algorithms for approximate graph matching abstract labeled graphs are graphs in which each node and edge has a label the distance between two labeled graphs is considered to be the weighted sum of the costs of edit operations insert delete and relabel the nodes and edges to transform one graph to the other the paper considers two variants of the approximate graph matching problem agm given a pattern graph p and a data graph d 1 1 what is the distance between p and d 2 2 what is the minimum distance between p and d when subgraphs can be freely removed from d we first show that no efficient algorithm can solve either variant of the agm unless p np then we present several heuristic algorithms leading to approximate solutions the heuristics are based on probabilistic hill climbing and maximum flow techniques our experimental results involving the comparison of real and simulated data demonstrate the good performance of the algorithms presented

choice of specific interpolation points in quadrature formula for integrals containing bessel functions a method for calculation of integrals containing bessel functions is suggested which based on linear interpolation applied to the function entering the integral along with the bessel function a specific choice of interpolation points allows excluding the contribution into integral of all interpolation points besides the first one the study of errors leads to determination of bounds of the considered integral

numerical evaluation of spherical bessel transforms via fast fourier transforms the purpose of this article is to describe a new fast fourier transform fft method for calculating spherical bessel transforms the method is based on an expansion representation of the spherical bessel functions in terms of sine and cosine trigonometric functions multiplied by polynomials in inverse powers of the argument of the bessel function 11 the method should be of value in algorithms in which frequent calculations of spherical bessel transforms are required at many values of the transform variables which is frequently the situation in time dependent scattering calculations the method makes use of ffts for which the computing time for each transform scales as nlog n where n is the number of quadrature points rather than the n2 scaling of ordinary numerical quadratures also the explicit evaluation of the spherical bessel functions is not required in the method the method differs from that given in the work of j d talman 2 33 and a e siegmon 4 in the work of talman 2 33 and siegman 4 a change to logarithmic variables is required to recast the integral transform as a convolution integral which is then evaluated by fft procedures however as pointed out by talman this makes the step size ar increase proportionally with r and renders the method unsuitable for functions of an oscillatory nature in particular the oscillatory nature of the function is lost in the increasing mesh intervals in essence the talman siegman method is excellent for bound state wave functions but it is not

identifying nonlinear biomechanical models by multicriteria analysis in this study the methodology developed by srdjevic and cveticanin international journal of industrial ergonomics 34 2004 307 318 for the nonbiased objective parameter identification of the linear biomechanical model exposed to vertical vibrations is extended to the identification of n degree of freedom dof nonlinear biomechanical models the dynamic performance of the n dof nonlinear model is described in terms of response functions in the frequency domain such as the driving point mechanical impedance and seat to head transmissibility function for randomly generated parameters of the model nonlinear equations of motion are solved using the runge kutta method the appropriate data transformation from the time to frequency domain is performed by a discrete fourier transformation squared deviations of the response functions from the target values are used as the model performance evaluation criteria thus shifting the problem into the multicriteria framework the objective weights of criteria are obtained by applying the shannon entropy concept the suggested methodology is programmed in pascal and tested on a 4 dof nonlinear lumped parameter biomechanical model the identification process over the 2000 generated sets of parameters lasts less than 20 s the model response obtained with the imbedded identified parameters correlates well with the target values therefore justifying the use of the underlying concept and the mathematical instruments and numerical tools applied it should be noted that the identified nonlinear model has an improved accuracy of the biomechanical response compared to the accuracy of a linear model

an effective algorithm for string correction using generalized edit distances i description of the algorithm and its optimality abstract this paper deals with the problem of estimating a transmitted string xs from the corresponding received string y which is a noisy version of xs we assume that y contains any number of substitution insertion and deletion errors and that no two consecutive symbols of xs were deleted in transmission we have shown that for channels which cause independent errors and whose error probabilities exceed those of noisy strings studied in the literature 12 at least 99 5 of the erroneous strings will not contain two consecutive deletion errors the best estimate x of xs is defined as that element of h which minimizes the generalized levenshtein distance d x y between x and y using dynamic programming principles an algorithm is presented which yields x without computing individually the distances between every word of h and y though this algorithm requires more memory it can be shown that it is in general computationally less complex than all other existing algorithms which perform the same task

