共查询到20条相似文献,搜索用时 93 毫秒
1.
“网民知多少?”——中国互联网络信息中心全国调查抽样方案设计 总被引:1,自引:1,他引:0
互联网时代 ,国家和相关企业掌握互联网使用的动态变化情况是非常重要的。本设计采用了多阶段、分层、PPS与等概率相结合的混合抽样方法 ,考虑了时间和经费的限制 ,克服了缺少完整抽样框等困难 ,使抽样的科学性和可操作性得到了较好的结合 ,为中国互联网络信息中心的全国居民上网情况调查提供了切实可行的抽样方案 相似文献
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你也需要蒙特卡罗方法——提高应用水平的若干技巧 总被引:3,自引:1,他引:2
本文是《你也需要蒙特卡罗方法》中的第二篇。文中讨论提高应用水平的一些技巧,涉及模拟模型的选取,提高计算速度或降低抽样方差的一些方法,诸如重要抽样、相关抽样、对偶抽样和分层抽样等。还讨论了模拟中所需的抽样次数的确定和模拟结果的精度评估等实用问题。 相似文献
3.
王正向 《数学的实践与认识》1987,(4)
本文把[2,3]关于离散样本顺序量的理论同概率分布曲线法作了比较,找出了它们在本质上的联系;并用时域抽样定理把前者的结论推广到后者,从而给出了所述Δ_i、E_i 统计特性的定量表述和实践中所用概率分布曲线法参数估值精度的极限界限.最后利用所得结果对一种典型动态测量数据的处理方法进行了改进,以期提高精度,简化计算. 相似文献
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大数据背景下,对于抽样调查的必要性和重要性,目前还存在一定争论.文章定义了两种类型的大数据场景,一种是现有数据量海量的情况;另一种是现有抽样框名录海量的情况.对于抽样框名录海量的情况下,抽样调查既必要又重要.文章基于某平台类企业的海量抽样框名录,对该平台类企业关心的问题采用目录抽样的方法进行抽样调查研究,并考虑了样本轮... 相似文献
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均值误差的随机加权分布的渐近展开——非独立同分布情况 总被引:1,自引:0,他引:1
§1.前言和摘要本文作者在[1]中利用随机加权的方法对均值的误差的分布进行了计算.这种方法是Efron之Bootstrap方法之推广.继[1]以后,涂冬生和郑忠国又讨论了随机加权分布的渐近展开的问题.[2]中的论证进一步说明了随机加权法的优良性.正如[1]中所说的,随机加权法是很有前途的一种计算方法.它与Bootstrap方法比较起来,具有许多优点.其中一个很重要的特点是它抛弃了重新抽样的想法,因此它可以不受独立同分布模型的约束.本文 相似文献
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混合截尾试验是定时和定数截尾的一种有用的推广。本文研究了Weibull分布和混合截尾试验的一次抽样方案,并对可靠决策损失函数给出了贝叶斯风险的显式表达式。比较陈和林的模型(1999),我们得混合截尾试验的抽样方案于定时抽样方案。 相似文献
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非线性再生散度模型是指数族非线性模型、广义线性模型和正态非线性回归模型的推广和发展,唐年胜等人研究了该模型参数的极大似然估计及其统计诊断。本文基于Gibbs抽样和MH抽样算法讨论非线性再生散度模型参数的Bayes估计。模拟研究和实例分析被用来说明该方法的有效性。 相似文献
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对于无放回抽样,教材(人教版,高中数学选修Ⅱ)介绍了三种抽样方法,即简单随机抽样、系统抽样和分层抽样.这三种抽样方法的共同基础是,抽样过程中每个个体被抽取的概率相等.教材对这一共同基础给出了证明.系统抽样和分层抽样都以简单随机抽样为基础,但这两种抽样指标的确定依据及其中所述“更充分地反映总体的情况”,教材并没有给出解释,学生感到难以理解. 相似文献
11.
S. M. Saulin 《Theoretical and Mathematical Physics》2017,191(1):537-557
We show that the potential coupling of classical mechanical systems (an oscillator and a heat bath), one of which (the heat bath) is linear and infinite-dimensional, can provoke energy dissipation in a finitedimensional subsystem (the oscillator). Under natural assumptions, the final dynamics of an oscillator thus reduces to a tendency toward equilibrium. D. V. Treschev previously obtained results concerning the dynamics of an oscillator with one degree of freedom and a quadratic or (under some additional assumptions) polynomial potential. Later, A. V. Dymov considered the case of a linear oscillator with an arbitrary (finite) number of degrees of freedom. We generalize these results to the case of a heat bath (consisting of several components) and a multidimensional oscillator (either linear or nonlinear). 相似文献
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A. L. Kuzemsky 《Theoretical and Mathematical Physics》2018,194(1):30-56
We consider some principal problems of nonequilibrium statistical thermodynamics in the framework of the Zubarev nonequilibrium statistical operator approach. We present a brief comparative analysis of some approaches to describing irreversible processes based on the concept of nonequilibrium Gibbs ensembles and their applicability to describing nonequilibrium processes. We discuss the derivation of generalized kinetic equations for a system in a heat bath. We obtain and analyze a damped Schrödinger-type equation for a dynamical system in a heat bath. We study the dynamical behavior of a particle in a medium taking the dissipation effects into account. We consider the scattering problem for neutrons in a nonequilibrium medium and derive a generalized Van Hove formula. We show that the nonequilibrium statistical operator method is an effective, convenient tool for describing irreversible processes in condensed matter. 相似文献
14.
