meshless implementation of the geometrically exact kirchhoff love shell theory summary in the present paper a meshless generalized multiple fixed least squares implementation of the geometrically exact kirchhoff love shell theory is described the material time derivative of the deformation gradient and the first piola kirchhoff stress tensor are considered as basic conjugate quantities to evaluate the internal power the shell s initial geometry is reproduced exactly by the predefined mapping from a reference plane configuration as a constitutive model a neo hookean material whose functional is altered in compliance with the plane stress condition is chosen the augmented weak form suitable for both interpolative and non interpolative approximations thanks to the imposition of the essential boundary conditions through lagrange multipliers is consistently linearized and the resultant bilinear form proved to be symmetric the appearance of the corner reactions related to the jumps of the pseudo torsion boundary moment requires the inclusion of additional pointwise displacement constraints at the essential boundary corners the importance of these quantities is demonstrated in the numerical tests revealing its positive influence on the displacements and particularly their derivatives up to 3rd order in both linear and nonlinear problems the possibility of incorporation of drilling boundary moment for nonlinear problems was successfully assessed copyright 2014 john wiley sons ltd

multiphysics simulation of flow induced vibrations and aeroelasticity on parallel computing platforms abstract this article describes the application of multiphysics simulation on parallel computing platforms to model aeroelastic instabilities and flow induced vibrations multiphysics simulation is based on a single computational framework for the modeling of multiple interacting physical phenomena within the multiphysics framework the finite element treatment of fluids is based on the galerkin least squares gls method with discontinuity capturing operators the arbitrary lagrangian eulerian ale method is utilized to account for deformable fluid domains the finite element treatment of solids and structures is based on a three field variational principle fully coupled interaction constraints are enforced using the augmented lagrangian method the multiphysics architecture lends itself naturally to high performance parallel computing several applications are presented the importance of capturing the nonlinear effects and accounting for mesh movement is highlighted and the scalability of the software is illustrated

a group theoretic approach to the linear free vibration analysis of shells with dihedral symmetry this paper deals with a group theoretic approach to the finite element analysis of linear free vibrations of shells with dihedral symmetry examples of such shell structures are cylindrical shells conical shells shells with circumferential stiffeners corrugated shells spherical shells etc the group theoretic approach is used to exploit the inherent symmetry in the problem for vibration analysis the group theoretic results give the correct symmetry adapted basis for the displacement field the stiffness matrix k and the mass matrix m are identically block diagonalized in this basis the generalized linear eigenvalue problem of free vibration gets split into independent subproblems due to this block diagonalization the simo element is used in the finite element formulation of the shell equilibrium equations numerical results for natural frequencies and natural modes of vibration of several dihedral shell structures are presented the results are shown to be in very good agreement with those reported in the literature the computational advantages and physical insights due to the group theoretic approach are also discussed

inverse formulation for geometrically exact stress resultant shells the inverse elastostatics method tackles a class of problems in which the deformed geometry and the applied load are known while the initial geometry and the stress in the deformed state are to be determined the method is imperative for many biomechanics applications particularly for image based stress analysis of living organs as the geometry captured by imaging often correspond to a pre deformed configuration 3 4 the computational aspects of inverse elastostatics i e the inverse formulations have been established for general elastic solids 1 2 3 in this work the inverse formulation of thin walled structures modeled as geometrically exact stress resultant shell 5 is presented the inverse formulation builds on a fundamental assumption of the elastic media that the stress depends on local relative motion of the body if either the reference or the deformed configuration is given the other can be found from the elastostatic equilibrium the shell formulation follows the same logic albeit involving shell kinematics and kinetics regardless of the additional assumptions introduced in the shell theory the fundamental premise underlying inverse analysis remains the same in the proposed formulation the inverse problem is solved by using the standard week form of shell balance equations which are yet parameterized and linearized in terms of the inverse motion to facilitate an effective numerical computation an invariant approached is used to formulate the constitutive equations a consistent reduction from 3d energy function is also introduced numerical examples involving both isotopic and anisotropic materials are provided for validating the formulation applications to several biological thin walled structures demonstrate the practical utility of the method