an algorithm for the numerical evaluation of the hankel and abel transforms a procedure for the efficient numerical evaluation of the hankel and abel transforms is proposed the abel transform is reduced to a convolution which is evaluated in part analytically and in part with an fft the hankel transform is obtained by following the abel transform with an fft

numerical integration of related hankel transforms by quadrature and continued fraction expansion an algorithm is presented for the accurate evaluation of hankel or bessel transforms of algebraically related kernel functions defined here as the non bessel function portion of the integrand that is more widely applicable than the standard digital filter methods without enormous increases in computational burden the algorithm performs the automatic integration of the product of the kernel and bessel functions between the asymptotic zero crossings of the latter and sums the series of partial integrations using a continued fraction expansion equivalent to an analytic continuation of the series the integrands may be saved to allow the rapid computation of related transforms without recalculating the kernel or bessel functions and the integration steps use interlacing quadrature formulas so that no function evaluations are wasted when it is necessary to increase the order of the quadrature rule the continued fraction algorithm allows very slowly divergent or even formally divergent integrals to be computed quite easily the local error is controlled at each step in the algorithm and accuracy is limited largely by machine resolution the algorithm is written in fortran and is listed in an appendix along with a driver program that illustrates its features the driver program and subroutine are available from the seg business offtce

evaluating infinite integrals involving bessel functions of arbitrary order abstract the evaluation of intergrals of the form i n 0 x j n x d x is considered in the past the method of dividing an oscillatory integral at its zeros forming a sequence of partial sums and using extrapolation to accelerate convergence has been found to be the most efficient technique available where the oscillation is due to a trigonometric function or a bessel function of order n 0 1 here we compare various extrapolation techniques as well as choices of endpoints in dividing the integral and establish the most efficient method for evaluating infinite integrals involving bessel functions of any order n not just zero or one we also outline a simple but very effective technique for calculating bessel function zeros

a formal theory for optimal and information theoretic syntactic pattern recognition abstract in this paper we present a foundational basis for optimal and information theoretic syntactic pattern recognition we do this by developing a rigorous model m for channels which permit arbitrarily distributed substitution deletion and insertion syntactic errors more explicitly if a is any finite alphabet and a the set of words over a we specify a stochastically consistent scheme by which a string u a can be transformed into any y a by means of arbitrarily distributed substitution deletion and insertion operations the scheme is shown to be functionally complete and stochastically consistent apart from the synthesis aspects we also deal with the analysis of such a model and derive a technique by which pr y u the probability of receiving y given that u was transmitted can be computed in cubic time using dynamic programming one of the salient features of this scheme is that it demonstrates how dynamic programming can be applied to evaluate quantities involving complex combinatorial expressions and which also maintain rigid probability consistency constraints experimental results which involve dictionaries with strings of lengths between 7 and 14 with an overall average noise of 39 75 demonstrate the superiority of our system over existing methods apart from its straightforward applications in string generation and recognition we believe that the model also has extensive potential applications in speech uni dimensional signal processing and computational molecular biology

mathematical models for the apparent masses of standing subjects exposed to vertical whole body vibration linear lumped parameter models of the apparent masses of human subjects in standing positions when exposed to vertical whole body vibration have been developed simple models with a single degree of freedom d o f and with two d o f were considered for practical use model parameters were optimised using both the mean apparent mass of 12 male subjects and the apparent masses of individual subjects measured in a previous study the calculated responses of two d o f models with a massless support structure showed best agreement with the measured apparent mass and phase with errors less than 0 1 in the normalised apparent mass i e corresponding to errors less than 10 of the static mass and errors less than 5 in the phase for a normal standing posture the model parameters obtained with the mean measured apparent masses of the 12 subjects were similar to the means of the 12 sets of parameters obtained when fitting to the individual apparent masses it was found that the effects of vibration magnitude and postural changes on the measured apparent mass could be represented by changes to the stiffness and damping in the two d o f models

a tree matching algorithm based on node splitting and merging an algorithm that computes the best matching of two trees is described the degree of mismatch i e the distance is measured in terms of the number of node splitting and merging operations required the proposed tree distance is a more appropriate measurement of structural defonnation than the tree distance measure in terms of the number of insertions deletions and substitutions of tree nodes as defined in previous studies an algorithm that uses a divide and conquer strategy is presented the analysis shows that the time complexity is o nm2 where n and al are the number of nodes of the two trees respectively the algorithm has been implemented on a vax 11 780

