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关于随机变量分布函数 总被引：1，自引：0，他引：1
张晓明 《福建工程学院学报》2007,5(4):369-371
主要讨论连续型随机变量分布函数与离散型随机变量分布函数在表达形式等方面的异同,总结连续型随机变量分布函数的主要表达形式,并讨论连续型随机变量分布函数的可导性. 相似文献
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讨论二维连续型随机变量的和、差、积、商分布函数时,可先求出它们的密度函数,然后利用分布函数是密度函数的积分这一关系,即可求出其分布函数。 相似文献
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研究了自由分布（连续性）条件下顺序统计量函数的分布问题,首先证明单个顺序统计量函数的分布服从贝塔分布和多个顺序统计量函数的联合分布与U（0,1）上对应顺序统计量的联合分布相同;其次证明两个顺序统计量函数之差也服从贝塔分布及其协方差阵的表达形式;最后给出了顺序统计量函数的条件分布的一些相关结果和推论。 相似文献
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为了求解参数估计中的统计推断问题,将不含参数的非参数核密度估计和经验分布函数作为"理论分布",含参数的密度函数和分布函数作为"拟合分布",逆向地将实际中的两类分布角色互换,然后构建拟合分布与理论分布偏差的目标函数。再基于优化理论得到使得目标函数达到最小的参数值作为未知参数的估计,由此构建了求解经典的参数推断问题的两种逆向求解法。通过柯西分布参数的随机模拟试验,说明了逆向法的可行性和普适性;再结合Bootstrap方法,对常见分布参数的区间估计和检验p值进行随机模拟。结果表明,逆向方法在上述参数统计推断问题上的可行性;基于分布函数的逆向法优于基于密度函数的逆向法。 相似文献
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随机变量的分布函数完全描述了随机变量取值的概率规律,因此研究分布函数的性质具有十分重要的意义,讨论一维连续实随机变量序列的分布函数的一些性质。 相似文献
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随机变量的分布函数是一种分析性质良好的函数，通过分布函数就能计算出各种事件的概率，因此，引进随机变量的分布函数，能使许多概率问题得以简化而归结于函数的运算，但就一般的教学中，仅对分布函数作为较直观的描述，缺乏数学上的严密性，本文就在概率论公理 系统的基础上对随机变量，分布函数进行严格定义并由此探讨随机变量分布函数的教学问题。 相似文献
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本文指出了连续型的分布函数Ｆ（ｘ）与其密度函数ｆ（ｘ）之间的关系，给出了奇异型的分布函数的例子，说明了离子散型的分布函数不一定是阶梯函数。 相似文献
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采用线性稳定性理论研究了三维平板边界层中展向来流速度对流动稳定性的影响。在基本流中给出了展向速度的大小,从特征值、特征函数和扰动波的增长幅值上显示不同展向来流速度的计算结果,并和无展向来流速度的二维边界层进行比较,结果表明,展向速度对边界层内的扰动起着不稳定的作用,且展向速度越大稳定性越差。 相似文献
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SIMOVSKI C.R VIITANEN A.J. TRETYAKOV S.A 《浙江大学学报(A卷英文版)》2006,7(1):29-33
INTRODUCTION The waveguide properties of linear arrays (chains) of silver nano-particles at optical frequencies are well known (Krenn et al., 1997; 1999; Tretyakov and Viitanen, 2000; Girard et al., 1994; Weber and Ford, 2004). Silver spheres and ellipsoids can support forward or backward waves along the chain depend- ing on their polarization state and the eigenfrequency (Krenn et al., 1999; Tretyakov and Viitanen, 2000; Girard et al., 1994; Weber and Ford, 2004). At com- paratively … 相似文献
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ＩＮＴＲＯＤＵＣＴＩＯＮＳｈｏｃｋｗａｖｅｒｅｆｌｅｃｔｉｏｎｆｒｏｍａｗａｌｌｓｕｒｆａｃｅ,ｄｉｆｆｒａｃｔｉｏｎａｌｏｎｇａｃｕｒｖｅｄｓｕｒｆａｃｅ ,ｐｒｏｐａｇａｔｉｏｎｔｈｒｏｕｇｈａｃｈａｎｎｅｌｏｒａｔｕｂｅｗｉｔｈｖａｒｙｉｎｇｃｒｏｓｓ 相似文献
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The scaling and similarity of wall bounded turbulent flow were studied. The properties of such flows and the relationship between a power law and a logarithmic type of velocity distribution were investigated. Based on the physical mechanism involved, our results show that the power law and the logarithmic distribution are only different forms with the same hypothesis and hold only in the outer flow zone. Thus, a universal explanation for various empirical formulae of velocity distribution was obtained. Manning＇s formula was studied to explain theoretically the experiential result that the roughness coefficient is only a comprehensive parameter of the whole system without a corresponding physical factor. The physical mechanism of the velocity distribution of parallel to wall bounded flow was explored, the results show that the parameters in the formula of velocity distribution are indices of the system responding to flowing environmental factors to represent general case of boundary roughness and the flowing state, corresponding physical mechanism is vortex motion. 相似文献
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The use of bionic non-smooth surfaces is a popular approach for saving energy because of their drag reduction property. Conventional non-smooth structures include riblets and dimples. Inspired by sand dunes, a novel variable ovoid nonsmooth structure is proposed in this study. The body of the variable ovoid dimple was designed based on three size parameters, the radius, semimajor, and depth, and a 3D model was created based on UG software. The constructed variable dimples were placed in a rectangular array on the bottom of a square tube model. Following ANSYS meshing, the grid model was imported into FLUENT, where the flow characteristics were calculated. Results of skin friction reduction were achieved and the effect of the design parameters on different variable ovoid dimples was obtained by orthogonal testing. Various aspects of the skin friction reduction mechanism were discussed including the distribution of velocity vectors, variation in boundary layer thickness, and pressure distribution. 相似文献
