an interpretive method for moving force identification dynamic load data have been valuable for bridge and pavement design traditional ways to acquire truck axle and gross weight information are expensive and subject to bias and this has led to the development of weigh in motion wim techniques most of the existing wim systems have been developed to measure only the static axle loads this paper aims to introduce a method to identify moving dynamic loads on bridges using the bridge responses caused by such loads a closed form solution can be obtained to identify moving constant loads while numerical methods must be used to identify the time varying moving loads the set of equations that leads to the solution is based on euler s equation of beams a two axle vehicle model is developed to generate the theoretical responses and the corresponding interactive moving forces studies were carried out to check whether the proposed method could recover the original interactive moving forces and the method was found to be feasible

theoretical study of moving force identification on continuous bridges a method to identify moving forces on a continuous bridge has been developed in this paper the bridge is modelled as a bernoulli euler beam and the boundary value problem of the beam is solved to get the exact mode shape functions of the vibrating beam with intermediate supports as the number of spans of the bridge increases the identification accuracy decreases and at the same time more execution time is needed to finish one case study to minimize this problem a method has been developed to identify moving forces on a selected span of interest from the continuous bridge the singular value decomposition svd of the coefficient matrix of the overdetermined equation is used in the solution to evaluate the method simulations of two moving forces on a continuous bridge and on one selected span from the continuous bridge are studied white noise is added to the simulated bending moment and acceleration responses to study the effect of noise in moving forces identification problem for different numbers and arrangements of sensors the results obtained from the simulation study show that the method is effective in identifying moving forces and acceptable results can be obtained

continuous phase modulation part i full response signaling the continuous phase modulation cpm signaling scheme has gained interest in recent years because of its attractive spectral properties data symbol pulse shaping has previously been studied with regard to spectra for binary data and modulation index 0 5 in this paper these results have been extended to the m ary case where the pulse shaping is over a one symbol interval the so called full response systems results are given for modulation indexes of practical interest concerning both performance and spectrum comparisons are made with minimum shift keying msk and systems have been found which are significantly better in e b n 0 for a large signal to noise ratio snr without expanded bandwidth schemes with the same bit error probability as msk but with considerably smaller bandwidth have also been found significant improvement in both power and bandwidth are obtained by increasing the number of levels m from 2 to 4

domain contraction in nonlinear programming minimizing a quadratic concave objective over a polyhedron using linear underestimating approximations and their dual solutions we develop new results for the nonconvex problem of minimizing a quadratic concave function under linear constraints for solving this problem which has such important management applications as economies of scale fixed charge and quadratic assignment problems some results provide and tighten bounds on the global minimum value while others identify the domains of the variables which may be excluded from further consideration this leads to successive reduction of domains containing a global solution called domain contraction and ideally to a solution with the objective value within some acceptable error level for most results specific problem instances are provided to establish their use in theory in practice experience with solving the problems presented here indicates that a combination of the proposed domain contraction via linear underestimation and its dual information with the branch and bound approach offers a computa

delayed decision feedback sequence estimation the authors delayed decision feedback sequence estimation ddfse for uncoded pam signals is considered estimates on the performance of the algorithm are given and simulation results are provided for several examples a more general form of ddfse applicable to coded modulation systems is also presented as an example detection of trellis coded qpsk quadrature phase shift keyed signals over intersymbol interference channels is discussed

a method for globally minimizing concave functions over convex sets a method is described for globally minimizing concave functions over convex sets whose defining constraints may be nonlinear the algorithm generates linear programs whose solutions minimize the convex envelope of the original function over successively tighter polytopes enclosing the feasible region the algorithm does not involve cuts of the feasible region requires only simplex pivot operations and univariate search computations to be performed allows the objective function to be lower semicontinuous and nonseparable and is guaranteed to converge to the global solution computational aspects of the algorithm are discussed

minimizing piecewise concave functions over polyhedra we introduce an iterative method for solving linearly constrained optimization problems whose nonsmooth nonconvex objective function is defined as the pointwise maximum of finitely many concave functions such problems often arise from reformulations of certain constraint structures e g binary constraints finite max min constraints in diverse areas of optimization we state a local optimization strategy which exploits piecewise concavity of the objective function giving rise to a linearized model corrected by a proximity term in addition we introduce an approximate line search strategy based on a curvilinear model which similarly to bundle methods can return either a satisfactory descent or a null step declaration termination at a point satisfying an approximate stationarity condition is proved we embed the local minimization algorithm into a variable neighborhood search scheme and a coordinate direction search heuristic whose aim is to improve the current estimate of the global minimizer

input forces estimation of beam structures by an inverse method an on line recursive inverse method to estimate the input forces of beam structures is presented the inverse method is based on the kalman filter and a recursive least squares algorithm the filter models the system dynamics in a linear set of state equations the state equations of the beam structures were constructed using the finite element method the practicability and accuracy of the estimation method were examined with numerical simulations from which the input forces of a cantilever beam with a lumped mass on the free end were estimated from the output responses in the numerical experiments the cantilever beam was subjected to five types of input forces i e sinusoidal triangular impulse rectangular impulse a series of impulses and random the simulation results show that the inverse method has an excellent performance to estimate the input forces of beam structural systems from the noisy measurements

a dynamic programming algorithm for input estimation on linear time variant systems a time domain input estimation algorithm for linear systems with general time varying parameters is developed the algorithm is an extension of an existing approach for time invariant state space models and several new features such as higher order input approximations and an extended time variant output relation including direct input influence are introduced numerical examples are given to illustrate the new features and show that the algorithm is valid in a general time variant setting in particular excellent results are obtained for an ill posed moving force identification problem with noise contaminated data treated with tikhonov regularization

a list type reduced constraint generalization of the viterbi algorithm the viterbi algorithm va an optimum decoding rule for a q ary trellis code of constraint length k operates by taking the best survivor from each of q k 1 lists of candidates at each decoding step a generalized va gva is proposed that makes comparisons on the basis of a label of length l l leq k it selects incorporating the notion of list decoding the s best survivors from each of q l 1 lists of candidates at each decoding step coding theorems for a discrete memoryless channel are proved for gva decoding and shown to be natural generalizations of those for va decoding an example of intersymbol interference removal is given to illustrate the practical benefits that the gva can provide

