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1.
Shinto Eguchi 《Annals of the Institute of Statistical Mathematics》1986,38(1):385-398
Summary This paper is concerned with estimation for a subfamily of exponential-type, which is a parametric model with sufficient statistics.
The family is associated with a surface in the domain of a sufficient statistic. A new estimator, termed a projection estimator,
is introduced. The key idea of its derivation is to look for a one-to-one transformation of the sufficient statistic so that
the subfamily can be associated with a flat subset in the transformed domain. The estimator is defined by the orthogonal projection
of the transformed statistic onto the flat surface. Here the orthogonality is introduced by the inverse of the estimated variance
matrix of the statistic on the analogy of Mahalanobis's notion (1936,Proc. Nat. Inst. Sci. Ind.,2, 49–55). Thus the projection estimator has an explicit representation with no iterations. On the other hand, the MLE and
classical estimators have to be sought as numerical solutions by some algorithm with a choice of an initial value and a stopping
rule. It is shown that the projection estimator is first-order efficient. The second-order property is also discussed. Some
examples are presented to show the utility of the estimator. 相似文献
2.
Samir Elhedhli 《Operations Research Letters》2005,33(6):615-624
We consider a class of nonlinear knapsack problems with applications in service systems design and facility location problems with congestion. We provide two linearizations and their respective solution approaches. The first is solved directly using a commercial solver. The second is a piecewise linearization that is solved by a cutting plane method. 相似文献
3.
有资格限制的指派问题的求解方法 总被引:3,自引:0,他引:3
在实际的指派工作中,常会遇到某个人有没有资格去承担某项工作的问题,因此,本建立了有资格限制的指派问题的数学模型。在此数学模型中,将效益矩阵转化为判定矩阵,由此给出了判定此种指派问题是否有解的方法;在有解的情况下,进一步将效益矩阵转化为求解矩阵,从而将有资格限制的指派问题化为传统的指派问题来求解。最后给出了一个数值例子来说明这样的处理方法是有效的。 相似文献
4.
Numerical computation of stability and detection of Hopf bifurcations of steady state solutions of delay differential equations 总被引:3,自引:0,他引:3
The characteristic equation of a system of delay differential equations (DDEs) is a nonlinear equation with infinitely many
zeros. The stability of a steady state solution of such a DDE system is determined by the number of zeros of this equation
with positive real part. We present a numerical algorithm to compute the rightmost, i.e., stability determining, zeros of
the characteristic equation. The algorithm is based on the application of subspace iteration on the time integration operator
of the system or its variational equations. The computed zeros provide insight into the system’s behaviour, can be used for
robust bifurcation detection and for efficient indirect calculation of bifurcation points.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
6.
The paper is concerned with the problem of stabilizing a spherical robot of combined type during its motion. The focus is on the application of feedback for stabilization of the robot which is an example of an underactuated system. The robot is set in motion by an internal wheeled platform with a rotor placed inside the sphere. The results of experimental investigations for a prototype of the spherical robot are presented. 相似文献
7.
《Journal of Applied Mathematics and Mechanics》2006,70(4):599-610
The torsion of a composite cone that has a centre of rotation at its apex is investigated in a spherical system of coordinates. A composite cone is a cone with one shear modulus, inserted into a conical funnel having another shear modulus and with ideal mechanical contact between its surface and the inner surface of the conical funnel. The auxiliary problem of a composite cone with its apex truncated by a spherical surface is considered first. The outer surface of such a conical body is not loaded, but a load that reduces to a torque is applied to its spherical surface. The auxiliary problem is reduced to a one-dimensional discontinuous boundary-value problem using a specially constructed integral transformation. The exact solution of this boundary-value problem is constructed. The limit is then taken in the solution obtained as the radius of the spherical surface tends to zero for the purpose of obtaining an exact solution of the problem of the torsion of a composite cone that has a centre of rotation at the apex. 相似文献
8.
9.
