blind channel equalization and spl epsiv approximation algorithms we show that a blind equalizer can be obtained without estimating any statistics based on the received data if the constellation alphabet is known the idea is to formulate the blind channel equalization problem into a quadratic optimization with binary constraints then efficient spl epsiv approximation algorithms are presented and applied to find the equalizer coefficients the proposed approach blindly equalizes the channel at symbol baud rates does not rely on estimating any statistics applies to nonminimum phase channels and converges to an spl epsiv neighborhood of a global optimum simulation results support the theoretical analysis

maximum likelihood estimation of the autoregressive model by relaxation on the reflection coefficients a method for autoregressive parameter estimation which successively maximizes the likelihood with respect to each reflection coefficient while keeping the others fixed is presented the algorithm generalizes the recursive maximum likelihood technique of s m kay 1983 which corresponds to performing only one iteration cycle an interesting application is the estimation of a toeplitz covariance matrix simulations show that the algorithm converges quite fast and provides much better estimates than current procedures for short record length

estimate of the difference between the kac operator and the schrodinger semigroup an operator norm estimate of the difference between the kac operator and the schrodinger semigroup is proved and used to give a variant of the trotter product formula for schrodinger operators in thelp operator norm this extends helffer s result in thel2 operator norm to the case in thelp operator norm for more general scalar potentials and with vector potentials the method of the proof is probabilistic based on the feynman kac and feynman kac ito formula

calf muscle moment work and efficiency in level walking role of series elasticity abstract moment and work of the human calf muscles in level walking were determined by means of an emg to force processor based on a muscle analogue hof and van den berg 1981 j biomechanics 14 747 758 759 770 771 785 787 792 nine subjects four women five men walked on a level treadmill at speeds between 0 5 and 2 5 m s 1 in their self chosen pace and at forced pace with steplengths between 0 3 and 1 1 m the calf muscles are normally only active in the stance phase the moment increases with a variable course to a peak just before push off this peak moment increases with the walking speed from the reference moment the value in standing on the toes with one leg at zero speed to 1 5 2 1 times this value at a speed of 2 m s 1 and decreases at still greater speeds during the roll over phase work is done on the calf muscles negative work followed by positive work in push off the negative work is constant 0 20 0 36 j kg 1 depending on the subject the positive work increases linearly with steplength not with speed from zero at ca 0 35 m to 0 50 j kg 1 at a steplength of 1 1 m the interaction between the contractile and the series elastic component in the muscle could be studied by means of the analogue a great part of the work done on the muscle and of the positive work done by the contractile component are stored in the series elastic component the stored energy is released at a high rate in push off this mechanism ideally requires a concerted contraction i e a contraction in which the activation is matched to the load to the effect that the length of the contractile component remains constant the muscle then behaves like a spring consequences are a only little of the negative work gets lost b the length of the contractile component remains close to the optimum of the force length relation c the shortening speed of the contractile component is now in the range where the muscle works at a high efficiency and d high power peaks can be delivered due to the catapult action

moment analysis for localization in random schrodinger operators we study localization effects of disorder on the spectral and dynamical properties of schrodinger operators with random potentials the new results include exponentially decaying bounds on the transition amplitude and related projection kernels including in the mean these are derived through the analysis of fractional moments of the resolvent which are finite due to the resonance diffusing effects of the disorder the main difficulty which has up to now prevented an extension of this method to the continuum can be traced to the lack of a uniform bound on the lifshitz krein spectral shift associated with the local potential terms the difficulty is avoided here through the use of a weak l 1 estimate concerning the boundary value distribution of resolvents of maximally dissipative operators combined with standard tools of relative compactness theory

