介子跃迁形状因子的重夸克极限和1/m_Q修正

在BS理论框架下,对0~-→0~-和0~-→1~-(0~-和1~-分别代表赝标介子和矢量介子)跃迁的形状因子进行模型无关的分析.结果表明BS框架既能给出重夸克极限下的自旋—味对称性,又能给出重夸克有效理论关于1/m_Q修正的Luke定理及其它关系.     

Effects of total pressures and equivalence ratios on kerosene/air rotating detonation engines using a paralleling CE/SE method

In this paper, the kerosene/air rotating detonation engines(RDE) are numerically investigated, and the emphasis is laid on the effects of total pressures and equivalence ratios on the operation characteristics of RDE including the initiation, instabilities, and propulsive performance. A hybrid MPI + OpenMP parallel computing model is applied and it is proved to be able to obtain a more effective parallel performance on high performance computing(HPC) systems. A series of cases with the total pressure of 1 MPa, 1.5 MPa, 2 MPa, and the equivalence ratio of 0.9, 1, 1.4 are simulated. On one hand, the total pressure shows a significant impact on the instabilities of rotating detonation waves. The instability phenomenon is observed in cases with low total pressure (1 MPa) and weakened with the increase of the total pressure. The total pressure has a small impact on the detonation wave velocity and the specific impulse. On the other hand, the equivalence ratio shows a negligible influence on the instabilities, while it affects the ignition process and accounts for the detonation velocity deficit. It is more difficult to initiate rotating detonation waves directly in the lean fuel operation condition. Little difference was observed in the thrust with different equivalence ratios of 0.9, 1, and 1.4. The highest specific impulse was obtained in the lean fuel cases, which is around 2700 s. The findings could provide insights into the understanding of the operation characteristics of kerosene/air RDE.     

Thermodynamics and performance of Al/CuO nanothermite with different storage time

The storage stability of energetic materials is important for its application. Here, the storage stability of Al/CuO nanothermite, which was prepared by electrospray method and stored with different storage time, was systematically researched. The activation energy of Al/CuO nanothermite was calculated by differential scanning calorimetry (DSC). The ignition temperature and the curve pressure history of Al/CuO nanothermite was measured using ignition temperature measuring device and constant-volume pressurization tests, respectively. Further, the thermites were characterized by X-ray Diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and Transmission electron microscopy (TEM). The results show that the morphology of the thermites did not change significantly. The activation energy was decreased from 254.1 kJ/mol to 181.8 kJ/mol after storage for 13 months. When stored for 0, 7 and 13 months, the peak pressures of Al/CuO nanothermite were 685.8 kPa, 626.3 kPa and 625.5 kPa, respectively. In addition to the ignition temperature, it was 775 ℃, 739 ℃ and 754 ℃, respectively. This result indicated that the ignition and combustion properties of Al/CuO nano-thermite are obviously reduced when stored for a long time, at room temperature.     

一类参数激励与强迫激励并存的非线性振动系统的分叉

本文用Ｌｉａｐｕｎｏｖ—Ｓｃｈｍｉｄｔ方法研究了同时受参数激励与强迫激励作用的非线性振动系统的亚谐分叉问题,用奇异性理论确定了等价意义下的分叉方程的形式,导出了必需的分叉系数,求出并且分析了１／２—１／２亚谐共振分叉方程的普适开折,画出了各个结构稳定域及分叉集上的响应图。     

有人/无人平台协同技术与行动模式研究

无人平台已广泛用于军用和民用市场,并在反恐、维稳、排爆,侦察等领域发挥了极其重要的作用。目前已形成了有人/无人平台共同协作完成任务的工作模式,大大地提高了工作的时效性、适应性、作战效能等。为了提高有人/无人平台的协同作战能力,本文研究有人/无人平台的协同作战技术体系以及作战模式,以解决在协同侦察、搜救、监视等应急任务中遇到的各种问题。此外,提出了一套完整的协同作战想定,可用于有效验证相关的协同技术。     

码分多址(CDMA)蜂房移动通信上、下行链路带宽非对称划分的分析

从移动台和基站接收机输入端载干比以及T S Rappaport和L B Milstein提出的信道传输模型出发 ,对码分多址 (CDMA)蜂房移动通信系统的上、下行链路带宽划分进行了分析 ,提出了非对称划分办法 ,同时给出了仿真结果。分析表明 :上、下行链路带宽划分有效地提高了码分多址 (CDMA)蜂房移动通信系统容量     

获得前馈序列最大周期的一般方法

本文讨论了前馈序列的周期性问题,找到了使前馈序列获得最大周期的一般方法。     

YFRIO 实时I/O语言与YFSIM 仿真语言的同步关系

本文介绍ＹＦＲＩＯ语言和ＹＦＳＩＭ语言的同步关系,阐述了两者同步的硬件、软件机制,以及如何进行程序设计。     

多全球导航卫星系统联合的探月飞行器轨道定位分析

针对探月飞行器月球公转轨道上的卫星导航定位问题,以高轨道飞行器卫星导航定位的研究为基础,采用多全球导航卫星系统联合定位的方法进行仿真。分析了载波功率与噪声功率密度比为15d BHz的弱信号捕获门限下,各系统联合定位时波束主瓣和旁瓣的可用性,同时对各系统联合情况下的精度因子值进行分析。仿真结果表明:当接收到的卫星天线辐射的主瓣和旁瓣信号均高于载噪比门限时,全球导航卫星系统的三系统或四系统的联合能满足实时定位条件;而旁瓣损耗不加以补偿时,接收信号载噪比低于门限并导致任意联合方式均无法完成定位。各系统联合的精度因子分析表明:单系统或双系统联合的几何精度因子变化剧烈,四系统联合相比三系统联合的几何精度因子下降16.93%;三系统联合定位方案中,美国全球定位系统、中国的北斗卫星导航定位系统与欧洲的伽利略卫星导航定位系统联合方案的几何精度因子值变化最平稳,为最佳选择。理论分析和仿真结果为探月飞行器定位技术研究和星载多系统接收机设计提供参考。     

一种从二维照片反求三维CAD模型的稳健方法

研究了从物体二维照片重构其三维CAD模型的算法。通过物体在不同方位的一组照片 ,选取一定数量的配准点 ,该算法能够计算出照相机的运动参数 ,进而得到物体表面的 3D几何信息及CAD模型。算法充分考虑到了CAD建模的可制造性约束 ,具有精确、稳健的特点 ,在逆向工程建模、计算机视觉、机器人领域有应用前景。