固定界面Level Set方法在爆轰波阵面传播中的应用

针对重新初始化造成的界面位置偏离问题,提出一种固定界面Level Set方法。该方法的基本思想是在重新初始化相邻两次迭代过程中,通过构建保持界面不动满足的条件,从而推导出光滑参数的计算公式。与传统Level Set方法相比较,固定界面Level Set方法将固定的光滑参数修正为变化的光滑参数。数值模拟结果表明：固定界面Level Set方法在重新初始化过程中能够很好地固定界面位置,从而提高Level Set方法的质量守恒性;固定界面Level Set方法能够有效地避免由于误差累积导致的爆轰波阵面偏离现象,具有较高的计算精度和分辨率,适用于求解爆轰波阵面传播问题。针对重新初始化造成的界面位置偏离问题,提出一种固定界面Level Set方法。该方法的基本思想是在重新初始化相邻两次迭代过程中,通过构建保持界面不动满足的条件,从而推导出光滑参数的计算公式。与传统Level Set方法相比较,固定界面Level Set方法将固定的光滑参数修正为变化的光滑参数。数值模拟结果表明：固定界面Level Set方法在重新初始化过程中能够很好地固定界面位置,从而提高Level Set方法的质量守恒性;固定界面Level Set方法能够有效地避免由于误差累积导致的爆轰波阵面偏离现象,具有较高的计算精度和分辨率,适用于求解爆轰波阵面传播问题。     

空中爆炸问题的高精度数值模拟研究

针对空中爆炸初期强间断和爆炸后期接触间断物理特性,提出了虚拟流体方法（GFM）和真实虚拟流体方法（RGFM）2种界面处理方法相耦合的计算方法。在高密度比、高压力比同时存在的 爆炸初期和压力、密度及速度等物理量相接近的爆炸后期,分别采用RGFM和GFM对物质界面两侧物理量进行处理。采用Local Level Set方法对运动界面进行追踪,并用5阶高精度加权本质非振荡（WENO）格式和3阶TVD Runge-Kutta方法对控制方程进行离散,编制了空中爆炸数值模拟程序,应用该程序对不同高度近地面空中爆炸以及冲击波与挡墙相互作用问题进行数值模拟,模拟结果能够较好地反映空中爆炸中冲击波的产生、传播、反射、绕射及爆炸产物的膨胀等现象,并与经验公式和试验结果吻合较好。证明了该耦合方法能够模拟空中爆炸问题,并且爆炸波在传播过程中具有很好的对称性,为模拟高密度比、高压力比的多物质之间相互作用问题提供了有效的计算方法。     

非理想爆轰波阵面传播的Level Set方法应用研究

为了较精确地对非理想爆轰波的传播进行计算,基于爆轰冲击波动力学(DSD)理论,研究了计算二维贴体坐标系中爆轰波阵面传播问题的Level Set方法。根据Ham ilton-Jacobi方程的Godunov差分格式,提出了非正交的贴体坐标系中Level Set函数方程的差分格式及其相应的数值方法。将Level Set方法应用于自行研制的二维流体动力学程序TDY2D得到编码TDY_DSD,对爆轰波的传播及爆轰驱动的实验模型进行了数值模拟计算,所得的计算值均与实验值符合较好。计算结果表明了TDY_DSD程序的正确性和有效性,具有较高计算精度。     

后缘射流对跨音速翼型激波振荡影响的数值模拟

跨音速翼型上激波与附面层相互干扰会导致激波在翼型上前后振荡,从而有可能引起机翼抖振。要对激波振荡进行控制主要应通过改变激波附面层相互作用区域的流动和后缘处尾流的流动来实现。通过数值方法模拟后缘射流对尾流流动的改变以及对跨音速翼型上激波振荡的影响。计算了不同射流速度下相对厚度为18%的双圆弧翼型绕流场,分析了后缘射流对激波振荡及翼型气动特性的影响。结果表明后缘射流对激波振荡有抑制作用,同时对翼型气动特性有一定改进作用。     

对称边界条件下轨道炮有限元／边界元仿真

基于deal．ii编写了电磁轨道炮有限元仿真程序,建立了拉格朗日运动坐标下电磁轨道炮的有限元仿真模型;通过使用有限元边界元耦合方法可以对电磁轨道炮的边界条件进行计算,而无需对轨道炮周边的空气划分网格,是一种处理电磁场边界问题的有效方法;但是,由于边界元方法,使用的是满秩矩阵,在三维情况下计算量大,利用轨道炮的对称性,使用对称边界条件,减少了参与计算的网格数目,从而减少计算量。     

