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401.
A Twin-CME Scenario for Ground Level Enhancement Events 总被引:2,自引:0,他引:2
Ground Level Enhancement (GLEs) events are extreme Solar Energetic Particle (SEP) events. Protons in these events often reach ~GeV/nucleon. Understanding the underlying particle acceleration mechanism in these events is a major goal for Space Weather studies. In Solar Cycle 23, a total of 16 GLEs have been identified. Most of them have preceding CMEs and in-situ energetic particle observations show some of them are enhanced in ICME or flare-like material. Motivated by this observation, we discuss here a scenario in which two CMEs erupt in sequence during a short period of time from the same Active Region (AR) with a pseudo-streamer-like pre-eruption magnetic field configuration. The first CME is narrower and slower and the second CME is wider and faster. We show that the magnetic field configuration in our proposed scenario can lead to magnetic reconnection between the open and closed field lines that drape and enclose the first CME and its driven shock. The combined effect of the presence of the first shock and the existence of the open close reconnection is that when the second CME erupts and drives a second shock, one finds both an excess of seed population and an enhanced turbulence level at the front of the second shock than the case of a single CME-driven shock. Therefore, a more efficient particle acceleration will occur. The implications of our proposed scenario are discussed. 相似文献
402.
为了在初/中级教练机装备方案决策中体现出训练需求,选用质量功能展开的方法对其进行了分析.先利用比较矩阵确定训练需求重要度,建立训练需求与能力属性之间的QFD关系矩阵,得到不同能力属性的重要度,最后计算出个方案的能力属性值,通过线性加权计算将属性值反映到不同方案对于训练需求的满足程度上来,得出了量化分析的结果,为教练机装备决策方法研究提供了一个新思路. 相似文献
403.
改进了用于实验室热尾流测量的温度测量系统,提高了系统的集成度和抗干扰能力。在水槽中实验研究了螺旋桨推进潜艇模型在有、无温度分层流体中尾流的热特征,得到两种条件下尾流的温度分布和信号衰减规律,分析了两种尾流信号的形成机理及其影响因素,表明在温度分层环境中"冷尾流"信号对探测和识别水下航行的潜艇更为有利,所得结果可为红外反潜和潜艇红外隐身提供更加切合实际的理论支撑。 相似文献
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406.
Forward Variable Area Bypass Injector (FVABI) is one of key components which contributes to modulate the cycle parameters of Variable Cycle Engine (VCE) under various operation conditions. The modeling method of zero-dimensional FVABI was reviewed and its deficiency was analyzed based on FVABI flow characteristic. In order to improve the accuracy of VCE performance simulation, the high-fidelity modeling method of FVABI was developed based on its working characteristics. Then it was coupled with the zero-dimensional VCE model and the multi-level VCE model was built. The results indicate that the geometric and aerodynamic parameters can affect the interaction between the two airflows and the zero-dimensional FVABI model is too simple to predict the component performance accurately, especially when the FVABI inner bypass is chocked. Based on the performance curves for single bypass mode and the regression model of multi-scale support vector regression for double bypass mode, the high-fidelity model can predict FVABI performance accurately and rapidly. The integration of high-fidelity FVABI model into zero-dimensional VCE model can be done by adjusting iterative variables and balance equations. The multi-level model has good convergence and it can predict VCE performance when the FVABI inner bypass is chocked. 相似文献
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408.
一种MEMS陀螺标度因数误差补偿方法 总被引:3,自引:0,他引:3
高动态、恶劣温度环境下,微小型飞行器(MAV)导航、制导与控制系统关键器件微机电系统(MEMS)陀螺受温度和转速耦合影响,其标度因数误差呈强非线性特点,常规方法无法精确补偿。通过分析MEMS陀螺标度因数误差的产生机理,建立了包含温度和转速非线性因素的标度因数误差模型,提出一种基于径向基(RBF)神经网络的标度因数非线性耦合误差补偿方法,解决了常规补偿方法精度差的问题。标定与补偿实验表明:在-10~+55℃温度范围、-150~+150(°)/s输入转速范围内,采用新方法补偿后MEMS陀螺输出平均精度比多项式拟合方法提高7倍;在-20~+20(°)/s低输入转速的误差强非线性区间内,精度提高近20倍,验证了本文方法的有效性和优越性。 相似文献
409.
The issue of mesh-dependence emerges when the conventional continuum damage model is applied to handling the softening behavior. In order to circumvent the mesh-dependence, the non-local theory is introduced into the conventional damage model and the finite element formulas are derived for two-dimensional gradient-enhanced damage model. A new element is proposed in which the basic unknown quantities are displacement, non-local equivalent strain and the gradient of non-local equivalent strain. The element and constitutive equation proposed in this article are added to the finite element software ABAQUS through user subroutine UEL. Numerical results show that the gradient-enhanced damage model can eliminate the mesh-dependence and is effective for dealing with the issue of softening behavior. 相似文献
410.
在综述了电缆故障类型和现有电缆故障检测与定位方法的基础上,引入了两种电缆故障在线检测与定位新方法——序列时域反射法(STDR)和扩散频谱时域反射法(SSTDR),分析研究了两种方法的原理,选取了一种适用于两种方法的相关算法——改进的实序列频域相关算法,并在MATLAB中建立了仿真模型,对两种方法进行了仿真验证,并进行了比较,对实际的应用具有理论指导意义。 相似文献