an open source full 3d electromagnetic modeler for 1d vti media in python empymod abstractthe python code empymod computes the 3d electromagnetic field in a layered earth with vertical transverse isotropy by combining and extending two earlier presented algorithms in this journal the bottleneck in frequency and time domain calculations of electromagnetic responses derived in the wavenumber frequency domain is the transformations from the wavenumber to the space domain and from the frequency to the time domain the so called hankel and fourier transforms three different hankel transform methods quadrature quadrature with extrapolation qwe and filters and four different fourier transform methods fast fourier transform fft fftlog qwe and filters are included in empymod which allows us to compare these different methods in terms of speed and precision the best transform in terms of speed and precision depends on the modeled frequencies published digital filters for the hankel transform are very fast and precise for frequencies in the range of controlled source electromag

constrained string editing abstract let x and y be any two strings of finite length we consider the problem of transforming x to y using the edit operations of deletion insertion and substitution the optimal transformation is the one which has the minimum edit distance associated with it the problem of computing this distance and the optimal transformation using no edit constraints has been studied in the literature in this paper we consider the problem of transforming x to y using any arbitrary edit constraint involving the number and type of edit operations to be performed an algorithm is presented to compute the minimum distance associated with editing x to y subject to the specified constraint the algorithm requires o x y min x y time and space the technique to compute the optimal transformation is also presented

approximation for bessel functions and their application in the computation of hankel transforms we present rational approximations of the bessel functions jv x v 0 1 10 which can be used to simplify the computation of the hankel transform to the computation of two fourier transforms

theoretical foundation methods and criteria for calibrating human vibration models using frequency response functions while simulations of the measured biodynamic responses of the whole human body or body segments to vibration are conventionally interpreted as summaries of biodynamic measurements and the resulting models are considered quantitative this study looked at these simulations from a different angle model calibration the specific aims of this study are to review and clarify the theoretical basis for model calibration to help formulate the criteria for calibration validation and to help appropriately select and apply calibration methods in addition to established vibration theory a novel theorem of mechanical vibration is also used to enhance the understanding of the mathematical and physical principles of the calibration based on this enhanced understanding a set of criteria was proposed and used to systematically examine the calibration methods besides theoretical analyses a numerical testing method is also used in the examination this study identified the basic requirements for each calibration method to obtain a unique calibration solution this study also confirmed that the solution becomes more robust if more than sufficient calibration references are provided practically however as more references are used more inconsistencies can arise among the measured data for representing the biodynamic properties to help account for the relative reliabilities of the references a baseline weighting scheme is proposed the analyses suggest that the best choice of calibration method depends on the modeling purpose the model structure and the availability and reliability of representative reference data

electromagnetic modeling of three dimensional bodies in layered earths using integral equations we have developed an algorithm based on the method of integral equations to simulate the electromagnetic responses of three dimensional bodies in layered earths the inhomogeneities are replaced by an equivalent current distribution which is approximated by pulse basis functions a matrix equation is constructed using the electric tensor green s function appropriate to a layered earth and it is solved for the vector current in each cell subsequently scattered fields are found by integrating electric and magnetic tensor green s functions over the scattering currents efficient evaluation of the tensor green s functions is a major consideration in reducing computation time we find that tabulation and interpolation of the six electric and five magnetic hankel transforms defining the secondary green s functions is preferable to any direct hankel transform calculation using linear filters a comparison of responses over elongate three dimensional 3 d bodies with responses over two dimensional 2 d bodie

fast hankel transform by fast sine and cosine transforms the mellin connection the hankel transform of a function by means of a direct mellin approach requires sampling on an exponential grid which has the disadvantage of coarsely undersampling the tail of the function a novel modified hankel transform procedure that does not require exponential sampling is presented the algorithm proceeds via a three step mellin approach to yield a decomposition of the hankel transform into a sine a cosine and an inversion transform which can be implemented by means of fast sine and cosine transforms

