带壳装药壳体厚度对混凝土爆破毁伤效果的影响

根据混凝土中爆炸冲击波初始压力经验公式和C-J爆轰理论,用AUTODYN软件对带壳装药在混凝土中爆炸进行数值模拟,计算了不同壳厚下爆炸冲击波的初始压力值,得到带壳装药混凝土中爆炸冲击波初始压力的拟合公式,分析了冲击波初始压力随壳体厚度与装药半径比的变化规律.另外,从爆炸能量和爆炸冲击波的比冲量两个角度分别研究了壳体厚度对混凝土毁伤效果的影响.结果表明:当壳厚为0.5 ～2 mm时,爆坑体积较裸装药时增大,毁伤效果也较好;但当壳厚大于2 mm时,爆坑体积逐渐变小,毁伤效果也将变差.     

起爆方式对柱形炸药空爆冲击波场的影响

为研究起爆方式对柱形炸药爆炸能量输出的控制效应,运用AUTODYN软件对不同起爆方式作用下的炸药在空气中爆炸过程进行了模拟。通过对比分析参考位置的冲击波超压峰值,得到了起爆方式对爆炸冲击波场分布的影响规律。研究结果表明:比例距离小于5 m·kg-1/3时,起爆方式可改变爆炸冲击波场的局部分布形态,其在不同的方向和距离对冲击波超压影响存在差异;比例距离大于5 m·kg-1/3时,起爆方式对冲击波场分布基本无影响;柱形炸药长径比一定的条件下,同一起爆方式作用下的爆炸相似律仍然成立。     

三向正交预制体织造参数对C/C复合材料性能的影响

以Z向间距不同的三向正交结构预制体为研究对象,采用化学气相渗透和浸渍树脂相结合的工艺制备碳/碳(C/C)复合材料,研究织造参数对C/C复合材料微观结构和弯曲性能的影响。以三向正交预制体最小的重复结构为单元建立计算模型,获得三向正交预制体纤维含量与织造参数的关系式并进行验证,结果表明：Z向纤维间距及X,Y向纤维层间距越小,预制体纤维含量越高;Z向纤维间距越大,纤维交织处扭曲变形大,预制体孔隙结构发生变化;相同致密化工艺下,孔隙结构的变化影响C/C复合材料中基体碳的组成和分布,对基体碳形貌无影响;X,Y向纤维含量越高,Z向纤维间距越小,致密后的C/C复合材料弯曲强度越高。     

钢筋混凝土隔离墙抗爆性能数值模拟研究

为了研究钢筋混凝土隔离墙在爆炸荷载作用下的动态响应和抗爆性能,采用LS-DYNA有限元软件建立9 m跨度隔离墙结构简化模型,模拟了不同药量和爆炸距离下隔离墙的动态响应。将模拟结果与经验超压公式计算结果和已有试验结果对比,验证了爆炸荷载和材料参数选取的合理性,分析了结构的破坏过程、冲击波作用规律、墙面荷载分布规律和结构变形情况。结果表明:建立的数值模拟可以较好地模拟爆炸冲击波与结构的相互作用;墙面冲击波压力衰减速率与药量和爆炸距离密切相关,墙面压力衰减幅度可达97.8%。在相同药量时,随着爆炸距离增加,墙体底部压力减小,顶部冲量增加;墙体结构由小变形转变为结构整体的较大变形;比例距离小于0.376■时,墙体底部容易发生剪切破坏。模拟结果可以为抗爆隔离墙的设计提供依据。     

不同长径比柱形装药水下爆炸冲击波演化规律

为分析药柱形状对水下爆炸冲击波演化的影响。针对圆柱形装药中心起爆问题,在理论上建立了炸药与水交界面上初始冲击波压力及其传播方向的二维计算方法,借助于AUTODYN有限元计算程序开展了长径比1:2～10:1的圆柱形TNT在无限水域爆炸的数值模拟,并开展了长径比为1:1和2.6:1的圆柱形TNT的水下爆炸试验;对比理论、仿真和试验结果,验证了理论模型的合理性和数值模拟的有效性,分析了柱形装药水下爆炸冲击波的传播规律,重点分析了药柱长径比对不同爆距处冲击波压力分布及传播方向的影响。结果表明：圆柱形装药水下爆炸后,冲击波波阵面逐渐从柱形趋向椭球型再趋向球型,当冲击波传播至10倍无量纲爆距时高压区的转移结束;当长径比大于1:1时,炸药轴向(端面)的冲击波压力衰减速率大于径向(圆柱面)的衰减速率,冲击波峰值压力随着方向角的增大而单调增长;在1:1～5:1的长径比和20倍无量纲爆距范围内,增大药柱长径比可定向增强炸药径向的冲击波压力,药柱的形状对冲击波压力分布影响随着爆距增大而减小。     

