a general class of sliding surface for sliding mode control in the conventional sliding mode control the relative degree of the chosen sliding surface is usually one this paper addresses a general class of sliding surface whose relative degree is no longer restricted to one we show that when the relative degree is more than two it is inevitable that there will exist a limit cycle for the nonlinear sign function and for the case of relative degree two the system possesses poor phase margin however these disadvantages can be remedied remarkably by smoothing out the control nonlinearity in a suitable boundary layer with a saturation function that ensures asymptotic stability of the overall system

optimal designs for space time linear precoders and decoders we introduce a new paradigm for the design of transmitter space time coding that we refer to as linear precoding it leads to simple closed form solutions for transmission over frequency selective multiple input multiple output mimo channels which are scalable with respect to the number of antennas size of the coding block and transmit average peak power the scheme operates as a block transmission system in which vectors of symbols are encoded and modulated through a linear mapping operating jointly in the space and time dimension the specific designs target minimization of the symbol mean square error and the approximate maximization of the minimum distance between symbol hypotheses under average and peak power constraints the solutions are shown to convert the mimo channel with memory into a set of parallel flat fading subchannels regardless of the design criterion while appropriate power bits loading on the subchannels is the specific signature of the different designs the proposed designs are compared in terms of various performance measures such as information rate ber and symbol mean square error

robust tracking in nonlinear systems a nonlinear feedback multivariable controller is used to implement multivariable tracking in a nonlinear system the tracking error is measured by a general function of system state and the input command the controller is robust in the sense that the tracking error is ultimately bounded in the presence of modeling errors free parameters which affect the form of the controller allow flexibility in determining such factors as the size of the ultimate bound the rate of error decay excursion of the control conditions on the class of modeling errors and the level of system gain restrictive assumptions on the structure of the model and the modeling errors are required but they are treated in a transformation framework which allows the generalization of similar conditions which appear in the prior literature these assumptions hold for robotic manipulators this application is investigated at some length and it appears that the resulting control scheme may have advantages over others which have been proposed in the robotics literature

free vibration analysis of cylindrical tanks partially filled with liquid abstract a simple but effective modal solution based on the underlying ideas of the hierarchical finite element method is presented for evaluating the free vibration characteristics of vertical thin circular cylindrical shells partially or completely filled with liquid and subjected to any variationally consistent set of boundary conditions on the lower and upper boundaries effects of static liquid pressure in plane inertias and liquid free surface motions are taken into account the solution of the shell problem is obtained through a procedure in which sander s shell equations are transformed into a new system of first order ordinary differential equations which are solved by the galerkin error minimization procedure the system variables are those quantities which appear in the boundary conditions on a rotationally symmetric edge of a cylindrical shell the liquid is taken as non viscous and incompressible and the coupling between the deformable shell and this medium is taken into account the solution for the liquid velocity potential is assumed as a sum of two sets of linear combinations of suitable harmonic functions which satisfy laplace equation and the relevant boundary conditions this procedure leads to a determinantal equation for the determination of the shell and liquid natural frequencies and the associated mode shapes application of the method to a few selected cases and comparisons of the numerical results with those obtained by other theories and from experiments are found to be good and demonstrate the effectiveness and accuracy of the present methodology

globally stable robust tracking of nonlinear systems using variable structure control and with an application to a robotic manipulator the globally stable robust output tracking for a class of nonlinear systems is considered based only on the knowledge of the bounds on the uncertainties a variable structure control vsc law is developed under the structure matching assumption it is shown that the outputs of the closed loop system asymptotically track given output trajectories despite the uncertainties while maintaining the boundedness of all signals inside the loop all signals inside the loop are shown to be bounded for all time to illustrate the efficiency of the controller the approach is applied to the case of a two degree of freedom dof robotic manipulator with variable payload numerical simulation results are also provided

asymptotic stability for tracking control of nonlinear uncertain dynamical systems described by differential inclusions in this paper we will study the tracking control problem for nonlinear uncertain dynamical systems two generalized feedback control inputs have been proposed such that the feedback controlled systems satisfy the complete tracking control property with exponential asymptotic stability and the trajectories of the systems are steered to the pre specified observation map with an exponential convergence rate moreover an estimate of the tracking time of the trajectories attaining the observation map has also been given an example inspired from a guided missile problem illustrates the use of our main results

spatial modulation over partially coherent multiple input multiple output channels communication over multiple input multiple output mimo channels of arbitrary coherence is considered in light of a mean square estimation error msee criterion earlier work in the field has focused on fully coherent channels and determined that use of a singular value decomposition svd of the channel transfer function matrix can realize the capacity of the mimo channel more recently research has shown that the use of arbitrary orthonormal channel excitation vectors can maximize expected capacity over fully incoherent rayleigh fading mimo channels partially coherent channels have generally been examined only in terms of their degrading influence on capacity in this discussion channel excitation techniques are proposed that minimize an msee criterion over an ensemble of mimo channels of arbitrary coherence the algorithms rely on only the second and fourth order moments of the channel transfer function two experiments were conducted to examine the new strategies using measured mimo channel transfer function ensembles one from an underwater acoustic channel and others from rf wireless channels the performance of the strategies are compared the new techniques outperform orthonormal signaling based on sinr or capacity metrics while requiring substantially less channel feedback than needed by a channel decomposition approach

output tracking control of nonlinear systems with mismatched uncertainties abstract this paper addresses the output tracking problem of a class of nonlinear systems given input output linearizability of the class of nonlinear systems a robust output tracking controller derived via a lyapunov based approach is proposed here the model uncertainties do not need to satisfy the conventional matching condition but states and tracking error remain bounded furthermore the magnitude of the tracking error will bear dominant dependence on the magnitude of the mismatched uncertainties

a modified trellis coding technique for partial response channels the problem of trellis coding for multilevel baseband transmission over partial response channels with transfer polynomials of the form 1 or d sup n is addressed the novel method presented here accounts for the channel memory by using multidimensional signal sets and partitioning the signal set present at the noiseless channel output it is shown that this coding technique can be viewed as a generalization of a well known procedure for binary signaling the concatenation of convolutional codes and inner block codes that are tuned to the channel polynomial it results in high coding gains with moderate complexity if some bandwidth expansion is accepted

coset codes ii binary lattices and related codes for pt i see ibid vol 34 no 5 p 1123 51 1988 the family of barnes wall lattices including d sub 4 and e sub 8 of lengths n 2 sup n and their principal sublattices which are useful in constructing coset codes are generated by iteration of a simple construction called the squaring construction the closely related reed muller codes are generated by the same construction the principal properties of these codes and lattices are consequences of the general properties of iterated squaring constructions which also exhibit the interrelationships between codes and lattices of different lengths an extension called the cubing construction generates good codes and lattices of lengths n 3 2 sup n including the golay code and leech lattice with the use of special bases for 8 space another related construction generates the nordstrom robinson code and an analogous 16 dimensional nonlattice packing these constructions are represented by trellis diagrams that display their structure and interrelationships and that lead to efficient maximum likelihood decoding algorithms

