基于数字图像处理的破片速度参数测量

介绍了两种常用的测量破片速度参数的方法,研究了数字图像处理技术在终点效应研究中的实现方法,合理设计试验并利用数字图像处理技术测量了破片的速度参数,具有一定的可行性,实用性强,研究结果表明,利用此方法所得到的破片速度参数与理论计算以及其它方法所测得的结果基本吻合。     

弹丸破片测速的新概念与新方法可行性研究

由于弹丸的杀伤能力与其破片动能有直接的关系,因此,采用弹丸破片在定距离处平均击靶速度(破片存速)比采用破片平均飞散速度衡量破片杀伤能力更为准确,也更具有实际意义。在此概念基础上,本文设计了一种新的破片测速方法。利用破片穿入预置阻尼块发生侵彻现象时其侵彻深度与撞击速度的函数关系,采用现代传感器技术及数据采集处理技术,测量出破片侵彻深度,从而准确测定破片击靶速度与分布,为弹丸破片杀伤能力的评估提供了一种新的思路与方法。     

考虑瞬态压力波效应的高速列车车门模态试验分析

讨论高速列车会车瞬态压力波与车门模态的关系。介绍模态试验的基本理论。采用锤击脉冲激励获得单个车门的基本模态。采用正弦扫频激励获得车门 - 框架系统的衍生模态。将车门基本模态和衍生模态相结合,可了解车门弯曲和扭曲的频率与振型。通过采取措施改善车门模态参数,将减缓高速列车会车瞬态压力波的效应。     

基于2.5维有限元法的有限长波导结构模态密度计算EI北大核心CSCD

模态密度是衡量振动系统贮存能量大小的物理量,同时也是统计能量分析子系统的主要参数之一,其精度能够直接影响系统响应预测的精度;群速度为结构波能量的传播速度,是表征结构波动特性的重要参数。针对工程中常见的波导结构,基于2.5维有限元法计算结构的频散曲线,利用波形置信度概念对频散曲线对应的特征波进行分类,同时给出波导结构特征波群速度的表达式。从波动角度出发,推导了有限长波导结构总的模态密度和不同特征波模态密度的计算公式。以单板和高速列车用铝型材为例,对其波动特性和模态密度进行分析和计算。研究结果表明,随着频率增加,该方法计算得到的模态密度和其他方法吻合较好。在结构的截止频率处,群速度为零,模态密度无穷大,但在有限频带内的平均模态密度为有限值;结构的某些截止频率附近,群速度和模态密度可能会存在负值,意味着结构波的传播方向和能量的传播方向相反。通过对特征波的识别,可实现不同特征波下的模态密度计算。相关结果可为统计能量分析中相似模态群子系统的划分提供参考依据。     

图像序列中破片群目标提取与关联方法研究

图像序列中破片群目标的提取和相互关联是基于高速摄影的破片参数测试中的关键技术,为准确提取破片群目标并进行关联,采用混合高斯背景建模结合邻帧差分法提取出前景;通过形态学处理,消除爆炸产生的火花扬尘等干扰,准确提取出了图像中的破片目标;提出了基于轨迹约束的搜索方法对图像序列中同一破片目标进行关联,通过试验验证,证明方法可以满足测试要求。解决了高速摄影法进行破片测速中破片群目标提取和图像序列中同一目标关联的关键问题。     

模拟破片杀伤战斗部空爆冲击波与高速破片群联合作用的等效试验方法

破片杀伤战斗部空爆冲击波与高速破片群联合毁伤作用下目标结构的毁伤特性、防护效能等是当前防护领域的热点和难点,但目前的试验研究手段和方法存在不足,为此,提出采用等效缩比战斗部(其原理为炸药爆炸驱动预制破片分散)来模拟破片杀伤战斗部,可作为进行空爆冲击波与高速破片群对防护结构的联合毁伤作用的实验方法。在确定防御目标战斗部、防御目标弹丸和几何缩尺比的基础上,根据爆炸力学相关经验公式,提出了求解等效缩比战斗部的装药和预制破片的相关参数的等效计算方法。该等效试验方法考虑了多破片侵彻的增强效应以及与爆炸冲击波的联合毁伤增强效应,且等效计算方法参数较少、简单实用。     

破片撞击燃料箱时水锤效应的数值仿真研究

为了揭示高速破片对燃料箱的毁伤机理,采用数值计算的方法研究了单破片、多破片撞击燃料箱所形成的液压水锤效应,计算分析了单枚破片的撞击速度和多枚破片之间的距离对箱体变形的影响。结果表明,单枚破片高速撞击燃料箱时,撞击速度每增大100 m/s,变形高度增加4.3%;当多枚破片以1400 m/s的速度撞击燃料箱时,破片之间的距离越小,箱体的变形量越大;当燃料箱体的变形最大时,破片间距为8.3倍破片直径。     

