1,110 research outputs found

    Time-Space Constrained Codes for Phase-Change Memories

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    Phase-change memory (PCM) is a promising non-volatile solid-state memory technology. A PCM cell stores data by using its amorphous and crystalline states. The cell changes between these two states using high temperature. However, since the cells are sensitive to high temperature, it is important, when programming cells, to balance the heat both in time and space. In this paper, we study the time-space constraint for PCM, which was originally proposed by Jiang et al. A code is called an \emph{(α,β,p)(\alpha,\beta,p)-constrained code} if for any α\alpha consecutive rewrites and for any segment of β\beta contiguous cells, the total rewrite cost of the β\beta cells over those α\alpha rewrites is at most pp. Here, the cells are binary and the rewrite cost is defined to be the Hamming distance between the current and next memory states. First, we show a general upper bound on the achievable rate of these codes which extends the results of Jiang et al. Then, we generalize their construction for (α≥1,β=1,p=1)(\alpha\geq 1, \beta=1,p=1)-constrained codes and show another construction for (α=1,β≥1,p≥1)(\alpha = 1, \beta\geq 1,p\geq1)-constrained codes. Finally, we show that these two constructions can be used to construct codes for all values of α\alpha, β\beta, and pp

    Coding for Two Dimensional Constrained Fields

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    Attention modulates spatial priority maps in the human occipital, parietal and frontal cortices.

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    Computational theories propose that attention modulates the topographical landscape of spatial 'priority' maps in regions of the visual cortex so that the location of an important object is associated with higher activation levels. Although studies of single-unit recordings have demonstrated attention-related increases in the gain of neural responses and changes in the size of spatial receptive fields, the net effect of these modulations on the topography of region-level priority maps has not been investigated. Here we used functional magnetic resonance imaging and a multivariate encoding model to reconstruct spatial representations of attended and ignored stimuli using activation patterns across entire visual areas. These reconstructed spatial representations reveal the influence of attention on the amplitude and size of stimulus representations within putative priority maps across the visual hierarchy. Our results suggest that attention increases the amplitude of stimulus representations in these spatial maps, particularly in higher visual areas, but does not substantively change their size

    A co-designed equalization, modulation, and coding scheme

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    The commercial impact and technical success of Trellis Coded Modulation seems to illustrate that, if Shannon's capacity is going to be neared, the modulation and coding of an analogue signal ought to be viewed as an integrated process. More recent work has focused on going beyond the gains obtained for Average White Gaussian Noise and has tried to combine the coding/modulation with adaptive equalization. The motive is to gain similar advances on less perfect or idealized channels

    Common Boundaries: Moving Toward Coordinated and Sustainable Planning on the Oneida Reservation

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    Comprehensive planning can help communities engage in purposeful and sustainable land use development. Previous research has indicated that Indian reservations in the United States often face unique roadblocks to these planning efforts: checkerboard patterns of tribal and nontribal ownership, and the presence of both tribal and local governments exercising land use authority within the same shared space. These roadblocks can lead to uncooperative, uncoordinated, or unsustainable development. Despite these noted problems, there remains an important gap in the current literature regarding solutions to overcome these roadblocks. The purpose of this study was to address that gap. Guided by Forester\u27s critical planning theory to critically examine the social and historical roots of planning within a particular community, this qualitative case study examined government records and conducted 18 interviews of tribal and local government officials. Data analysis consisted of coding data to reveal emergent themes relating to cooperative land use planning in the future. These themes included: (a) approaching planning with a regional philosophy in mind, (b) strengthening interpersonal relationships, (c) finding ways to fairly compensate each other for government services, (d) continuing to acknowledge each government\u27s ability to govern within this shared space, and (e) refraining from asserting authority over a neighboring government. This research is an important contribution to the existing literature and enhances social change initiatives by providing guidance for tribal and local government officials to increase cooperative land use planning

    Lattice Gaussian Sampling by Markov Chain Monte Carlo: Bounded Distance Decoding and Trapdoor Sampling

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    Sampling from the lattice Gaussian distribution plays an important role in various research fields. In this paper, the Markov chain Monte Carlo (MCMC)-based sampling technique is advanced in several fronts. Firstly, the spectral gap for the independent Metropolis-Hastings-Klein (MHK) algorithm is derived, which is then extended to Peikert's algorithm and rejection sampling; we show that independent MHK exhibits faster convergence. Then, the performance of bounded distance decoding using MCMC is analyzed, revealing a flexible trade-off between the decoding radius and complexity. MCMC is further applied to trapdoor sampling, again offering a trade-off between security and complexity. Finally, the independent multiple-try Metropolis-Klein (MTMK) algorithm is proposed to enhance the convergence rate. The proposed algorithms allow parallel implementation, which is beneficial for practical applications.Comment: submitted to Transaction on Information Theor
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