凹陷地形对固体推进剂近地爆炸冲击波影响的数值分析

固体火箭发动机推进剂爆炸冲击波超压测试试验中,爆炸后地形的改变会使冲击波的传播过程和压力分布发生改变,导致超压测量结果小于理论计算结果。为了研究推进剂爆炸后地形结构对冲击波压力的影响,利用Autodyn软件使用Lagrange/Euler耦合的方法,计算了距离地面高度为1 m的950 kg推进剂在平整和凹陷两种地形工况下,爆炸冲击波的压力分布和贴地位置冲击波的超压曲线。结果表明,当推进剂下方存在凹陷地形时,地形的反射作用使推进剂爆炸形成的半球状冲击波波面压力在半球的上侧较高,而在半球的近地侧较低;而推进剂下方平整时,推进剂爆炸形成的半球状冲击波在半球近地侧较高,而在半球上侧较低。推进剂下方有凹陷地形时,爆炸形成的冲击波在贴地位置的压力比推进剂下方平整时小,同一贴地测点的冲击波到达时间也滞后。推进剂下方有凹陷时,爆炸冲击波超压曲线小于推进剂下方地形平整的超压曲线,这个结果解释了工程试验中大炸坑的推进剂爆炸超压试验中,超压的实测数据小于理论计算和数值仿真的现象。     

装药壳体对含铝炸药水下爆炸性能影响研究

针对某含铝炸药,分别在6 mm钢壳、硬铝壳、PVC壳及裸药柱形装药条件下进行水下爆炸实验,测量3 m,5 m,7 m处冲击波压力时程曲线,获得不同装药条件下冲击波的峰值、冲量、能量及气泡脉动周期和气泡能等参数。利用AUTODYN-2D程序,对带壳装药含铝炸药水下爆炸过程进行数值模拟,通过与实验测量结果对比,验证数值仿真方法和结果的准确性。在此基础上,结合量纲分析与数值模拟方法研究填装比对冲击波波形、压力峰值及气泡脉动周期的影响规律。研究表明：填装较小时,冲击波压力峰值与冲击波能均增大;填装较大时,压力峰值与冲击波能均减小;气泡脉动周期随填装比的增加而减小;在钢壳装药下,最优填装比为1.45。有限元模型与计算结论可为水中兵器设计提供一定参考。     

基于深度学习的爆炸冲击波信号重构模型

针对爆炸冲击波信号重构问题,引入深度卷积神经网络（DCNN）捕捉冲击波信号的局部信息和高阶特征,引入双向长短期记忆网络（Bi-LSTM）捕捉冲击波超压数据时序依赖关系,进而构建了基于深度学习的爆炸冲击波信号重构模型。相关实验研究表明,本文构建的爆炸冲击波信号重构模型,综合考量了信号的时序关系、频谱特征、数据变化规律等特征信息;在基于有限测点数据的冲击波场压力分布重构实验中,模拟和实测超压峰值平均误差分别为3.53%和13.71%,正压作用时间平均误差分别为7.35%和14.26%,比冲量平均误差分别为4.02%和11.92%;在基于残缺数据的冲击波压力曲线重构实验中,模拟和实测信号重构的缺失值与原始值基本吻合,且偏差均在0附近;均满足爆炸冲击波压力重构指标要求。研究结果对爆炸冲击波信号重构有重要指导意义。     

超重力场下球形炸药水下爆炸实验及数值模拟

常重力条件下,Mach数和Froude数无法同时满足相似。采用离心模型实验,研究水下爆炸冲击波特性及气泡脉动规律,并采用数值模拟方法重现了超重力场下的水下爆炸过程。实验及数值模拟的结果表明,重力的改变基本不影响冲击波的峰值,COLE理论在超重力环境下仍然适用,而超重力场下,小当量炸药可以模拟气泡的脉动迁移过程,其结果可以用于预测大当量炸药深水爆炸的特性。此外,为减少计算时间并提高计算精度,采用将二维冲击波作为初始条件映射到三维模型的建模方法。对于冲击波计算,网格尺寸宜取药包半径的1/20¹/10;对于气泡脉动,宜取药包半径的1/21/10;对于气泡脉动,宜取药包半径的1/2¹。     