A. Morro 《Mathematical and Computer Modelling》2002,35(13):335-1389
The standard wave-splitting approach for the wave equation in inhomogeneous media is first reexamined. Next, by analogy with the theory of wave propagation through singular surfaces, a characterization is given for a function in space-time to represent a wave propagating in a direction. The condition is applied in connection with a simple example and found to be quite restrictive. The same problem is then considered in the Fourier-transform domain where the unknown function is an n-tuple satisfying a system of ordinary differential equations. The condition for propagation in a direction is established for the Fourier components. Next, some physical problems are considered which are expressed by partial differential equations or by integro-differential equations. The associated first-order system of equations is examined in terms of the eigenvalues of a matrix. This shows that, for any eigenvalue, the direction of propagation may change with the frequency and that arguments about the dominance of the principal part of the operator may cease to hold. 相似文献
10.
L. Nazarenko L. P. Khoroshun W. H. Müller B. R. Wille 《Mechanics of Composite Materials》2009,45(1):11-20
A model of deformation of stochastic composites subjected to microdamage is developed for the case of orthotropic materials
with microdamages accumulating in the fibers. The composite is treated as a matrix strengthened with elliptic fibers with
orthotropic elastic properties. The fractured microvolumes are modeled by a system of randomly distributed quasi-spherical
pores. The porosity balance equation and relations for determining the effective elastic moduli for the case of a fibrous
composite with orthotropic components are used as the fundamental relations. The fracture criterion is given as a limit value
of the intensity of average shear stresses occurring in the undamaged part of the material, which is assumed to be a random
function of coordinates and is described by the Weibull distribution. Based on an analytical and numerical approach, the algorithm
for determining the nonlinear deformation properties of such a material is constructed. The nonlinearity of composite deformations
is caused by the accumulation of microdamages in the fibers. By using a numerical solution, the nonlinear stress–strain diagrams
for an orthotropic composite in uniaxial tension are obtained.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 45, No. 1, pp. 17–30, January–February, 2009. 相似文献
11.
Monotonicity and stability of periodic polling models 总被引:2,自引:2,他引:0
This paper deals with the stability of periodic polling models with a mixture of service policies. Customers arrive according to independent Poisson processes. The service times and the switchover times are independent with general distributions. The necessary and sufficient condition for the stability of such polling systems is established. The proof is based on the stochastic monotonicity of the state process at the polling instants. The stability of only a subset of the queues is also analyzed and, in case of heavy traffic, the order of explosion of the queues is given. The results are valid for a model with set-up times, and also when there is a local priority rule at the queues.This work was supported in part by a Fellowship of the Netherlands Organization for Scientific Research NWO-ECOZOEK. 相似文献
12.
Time discretization via Laplace transformation of an integro-differential equation of parabolic type
We consider the discretization in time of an inhomogeneous parabolic integro-differential equation, with a memory term of
convolution type, in a Banach space setting. The method is based on representing the solution as an integral along a smooth
curve in the complex plane which is evaluated to high accuracy by quadrature, using the approach in recent work of López-Fernández
and Palencia. This reduces the problem to a finite set of elliptic equations with complex coefficients, which may be solved
in parallel. The method is combined with finite element discretization in the spatial variables to yield a fully discrete
method. The paper is a further development of earlier work by the authors, which on the one hand treated purely parabolic
equations and, on the other, an evolution equation with a positive type memory term.
The authors acknowledge the support of the Australian Research Council. 相似文献
13.
The article considers a method for three-dimensional mathematical modeling of the effect of a bending coastline on the electromagnetic
field. A sea with a peninsula and with a bay is examined. The effect of the peninsula and the bay on the coast skin effect
is investigated. The problem is solved by the integral equation method. 相似文献
14.