on non linear dynamics of shells implementation of energy momentum conserving algorithm for a finite rotation shell model continuum and numerical formulations for non linear dynamics of thin shells are presented in this work an elastodynamic shell model is developed from the three dimensional continuum by employing standard assumptions of the first order shear deformation theories motion of the shell directior is described by a singularity free formulation based on the rotation vector temporal discretization is performed by an implicit one step second order accurate time integration scheme in this work an energy and momentum conserving algorithm which exactly preserves the fundamental constants of the shell motion and guaranties unconditional algorithmic stability is used it may be regarded as a modification of the standard mid point rule spatial discretization is based on the four noded isoparametric element particular attention is devoted to the consistent linearization of the weak form of the initial boundary value problem discretized in time and space in order to achieve a quadratic rate of asymptotic convergence typical for the newton raphson based solution procedures an unconditionally stable time finite element formulation suitable for the long term dynamic computations of flexible shell like structures which may be undergoing large displacements large rotations and large motions is therefore obtained a set of numerical examples is presented to illustrate the present approach and the performance of the isoparametric four noded shell finite element in conjunction with the implicit energy and momentum conserving time integration algorithm

on a stress resultant geometrically exact shell model part vii shell intersections with dof finite element formulations abstract if the mid surface of a shell is smooth the classical theory describes the orientation of the director field attached to the mid surface by two independent rotational degrees of freedom at a shell intersection where this smoothness assumption no longer holds it is shown that the director field in the full nonlinear continuum shell equations must be necessarily described by three degrees of freedom this added degree of freedom however is totally unrelated to the so called drill rotation widely used as a means of tackling the shell intersection problem a computational procedure involving a trivial modification of the global singularity free update procedure described in part iii of this work is described which completely resolves the shell intersection problem without introducing drill springs or related ad hoc devices the proposed approach leaves unchanged standard finite element formulations in terms of 5 dof node affects only the global update formulae and exhibits excellent performance as illustrated by representative numerical simulations

on the parametrization of finite rotations in computational mechanics a classification of concepts with application to smooth shells this paper concerns the computational treatment of large rotations with application to the finite element discretisation of smooth shells formulations based on various rotational parametrizations are reviewed and classified with respect to their update structure category ii is based on total rotational degrees of freedom leading to an additive update structure whereas category i relies on linearized rotational degrees of freedom leading to a multiplicative update structure based on this classification new formulations are developed among them are the rodrigues formula applied within category ii with additive update structure for the two components of the rotation vector and two successive elementary rotations in the sense of euler angles applied within category i yielding a singularity free formulation the numerical examples confirm that every rotational parametrization when applied within category ii leads to singularities whereas the application within category i enables the calculation of overall rotations unrestricted in size without any singularity

nonlinear dynamic analysis of shells with the triangular element tric abstract tric is a facet triangular shell element which is based on the natural mode method it has been shown that the tric shell element satisfies the individual element test and in the framework of the nonconsistent formulation the convergence requirements are fulfilled while it has been proved to be very efficient in linear and nonlinear static problems moreover another major advantage in the formulation of this element is the incorporation of the transverse shear deformations in a way that defies the shear locking phenomenon in this work the derivation of the consistent and lumped mass matrices of the tric element is presented so that it can be used in linear and nonlinear dynamic problems both translational and rotational inertia are included in the consistent mass matrix which is conceived using kinematical and geometrical arguments consistent with the assumed natural rigid body and straining modes of the element all the kinematical and geometrical arguments that are invoked for the derivation of the consistent mass matrix are briefly presented moreover two formulations of the lumped mass matrix of tric are derived the first formulation is based entirely on geometrical considerations whereas the second is based on lumping the consistent mass matrix of tric finally the element s robustness and accuracy will be shown by applying it to properly selected benchmark examples of nonlinear shell dynamics while its computational efficiency will be demonstrated by comparing the cpu performance of the element with the other available shell elements

