the equations of motion of curved pipes conveying fluid abstract the non linear differential equations of motion of a fluid conveying pipe the no flow configuration of which is in the shape of a one dimensional line arbitrarily curved and twisted in space are derived by making use of the newtonian approach the extensible dynamics of the beam is based on the timoshenko beam theory some significant differences with the equations available in the open literature are discussed the stressed by flow configuration is found to be the only equilibrium state adequate for the study of the linear stability of such pipe fluid systems

the equations of motion of initially stressed timoshenko tubular beams conveying fluid abstract in this paper the equations of motion of an initially stressed timoshenko tubular beam subjected to a tensile follower load and conveying fluid are derived by using the appropriate statement of hamilton s principle this latter is obtained first for open systems the instantaneous total mass of which does not necessarily remain constant in the course of deformation open denoting that there is momentum transport in and out of the system the equations of motion are derived separately for a cantilevered system and for one with both extremities of the tube clamped yet another derivation for the cantilevered tube is presented with the system considered to be quasi closed where all flow induced effects are incorporated through the virtual work as if they were external forces all three sets of equations are found to be identical these equations are then compared with those obtained more simply by the newtonian force balance approach some differences between them are found to exist the principal of which are associated with the follower or other tensile forces these are discussed at some length and the equations of motion obtained here are compared to those obtained by other researchers for timoshenko beams subjected to follower or tensile forces

3 d sound source reconstruction and field reprediction using the helmholtz integral equation abstract a method for reconstruction of the boundary conditions of an arbitrarily shaped three dimensional 3 d sound source from a finite number of field pressures is presented and the associated field is repredicted by using the helmholtz integral equation to minimize the reconstruction error due to noise in the field pressures a filtering method is proposed and it is verified that numerically singular values which correspond to the higher order modes of the evanescent like components of the source velocities are eliminated for arbitrarily shaped sources with complex boundary conditions the reconstruction is performed accurately when the size of each element is less than a quarter wavelength and the field measurement positions are equally or randomly distributed on the surface of a sphere in the vicinity of the source our technique can be used in computer aided loudspeaker design that reconstructs loudspeaker diaphragm velocities from the finite number of field pressures and repredicts the variation of the sound field procuced by a redesigned loudspeaker cabinet on which the reconstructed diaphragm is mounted

the use of chief to obtain unique solutions for acoustic radiation using boundary integral equations this report is concerned with the problem of obtaining a unique solution for radiation problems at characteristic wavenumbers when a boundary integral equation formulation is used it is shown that the combined helmholtz integral equation formulation chief method works even when numerous interior points lie exactly on nodal surfaces of a mode corresponding to an eigenfrequency of the related interior problem when at least one interior point does not lie on a nodal surface the use of chief is illustrated with numerical radiation experiments for the sphere and the finite cylinder chief is compared to the helmholtz gradient formulation hgf for circumventing nonuniqueness and is found to yield a more accurate solution in at least one published example a procedure is used to indicate the solution error when using integral equation methods with or without a technique to circumvent nonuniqueness this procedure uses the velocity potential of an interior point as an indicator of solution error in all cases considered the interior potential correctly indicated a good or bad solution whereas the matrix condition number falsely indicated a bad solution in several instances work supported in part by onr

boundary element analysis for the helmholtz eigenvalue problems with a multiply connected domain for a helmholtz eigenvalue problem with a multiply connected domain the boundary integral equation approach as well as the boundary element method is shown to yield spurious eigenvalues even if the complex valued kernel is used in such a case it is found that spurious eigenvalues depend on the geometry of the inner boundary demonstrated as an analytical case the spurious eigenvalue for a multiply connected problem with its inner boundary as a circle is studied analytically by using the degenerate kernels and circulants an annular case can be studied analytically in a discrete system and can be treated as a special case the proof for the general boundary instead of the circular boundary is also derived the burton miller method is employed to eliminate spurious eigenvalues in the multiply connected case moreover a modified method considering only the real part formulation is provided five examples are shown to demonstrate that the spurious eigenvalues depend on the shape of the inner boundary good agreement between analytical prediction and numerical results are found

estimating the number of classes in a finite population abstract we use an extension of the generalized jackknife approach of gray and schucany to obtain new nonparametric estimators for the number of classes in a finite population of known size we also show that generalized jackknife estimators are closely related to certain horvitz thompson estimators to an estimator of shlosser and to estimators based on sample coverage in particular the generalized jackknife approach leads to a modification of shlosser s estimator that does not suffer from the erratic behavior of the original estimator the performance of both new and previous estimators is investigated by means of an asymptotic variance analysis and a monte carlo simulation study