comparison between emg to force processing and kinetic analysis for the calf muscle moment in walking and stepping abstract in emg to force processing the force of a muscle or the corresponding muscle moment with respect to the joint is determined from emg and muscle length by means of a model of the muscle s contractile and elastic properties in kinetic analysis the joint moment is calculated from the ground reaction force and the positions and accelerations of the body segments by means of newtonian equations based on a rigid body segment model these two fundamentally different methods have been compared by determining simultaneously the calf muscle moment and the total ankle moment in walking at slow moderate and fast speed and in stepping up and down a low bench as long as there is no activity of other muscles the moments obtained by either method should be identical the analysis was restricted to such periods as assessed from the emg of tibialis anterior in each experimental condition three steps were analyzed in five subjects of 21 22 yr in comparison with the results of kinetic analysis emg processing shows differences between 7 and 54 nm r m s with an average of 22 nm r m s normalized with respect to the r m s value of the moment itself the differences amount to 0 13 0 51 with an average of 0 22 in the majority of cases there was no systematic deviation between emg processing and kinetic analysis and the r m s difference was of the same order of magnitude as determined previously in ergometer experiments

joint data and channel estimation using blind trellis search techniques a novel method of maximum likelihood sequence estimation is proposed for data that are transmitted over unknown linear channels this procedure does not require a startup sequence for estimating the channel impulse response rather the data and the channel are simultaneously estimated it is implemented without any loss of optimality by a trellis search algorithm which searches for the best data sequence from among a number of hypothesized trellises which are constructed from the observed sequence the number of states in each trellis and the number of trellises grow exponentially with the channel memory a suboptimal trellis search algorithm is proposed whose complexity at best is slightly higher than that of the adaptive viterbi algorithm operating with a known channel response a simplified channel estimation algorithm when the number of data alphabets is greater than 2 is also proposed fast convergence of the algorithm in estimating the channel is demonstrated for binary pulse amplitude modulation over a variety of channels convergence over a wide range of snr occurs within 100 symbols the channel estimation algorithm for multi level signals converges within 500 1000 symbols we finally present an application of this algorithm to the problem of sequence estimation in the presence of rapidly time varying intersymbol interference the algorithm provides reliable zero delay decisions which results in a better channel tracking algorithm when compared to previously proposed schemes

mechanical output from individual muscles during explosive leg extensions the role of biarticular muscles the main result of this study is that biarticular leg muscles contribute significantly to the work done at joints due to transfer of power during explosive leg extensions in particular a net power transfer was shown from hip to knee joint during jumping and sprinting seven elite athletes performed explosive one legged jump and sprint push offs kinematics ground reaction forces and el tromyography emg of leg muscles were recorded the mechanical output of six individu muscle groups was estimated by using hill based muscle models the emg and kinematics served as input to these models for jumping as well as for sprinting the model estimated similar results for the relative work contribution done about a joint due to transfer of power by the biarticular muscles rectus femoris showed a power transfer from hip to knee joint while in contrast hamstrings showed a power transfer from knee to hip joint regardless of these opposite directions of power transfer a net transfer occurred from the hip to the knee joint the relative work contribution of hamstrings done in hip extension was 7 in jumping and 11 in sprinting for rectus femoris the relative work contribution done in knee extension was 21 in jumping and 31 in sprinting power transferring actions by gastrocnemius from knee to ankle contributed 25 in jumping and 28 in sprinting to the work done in piantar flexion these results support the hypothesis that the action of biarticular muscles contributes to a net transfer of power from proximal to distal joints during explosive leg extensions this action of the biarticular muscles causes an efficient conversion of body segment rotations into the desired translation of the body centre of gravity

blind separation of instantaneous mixture of sources via an independent component analysis in this paper we introduce a procedure for separating a multivariate distribution into nearly independent components based on minimizing a criterion defined in terms of the kullback leibner distance by replacing the unknown density with a kernel estimate we derive useful forms of this criterion when only a sample from that distribution is available we also compute the gradient and hessian of our criteria for use in an iterative minimization setting this gradient to zero yields a set of separating functions similar to the ones considered in the source separation problem except that here these functions are adapted to the observed data finally some simulations are given illustrating the good performance of the method

the uniqueness of the integrated density of states for the schrodinger operators with magnetic fields the integrated density of states ids for the schrodinger operators is defined in two ways by using the counting function of eigenvalues of the operator restricted to bounded regions with appropriate boundary conditions or by using the spectral projection of the whole space operator a sufficient condition for the coincidence of the two definitions above is given moreover a sufficient condition for the coincidence of the ids for the dirichlet boundary conditions and the ids for the neumann boundary conditions is given the proof is based only on the fundamental items in functional analysis such as the min max principle etc

