sequential sequence estimation for channels with intersymbol interference of finite or infinite length a sequential sequence estimator for channels with finite or infinite intersymbol interference isi is proposed it consists of a whitened matched filter followed by a sequential algorithm a key component of a sequential estimator is a suitable metric that accounts for the unequal search depth this metric is derived for the isi channel computer simulations for three different channels show that the sequential sequence estimator has considerably less computational complexity than a maximum likelihood sequence estimator using the viterbi algorithm mlse va while still maintaining the optimum estimation performance of the mlse va a performance not achievable with any reduced state viterbi algorithm

exact location of the multicritical point for finite dimensional spin glasses a conjecture we present a conjecture on the exact location of the multicritical point in the phase diagram of spin glass models in finite dimensions by generalizing our previous work we combine duality and gauge symmetry for replicated random systems to derive formulae which make it possible to understand all the relevant available numerical results in a unified way the method applies to non self dual lattices as well as to self dual cases in the former case of which we derive a relation for a pair of values of multicritical points for mutually dual lattices the examples include the j and gaussian ising spin glasses on the square hexagonal and triangular lattices the potts and zq models with chiral randomness on these lattices and the three dimensional j ising spin glass and the random plaquette gauge model

fictitious boundary and moving mesh methods for the numerical simulation of rigid particulate flows in this paper we investigate the numerical simulation of particulate flows using a new moving mesh method combined with the multigrid fictitious boundary method fbm s turek d c wan l s rivkind the fictitious boundary method for the implicit treatment of dirichlet boundary conditions with applications to incompressible flow simulations challenges in scientific computing lecture notes in computational science and engineering vol 35 springer berlin 2003 pp 37 68 d c wan s turek l s rivkind an efficient multigrid fem solution technique for incompressible flow with moving rigid bodies numerical mathematics and advanced applications enumath 2003 springer berlin 2004 pp 844 853 d c wan s turek direct numerical simulation of particulate flow via multigrid fem techniques and the fictitious boundary method int j numer method fluids 51 2006 531 566 with this approach the mesh is dynamically relocated through a linear partial differential equation to capture the surface of the moving particles with a relatively small number of grid points the complete system is realized by solving the mesh movement and the partial differential equations of the flow problem alternately via an operator splitting approach the flow is computed by a special ale formulation with a multigrid finite element solver and the solid particles are allowed to move freely through the computational mesh which is adaptively aligned by the moving mesh method in every time step one important aspect is that the data structure of the undeformed initial mesh in many cases a tensor product mesh or a semi structured grid consisting of many tensor product meshes is preserved while only the spacing between the grid points is adapted in each time step so that the high efficiency of structured meshes can be exploited numerical results demonstrate that the interaction between the fluid and the particles can be accurately and efficiently handled by the presented method it is also shown that the presented method significantly improves the accuracy of the previous multigrid fbm to simulate particulate flows with many moving rigid particles

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

block decision feedback equalization a natural generalization of the conventional decision feedback equalizer dfe based on block processing and maximum a posteriori decisions is presented this block dfe is indexed by two parameters depending on the block length p and the number of decisions q

efficient soft input soft output tree detection via an improved path metric tree detection techniques are often used to reduce the complexity of a posteriori probability app detection in multiantenna wireless communication systems in this paper we introduce an efficient soft input soft output tree detection algorithm that employs a new type of look ahead path metric in the process of branch pruning or sorting while conventional path metrics depend only on symbols on a visited path the new path metric accounts for unvisited parts of the tree in advance through an unconstrained linear estimator and adds a bias term that reflects the contribution of as yet undecided symbols by applying the linear estimate based look ahead path metric to an algorithm that selects the best paths for each level of the tree we develop a new soft input soft output tree detector called an improved soft input soft output algorithm iss ma based on an analysis of the probability of correct path loss we show that the improved path metric offers substantial performance gain over the conventional path metric we also demonstrate through simulations that the proposed iss ma can be a promising candidate for soft input soft output detection in high dimensional systems

computational complexity of sequential sequence estimation for intersymbol interference channels the computational complexity of a sequential algorithm sa developed for intersymbol interference isi channels is analyzed to determine the computational complexity the finite state machine that models the channel and white matched filter system of which the sa is a part is interpreted as a special convolutional encoder followed by a binary symbol to q ary symbol mapping it follows that the computational distribution is pareto and that there exists a computational cutoff rate r sub comp for the uncoded data considered the rate is fixed and the r sub comp criterion translates into a signal to noise ratio snr criterion an upper bound on snr sub comp is found analytically by assuming a uniform input distribution iteration equations developed by s arimoto 1976 are adapted to find the true snr sub comp numerically