analytical study and numerical experiments for radiation and scattering problems using the chief method in this paper the well known failure in numerical computations of the exterior helmholtz integral equation at certain characteristic frequencies is investigated analytically and numerically the combined helmholtz integral equation formulation chief method is a very popular technique that can overcome the non unique problem but this method breaks down if the interior points are not properly chosen the chief method in conjunction with the singular value decomposition svd technique is an easy and efficient method to ensure a unique solution for the exterior problem based on the circulant properties and degenerate kernels an analytical scheme in discrete system of a cylinder is achieved the optimum numbers and proper positions for the collocation points in the interior domain are analytically studied and suggested in the numerical scheme numerical experiments are designed to verify the analytical results one analytical example for a circular cylinder and one numerical example for a square rod are demonstrated to show the validity of the chief method

development of an energy boundary element formulation for computing high frequency sound radiation from incoherent intensity boundary conditions an energy boundary element analysis ebea formulation is presented for calculating sound radiation at high frequency from a radiator with arbitrary shape the ebea development presented in this paper compliments previous energy finite element analysis efea developments for computing high frequency vibration of structures immersed in an acoustic medium from the efea solution the structural vibrational energy throughout the structure and the acoustic power radiated from each surface element in contact with the surrounding fluid are computed the ebea utilizes the information for the acoustic power radiated from each element of the outer surface of the structure as a boundary condition in order to compute the acoustic field in an unbound medium with no damping that surrounds the radiating structure since the structural vibration between different elements is considered as incoherent in the efea the acoustic intensity associated with each surface element that radiates in the surrounding medium is also considered as incoherent between different elements in the ebea formulation the governing integral equation of ebea is established and a numerical solution is presented the present method is validated by comparing ebea results to analytical solutions and to numerical results from an axi symmetric hp finite element code with infinite acoustic elements suitable for structural acoustic computations good correlation is demonstrated for all the analyses

application of the transfer matrix method to non conservative systems involving fluid flow in curved pipes abstract the application of the transfer matrix method to problems of fluid flow in planar curved pipes is presented also a presentation is given of how to deal with the stability of non conservative problems when using the dynamic method in the method proposed account is taken of the effect of the initial state of stress on the dynamic behaviour of the pipe three well known problems are solved to verify the convergence and applicability of the transfer matrix formulation to non conservative problems involving fluid flow

jackknifing and bootstrapping goodness of fit statistics in sparse multinomials abstract many goodness of fit problems can be put in the following form n n 1 nk is a multinomial n vector and it is desired to test the composite null hypothesis h 0 p against all possible alternatives the usual tests used are pearson s 1900 statistic or the likelihood ratio statistic neyman and pearson 1928 cressie and read 1984 pointed out that both of these statistics are in the power family of statistics with 1 and 0 respectively they suggested an alternative statistic with although all of these statistics are asymptotically 2 in the usual situation of k fixed and n this is not the case if the multinomial is sparse specifically morris 1975 showed that under certain regularity conditions with k and n both x 2 and g 2 are asymptotically normal with different mean and variance under a simple null hypothesis cressie and read 1984 extended these results to the general 2ni family although these results have not been proven for composite nul

studies of domain based formulations for computing exterior problems of acoustics a strategy must be devised to compute solutions over domains which are unbounded exact impedance conditions at an artificial external boundary are specified by the dtn method yielding an equivalent problem that is suitable for domain based computation the dtn boundary condition is non reflective giving rise to exact and thereby unique solutions the truncated dtn operator which is employed in practice fails to inhibit the reflection of higher modes so that non unique solutions may occur at their harmonics simple expressions determine a sufficient number of terms in the truncated operator for unique solutions at any given wave number there are three characteristic length scales in the computational problem the radius of the artificial boundary the geometry of the body represented by the internal boundary and the mesh size

a hybrid bie ffp scheme for predicting barrier efficiency outdoors to assess the acoustical performance of noise screens in the presence of an arbitrary sound speed profile a numerical scheme based on a combination of the boundary integral and fast field program methods is developed the green s function required in the boundary integral is evaluated by a fast field formulation the procedure is validated by comparing its predictions with other numerical results for simple cases and with measurements for indoor model experiments simulating downward refracting conditions it is predicted that the performance of a noise screen placed 50 m from the source is reduced considerably by moderate downwind conditions

