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Quasi-automatic groups are asynchronously automatic

THEORETICAL COMPUTER SCIENCE 2019年 793卷 193-195页

作者： Blanchette, Benjamin

A quasi-automatic semigroup is a finitely generated semigroup with a rational set of representatives such that the graph of right multiplication by any generator is a rational relation. A asynchronously automatic semigroup is a quasi-automatic semigroup for which these rational relations are also recognisable by two-tape automata. We show that when such a semigroup happens to be a group, the converse actually holds, meaning quasi-automatic groups are asynchronously automatic. (C) 2019 Published by Elsevier B.V.

关键词： Quasi-automatic semigroups Asynchronously automatic groups computation complexity Rational transductions Finite automata

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Alternating total variation and non-local total variation for fast compressed sensing magnetic resonance imaging

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ELECTRONICS LETTERS 2015年第22期51卷 1740-1741页

作者： Hao, Wangli Li, Jianwu Shanxi Agr Univ Sch Software Taigu 030801 Shanxi Peoples R China Beijing Inst Technol Sch Comp Sci & Technol Beijing Key Lab Intelligent Informat Technol Beijing 100081 Peoples R China

Total variance-(TV) based compressed sensing MRI (CS-MRI) reconstruction methods are effective in restoring a magnetic resonance (MR) image structure from undersampled k-space data. However, the local details of MR images are usually oversmoothed such that block effects are easily caused. Fortunately, the problem can be overcome by the non-local total variation (NLTV), which is highly effective in keeping fine details and sharping image edges. Nevertheless, NLTV is not good at finding similar patches. Considering TV and NLTV are complementary, it is proposed to use them alternatively instead of combining them in one objective function for CS-MRI. In one alternation, the objective function containing the TV and the wavelet regularisations is firstly used to build the structure of the reconstructed MR image through running several iterations of the optimisation method and then the objective function including the NLTV and the wavelet constraints is used to remove the blocking effects and to preserve the image details through running only one iteration of the optimisation method. A number of alternations are run to find the final reconstruction image. Experimental results validate the effectiveness of the method regarding both reconstruction accuracy and computation complexity.

关键词： biomedical MRI compressed sensing computational complexity image restoration image sampling iterative methods medical image processing optimisation wavelet transforms alternating total variation block effects computation complexity fast compressed sensing magnetic resonance imaging image edges iteration nonlocal total variation optimisation method reconstruction accuracy restoring magnetic resonance image structure total variance-based compressed sensing MRI reconstruction methods undersampled k-space data wavelet constraints wavelet regularisations

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OPTIMIZED IMPLEMENTATION OF REAL-TIME DISCRETE WIGNER DISTRIBUTION

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ELECTRONICS LETTERS 1989年第11期25卷 706-707页

作者： EILOUTI, HH KHADRA, LM Department of Electrical Engineering Jordan University of Science & Technology Irbid Jordan

In the letter an optimised algorithm for real-time implementation of the discrete Wigner distribution (DWD) is presented. The algorithm makes use of the symmetry properties in the Wigner kernel and computes the analytic signal recursively in the time domain. Its computation complexity is found to be very small compared with the direct implementation of the DWD when real-time processing is needed.

关键词： optimisation optimised algorithm time-domain analysis symmetry properties Optimisation techniques real-time discrete Wigner distribution Wigner kernel time domain Signal processing and detection signal processing computational complexity computation complexity

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Low complexity energy efficient very low bit-rate image compression scheme for wireless sensor network

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INFORMATION PROCESSING LETTERS 2013年第18期113卷 672-676页