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胡永生 《福建教育学院学报》2010,11(5):99-102
文章研究一类具有无穷大边值的二阶半线性微分方程的奇摄动Robin问题的双边界层与内层现象。基于边界层校正,构造了该问题的边界层、内层校正函数;基于微分不等式理论,证明了该边值问题解的存在性,同时得到解的一致有效的高阶渐近估计。 相似文献
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基于有限体积方法,对嵌入式行星螺杆挤出机内流场进行了三维等温数值模拟。通过简化的物理模型来模拟螺杆的几何结构,使用用户自定义程序设定了行星螺杆运动的边界条件。分析了挤出机螺槽内压力和速度的分布;使用粒子追踪技术观察了螺杆内流体运动轨迹和粒子分布规律;对粒子在螺杆内的停留时间分布进行了统计。结果表明行星螺杆对流体运动产生了周期性扰动。初始位置在一起的两个粒子,终点位置却相距很远。示踪粒子的具有对初始敏感的混沌特性,粒子的运动轨迹具有无序性,说明流体存在着混沌效应。 相似文献
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This paper reports theoretical and experimental study of a new type of interaction of a moving shock wave with an unsteady
boundary layer. This type of shock wave-boundary layer interaction describes a moving shock wave interaction with an unsteady
boundary layer induced by another shock wave and a rarefaction wave. So it is different from the interaction of a stationary
shock wave with steady boundary layer, also different from the interaction of a reflected moving shock wave at the end of
a shock tube with unsteady boundary layer induced by an incident shock. Geometrical shock dynamics is used for the theoretical
analysis of the shock wave-unsteady boundary layer interaction, and a double-driver shock tube with a rarefaction wave bursting
diaphragm is used for the experimental investigation in this work.
Projects (No. X61151) supported by Centre for Engineering Research at Zhejiang University of Technology, China 相似文献
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The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According
to the characteristics of VLEM, only some characterized layer thickness values need be defined as design variables instead
of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this
method is that it is not necessary to regenerate the FE (finite element) grid during the optimization process so as to avoid
optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization
problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained
after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named “behavior model
technique” can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness
and practicality of the proposed method.
Project (No. 50075083) supported by National Natural Science Foundation of China 相似文献
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《天津大学学报(英文版)》2017,(6)
In this study, a continuous and airtight twinspiral dryer was developed in accordance with the characteristics and challenges in the process of disposing polysilicon slurry. Computational fluid dynamics(CFD)simulations were used to investigate the flow field in the rotating twin-spiral continuous dryer and an original discrete phase model was also elaborated to compare with the cold-modeling experimental results. The corresponding flow field was obtained using the available inlet velocity of 0.05-0.3 m/s and the rotational speed of the inner cone of 12-44 r/min, the residence time distribution, and tracked particles trajectory. Results showed that the residence time of the tracer particles in the cone cylinder was about 15.8-25.4% of the time spent out of it, and the particle's residence time was much shorter in contrast to the rotational speed and inlet velocity. The external ribbon had a larger influence on the fluid, thereby leading to a larger velocity in the region outside the cone compared to that in the region inside the cone. In addition, the appearance of the vortex and boundary layer separation at the back of the ribbon and the spoke bar had secondary diversion effects on the fluid. Furthermore, the inlet velocity had little influence on the flow field while the rotational speed of the cone greatly affected the flow field. Hence, the CFD simulations showed good agreement with the experimental results. 相似文献