EPS缓冲材料衰减水下爆炸能量的实验研究

为了研究缓冲材料EPS对水下爆炸能量的衰减作用,在爆炸水池内起爆有EPS包裹的雷管,采用压力传感器测量水下固定爆心距点爆炸冲击波,采用振动传感器测量实验水池近地面固定点振动。结果表明：EPS缓冲柱体半径按梯度增大,压力测点冲击波超压、比冲击波能以及振动测点竖直方向振动速度都衰减显著;在缓冲柱体半径R≥80 mm时,水下爆炸脉动波弱化或消失;增加EPS缓冲材料的密度,可有效衰减压力测点爆炸能量,但对振动测点速度衰减影响较小;压力测点爆心距增加,测得爆炸能量减小,但能量衰减率不一定因有EPS材料缓冲而提升。导出式(1)可根据实际防设点的爆心距和药包半径来近似设计水下爆炸EPS缓冲材料厚度和密度。     

A 3.2 kHz, 14-Bit Optical Absolute Rotary Encoder With a CMOS Profile Sensor

We have developed a 3.2 kHz, 14-bit optical absolute rotary encoder system using a profile sensor and a slit disc. The profile sensor, which we have designed for this purpose, is a unique CMOS area image sensor aimed at high-speed position detection of X and Y axes. Y axis profile data from the profile sensor is used for recognition of an index code on the slit disc, and X axis profile data is used for position detection of the index code. This combination of two-axis information enables high resolution even with a small number of index codes (64 indexes) and a small amount of digital calculations. Experimental results show that this system can detect rotation with an angular resolution of 14 bits (0.022deg) and a maximum detection speed of 3.2 kHz.     

Nonlinear isotropic constitutive laws: choice of the three invariants, convex potentials and constitutive inequalities

The aim of this paper is a new formulation of nonlinear isotropic constitutive laws. Our main hypothesis claims that the eigenvalues of stress and strain tensors are classified in the same order (the eigenvector associated to the highest eigenvalue of the stress tensor is also associated to the highest eigenvalue of the strain tensor, etc.). Further, we assume the existence of a differentiable convex isotropic potential. By introducing three new invariants for each tensor (called X, Y, Z for the stress tensor S and x, y, z for the strain tensor E) a constitutive law is revealed to be a simple duality between the chosen invariants: (x, y, z) and (X, Y, Z) look like Cartesian coordinates of E and S. We look at several potentials chosen as polynomials of these invariants. Finally, first and third order isotropic elasticity laws are reviewed and convexity of the potentials is discussed.     

Some concepts concerning twinning and cellular growth of bulk barium metaborate (BBO) crystals

Bulk single β-BaB₂O₄ (BBO) crystals have been grown by the TSSG method in Czochralski variant, using Na₂O and NaF as the solvents. It was found that formation of twins (electric type) or cellular substructures of different scales is their specific growth feature. We believe that their formation is governed by changes in the composition and structure of the double-electric layer (DEL) at the interface of crystal growth. In Z-axis crystals only microtwins structures were revealed whose number and localization are determined by the composition of used solvent. The cellular growth of these crystals at a particular stage is a result of the impossibility of frontal formation of an antipolar structure (macrotwin) under the conditions of increasing charge density in the DEL. In the Y(X-)-axis crystals the conditions for formation of one or three (five, etc.) macrotwin boundaries and, hence, noncellular growth are always realized. Model concepts, characterizing seeding and growth of Y(X-)- and Z-axis BBO crystals are discussed.     

烧蚀型面结构对CVI+HPIC工艺制备针刺C/C喉衬等离子烧蚀性能的影响

以碳纤维无纬布/碳纤维网胎叠层针刺预制体为增强体, 经化学气相渗透(CVI)联合沥青高压碳化(HPIC)工艺制备了热解碳+沥青碳双元基针刺C/C喉衬材料, 利用X射线断层扫描(μ-CT)和扫描电镜(SEM)表征了材料的微观结构, 采用等离子烧蚀试验考察了针刺喉衬材料X-Y纤维铺层面(0°)、Z向针刺面(90°)以及两者间过渡层面(23°、45°和68°)的烧蚀性能。结果表明, 采用CVI+HPIC组合工艺能使针刺材料达到高致密态, 获得了孔隙率仅为4%的C/C材料, 材料内部孔隙呈离散态分布, 其中98%的孔隙为小于20 μm的小孔。烧蚀结果显示, 针刺C/C材料不同区域的烧蚀性能存在差异, 从X-Y层面(0°)到Z向针刺面(90°), 其耐烧蚀性能呈先增强后减弱的趋势, 68°层面耐烧蚀性能最好, 线、质量烧蚀率分别为0.056 mm/s、0.050 g/s。烧蚀面纤维的排布是影响烧蚀性能的关键因素, 68°层面因形成的尖端烧蚀模式占比较高, 表现出最佳的耐烧蚀性能。     