generalized levitin polyak well posedness in constrained optimization in this paper we consider levitin polyak type well posedness for a general constrained optimization problem we introduce generalized levitin polyak well posedness and strongly generalized levitin polyak well posedness necessary and sufficient conditions for these types of well posedness are given relations among these types of well posedness are investigated finally we consider convergence of a class of penalty methods and a class of augmented lagrangian methods under the assumption of strongly generalized levitin polyak well posedness

conservative numerical methods for x f x abstract two distinctly different numerical methods are developed for solving the conservative initial value problem x f x x o dot x o both methods conserve exactly the same total energy as does the given differential equation computer examples are described and

geometrically exact sandwich shells the static case the present formulation offers a general method for analyzing the static response of geometrically exact sandwich shells undergoing large deformation the layer directors at a point in the reference surface are connected to each other by universal joints and form a chain of rigid links finite rotations of the directors in every layer are allowed with shear deformation independently accounted for in each layer the thickness and the length of each layer can be arbitrary thus allowing the modeling of an important class of multilayer structures having ply drop offs the present formulation is thus suitable to model shell structures with patches of constrained viscoelastic materials or of piezoelectric materials the nonlinear weak form of the governing equations of equilibrium is constructed here and then the linearization of the weak form and the associated inextensible directors update are derived leading to a symmetric tangent stiffness matrix a galerkin finite element projection of the linearized equilibrium equations results in a system of nonlinear algebraic equations in which the interpolation accounts for the finite rotations of the directors we present extensive numerical examples including sandwich shells with three identical layers and ply drop offs to illustrate the applicability and versatility of the proposed formulation

a generalized m interval partition detector with application to signal detection in impulsive noise a new class of detectors based on orthonormal polynomial approximations in properly selected subintervals is considered it is found that many well known robust detectors are subclasses of the new class in addition to the properties possible implementation of the detectors is presented exten sive numerical evaluations indicate that the new detector al ways maintains a nearly optimum performance in the context of are regardless of the degree of noise contamination and is insignificantly influenced by unspecified variations in noise densities moreover the new detectors are realizable in real time several suggestions are made for further improvement of the new detectors

a four node corotational quadrilateral elastoplastic shell element using vectorial rotational variables four node corotational quadrilateral elastoplastic shell element summary a four node corotational quadrilateral elastoplastic shell element is presented the local coordinate system of the element is defined by the two bisectors of the diagonal vectors generated from the four corner nodes and their cross product this local coordinate system rotates rigidly with the element but does not deform with the element as a result the element rigid body rotations are excluded in calculating the local nodal variables from the global nodal variables the two smallest components of each nodal orientation vector are defined as rotational variables leading to the desired additive property for all nodal variables in a nonlinear incremental solution procedure different from other existing corotational finite element formulations the resulting element tangent stiffness matrix is symmetric owing to the commutativity of the local nodal variables in calculating the second derivative of strains with respect to these variables for elastoplastic analyses the maxwell huber hencky von mises yield criterion is employed together with the backward euler return mapping method for the evaluation of the elastoplastic stress state the consistent tangent modulus matrix is derived to eliminate locking problems we use the assumed strain method several elastic patch tests and elastoplastic plate shell problems undergoing large deformation are solved to demonstrate the computational efficiency and accuracy of the proposed formulation copyright 2013 john wiley sons ltd

generalized nash games and quasi variational inequalities abstract a generalized nash game is an n person noncooperative game with nondisjoint strategy sets other names for this game form include social equilibria and pseudo nash games this paper explores both the qualitative and quantitative properties of such games through the use of quasi variational inequality theory several interesting relationships between the variational and quasi variational inequality forms of this class of games are described and the practical implementation of generalized nash games are explored at length

a new energy and momentum conserving algorithm for the non linear dynamics of shells a numerical time integration scheme for the dynamics of non linear elastic shells is presented that simultaneously and independent of the time step size inherits exactly the conservation laws of total linear total angular momentum as well as total energy the proposed technique generalizes to non linear shells recent work of the authors on non linear elastodynamics and is ideally suited for long term large scale simulations the algorithm is second order accurate and can be immediately extended with no modification to a fourth order accurate scheme the property of exact energy conservation induces a strong notion of non linear numerical stability which manifests itself in actual simulations