optimized power allocation for packet retransmissions of non gaussian inputs through sequential awgn channels this work investigates the optimization of power allocation for hybrid arq h arq retransmissions of non gaussian inputs over a bank of independent parallel gaussian channels we establish a general solution for maximizing generic transceiver objective utility functions that are monotonically non decreasing and concave function with respect to the accumulated signal to noise ratio snr specifically we investigate optimized solutions under two performance metrics namely the mutual information mi and the union bound of symbol error rate ubser under maximal ratio combining mrc reception we establish that efficient utilization of parallel channels in h arq retransmissions requires sequential updating of signal channel pairing as well as optimizing power allocation applying geometric analysis of power loading for h arq retransmission we show that for i i d inputs that are not necessarily gaussian the optimum pairing policy should match signals of the lowest cumulative signal to noise ratio with channels of the best quality in each transmission which is consistent with a similar result of for gaussian input signals we further propose a generalized mercury waterfilling algorithm for the optimal power assignment problem in h arq simulation results illustrate substantial improvements over designs based on gaussian input assumptions

vector coding for partial response channels a linear technique for combining equalization and coset codes on partial response channels with additive white gaussian noise is developed the technique vector coding uses a set of transmit filters or vectors to partition the channel into an independent set of parallel intersymbol interference isi free channels for any given finite or infinite block length the optimal transmit vectors for such channel partitioning are shown to be the eigenvectors of the channel covariance matrix for the specified block length and the gains of the individual channels are the eigenvalues an optimal bit allocation and energy distribution are derived for the set of parallel channels under an accurate extension of the continuous approximation for power in optimal multidimensional signal sets for constellations with unequal signal spacing in different dimensions examples are presented that demonstrate performance advantages with respect to zero forcing decision feedback methods that use the same coset code on the same partial response channel only resampling the channel at an optimal rate and assuming no errors in the feedback path will bring the performance of the decision feedback methods up to the level of the vector coded system

a transformed lure problem for sliding mode control and chattering reduction the sliding mode control problem is investigated with the frequency domain approach the authors show that the sliding mode control can be transformed into a lure problem with this formulation it is shown that the conventional sliding mode control with a nonlinear sign function can only guarantee to make the overall system stable but not asymptotically stable the authors also consider a practical situation where the sign nonlinearity may contain a hysteresis loop for this situation they show that even if the hysteresis loop is very small there still exists a limit cycle however chattering phenomenon caused by the limit cycle behavior can be eliminated by a certain class of nonlinearities

perfect discrete multitone modulation with optimal transceivers previously discrete fourier transform dft based discrete multitone modulation dmt systems have been widely applied to various applications in this paper we study a broader class of dmt systems using more general unitary matrices instead of dft matrices for this class we show how to design optimal dmt systems over frequency selective channels with colored noise in addition asymptotical performance of dft based and optimal dmt systems are studied and shown to be equivalent however for a moderate number of bands the optimal dmt system offers significant gain over the dft based dmt system as is demonstrated by examples

computing the weight distribution of a set of points obtained by scaling shifting and truncating a lattice a method is developed to compute the weight distribution of a set of points obtained from a lattice the lattice is scaled with possibly nonequal factors along different dimensions is shifted to an arbitrary point and its lower dimensional subspaces are truncated within given shaping regions each branch in the lattice trellis diagram is labeled by the weight distribution of the corresponding coset incorporating the effects of scaling shifting and truncation the weight distribution is obtained by multiplying the weight distribution of the serial branches and then adding the result over parallel paths

multirate zero forcing tx rx design for mimo channel under ber constraints this paper is concerned with communicating parallel independent streams of data possibly of different rates through a multiple input multiple output channel each data stream is required to satisfy a bit error rate ber constraint this scenario arises in multimedia communications we find the linear zero forcing transmitter receiver tx rx matrix pair that requires the minimum transmitter power to achieve the ber constraints it is well known that the tx rx pair can be chosen to partition the matrix channel into scalar subchannels corresponding to singular values and different data streams can be transmitted through different subchannels this design is suboptimum in general the optimum design has the following structure the set of input data streams is partitioned into groups called signal groups the set of subchannels is conformably partitioned into subchannel groups each signal group is collectively transmitted through its assigned subchannel group with each signal subchannel group pair is associated a unitary matrix that mixes the signals at the transmitter and unmixes them at the receiver we derive a simple algorithm to determine the optimum signal and subchannel groups we then use a known algorithm from majorization theory to determine the unitary matrices using these we completely specify the optimum tx rx pair

rayleigh quotients for coupled free vibrations abstract based upon the general thin shell theory and basic equations in fluid mechanics three kinds of rayleigh s quotients for coupled fluid structure free vibrations are developed for arbitrary tanks fully or partially filled with i inviscid irrotational and incompressible fluid with the effects of free surface waves neglected ii inviscid irrotational and incompressible fluid with the effects of free surface waves considered and iii inviscid irrotational and compressible fluid respectively theorems concerning stationary values of the respective rayleigh quotients are proved by utilizing the generalized orthogonality relationships for the wet modes of these three kinds of liquid containing tank models thus the mathematical foundations for calculating approximately the eigenvalues and eigenvectors in fluid structure interaction systems are presented an example of applying the rayleigh quotient to predicting a natural frequency of a cylindrical tank partially filled with fluid is provided and the result is compared with that available

block transmission over dispersive channels transmit filter optimization and realization and mmse dfe receiver performance optimal transmit filters for packet based data transmission on dispersive gaussian noise linear time invariant channels are derived by maximizing the mutual information subject to a fixed input power budget a quasi stationary approximation to the optimal nonstationary input covariance process is derived and shown to exhibit negligible mutual information loss from the optimal case for situations of most practical interest moreover this quasi stationary approximation results in efficiently computed lattice or pole zero implementations of the transmit filter by considering the popular finite impulse response minimum mean square error decision feedback equalizer fir mmse dfe as a receiver structure we show that transmitter optimization results in an appreciable improvement in the decision point signal to noise ratio finally we show that as the output blocklength becomes infinite the optimum finite dimensional nonstationary input covariance process converges to a stationary process whose power spectrum obeys the well known water pouring distribution

global robust stabilization of nonlinear cascaded systems this paper gives a sufficient condition for a class of nonlinear cascaded systems to be globally stabilizable via state feedback in the presence of uncertainty which does not necessarily satisfy the so called matching condition the authors result is an extension of the former stabilization results which treated systems without uncertainty in the sense that the uncertainty is taken into account

non linear dynamics and stability of circular cylindrical shells containing flowing fluid part i stability abstract the study presented is an investigation of the non linear dynamics and stability of simply supported circular cylindrical shells containing inviscid incompressible fluid flow non linearities due to large amplitude shell motion are considered by using the non linear donnell s shallow shell theory with account taken of the effect of viscous structural damping linear potential flow theory is applied to describe the fluid structure interaction the system is discretiszd by galerkin s method and is investigated by using a model involving seven degrees of freedom allowing for travelling wave response of the shell and shell axisymmetric contraction two different boundary conditions are applied to the fluid flow beyond the shell corresponding to i infinite baffles rigid extensions of the shell and ii connection with a flexible wall of infinite extent in the longitudinal direction permitting solution by separation of variables they give two different kinds of dynamical behaviour of the system as a consequence of the fact that axisymmetric contraction responsible for the softening non linear dynamical behaviour of shells is not allowed if the fluid flow beyond the shell is constrained by rigid baffles results show that the system loses stability by divergence