基于RKDG方法的空中爆炸冲击波数值模拟

针对空中爆炸强间断模拟精度较低的问题,应用虚拟流体方法(GFM)处理高密度比、高压力比存在的爆炸流场中物质界面处两侧的物理量。采用Level Set方法对运动界面进行追踪,采用间断伽辽金法对控制方程在空间上进行离散,采用龙格库塔方法在时间上离散。编制空中爆炸数值模拟程序,应用计算程序对自由场空中爆炸进行模拟,将计算得到的空中爆炸载荷与经验公式进行比较。结果证明该方法具有较高的精度。给出了强、弱间断性的空中爆炸流场密度和压力分布规律,同时对冲击波与冲击波相互作用进行模拟,说明RKDG方法能较好地模拟冲击波的反射、绕射等现象,处理空中爆炸间断性问题。     

流固耦合数值模拟方法及其在分段式SRM的应用

固体火箭发动机工作过程由于结构变形与内流场之间的流固耦合作用可能造成发动机内流场压强振荡,导致载荷的动态受力甚至可能毁坏载荷。从耦合算法、界面数据传递、动网格算法三个方面介绍了流固耦合数值计算方法,总结了流固耦合在分段式固体火箭发动机工作过程压强振荡方面的研究及应用进展。指出基于分离解法,结合流场大涡模拟模型,能较好的求解固体发动机内因流固耦合因素导致的压强振荡问题。     

混凝土动态断裂数值模拟研究

动态拉伸载荷下,混凝土断裂强度随应变率的增加而提高。根据混凝土内部骨料与砂浆的力学性能,建立描述混凝土材料的细观有限元模型。通过ABAQUS二次开发单元UEL计算动载荷下垂直骨料砂浆界面裂纹的扩展,计算不同加载率下裂纹的扩展路径。计算结果表明,在低加载率下,裂纹沿着骨料与砂浆界面传播,在高加载率下,裂纹将穿过骨料,分析表明混凝土应变率效应的物理成因应为骨料断裂所致。     

强冲击下线弹性体中的运动非线性效应

分析和研究了强冲击下线弹性体中与质点非线性运动有关的运动非线性效应。研究结果表明，运动非线性的动态响应十分显著，在分析和计算中不可忽视。本文还研究了线弹性体中运动非线性波的激波构成和传播。     

基于动网格CFD技术的膛口弹前激波流场数值模拟

针对数值模拟弹丸膛内加速运动造成的网格变化,采用分块网格划分的整体运动处理方法和基于动态层变方法的结构动网格技术,保证了数值网格的质量。模拟弹丸膛内运动的弹前激波流场,并描述了激波流场的形成,发展过程,实现了含运动弹丸的膛口激波流场模拟。数值计算结果与实验照片进行对比,弹前激波流场的形状和位置能较好吻合,表明数值模拟方法是合理可行的。     

Nitrosation and Nitration of Tetraacetyldibenzylhexaazaisowurtzitane

Tetraacetyldibenzylhitane (TADBIW) was subjected to debenzylation by nitrosating with inorganic materials available commercially to synthesize tetraacetyldinitrosohexaazaisowurtzitane (TADNSIW). TADNSIW was purified, and its structure was determined by FTIR, 1H NMR, MS and element analysis. The debenzylation reaction of TADBIW gave quantitative benzaldehyde as a by-product. This indicates that the reaction produces an imine cation as an intermediate. Hexanitrohexaazaisowurtzitane (HNIW) was prepared from unpurified TADNSIW with the yield over 96.0 % and the purity more than 98.0 %. And the mechanism of the reaction from TADNSIW to HNIW is proposed to be oxidation of nitroso and nitration of acetyl on the molecule of TADNSIW, This reaction system involved is simple, and the reaction can complete within a short time and under mild conditions. The product can be easily to separate and the waste disposed readily.     

A Robust Algorithm for Watermarking 2D Vector Maps with Low Shape-Distortions

The technique of watermarking has been introduced into 2D vector maps for many potential applications such as protecting the copyright of important GIS （geographical information system） data and tracing the data source of military maps. In most previous works, although the validity of the map data could be preserved during the embedding procedure, the shape-distortions of the map elements are usually neglected which would tend to degrade the invisibility of the watermarking schemes. A shape-preserving algorithm for watermarking 2D vector maps is presented in this paper. A 1D distance sequence extracted from the original map is adopted as the cover data instead of 2D coordinates. A watermark bit is represented by changing the distributions of the cover data. The embedding procedure induces lower shape-distortions than in former works. Experimental results indicate better invisibility of the proposed scheme, as well as its robustness to certain attacks such as map simplification, interpolation, additive noise and most geometric transforms.     