spurious and true eigensolutions of helmholtz bies and bems for a multiply connected problem the spurious eigenvalues of an annular domain have been verified for the singular and hypersingular boundary element methods bems and circumvented by using the burton miller approach do they also occur in other formulations continuous formulations such as the singular and hypersingular boundary integral equations bies the null field bies and the fictitious bies or such discrete formulations as the null field bems and the fictitious bems for the ten formulations of the multiply connected problem the study of otherwise the same issues is continued in the present paper by using the degenerate kernels and the fourier series it is demonstrated analytically for the six continuous formulations of bies that spurious eigensolutions depend on the geometry of the inner boundary but not on that of the outer boundary this conclusion can be extended to the six discrete formulations of bems to filter out the spurious eigenvalues the chief combined helmholtz integral equation formulation method is used here instead of the burton miller approach the optimum number and appropriate positions of the chief points are also addressed it is then shown that in the null field and fictitious bems the spurious and true eigenvalues can be detected and distinguished by using the singular value decomposition updating techniques in conjunction with the fredholm alternative theorem illustrative examples show the validity of the proposed methodologies

small sample estimation of species richness applied to forest communities summary many well known methods are available for estimating the number of species in a forest community however most existing methods result in considerable negative bias in applications where field surveys typically represent only a small fraction of sampled communities this article develops a new method based on sampling with replacement to estimate species richness via the generalized jackknife procedure the proposed estimator yields small bias and reasonably accurate interval estimation even with small samples the performance of the proposed estimator is compared with several typical estimators via simulation study using two complete census datasets from panama and malaysia

bootstrapped insights into empirical applications of stochastic dominance bootstrapping a very versatile statistical technique significantly amplifies the understanding and success of empirical applications of stochastic dominance its ability to calculate the standard deviations of order statistics reveals the uncertainty of the critical estimates of the tails of cumulative density functions understanding this uncertainty reveals why a wide variety of tail shapes all cause a notable loss in power for stochastic dominance tests simulations show that the smoothing inherent in bootstrapping can significantly increase the power of the tests when dominance exists in the population

analytical investigation for true and spurious eigensolutions of multiply connected membranes containing elliptical boundaries using the dual biem it is well known that the boundary element method may induce spurious eigenvalues while solving eigenvalue problems the finding that spurious eigenvalues depend on the geometry of inner boundary and the approach utilized has been revealed analytically and numerically in the literature however all the related efforts were focused on eigenproblems involving circular boundaries on the other hand the extension to elliptical boundaries seems not straightforward and lacks of attention accordingly this paper performs an analytical investigation of spurious eigenvalues for a confocal elliptical membrane using boundary integral equation methods biem in conjunction with separable kernels and eigenfunction expansion to analytically study this eigenproblem the elliptic coordinates and mathieu functions are adopted the fundamental solution is expanded into the separable kernel by using the elliptic coordinates and the boundary densities are expanded by using the eigenfunction expansion the jacobian terms may exist in the separable kernel boundary density and boundary contour integration and they can cancel each other out therefore the orthogonal relations are reserved in the boundary contour integration in this way a similar finding about the mechanism of spurious eigenvalues is found and agrees with those corresponding to the annular case to verify this finding the boundary element method and the commercial finite element code abaqus are also utilized to provide eigensolutions respectively for comparisons good agreement is observed from comparisons based on the adaptive observer system the present approach can deal with eigenproblems containing circular and elliptical boundaries at the same time in a semi analytical manner by using the biem it is found that spurious eigenvalues are the zeros of the modified mathieu functions which depend on the inner elliptical boundary and the integral formulation finally several methods including the chief method the svd updating technique and the burton miller method are employed to filter out the spurious eigenvalues respectively in addition the efficiency of the chief method is better than those of the svd updating technique and the burton miller approach since not only hypersingularity is avoided but also computation effort is saved