dynamic responses of reissner mindlin plates with free edges resting on tensionless elastic foundations abstract dynamic response analysis is presented for a reissner mindlin plate with four free edges resting on a tensionless elastic foundation of the winkler type and pasternak type the mechanical loads consist of transverse partially distributed impulsive loads and in plane static edge loads while the temperature field is assumed to exhibit a linear variation through the thickness of the plate the material properties are assumed to be independent of temperature the two cases of initially compressed plates and of initially heated plates are considered the formulations are based on reissner mindlin first order shear deformation plate theory and include the plate foundation interaction and thermal effects a set of admissible functions is developed for the dynamic response analysis of moderately thick plates with four free edges the galerkin method the gauss legendre quadrature procedure and the runge kutta technique are employed in conjunction with this set of admissible functions to determine the deflection time and bending moment time curves as well as shape mode curves an iterative scheme is developed to obtain numerical results without using any assumption on the shape of the contact region the numerical illustrations concern moderately thick plates with four free edges resting on tensionless elastic foundations of the winkler type and pasternak type from which results for conventional elastic foundations are obtained as comparators the results confirm that the plate will have stronger dynamic behavior than its counterpart when it is supported by a tensionless elastic foundation

a unifying design of sliding mode and classical controllers a theory is given to unify output sliding mode control and classical control the idea is based on defining the sliding variable in such a way that once the system begins to slide the classical controller transfer function is realized this idea leads to the development of a hybrid sliding and classical controller which retains the merits of both types of controllers but eliminates their respective limitations the proposed method is robust and applies to non minimum phase single input single output siso systems no state measurement is required

orthogonality of wet modes in coupled vibrations of cylindrical shells containing liquids abstract on the basis of flugge s thin shell equations and a linear potential flow theory general orthogonality relations of wet modes for cylindrical storage vessels containing liquids are established some applications of these relations to dynamic response analysis under arbitrary excitation are also discussed

trellis coding for partial response channels we consider trellis coding techniques for improving the reliability of digital transmission over noisy partial response channels such channels are commonly encountered in digital communication systems and also play a role in devices for data recording concentrating on the channels with characteristics 1 mp d we study methods to obtain codes which increase free euclidean distance between permitted sequences of channel outputs and avoid the occurrence of unlimited runs of identical outputs at the expense of some loss in data rate one technique employs the concept of set partitioning the other is based on using convolutional codes designed for maximum free hamming distance in conjunction with a precoder both methods lead to essentially equivalent codes

optimization of signal sets for partial response channels ii asymptotic coding gain for pt i see ibid vol 37 no 5 p 1327 141 1991 for a linear time invariant discrete time channel with a given transfer function h f and information rate r bits t where t is the symbol interval an optimal signal set of length k is defined to be a set of 2 sup rk inputs of length k that maximizes the minimum l sub 2 distance between pairs of outputs the author studies the minimum distance between outputs or equivalently the coding gain of optimal signal sets as k to infinity he shows how to estimate the coding gain relative to single step detection of an optimal signal set length k when k is large

a hydroelasticity method for vibrating structures containing and or submerged in flowing fluid this paper presents a method for investigating the dynamics of elastic structures containing and or submerged in flowing fluid the method presented is based on a boundary integral equation method in conjunction with the method of images in order to impose appropriate boundary condition on the fluid s free surface the method of analysis can be applied to any shape of cylindrical structure partially in contact with flowing fluid in the analysis of the linear fluid structure system it is assumed that the fluid is ideal i e inviscid incompressible and its motion is irrotational it is assumed that the flexible structure vibrates in its in vacuo eigenmodes when it is in contact with flowing fluid and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure the in vacuo dynamic properties of the dry structure are obtained by using a standard finite element software in the wet part of the analysis the wetted surface is idealized by using appropriate boundary elements referred to as hydrodynamic panels the fluid structure interaction effects are calculated in terms of the generalized added mass coefficients generalized coriolis fluid force coefficients and generalized centrifugal fluid force coefficients in order to demonstrate the applicability of the proposed method a circular cylindrical shell simply supported at both ends was adopted for the calculations the cylindrical shell was considered separately with rigid and flexible extensions at its ends to assess the influence of flowing fluid on the dynamic behavior of the shell structure the non dimensional eigenfrequencies and associated eigenmodes are presented as a function of the non dimensional fluid velocity the predictions compare well with available analytical calculations found in the literature

hydroelastic analysis of fluid storage tanks by using a boundary integral equation method abstract this paper presents a boundary integral equation method in conjunction with the method of images in order to investigate the dynamic behaviour wet frequencies and associated mode shapes of fluid containing structures in the analysis of the linear fluid structure system it is assumed that the fluid is ideal and fluid forces are associated with inertial effects of the contained fluid this implies that the fluid pressure on the wetted surface of the structure is in phase with the structural acceleration the in vacuo dynamic properties of the dry structure are obtained by using standard finite element software in the wet part of the analysis the fluid structure interaction effects are calculated in terms of the generalized added mass coefficients by use of the boundary integral equation method together with the method of images in order to impose the 0 boundary condition on the free surface in this study three different test cases are considered i a clamped free cylindrical tank with a rigid bottom ii a flexible circular plate in a rigid cylindrical tank and iii a flexible cylindrical shell with flexible end plates hermetic can the fluid storage tanks in this investigation are assumed partially or completely filled with water to assess the influence of the contained fluid on the dynamic characteristics the wet natural frequencies and associated mode shapes are calculated the predictions compare well with available experimental and numerical data

robust stabilization of mimo nonlinear time varying mismatched uncertain systems abstract this paper considers the problem of robust stabilization of multi input multi output mimo nonlinear systems in the presence of mismatched time varying uncertainties combining the differential geometric feedback linearization with the deterministic approach it derives two robust stabilizing controllers i e the high gain feedback controller and the variable structure controller these two controllers only require the knowledge of the nominal system and the bounds of the uncertainties therefore they are more feasible to be implemented both controllers reduce the effects of arbitrarily large bounded mismatched uncertainties successfully to achieve uniform ultimate boundedness stabilization of the mimo nonlinear timevarying uncertain systems

multidimensional signal sets through the shell construction for parallel channels the authors derive a procedure to send r bits on m parallel channels a decomposition of the best constellation in z sup m 1 2 1 2 is given in terms of the cross products of lower dimensional shells of points the proposed scheme can be used with good known coset codes to provide an alternate method of coded modulation the results indicate that one can get good shaping gains for low encoder complexity the method is also generalized for channels with unequal gains the authors also find a significant performance advantage at fixed shaping gain in certain cases with respect to the recent voronoi constellations in terms of peak to average power and constellation expansion

robust control of cascaded and individually feedback linearizable nonlinear systems abstract feedback linearization technique is applied to design robust controllers for a class of nonlinear uncertain systems every system in the class is a series connection of finite number of nonlinear subsystems which are individually feedback linearizable and have significant but matched nonlinear functional uncertainties the key difference between this work and existing robust results is that the matching conditions and the existence of feedback linearization transformation are only required individually for each subsystem a constructive robust control design procedure is proposed for the unique control in the overall system the procedure is conceptually simple and contains three steps first perform input output feedback linearization for all individual subsystems second design fictitious robust controllers for inputs of each subsystem as if the subsystem had an independent control finally a mapping is developed which maps the individual fictitious controls recursively into the unique control of the overall system since neither the matching conditions nor feedback linearization are required for the overall system this becomes the broadest class of nonlinear uncertain or known systems for which a robust regular tracking control can be constructed using feedback linearization method global stability of the overall system is always guaranteed