David Taj 《Annales Henri Poincare》2010,11(7):1303-1339
We study the van Hove limit for master equations on a Banach space, and propose a contraction semigroup as limit dynamics.
The generator has a Lindblad form if specialized to C*-algebras, is always well defined irrespectively of the subsystem spectrum, includes first-order contributions, and returns
Davies averaged generator, when the latter is defined. The theory is applied to the case of a free particle in contact with
a heat bath. 相似文献
15.
《Applied Mathematical Modelling》2002,26(2):203-221
The performance of an iron-bath reactor has been studied using a comprehensive numerical model that combines a computational fluid dynamics approach for the gas phase and a heat and mass balance model for the bath. The model calculates:
- •coal, ore, flux and oxygen consumption;
- •post-combustion ratio (PCR);
- •heat-transfer efficiency (HTE);
- •off-gas temperature and composition;
- •heat transfer and chemical reactions between gas and iron and slag droplets; and
- •heat transfer between gas and bath, refractories and lance.
16.
We use the nonequilibrium Liouville equation to derive the master equation for the reduced statistical operator in a heat
bath represented by a many-particle environment. Focusing on the case of a weak system-bath coupling, we consider the Born-Markov
approximation of the master equation and compare the result to different approaches. The master equation is elaborated for
the special case of an atom as a reduced system in a plasma background. We find that the dynamical structure factor determines
the effect of the plasma on the reduced system. We consider the operator equation in the atomic eigenstate and in the phase-space
representation, which yields two limiting cases: quantum mechanical behavior similar to the isolated atom for the lower strongly
bound levels and a semiclassical one for highly excited Rydberg levels.
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Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 154, No. 1, pp. 31–62, January, 2008. 相似文献
17.
We consider the problem of the dissipative dynamics of a harmonic oscillator linearly coupled to a heat bath. We demonstrate
that in addition to the mean energy, there exists an infinite series of quantities exponentially decreasing in time that are
means of polynomials of the system Hamiltonian. We obtain the spectrum of the corresponding relaxation times. We propose a
method for representing the time characteristics of the system in terms of operators corresponding to the exponentially damped
observables. We obtain a recurrence relation for these operators. 相似文献
18.
Hsin-Ping Chu Chieh-Li Chen 《Communications in Nonlinear Science & Numerical Simulation》2008,13(8):1605-1614
In this paper, the differential transform is employed to discuss the behaviors of nonlinear heat conduction problem. A hybrid method of differential transform and finite difference approach is proposed to solve the transient responses of a nonlinear heat conduction problem. Different parameters of the equation and boundary conditions are considered to verify the feasibility of the proposed method to such problems. Simulation results are illustrated and discussed in comparison with the linear case. The results show that the hybrid method can achieve good results for such problems. 相似文献
19.
《Chaos, solitons, and fractals》2001,12(14-15):2631-2638
We consider two non-interacting systems embedded in a heat bath. If they remain dynamically independent, physical inconsistencies are avoided only if the single-system reduced dynamics is completely positive also beyond the weak-coupling limit. 相似文献
20.
Normalized Dynamic Characterization and Application of Multiple Heat Storage Materials Based on Standard Thermal Resistance北大核心CSCD
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基于标准热阻和能量流法,推导出储热材料与换热流体的瞬态换热热阻,通过类比电路分析法,获得了储热-换热过程的瞬态热量流模型及动态响应时间常数。进一步引入节点温度,重新定义换热热阻,获得了储热与换热过程耦合的三阶电路瞬态热量流模型,求解得到了加热、储热和释热三类时间常数,可用于协同表征储热材料中储热与释热的快慢程度,从而实现了多类储热材料的归一化动态表征。通过数值模拟验证与应用对比分析,发现基于多时间常数的归一化动态模型用于表征储热材料的动态特性是可行的,可直接对不同换热、储热材料进行对比分析。案例分析发现与固体储热材料换热时,液态金属的动态换热能力优于熔融盐,而相比于水蒸气和CO2,空气与陶瓷材料换热能更快达到稳态。 相似文献