string alignment with substitution insertion deletion squashing and expansion operations abstract let x and y be any two strings of finite length the problem of transforming x to y using the edit operations of substitution deletion and insertion has been extensively studied in the literature the problem can be solved in quadratic time if the edit operations are extended to include the operation of transposition of adjacent characters and is np complete if the characters can be edited repeatedly in this paper we consider the problem of transforming x to y when the set of edit operations is extended to include the squashing and expansion operations whereas in the squashing operation two or more contiguous characters of x can be transformed into a single character of y in the expansion operation a single character in x may be expanded into two or more contiguous characters of y these operations are typically found in the recognition of cursive script a quadratic time solution to the problem has been presented this solution is optimal for the infinite alphabet case the strategy to compute the sequence of edit operations is also presented

mathematical models for the apparent mass of the seated human body exposed to vertical vibration alternative mathematical models of the vertical apparent mass of the seated human body are developed the optimum parameters of four models two single degree of freedom models and two two degree of freedom models are derived from the mean measured apparent masses of 60 subjects 24 men 24 women 12 children previously reported the best fits were obtained by fitting the phase data with single degree of freedom and two degree of freedom models having rigid support structures for these two models curve fitting was performed on each of the 60 subjects so as to obtain optimum model parameters for each subject for the averages of each of the three groups of subjects and for the entire group of subjects the values obtained are tabulated use of a two degree of freedom model provided a better fit to the phase of the apparent mass at frequencies greater than about 8 hz and an improved fit to the modulus of the apparent mass at frequencies around 5 hz it is concluded that the two degree of freedom model provides an apparent mass similar to that of the human body but this does not imply that the body moves in the same manner as the masses in this optimized two degree of freedom model

pattern recognition of strings with substitutions insertions deletions and generalized transpositions abstract we study the problem of recognizing a string y which is the noisy version of some unknown string x chosen from a finite dictionary h the traditional case which has been extensively studied in the literature is the one in which y contains substitution insertion and deletion sid errors although some work has been done to extend the traditional set of edit operations to include the straightforward transposition of adjacent eharacters see j assoc comput mach 22 177 183 1975 the problem is unsolved when the transposed characters are themselves subsequently substituted as is typical in cursive and typewritten script in molecular biology and in noisy chain coded boundaries in this paper we present the first reported solution to the analytic problem of editing one string x to another y using these four edit operations a scheme for obtaining the optimal edit operations has also been given both these solutions are optimal for the infinite alphabet case using these algorithms we present a syntactic pattern recognition scheme which corrects noisy text containing all these types of errors the paper includes experimental results involving sub dictionaries of the most common english words which demonstrate the superiority of our system over existing methods

dual algorithms for fast calculation of the fourier bessel transform this paper presents a new procedure for the fast calculation of the fourier bessel transform the computation is performed in a dual mode and involves two matched algorithms the first of which provides the lower order components while the second yields intermediate and higher order samples of the transform the first algorithm is based on the fourier selection summation fss method derived in a previous study while the second relies on the bessel function large argument asymptotic expansion it is shown that the dual procedure constructed along these lines requires a computation time which is about four times that needed by a single n point fast fourier transform

elementary approximations for zeros of bessel functions let jvk yvk and cvk denote the kth positive zeros of the bessel functions jv x yv x and of the general cylinder function cv x cos jv x sin yv x 0 respectively in this paper we extend to cvk k 2 3 some linear inequalities presently known only for jvk in the case of the zeros yvk we are able to extend these inequalities also to k 1 finally in the case of the first positive zero jv1 we compare the linear enequalities given in 9 with some other known inequalities

an algorithm for computing general integer order hankel transforms a tomographic image reconstruction algorithm that we have been studying requires the nth order hankel transform for the nth function in a series where n varies over a set of integers unfortunately most previously proposed algorithms have either dealt with only zeroth order transforms or cannot be applied conveniently to our problem we propose an algorithm for computing general integer order hankel transforms the algorithm takes samples of equally spaced input functions and gives equally spaced samples of the transforms

algorithms to numerically evaluate the hankel transform abstract the efficient and accurate evaluation of the hankel transform is required in a number of applications this paper reviews a number of algorithms that have only recently been exposed in the literature results of a comparative study of some useful algorithms are presented it is found that the performance of all algorithms depends on the type of function to be transformed the projection based methods provide acceptable accuracy with better efficiency than numerical quadrature

fast hankel transform algorithm the hankel or fourier bessel transform is an important computational tool for optics acoustics and geophysics it may be computed by a combination of an abel transform which maps an axisymmetric two dimensional function into a line integral projection and a one dimensional fourier transform this paper presents a hankel transform algorithm using a fast linear time abel transform followed by an fft