guard sequence optimization for block transmission over linear frequency selective channels we show that the optimum length spl nu guard sequence for block transmission over a linear gaussian noise dispersive channel with memory spl nu is a linear combination of the n information symbols of the block a closed form expression for the optimum guard sequence is derived subject to a total average energy constraint on the information and guard symbols the achievable channel block throughput with the optimum guard sequence is compared with that achievable with two common guard sequence types namely zero stuffing and cyclic prefix

learning variable structure control approaches for repeatable tracking control tasks for the finite period tracking control task repeatable over iterations uniformly bounded learning control is synthesized into variable structure control to approximate the equivalent control and to realize perfect tracking

block based eigensystem of the 1 spl plusmn d and 1 d sup 2 partial response channels we find analytical expressions for the block based input and output eigenvectors and eigenvalues of the systems with responses 1 spl plusmn d and 1 d sup 2 the input eigenvectors form an orthonormal basis which is the optimum modulator for a channel with that transfer function the output eigenvectors form an orthonormal basis with the same spectral nulls as the corresponding system this basis can be used to produce line codes with spectral nulls the eigenvectors are sinusoids this reduces the computational complexity by allowing for fast transform algorithms to perform the modulation for a block of data

mmse decision feedback equalizers and coding ii coding results for pt i see ibid vol 43 no 10 p 2582 1995 the minimum mean squared error decision feedback equalizer mmse dfe has properties that suggest that it is a canonical equalization structure in systems that combine equalization with coded modulation with a given symbol rate 1 t and transmit spectrum the output signal to noise ratio snr sub mmse dfe u of a mmse dfe with an unbiased decision rule is a single parameter that characterizes the channel for coding purposes indeed the transmit spectrum that maximizes snr sub mmse dfe u is the capacity achieving water pouring spectrum and the capacity c t in bits per two dimensions is given by c t log sub 2 1 snr sub mmse dfe u regardless of the channel characteristics the performance of a coded system with a mmse dfe equalization structure may be accurately estimated using the gain of the coding scheme at a given pr e this performance is shown to be approximately the same as that of a multicarrier system using the same transmit spectrum and similar coding such systems are known to be able to approach capacity arbitrarily closely the mmse dfe can perform significantly better than a zero forcing decision feedback equalizer particularly at moderate to low snr s and on severe isi channels simulation results indicate that performance of the mmse dfe is surprisingly insensitive to transmit spectral shaping as long as the transmit spectrum exceeds the capacity achieving band but that there is an optimal symbol rate that should approximately be used

capacity analysis of index modulations over spatial polarization and frequency dimensions determining the capacity of a modulation scheme is a fundamental topic of interest index modulations im such as spatial modulation smod polarized modulation pmod or frequency index modulation fmod are widely studied in the literature however finding a closed form analytical expression for their capacity still remains an open topic in this paper we formulate closed form expressions for the instantaneous capacity of im together with its second and fourth order approximations we show that in average the second approximation error tends to zero for low signal to noise ratio snr and is o left textrm snr right also a detailed analysis of the ergodic capacity over rayleigh rice and nakagami m channel distributions is provided as application of the capacity analysis we leverage the proposed expressions to compute the ergodic capacities of smod for different antenna configuration and correlations pmod for different channel components and conditions and fmod for different frequency separations

a dual reciprocity boundary element solution method for the free vibration analysis of fluid coupled kirchhoff plates abstract a boundary element solution method is proposed for linear vibration analysis of fluid coupled thin plates the method is based on replacing the associated biharmonic operator with two successive harmonic operators leading to a coupled system of boundary integral equations with simpler properties the fundamental solution has an elementary form and complicated singularity removal techniques can be avoided the fluid flow due to the plate motion is taken as a potential field and its effect on the plate dynamics is incorporated into the analysis by invoking another boundary integral solution described over the fluid plate interface the body terms in the plate boundary integral equations are considered by the dual reciprocity boundary element formulation three different radial basis functions are employed as interpolation functions alone and augmented with polynomial and sine expansions to represent the body terms the performance of the method is investigated from several perspectives by adopting plates with different shapes and or boundary conditions excellent approximations are obtained in general the convergence behavior is consistent both dry and wet frequency parameters are predicted accurately and the mode shapes are captured even with rough models in some of the studied problems however deviated results are obtained for specific modes furthermore it is observed that the performance of the method depends on the implemented drm functions and combining radial basis functions with global expansions does not yield noticeable improvements

new precoding for intersymbol interference cancellation using nonmaximally decimated multirate filterbanks with ideal fir equalizers in this paper we propose a new precoding method for intersymbol interference isi cancellation by using non maximally decimated multirate filterbanks unlike the existing preceding methods such as the th and trellis precodings the new preceding i may be independent of the isi channel ii is linear and does not have to implement any modulo operation iii gives the ideal fir equalization at the receiver for any fir isi channel including spectral null channels iv expands the transmission bandwidth in a minimum amount the precoding is built on non maximally decimated multirate filterbanks based on multirate filterbank theory we present a necessary and sufficient condition on an fir isi transfer function in terms of its zero set such that there is a linear fir n spl times m precoder so that an ideal fir equalizer exists where the integers k and n are arbitrarily fixed the condition is easy to check as a consequence of the condition for any given fir isi transfer function not identically 0 there always exist such linear fir precoders moreover for almost all given fir isi transfer functions there exist linear fir precoders with size n spl times n 1 i e the bandwidth is expanded by 1 n in addition to the conditions on the isi transfer functions a method for the design of the linear fir precoders and the ideal fir equalizers is also given numerical examples are presented to illustrate the theory

nonlinear dynamics of harmonically excited circular cylindrical shells containing fluid flow abstract in the present study the geometrically nonlinear vibrations of circular cylindrical shells subjected to internal fluid flow and to a radial harmonic excitation in the spectral neighbourhood of one of the lowest frequency modes are investigated for different flow velocities the shell is modelled by donnell s nonlinear shell theory retaining in plane inertia and geometric imperfections the fluid is modelled as a potential flow with the addition of unsteady viscous terms obtained by using the time averaged navier stokes equations a harmonic concentrated force is applied at mid length of the shell acting in the radial direction the shell is considered to be immersed in an external confined quiescent liquid and to contain a fluid flow in order to reproduce conditions in previous water tunnel experiments for the same reason complex boundary conditions are applied at the shell ends simulating conditions intermediate between clamped and simply supported ends numerical results obtained by using pseudo arclength continuation methods and bifurcation analysis show the nonlinear response at different flow velocities for i a fixed excitation amplitude and variable excitation frequency and ii fixed excitation frequency by varying the excitation amplitude bifurcation diagrams of poincare maps obtained from direct time integration are presented as well as the maximum lyapunov exponent in order to classify the system dynamics in particular periodic quasi periodic sub harmonic and chaotic responses have been detected the full spectrum of the lyapunov exponents and the lyapunov dimension have been calculated for the chaotic response they reveal the occurrence of large dimension hyperchaos