d c sets d c functions and nonlinear equations ad c set is a set which is the difference of two convex sets we show that any set can be viewed as the image of a d c set under an appropriate linear mapping using this universality we can convert any problem of finding an element of a given compact set in n into one of finding an element of a d c set on the basis of this approach a method is developed for solving a system of nonlinear equations inequations unlike newton type methods our method does not require either convexity differentiability assumptions or an initial approximate solution

force identification of dynamic systems using genetic programming one obvious limitation of the traditional force identification techniques is that they are unable to obtain the explicit expression of the force moreover some techniques need both the displacement and velocity data of all freedoms and some need the markov parameters from numerical calculation or experimental test before the force identification can be carried out this paper presents a genetic programming gp based method for excitation force identification of dynamic systems to overcome these traditional methods disadvantages gp is employed as a search and optimization method to obtain the optimal if not the best force expression from the known dynamic response one obvious merit of the proposed method is that it can obtain the explicit expression of the unknown force another advantage is that it only needs the dynamic response data at one point i e displacement or velocity or acceleration of one freedom illustrative examples demonstrate that the gp based method is able to identify the excitation force of a single degree a three degree dynamic systems and a frame structure depicting its potential for force forecast problems

nonlinear dynamic analysis of an eccentrically prestressed damped beam under a concentrated moving harmonic load this paper focuses on the geometrically nonlinear dynamic analysis of an eccentrically prestressed simply supported damped beam subjected to a concentrated moving harmonic load the nonlinear dynamic deflections of the beam are obtained by polynomial functions the kelvin voigt model for the material of the beam is used two coupled nonlinear systems of equations of motion are derived using lagrange s equations under the assumptions of the euler bernoulli beam theory with the von karman s nonlinear strain displacement relationships the rotary inertia axial displacement and axial inertia are included in the formulation the nonlinear equations of motion are solved by using the implicit time integration method of newmark in conjunction with the newton raphson iteration method in this study the effects of large deflections the internal damping of the beam the velocity of the moving harmonic load the prestress load the eccentricity of the prestress load and the excitation frequency on the dynamic response of the beam are discussed the obtained results are compared with the results based on the linear beam theory convergence studies are performed numerical results show that the above mentioned effects play a very important role in the deflections of the beam

vibration of multi span non uniform beams under moving loads by using modified beam vibration functions based on hamilton s principle the vibration of a multi span non uniform beam subjected to a moving load is analysed by using modified beam vibration functions as the assumed modes the modified beam vibration functions satisfy the zero deflection conditions at all the intermediate point supports as well as the boundary conditions at the two ends of the beam numerical results are presented for both uniform and non uniform beams under moving loads of various velocities examples show that this method converges very quickly and good results are obtained

concave minimization via conical partitions and polyhedral outer approximation an algorithm is proposed for globally minimizing a concave function over a compact convex set this algorithm combines typical branch and bound elements like partitioning bounding and deletion with suitably introduced cuts in such a way that the computationally most expensive subroutines of previous methods are avoided in each step essentially only few linear programming problems have to be solved some preliminary computational results are reported

convergence and restart in branch and bound algorithms for global optimization application to concave minimization and d c optimization problems a general branch and bound conceptual scheme for global optimization is presented that includes along with previous branch and bound approaches also grid search techniques the corresponding convergence theory as well as the question of restart capability for branch and bound algorithms used in decomposition or outer approximation schemes are discussed as an illustration of this conceptual scheme a finite branch and bound algorithm for concave minimization is described and a convergent branch and bound algorithm based on the previous one is developed for the minimization of a difference of two convex functions

a global solution to sparse correspondence problems we propose a new methodology for reliably solving the correspondence problem between sparse sets of points of two or more images this is a key step inmost problems of computer vision and so far no general method exists to solve it our methodology is able to handle most of the commonly used assumptions in a unique formulation independent of the domain of application and type of features it performs correspondence and outlier rejection in a single step and achieves global optimality with feasible computation feature selection and correspondence are first formulated as an integer optimization problem this is a blunt formulation which considers the whole combinatorial space of possible point selections and correspondences to find its global optimal solution we build a concave objective function and relax the search domain into its convex hull the special structure of this extended problem assures its equivalence to the original one but it can be optimally solved by efficient algorithms that avoid combinatorial search this methodology can use any criterion provided it can be translated into cost functions with continuous second derivatives

an efficient algorithm for dynamic analysis of bridges under moving vehicles using a coupled modal and physical components approach abstract a general and efficient method is proposed for the resolution of the dynamic interaction problem between a bridge discretized by a three dimensional finite element model and a dynamic system of vehicles running at a prescribed speed the resolution is easily performed with a step by step solution technique using the central difference scheme to solve the coupled equation system this leads to a modified mass matrix called a pseudo static matrix for which its inverse is known at each time step without any numerical effort the method uses a modal superposition technique for the bridge components the coupled system vectors contain both physical and modal components the physical components are the degrees of freedom of a vehicle modelled as linear discrete mass spring damper systems the modal components are the degree of freedom of a linear finite element model of the bridge in this context the resolution of the eigenvalue problem for the bridge is indispensable the elimination of the interaction forces between the two systems bridge and vehicles gives a unique coupled system supersystem containing the modal and physical components in this study we duly consider the bridge pavement as a random irregularity surface the comparison between this study and the uncoupled iterative method is performed

reconstruction of distributed dynamic loads on an euler beam via mode selection and consistent spatial expression this paper presents a convenient and efficient approach to reconstruct two dimensional distributed dynamic loads on a damped thin elastic plate from its steady state dynamic response the approach is based on a mode selection method which comes from an idea that an optimal range of frequency and mode exists for dynamic load reconstruction as well as on the consistent spatial expression of the distributed dynamic loads the criterion for mode selection is derived theoretically a comparison between the method of truncated singular value decomposition tsvd and the method of mode selection demonstrates that the former is unstable while the latter is not only stable but robust with the proposed criterion the method of mode selection enables one to find an optimal range for load reconstruction provided that the error bounds of both parameters and objective are given or estimated and hence to make a balance between the reconstruction range and the error control