the magnetic weyl calculus in the presence of a variable magnetic field the weyl pseudodifferential calculus must be modified the usual modification based on the minimal coupling principle at the level of the classical symbols does not lead to gauge invariant formulas if the magnetic field is not constant we present a gauge covariant quantization relying on the magnetic canonical commutation relations the underlying symbolic calculus is a deformation defined in terms of the magnetic flux through triangles of the classical moyal product

non trapping magnetic fields and morrey campanato estimates for schrodinger operators abstract we prove some uniform in a priori estimates for solutions of the equation i a 2 u v x u i u f 0 0 the estimates are obtained in terms of morrey campanato norms and can be used to prove absence of zero resonances in a suitable sense for electromagnetic hamiltonians quantitative conditions on the size of the trapping component of the magnetic field and the non repulsive component of the electric field are given

maximal inequalities and riesz transform estimates on lp spaces for magnetic schrodinger operators ii the paper concerns the magnetic schrodinger operator h bf a v sum j 1 n frac 1 i frac partial partial x j a j 2 v on mathbb r n we prove some lp estimates on the riesz transforms of h and we establish some related maximal inequalities the conditions that we arrive at are essentially based on the control of the magnetic field by the electric potential

separation of independent sources from correlated inputs the characterization of independent stationary stochastic components sources is generally achieved by using the spectral matrix of partially correlated measurements which are linearly related to the components of interest in the general case where no assumptions are made concerning the way the sources are mixed on the measurements the spectral matrix is not able to extract the true sources while spectral analysis only uses second order properties of independent stochastic sources a procedure based on higher order analysis fourth order cross cumulants is developed this approach leads to a complete identification of the sources

the forward problem for the electromagnetic helmholtz equation with critical singularities abstract we study the forward problem of the magnetic schrodinger operator with potentials that have a strong singularity at the origin we obtain new resolvent estimates and give some applications on the spectral measure and on the solutions of the associated evolution problem

on moments of negative eigenvalues for the pauli operator abstract this paper concerns the three dimensional pauli operator p p a x 2 v x with a nonhomogeneous magnetic fieldb curl a the following lieb thirring type inequality for the moment of negative eigenvalues is established as j j c 1 r 3 v x 5 2 dx c 2 r 3 b p x 3 2 v x dx wherep 3 2 andbp x is thelpaverage of b over certain cube centered atxwith a side length scaling like b 1 2 we also show that ifbhas a constant direction j j c 1 r 3 v x 3 2 dx c 2 r 3 b p x v x 1 2 dx where 1 2 andp 1

ultracontractivity and the heat kernel for schrodinger operators and dirichlet laplacians abstract abstract connections between integral kernels of positivity preserving semigroups and suitable lp contractivity properties are established then these questions are studied for the semigroups generated by v and h the dirichlet laplacian for an open connected region as an application under a suitable hypothesis sobolev estimates are proved valid up to of the form x c 0 x h k 2 where 0 is the unique positive l2 eigenfunction of h

lower bounds for the spectra of schrodinger operators with magnetic fields abstract an explicit representation of lower bounds for the spectra of schrodinger operators with magnetic fields on compact riemannian manifolds is given using the positivity of the pauli hamiltonian this representation is applied to show some asymptotic properties of a stochastic oscillatory integral and the transverse analyticity of the law of a stochastic line integral

bounds on the heat kernel of the schrodinger operator in a random electromagnetic field we obtain lower and upper bounds on the heat kernel and green functions of the schrodinger operator in a random gaussian magnetic field and a fixed scalar potential we apply the stochastic feynman kac representation diamagnetic upper bounds and the jensen inequality for the lower bound we show that if the covariance of the electromagnetic vector potential is increasing at large distances then the lower bound decreases exponentially fast for large distances and a large time