is the fast hankel transform faster than quadrature the fast hankel transform fht implemented with digital filters has been the algorithm of choice in em geophysics for a few decades however other disciplines have predominantly relied on methods that break up the hankel transform integral into a sum of partial integrals that are each evaluated with quadrature the convergence of the partial sums is then accelerated through a nonlinear sequence transformation while such a method was proposed for geophysics nearly three decades ago it was demonstrated to be much slower than the fht this work revisits this problem by presenting a new algorithm named quadrature with extrapolation qwe the qwe method recasts the quadrature sum into a form conceptually similar to the fhtapproach by using a fixed point quadrature rule the sum of partial integrals is efficiently accelerated using the shanks transformation computed with wynn s algorithm a matlab implementation of the qwe algorithm is compared with the fht method for accuracy and speed on a suite of relevant modeling problems including frequency domain controlledsource em time domain em and a large loop magnetic source problem surprisingly the qwe method is faster than the fht for all three problems however when the integral needs to be evaluated at many offsets and the lagged convolution variant of the fht is applicable the fht is significantly faster than the qwe method for divergent integrals such as those encountered in the large loop problem the qwe method can provide an accurate answer when the fht method fails

a body mass dependent mechanical impedance model for applications in vibration seat testing abstract a three degree of freedom model is proposed to predict the biodynamic responses of the seated human body of different masses a baseline model is initially derived to satisfy both the mean apparent mass and seat to head transmissibility responses proposed in iso dis 5982 2000 applicable for mean body mass of 75 kg the validity of the resultant generic mass dependent model is verified by comparing the apparent mass and driving point mechanical impedance responses computed for total body masses of 55 75 and 90 kg with the range of idealized values proposed for body masses within the 49 93 kg range considering the lack of data that could be found to define the apparent mass mechanical impedance of subjects with different body masses when applying the experimental conditions defined in iso dis 5982 2000 an attempt is made to adapt the parameters of the base model to fit the measured apparent mass data applicable to groups of automobile occupants within different mass ranges this is achieved through constrained parametric optimization which consists of minimizing the sum of squared errors between the computed response and the mean apparent mass data measured for automobile occupants within four mass groups less than 60 kg 60 5 70 5 kg 70 5 80 kg and above 80 kg the results show a reasonably good agreement between the model responses and the measured apparent mass data particularly at frequencies below 10 hz the results suggest that the proposed mass dependent model can effectively predict the apparent mass responses of automobile occupants over a wide range of body masses and for two different postures passenger hands in lap and driver hands on steering wheel postures

effective capacity of l_p norm diversity receivers over generalized fading channels under adaptive transmission schemes this paper presents novel moment generating function mgf and characteristic function chf based frameworks for the ec performance analysis of a generic l p norm diversity combining scheme under adaptive transmission policies the considered system operates over generalized fading channels a maximum delay constraint and under various channel state information csi conditions depending upon the operational csi four policies are studied namely i constant power with optimal rate adaptation ora ii optimal power and rate adaptation opra iii channel inversion with fixed rate cifr and iv truncated cifr tifr the l p norm diversity is a generic diversity structure which includes as special cases various well known diversity schemes such as equal gain combining egc maximal ratio combining mrc and amplify and forward af relaying under the ora and opra policies we derive single integral expressions for evaluating the ec of l p norm diversity reception directly from the mgf or the incomplete mgf of the signal to noise ratio snr at the receiver respectively for the ec performance evaluation of the egc and af relaying systems operating under the opra policy a chf based approach which is computationally more efficient as compared to the mgf based approach is further presented it is shown that the ec for the cifr and tifr policies can be directly evaluated from the mgf or the chf of the snr at the receiver respectively for the ora policy a novel analytical approach for the asymptotic ec performance analysis is also developed and evaluated revealing how important system operation parameters affect the overall system performance the mathematical formalism is validated with selected numerical and equivalent simulation performance evaluation results thus confirming the correctness of the proposed analytical methodology