crack identification in beam from dynamic responses a time domain method is proposed in which the parameters of a crack in a structural member are identified from strain or displacement measurements the crack is modeled as a discrete open crack represented mathematically by the dirac delta function the dynamic responses are calculated basing on modal superposition in the inverse analysis optimization technique coupled with regularization on the solution is used to identify the crack s the formulation for identification is further extended to the case of multiple cracks a general orthogonal polynomial function is used to generate the derivatives of the strain or displacement time responses to eliminate the error due to measurement noise computation simulations with sinusoidal and impulsive excitations on a beam with a single crack or multiple cracks show that the method is effective for identifying the crack parameters with accuracy the proposed identification algorithm was also verified experimentally from impact hammer tests on a beam with a single crack

signal codes convolutional lattice codes the coded modulation scheme proposed in this paper has a simple construction an integer sequence representing the information is convolved with a fixed continuous valued finite impulse response fir filter to generate the codeword a lattice point due to power constraints the code construction includes a shaping mechanism inspired by precoding techniques such as the tomlinson harashima filter we naturally term these codes convolutional lattice codes or alternatively signal codes due to the signal processing interpretation of the code construction surprisingly properly chosen short fir filters can generate good codes with large minimal distance decoding can be done efficiently by sequential decoding or for better performance by bidirectional sequential decoding error analysis and simulation results indicate that for the additive white gaussian noise awgn channel convolutional lattice codes with computationally reasonable decoders can achieve low error rate close to the channel capacity

estimation of modal loads using structural response in this study an analytical procedure is developed based on the kalman filtering approach to estimate modal loads applied on a structure using limited measured response of the structure the effect of various variables such as the type of response the noise level and the level of uncertainty in dynamic properties of the structure on the modal load estimation is evaluated in the frequency domain through numerical analysis for a single degree of freedom sdof and a multi degree of freedom mdof system it is observed that the acceleration response is relatively more stable and robust in external load estimation than other response components the noise is amplified at the high frequency range for the displacement or velocity response whereas in the case of acceleration response the noise is not amplified in the estimated external load it is also found that the discrepancy between dynamic characteristics derived for an analytical model and the actual structure causes the transfer function from the actual load to the estimated load to distort near and below the structural natural frequency the estimation of external loads is extended to a mdof system the results show that the modal loads can be estimated accurately from limited measurements of acceleration response on the basis of the assumption that the measured response can be transformed to the modal response by a proper orthogonal decomposition and the corresponding modal properties used for the transformation can be obtained by a system identification technique

on the finite length scaling of q ary polar codes the polarization process of polar codes over a prime q ary alphabet is studied recently it has been shown that the blocklength of polar codes with prime alphabet size scales polynomially with respect to the inverse of the gap between code rate and channel capacity however except for the binary case the degree of the polynomial in the bound is extremely large in this paper a different approach to computing the degree of this polynomial for any prime alphabet size is shown this approach yields a lower degree polynomial for various values of the alphabet size that were examined it is also shown that even lower degree polynomial can be computed with an additional numerical effort

studies on dynamic behavior of functionally graded cylindrical shells with pzt layers under moving loads based on the first order shear deformation theory fsdt the hamilton s principle and the maxwell equation this paper presents the coupling equations to govern the electric potential and the displacements of the functionally graded cylindrical shell with surface bonded pzt piezoelectric layer and subjected to moving loads the frequencies equations are obtained by using displacement functions and one electric potential function the modal analysis technique and newmark s integration method are used to calculate the displacements and sensory electric potential of the shell subjected to moving loads the effects of the moving velocities of the loads volume fraction exponents of functionally graded materials fgms and temperature environment on the dynamic responses of shells are investigated an analytical approximate equation is obtained to describe the relationship between critical velocities of moving loads and natural frequencies of shells the present approach is validated by comparing the natural frequencies with the result presented by ng et al in addition numerical results show the relationship between the displacements and sensory electric potential of the shell the present work shows that some meaningful and interesting results presented in this paper are helpful for the application and the design of smart sensory structures

breadth first maximum likelihood sequence detection geometry sa b c is an algorithm penetrating a tree or trellis breadth first it performs maximum likelihood sequence detection mlsd under that structural constraint and also under the complexity constraints determined by the parameters b and c first c is the number of partitions into which the states are distributed and b denotes the number of paths in each partition recursively selecting paths which are closest to the received signal in the euclidean distance hamming distance sense guarantees constrained mlsd for the additive white gaussian binary symmetric channel the previously presented vector euclidean distance ved is an important tool for analyzing sa b c over the additive white gaussian noise awgn channel a geometric interpretation of the signals involved clarifies the basic properties of this ved and other relevant general results invariance monotonicity these results also form a basis for the construction of an algorithm for the efficient and fast calculation of minimum veds of interest for large signal to noise ratio snr detection performance this in turn reveals the necessary complexity requirements to meet specified performance requirements for concrete trellis coded systems here the simple example of convolutionally coded rate 1 2 with gray coded quaternary phase shift keying over the awgn channel is considered when c 1 and choosing b spl sim spl radic s s being the number of states in the code trellis gives the same asymptotic detection performance large snr as unconstrained mlsd e g implemented using the viterbi algorithm

a parallel algorithm for constrained concave quadratic global minimization the global minimization of large scale concave quadratic problems over a bounded polyhedral set using a parallel branch and bound approach is considered the objective function consists of both a concave part nonlinear variables and a strictly linear part which are coupled by the linear constraints these large scale problems are characterized by having the number of linear variables much greater than the number of nonlinear variables a linear underestimating function to the concave part of the objective is easily constructed and minimized over the feasible domain to get both upper and lower bounds on the global minimum function value at each minor iteration of the algorithm the feasible domain is divided into subregions and linear underestimating problems over each subregion are solved in parallel branch and bound techniques can then be used to eliminate parts of the feasible domain from consideration and improve the upper and lower bounds it is shown that the algorithm guarantees that a solution is obtained to within any specified tolerance in a finite number of steps computational results are presented for problems with 25 and 50 nonlinear variables and up to 400 linear variables these results were obtained on a four processor cray2 using both sequential and parallel implementations of the algorithm the average parallel solution time was approximately 15 seconds for problems with 400 linear variables and a relative tolerance of 0 001 for a relative tolerance of 0 1 the average computation time appears to increase only linearly with the number of linear variables