hydroelastic vibration of a circular plate submerged in a bounded compressible fluid abstract an analytical method for the linear free vibration of a circular plate submerged in a fluid was developed by the rayleigh ritz method based on the fourier bessel series expansion it is assumed that the plate is clamped at an offcenter location of a rigid cylindrical container and the fluid bisected by the plate in the container is non viscous and compressible since a combination of the dry modal functions of the circular plate can approximate the wet vibration modes the functions were used to form a set of linearly independent functions of the rayleigh ritz method it was found that the theoretical results could predict well the fluid coupled natural frequencies with excellent accuracy compared with the finite element analysis results the effects of the fluid compressibility and the offcenter distance on the natural frequencies were also observed

continuous state feedback guaranteeing uniform ultimate boundedness for uncertain dynamic systems we consider a dynamic system containing uncertain elements only the set of possible values of these uncertainties is known based on this information a class of state feedback controls is proposed in order to guarantee uniform ultimate boundedness of every system response within an arbitrarily small neighborhood of the zero state these feedback controls are continuous functions of the state

dynamics of a rectangular plate resting on an elastic foundation and partially in contact with a quiescent fluid abstract in this study a method of analysis is presented for investigating the effects of elastic foundation and fluid on the dynamic response characteristics natural frequencies and associated mode shapes of rectangular kirchhoff plates for the interaction of the kirchhoff plate pasternak foundation a mixed type finite element formulation is employed by using the g teaux differential the plate finite element adopted in this study is quadrilateral and isoparametric having four corner nodes and at each node four degrees of freedom are present one transverse displacement two bending moments and one torsional moment therefore a total number of 16 degrees of freedom are assigned to each element a consistent mass formulation is used for the eigenvalue solution in the mixed finite element analysis the plate structure considered is assumed clamped or simply supported along its edges and resting on a pasternak foundation furthermore the plate is fully or partially in contact with fresh water on its one side for the calculation of the fluid structure interaction effects generalized fluid structure interaction forces a boundary element method is adopted together with the method of images in order to impose an appropriate boundary condition on the fluid s free surface it is assumed that the fluid is ideal i e inviscid incompressible and its motion is irrotational it is also assumed that the plate elastic foundation system vibrates in its in vacuo eigenmodes when it is in contact with fluid and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure at the fluid structure interface continuity considerations require that the normal velocity of the fluid is equal to that of the structure the normal velocities on the wetted surface of the structure are expressed in terms of the modal structural displacements obtained from the finite element analysis by using the boundary integral equation method the fluid pressure is eliminated from the problem and the fluid structure interaction forces are calculated in terms of the generalized hydrodynamic added mass coefficients due to the inertial effect of fluid to asses the influences of the elastic foundation and fluid on the dynamic behavior of the plate structure the natural frequencies and associated mode shapes are presented furthermore the influence of the submerging depth on the dynamic behavior is also investigated

finite element analysis of the vibratory characteristics of cylindrical shells conveying fluid a finite element formulation is developed to predict the vibration of cylindrical shells conveying fluid the method is based on the three dimensional theory of elasticity and the linearised eulerian equations the hydrodynamic pressure is derived from the condition for dynamic coupling of the fluid structure and the eulerian equation the influence of initial stresses within the shell due to fluid pressure is taken into account predicted natural frequencies for fluid shell systems in the radius to thickness ratio range of r h 38 96 1624 are compared with published experimental results to validate the model and are also compared with results obtained using other finite element models based on the classical shell theory and potential flow theory to demonstrate advantages and disadvantages in terms of accuracy the effect of variation in flow velocities and hydrostatic pressures on the dynamic behaviour of fluid conveying shells is examined and the influence of supported conditions on the free vibration is also discussed

residue division multiplexing for discrete time signals multiplexing is a technique for dividing a single transmission channel into a number of virtual subchannels the present paper introduces a new multiplexing system for discrete time signals based on a polynomial factorization in this multiplexing system a linear filter additive noise channel is decomposed into independent subchannels that are also modeled as linear filter additive noise channels a configuration and an analysis of the multiplexing system as applied to mobile communications are described in detail based on a specific selection of polynomial factorization multicarrier code division multiple access mc cdma is receiving much attention in the field of mobile communications because of its time and frequency diversity property as is the case with mc cdma in the proposed multiplexing system the subchannel information is dispersed uniformly in both frequency and time so that degradation localized in frequency or time average out over the subchannels the averaging has the effect of decreasing the total error probability of transmission unlike mc cdma however the multiplexing system creates multiple carriers simply by up sampling a single complex sinusoidal carrier for each subchannel user because of the simple mechanism the implementation cost is less than that of mc cdma

trellis coded modulation with multidimensional constellations trellis coded modulation schemes using four eight or 16 dimensional constellations have a number of potential advantages over the usual two dimensional schemes a smaller constituent two dimensional constellation easier tolerance to phase ambiguities and a better trade off between complexity and coding gain a number of such schemes are presented and evaluated starting with a variety of multidimensional lattices we show how to select multidimensional constellations how to partition them into subsets how to construct trellis codes using those subsets and how to map hits to constellation points simplifications of the viterbi decoding algorithm are presented we conclude that there are multidimensional trellis coded modulation schemes that perform better for the same complexity than do two dimensional schemes

free vibration of a partially liquid filled and submerged horizontal cylindrical shell abstract the dynamic characteristics i e natural frequencies and mode shapes of a partially filled and or submerged horizontal cylindrical shell are examined in this investigation it is assumed that the fluid is ideal and fluid forces are associated with inertial effects only namely the fluid pressure on the wetted surface of the structure is in phase with the structural acceleration the in vacuo dynamic characteristics of the cylindrical shell are obtained using standard finite element software in the wet part of the analysis it is assumed that the shell structure preserves its in vacuo mode shapes when in contact with the contained and or surrounding fluid and that each mode shape gives rise to a corresponding surface pressure distribution of the shell the fluid structure interaction effects are calculated in terms of generalized added masses using a boundary integral equation method together with the method of images in order to impose an appropriate boundary condition on the free surface to assess the influence of the contained and or surrounding fluid on the dynamic behaviour of the shell structure the wet natural frequencies and associated mode shapes were calculated and compared with available experimental measurements

sum capacity of gaussian vector broadcast channels this paper characterizes the sum capacity of a class of potentially nondegraded gaussian vector broadcast channels where a single transmitter with multiple transmit terminals sends independent information to multiple receivers coordination is allowed among the transmit terminals but not among the receive terminals the sum capacity is shown to be a saddle point of a gaussian mutual information game where a signal player chooses a transmit covariance matrix to maximize the mutual information and a fictitious noise player chooses a noise correlation to minimize the mutual information the sum capacity is achieved using a precoding strategy for gaussian channels with additive side information noncausally known at the transmitter the optimal precoding structure is shown to correspond to a decision feedback equalizer that decomposes the broadcast channel into a series of single user channels with interference pre subtracted at the transmitter

linearized formulation for fluid structure interaction application to the linear dynamic response of a pressurized elastic structure containing a fluid with a free surface abstract to control the linear vibrations of structures partially filled with liquids is of prime importance in various industries such as aerospace naval civil and nuclear engineering it is proposed here to investigate a linearized formulation adapted to a rational computation of the vibrations of such coupled systems its particularity is to be fully lagrangian since it considers the fluid displacement field with respect to a static equilibrium configuration as the natural variable describing the fluid motion as classically done in structural dynamics as the coupled system considered here is weakly damped in the low frequency domain low modal density the analysis of the vibrations of the associated undamped conservative system constitutes the main objective of this paper one originality of the present formulation is to take into account the effect of the pressurization of the tank on the dynamics of the system particularly in the case of a compressible liquid we propose here a new way of deriving the linearized equations of the coupled problem involving a deformable structure and an inner inviscid liquid with a free surface a review of the classical case considering a heavy incompressible liquid is followed by an application to the new case involving a light compressible liquid a solution procedure in the frequency domain is proposed and a numerical discretization using the finite element method is discussed in order to reduce the computational costs an appropriate reduced order matrix model using modal synthesis approach is also presented

