects of different parameters of mini cutting explosives on the cutting depth are obtained. Consequently the appropriate material of half-circular metal covers, explosive types and the ranges of charge quantities are determined. On the other hand, the cutting process of aviation PMMA plate by mini cutting explosives is simulated by means of nonlinear dynamic analysis code LS-DYNA. In finite element analysis,Arbitrary Lagrangian Euler (ALE) algorithm is used to depict the fluid property of high energy explosives. Continuous damage material model is used to simulate the complicate dynamic damage behavior of PMMA due to explosion shock waves. Only sliding contact option is defined to fulfill the fluid-structure interaction between explosives and PMMA plate by distributed parameter methods. Phenomenon of spallation observed in the experiment is presented in the simulation. The relationship between the penetration depth of PMMA plate and charge linear density obtained by numerical simulation agrees well with experimental result.     

基于密码杂凑函数的安全规则匹配优化算法

随着防火墙、入侵防御系统等网络安全规则数目的快速增长,规则匹配效率成为影响网络安全设备性能的一个瓶颈。基于密码杂凑算法的随机性、低碰撞性等良好特性,设计了一种用于防火墙等网络安全设备的安全规则匹配算法。通过调整密码杂凑算法轮数、存储空间大小等参数,达到存储空间资源占用与实现效率的平衡。分析了规则数目、存储空间大小和发生碰撞概率之间的关系,以及软硬件实现的速度。该方案比以前的简单哈希算法碰撞概率低,适用于高性能防火墙等网络安全设备的性能优化和效率提升。