bandwidth efficient coded modulation with optimized linear partial response signals we study the design of optimal signals for bandwidth efficient linear coded modulation previous results show that for linear channels with intersymbol interference isi reduced search decoding algorithms have near maximum likelihood error performance but with much smaller complexity than the viterbi decoder consequently the controlled isi introduced by a lowpass filter can be practically used for bandwidth reduction such spectrum shaping filters comprise an explicit coded modulation for which we seek the optimal design we simultaneously constrain the bandwidth and maximize the minimum euclidean distance between signals we show that under quite general assumptions the problem can be formulated as a linear program and solved with well known efficient optimization techniques numerical results are presented and the performance of the optimal signals measured by their combined bandwidth and noise immunity is analyzed the new codes are comparable to set partition tcm trellis codes tests of an m algorithm decoder confirm this and show that the performance occurs at small detection complexity

level set based deformation methods for adaptive grids a new method for generating adaptive moving grids is formulated based on physical quantities level set functions are used to construct the adaptive grids which are solutions of the standard level set evolution equation with the cartesian coordinates as initial values the intersection points of the level sets of the evolving functions form a new grid at each time the velocity vector in the evolution equation is chosen according to a monitor function and is equal to the node velocity a uniform grid is then deformed to a moving grid with desired cell volume distribution at each time the method achieves precise control over the jacobian determinant of the grid mapping as the traditional deformation method does the new method is consistent with the level set approach to dynamic moving interface problems

nonlinear techniques for the joint estimation of cochannel signals cochannel interference occurs when two or more signals overlap in frequency and are present concurrently unlike in spread spectrum multiple access systems where the different users necessarily share the same channel cochannel interference is a severe hindrance to frequency and time division multiple access communications and is typically minimized by interference rejection suppression techniques rather than using interference suppression we are interested in the joint estimation of the information bearing narrow band cochannel signals novel joint estimators are proposed that employ a single input demodulator with oversampling to compensate for timing uncertainties assuming finite impulse response channel characteristics maximum likelihood ml and maximum a posteriori map criteria are used to derive cochannel detectors of varying complexities and degrees of performance in particular a suboptimal two stage joint map symbol detector jmapsd is introduced that has a lower complexity than the single stage estimators while accruing only a marginal loss in error rate performance at high signal to interference ratios assuming only reliable estimates of the primary and secondary signal powers a blind adaptive jmapsd algorithm for a priori unknown channels is also derived the performance of these nonlinear joint estimation algorithms is studied through example computer simulations for two cochannel sources

non binary and precoded faster than nyquist signaling faster than nyquist ftn signaling is an important method of narrowband coding the concept is extended here to non binary signal constellations these are much more bandwidth efficient than binary ones a powerful method of finding the minimum distance for binary and non binary ftn is presented preceding ftn transmissions with short linear filters proves to be an effective way to gain distance a shannon limit to bit error rate is derived that applies for ftn tests of an m algorithm receiver are performed and compared to this limit

reduced complexity sequence estimation using state partitioning a reduced state sequence estimator rsse for linear dispersive channels is described the technique is based on partitioning the set of all channel states in a way that defines a trellis with fewer states the new technique generalizes trellises that were previously obtained by duel hallen and heegard 1989 and eyouboglu and qureshi 1988 while the approach followed by duel hallen results in powers of two state trellises the new technique generates trellises with an arbitrary number of states using the state partitioning approach one could also generalize the trellises obtained by eyouboglu therefore the approach described in this paper provides a better performance complexity tradeoff

sequential decoding of convolutional codes in channels with intersymbol interference sequential sequence estimation for communications channels with convolutionally coded input sequences and intersymbol interference isi is proposed the receiver consists of a whitened matched filter wmf and a vector sequential decoder the metric of the vector sequential algorithm sa is derived analytical results for error probability and computational complexity of the sequential decoder are presented the error probability is found to be dominated by the minimum euclidean distance between the possible output sequences and the computational distribution is pareto typical of a sequential decoder the computational cut off code rate r sub comp and its lower bound r sub comp are also derived numerical simulation results of the error probability and the computational complexity are presented comparing with the viterbi algorithm va reveals that the sa essentially has the same error performance as that of the va while its average computational complexity is one to two orders of magnitude less than that of the va