dynamic response of a beam with intermediate point constraints subject to a moving load abstract the transverse vibration of a beam with intermediate point constraints subject to a moving load is analyzed by using the euler beam theory and the assumed mode method the point constraints in the form of supports are assumed to be linear springs of large stiffness results of numerical simulations are presented for various combinations of constant axial velocity of the moving load and number of point constraints

generalized app detection of continuous phase modulation over unknown isi channels techniques for computing soft information in the presence of unknown intersymbol interference are presented with a particular focus on iterative detection of serially concatenated continuous phase modulation the techniques are centered around the recursive least squares algorithm thus enabling unsupervised detection in particular we employ bidirectional estimation

solution of the multisource weber and conditional weberproblems by d c programming d c programming is a recent technique of global optimization that allows the solution of problems whose objective function and constraints can be expressed as differences of convex i e d c functions many such problems arise in continuous location theory the problem first considered is to locate a known number of source facilities to minimize the sum of weighted euclidean distances between a user s fixed location and the source facility closest to the location of each user we also apply d c programming to the solution of the conditional weber problem an extension of the multisource weber problem in which some facilities are assumed to be already established in addition we consider a generalization of weber s problem the facility location problem with limited distances where the effective service distance becomes a constant when the actual distance attains a given value computational results are reported for problems with up to 10 000 users and two new facilities 50 users and three new facilities 1 000 users 20 existing facilities and one new facility or 200 users 10 existing and two new facilities

global minimization of a linearly constrained concave function by partition of feasible domain the problem of minimizing a concave function subject to linear inequality constraints may have many local solutions therefore finding the global constrained minimum is a computationally difficult problem a computational method is described which finds the global minimum of a smooth concave function over a polyhedron in rn the feasible domain is partitioned into a rectangular domain which can be excluded from further consideration and r 2n subdomains at least one of which contains the global minimum a known algorithm can be applied sequentially or in parallel to each of these r subdomains to compute the global minimum a method is also presented appendix b for the construction of nontrivial test problems for which the global minimum point is known given an arbitrary polyhedron and a selected vertex it is shown how to determine a concave quadratic function generally with many local minima with its global minimum at the selected vertex

a novel approach for distributed dynamic load reconstruction by space time domain decoupling abstract a novel inverse approach based on green s function method and orthogonal polynomial fitting technique is presented in this paper to reconstruct the distributed dynamic load acting on a structure this approach enables one to identify the time history and reconstruct the spatial distribution function separately it is first assumed in this paper that the distribution function and the time history of the distributed dynamic load are separable modal analysis proves the sameness of the form between the modal loads and the actual time history with the knowledge of corresponding green s functions and modal responses the modal loads are identified later approximating the spatial distribution function by a set of chebyshev orthogonal polynomials new distributed dynamic loads are constructed with each orthogonal polynomial performing as the spatial distribution function and the previously identified modal load acting as the time history fitting the modal loads the coefficients of each orthogonal polynomial are achieved and then the spatial distribution function recovered to overcome the intrinsic ill conditioned characteristic appropriate regularization methods are adopted in both the modal load identification and the distribution function reconstruction numerical examples demonstrate the validity and accuracy of the proposed method

analysis of discrete ill posed problems by means of the l curve when discrete ill posed problems are analyzed and solved by various numerical regularization techniques a very convenient way to display information about the regularized solution is to plot the norm or seminorm of the solution versus the norm of the residual vector in particular the graph associated with tikhonov regularization plays a central role the main purpose of this paper is to advocate the use of this graph in the numerical treatment of discrete ill posed problems the graph is characterized quantitatively and several important relations between regularized solutions and the graph are derived it is also demonstrated that several methods for choosing the regularization parameter are related to locating a characteristic l shaped corner of the graph

vibrations of non uniform continuous beams under moving loads abstract the dynamic behavior of multi span non uniform beams transversed by a moving load at a constant and variable velocity is investigated the continuous beam is modelled using bernoulli euler beam theory the solution is obtained by using both the modal analysis method and the direct integration method the natural frequencies and mode shapes used in the solution of this problem are obtained exactly by deriving the exact dynamic stiffness matrices for any polynomial variation of the cross section along the beam using the exact element method the mode shapes are expressed as infinite polynomial series using the exact mode shapes yields the exact solution for general variation of the beam section in case of constant and variable velocity numerical examples are presented in order to demonstrate the accuracy and the effectiveness of the present study and the results are compared to previously published results

difference of convex solution of quadratically constrained optimization problems abstract recently global optimization algorithms have been proposed for solving nonconvex programs whose objective and constraint functions are expressed as the difference of two convex functions a surprisingly large class of functions can be decomposed in this way so these algorithms can be viewed as general procedures for global optimization often a given problem can have more than one difference of convex d c formulation this paper investigates the impact of alternative d c formulations of a nonconvex program in particular we investigate the computational performance of two d c programming algorithms when applied to two d c formulations of quadratically constrained quadratic optimization models computational results suggest that the performance of d c techniques can be significantly influenced by the nature of the d c decomposition

time domain responses of a prestressed beam and prestress identification abstract the time domain response of a prestressed euler bernoulli beam under external excitation is studied based on modal superposition the prestress force is then identified in the time domain by a system identification approach and tikhonov regularization technique is used to provide bounds to the ill conditioned results in the identified problem both measured displacements and strains are used the noise effect is improved using the orthogonal polynomial function and cases with either sinusoidal or impulsive excitations are illustrated to give very good results from the lower three measured modes and data obtained from three measurement points work in this paper demonstrates the feasibility of indirectly identifying the prestress force in a beam