Open Rule-setting System Applied to Conceptual Design of Engines

Open rule-setting method advanced in this paper concentrates on providing designers of engines with a convenient way to express their design innovations and develop the expected prototypes in the early CAD stage, and constitute effective models for the following analysis process of CAE and CAPP. The problems arisen in the process of conceptual design with the traditional experience-based development method are analyzed. Based on those analyses, open rule-setting method is presented and some associated technical problems are discussed. The functional framework of open rule-setting system was built as software engineering methods. The speciality of the engine product as a kind of complex product and the requirement of the engine product based on its structural particularity to rule-setting system are considered carefully. A demonstration is supplied to illustrate how the open rule-setting method enhances the efficiency and quality of the engine conceptual design.     

Research on Linux Network Device Driver

By analyzing the working principle of Linux network device driver, discussing the Linux network driver structure and its key technologies, the general network driver structure and its design methodologies in Linux system are summarized. Through modifying the network device driver of Linux device driver 3rd version snull, c and improving the COW technology, the Zero-Copy technology in Linux （kernel version 2.6.11 ） is implemented. In the end, the success test tells us that the thorough analysis of network device driver is the foundation of many applications, and it also provides a certain improvement to a lot of real applications, even to military application development.     

Method for Measuring Velocity of Warhead Fragments Based on Photoelectric Detection

For measuring velocity and impacting position of single fragment of warhead, a non-contact measuring method is proposed, in which a six-light-screen array, a position indicator, a multi-channel chronograph and a computer are used.The principle of measurement is described. The key device of the system is a light screen array sensor which consists of six light screens allocated with certain geometrical parameters. When the fragment flies through the light screen array, the time of passing through each of the screens is recorded by the multi-channel chronograph. According to the time data and the geometrical parameters of the array, the velocity vector and the location of the fragment can be calculated immediately. The presented method can be used to locate the fragment and to measure the real velocity on its flying direction. It can also be used to measure the velocity of a fragment swarm after the system is engineered further.     

数码电子雷管中影响点火头性能因素分析

阐述了数码电子雷管中,点火药剂细结晶三硝基间苯二酚铅（LTNR）的制备工艺;从点火药剂的种类、加入黏合剂的质量分数、桥丝直径、点火头的电阻值、防潮漆的蘸涂等方面对点火头性能的影响因素进行了探讨;通过震动试验、并联起爆试验、延期精度检测与考核,试验结果表明：一次性合成的细结晶LTNR是制造数码电子雷管点火头较为理想的点火药剂,按技术要求生产的点火头性能指标能够满足行业标准要求。     

Improvement and Experiment of the Reamer in Vibra Cutter Against Wave Edge of Titanium Sheet Alloy Parts

By analyzing the influencing factors of part quality making of sheet alloy of titanium by vibra cutter, the shape of upper reamer is set as cylinder and wedge-shaped form, and the lower reamer as plain and hemicycle form, and its main structural parameters are defined as well. Then it is validated further that such improved vibra cutter reamer can be used to process curve-edged parts of titanium alloy sheet. The experimental result shows that the titanium alloy sheet parts processed by above equipment have no sharpen angles for convex parts and evident crevasse of concave-edged part. In summary, such improvement can eliminate the free-waved edge and improve the manufacture quality of titanium alloy sheet parts greatly.     

Experimental Study on the Small Flyer Initiating Behavior of Fine-grained Explosives

The initiating behavior of fine-grained explosives by small flyer is studied. The diameter of small flyer in this device is 1 ram. The test results indicate that the granularity of explosives has great effect on its flyer initiating sensitivity.The flyer initiating sensitivity of the fine-grained explosives is higher and the critical initiating energy is lower than that of common explosives. For common explosive, the flyer initiating sensitivity increases as the density is reduced. But for the fine-grained explosive, the test results are exactly opposite.     

Algorithm for Multi-laser-target Tracking Based on Clustering Fusion

Multi-laser-target tracking is an important subject in the field of signal processing of laser warners. A clustering method is applied to the measurement of laser warner, and the space-time fusion for measurements in the same cluster is accomplished. Real-time tracking of multi-laser-target and real-time picking of multi-laser-signal are introduced using data fusion of the measurements. A prototype device of the algorithm is built up. The results of experiments show that the algorithm is very effective.     

Influence of Installing Error on the Surface Shape Precision of the Axial Symmetry Aspheric Workpiece in Lapping

A method to calculate the surface shape error, which is caused by the installing error between the workpiece and the lapping tool in the process of form lapping, is proposed. The mathematical model which the installing translation error influences on the workpiece surface shape error is established. The changing rule of the error is simulated through the calculating example of the paraboloid workpiece. The results indicate that the surface shape error of the workpiece is increasing with the increase of the installing translation error, it is also increasing gradually along the center point of the curve surface to the edge, and the influence is severer to the curve surface with great curvature than that of the small curvature when the translation error is the same.