In Network-on-Chip (NoC) based multi-core platforms, Distributed Shared Memory (DSM) preferably uses virtual addressing in order to hide the physical locations of the memories. However, this incurs performance penalty...
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In Network-on-Chip (NoC) based multi-core platforms, Distributed Shared Memory (DSM) preferably uses virtual addressing in order to hide the physical locations of the memories. However, this incurs performance penalty due to the Virtual-to-Physical (V2P) address translation overhead for all memory accesses. Based on the data property which can be either private or shared, this paper proposes a hybrid DSM which partitions a local memory into a private and a shared part. The private part is accessed directly using physical addressing and the shared part using virtual addressing. In particular, the partitioning boundary can be configured statically at design time and dynamically at runtime. The dynamic configuration further removes the V2P address translation overhead for those data with changeable property when they become private at runtime. In the experiments with three applications (matrix multiplication, 2D FFT, and H.264/AVC encoding), compared with the conventional DSM, our techniques show performance improvement up to 37.89%. (C) 2012 Elsevier Ltd. All rights reserved.
This paper describes our approach to support the development of large-scale Web applications. Large development efforts have to be divided into a number of smaller tasks of different kinds that can be performed by mul...
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This paper describes our approach to support the development of large-scale Web applications. Large development efforts have to be divided into a number of smaller tasks of different kinds that can be performed by multiple developers. Once this process has taken place, it is important to manage the consistency among the artifacts in an efficient and systematic manner. Our model-driven approach makes this possible. In this paper, we discuss how a metamodel is used to describe part of the specification as a central contract among the developers. We also describe a tool that we implemented on the basis of the metamodel. The tool provides a variety of code generators and a mechanism for checking whether view artifacts, such as JavaServer Pages(TM), are compliant with the model. This feature helps developers manage the consistency between a view artifact and the related business logic-HyperText Transfer Protocol request handlers.
Seismic data volumes, which require huge transmission capacities and massive storage media, continue to increase rapidly due to acquisition of 3D and 4D multiple streamer surveys, multicomponent data sets, reprocessin...
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Seismic data volumes, which require huge transmission capacities and massive storage media, continue to increase rapidly due to acquisition of 3D and 4D multiple streamer surveys, multicomponent data sets, reprocessing of prestack seismic data, calculation of post-stack seismic data attributes, etc. We consider lossy compression as an important tool for efficient handling of large seismic data sets. We present a 2D lossy seismic data compression algorithm, based on sub-band coding, and we focus on adaptation and optimization of the method for common-offset gathers. The sub-band coding algorithm consists of five stages: first, a preprocessing phase using an automatic gain control to decrease the non-stationary behaviour of seismic data;second, a decorrelation stage using a uniform analysis filter bank to concentrate the energy of seismic data into a minimum number of sub-bands;third, an iterative classification algorithm, based on an estimation of variances of blocks of sub-band samples, to classify the sub-band samples into a fixed number of classes with approximately the same statistics;fourth, a quantization step using a uniform scalar quantizer, which gives an approximation of the sub-band samples to allow for high compression ratios;and fifth, an entropy coding stage using a fixed number of arithmetic encoders matched to the corresponding statistics of the classified and quantized sub-band samples to achieve compression. Decompression basically performs the opposite operations in reverse order. We compare the proposed algorithm with three other seismic data compression algorithms. The high performance of our optimized sub-band coding method is supported by objective and subjective results.
The software for portable systems for obtaining. image with coding apertures (masks) is described. The software developed controls all systems that form an image and obtain shadow patterns, reconstructs the initial ga...
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The software for portable systems for obtaining. image with coding apertures (masks) is described. The software developed controls all systems that form an image and obtain shadow patterns, reconstructs the initial gamma-image, and processes previously obtained images. The software is used with portable systems in which URA and MURA type masks with different rank are used as the coding aperture. Programs for modeling the process of obtaining shadow patterns using real apparatus which has different position-sensitive detectors are described. Possible configurations of new apparatus which could be of practical interest are examined.
This study investigates the effect of multiple sources using STS across a Time-Hopping-PPM Modulation that is over an UWB Saleh-Valenzuela channel with each source using two transmit antennas. We model and analyze thi...
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This study investigates the effect of multiple sources using STS across a Time-Hopping-PPM Modulation that is over an UWB Saleh-Valenzuela channel with each source using two transmit antennas. We model and analyze this system, showing that the presence of such MAI results in a significant degradation in BER performance. Simulation results show that for strong signal strength of interfering MAI signals degradation in BER performance is observed for the cases where we have five and 10 distinct MAI sources present when using Walsh-Hadamard thirty two chip spreading sequences. Using simulation, we investigate the use of other sets of orthogonal spreading sequences with improved cross correlation properties and find that for some sequences a significant improvement is seen compared to Walsh-Hadamard sequences when they are similarly misaligned. We show that MAI degrades the BER performance of such systems and that selection of improved cross correlation spreading code sequence sets improves BER. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
We provide an explicit construction for a complete set of orthogonal primitive idempotents of finite group algebras over nilpotent groups. Furthermore, we give a complete set of matrix units in each simple epimorphic ...