conservation properties of a time fe method part i time stepping schemes forn body problems in the present paper one step implicit integration algorithms for the n body problem are developed the time stepping schemes are based on a petrov galerkin finite element method applied to the hamiltonian formulation of the n body problem the approach furnishes algorithmic energy conservation in a natural way the proposed time finite element method facilitates a systematic implementation of a family of time stepping schemes a particular algorithm is specified by the associated quadrature rule employed for the evaluation of time integrals the influence of various standard as well as non standard quadrature formulas on algorithmic energy conservation and conservation of angular momentum is examined in detail for linear and quadratic time elements copyright 2000 john wiley sons ltd

levitin polyak well posedness of generalized quasivariational inequalities with functional constraints abstract in this paper we study levitin polyak type well posedness for generalized quasivariational inequality problems with explicit constraints four types of levitin polyak well posedness will be introduced various criteria and characterizations will be derived for these types of levitin polyak well posedness

an energy momentum consistent method for transient simulations with mixed finite elements developed in the framework of geometrically exact shells summary in this paper a mixed variational formulation for the development of energy momentum consistent emc time stepping schemes is proposed the approach accommodates mixed finite elements based on a hu washizu type variational formulation in terms of displacements green lagrangian strains and conjugated stresses the proposed discretization in time of the mixed variational formulation under consideration yields an emc scheme in a natural way the newly developed methodology is applied to a high performance mixed shell finite element the previously observed robustness of the mixed finite element formulation in equilibrium iterations extends to the transient regime because of the emc discretization in time copyright 2016 john wiley sons ltd

conservation properties of a time fe method part iii mechanical systems with holonomic constraints a galerkin based discretization method for index 3 differential algebraic equations pertaining to finite dimensional mechanical systems with holonomic constraints is proposed in particular the mixed galerkin mg methodis introduced which leads in a natural way to time stepping schemes that inherit major conservation properties of the underlying constrained hamiltonian system namely total energy and angular momentum in addition to that the constraints on the configuration level and on the velocity momentum level are fulfilled exactly the application of the mg method to specific mechanical systems such as the pendulum rigid body dynamics and the coupled motion of rigid and flexible bodies is presented related numerical examples are investigated to evaluate the numerical performance of the mg 1 and mg 2 method

the hamiltonian structure of nonlinear elasticity the material and convective representations of solids rods and plates it is our belief that a thorough understanding of the mathematical underpinnings of elasticity is crucial to its analytical and numerical implementation for example in the analysis of rotating structures the coupling of the equations for geometrically inexact models obtained by linearization or other approximations with those for rotating rigid bodies can easily lead to misleading artificial softening effects that can significantly alter numerical results see simo and vuquoc 1986c especially equations 3 and 5 in this paper we consider fully nonlinear geometrically exact models for rods plates and shells which take into account shear and torsion as well as the usual bending effects in traditional rod and plate models these models can be obtained either from the three dimensional theory by a systematic use of projection methods see e g antman 1972 and naghdi 1972 or by a direct approach within the context of cosserat continuum remarkably the two approaches lead to essentially the same form of the governing field equations in the present context we have chosen as a model problem a particular rod model which may be regarded as an extension of the classical kirchhoff love model see love 1944 to include shear deformations as in

well posedness of generalized mixed variational inequalities inclusion problems and fixed point problems we introduced and studied the concept of well posedness to a generalized mixed variational inequality some characterizations are given under suitable conditions we prove that the well posedness of the generalized mixed variational inequality is equivalent to the well posedness of the corresponding inclusion problem we also discuss the relations between the well posedness of the generalized mixed variational inequality and the well posedness of the corresponding fixed point problem finally we derive some conditions under which the generalized mixed variational inequality is well posed

