This special issue contains a selection of seven papers from the 18th Annual International Computing and Combinatorics Conference (COCOON), held during August 20-22, 2012, in Sydney Australia. The conference program f...
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This special issue contains a selection of seven papers from the 18th Annual International Computing and Combinatorics Conference (COCOON), held during August 20-22, 2012, in Sydney Australia. The conference program featured 50 presentations chosen from 121 submissions, covering a wide range of topics related to theoretical aspects of computing. This is reflected by the seven papers selected for the special issue whose topics range from clustering to circuit lower bounds. The papers were invited based on their evaluation by the COCOON 2012 program committee, and went through the standard rigorous refereeing process of Algorithmica before being accepted to this special issue.
Questions concerning textual referentiality figure among the most controversial in literary theory. The complementarity of semiotic and marxist notions of the literary referent suggests a new understanding of the refe...
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Questions concerning textual referentiality figure among the most controversial in literary theory. The complementarity of semiotic and marxist notions of the literary referent suggests a new understanding of the referent based on the concept of “cultural unit.” The similarity in the relations that marxist epistemology (as defined by Althusser) posits between thought and the real and that semiotics (as defined by Eco) posits between language and the real warrants this reformulation. A discussion of the semiotic and marxist concepts necessary for a theory of the literary referent leads to its definition as a cultural ideological unit that, by virtue of its necessary but unrepresented relation to other, nonidentical cultural units, furnishes in the mode of a dialectical absence the materials requisite for an understanding both of certain textual properties and of the structure of the historical reality to which the text alludes.
Hooker addresses the objection that complying with conventionally accepted norms is at least sometimes right even if they are less than ideal. Hooker argues that ideal code theory can itself contend that compromising...
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Hooker addresses the objection that complying with conventionally accepted norms is at least sometimes right even if they are less than ideal. Hooker argues that ideal code theory can itself contend that compromising with convention is sometimes right.
We investigate effective noise channels for encoded quantum systems with and without active error correction. Noise acting on physical qubits forming a logical qubit is thereby described as a logical noise channel act...
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We investigate effective noise channels for encoded quantum systems with and without active error correction. Noise acting on physical qubits forming a logical qubit is thereby described as a logical noise channel acting on the logical qubits, which leads to a significant decrease of the effective system dimension. This provides us with a powerful tool to study entanglement features of encoded quantum systems. We demonstrate this framework by calculating lower bounds on the lifetime of distillable entanglement and the negativity for encoded multipartite qubit states with different encodings. At the same time, this approach leads to a simple understanding of the functioning of (concatenated) error correction codes.
Wireless Sensor Networks (WSNs) are composed of small wireless nodes equipped with sensors, a processor, and a radio communication unit, all normally powered by batteries. For most WSN applications, the network is exp...
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Wireless Sensor Networks (WSNs) are composed of small wireless nodes equipped with sensors, a processor, and a radio communication unit, all normally powered by batteries. For most WSN applications, the network is expected to function for several months or years. In the common monitoring application scenario, adjacent nodes in a WSN often sense spatially correlated data. Suppressing this correlation can significantly improve the lifetime of the network. The maximum possible network data compression can be achieved using distributed source coding (DSC) techniques when nodes encode at Slepian-Wolf rates. This paper presents contributions to the lifetime optimization problem of WSNs in the form of two algorithms: the Updated-CMAX (UCMAX) power-aware routing algorithm to optimize the routing tree and the Rate Optimization (RO) algorithm to optimize the encoding rates of the nodes. The two algorithms combined offer a solution that maximizes the lifetime of a WSN measuring spatially correlated data. Simulations show that our proposed approach may significantly extend the lifetime of multihop WSNs with nodes that are observing correlated data.
Original images are often compressed for the communication applications. In order to avoid the burden of decompressing computations, it is thus desirable to segment images in the compressed domain directly. This paper...
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Original images are often compressed for the communication applications. In order to avoid the burden of decompressing computations, it is thus desirable to segment images in the compressed domain directly. This paper presents a simple rate-distortion-based scheme to segment images in the JPEG2000 domain. It is based on a binary arithmetic code table used in the JPEG2000 standard, which is available at both encoder and decoder;thus, there is no need to transmit the segmentation result. Experimental results on the Berkeley image database show that the proposed algorithm is preferable in terms of the running time and the quantitative measures: probabilistic Rand index (PRI) and boundary displacement error (BDE).
Finding the densest sphere packing in d-dimensional Euclidean space Rd is an outstanding fundamental problem with relevance in many fields, including the ground states of molecular systems, colloidal crystal structure...
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Finding the densest sphere packing in d-dimensional Euclidean space Rd is an outstanding fundamental problem with relevance in many fields, including the ground states of molecular systems, colloidal crystal structures, coding theory, discrete geometry, number theory, and biological systems. Numerically generating the densest sphere packings becomes very challenging in high dimensions due to an exponentially increasing number of possible sphere contacts and sphere configurations, even for the restricted problem of finding the densest lattice sphere packings. In this paper we apply the Torquato-Jiao packing algorithm, which is a method based on solving a sequence of linear programs, to robustly reproduce the densest known lattice sphere packings for dimensions 2 through 19. We show that the TJ algorithm is appreciably more efficient at solving these problems than previously published methods. Indeed, in some dimensions, the former procedure can be as much as three orders of magnitude faster at finding the optimal solutions than earlier ones. We also study the suboptimal local density-maxima solutions (inherent structures or “extreme” lattices) to gain insight about the nature of the topography of the “density” landscape.
This paper considers quantum network coding, which is a recent technique that enables quantum information to be sent on complex networks at higher rates than straightforward routing strategies. Kobayashi et al. have r...
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This paper considers quantum network coding, which is a recent technique that enables quantum information to be sent on complex networks at higher rates than straightforward routing strategies. Kobayashi et al. have recently showed the potential of this technique by demonstrating how any classical network coding protocol gives rise to a quantum network coding protocol. They nevertheless primarily focused on an abstract model, in which quantum resources such as additional quantum registers can be freely introduced at each node. In this work, we present a protocol for quantum network coding under weaker (and more practical) assumptions: Our new protocol works even for quantum networks where adjacent nodes initially share one Einstein-Podolsky-Rosen pair but cannot add any additional quantum registers or send any quantum information. A typical example of networks satisfying this assumption is quantum repeater networks, which are promising candidates for the implementation of large-scale quantum networks. Our results thus show that quantum network coding techniques can increase the transmission rate in such quantum networks as well.
Time-varying codes associate variable length code words to letters being encoded depending on their positions in the input string. These codes have been introduced in [8] as a proper extension of L codes. This paper i...
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Time-varying codes associate variable length code words to letters being encoded depending on their positions in the input string. These codes have been introduced in [8] as a proper extension of L codes. This paper is devoted to a further study of time-varying codes. First, we show that adaptive Huffman encodings are special cases of encodings by time-varying codes. Then, we focus on three kinds of characterization results: characterization results based on decompositions over families of sets of words, a Schutzenberger like criterion, and a Sardinas-Patterson like characterization theorem. All of them extend the corresponding characterization results known for classical variable length codes.
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