光幕靶测量破片群初速的方法

针对计算战斗部杀伤概率和引战配合参数,提出一种六幕光幕靶对战斗部破片群初速进行测量的方法.给出了六幕光幕靶的测量原理.可以通过测量多个破片的飞行速度与飞行姿态角,推导出速度衰减系数.采用多台六幕光幕靶圆形放置,同时参与测试,再根据破片速度衰减公式确定破片群的初速.同时对沿战斗部轴向的破片初速进行了探讨,用其初速分布更准确地表示战斗部的初速分布,讨论了误差影响因素.     

高速高温计在脉冲加热技术中的应用

高速高温计作为利用脉冲加热技术测量热物性参数的瞬态量热法的重要工具,随着脉冲加热技术的发展而发展起来.介绍了最近三十年国内外高速高温计的发展历史,给出高速高温计的一些基本的光电特性和标定方法,着重介绍高速高温计在利用脉冲加热技术测量材料热物性参数中的应用.最后介绍了该领域的最新研究动态和发展方向.     

装配式组合防爆墙抗高速破片侵彻性能研究

为研究一种新型的装配式双层钢板组合防爆墙结构的破坏分级指标,依据CONWEP程序计算所得的不同恐怖爆炸威胁等级下破片的特征参数,采用LS-DYNA软件,对组合防爆墙及等厚混凝土结构抗单破片及多破片高速法向撞击时的侵彻性能进行对比研究,分析了破片在防爆墙中的侵彻过程,得到了4种类型破片法向撞击下两种防爆墙的破坏特征以及破片侵彻深度、速度、加速度等特性参数的变化规律.分析表明,组合防爆墙抗破片侵彻性能明显优于混凝土结构,在研究结构破坏分级指标时须考虑多破片的破坏效应.     

A Salmonella detection system using an engineered DNA binding protein that specifically captured a DNA sequence

We have developed a novel method for the detection with high selectivity of a double-stranded DNA fragment using an engineered DNA-binding protein, DnaA IV, a fusion protein of the DNA-binding domain of DnaA and glutathione S-transferase. The DNA fragment detection system is based on DNA-protein interaction and consists of sequence-specific binding of DnaA IV with a DNA fragment containing the DnaA box. DnaA IV, while not capturing other DNA fragments, specifically captured that containing the DnaA box. Because the oriC fragment containing the DnaA box could be specifically amplified by PCR from the genus Salmonella, the DNA fragment detection system was adapted for the detection of Salmonella. The Salmonella detection system using PCR amplification and the engineered DNA-binding protein could distinguish 104 cfu/mL Salmonella from 106 cfu/ mL contaminating bacteria.     

Computational modeling of explosive-filled cylinders

A time-dependent, two-dimensional, finite-difference code can be used to model fragmenting cylinders. Strictly hydrodynamic treatment of the casing material generally overpredicts the final fragment velocity. A more definitive final fragment velocity is predicted when the casing material is treated as an elastic-plastic material, but the final fragment velocities occur at unrealistically high cylindrical expansion ratios. To remove some of these objections and, at the same time, model the casing motion more realistically, a gas leakage model has been developed to simulate explosive gas leakage around fragments after casing breakup. Comparisons have been made between code calculations and experimental data. The experimental data include different length-to-diameter ratios, natural and discrete fragmenting cylinders, different charge-to-casing mass ratios, and different initiation postures. The gas leakage model predicts definitive final fragment velocities in excellent agreement with the experimental data.     

自然激励技术在时延相关白噪声激励系统中的应用

工况模态分析(operational modal analysis,OMA)是一种只基于输出数据进行系统模态参数辨识的技术。由于系统所受激励未知,通常假设其为互不相关的白噪声。自然激励技术(natural excitation technique,NExT)正是一种基于该假设的从响应数据中提取自由衰减信号的高效方法。然而对于真实工况,系统所受激励之间互不相关的假设过于严格,例如行驶的车辆等所受激励为时间延迟相关的白噪声。针对这类情况,基于复模态系统讨论NExT理论的适用性。结果表明,NExT是否适用取决于从相关函数中截取的用来进行OMA分析的数据段的位置,当数据段位于Tε区间内,NExT是适用的。在ε已知的情况下,可以基于NExT对系统进行工况模态分析。最后通过仿真进一步验证该结论。     

基于SIMULINK的弹丸自然破片运动模型仿真研究

为了研究实际空气中自然破片的运动规律,建立了直角坐标系下破片质心运动模型,并建立SIMULINK仿真模型对破片的运动微分方程组进行仿真求解,得到了破片的运动轨迹、飞行的水平距离、落地时的动能,以及破片随其初始飞行角度变化的规律.研究结果表明,基于SIMULINK对弹丸破片运动规律进行研究,可以获得直观、形象、准确的仿真...     