energy conserving and decaying algorithms in non linear structural dynamics a generalized formulation of the energy momentum methodwill be developed within the framework of the generalizedmethodwhich allows at the same time guaranteed conservation or decay of total energy and controllable numerical dissipation of unwanted high frequency response furthermore the latter algorithm will be extended by the consistently integrated constraints of energy and momentum conservation originally derived for the constraint energy momentum algorithm the goal of this general approach of implicit energyconserving and decaying time integration schemes is to compare these algorithms on the basis of an equivalent notation by the means of an overall algorithmic design and hence to investigate their numerical properties numerical stability and controllable numerical dissipation of high frequencies will be studied in application to non linear structural dynamics among the methods considered will be the newmark method the classical methods the energy momentum methodwith and without numerical dissipation the constraint energymomentum algorithm and the constraint energy method copyright 1999 john wiley sons ltd

asymptotically optimum finite memory detectors in spl phi mixing dependent processes the design of a finite memory partition system for the detection of a constant signal in spl phi mixing noise is investigated it is found that the new detector converges to the locally optimal finite memory practically intractable detector characterized by a multidimensional fredholm integral equation of the second kind the new detector encompasses many classes of known detectors numerical calculations demonstrate that the finite memory detector compares favorably using asymptotic relative efficiency as a fidelity criterion to other classes of detectors even if extremes of dependent noise distributions are considered the same calculations also suggest that a dependent process may be treated as an m dependent process in finite memory detectors without causing significant detrimental effects provided m is sufficiently large to reduce excessive computational complexity a priori knowledge regarding properties of system parameters such as matrix symmetry as well as noise distributions especially gaussian and its independently nonlinear transformations are exploited generalizations and extensions of the proposed detectors are also discussed the operation of the detector may be easily extended to include adaptability and or sequential operation

constraint energy momentum algorithm and its application to non linear dynamics of shells abstract a modified time integration method is developed for non linear structural dynamics combining controllable algorithmic dissipation of higher modes and at the same time conservation of energy as well as linear and angular momentum although these features seem to be actually inconsistent numerical stability with large time steps for dynamic buckling and snap through problems as well as for dynamical systems with smooth solutions is guaranteed arbitrary implicit one step time integration schemes with newmark approximations are suitable for use as basic algorithms for the proposed method the desired conservation attributes are obtained if the basic algorithm is augmented by energy and momentum constraints the potential of the suggested algorithm is demonstrated by selected applications to non linear dynamics of shell structures

generalized energy momentum method for non linear adaptive shell dynamics in the present study a generalization of the energy momentum method denoted by generalized energy momentum method applied to the non linear dynamics of shells will be developed within the framework of the generalized a method this algorithmic environment contains the unconditionally stable energy momentum method and its numerically damped version as well as the classical newmark and a methods as special cases in order to control the size of the time steps of the integration scheme with respect to accuracy and eaciency an adaptive time stepping procedure based on local a posteriori error estimation will be improved for non linear dynamical systems and applied to the proposed class of algorithms the spatial discretization is realized by an eight noded finite shell element of reissner mindlin type including an extensible shell director field permitting the application of three dimensional material laws the original formulation of this finite element will be developed for non linear dynamic analysis and adapted for the employment within the introduced energy conserving decaying time integration scheme 1999 elsevier science s a all rights reserved

on the boundary conditions of the geometrically nonlinear kirchhoff love shell theory abstract the present paper addresses the problem of establishing the boundary conditions of a geometrically nonlinear thin shell model especially the kinematic ones our model is consistently derived from general 3d continuum mechanics statements generalized cross sectional strains and stresses are based on the deformation gradient and the first piola kirchhoff stress tensor since only the bending deformation is included in this model no special technique needs to be adopted in order to avoid shear locking the theory is derived in such a way that any material model can be considered as a constitutive relation once the zero transverse normal stress assumption is properly taken into account special attention is given to the question of devising the appropriate shell boundary conditions several parameters are proposed to characterize the boundary rotation for an arbitrary spatial shell configuration the appearance of corner concentrated forces related to jumps of torsion moments is captured and justified a weak form of the equilibrium is presented which is suitable for implementation by means of any numerical technique that provides c 1 continuity approximation it is prone to be used with both interpolative like the finite element method and non interpolative methods like the element free galerkin method the latter is used to exemplify the proposed approach