essential self adjointness for semi bounded magnetic schrodinger operators on non compact manifolds abstract we prove essential self adjointness for semi bounded below magnetic schrodinger operators on complete riemannian manifolds with a given positive smooth measure which is fixed independently of the metric some singularities of the scalar potential are allowed this is an extension of the povzner wienholtz simader theorem the proof uses the scheme of wienholtz but requires a refined invariant integration by parts technique as well as the use of a family of cut off functions which are constructed by a non trivial smoothing procedure due to karcher

on the number of negative eigenvalues for a schrodinger operator with magnetic field we consider the schrodinger operator with magnetic field h sum limits j 1 n left frac 1 i frac partial partial x j a j right 2 vin mathbb r n under certain conditions on the magnetic fieldb curla we generalize the fefferman phong estimates bull a m s 9 129 206 1983 on the number of negative eigenvalues for v to the operatorh upper and lower bounds are established our estimates incorporate the contribution from the magnetic field the conditions onb in particular are satisfied if the magnetic potentialsaj x are polynomials

new bounds on the maximum ionization of atoms we prove that the maximum number nc of non relativistic electrons that a nucleus of charge z can bind is less than 1 22z 3z1 3 this improves lieb s upper bound nc 2z 1 lieb phys rev a 29 3018 3028 1984 when z 6 our method also applies to non relativistic atoms in magnetic field and to pseudo relativistic atoms we show that in these cases under appropriate conditions limsup z to infty n c z le 1 22

emg to force processing iii estimation of model parameters for the human triceps surae muscle and assessment of the accuracy by means of a torque plate the parameters of the active state and the series elastic component of the hill muscle model were estimated for the human calf muscles by means of a torque plate on seven normal subjects together with the results of the calfergometer experiments part ii this yields the complete set of parameters for the emg to force processor based on the hill model part i the accuracy of the processor was assessed by means of a set of severe test contractions in which the subjects tilted on one foot at various velocities slow to as fast as possible the mechanical work m dt and the integrated torque m dt were calculated for these contractions m being the torque calculated by the emg processor and the measured angular velocity these values of the work and the integrated torque were compared to those obtained with the measured torque mm instead of m the relative error for positive work negative work and integrated torque was 6 2 14 means s d data on the peak values of m mm are also given

sample partial autocorrelation function a new estimation procedure for a partial autocorrelation coefficient of a stationary time series based on a natural geometrical analysis of the sample data is proposed a method for autoregressive parameter estimation which is midway between the constrained least squares procedure of burg and the unconstrained one given by the for ward backward least squares method is then obtained the method provides a stable filter and operates in a recursive model order fash ion simulation results indicate that the method eliminates some short comings of classical least squares procedures and stays close to the ex act maximum likelihood estimation method

on the mean field approximation of many boson dynamics abstract we show under general assumptions that the mean field approximation for quantum many boson systems is accurate our contribution unifies and improves most of the known results the proof uses general properties of quantization in infinite dimensional spaces phase space analysis and measure transportation techniques

constructive representations of propagators for quantum systems with electromagnetic fields the quantum evolution of an n body system of particles that mutually interact through scalar fields and couple to an arbitrary external electromagnetic field is rigorously described both operator and kernel valued solutions to the evolution problem are found based upon a particular realization of the dyson expansion a convergent series representation of the propagator the kernel of the schrodinger time evolution operator is obtained the basic approach is to embed the quantum evolution problem in the larger class of evolution problems that result if mass is allowed to be complex quantum evolution with real mass is considered to be the boundary value of the complex mass evolution problem the constructive representation of the propagator is determined for the class of analytic scalar and vector fields that are given as fourier transforms of time dependent scalar and vector valued measures

emg to force processing ii estimation of parameters of the hill muscle model for the human triceps surae by means of a calfergometer on a calfergometer isotonic contractions were performed by the calf muscles of human subjects the measured torque mm was compared to the torque m processed from the emg and the joint angle by means of an electronic processor based on the hill muscle model by means of these experiments the model parameters were determined for the torque angle relation the torque angular velocity relation and the parallel elastic component pec experiments were done a for the soleus only 4 subjects and b for the combination of soleus and gastrocnemius 8 subjects it turned out that the torque angle parameters varied among subjects the torque angular velocity parameters for soleus only varied also among subjects for the combined calf muscle group the interindividual differences in the torque angular velocity parameters could be neglected one of the parameters of the pec was the same for all subjects while the other was variable among the subjects the obtained parameter values are discussed and compared with available literature data values for the r m s and the peak error in the isotonic phases of the contraction are given and compared with values predicted from the stochastic properties of the emg signal