quantification of changes in modal parameters due to the presence of passive people on a slender structure abstract this work proposes a method to predict changes in modal parameters of a generic structure due to the presence of passive people the method requires to accurately know the modal model of the empty structure i e natural frequencies damping ratios and mode shapes no restriction on the number of degrees of freedom of the structure is required each passive subject on the structure is modelled through his apparent mass and is introduced locally on the empty structure to obtain a model of the joint human structure system to include the apparent mass of the subjects in the model both measurements and models available in literature were used the effect of using different models of the apparent mass was investigated and the effect of using apparent masses obtained with different levels of vibration was analysed the proposed model was validated by means of experimental tests carried out on a lightly damped staircase the empty structure was first tested to obtain its modal model in order to apply the proposed approach after performing several tests with passive people standing on the structure the experimental results showed small changes of natural frequencies increase or decrease and a high increase of damping ratios due to people s presence thus the proposed approach was used to predict the above mentioned changes the measured and predicted frequency response functions natural frequencies and damping ratios were compared in all the cases taken into consideration the predicted results fitted with the experimental evidence

development of a two dimensional dynamic model of the foot ankle system exposed to vibration abstract workers in mining mills construction and some types of manufacturing are exposed to vibration that enters the body through the feet exposure to foot transmitted vibration ftv is associated with an increased risk of developing vibration induced white foot viwft viwft is a vascular and neurological condition of the lower limb leading to blanching in the toes and numbness and tingling in the feet which can be disabling for the worker this paper presents a two dimensional dynamic model describing the response of the foot ankle system to vibration using four segments and eight kelvin voigt models the parameters of the model have been obtained by minimizing the quadratic reconstruction error between the experimental and numerical curves of the transmissibility and the apparent mass of participants standing in a neutral position the average transmissibility at five locations on the foot has been optimized by minimizing the difference between experimental data and the model prediction between 10 and 100 hz the same procedure has been repeated to fit the apparent mass measured at the driving point in a frequency range between 2 and 20 hz monte carlo simulations were used to assess how the variability of the mass stiffness and damping matrices affect the overall data dispersion results showed that the 7 of freedom model correctly described the transmissibility the average transmissibility modulus error was 0 1 the error increased when fitting the transmissibility and apparent mass curves the average modulus error was 0 3 however the obtained values were reasonable with respect to the average inter participant variability experimentally estimated at 0 52 for the modulus study results can contribute to the development of materials and equipment to attenuate ftv and consequently lower the risk of developing viwft

an improved algorithm for approximate string matching given a text string a pattern string and an integer k a new algorithm for finding all occurrences of the pattern string in the text string with at most k differences is presented both its theoretical and practical variants improve upon the known algorithms

an algorithm for the computation of zeros of a special class of entire functions abstract a two stage algorithm is presented for computing the zeros of a special class of entire functions the first stage which has linear convergence produces two sided bounds for the zeros these are then used as data for the second stage which employs a cubically convergent iterative process with monotonic convergence to the zeros from below and above appropriate modifications to the algorithm in order that it be applicable to certain real polynomials are also included

simultaneous calculation of fourier bessel transforms up to order n abstract in many practical applications it is necessary to calculate the first n fourier bessel transforms this paper describes procedures allowing the simultaneous evaluation of these transforms the calculation involves a basic one dimensional fourier transform repeated selection of suitable fourier components followed by successive evaluation of fourier series coefficients determination of l samples of the first n fourier bessel transforms requires of the order of 2 ln log 2 n operations and this number is comparable to the operation count corresponding to a two dimensional discrete fourier transform

an effective algorithm for string correction using generalized edit distance ii computational complexity of the algorithm and some applications this paper deals with the problem of estimating an unknown transmitted string xs belonging to a finite dictionary h from its observable noisy version y in the first part of this paper 18 we have developed an algorithm referred to as algorithm i to find the string x h which minimizes the generalized levenshtein distance d xy in this part of the paper we study the computational complexity of algorithm i and illustrate quantitatively the advantage algorithm i has over the standard technique and other algorithms its superiority has been shown for various dictionaries including the one consisting of the 1021 most common english words of length greater than unity 23 a comparison between algorithm i and other algorithms used to correct misspelled words of a regular language is also made here some applications of algorithm i are also discussed