adaptive grid generation based onthe least squares finite element method approximate solutions of a partial differential equation become inaccurate if they arecomputed on a fixed grid that is not sufficiently fine in regions of the domain where the variables change rapidly for time dependent problems special features of a partial differential equation and their location could change in time as well thus adaptive grid methods are necessary in this paper we develop an adaptive deformation method based on the least squares finite element method lsfem a main advantage of this method as compared to the existing deformation method is its ability to generate adaptive grids on domains with moving boundary it computes the node velocity from a div curl system according to an error indicator monitor function and then moves the nodes to new locations so that the size of the new grid cells can be directly controlled in this method the connectivity of the nodes is unchanged if the grid quality is acceptable otherwise various optimization procedures can be applied after node movements to improve grid quality the grid formed becomes refined in regions where the solution error is large

a unified framework for tree search decoding rediscovering the sequential decoder we consider receiver design for coded transmission over linear gaussian channels we restrict ourselves to the class of lattice codes and formulate the joint detection and decoding problem as a closest lattice point search clps here a tree search framework for solving the clps is adopted in our framework the clps algorithm is decomposed into the preprocessing and tree search stages the role of the preprocessing stage is to expose the tree structure in a form matched to the search stage we argue that the forward and feedback matrix filters of the minimum mean square error decision feedback equalizer mmse dfe are instrumental for solving the joint detection and decoding problem in a single search stage it is further shown that mmse dfe filtering allows for solving underdetermined linear systems and using lattice reduction methods to diminish complexity at the expense of a marginal performance loss for the search stage we present a generic method based on the branch and bound bb algorithm and show that it encompasses all existing sphere decoders as special cases the proposed generic algorithm further allows for an interesting classification of tree search decoders sheds more light on the structural properties of all known sphere decoders and inspires the design of more efficient decoders in particular an efficient decoding algorithm that resembles the well known fano sequential decoder is identified the excellent performance complexity tradeoff achieved by the proposed mmse dfe fano decoder is established via simulation results and analytical arguments in several multiple input multiple output mimo and intersymbol interference isi scenarios

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

accuracy thresholds of topological color codes on the hexagonal and square octagonal lattices accuracy thresholds of quantum error correcting codes which exploit topological properties of systems defined on two different arrangements of qubits are predicted we study the topological color codes on the hexagonal lattice and on the square octagonal lattice by the use of mapping into the spin glass systems the analysis for the corresponding spin glass systems consists of the duality and the gauge symmetry which has succeeded in deriving locations of special points which are deeply related with the accuracy thresholds of topological error correcting codes we predict that the accuracy thresholds for the topological color codes would be 1 ensuremath p c 0 1096 8 for the hexagonal lattice and 1 ensuremath p c 0 1092 3 for the square octagonal lattice where 1 ensuremath p denotes the error probability on each qubit hence both of them are expected to be slightly lower than the probability 1 ensuremath p c 0 110 text 028 for the quantum gilbert varshamov bound with a zero encoding rate

multicritical points for spin glass models on hierarchical lattices the locations of multicritical points on many hierarchical lattices are numerically investigated by the renormalization group analysis the results are compared with an analytical conjecture derived by using the duality the gauge symmetry and the replica method we find that the conjecture does not give the exact answer but leads to locations slightly away from the numerically reliable data we propose an improved conjecture to give more precise predictions of the multicritical points than the conventional one this improvement is inspired by a different point of view coming from the renormalization group and succeeds in deriving very consistent answers with many numerical data doi 10 1103 physreve 77 061116

a soft output hybrid algorithm for ml map sequence estimation the classical viterbi algorithm ml sequence estimation can be computed using a forward backward structure similar to that of the classical hidden markov model forward backward algorithm map state estimation this similarity is exploited to develop a hybrid algorithm which provides a mathematical connection between ml sequence estimation and map state estimation

multicritical nishimori point in the phase diagram of the j ising model on a square lattice we investigate the critical behavior of the random bond j ising model on a square lattice at the multicritical nishimori point in the t p phase diagram where t is the temperature and p is the disorder parameter p 1 corresponds to the pure ising model we perform a finite size scaling analysis of high statistics monte carlo simulations along the nishimori line defined by 2p 1 tanh 1 t along which the multicritical point lies the multicritical nishimori point is located at p 0 890 81 7 t 0 9528 4 and the renormalization group dimensions of the operators that control the multicritical behavior are y 1 0 655 15 and y 2 0 250 2 they correspond to the thermal exponent nu identical with1 y 2 4 00 3 and to the crossover exponent phi identical withy 1 y 2 2 62 6