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We provide an explicit construction for a complete set of orthogonal primitive idempotents of finite group algebras over nilpotent groups. Furthermore, we give a complete set of matrix units in each simple epimorphic image of a finite group algebra of a nilpotent group. (C) 2010 Elsevier Inc. All rights reserved.
We study coding schemes for multiparty interactive communication over synchronous networks that suffer from stochastic noise, where each bit is independently flipped with probability epsilon. We analyze the minimal ov...
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We study coding schemes for multiparty interactive communication over synchronous networks that suffer from stochastic noise, where each bit is independently flipped with probability epsilon. We analyze the minimal overhead that must be added by the coding scheme to succeed in performing the computation despite the noise. Our main result is a lower bound on the communication of any noise-resilient protocol over a synchronous star network with n parties (where all parties communicate in every round). Specifically, we show a task that can be solved by communicating T bits over the noise-free network, but for which any protocol with success probability of 1 - o(1) must communicate at least Omega(T log n/log log n) bits when the channels are noisy. By a 1994 result of Rajagopalan and Schulman, the slowdown we prove is the highest one can obtain on any topology, up to a log log n factor. We complete our lower bound with a matching coding scheme that achieves the same overhead;thus, the capacity of (synchronous) star networks is Theta(log log n/log n). Our bounds prove that, despite several previous coding schemes with rate Omega(1) for certain topologies, no coding scheme with constant rate Omega(1) exists for arbitrary n-party noisy networks.
In this paper, we give an explicit construction of a family of capacity-achieving binary t-write WOM codes for any number of writes t, which have polynomial time encoding and decoding algorithms. The block length of o...
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In this paper, we give an explicit construction of a family of capacity-achieving binary t-write WOM codes for any number of writes t, which have polynomial time encoding and decoding algorithms. The block length of our construction is N = (t/epsilon)(O(t/(delta epsilon))) when epsilon is the gap to capacity and encoding and decoding run in time N1+ delta. This is the first deterministic construction achieving these parameters. Our techniques also apply to larger alphabets.
The validation of thermal hydraulic system codes like TRACE is a demanding and highly needed task for the nuclear engineering community. In the present paper the validation of TRACE is focused on the heat transfer enh...
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The validation of thermal hydraulic system codes like TRACE is a demanding and highly needed task for the nuclear engineering community. In the present paper the validation of TRACE is focused on the heat transfer enhancement models for spacer grids. Several test sections are selected for that purpose whereas several coolants, different rod arrangements and dimensions, and various thermal hydraulic boundary conditions are considered. The systematic evaluation by means of post-test calculations shows that the present TRACE model is well able to represent the magnitude of the heat transfer enhancement directly at the spacer grid. Nevertheless, improvements of the model were necessary in order to catch the enhancement downstream of the spacer grid. With the present model, the exponential decay of the enhancement is over estimated. The comparison with experimental data suggests a faster establishment of the fully developed flow. Adjustments to the model are done in order to represent the data correctly in terms of magnitude and duration. (C) 2013 Elsevier B.V. All rights reserved.
Let C be a binary linear block code of length n, dimension k and minimum Hamming distance d over GF(2)(n). Let d(perpendicular to) denote the minimum Hamming distance of the dual code of C over GF(2)(n). Let epsilon :...
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Let C be a binary linear block code of length n, dimension k and minimum Hamming distance d over GF(2)(n). Let d(perpendicular to) denote the minimum Hamming distance of the dual code of C over GF(2)(n). Let epsilon : GF(2)(n) bar right arrow {-1, 1}(n) be the component-wise mapping epsilon(v(i)):=(-1)(vi), for v = (v(1), v(2), ..., v(n)) is an element of GF(2)(n). Finally, for p < n, let Phi(C) be a p x n random matrix whose rows are obtained by mapping a uniformly drawn set of size p of the codewords of C under epsilon. It is shown that for d(perpendicular to) large enough and y:=p/n is an element of (0, 1) fixed, as n -> infinity the empirical spectral distribution of the Gram matrix of 1/root n Phi(C) resembles that of a random i.i.d. Rademacher matrix (i.e., the Marchenko-Pastur distribution). Moreover, an explicit asymptotic uniform bound on the distance of the empirical spectral distribution of the Gram matrix of 1/root n Phi(C) to the Marchenko-Pastur distribution as a function of y and d(perpendicular to) is presented.
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