optimization of a lattice based constellation for signaling over a partial response channel this article discusses the problem of optimizing a lattice based signal constellation for signaling over a partial response channel the objective is to minimize the probability of error which is determined by the combined effects of the additive gaussian noise and channel memory

lower bound on the ber of a pre and postequalized vector communication system this paper is concerned with communication over a multiple input multiple output channel in the first reference a lower bound on the bit error rate of a pre and postequalized communication system was derived for uniform bit loading here we extend the lower bound to nonuniform bit loading the lower bound applies to communication systems for which 1 the cascade of the pre equalizer noise free channel and postequalizer is a diagonal matrix a generalized zero forcing condition satisfied by many designs in the literature and 2 the encoding modulation decoding demodulation is done independently over the dimensions of the pre equalizer input postequalizer output the lower bound is stated as a function of the bit loading channel and transmitter power only and applies to uncoded as well as coset coded systems toward deriving the lower bound we minimize a weighted average of the noise variances at the postequalizer output

new trellis codes based on lattices and cosets a new technique is proposed for constructing trellis codes which provides an alternative to ungerboeck s method of set partitioning the new codes use a signal constellation consisting of points from an n dimensional lattice lambda with an equal number of points from each coset of a sublattice lambda one part of the input stream drives a generalized convolutional code whose outputs are cosets of lambda while the other part selects points from these cosets several of the new codes are better than those previously known

discrete multiple tone modulation with coset coding for the spectrally shaped channel a discrete approach to multiple tone modulation is developed for digital communication channels with arbitrary intersymbol interference isi and additive gaussian noise multiple tone modulation is achieved through the concatenation of a finite block length modulator based on discrete fourier transform dft code vectors and high gain coset or trellis codes symbol blocks from an inverse dft idft are cyclically extended to generate isi free channel output symbols that decompose the channel into a group of orthogonal and independent parallel subchannels asymptotic performance of this system is derived and examples of asymptotic and finite block length coding gain performance for several channels are evaluated at different values of bits per sample this discrete multiple tone technique is linear in both the modulation and the demodulation and is free from the effects of error propagation that often afflict systems employing bandwidth optimized decision feedback plus coset codes

filterbank transceivers optimizing information rate in block transmissions over dispersive channels optimal finite impulse response fir transmit and receive filterbanks are derived for block based data transmissions over frequency selective additive gaussian noise agn channels by maximizing mutual information subject to a fixed transmit power constraint both fir and pole zero channels are considered the inherent flexibility of the proposed transceivers is exploited to derive as special cases zero forcing zf and minimum mean square error receive filterbanks the transmit filterbank converts transmission over a frequency selective fading channel affected by additive colored noise into a set of independent flat fading subchannels with uncorrelated noise samples two loading algorithms are also developed to distribute transmit power and number of bits across the usable subchannels while adhering to an upper bound on the bit error rate ber reduction of the signal to noise ratio snr margin required to satisfy the prescribed ber is achieved by coding each subchannel s bit stream the potential of the proposed transceivers is illustrated and compared to discrete multitone dmt with simulated examples

a technique for the systematic choice of admissible functions in the rayleigh ritz method abstract a simple and systematic choice of admissible functions which are the eigenfunctions of the closest simple problem extracted from the one considered is proposed the extracted problem must be less constrained than the original one in other words it must be a problem where some constraints or other complications e g added masses are eliminated elastic constraints replace the eliminated rigid ones the convergence is also analyzed this approach has practical applications when it is possible to extract a problem with eigenfunctions expressed in closed form it also allows a very simple calculation of the potential energy of the system solutions for several cases involving beams are given in order to show the power of the method application of the method to circular plates and shells is also addressed

design of block transceivers with decision feedback detection this paper presents a method for jointly designing the transmitter receiver pair in a block by block communication system that employs intrablock decision feedback detection we provide closed form expressions for transmitter receiver pairs that simultaneously minimize the arithmetic mean squared error mse at the decision point assuming perfect feedback the geometric mse and the bit error rate of a uniformly bit loaded system at moderate to high signal to noise ratios separate expressions apply for the zero forcing and minimum mse mmse decision feedback structures in the mmse case the proposed design also maximizes the gaussian mutual information and suggests that one can approach the capacity of the block transmission system using independent instances of the same gaussian code for each element of the block our simulation studies indicate that the proposed transceivers perform significantly better than standard transceivers and that they retain their performance advantages in the presence of error propagation

hydroelastic vibration of two identical rectangular plates a theoretical study is presented on the hydroelastic vibration of two identical rectangular plates coupled with a bounded fluid it is assumed that the plates are clamped along the plate edges and an ideal fluid is surrounded by the two rectangular plates and a rigid rectangular container the velocity potential satisfying the fluid boundary conditions is expanded in terms of a finite fourier series and the modal displacements of the plates are also expanded by the finite fourier series for the compatibility requirement along the contacting surface between the plates and the fluid two transverse vibration modes in phase and out of phase are observed in the symmetric fluid coupled structure each in phase mode is assumed as a combination of the beam modes in air but every out of phase mode is assumed as a combination of polynomials satisfying the plate boundary condition and fluid volume conservation the coupled natural frequencies are obtained from the relationship between the reference kinetic energy of the structure including the fluid and the maximum strain energy of the two plates the proposed analytical method was found to be in good agreement with the results of a three dimensional finite element analysis

a hydroelastic investigation of circular cylindrical shells containing flowing fluid with different end conditions abstract this paper presents the effects of different end conditions on the response behavior of thin circular cylindrical shell structures fully in contact with flowing fluid the investigated end conditions are as follows simply supported clamped clamped clamped simply supported and clamped free cantilever shell ends additionally the dynamic responses of a tapered cylindrical shell conveying flowing fluid and simply supported at its ends were investigated the method employed in this study is a hybrid method a boundary integral equation method for the calculation of the fluid structure interaction effects and a finite element method for the structural analysis in this study the mathematical model presented before b ugurlu a ergin a hydroelasticity method for vibrating structures containing and or submerged in flowing fluid journal of sound and vibration 290 2006 572 596 is extended by applying the direct boundary integral equation method and by using a higher order panel method linear distribution it should also be said that the method used in this study could be applied to any shape of cylindrical structure in contact with internal and or external flowing fluid in contrast to the studies found in the literature in the analysis of the linear fluid structure system it is assumed that the fluid is ideal i e inviscid incompressible and its motion is irrotational it is assumed that the flexible structure vibrates in its in vacuo modes when it is in contact with flowing fluid and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure the in vacuo dynamic properties of the dry structure are obtained by using a standard finite element software in the wet part of the analysis the wetted surface is idealized by using appropriate boundary elements referred to as hydrodynamic panels the fluid structure interaction forces are calculated in terms of the generalized added mass coefficients generalized coriolis fluid force coefficients and generalized centrifugal fluid force coefficients to demonstrate the applicability of the method and assess the influences of the flowing fluid and end support conditions on the dynamic response behavior of the shell structures the non dimensional eigenfrequencies and associated eigenmodes are presented as a function of the non dimensional axial flow velocity and they compare well with the analytical solutions found in the literature

