高精度有限体积格式在三维曲线坐标系下的应用

为了构造在光滑区具有较高分辨率并且可以无振荡捕捉激波的高精度有限体积格式,同时降低格式在模板选择上遇到的困难,基于逐维重构方法,发展了结构网格下的高精度有限体积格式,并将这一格式推广到三维曲线坐标系下,从而可以适应相对复杂外形下的计算。为充分验证格式的有效性,选取一系列典型算例进行计算:在等熵涡输运和二维喷管流动中验证了格式的精度可以达到设计精度;在双马赫反射问题中格式也表现出良好的捕捉激波的能力。数值计算表明,上述格式在曲线网格上具有较高的数值精度和鲁棒的激波捕捉能力,适用于流体力学方程的计算。     

硬件加速的三维雷达作用范围表现

未来数字化战场迫切需要表现复杂环境影响下的三维雷达作用范围,目前研究多限于二维,而三维表现又受限于速度,为此提出一种硬件加速的三维表现方法。在构造环境影响下雷达电磁波损失三维数据场的基础上,利用硬件加速的等值面提取算法建立雷达作用范围的三维模型,并将其表现到战场环境中。在普通微机上针对典型雷达的实验中,克服了二维表现不直观以及三维表现慢的缺点,形象地展示了地形大气等环境影响下三维作用范围,从而为用户提供决策和感官支持。     

棱纹面与洛仑兹力对湍流边界层特性影响的比较

用氢气泡技术对棱纹面平板以及施加行波式洛仑兹力的平板水边界层开展流动显示实验研究,探讨棱纹面与行波式洛仑兹力影响湍流边界层相干结构的作用机理.实验结果表明,棱纹面与洛仑兹力促进了边界层由层流向湍流的转捩;而对于湍流边界层,在一定的无量纲参数范围内棱纹面与行波式洛仑兹力都能实现边界层的局部减阻,相应地湍流边界层粘性底层低速条带平均间距有所增加.     

战场大地形空间格网点的高斯曲率算法研究及可视化

论述了在细节层次模型简化技术中,空间格网点的高斯曲率的计算方法,以及在.NET平台下如何用C#语言对算法进行编程.然后依照此算法得出格网点曲率值的大小,删除曲率小的中心点并对删除中心点后留下的空洞进行三角化,从而实现细节层次模型的简化.为体现算法的效果,应用高斯曲率算法将全细节的三维地形模型实现了细节层次模型的可视化,并提出用曲率的几何性质来对算法进行了误差分析,将其结果与其他算法进行了比较.通过实例和误差分析,其结果表明此算法速度快且效果好.     

超声导波在管道中传播的可视化模拟研究

利用有限元方法建立管道导波3-D模型,通过在管道中激励纵向超声波,模拟导波在管道中的传播形态。根据回波信号的传播时间计算了纵波传播速度,与频散曲线得到的纵波速度符合较好。从观测点取得的波信号能够反映超声波在管道中传播时存在的反射和衰减现象,动画结果能够形象直观地反映导波在管道中传播的情形,实现了导波传播的可视化模拟。该研究有利于更好地解释导波在管道无损检测中出现的频散特征。     

A new look on the electric spark sensitivity of nitramines

Electric spark energy, E_ES, for a 50% probability of initiation of the 14 nitramines was determined using a measuring instrument in which the electrodes are in direct contact with the sample. Indirectly proportional relationships were established between the logarithm of the E_ES values and the length of the longest N–N bond in the nitramine molecule. This finding is compatible with the mechanism of the first step in the electro-reduction of the nitramine grouping. Directly proportional relationships were found to exist between the E_ES values and the crystal lattice free volumes, ΔV (i.e. an increase in the ΔV values increases the nitramine's resistance to electric sparks) but there were several nitramines with the opposite course of this relationship. Also a semilogarithic relationships between the E_ES values and a ratio of intrinsic volumes of molecule, V_int, to the ΔV values were described as well as ambiguous linear dependence between these energies and a sum of the positive and negative extremes of the molecular surface electrostatic potentials, V_S,Σ. Several nitramines studied (always the same ones) display roughly the same distribution in the coordinate systems of relationships with lengths of the longest N–N bonds, the V_int/ΔV ratio and the sum V_S,Σ as the independent variables. It was found that, typically, such relationships start from a single identical point, in effect a point corresponding to data for a structural unit from which the studied nitramines can be hypothetically generated, and/or are converging on another point, often the one corresponding to the data for HNIW. All the findings point to a fundamental influence of the intermolecular forces on reactivity of nitramines exposed to electric sparks.     

Should competing firms reveal their capacity?

In this article, we explore when firms have an incentive to hide (or reveal) their capacity information. We consider two firms that aim to maximize profits over time and face limited capacity. One or both of the firms have private information on their own capacity levels, and they update their beliefs about their rival's capacity based on their observation of the other firm's output. We focus on credible revelation mechanisms—a firm may signal its capacity through overproduction, compared to its myopic production levels. We characterize conditions when high‐capacity firms may have the incentive and capability to signal their capacity levels by overproduction. We show that prior beliefs about capacity play a crucial, and surprisingly complex, role on whether the firm would prefer to reveal its capacity or not. A surprising result is that, despite the fact that it may be best for the high‐capacity firm to overproduce to reveal its capacity when capacity information is private, it may end up with more profits than if all capacity information were public knowledge in the first place. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

富氮气体对柴油氧化安定性影响

在95℃条件,考察了2种柴油在5种氮体积分数下氧化安定性随时间的变化,采用方差分析法分析了富氮气体对实际胶质、酸度的影响,拟合了实际胶质生成速率与氮体积分数的关系。结果表明:氮体积分数对实际胶质、酸度有显著性影响,实际胶质与储存时间呈一次函数关系,实际胶质生成速率与氮体积分数间存在幂函数关系,储存过程中氮体积分数越大,氧化生成有机酸越少。     

氧气体积分数对油气爆炸特性的影响

作为燃烧和爆炸三要素之一,氧气体积分数的控制对于爆炸事故的防治具有重要意义。实验研究了氧气体积分数对汽油蒸气-空气混合物（简称油气）爆炸极限和爆炸压力的影响。结果表明：随着氧气体积分数的降低,油气爆炸下限呈一阶指数规律缓慢增大,油气爆炸上限呈线性规律迅速减小;爆炸极限范围由0.92%~3.76%缩小为1点,该爆炸极限临界点为1.22%,对应的临界氧气体积分数为11.4%;油气的最大爆炸压力和最大压力上升速率随着氧气体积分数的降低而减小,油气体积分数越大,氧气体积分数影响越显著。     

舰炮防空战法的可视化技术

舰炮防空是水面舰艇自防御的重要手段之一.文章围绕可视化和虚拟现实技术,分析了舰炮防空战法研究的内容,给出了舰炮防空战法可视化的方法,重点探讨了其中的防空弹道仿真、反舰导弹弹道仿真、海浪水文气象环境仿真、战场焰火和爆炸效果仿真及舰炮防空战法仿真中实时碰撞检测的基本方法和优化技术,提出了解决这些问题的主要方法,并在PC机上进行了实现.最后给出了舰炮防空战法的可视化结果.