singular first order perturbations of the heat equation we exhibit dimension independent conditions under which the formal operator a a v can be defined on such that its closure in l 2 r s dx is quasi m accretive here a is real so that is nonselfadjoint the method of proof is a generalized version of the argument employed in the portion of the author s thesis where term a was originally considered specifically we construct exp t as a limit of approximating semigroups since the thesis appeared kato has also dealt with the term a his conditions on a and v are similar to but more general than the conditions that appear here in addition he considers magnetic vector potentials of interest here is the semigroup method itself the conciseness of the arguments thereby produced and a relaxed condition on div a

endpoint strichartz estimates for the magnetic schrodinger equation abstract we prove strichartz estimates for the schrodinger equation with an electromagnetic potential in dimension n 3 the decay and regularity assumptions on the potentials are almost critical i e close to the coulomb case in addition we require repulsivity and a nontrapping condition which are expressed as smallness of suitable components of the potentials while the potentials themselves can be large the proof is based on smoothing estimates and new sobolev embeddings for spaces associated to magnetic potentials

energy concentration and explicit sommerfeld radiation condition for the electromagnetic helmholtz equation we study the electromagnetic helmholtz equation ib x 2u x n x u x f x x rd with the magnetic vector potential b x and n x a variable index of refraction that does not necessarily converge to a constant at infinity but can have an angular dependence like n x n x x as x we prove an explicit sommerfeld radiation condition rd bu in 1 2x x u 2dx1 x for solutions obtained from the limiting absorption principle and we also give a new energy estimate rd n x x 2 u 21 x dx which explains the main physical effect of the angular dependence of n at infinity and deduces that the energy concentrates in the directions given by the critical points of the potential

comportement des noyaux de la chaleur des operateurs de schrodinger et applications a certaines equations paraboliques semi lineaires abstract we consider general schrodinger operators on domains of riemannian manifolds with possibly exponential volume growth we prove sharp large time gaussian upper bounds these bounds are then used to prove new l p l p estimates for the corresponding semigroups applications to semi linear parabolic equations are given

blind source separation of signals with known alphabets using spl epsi approximation algorithms we show that blind separation of signals in given alphabets can be formulated into a quadratic optimization problem with integer constraints then efficient spl epsi approximation algorithms are applied to directly estimate the transmitted signals the proposed approach does not require any high order statistics moreover the algorithms converge to an spl epsi neighborhood of the global optimum with polynomial computational complexity simulations show that the algorithm achieves satisfactory performance using a short length of data

quasi maximum likelihood multiuser detection using semi definite relaxation with application to synchronous cdma the maximum likelihood ml multiuser detector is well known to exhibit better bit error rate ber performance than many other multiuser detectors unfortunately ml detection mld is a nondeterministic polynomial time hard np hard problem for which there is no known algorithm that can find the optimal solution with polynomial time complexity in the number of users in this paper a polynomial time approximation method called semi definite sd relaxation is applied to the mld problem with antipodal data transmission sd relaxation is an accurate approximation method for certain np hard problems the sd relaxation ml sdr ml detector is efficient in that its complexity is of the order of k3 5 where k is the number of users we illustrate the potential of the sdr ml detector by showing that some existing detectors such as the decorrelator and the linear minimum mean square error detector can be interpreted as degenerate forms of the sdr ml detector simulation results indicate that the ber performance of the sdr ml detector is better than that of these existing detectors and is close to that of the true ml detector even when the cross correlations between users are strong or the near far effect is significant

magnetic virial identities weak dispersion and strichartz inequalities we show a family of virial type identities for the schrodinger and wave equations with electromagnetic potentials as a consequence some weak dispersive inequalities in space dimension n 3 involving morawetz and smoothing estimates are proved finally we apply them to prove strichartz inequalities for the wave equation with a non trapping electromagnetic potential with almost coulomb decay