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

strong disorder paramagnetic ferromagnetic fixed point in the square lattice j ising model we consider the random bond j ising model on a square lattice as a function of the temperature t and of the disorder parameter p p 1 corresponds to the pure ising model we investigate the critical behavior along the paramagnetic ferromagnetic transition line at low temperatures below the temperature of the multicritical nishimori point at t 0 9527 1 p 0 89083 3 we present finite size scaling analyses of monte carlo results at two temperature values t 0 645 and t 0 5 the results show that the paramagnetic ferromagnetic transition line is reentrant for t t that the transitions are continuous and controlled by a strong disorder fixed point with critical exponents 1 50 4 0 128 8 and 0 095 5 this fixed point is definitely different from the ising fixed point controlling the paramagnetic ferromagnetic transitions for t t our results for the critical exponents are consistent with the hyperscaling relation 2 d 2 0

reduced complexity soft mimo detection based on causal and noncausal decision feedback we present a reduced complexity soft detection rcsd scheme geared to multiple input multiple output mimo systems with spatial domain multiplexing leading to layered space time or space frequency architecture the proposed algorithm relies on a trellis representation of the mimo signals and a subsequent formulation of constrained depth maximum a posterior map detection in conjunction with soft decision feedback sdf decision feedback is broken into causal and noncausal parts in an effort to maximize the observation window while maintaining a reasonable computational load two variations of rcsd are proposed to utilize the noncausal information in different ways analysis based on mean squared error mse and log likelihood ratio llr associated with symbols in different stages of the trellis is done to develop insight into error propagation in the rcsd algorithm as well as to compare the quality of the soft information obtained by the two rcsd variants error rate simulations are conducted in the context of turbo like iterative demapping and decoding idd the resulting performance and required complexity are compared with those of maximum a posterior map detection soft sphere detection sd as well as the turbo blast processing scheme we observe favorable performance complexity tradeoffs with the proposed soft detection scheme for a number of modulation channel scenarios

locations of multicritical points for spin glasses on regular lattices we present an analysis leading to precise locations of the multicritical points for spin glasses on regular lattices the conventional technique for determination of the location of the multicritical point was previously derived using a hypothesis emerging from duality and the replica method in the present study we propose a systematic technique by an improved technique giving more precise locations of the multicritical points on the square triangular and hexagonal lattices by carefully examining the relationship between two partition functions related with each other by the duality we can find that the multicritical points of the ifmmode pm else textpm fi j ising model are located at p c 0 890 phantom rule 0 2em 0ex 813 on the square lattice where p c means the probability of j ij j g0 at p c 0 835 phantom rule 0 2em 0ex 985 on the triangular lattice and at p c 0 932 phantom rule 0 2em 0ex 593 on the hexagonal lattice these results are in excellent agreement with recent numerical estimations

symmetry complexity and multicritical point of the two dimensional spin glass we analyse models of spin glasses on the two dimensional square lattice by exploiting symmetry arguments the replicated partition functions of the ising and related spin glasses are shown to have many remarkable symmetry properties as functions of the edge boltzmann factors it is shown that the applications of homogeneous and hadamard inverses to the edge boltzmann matrix indicate reduced complexities when the elements of the matrix satisfy certain conditions suggesting that the system has special simplicities under such conditions using these duality and symmetry arguments we present a conjecture on the exact location of the multicritical point in the phase diagram