D-optimal mixture design: optimization of ternary matrix blends for controlled zero-order drug release from oral dosage forms

The objective of the present study was to develop a tablet formulation with a zero-order drug release profile based on a balanced blend of three matrix ingredients. To accomplish this goal, a 17-run, three-factor, two-level D-Optimal mixture design was employed to evaluate the effect of Polyox^™ (X₁), Carbopol® (X₂), and lactose (X₃) concentrations on the release rate of theophylline from the matrices. Tablets were prepared by direct compression and were subjected to an in vitro dissolution study in phosphate buffer at pH 7.2. Polynomial models were generated for the responses Y₄ (percent released in 8 h) and Y₆ (similarity factor or f₂). Fitted models were used to predict the composition of a formulation that would have a similar dissolution profile to an ideal zero-order release at a rate of 8.33% per hour. When tested, dissolution profile of the optimized formulation was comparable to the reference profile (f₂ was 74.2, and n [release exponent] was 0.9). This study demonstrated that a balanced blend of matrix ingredients could be used to attain a zero-order release profile. Optimization was feasible by the application of response surface methodology, which proved efficient in designing controlled-release dosage forms.     

Reliability models based on bivariate exponential distributions

Motivated by reliability applications, we derive the exact distributions of R=X+Y and W=X/(X+Y) and the corresponding moment properties when X and Y follow five flexible bivariate exponential distributions. The expressions turn out to involve several special functions.     

On asymptotic behavior of oscillatory solutions of operator differential equations perturbed by a fast Markov process

We study the asymptotic behavior of the distributions of the solution of the differential equation of the form

in a separable Hilbert space H where y(t) is an ergodic homogenous Markov process in a measurable space (Y, C) satisfying some mixing conditions and A(y), y Y is a family of commuting closed linear operators with the same dense domain. Using the spectral representation of the solution we construct an H-valued process û_ε(t) which is expressed in terms of the solution of the averaged equation

where = ƒ A(y)(dy) and is the ergodic distribution of Y(t), and some Gaussian random fields with independent increments. We show that the distributions of u_ε(t/ε) and û_ε(t) asymptotically coincide.     

Liapunov stability and adding machines revisited

We give a revised proof of a theorem originally due to Buescu and Stewart (1995). The new version of this theorem dispenses with the assumption that the space X is locally compact. The theorem is as follows: let X be a locally connected metric space, let f,:,X→X be a continuous map, and let A⊂X be a Liapunov stable compact transitive set that has infinitely many connected components. Then the map induced by f on the space of connected components of A is topologically conjugate to an adding machine.     

爆炸荷载作用下覆土库外部冲击波传播规律

为了研究爆炸荷载作用下覆土库外部冲击波的传播规律,采用有限元软件ANSYS/LS-DYNA,结合将覆土库结构破坏与冲击波传播先后模拟的新手段,对覆土库外部距爆心比例距离小于15 m/kg^(1/3)范围内空气冲击波的传播过程进行模拟,并对模拟所得不同测线方向(0°、60°、90°、135°和180°)冲击波峰值超压和冲击波到达时间进行分析。结果表明:测点距爆心比例距离在1～15 m/kg(1/3)范围内空气冲击波的传播过程进行模拟,并对模拟所得不同测线方向(0°、60°、90°、135°和180°)冲击波峰值超压和冲击波到达时间进行分析。结果表明:测点距爆心比例距离在1～15 m/kg^(1/3)范围内,随比例距离的增大,在60°和90°测线方向,冲击波峰值超压衰减率从87.63%降到26.39%;在135°和180°测线方向,冲击波峰值超压衰减率从81.19%降到1.39%。随着测点距爆心比例距离的增大,冲击波峰值超压呈指数型衰减,冲击波到达时间呈线性增加。