analytical method for blind binary signal separation the blind separation of multiple co channel binary digital signals using an antenna array involves finding a factorization of a data matrix x into x as where all entries of s are 1 or 1 it is shown that this problem can be solved exactly and noniteratively via a certain generalized eigenvalue decomposition as indicated by simulations the algorithm is robust in the presence of noise an interesting implication is that certain cluster segmentation problems can be solved using eigenvalue techniques

simple diamagnetic monotonicities for schrodinger operators with inhomogeneous magnetic fields of constant direction under certain simplifying conditions we detect monotonicity properties of the ground state energy and the canonical equilibrium density matrix of a spinless charged particle in the euclidean plane subject to a perpendicular possibly inhomogeneous magnetic field and an additional scalar potential firstly we point out a simple condition warranting that the ground state energy does not decrease when the magnetic field and or the potential is increased pointwise secondly we consider the case in which both the magnetic field and the potential are constant along one direction in the plane and give a genuine path integral argument for corresponding monotonicities of the density matrix diagonal and the absolute value of certain off diagonals our results complement to some degree results of loss and thaller 1997 commun math phys 186 95 and erdos 1997 j math phys 38 1289

blind ml detection of orthogonal space time block codes efficient high performance implementations orthogonal space time block codes ostbcs have attracted much attention owing to their simple code construction maximal diversity gain and low maximum likelihood ml detection complexity when channel state information csi is available at the receiver this paper addresses the problem of ml ostbc detection with unknown csi focusing on the binary and quaternary psk constellations we show that blind ml ostbc detection can be simplified to a boolean quadratic program bqp from an optimization viewpoint the bqp is still a computationally hard problem and we propose two alternatives for dealing with this inherent complexity first we consider the semidefinite relaxation sdr approach which leads to a suboptimal but accurate blind ml detection algorithm with an affordable worst case computational cost we also consider the sphere decoding approach which leads to an exact blind ml detection algorithm that remains computationally expensive in the worst case but generally incurs a reasonable average computational cost for the two algorithms we study implementation methods that can significantly reduce the computational complexity simulation results indicate that the two blind ml detection algorithms are competitive in that the bit error performance of the two algorithms is almost the same and is noticeably better than that of some other existing blind detectors moreover numerical studies show that the sdr algorithm provides better complexity performance than the sphere decoder in the worst case sense and vice versa in the average sense

abstract criteria for multiple solutions to nonlinear coupled equations involving magnetic schrodinger operators we consider a system of nonlinear coupled equations involving magnetic schrodinger operators and general potentials we provide the criteria for the existence of multiple solutions to these equations as special cases we get the classical results on existence of infinitely many distinct solutions within hartree and hartree fock theory of atoms and molecules subject to an external magnetic fields we also extend recent results within this theory including coulomb system with a constant magnetic field a decreasing magnetic field and a physically measurable magnetic field

gaussian kernels have only gaussian maximizers a gaussian integral kernel g x y on rn x rn is the exponential of a quadratic form in x and y the fourier transform kernel is an example the problem addressed here is to find the sharp bound of g as an operator from l p rp to l q rn and to prove that the l p rn functions that saturate the bound are necessarily gaussians this is accomplished generally for 1 q in some special cases besides greatly extending previous results in this area the proof technique is also essentially different from earlier ones a corollary of these results is a fully multidimensional multilinear generalization of young s inequality

blind separation of mixture of independent sources through a quasi maximum likelihood approach we propose two methods for separating mixture of independent sources without any precise knowledge of their probability distribution they are obtained by considering a maximum likelihood ml solution corresponding to some given distributions of the sources and relaxing this assumption afterward the first method is specially adapted to temporally independent non gaussian sources and is based on the use of nonlinear separating functions the second method is specially adapted to correlated sources with distinct spectra and is based on the use of linear separating filters a theoretical analysis of the performance of the methods has been made a simple procedure for optimally choosing the separating functions is proposed further in the second method a simple implementation based on the simultaneous diagonalization of two symmetric matrices is provided finally some numerical and simulation results are given illustrating the performance of the method and the good agreement between the experiments and the theory

