By minimising the pairwise error probability (PEP) bound subject to the fixed power constraint, a suboptimal precoding scheme for space-time block-coded multiple-input-multiple-output (STBC-MIMO) systems with mean and...
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By minimising the pairwise error probability (PEP) bound subject to the fixed power constraint, a suboptimal precoding scheme for space-time block-coded multiple-input-multiple-output (STBC-MIMO) systems with mean and covariance feedback in spatially correlated Rayleigh fading channels is developed, which can include the mean-feedback only and covariance-feedback only as its special cases. This scheme can achieve performances close to the existing optimal scheme while being more computationally efficient. The simulation results show that the proposed scheme can provide better performances than the conventional equal power scheme, and achieve almost the same performances as the existing optimal scheme.
Language is one of the central metaphors around which the discipline of computer science has been built. The language metaphor entered modern computing as part of a cybernetic discourse, but during the second half of ...
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Language is one of the central metaphors around which the discipline of computer science has been built. The language metaphor entered modern computing as part of a cybernetic discourse, but during the second half of the 1950s acquired a more abstract meaning, closely related to the formal languages of logic and linguistics. The article argues that this transformation was related to the appearance of the commercial computer in the mid-1950s. Managers of computing installations and specialists on computer programming in academic computer centers, confronted with an increasing variety of machines, called for the creation of “common” or “universal languages” to enable the migration of computer code from machine to machine. Finally, the article shows how the idea of a universal language was a decisive step in the emergence of programming languages, in the recognition of computer programming as a proper field of knowledge, and eventually in the way we think of the computer.
The efficient coding hypothesis posits that sensory systems maximize information transmitted to the brain about the environment. We develop a precise and testable form of this hypothesis in the context of encoding a s...
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The efficient coding hypothesis posits that sensory systems maximize information transmitted to the brain about the environment. We develop a precise and testable form of this hypothesis in the context of encoding a sensory variable with a population of noisy neurons, each characterized by a tuning curve. We parameterize the population with two continuous functions that control the density and amplitude of the tuning curves, assuming that the tuning widths vary inversely with the cell density. This parameterization allows us to solve, in closed form, for the information-maximizing allocation of tuning curves as a function of the prior probability distribution of sensory variables. For the optimal population, the cell density is proportional to the prior, such that more cells with narrower tuning are allocated to encode higher-probability stimuli and that each cell transmits an equal portion of the stimulus probability mass. We also compute the stimulus discrimination capabilities of a perceptual system that relies on this neural representation and find that the best achievable discrimination thresholds are inversely proportional to the sensory prior. We examine how the prior information that is implicitly encoded in the tuning curves of the optimal population may be used for perceptual inference and derive a novel decoder, the Bayesian population vector, that closely approximates a Bayesian least-squares estimator that has explicit access to the prior. Finally, we generalize these results to sigmoidal tuning curves, correlated neural variability, and a broader class of objective functions. These results provide a principled embedding of sensory prior information in neural populations and yield predictions that are readily testable with environmental, physiological, and perceptual data.
The Sodium-cooled fast neutron reactor ASTRID is currently under design and development in France. Traditional ECCO/ERANOS fast reactor code system used for ASTRID core design calculations relies on multi-group JEFF-3...
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The Sodium-cooled fast neutron reactor ASTRID is currently under design and development in France. Traditional ECCO/ERANOS fast reactor code system used for ASTRID core design calculations relies on multi-group JEFF-3.1.1 data library. To gauge the use of ENDF/B-VII.0 and JEFF-3.1.1 nuclear data libraries in the fast reactor applications, two recent OECD/NEA computational benchmarks specified by Argonne National Laboratory were calculated. Using the continuous-energy TRIPOLI-4 Monte Carlo transport code, both ABR-1000 MWth MOX core and metallic (U-Pu) core were investigated. Under two different fast neutron spectra and two data libraries, ENDF/B-VII. 0 and JEFF-3.1.1, reactivity impact studies were performed. Using JEFF3.1.1 library under the BOEC (Beginning of equilibrium cycle) condition, high reactivity effects of 808 +/- 17 pcm and 1208 +/- 17 pcm were observed for ABR-1000 MOX core and metallic core respectively. To analyze the causes of these differences in reactivity, several TRIPOLI-4 runs using mixed data libraries feature allow us to identify the nuclides and the nuclear data accounting for the major part of the observed reactivity discrepancies.
A subset C C V is an r-identifying code in a graph G = (V E) if the sets I-r(v) = {c is an element of C vertical bar d(c, v) = 15, the optimal density of an r-identifying code is 1/8r(2). The problem finding a minimum...