capacity penalty due to ideal zero forcing decision feedback equalization we consider the capacity c of a continuous time channel with frequency response h f and additive white gaussian noise if h f sup 2 behaves like a polynomial of order spl rho at high frequencies we show that the per symbol capacity approaches spl rho 2 nats per channel use at high signal powers if the receiver uses an ideal zero forcing decision feedback equalizer dfe consisting of a sampled whitened matched filter followed by a zero forcing tail canceler that is free of error propagation the overall system is free of intersymbol interference and has a well defined capacity c sub zf by comparing this capacity with the capacity c of the underlying channel we quantify the loss of information inherent in the tail canceling operation that typifies zero forcing dfe and zero forcing precoding systems for strictly bandlimited channels we find that the capacity penalty approaches zero in the limit of large signal power on the other hand for nonstrictly bandlimited channels the asymptotic penalty is nonzero however with bandwidth optimization the asymptotic penalty is at most 0 59 db and the asymptotic ratio c sub zf c is at least 93 6 depending on the asymptotic order spl rho of the channel response

optimization of signal sets for partial response channels i numerical techniques given a linear time invariant discrete time channel the problem of constructing n input signals of finite length k that maximize minimum l sub 2 distance between pairs of outputs is considered two constraints on the input signals are considered a power constraint on each of the n inputs hard constraint and an average power constraint over the entire set of inputs soft constraint the hard constraint problem is equivalent to packing n points in an ellipsoid in min k n 1 dimensions to maximize the minimum euclidean distance between pairs of points gradient based numerical algorithms and a constructive technique based on dense lattices are used to find locally optimal solutions to the preceding signal design problems two numerical examples are shown for which the average spectrum of an optimized signal set resembles the water pouring spectrum that achieves shannon capacity assuming additive white gaussian noise

three dimensional vibration analysis of rectangular thick plates on pasternak foundation the free vibration characteristics of rectangular thick plates resting on elastic foundations have been studied based on the three dimensional linear and small strain elasticity theory the foundation is described by the pasternak two parameter model the ritz method is used to derive the eigenvalue equation of the rectangular plate by augmenting the strain energy of the plate with the potential energy of the elastic foundation the chebyshev polynomials multiplied by a boundary function are selected as the admissible functions of the displacement functions in each direction the approach is suitable for rectangular plates with arbitrary boundary conditions convergence and comparison studies have been performed on square plates on elastic foundations with different boundary conditions it is shown that the present method has a rapid convergent rate stable numerical operation and very high accuracy parametric investigations on the dynamic behaviour of clamped square thick plates on elastic foundations have been carried out in detail with respect to different thickness span ratios and foundation parameters some results found for the first time have been given and some important conclusions have been drawn

on the number of points on shells for shifted z sup 4 sup n lattices a conjecture is proven on the number of points on shells for the shifted z sup 4 and the shifted z sup 8 lattices furthermore the results are extended to any shifted z sup 4 sup n lattice n 0 1 these results provide an easy way to compute the number of points on shells for the type of lattices used in the design of multidimensional signal sets or in vector coding

coset codes for partial response channels or coset codes with spectral nulls known coset codes are adapted for use on partial response channels or to generate signals with spectral nulls by using coset precoding and running digital sum feedback any desired tradeoff can be achieved between the power and spectra of the relevant sequences up to the optimum tradeoff possible a fundamental theorem specifying this optimum tradeoff is given a maximum likelihood sequence estimation mlse decoder for the original code may be used for the adapted code and such a decoder then attains the minimum squared distance of the original code these methods sometimes generate codes with greater minimum squared distance than that of the original code this distance can be attained by augmented decoders although such decoders inherently require long decoding delays and may be subjected to quasi catastrophic error propagation the authors conclude that at least for sequences supporting large numbers of bits per symbol coset codes can be adapted to achieve effectively the same performance and complexity on partial response channels or for sequences with spectral nulls as they do in the ordinary memoryless case

eigenvalue problems for vibrating structures coupled with quiescent fluids with free surface abstract vibrations of plates shells and plate shell systems coupled with sloshing quiescent and inviscid fluid have been advantageously studied by inserting the sloshing condition into the eigenvalue problem here a formulation of this particular eigenvalue problem for symmetric matrices is obtained in fact in the previous studies this technique has given eigenvalue problems for non symmetric matrices for which the problem of the existence of complex eigenvalues arises the present analysis deals with compressible and incompressible fluids and the discretization of the system is obtained by using the rayleigh ritz method the rayleigh quotient of the system is manipulated to obtain expressions suitable for symmetric formulations of the eigenvalue problem in particular the rayleigh quotient is transformed into a simpler expression where the potential energies of the compressible fluid and free surface waves do not appear the method is applied to a vertical simply supported circular cylindrical shell partially filled by an incompressible sloshing liquid a case with large interaction between sloshing and bulging modes is considered and interesting phenomena are observed

channel coding with multilevel phase signals a coding technique is described which improves error performance of synchronous data links without sacrificing data rate or requiring more bandwidth this is achieved by channel coding with expanded sets of multilevel phase signals in a manner which increases free euclidean distance soft maximum likelihood ml decoding using the viterbi algorithm is assumed following a discussion of channel capacity simple hand designed trellis codes are presented for 8 phase shift keying psk and 16 quadrature amplitude shift keying qask modulation these simple codes achieve coding gains in the order of 3 4 db it is then shown that the codes can be interpreted as binary convolutional codes with a mapping of coded bits into channel signals which we call mapping by set partitioning based on a new distance measure between binary code sequences which efficiently lower bounds the euclidean distance between the corresponding channel signal sequences a search procedure for more powerful codes is developed codes with coding gains up to 6 db are obtained for a variety of multilevel phase modulation schemes simulation results are presented and an example of carrier phase tracking is discussed

coupled vibrations of cantilever cylindrical shells partially submerged in fluids with continuous simply connected and non convex domain abstract the approach developed in the present paper is applied for the coupled vibration analysis of a cantilever cylindrical shell partially submerged in a fluid with a continuous simply connected and non convex domain the shell is partially and concentrically submerged in a rigid cylindrical container partially filled by a fluid which is assumed to be incompressible and inviscid the velocity potential for fluid motion is formulated in terms of eigenfunction expansions using the collocation method the interaction between the fluid and the structure takes into account by using the compatibility requirement along the wet surface of the shell and the rayleigh ritz method is used to calculate natural frequencies and modes of the coupled system the validity of the developed theoretical method is verified by comparing the results with those obtained from the finite element analysis furthermore the effects of submergence depth radial distance between shell and container and circumferential wavenumbers on the natural frequencies and modes of the coupled system are investigated

coset codes i introduction and geometrical classification practically all known good constructive coding techniques for bandlimited channels including lattice codes and various trellis coded modulation schemes can be characterized as coset codes a coset code is defined by a lattice partition lambda lambda and by a binary encoder c that selects a sequence of cosets of the lattice lambda the fundamental coding gain of a coset code as well as other important parameters such as the error coefficient the decoding complexity and the constellation expansion factor are purely geometric parameters determined by c lambda lambda the known types of coset codes as well as a number of new classes that systematize and generalize known codes are classified and compared in terms of these parameters