generation of curvilinear coordinates on multiply connected regions with boundary singularities a new algorithm to generate smooth two dimensional boundary conforming coordinates with grid lines control on multiply connected regions including boundary singularities is devised the technique fits into the category of elliptic grid generators since it is based on the numerical solution of poisson equations the physical domain d is transformed into a topologically equivalent connected rectangular domain d by defining a branch cut inside d control of the grid line spacing over the multiply connected regions is established by appropriately distributing nodal points on the branch cut and on other boundary curves simple and computationally convenient expressions for the control functions present in the poisson system are obtained from this initial distribution of points thus a natural link between clustering properties and the control functions is created fixing the nodal points on the branch cut causes the convergence of the numerical method about the singular boundary points an iterative smoothing process relocating the branch cut is described as a result smooth grids are obtained grid quality analysis shows that coordinate line orthogonality in the new meshes is superior than in similar grids obtained from a well known commercial software the algorithm is successfully tested over a variety of multiply connected domains the computational advantage of this novel grids is revealed by using them to numerically model the vibrations of complexly shaped annular membranes

asymptotic error performance of modulation codes in the presence of severe intersymbol interference the minimum distance and hence the asymptotic error probability of trellis modulation codes that have been subjected to severe channel filtering are evaluated a general algorithm is proposed for this purpose and applied to one class of coded modulations using a frequency domain interpretation of the euclidean distance it is shown that under extreme channel band limitations the error event that causes the minimum distance is characterized by a spectral null at dc numerical results show that for filtered continuous phase modulation codes decreasing the modulation index or smoothing the frequency pulse does not improve the error performance for some of these modulations channel filtering can actually improve the minimum distance bandpass and low pass filtering are contrasted the numerical results are explained by power spectrum considerations

duality with real space renormalization and its application to bond percolation we obtain the exact solution of the bond percolation thresholds with inhomogeneous probabilities on the square lattice our method is based on the duality analysis with real space renormalization which is a profound technique invented in the spin glass theory our formulation is a more straightforward way than that of a very recent study on the same problem r m ziff et al j phys a math theor 45 494005 2012 the resultant generic formulas from our derivation can give several estimations for the bond percolation thresholds on other lattices rather than the square lattice

an adaptive grid method and its application to steady euler flow calculations an adaptive remeshing procedure based on a cell volume deformation method is presented starting with an initial grid this method offers direct cell volume control through the specification of the transformation jacobian grid points are moved with appropriate grid velocities so that the specified cell volume distribution can be achieved at the end of the grid movement without adding or removing grid points the grid velocities are determined by solving a scalar poisson equation this method is applied to solving the compressible euler equations computational test cases of transonic flow over an airfoil are presented and demonstrate the desired control of grid sizes across shock waves

novel reduced state bcjr algorithms bcjr algorithm is an exact and efficient algorithm to compute the marginal posterior distributions of state variables and pairs of consecutive state variables of a trellis structure due to its overwhelming complexity reduced complexity variations such as the m bcjr algorithm have been developed in this paper we propose improvements upon the conventional m bcjr algorithm based on modified active state selection criteria we propose selecting the active states based on estimates of the fixed lag smoothed distributions of the state variables we also present gaussian approximation techniques for the low complexity estimation of these fixed lag smoothed distributions the improved performance over the m bcjr algorithm is shown via computer simulations

moving meshes by the deformation method in this paper we describe the deformation method for generation of moving meshes and its applications in computational fluid dynamics cfd and potential applications for image representation segmentation and landmark matching for image registration we demonstrate that the deformation method can generate meshes of prescribed cell area numerical examples are presented to confirm that

duality analysis on random planar lattices the conventional duality analysis is employed to identify a location of a critical point on a uniform lattice without any disorder in its structure in the present study we deal with the random planar lattice which consists of the randomized structure based on the square lattice we introduce the uniformly random modification by the bond dilution and contraction on a part of the unit square the random planar lattice includes the triangular and hexagonal lattices in extreme cases of a parameter to control the structure a modern duality analysis fashion with real space renormalization is found to be available for estimating the location of the critical points with a wide range of the randomness parameter as a simple test bed we demonstrate that our method indeed gives several critical points for the cases of the ising and potts models and the bond percolation thresholds on the random planar lattice our method leads to not only such an extension of the duality analyses on the classical statistical mechanics but also a fascinating result associated with optimal error thresholds for a class of quantum error correction code the surface code on the random planar lattice which is known as a skillful technique to protect the quantum state

duality in finite dimensional spin glasses we present an analysis leading to a conjecture on the exact location of the multicritical point in the phase diagram of spin glasses in finite dimensions the conjecture in satisfactory agreement with a number of numerical results was previously derived using an ansatz emerging from duality and the replica method in the present paper we carefully examine the ansatz and reduce it to a hypothesis on analyticity of a function appearing in the duality relation thus the problem is now clearer than before from a mathematical point of view the ansatz somewhat arbitrarily introduced previously has now been shown to be closely related to the analyticity of a well defined function