a blind source separation technique using second order statistics separation of sources consists of recovering a set of signals of which only instantaneous linear mixtures are observed in many situations no a priori information on the mixing matrix is available the linear mixture should be blindly processed this typically occurs in narrowband array processing applications when the array manifold is unknown or distorted this paper introduces a new source separation technique exploiting the time coherence of the source signals in contrast with other previously reported techniques the proposed approach relies only on stationary second order statistics that are based on a joint diagonalization of a set of covariance matrices asymptotic performance analysis of this method is carried out some numerical simulations are provided to illustrate the effectiveness of the proposed method

source separation when the input sources are discrete or have constant modulus in this paper we present a new method for the source separation problem when some prior information on the input sources is available more specifically we study the situation where the distributions of the input signals are discrete or are concentrated on a circle the method is based on easy properties of hankel forms and on the divisibility of gaussian distributions in both situations we prove that the estimator converges in absence of noise or if we know the first moments of the noise up to its scale moreover in the absence of noise the estimate converges with a finite number of observations

blind mimo ar system identification and source separation with finite alphabet in this paper a new method for system identification and blind source separation in a multiple input multiple output mimo system is proposed the mimo channel is modeled by a multi dimensional autoregressive ar system the transmitted signals are assumed to take values from a finite alphabet modeled by the gaussian mixture model gmm with infinitesimal variances the expectation maximization em algorithm for estimation of the mimo ar model parameters is derived the performance of the proposed algorithm in terms of probability of error in signal detection and root mean squared error rmse of the system parameters and system transfer function estimates is evaluated via simulations it is shown that the obtained probability of error is very close to the probability of error of the optimal algorithm which assumes known channel state information

blind separation of synchronous co channel digital signals using an antenna array i algorithms we propose a maximum likelihood ml approach for separating and estimating multiple synchronous digital signals arriving at an antenna array at a cell site the spatial response of the array is assumed to be known imprecisely or unknown we exploit the finite alphabet property of digital signals to simultaneously estimate the array response and the symbol sequence for each signal uniqueness of the estimates is established for bpsk signals we introduce a signal detection technique based on the finite alphabet property that is different from a standard linear combiner computationally efficient algorithms for both block and recursive estimation of the signals are presented this new approach is applicable to an unknown array geometry and propagation environment which is particularly useful in wireless communication systems simulation results demonstrate its promising performance

existence of a solution to hartree fock equations with decreasing magnetic fields in the presence of an external magnetic field we prove existence of a ground state within the hartree fock theory of atoms and molecules the ground state exists provided the magnetic field decreases at infinity and the total charge z of k nuclei exceeds n 1 where n is the number of electrons in the opposite direction no ground state exists if n 2z k

optimal heat kernel estimates for schrodinger operators with magnetic fields in two dimensions sharp smoothing estimates are proven for magnetic schrodinger semigroups in two dimensions under the assumption that the magnetic field is bounded below by some positive constantb0 as a consequence thel norm of the associated integral kernel is bounded by thel norm of the mehler kernel of the schrodinger semigroup with the constant magnetic fieldb0

essential selfadjointness of singular magnetic schrodinger operators on riemannian manifolds in this paper we extend the well known leinfelder simader theorem on the essential selfadjointness of singular schrodinger operators to arbitrary complete riemannian manifolds this improves some earlier results of shubin milatovic and others

scattering in the energy space for the nls with variable coefficients we consider the nls with variable coefficients in dimension n ge 3 begin aligned i partial t u lu f u 0 qquad lv nabla b cdot a x nabla b v c x v qquad nabla b nabla ib x end aligned on mathbb r n or more generally on an exterior domain with dirichlet boundary conditions for a gauge invariant defocusing nonlinearity of power type f u simeq u gamma 1 u we assume that l is a small long range perturbation of delta plus a potential with a large positive part the first main result of the paper is a bilinear smoothing interaction morawetz estimate for the solution as an application under the conditional assumption that strichartz estimates are valid for the linear flow e itl we prove global well posedness in the energy space for subcritical powers gamma 1 frac 4 n when the domain is mathbb r n by extending the strichartz estimates due to tataru am j math 130 3 571 634 2008 we prove that the conditional assumption is satisfied and deduce well posedness and scattering in the energy space