an excursion into large rotations the present discourse develops an enlarged exploration of the matrix formulation of finite rotations in space initiated in 1 it is shown how a consistent but subtle matrix calculus inevitably leads to a number of elegant expressions for the transformation or rotation matrix t appertaining to a rotation about an arbitrary axis also analysed is the case of multiple rotations about fixed or follower axes particular attention is paid to an explicit derivation of a single compound rotation vector equivalent to two consecutive arbitrary rotations this theme is discussed in some detail for a number of cases semitangential rotations for which commutativity holds first proposed in 2 3 are also considered furthermore an elementary geometrical analysis of large rotations is also given finally we deduce in an appendix using a judicious reformulation of quarternions the compound pseudovector representing the combined effect of n rotations in the author s opinion the present approach appears preferable to a pure vectorial scheme and even more so to an indicial formulation and is computationally more convenient

a co rotational element time integration strategy for non linear dynamics new procedures are proposed for implicit dynamic analysis using the finite element method the main aim is to give stable solutions with significant rigid body motions in particular rotations in contrast to most conventional approaches the time integration strategy is closely linked to the element technologies with the latter involving a form of co rotational procedure for the undamped situation one of the solution procedures leads to an algorithm that exactly conserves energy when constant external forces are applied i e with gravity loading

the generalized quasi variational inequality problem with applications a new problem called the generalized quasi variational inequality problem is introduced this new problem extends all the existing variational inequality problems in finite dimensional spaces and enlarges the class of problems that can be approached by the variational inequality theory some existence results without convexity assumptions are presented applications to mathematical and equilibrium programming are given

on a stress resultant geometrically exact shell model part vi conserving algorithms for non linear dynamics in parts i to v of the present work the formulation and finite element implementation of a non linear stress resultant shell model are considered in detail this paper is concerned with the extension of these results to incorporate completely general non linear dynamic response of special interest here is the dynamics of very flexible shells undergoing large overall motion which conserves the total linear and angular momentum and for the hamiltonian case the total energy a main goal of this paper is the design of non linear time stepping algorithms and the construction of finite element interpolations which preserve exactly these fundamental constants of motion it is shown that only a very special class of algorithms namely a formulation of the mid point rule in conservation form exactly preserves the total linear and angular momentum for the hamiltonian case a somewhat surprising result is proved regardless of the degree of non linearity in the stored energy function a generalized mid point rule algorithm always exists which exactly conserves energy the conservation properties of a time stepping algorithm need not and in general will not be preserved by the spatial discretization precise conditions which ensure preservation of these conservation properties are derived a number of numerical simulations are presented which illustrate the exact conservation properties of the proposed methodology

finite difference calculus invariant structure of a class of algorithms for the nonlinear klein gordon equation in a previous work the authors have presented a formalism for deriving systematically invariant symmetric finite difference algorithms for nonlinear evolution differential equations that admit conserved quantities this formalism is herein cast in the context of exact finite difference calculus the algorithms obtained from the proposed formalism are shown to derive exactly from discrete scalar potential functions using finite difference calculus in the same sense as that of the corresponding differential equation being derivable from its associated energy function a conserved quantity a clear ramification of this result is that the derived algorithms preserve certain discrete invariant quantities which are the consistent counterpart of the invariant quantities in the continuous case results on the nonlinear stability of a class of algorithms that are derived using the proposed formalism and that preserve energy or linear momentum are discussed in the context of finite difference calculus some

on the use of geometrically exact shells in a conserving framework for flexible multibody dynamics abstract the present work deals with the design of energy momentum conserving schemes for flexible multibody dynamics the proposed approach is based on nonlinear finite element methods for the space discretization of flexible bodies in particular the focus is on geometrically exact shells relying on reissner mindlin kinematics it is shown that the equations of motion pertaining to the semi discrete shell formulation can be written in the form of differential algebraic equations daes the daes provide a uniform framework for a rotationless description of flexible multibody dynamics the use of rotational parameters is circumvented throughout the discretization process in space and time the rotationless description facilitates the straightforward incorporation of geometrically exact shells and beams into a multibody framework in addition to that the advocated approach makes possible the design of a uniform energy momentum conserving time stepping scheme for general multibody systems numerical examples demonstrate the excellent numerical stability properties of the present scheme moreover comparison is made with more traditional formulations based on rotational parameters