a new form of the hypersingular boundary integral equation for 3 d acoustics and its implementation with c0 boundary elements abstract an improved weakly singular form of the hypersingular boundary integral equation hbie for 3 d acoustic wave problems is presented in this paper compared with the weakly singular form of the hbie published earlier y j liu and f j rizzo a weakly singular form of the hypersingular boundary integral equation applied to 3 d acoustic wave problems comput methods appl mech engrg 96 1992 271 287 this new form involves only tangential derivatives of the density function and thus its discretization using the boundary element method bem is easier to perform instead of using nonconforming and c1 continuous boundary elements advocated earlier c0 continuous conforming quadratic elements are employed in the discretization of this weakly singular form of the hbie some justifications on using c0 elements for hbies are provided to reflect the current views on this crucial issue for hbies it is postulated that the original c1 continuity requirement for the density function in the analytical hbie formulation can be relaxed to piecewise c1 continuity in the numerical implementation of the weakly singular forms of the hbie numerical examples of both scattering and radiation problems clearly demonstrate the accuracy and versatility of the new weakly singular form of the hbie for 3 d acoustics

nonparametric lower bounds for species richness and shared species richness under sampling without replacement summary a number of species richness estimators have been developed under the model that individuals or sampling units are sampled with replacement however if sampling is done without replacement so that no sampled unit can be repeatedly observed then the traditional estimators for sampling with replacement tend to overestimate richness for relatively high sampling fractions ratio of sample size to the total number of sampling units and do not converge to the true species richness when the sampling fraction approaches one based on abundance data or replicated incidence data we propose a nonparametric lower bound for species richness in a single community and also a lower bound for the number of species shared by multiple communities our proposed lower bounds are derived under very general sampling models they are universally valid for all types of species abundance distributions and species detection probabilities for abundance data individuals detectabilities are allowed to be heterogeneous among species for replicated incidence data the selected sampling units e g quadrats need not be fully censused and species can be spatially aggregated all bounds converge correctly to the true parameters when the sampling fraction approaches one real data sets are used for illustration we also test the proposed bounds by using subsamples generated from large real surveys or censuses and their performance is compared with that of some previous estimators

diffraction of acoustic waves by rigid plane baffles the integral equation method is applied to study the diffraction of acoustic waves by rigid plane baffles such as a circular disk and a ring a set of six real fredholm integral equations of the second kind is solved simultaneously to determine the velocity potentials on a circular disk these equations are transformed into discrete forms by applying the gauss legendre quadrature formula in the radial direction and the best possible numerical integration formula in the angular direction the discrete equations are solved by the method of successive approximations which is also called the direct integral equation method a new method is also developed to take care of integrations involving the cauchy principal values which occur when the moving point coincides with the fixed point the accuracy of the present numerical approach has been tested by computing the excess pressure ratio p p0 on the surfaces of a circular disk exposed to a plane wave and by comparing it with both analytical and experimental

an estimator of number of species from quadrat sampling summary we consider the problem of estimating the number of distinct species s in a study area from the recorded presence or absence of species in each of a sample of quadrats a generalized jackknife estimator of s is derived along with an estimate of its variance it is compared with the jackknife estimator for s proposed by heltshe and forrester 1983 biometrics39 1 12 and the empirical bayes estimator of mingoti and meeden 1992 biometrics48 863 875 we show that the empirical bayes estimator has the form of a generalized jackknife estimator under a specific model for species distribution we compare the new estimators of s to the empirical bayes estimator via simulation we characterize circumstances under which each is superior

a simple method avoiding non uniqueness in the boundary element method for acoustic scattering problem the boundary element method bem is widely used for sound field analysis problems however it has a non uniqueness problem in the exterior domain various methods to avoid this problem have been developed however these are not easily applied to the bem in this paper a simple method called the ica ring inner cavity ringing method is proposed for avoiding the non uniqueness problem and this method is applied to the bem in both single and plural domains the concept of the ica ring method is that a scatterer in free space is hollowed as a shell and the volume is smaller the eigenfrequencies are shifted to a higher range next the mechanism of the non uniqueness problem in plural domains and a reason of the application of the ica ring method to the case of plural domains are explained finally some results calculated by the bem using the ica ring method are shown the calculational condition is that a cylinder with radius 0 125m floats in two dimensional free space in this case no calculationa

nonparametric estimation of species richness two procedures the jackknife and the bootstrap are discussed as methods for estimating the number of species by the sampling of quadrats explicit formulas for both procedures are presented and evaluated under a model with a random distribution of individuals the jackknife and bootstrap are shown to reduce the bias although they underestimate the actual number of species if there is a large number of rare species and the number of quadrats sampled is small when a small number of quadrats is sampled the jackknife is shown to give better estimates when the number of quadrats is large the jackknife tends to overestimate the number of species and the bootstrap performs better