sequential sequence estimation for multiple channel systems with intersymbol and interchannel interference a vector sequential sequence estimator is proposed for multiple channel systems with both intersymbol interference isi and interchannel interference ici both finite isi ici and infinite isi ici are considered the estimator consists of a multiple dimensional whitened matched filter and a vector sequential decoder the metric of the sequential algorithm is derived and the algorithm s performance is analyzed computer simulation results for a two dimensional finite isi ici channel and a two dimensional infinite isi ici channel are presented analysis and simulation show that the symbol error probability of the vector sequential algorithm is essentially the same as for maximum likelihood sequence estimation using the vector viterbi algorithm while its average computational complexity is much less although computation per symbol is a random variable with the pareto distribution there exists a signal to noise ratio above which the ensemble average computation is bounded an upper bound on this ratio is found

an efficient dfe a ml suboptimum receiver for data transmission over dispersive channels using two dimensional signal constellations the dfe ml receiver is presented for data transmission systems using qam modulation a substantial improvement in performance results as compared to other one or two stage receiver structures at relatively low computational complexity

mathematical and numerical analysis of a robust and efficient grid deformation method in the finite element context among a variety of grid deformation methods the method proposed by bochev liao and de la pena methods partial differential equations 12 1996 pp 489 506 cai et al comput math appl 48 2004 pp 1077 1086 and liao and anderson appl anal 44 1992 pp 285 298 is one of the most favorable because it prevents mesh tangling and offers precise control over the element volumes its numerical realization requires only solving a poisson problem and a system of fully decoupled initial value problems many other deformation methods in contrast involve the solution of complicated nonlinear partial differential equations pdes in this article we introduce a generalization of liao s method which allows for generating a desired mesh size distribution for quite arbitrary grids without giving rise to mesh tangling we elaborate on its numerical realization and prove the convergence of our method our results are confirmed by numerical experiments

nonequilibrium relaxation study on spin glass model ferromagnetic fm transition point and universality class of the j ising model on cubic lattice are studied by computer simulation using the nonequilibrium relaxation ner method at fm bond density p between multicritical one pmc and 1 static exponents take universal values which are different from those of p 1 or p pmc and they are consistent with the values of the random fixed point and of the simulations and experiments for diluted ising systems the dynamical exponent however seems to depend on p and not to be universal although it may be due to finite time correction the estimation of pmc on square lattice is also refined to be 0 8894 9 which is consistent with the nishimori and nemoto s conjecture 0 889972

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

maximum likelihood sequence estimation from the lattice viewpoint considers the problem of data detection in multilevel lattice type modulation systems in the presence of intersymbol interference and additive white gaussian noise the conventional maximum likelihood sequence estimator using the viterbi algorithm has a time complexity of o m sup spl nu 1 operations per symbol and a space complexity of o spl delta m sup spl nu storage elements where m is the size of input alphabet spl nu is the length of channel memory and spl delta is the truncation depth by revising the truncation scheme and viewing the channel as a linear transform the authors identify the problem of maximum likelihood sequence estimation with that of finding the nearest lattice point from this lattice viewpoint the lattice sequence estimator for pam systems is developed which has the following desired properties 1 its expected time complexity grows as spl delta sup 2 as snr spl rarr spl infin 2 its space complexity grow as spl delta and 3 its error performance is effectively optimal for sufficiently large m a tight upper bound on the symbol error probability of the new estimator is derived and is confirmed by the simulation results of an example channel it turns out that the estimator is effectively optimal for m spl ges 4 and the loss in signal to noise ratio is less than 0 5 db even for m 2 finally limitations of the proposed estimator are also discussed

phase diagram and critical exponents of a potts gauge glass the two dimensional q state potts model is subjected to a z q symmetric disorder that allows for the existence of a nishimori line at q 2 this model coincides with the j random bond ising model for q 2 apart from the usual pure and zero temperature fixed points the ferro paramagnetic phase boundary is controlled by two critical fixed points a weak disorder point whose universality class is that of the ferromagnetic bond disordered potts model and a strong disorder point which generalizes the usual nishimori point we numerically study the case q 3 tracing out the phase diagram and precisely determining the critical exponents the universality class of the nishimori point is inconsistent with percolation on potts clusters