a new one point quadrature quadrilateral shell element with drilling degrees of freedom abstract in this paper we discuss the development of a new four node general shell element with single point quadrature used for the analysis of non linear geometrical and material problems one of the main features of the present development is the implementation of a rotation component around the shell normal i e drilling rotation to belytschko s family of shell elements thus at each node six degrees of freedom i e three translations and three rotations make the element easy to connect to space beams stiffeners or intersecting shells a projection scheme for warping correction is proposed so that the element is accurate for both flat and warped configurations all locking phenomena such as transverse shear in plane shear and membrane locking are controlled by an assumed strain method also a physical stabilization approach for control of spurious zero energy modes is proposed without requiring any artificial stabilization parameters this approach is inexpensive and accurate because it updates and stores hourglass stresses only at the mid surface rather than at all the integration points through the shell thickness to demonstrate the features of the new shell element it was applied to the analysis of large scale non linear static dynamic and impact problems using elastic isotropic anisotropic elastoplastic and composite damage models the element performed well for the problems that sometimes cause difficulties for other shell element techniques

hadamard and strong well posedness for convex programs it is proved that hadamard well posedness of a constrained convex optimization problem with respect to attouch wets convergence on the data implies in general its strong and hence tykhonov well posedness an example is given showing that the opposite implication fails without assuming an appropriate constrained qualification condition

the epi distance topology continuity and stability results with applications to convex optimization problems let i x denote the proper lower semicontinuous convex functions on a banach space x equipped with the completely metrizable topology of uniform convergence of distance functions on bounded sets we show subject to some standard constraint qualifications that the operations of addition and restriction are continuous these results are applied to convex well posed optimization problems as well as to convergence of approximated solutions in infinite dimensional convex programming to linear functionals exposing convex sets and to metric projections also for any given function in i x we obtain results regarding the convergence of its inf convolution with smoothing kernels

on the asymptotic efficiencies of robust detectors two methods are considered for comparing the asymptotic efficiencies of robust detectors in the problem of detecting coherent signals in additive noise the first of these methods considers the relative detector sample sizes for a fixed value of the detector power while the second method considers the relative detector sample sizes for a fixed value of the local detector power as measured by the local values of the slopes or curvatures of the detector power functions these measures of efficiency are variations of the asymptotic relative efficiencies ares of pitman and blomqvist respectively adapted to the robust detection problem these two approaches are used to compare the performance of robust nonlinear correlators to that of robust m detectors in both one sided and two sided detection problems under an epsilon contaminated mixture model for uncertainty in the noise statistics both measures of are fixed power and fixed local power indicate that the robust nonlinear correlator outperforms the robust m detector for this type of model however the fixed local power are is shown to be more useful in measuring the degree to which the robust nonlinear correlator is more efficient

unconditionally stable algorithms for rigid body dynamics that exactly preserve energy and momentum we show that for rigid body dynamics the mid point rule formulated in body co ordinates exactly conserves energy and the norm of the angular momentum for incremental force free motions but fails to conserve the direction of the angular momentum vector further we show that the mid point rule formulated in the spatial representation is in general physically and geometrically meaningless an alternative algorithm is developed which exactly preserves energy and the total spatial angular momentum in incremental force free motions the implicit version of this algorithm is unconditionally stable and second order accurate the explicit version conserves exactly angular momentum in incremental force free motions numerical simulations are presented which illustrate the excellent performance of the proposed procedure even for incremental rotations over 65 degrees the procedure is directly applicable to transient dynamic calculations of geometrically exact rods and shells

a class of memoryless robust detectors in dependent noise a new general approach to the formulation of a detector in non gaussian noise satisfying the strong mixing condition is introduced the only statistical knowledge required for the optimal design is a set of parameters which can be estimated from data and recursively updated this eliminates the requirement that exact distributions be known and leads naturally to efficient adaptive detectors