on the solution of concave knapsack problems we consider a version of the knapsack problem which gives rise to a separable concave minimization problem subject to bounds on the variables and one equality constraint we characterize strict local miniimizers of concave minimization problems subject to linear constraints and use this characterization to show that although the problem of determining a global minimizer of the concave knapsack problem is np hard it is possible to determine a local minimizer of this problem with at most o n logn operations and 1 logn evaluations of the function if the function is quadratic this algorithm requires at most o n logn operations

quasiconjugates of functions duality relationship between quasiconvex minimization under a reverse convex constraint and quasiconvex maximization under a convex constraint and applications abstract in this paper we introduce a concept of quasiconjugate for functions defined on rn whose values are in r the conjugacy correspondence between functions and their quasiconjugates is one to one and symmetric in a class of quasiconvex functions whose minimizer on rn is located at the origin by using the concept of quasiconjugate we obtain a duality relationship between quasiconvex minimization under a reverse convex constraint and quasiconvex maximization under a convex constraint this duality relationship allows us to establish a primal dual pair in a class of nonconvex optimization problems without the duality gap several applications are given

a decomposition method using a pricing mechanism for min concave cost flow problems with a hierarchical structure in this paper we develop a decomposition method using a pricing mechanism which has been widely applied to linear and convex programs for a class of nonconvex optimization problems that are min concave cost flow problems under directed uncapacitated networks with a hierarchical structure

global minimum test problem construction a method is presented for the construction of test problems for which the global minimum point is known given a bounded convex polyhedron inr n and a selected vertex a concave quadratic function is constructed which attains its global minimum at the selected vertex in general this function will also have many other local minima

limited search trellis decoding of convolutional codes the least storage and node computation required by a breadth first tree or trellis decoder that corrects t errors over the binary symmetric channels is calculated breadth first decoders work with code paths of the same length without backtracking the viterbi algorithm is an exhaustive trellis decoder of this type other schemes look at a subset of the tree or trellis paths for random tree codes theorems about the asymptotic number of paths required and their depth are proved for concrete convolutional codes the worst case storage for t error sequences is measured in both cases the optimal decoder storage has the same simple dependence on t the m algorithm and algorithms proposed by g j foschini ibid vol it 23 p 605 9 sept 1977 and by s j simmons phd diss queens univ kingston ont canada are optimal or nearly so they are all far more efficient than the viterbi algorithm

the complexity of vertex enumeration methods the computational complexity of problems relating to the enumeration of all the vertices of a convex polyhedron defined by linear inequalities is examined several published approaches are evaluated in this light a new algorithm is described and shown to have a better complexity estimate than existing methods empirical evidence supporting the theoretical superiority is presented finally vertex enumeration is discussed when the space containing the polyhedra is of fixed dimension and only the size of the inequality system is permitted to vary

jointly constrained biconvex programming this paper presents a branch and bound algorithm for minimizing the sum of a convex function in x a convex function in y and a bilinear term in x and y over a closed set such an objective function is called biconvex with biconcave functions similarly defined the feasible region of this model permits joint constraints in x and y to be expressed the bilinear programming problem becomes a special case of the problem addressed in this paper we prove that the minimum of a biconcave function over a nonempty compact set occurs at a boundary point of the set and not necessarily an extreme point the algorithm is proven to converge to a global solution of the nonconvex program we discuss extensions of the general model and computational experience in solving jointly constrained bilinear programs for which the algorithm has been implemented

vibration of multi span timoshenko beams to a moving force abstract a method of modal analysis is proposed in this paper to investigate the forced vibration of multi span timoshenko beams the ratio of the radius of gyration of the cross section to one span length is defined as a parameterr the effect ofron the first modal frequency of a beam is studied a concentrated force traversing on the beam is used as an example the effects of span number rotary inertia and shear deformation on the maximum moment the maximum deflection and the critical velocity of a beam are examined the results are compared with those of a multi span bernoulli euler beam

methods for global concave minimization a bibliographic survey the global concave minimization problem is to find the constrained global minimum of a concave function since such a function may have many local minima finding the global minimum is a computationally difficult problem in this bibliographic survey which includes most of the recent papers on constrained global concave minimization we have attempted to briefly summarize the main ideas in each paper these recent papers include those concerned with large scale global concave minimization and bilinear programming

an implicit enumeration method for global optimization problems abstract this paper presents a new method for the global minimization of a function subject to linear constraints the feasible set is first covered by a union of simpler sets then some of them are eliminated using some global analytic information about the objective function e g lipschitz constants properties of the derivatives etc the remaining part of the cover is then refined and the process is repeated estimates for the computational complexity are given for some classes of problems numerical experience is also reported

list decoding of turbo codes list decoding of turbo codes is analyzed under the assumption of a maximum likelihood ml list decoder it is shown that large asymptotic gains can be achieved on both the additive white gaussian noise awgn and fully interleaved flat rayleigh fading channels it is also shown that the relative asymptotic gains for turbo codes are larger than those for convolutional codes finally a practical list decoding algorithm based on the list output viterbi algorithm lova is proposed as an approximation to the ml list decoder simulation results show that the proposed algorithm provides significant gains corroborating the analytical results the asymptotic gain manifests itself as a reduction in the bit error rate ber and frame error rate fer floor of turbo codes

vibration frequencies of a rotating flexible arm carrying a moving mass abstract a clamped free flexible beam rotating in a horizontal plane and carrying a moving mass is modelled by the euler bernoulli beam theory the equation of motion is derived by hamilton s principle including the effects of centrifugal stiffening arising from the rotation of the beam the motion of the moving mass and the beam is coupled the equation of motion is a coupled non linear partial differential equation where the coupling terms have to be evaluated at the position of the moving mass in order to obtain the mode shapes which account for the motion of the moving mass the solution is discretized into space and time functions and the beam is divided into two separate regions with respect to the moving mass this results in two non homogeneous linear mode shape ordinary differential equations with four boundary one discontinuity and three continuity conditions the power series method is used to solve for the mode shape differential equations a frequency equation is derived giving the relationship between the non dimensional modal frequencies and the four non dimensional parameters i e the moving mass position the moving mass the beam angular velocity and the total moment of inertia about the hub the numerical bisection method is used to solve for the vibration frequencies under different parameters results are presented for the first three modes of vibration