a boundary integral equation method for two dimensional acoustic scattering problems this work formulates the singularity free integral equations to study 2 d acoustic scattering problems to avert the nonuniqueness difficulties burton s and burton and miller s methods are employed to solve the dirichlet and neumann problems respectively the surface helmholtz integral equations and their normal derivative equations in bounded form are derived the weakly singular integrals are desingularized by subtracting a term from the integrand and adding it back with an exact value depending on the relevant problem the additional integral can finally be either expressed in an explicit form or transformed to form a surface source distribution of the related equipotential body the hypersingular kernel is desingularized further using some properties of an interior laplace problem the new formulations are advantageous in that they can be computed by directly using standard quadrature formulas also discussed is the contour a unique feature of 2 d problems instead of dividing the boundary surface into several small elements a parametric representation of a 2 d boundary curve is further proposed to facilitate a global numerical implementation calculations consist of acoustic scattering by a hard and a soft circular cylinder respectively comparing the numerical results with the exact solutions demonstrates the proposed method s effectiveness

a semi analytical approach for radiation and scattering problems with circular boundaries in this paper the radiation and scattering problems with circular boundaries are studied by using the null field integral equations in conjunction with degenerate kernels and fourier series to avoid calculating the cauchy and hadamard principal values in implementation the null field point can be located on the real boundary owing to the introduction of degenerate kernels for fundamental solution an adaptive observer system of polar coordinate is considered to fully employ the property of degenerate kernels for the hypersingular equation vector decomposition for the radial and tangential gradient is carefully considered this method can be seen as a semi analytical approach since errors attribute from the truncation of fourier series neither hypersingularity in burton and miller approach nor the chief concepts were required to deal with the problem of irregular frequencies four gains well posed model singularity free boundary layer effect free and exponential convergence are achieved by using the present approach a fast convergence rate in exponential order than algebraic one in bem stems from the series expansions three examples were demonstrated to see the validity of the present formulation and show the better accuracy than bem

an integral equation approach to three dimensional acoustic radiation and scattering problems this paper provides numerical implementation and tests for a boundary integral equation method proposed recently by krutitskii ima j appl math 64 259 269 2000 for evaluating three dimensional acoustic radiation and scattering fields in the exterior neumann problem for several obstacles auxiliary boundaries with certain prescribed boundary conditions are introduced inside the obstacles for the purpose of eliminating the fictitious characteristic frequencies applying the simple source formulation on all boundaries leads to a set of uniquely solvable integral equations with weakly singular kernels to facilitate the numerical implementation the modified integral equations are further transformed to ordinary ones that contain nonsingular kernels only test cases consist of the acoustic radiation and scattering by one sphere and a pair of equal spheres comparisons are made with analytical solutions and schenck s chief method numerical results demonstrate the efficiency robustness and accuracy of

a note on methods for circumventing non uniqueness when using integral equations comparaison de la formulation de l equation integrale d helmholtz combinee et de la formulation du gradient d helmholtz pour resoudre les problemes de rayonnement acoustique et de diffusion acoustique

estimating the total number of distinct species using presence and absence data summary consider the problem of estimating the total number of distinct species in some specified region under investigation suppose the region is divided into n disjoint subregions or quadrats of equal area a sample of size n quadrats is chosen n 1 the other is to place at random n quadrats of equal area and fixed shape in the region of investigation in both cases the n quadrats in the sample are assumed to be disjoint and are totally observed so in fact when quadrat sampling is used a random sample of space is taken instead of a random sample of individuals it has been observed that species are often present with some natural clumping which creates dependence between quadrats and within quadrats heltshe and forrester 1983 and smith and van belle 1984 introduced some estimators for s when quadrat sampling is used see also burnham and overton 1979 the estimators they proposed are nonparametric and were developed by using jackknife and bootstrap arguments for a particular example palmer 1990 compared several estimators and showed that the first order jackknife estimator is preferred within this group in this paper we introduce some empirical bayes estimators for s when quadrat sampling is used by imposing a grid on the region the probabilistic model used to derive these estimators is basically a version of the efron and thisted 1976 model adapted to the case of quadrat