predictions of knee and ankle moments of force in walking from emg and kinematic data abstract a deterministic model was developed and validated to calculate instantaneous ankle and knee moments during walking using processed emg from representative muscles instantaneous joint angle as a correlate of muscle length and angular velocity as a correlate of muscle velocity and having available total instantaneous joint moments for derivation of certain model parameters a linear regression of the moment on specifically processed emg recorded while each subject performed cycled isometric calibration contractions yielded the constants for a basic moment emg relationship using the resultant moment for optimization the predicted moment was proportionally augmented for longer muscle lengths and reduced for shorter lengths similarly the predicted moment was reduced for shortening velocities and increased if the muscle was lengthening the plots of moments predicted using the full model and those calculated from link segment mechanics followed each other quite closely the range of root mean square errors were 3 2 9 5 nm for the ankle and 4 7 13 0 nm for the knee

pauli operator and aharonov casher theorem for measure valued magnetic fields we define the two dimensional pauli operator and identify its core for magnetic fields that are regular borel measures the magnetic field is generated by a scalar potential hence we bypass the usual a l 2 loc condition on the vector potential which does not allow to consider such singular fields we extend the aharonov casher theorem for magnetic fields that are measures with finite total variation and we present a counterexample in case of infinite total variation one of the key technical tools is a weighted l 2 estimate on a singular integral operator

schrodinger operators in the twentieth century this paper reviews the past fifty years of work on spectral theory and related issues in nonrelativistic quantum mechanics

on the spectrum of two dimensional schrodinger operators with spherically symmetric radially periodic magnetic fields we investigate the spectrum of the two dimensional schrodinger operator where the magnetic field and the electric potential v are spherically symmetric i e and b is p periodic similarly for v by considering two different gauges we get the following results in case the spectrum contains a semi axis that consists alternately of intervals of absolutely continuous and dense point spectrum in case the essential spectrum is purely dense point spectrum and possibly there are spectral gaps

on the maximal ionization for the atomic pauli operator within the born oppenheimer approximation lieb proved that the number of non relativistic spin frac 1 2 particles that can be bound to an atom of nuclear charge z in the presence of an external magnetic field satisfies n max 2z 1 provided the magnetic field tends to zero at infinity and the coupling between the magnetic field and the spin is ignored assuming that the magnetic field is generic we prove an upper bound which holds when the spin field coupling is included the set of generic magnetic fields contains an open dense subset of l 3 2 r 3 3

approximating quadratic programming with bound and quadratic constraints we consider the problem of approximating the global maximum of a quadratic program qp subject to bound and simple quadratic constraints based on several early results we show that a 4 7 approximate solution can be obtained in polynomial time

an information maximization approach to blind separation and blind deconvolution we derive a new self organizing learning algorithm that maximizes the information transferred in a network of nonlinear units the algorithm does not assume any knowledge of the input distributions and is defined here for the zero noise limit under these conditions information maximization has extra properties not found in the linear case linsker 1989 the nonlinearities in the transfer function are able to pick up higher order moments of the input distributions and perform something akin to true redundancy reduction between units in the output representation this enables the network to separate statistically independent components in the inputs a higher order generalization of principal components analysis we apply the network to the source separation or cocktail party problem successfully separating unknown mixtures of up to 10 speakers we also show that a variant on the network architecture is able to perform blind deconvolution cancellation of unknown echoes and reverberation in a speech signal finally we derive dependencies of information transfer on time delays we suggest that information maximization provides a unifying framework for problems in blind signal processing

linear response theory for magnetic schrodinger operators in disordered media abstract we justify the linear response theory for an ergodic schrodinger operator with magnetic field within the noninteracting particle approximation and derive a kubo formula for the electric conductivity tensor to achieve that we construct suitable normed spaces of measurable covariant operators where the liouville equation can be solved uniquely if the fermi level falls into a region of localization we recover the well known kubo str eda formula for the quantum hall conductivity at zero temperature