set variational inequalities in this paper we formulate variational inequality problems defined by point to set mappings svi constructive and nonconstructive proofs for the existence of the solutions of the svi are discussed moreover we show how the well known circumscribed ellipsoid method can be used to find approximate solutions to the svi defined by monotone mappings thereby we would like to mention that at each iteration we do not need to find subgradients to construct planes which do not cut off the solution we study also the connection between the svi and saddle point problems finally a method for solving nonmonotone variational inequality problems will be considered

joint power and admission control non convex l_ q approximation and an effective polynomial time deflation approach in an interference limited network joint power and admission control jpac aims at supporting a maximum number of links at their specified signal to interference plus noise ratio sinr targets while using minimum total transmission power various convex approximation deflation approaches have been developed for the jpac problem in this paper we propose an effective polynomial time non convex approximation deflation approach for solving the problem the approach is based on the non convex ell q 0 approximation of an equivalent sparse ell 0 reformulation of the jpac problem we show that for any instance of the jpac problem there exists a bar q in 0 1 such that it can be exactly solved by solving its ell q approximation problem with any q in 0 bar q we also show that finding the global solution of the ell q approximation problem is np hard then we propose a potential reduction interior point algorithm which can return an epsilon kkt solution of the np hard ell q approximation problem in polynomial time the returned solution can be used to check the simultaneous supportability of all links in the network and to guide an iterative link removal procedure resulting in the polynomial time non convex approximation deflation approach for the jpac problem numerical simulations show that the proposed approach outperforms the existing convex approximation approaches in terms of the number of supported links and the total transmission power particularly exhibiting a quite good performance in selecting which subset of links to support

a soft output mimo detector with achievable information rate based partial marginalization in this paper we propose a soft output detector for multiple input multiple output mimo channels that utilizes achievable information rate air based partial marginalization pm the proposed air based pm air pm detector has superior performance compared to previously proposed pm designs and other soft output detectors such as k best while at the same time yielding lower computational complexity a detection latency that is independent of the number of transmit layers and straightforward inclusion of soft input information using a tree representation of the mimo signal the key property of the airpm is that the connections among all child layers are broken therefore least square ls estimates used for marginalization are obtained independently and in parallel which have better quality than the zero forcing decision feedback zf df estimates used in previous pm designs such a property of the airpm detector is designed via a mismatched detection model that maximizes the air furthermore we show that the chain rule holds for the air calculation which facilitates an information theoretic characterization of the air pm detector less

groundwater management using numerical simulation and the outer approximation method for global optimization groundwater quantity management problems with fixed charges have been formulated in the past as mixed integer and linear programming problems in this paper a new methodology is presented where the fixed charges are incorporated into the objective function in an exponential form and the problem is solved as a concave minimization problem the principal difficulty in the minimization of a concave function over a linear or nonlinear set of constraints is that the local minima which are determined by the classical minimization algorithms may not be global in an effort to circumvent this problem the outer approximation method is introduced this method is applicable to the global minimization of a concave function over a compact set of constraints in the present work the outer approximation is applied to concave minimization problems over a convex compact set of constraints two applications of the method to groundwater management problems are presented herein and the results are compared with an existing solution obtained using a different optimization approach

comment on improved analysis of list decoding and its application to convolutional codes and turbo codes in a recent paper bai ieee trans inf theory 2007 an improved analysis concerning the analysis of list decoding was presented the event that the correct codeword is excluded from the list is central for the additive white gaussian noise awgn channel an important quantity is the in bai ieee trans inf theory 2007 called effective euclidean distance this was earlier considered in aulin ieee trans commun 1999 under the name vector euclidean distance ved where also a simple mathematical expression for this quantity was easily derived for any list size in bai ieee trans inf theory 2007 a geometrical analysis gives this when the list size is 1 2 or 3

maximizing a concave function over the efficient or weakly efficient set an important approach in multiple criteria linear programming is the optimization of some function over the efficient or weakly efficient set this is a very difficult nonconvex optimization problem even for the case that the function to be optimized is linear in this article we consider the problem of maximizing a concave function over the efficient or weakly efficient set we show that this problem can essentially be formulated as a special global optimization problem in the space of the extreme criteria of the underlying multiple criteria linear program an algorithm of branch and bound type is proposed for solving the resulting problem

low complexity decoders for constant envelope digital modulations digital angle modulations having input symbol memory can be demodulated using maximum likelihood sequence estimation mlse or viterbi decoding the demodulation of the more bandwidth efficient of these can require a large number of computations in this paper lower complexity decoding approaches are presented these decoders use a predetermined processing order and a reduced number of survivor signals s at every time nt processing is performed on the signal sequences using metrics likelihoods obtained by a matched filter bank similar to that needed for mlse the decoders can achieve asymptotic optimality of error rate while being computationally faster and simpler than mlse for many modulations in addition error rate performance can be traded for complexity reduction expected performance has been verified for representative modulations

on reduced complexity equalization based on ungerboeck and forney observation models this correspondence investigates the asymptotic behavior of reduced state intersymbol interference isi equalizers based on the ungerboeck and forney observation models it is shown that ungerboeck based equalizers can suffer from correct path loss cpl even in the noiseless regime isi conditions that lead to cpl are analytically derived and illustrated by examples

explicit form of an implicit method for inverse force identification abstract most existing time domain force identification methods are based on the state space method which has the disadvantage of large discretization error with a low sampling frequency or a long sampling duration this work transforms the conventional implicit newmark algorithm into an explicit form for the solution of the ax b equations which is an equivalent transformation and it exhibits the same characteristics of newmark algorithm as an implicit method the accuracy of this method for the dynamic force identification is illustrated with two shear frame buildings and a planar truss structure numerical results are compared with reference analytical responses the new method gives more accurate identified force time histories compared with those from the conventional state space method for multiple sinusoidal and white noise excitations with 10 measurement noise in the responses

convergence qualification of adaptive partition algorithms in global optimization following the presentation of a general partition algorithm scheme for seeking the globally best solution in multiextremal optimization problems necessary and sufficient convergence conditions are formulated in terms of respectively implied or postulated properties of the partition operator the convergence results obtained are pertinent to a number of deterministic algorithms in global optimization permitting their diverse modifications and generalizations