the decomposition of time varying hazard into phases each incorporating a separate stream of concomitant information abstract the hazard function of time related events such as death or reoperation following heart valve replacement often is time varying in a structured fashion as is the influence of risk factors associated with the events a completely parametric system is presented for the decomposition of time varying patterns of risk into additive overlapping phases descriptively labeled as early constant hazard and late each phase is shaped by a different generic function of time constituting a family of nested equations and is scaled by a separate logit linear or log linear function of concomitant information model building uses maximum likelihood estimation the resulting parametric equations permit hazard function survivorship function and probability estimates and their confidence limits to be portrayed and adjusted for concomitant information these provide a comprehensive analysis of time related events from which inferences may be drawn to improve for example the management of patients with valva

estimating species richness using the jackknife procedure an exact expression is given for the jackknife estimate of the number of species in a community and for the variance of this number when quadrat sampling procedures are used the jackknife estimate is a function of the number of species that occur in one and only one quadrat the variance of the number of species can be constructed as can approximate two sided confidence intervals the behavior of the jackknife estimate as affected by quadrat size sample size and sampling area is investigated by simulation

estimating diversity using quadrat sampling pielou 1966 journal of theoretical biology 13 131 144 first proposed the estimation of species diversity and its sampling error by using a pooled quadrat procedure heyer and berven 1973 ecology 54 642 645 modified this procedure by selecting the median of a group of sample permutations zahl 1977 ecology 58 907 913 introduced the jackknife estimation of species diversity under certain conditions pielou s pooled quadrat estimator is shown to be equivalent to zahl s jackknife estimator

h adaptive finite element computation of time harmonic exterior acoustics problems in two dimensions abstract in this paper we carry out adaptive finite element computations of the helmholtz equation in two dimensions in the context of time harmonic exterior acoustics the purpose is to demonstrate potentially significant cost savings engendered through adaptivity for propagating solutions at moderate wave numbers ka 2 4 the computations are performed on meshes of linear triangles and are adapted to the solution by locally changing element sizes h refinement the adaptive procedure involves applying an explicit residual based a posteriori error estimator and an h adaptive strategy which were derived in a previous paper the adaptive meshes are then obtained through global mesh regeneration using an advancing front mesh generator two different finite element formulations are considered the galerkin and galerkin least squares gls methods the infinite physical domain is truncated by an artificial exterior boundary on which a fully coupled dirichlet to neumann dtn boundary condition is applied two different problems are computed plane wave scattering by a rigid infinite surface circular and square cross sections and nonuniform radiation from an infinite circular cylinder detailed cost studies with respect to an active column direct solver are performed for the nonuniform radiation problem the adaptive mesh is twenty times more cost effective than a uniform mesh for galerkin when coupled with the gls formulation the adaptive mesh is forty times more efficient than galerkin computations on a uniform mesh

evaluation of the helmholtz boundary integral equation and its normal and tangential derivatives in two dimensions abstract this paper presents a means of evaluating singular integrals in the helmholtz boundary integral equation and its normal and tangential derivatives in two dimensions the subtraction addition technique is applied to the singular integral equations to convert the singular integrals to either ordinary integrals with bounded integrands or modified singular integrals including hypersingular integrals with exact integration values this regularization is performed before any discretization the modified integral equations can be calculated by directly applying standard quadrature rules over the entire integration domain numerical computations involve evaluating the acoustic field associated with a radiating inverse elliptic cylinder the velocity potential is obtained by applying the burton miller method which linearly combines the helmholtz boundary integral equation with its normal derivative to treat the fictitious characteristic frequencies further substituting the velocity potential into the regularized tangential derivative yields the surface tangential velocity comparing the numerical results with the analytical solutions verifies the effectiveness of the presented approach

a boundary integral equation method using auxiliary interior surface approach for acoustic radiation and scattering in two dimensions this paper presents an effective solution method for predicting acoustic radiation and scattering fields in two dimensions the difficulty of the fictitious characteristic frequency is overcome by incorporating an auxiliary interior surface that satisfies certain boundary condition into the body surface this process gives rise to a set of uniquely solvable boundary integral equations distributing monopoles with unknown strengths over the body and interior surfaces yields the simple source formulation the modified boundary integral equations are further transformed to ordinary ones that contain nonsingular kernels only this implementation allows direct application of standard quadrature formulas over the entire integration domain that is the collocation points are exactly the positions at which the integration points are located selecting the interior surface is an easy task moreover only a few corresponding interior nodal points are sufficient for the computation numerical calculations consist of the acoustic radiation and scattering by acoustically hard elliptic and rectangular cylinders comparisons with analytical solutions are made numerical results demonstrate the efficiency and accuracy of the current solution method