the optimum combination of block codes and receivers for arbitrary channels a determination is made of the combinations of transmitted block codewords and matching receiver filters that maximize the signal to noise ratio at the detector with arbitrary channel impulse response and arbitrary noise spectrum this permits representing the channel as a set of parallel uncoupled subchannels with uncorrelated noise the representation is used to calculate the capacity of an arbitrary block coded time discrete channel it is shown that substantial coding gains compared to symbol by symbol processing can be achieved the block code used can be concatenated with trellis coded modulation so that the two coding gains are additive

spatio temporal coding for wireless communication multipath signal propagation has long been viewed as an impairment to reliable communication in wireless channels this paper shows that the presence of multipath greatly improves achievable data rate if the appropriate communication structure is employed a compact model is developed for the multiple input multiple output mimo dispersive spatially selective wireless communication channel the multivariate information capacity is analyzed for high signal to noise ratio snr conditions the mimo channel can exhibit a capacity slope in bits per decibel of power increase that is proportional to the minimum of the number multipath components the number of input antennas or the number of output antennas this desirable result is contrasted with the lower capacity slope of the well studied case with multiple antennas at only one side of the radio link a spatio temporal vector coding stvc communication structure is suggested as a means for achieving mimo channel capacity the complexity of stvc motivates a more practical reduced complexity discrete matrix multitone dmmt space frequency coding approach both of these structures are shown to be asymptotically optimum an adaptive lattice trellis coding technique is suggested as a method for coding across the space and frequency dimensions that exist in the dmmt channel experimental examples that support the theoretical results are presented

effect of fluid depth on the hydroelastic vibration of free edge circular plate abstract this paper is concerned with the effect of water depth on the free vibration of free edge circular plates resting on a free fluid surface the problem addressed is formulated by using the hankel transformation method which leads to dual integral equations the solution of dual integral equations is solved numerically by using fourier bessel series the fluid is assumed to be inviscid and incompressible the kirchhoff theory of plates is used to model the elastic thin plate numerical results are given in non dimensional form for free edge circular plates in order to be ready to use in applications to validate the theoretical results experiments were carried out experimental results are in good agreement with theoretical results it is found that the effect of the fluid depth can be neglected when the fluid depth is greater than the diameter of the circular plates but becomes significant as the water depth decreases it is also observed in the experimental results that the fluid damping increases as the water depth decreases

orthogonality of wet modes in coupled vibration abstract the orthogonality property of wet modes for arbitrary storage vessels filled or partially filled with compressible fluid is investigated by means of love s thin shell equations and a linear potential flow theory the proof shows that the wet modes do possess the orthogonality property for all kinds of fluid filled tanks with zero boundary energy conditions when incompressible fluid is considered and the effect of free surface waves is neglected it is pointed out that there is another kind of orthogonality relationship among wet modes when a compressible fluid is contained or and the effect of the free surface waves is considered

viable control for uncertain nonlinear dynamical systems described by differential inclusions in this paper we will study the viable control problem for a class of uncertain nonlinear dynamical systems described by a differential inclusion the goal is to construct a feedback control such that all trajectories of the system are viable in a map moreover for any initial states no viable in the map under the feedback control all solutions of the system are steered to the map with an exponential convergence rate and viable in the map after a finite time t in this case an estimate of the time t of all trajectories attaining the map is given in the nanomedicine system an example inspired from cerebral embolism and cerebral thrombosis problems illustrates the use of our main results

variable structure control of robot manipulators with nonlinear sliding manifolds performance characteristics of a sliding mode controller depend essentially on a selected sliding manifold customarily the variable structure controllers operate with linear sliding surfaces however using nonlinear or time varying manifolds may provide definite advantages in particular they may provide faster convergence in this paper a control algorithm is presented which guarantees the occurrence of the sliding mode on nonlinear or time varying manifolds the bounds needed for calculating the switching gains are determined in terms of parameter variations rather than bounds on the system matrices the parameter bounds are usually evident and can be easily established or estimated while matrix bounds can rarely be justified in practical problems in this paper we also present an adaptive version of the controller which provides an automatic estimation of the parameter bounds the robustness of the controller with respect to a class of state dependent uncertainties is analysed by the lyapunov m

buckling and vibration of polar orthotropic circular plate resting on winkler foundation buckling and vibrational behavior of polar orthotropic circular plates of linearly varying thickness is presented on the basis of classical plate theory the plate is resting on winkler type foundation an approximate solution has been obtained by ritz method which employs basis functions based upon static deflection of polar orthotropic plates the effect of elastic foundation and that of orthotropy on the natural frequency of plate has been illustrated for different values of taper parameter flexibility parameter in plane force and nodal diameter the critical buckling load for clamped and simply supported plates have been obtained a comparison of results with those available in literature has been presented

a new class of stabilizing controllers for uncertain dynamical systems this paper is concerned with the problem of designing a stabilizing controller for a class of uncertain dynamical systems the vector of uncertain parameters q cdot is time varying and its values q t lie within a prespecified bounding set q in r p furthermore no statistical description of q cdot is assumed and the controller is shown to render the closed loop system practically stable in a so called guaranteed sense that is the desired stability properties are assured no matter what admissible uncertainty q cdot is realized within the perspective of previous research in this area this paper contains one salient feature the class of stabilizing controllers which we characterize is shown to include linear controllers when the nominal system happens to be linear and time invariant in contrast in much of the previous literature see for example 1 2 7 and 9 a linear system is stabilized via nonlinear control another feature of this paper is the fact that the

practically realizable digital transmission significantly below the nyquist bandwidth proposes a practically realizable digital signaling scheme that requires a bandwidth significantly below the nyquist limit and at the same time achieves the same asymptotic performance as memoryless pam a five step iterative procedure for constructing such schemes is presented and examples that occupy down to about 60 percent of the nyquist bandwidth are demonstrated using this simple procedure practical receiver structures are also briefly discussed

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

output tracking design of affine nonlinear plant via variable structure system an output tracking design for affine nonlinear systems via a variable structure system is proposed the structure algorithm is used to determine if the considered system is left invertible it is shown that if such a condition is satisfied then a sliding mode controller can be designed to achieve output tracking the decouplability condition in conventional approaches is now replaced by the weaker left invertibility condition stable tracking is guaranteed if the internal mode is bounded input bounded state stable simulation results are included to demonstrate the design procedure

natural vibrations and stability of shells of revolution interacting with an internal fluid flow abstract a finite element algorithm is proposed to investigate the dynamic behavior of elastic shells of revolution containing a quiescent or a flowing inviscid fluid in the framework of linear theory the fluid behavior is described using the perturbed velocity potential the shell behavior is treated in the framework of the classical shell theory and variational principle of virtual displacements incorporating a linearized bernoulli equation for calculation of hydrodynamic pressure acting on the shell the problem reduces to evaluation and analysis of the eigenvalues in the connected system of equations obtained by coupling the equations for velocity perturbations with the equations for shell displacements for cylindrical shells the results of numerical simulations are compared with recently published experimental analytical and numerical data the paper also reports the results of studying the dynamic behavior of shells under various boundary conditions for the perturbed velocity potential the investigation made for conical shells has shown that under certain conditions an increase in the cone angle can change a divergent type of instability to a flutter type