proper orthogonal decomposition and its applications part i theory abstract in view of the increasing popularity of the application of proper orthogonal decomposition pod methods in engineering fields and the loose description of connections among the pod methods the purpose of this paper is to give a summary of the pod methods and to show the connections among these methods firstly the derivation and the performance of the three pod methods karhunen loeve decomposition kld principal component analysis pca and singular value decomposition svd are summarized then the equivalence problem is discussed via a theoretical comparison among the three methods the equivalence of the matrices for processing the objective functions the optimal basis vectors the mean square errors and the asymptotic connections of the three methods are demonstrated and proved when the methods are used to handle the pod of discrete random vectors

identification of the structure parameters using short time non stationary stochastic excitation abstract in this paper we propose an approach to the flexural stiffness or eigenvalue frequency identification of a linear structure using a non stationary stochastic excitation process the idea of the proposed approach lies within time domain input output methods the proposed method is based on transforming the dynamical problem into a static one by integrating the input and the output signals the output signal is the structure reaction i e structure displacements due to the short time irregular load of random type the systems with single and multiple degrees of freedom as well as continuous systems are considered

a truncated generalized singular value decomposition algorithm for moving force identification with ill posed problems abstract this paper proposes a new methodology for moving force identification mfi from the responses of bridge deck based on the existing time domain method tdm the mfi problem eventually becomes solving the linear algebraic equation in the form ax b the vector b is usually contaminated by an unknown error e generating from measurement error which often called the vector e as noise with the ill posed problems that exist in the inverse problem the identification force would be sensitive to the noise e the proposed truncated generalized singular value decomposition method tgsvd aims at obtaining an acceptable solution and making the noise to be less sensitive to perturbations with the ill posed problems the illustrated results show that the tgsvd has many advantages such as higher precision better adaptability and noise immunity compared with tdm in addition choosing a proper regularization matrix l and a truncation parameter k are very useful to improve the identification accuracy and to solve ill posed problems when it is used to identify the moving force on bridge

on the duality of a non convex optimization problem and the strong unicity constant in linear chebyshev approximation abstract the main goal of this paper is to define a dual problem for a special non convex global optimization problem and to show that a duality gap may not occur the proof is based on the convergence of a cutting plane algorithm the results can be applied to a dual characterization of the strong unicity constant in linear chebyshev approximation and the algorithm can be used to compute this constant

global minimization of large scale constrained concave quadratic problems by separable programming the global minimization of a large scale linearly constrained concave quadratic problem is considered the concave quadratic part of the objective function is given in terms of the nonlinear variablesx r n while the linear part is in terms ofy r k for large scale problems we may havek much larger thann the original problem is reduced to an equivalent separable problem by solving a multiple cost row linear program with 2n cost rows the solution of one additional linear program gives an incumbent vertex which is a candidate for the global minimum and also gives a bound on the relative error in the function value of this incumbent ana priori bound on this relative error is obtained which is shown to be 0 25 in important cases if the incumbent is not a satisfactory approximation to the global minimum a guaranteede approximate solution is obtained by solving a single liner zero one mixed integer programming problem this integer problem is formulated by a simple piecewise linear underestimation of the separable problem

load updating for nonlinear finite element models a measurement based load updating method for finite element models subjected to static loads was studied using a four noded curved beam element for large displacements rotations and a gradient based variable metric optimizer finite element analysis was used to numerically calculate the geometrically linear and nonlinear responses and their sensitivities under a given load the optimizer was used to recursively update the load so that it minimized the square of the difference between the calculated and prefiltered noise free measured displacement or strain data for the basic studies the extracted load was represented within an element by a linear combination of integrated legendre polynomials the coefficients of which were taken as design variables of the least squares problem through a model order analysis the benefits for solving load updating problems using the relative deformation measurement the polynomials of lower orders the elements of larger sizes because of using the high precision four noded beam element and the denser measured points were studied for linear responses under different types of applied loads it was confirmed that using the reduced number of unknown variables to obtain an overdetermined inverse problem helps get unique and stable extracted loads though this conclusion was verified mainly through illustrative examples for a cantilever beam it was generally applicable to other load updating or inverse problems further examples were given for a three dimensional portal frame load updating extracting highly oscillating loads and a strain based cantilever beam load updating the final examples were load updating for geometrically nonlinear finite element models under self weight snow and or pressure loads

moving forces identification on a multi span continuous bridge abstract a continuous bridge is modelled as a multi span continuous timoshenko beam with non uniform cross section the vibration behaviour of this beam subjected to moving loads is analyzed by hamilton s principle with the intermediate point constraints represented by very stiff linear springs a method based on the modal superposition and optimization technique is developed to identify the moving forces in the time domain the damped least squares method is used in the identification to provide bounds to the results the errors in the moving force identification are discussed in the paper both computation simulations and laboratory tests show that the method is effective for identifying the moving loads using different combinations of measured responses

dynamic force identification based on enhanced least squares and total least squares schemes in the frequency domain identifying dynamic forces from structural responses is necessary when direct measurement of those dynamic forces is impossible using conventional means a common approach to address this problem is to determine the frequency response function frf matrix measure the structural responses and calculate the dynamic forces based on least squares ls scheme this approach has been proven to be effective in reducing the random errors that occur in structural response signals unfortunately the accuracy of this approach is often hindered by the inversion of an ill conditioned frf matrix at frequencies near the structural resonances to overcome this inversion instability two regularization filters namely the truncated singular value decomposition tsvd filter and the tikhonov filter are used in conjunction with the conventional ls scheme at specific frequencies here a criterion for applying these enhanced ls schemes is proposed to aid in determining when the increase in computational effort is better utilized furthermore a new ls form of the morozov s discrepancy principle is formulated to aid in selecting the optimum regularization parameter for these filters at each frequency the accuracy in using conventional ls tsvd based ls and tikhonov filter based ls schemes are compared analytically and numerically in this paper it is found that for small sized frf matrices the tikhonov filter based ls scheme tends to work better than the tsvd filter based ls scheme since these approaches can only deal with the random errors in the measured structural responses a total least squares tls scheme that can also address errors associated with the frf matrix is proposed in this research numerical simulations demonstrate that under certain conditions the tls scheme is more effective in reducing the impact of these errors