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A subset C C V is an r-identifying code in a graph G = (V E) if the sets I-r(v) = {c is an element of C vertical bar d(c, v) <= r} are distinct and non-empty for all vertices v subset of V. Here, d(c, v) denotes the number of edges on any shortest path from c to v. We consider the infinite n-dimensional king grid, i.e., the graph with vertex set V = Z(n) and the edge set E = {{x = (x(i), ... , x(n)), y = (y(1), ... , y(n))} vertical bar vertical bar x(i) - y(i)vertical bar <= 1 for i = 1, ... , n, x not equal y}, and give some lower bounds on the density of an r-identifying code. In particular, we prove that for n = 3 and for all r >= 15, the optimal density of an r-identifying code is 1/8r(2). The problem finding a minimum identifying code in the 3-dimensional king grid is equivalent with a minimum packing problem of cubes in the 3-dimensional lattice so that every point is covered by a distinct and non-empty subset of cubes. (C) 2013 Elsevier Ltd. All rights reserved.
We provide a detailed study of the general structure of translationally invariant two-dimensional topological stabilizer quantum error correcting codes, including subsystem codes. We show that they can be understood i...
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We provide a detailed study of the general structure of translationally invariant two-dimensional topological stabilizer quantum error correcting codes, including subsystem codes. We show that they can be understood in terms of the homology of string operators that carry a certain topological charge. In subsystem codes, two dual kinds of charges appear. We prove that two non-chiral codes are equivalent under local transformations iff they have isomorphic topological charges. Our approach emphasizes local properties over global ones.
This paper is motivated by the problem of finding the largest single-deletion-correcting code for binary strings. The Varshamov-Tenengolts construction classifies binary strings into non-overlapping sets, the largest ...
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This paper is motivated by the problem of finding the largest single-deletion-correcting code for binary strings. The Varshamov-Tenengolts construction classifies binary strings into non-overlapping sets, the largest set of these is asymptotically the largest singledeletion-correcting code. However despite the asymptotic optimality little is known about the quality of the construction as a function of the string length. We show that these sets are also responsible for the (near) solution of several combinatorial problems on a certain hypergraph. Furthermore our results are valid for any string length. We show that the sets collectively solve strong vertex coloring and edge coloring on the hypergraph exactly. For any string length n we show that the largest of these sets is within n+1/n-1 of optimal matching on the hypergraph, which also corresponds to the largest single-deletion-correcting code. Moreover, we show for any n the smallest of these sets is within n(2)-n/n(2)-3n+4-4/2(n) of the smallest cover of this hypergraph and that each of these sets is a perfect matching. We then obtain similar results on the dual of this hypergraph. (C) 2013 Elsevier B.V. All rights reserved.
A general strategy was developed to fabricate 2-to-1, 4-to-2 and 8-to-3 molecular encoders and a 1-to-2 decoder by assembling graphene oxide with various dye-labeled DNAs.
A general strategy was developed to fabricate 2-to-1, 4-to-2 and 8-to-3 molecular encoders and a 1-to-2 decoder by assembling graphene oxide with various dye-labeled DNAs.
Multiple input multiple output (MIMO) communication systems along with orthogonal frequency division multiplexing (OFDM) play a key role in designing next generation broadband wireless systems. Recently, low density p...
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Multiple input multiple output (MIMO) communication systems along with orthogonal frequency division multiplexing (OFDM) play a key role in designing next generation broadband wireless systems. Recently, low density parity check codes (LDPC) emerge as a good candidate for error correcting codes with capacity near Shannon's limit. In this study, the authors derive moment generating function- based closed-form upper bounds on the pairwise error probability for serially concatenated LDPC codes with Alamouti coded MIMO-OFDM systems. Also bit error rate expressions are derived for the mentioned concatenation scheme under spatially independent and correlated quasi-static Rayleigh, Rician and Nakagami fading channels. The authors' general framework considers the impact on coding and diversity gains because of spatial, time and frequency correlations, both individually and in combined form. In this study, the authors introduced the coexistence of spatial, time and frequency correlation channel models for proposed concatenation scheme and evaluate its effect on coding and diversity gain. Simulation results show that the proposed concatenation scheme is integrated in such a way that it takes advantage of every individual block. Further, the upper bounds derived in this study matches with the analytical results.
The Maximum Permutation Code Problem (MPCP) is a well-known combinatorial optimization problem in coding theory. The aim is to generate the largest possible permutation codes, having a given length n and a minimum Ham...
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ISBN:
(纸本)9781479935802
The Maximum Permutation Code Problem (MPCP) is a well-known combinatorial optimization problem in coding theory. The aim is to generate the largest possible permutation codes, having a given length n and a minimum Hamming distance d between the codewords. In this paper we present a new branch and bound algorithm, which combines combinatorial techniques with an approach based on group orbits. Computational experiments lead to interesting considerations about the use of group orbits for code generation.
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