The linear stability of the linear Phan-Thien Tanner (PTT) fluid model is investigated for plane Poiseuille flow. The PTT model involves parameters that can be used to fit shear and extensional data, which makes it suitable for describing both polymer solutions and melts. The base flow is determined using a Chebyshev-tau method. The linear stability equations are also discretized using Chebyshev approximations to furnish a generalized eigenvalue problem. The spectrum is shown to comprise a continuous part and a discrete part. The theoretical and numerical results are validated for the UCM and Oldroyd-B models, which are special cases of the PTT model, by comparing with results in the literature. It is demonstrated that the linear PTT fluid is stable to infinitesimal disturbances with respect to the range of shear-thinning, extensional and elasticity parameters considered. The computational efficiency and accuracy of the numerical method are also investigated. 相似文献
15.
16.
This paper is concerned with vibration analysis of rotating systems containing cracks. The flexibility matrix of cracked element is calculated with modified integration limits which is more accurate than conventional methods. The effect of this modification on the coefficients of flexibility matrix is presented for a simple rotor system containing open crack. To model the crack breathing behavior, a new finite element approach is introduced and implemented. Then, the dynamic response of a rotor with a breathing crack is evaluated by using the frequency/time domain approach (short time Fourier transform). The ability of short time Fourier transform to detect small cracks is investigated and compared with the transient response. The results provide a possible basis for an on-line monitoring system. 相似文献
17.
In this paper a mathematical model is developed for the dynamical behaviour of a hydrostatic skeleton. The basic configuration
is taken from the worm-like shape of the medicinal leech. It consists of a sequence of hexahedra with damped elastic springs
as edges to model the various parts of the musculature. The system is stabilized by the constraint of constant volume either
in the whole body or in prescribed compartments. We set up Lagrange's equations of motion with the Lagrange multipliers being
the pressure values in the compartments. The equations of motion lead to a large differential-algebraic system which is solved
by an application of semi-explicit numerical methods. Though the model has not yet been adapted to experimental data, first
simulations with a simplified set of parameters show that it is capable of generating basic movements of the leech such as
crawling and swimming.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
P. Hutar Z. Majer L. Nahlik L. Shestakova Z. Knesl 《Mechanics of Composite Materials》2009,45(3):281-286
The main focus of this paper is a numerical investigation of the fracture behavior of a particulate composite (CaCO3-PP). The composite is modeled as a three-phase continuum and simulated numerically on a microscale by using finite elements.
The propagation of a microcrack in a matrix filled with rigid particles covered by an interphase is analyzed. The stress distribution
is determined for a variety of particle sizes and material properties of the interphase. The final results, in agreement with
experimental data, confirm that the microcrack behavior depends on particle sizes.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 411-418, May-June, 2009. 相似文献
19.
The problem of stationary heat conduction of laminated plates of constant and variable thickness is formulated in the three-dimensional
statement. We reduce the three-dimensional problem to a twodimensional one by the method of initial functions. For plates
with layers of variable thickness, a system of resolving equations with variable coefficients is obtained. The obtained two-dimensional
boundary-value problems are analyzed. For plates with homogeneous layers of constant thickness, we construct a solution in
an analytic form. It is shown that this solution coincides with a solution obtained by the method of separation of variables. 相似文献
20.
A. V. Pozdneev 《Moscow University Computational Mathematics and Cybernetics》2008,32(3):125-134
At present, mass spectrometry is the main analytical technique used in the studies on determining the composition of biomolecules. In such studies, the accuracy of determining the mass values is affected by hidden parameters (Coulomb interaction of analyzed ions with each other and with the walls of the mass-spectrometer trap).The problem consists in the development of a parallel computer code that allows simulation of the millions of charged ions and can reproduce the times of a real experiment in order to study the influence of Coulomb forces on the mass spectrum.The mathematical formulation of the original physical problem is presented. It is proposed to use the particle-in-cell method for simulation of the motion of ion clouds in the trap. The equations of motion are integrated with the use of a scheme with frequency correction. This approach ensures exact reproduction of the cyclotron motion and the ion cyclotron resonance. The Poisson equation is solved at each time step with the use of a method based on the fast Fourier transform. The code is written in Fortran 90 and is parallelized with the use of OpenMP directives.Comparison is performed with a real experiment with protein cytochrome c. The effect of coalescence of spectral peaks is demonstrated at high charge densities in the case of three masses. 相似文献