an interior point algorithm to solve computationally difficult set covering problems we present an interior point approach to the zero one integer programming feasibility problem based on the minimization of a nonconvex potential function given a polytope defined by a set of linear inequalities this procedure generates a sequence of strict interior points of this polytope such that each consecutive point reduces the value of the potential function an integer solution not necessarily feasible is generated at each iteration by a rounding scheme the direction used to determine the new iterate is computed by solving a nonconvex quadratic program on an ellipsoid we illustrate the approach by considering a class of difficult set covering problems that arise from computing the 1 width of the incidence matrix of steiner triple systems

study on different beam models in moving force identification abstract several methods have been developed recently to identify moving forces on a beam the results from all of them exhibit fluctuations at the beginning and end of the time history and they are natural outcomes of the ill conditioned inverse problem accuracy of the identified forces also depends on the parameters of the beam force system which have not been systematically studied this paper employs tikhonov regularization technique to provide bounds to the ill conditioned results in the identification problem the calculation of the optimal regularization parameter is discussed the improved algorithm is then used to study the effect of different parameters on the identification results through single force and multi forces identification both the timoshenko beam theory and the euler bernoulli beam theory are included in the study for a comparison laboratory results on two moving forces identification are also presented for illustration timoshenko beam model is found better than the euler bernoulli beam model in the identification and the limits of applications of the moving force identification method are also reported

breadth first maximum likelihood sequence detection basics the problem of performing breadth first maximum likelihood sequence detection mlsd under given structural and complexity constraints is solved and results in a family of optimal detectors given a trellis with s states these are partitioned into c classes where b paths into each class are selected recursively in each symbol interval the derived result is to retain only those paths which are closest to the received signal in the euclidean hamming distance sense each member in the sa b c family of sequence detectors sa denotes search algorithm performs complexity constrained mlsd for the additive white gaussian noise awgn bsc channel the unconstrained solution is the viterbi algorithm va analysis tools are developed for each member of the sa b c class and the asymptotic snr probability of losing the correct path is associated with a new euclidean distance measure for the awgn case the vector euclidean distance ved the traditional euclidean distance is a scalar special case of this termed the scalar euclidean distance sed the generality of this ved is pointed out some general complexity reductions exemplify those associated with the va approach

a conical algorithm for globally minimizing a concave function over a closed convex set in this paper we are concerned with the problem of finding the global minimum of a concave function over a closed convex possibly unbounded set in rn the intrinsic difficulty of this problem is due to the fact that a local minimum of the objective function may fail to be a global one which makes the conventional methods of local optimization almost useless

penalty for zero one integer equivalent problem the equivalence of zero one integer programming and a concave quadratic penalty function problem has been shown by raghavachari for a sufficiently large value of the penalty a lower bound for this penalty is obtained here which in specific cases cannot be reduced

load updating for finite element models a method for reducing the differences between experimental testing or real world events and their finite element counterparts is presented in this method system identification or finite element model updating are not performed instead the loads on the finite element model that would create equivaient displacements or strains are identified by various means thus saving a large amount of computational effort this method of finding an applied load is also extremely useful in the analysis of testing data for vehicles and other structures using methods based on classical least squares methods we present the basis for finite element load updating and sample application through the use of a computer program for a beam under static loads we examine the conditioning number of the resulting system of equations and provide a least squares solution that is more robust through the use of singular value decomposition this allows an easier analysis of structural models for example of a prototype vehicle by determining the loads that the prototype is subjected to in testing these loads can then be used on other models of that vehicle during the design process to decrease the time spent in testing while increasing design s reliability by reducing uncertainties in the applied load

reduced state sequence estimation with set partitioning and decision feedback a reduced state sequence estimator for linear intersymbol interference channels is described the estimator uses a conventional viterbi algorithm with decision feedback to search a reduced state subset trellis that is constructed using set partitioning principles the complexity of maximum likelihood sequence estimation mlse due to the length of the channel memory and the size of the signal set is systematically reduced an error probability analysis shows that a good performance complexity tradeoff can be obtained in particular the results indicate that the required complexity to achieve the performance of mlse is independent of the size of the signal set for large enough signal sets simulation results are provided for two partial response systems a simple technique for quadrature partial response signaling qprs is described that eliminates the quasicatastrophic nature of the ml trellis

an inverse method for the estimation of input forces acting on non linear structural systems this study proposes an inverse method to identify input forces of non linear structural systems the method is an extension of the previous work that is limited to linear structural systems the present estimation method is composed of the extended kalman filter and a recursive least squares estimator by using the inverse method input forces acting on non linear structural systems can be estimated from measured dynamic responses in this work numerical simulations of input forces estimation of non linear lumped mass systems are performed to verify the practicality and accuracy of the proposed algorithm the simulation results demonstrate that the application of the input force estimation method to non linear structural systems is successful

moving force identification optimal state estimation approach existing techniques to identify moving forces exhibit the common weakness of having large fluctuations in the identified results a new method of moving force identification is developed in this paper making use of the dynamic programming technique to overcome this weakness the forces in the state space formulation of the dynamic system are identified in the time domain using a recursive formula based on several distributed sensor measurements and responses of the structure are reconstructed using the identified forces for comparison like all inverse problems the computation is ill conditioned however the dynamic programming technique inherently provides bounds to the ill conditioned forces and results from the simulation studies and laboratory work show great improvements over existing methods in the accuracy of identification

a branch and bound outer approximation algorithm for concave minimization over a convex set abstract this article presents a new algorithm for solving the problem of globally minimizing a concave function over a compact convex set the algorithm uses both branch and bound and outer approximation one of the major advantages of the algorithm is that the only significant nonlinear computation required can be accomplished using univariate search procedures after establishing the convergence of the algorithm we discuss this and other computational considerations a small example is solved to illustrate the algorithm because of its advantages the algorithm offers significant promise for efficiently minimizing a concave function over a compact convex set