Fragment detection system for studies of exotic neutron-rich nuclei

We have developed a fragment detection system for use in studies of exotic, neutron-rich nuclei. Using a C-shaped dipole magnet, the system sweeps charged fragments and un-reacted beam particles through an angle before stopping them in an array of plastic scintillator detectors, recording time-of-flight and total energy. The system also includes a pair of silicon strip detectors to measure fragment angle of emergence from the target and energy loss for particle identification.     

Assessment of missile hazards: identification of reference fragmentation patterns

Industrial accidents involving fragment projection were investigated. The analysis of fracture mechanics fundamentals allowed the exploration of the relations between the fracture characteristics and the final event leading to equipment collapse. Reference fragmentation patterns were defined on the basis of the geometrical characteristics of the categories of process vessels that are more frequently involved in fragmentation accidents. Primary scenarios leading to fragment projection were correlated to specific fragmentation patterns. A database reporting a detailed analysis of more than 140 vessel fragmentation events provided the data needed to support and validate the approach. The available data also allowed the calculation of the expected probability of fragment projection following vessel fragmentation, and the probability of the alternative fragmentation patterns with respect to the different accidental scenarios, based on the observed frequencies over the available data set.     

A simplified model for the assessment of the impact probability of fragments

A model was developed for the assessment of fragment impact probability on a target vessel, following the collapse and fragmentation of a primary vessel due to internal pressure. The model provides the probability of impact of a fragment with defined shape, mass and initial velocity on a target of a known shape and at a given position with respect to the source point. The model is based on the ballistic analysis of the fragment trajectory and on the determination of impact probabilities by the analysis of initial direction of fragment flight. The model was validated using available literature data.     

Spin velocimeters for impact debris fragments

An experimental technique for determining the velocity of individual debris fragments from hypervelocity impacts and correlating these velocity data to fragment size is presented. Design trades and experimental results for fragment spin velocimeters based on this technique are also presented. Validation tests were conducted to verify and optimize the performance of these instruments, and they were subsequently used to collect data for four hypervelocity impact tests. Such data are critical to the development of accurate debris environment models and to support safety hazard analyses of flight tests involving impacts. Comparisons with model predictions are presented.     

王快水库堆石爆破块度分布预报系统研究

王快水库堆石填筑工程堆石采用溢洪道开挖石料,溢洪道爆破开挖工程应用Kuz-Ram模型,并利用生产性爆破试验修正Kuz-Ram模型,建立了堆石爆破块度分布预报系统。此系统能经济、合理地制定爆破方案,确定爆破参数,控制堆石的块度,及时预报爆破块度分布情况,在王快水库工程25次大型爆破中取得了很好的应用效果。     

Chemicalome and metabolome matching approach to elucidating biological metabolic networks of complex mixtures

Global metabolite identification of complex compound mixtures in biological systems is a very challenging task. Herein, we developed and validated a chemicalome to metabolome matching approach by taking herbal medicine as an example to delineate the metabolic networks of complex systems. This approach consists of five steps of data processing including raw data output, endogenous background subtraction, parent compound and metabolite differentiation, chemicalome to metabolome correlation, and the final validation via manual fragment comparison. Chemicalome to metabolome correlation, the core step of this approach, was performed based on matching the accurate mass differences of pseudomolecular ions between them with the accurate mass changes of known metabolic pathways and validating the matches by validation ions. A step-forward approach that confers a gradual identification of metabolites generated from different steps (1-4) and types (degradation, phase I/II, or mixed) of metabolic reactions was further proposed for chemicalome to metabolome matching. This approach was validated to be very useful and powerful for the metabolite identification of a single compound, a homologous compound mixture, and a complex herbal system. Using this approach, all metabolites (162) detected from urine samples of rats treated with Mai-Luo-Ning injection could be linked to their respective parent compounds, and 143 of them were supported by the final validation via manual fragment analysis. In most cases, more than 80% of the automatic matching results could be supported by the manual fragment validations. A complex metabolic network showing all the possible links between precursors and metabolites was successfully constructed. This study provides a generally applicable approach to global metabolite identification of complex compound mixtures in complex matrixes.