a hybrid fast hankel transform algorithm for electromagnetic modeling a hybrid fast hankel transform algorithm has been developed that uses several complementary features of two existing algorithms anderson s digital filtering or fast hankel transform fht algorithm and chave s quadrature and continued fraction algorithm a hybrid fht subprogram called hybfht written in standard fortran 77 provides a simple user interface to call either subalgorithm the hybrid approach is an attempt to combine the best features of the two subalgorithms in order to minimize the user s coding requirements and to provide fast execution and good accuracy for a large class of electromagnetic problems involving various related hankel transform sets with multiple arguments special cases of hankel transforms of double order and double argument are discussed where use of hybfht is shown to be advantageous for oscillatory kernel functions

evaluation of bessel function integrals with algebraic singularities abstract a new method for the numerical evaluation of 1 0 1 x x j v ax dx is proposed where a are given constants and j is the bessel function of the first kind and of order it is assumed that f is a smooth function the method is based on approximation of the function f by a polynomial given in the form of a linear combination of the shifted jacobi polynomials r k and on the use of chebyshev series expansion for the function j ax

simple fast algorithms for the editing distance between trees and related problems ordered labeled trees are trees in which the left to right order among siblings is significant the distance between two ordered trees is considered to be the weighted number of edit operations insert delete and modify to transform one tree to another the problem of approximate tree matching is also considered specifically algorithms are designed to answer the following kinds of questions 1 what is the distance between two trees 2 what is the minimum distance between t 1 and t 2 when zero or more subtrees can be removed from t 2 3 let the pruning of a tree at node n mean removing all the descendants of node n the analogous question for prunings as for subtrees is answered a dynamic programming algorithm is presented to solve the three questions in sequential time o t 1 times t 2 times min textit depth t 1 textit leaves t 1 times min textit depth t 2 textit leaves t 2 and space o t 1 times t 2 compared with o t 1 times t 2 t

an median graphs properties algorithms and applications in object prototype learning and similar tasks median computation is an important technique for capturing the essential information of a given set of patterns we extend the median concept to the domain of graphs in terms of graph distance we introduce the novel concepts of set median and generalized median of a set of graphs we study properties of both types of median graphs for the more complex task of computing generalized median graphs a genetic search algorithm is developed experiments conducted on randomly generated graphs demonstrate the advantage of generalized median graphs compared to set median graphs and the ability of our genetic algorithm to find approximate generalized median graphs in reasonable time application examples with both synthetic and nonsynthetic data are shown to illustrate the practical usefulness of the concept of median graphs

a hankel transform approach to tomographic image reconstruction a relatively unexplored algorithm is developed for reconstructing a two dimensional image from a finite set of its sampled projections the algorithm referred to as the hankel transform reconstruction htr algorithm is polar coordinate based the algorithm expands the polar form fourier transform f r theta of an image into a fourier series in theta calculates the appropriately ordered hankel transform of the coefficients of this series giving the coefficients for the fourier series of the polar form image f p phi resolves this series giving a polar form reconstruction and interpolates this reconstruction to a rectilinear grid the htr algorithm is outlined and it is shown that its performance compares favorably to the popular convolution backprojection algorithm

application of dcim on marine controlled source electromagnetic survey the discrete complex image method dcim is used to calculate the mixed potential electric field integral equation the dcim has been used broadly in high frequency domain and now is successfully introduced to the extremely low frequency situation of marine controlled source electromagnetic mcsem survey the integral path in high frequency situation does not hold valid for extremely low frequency situation the reason can be ascribed to the change of wave number formulas a new integral path suitable for the extremely low frequency situation is proposed the appropriate ranges of the parameters used in dcim are given the computation is stable at these considerably large ranges the results of a five layer model calculated with dcim are compared with those with the filter method and the direct integral method the computation time with dcim is comparable to the time with filter method the effects of water depth upper sediment thickness and oil layer thickness are studied with dcim the results show that electric field varies with the change of thickness the effects accord to the physical meanings of mcsem survey it is safe to conclude that the dcim with the new path is valid in mcsem survey

fast nth order hankel transform algorithm an nth order hankel transform also called fourier bessel transform algorithm designed for many analytically defined functions is presented this algorithm is not restricted to order zero as such it provides greater generality than many others the traditional difficulty in the evaluation of hankel transforms the presence of bessel functions in the kernel of the integral transform is eliminated in this new hankel transform algorithm the algorithm presented is composed of a fast linear time nth order chebyshev transform followed by a fast fourier transform

chebyshev series approximations for the zeros of the bessel functions on note le sieme zero de j v x par j v s on presente des approximations pour j v s dans la region des valeurs de v et de s petites