作者： Phamila, Asnath Victy Y. Amutha, R. SSN Coll Engn Madras Tamil Nadu India

This paper presents an extremely fast and very low complex energy efficient image compression scheme for resource constrained, low powered devices in real time applications. The proposed Optimal Zonal 2 x 2 BinDCT is unique since it directly extracts and codes the DC Coefficient and the first three AC coefficients of an 8 x 8 image block using only shift-and-add operations. It is specifically designed for the resource constrained image sensor wireless networks requiring very low bitrates and is investigated in terms of image quality, entropy, processing time and overall energy consumption. Experiments are performed using the Atmel ATmega128 processor to measure the computation time and the resultant energy savings. Simulation results show that the proposed algorithm is extremely simple, fast and consumes only 4% of computation energy needed by Independent JPEG Group IJG version and thus prolongs the system lifetime. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Algorithms Discrete cosine transform Image coding computation complexity Real time systems Sensor network

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(Private) Kernelized Bandits with Distributed Biased Feedback

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PROCEEDINGS OF THE ACM ON MEASUREMENT AND ANALYSIS OF COMPUTING SYSTEMS 2023年第1期7卷 1-47页

作者： Li, Fengjiao Zhou, Xingyu Ji, Bo Virginia Tech 2202 Kraft Dr Blacksburg VA 24060 USA Wayne State Univ Detroit MI USA

In this paper, we study kernelized bandits with distributed biased feedback. This problem is motivated by several real-world applications (such as dynamic pricing, cellular network configuration, and policy making), where users from a large population contribute to the reward of the action chosen by a central entity, but it is difficult to collect feedback from all users. Instead, only biased feedback (due to user heterogeneity) from a subset of users may be available. In addition to such partial biased feedback, we are also faced with two practical challenges due to communication cost and computation complexity. To tackle these challenges, we carefully design a new distributed phase-then-batch-based elimination ( DPBE) algorithm, which samples users in phases for collecting feedback to reduce the bias and employs maximum variance reduction to select actions in batches within each phase. By properly choosing the phase length, the batch size, and the confidence width used for eliminating suboptimal actions, we show that DPBE achieves a sublinear regret of (O) over tilde(Tau(1-alpha/2) + root(sic)Tau(Tau)), where alpha is an element of (0, 1) is the user-sampling parameter one can tune. Moreover, DPBE can significantly reduce both communication cost and computation complexity in distributed kernelized bandits, compared to some variants of the state-of-the-art algorithms (originally developed for standard kernelized bandits). Furthermore, by incorporating various differential privacy models (including the central, local, and shuffle models), we generalize DPBE to provide privacy guarantees for users participating in the distributed learning process. Finally, we conduct extensive simulations to validate our theoretical results and evaluate the empirical performance.

关键词： kernelized bandits distributed feedback bias regret communication cost computation complexity privacy

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Modeling and Features Extraction of Blood Vessels based on Soft Regional Segmentation

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IFAC-PapersOnLine 2018年第6期51卷 366-371页

作者： Kubicek, Jan Cerny, Martin Penhaker, Marek Augustynek, Martin Molnarova, Kristyna Kosturikova, Jana Baleja, Ladislav Oczka, David Timkovic, Juraj VSB-Technical University of Ostrava FEECS K450 17. listopadu 15 Ostrava-Poruba708 33 Czech Republic Clinic of Ophthalmology University Hospital Ostrava Czech Republic

Analysis and visualization of the blood vessels has a crucial impact for the clinical practice. One of the most important aspects of such analysis is the blood vessels features extraction characterizing their state and manifestation. Such procedure may be done by using the mathematical modeling of the blood vessels which is not conventionally possible from the native records. We have proposed a mathematical segmentation model for extraction and modeling of the blood vessels structure from the CT angiography native records with a target of differentiation of the physiological blood vessels from calcification spots indicating areas where the blood vessel is damaged. Such model consequently allows for objective quantification of the calcification amount, as an important clinical parameter of the damage level of the blood vessel. The method is based on the histogram partitioning, and consequent classification via predefined number of the fuzzy triangular classes representing individual parts of the blood vessels. Consequent part of the segmentation model takes into account spatial relations inside of each region to make a model accurate, and robust against the noise and artefacts. As a part of our analysis we have tested the computation complexity of the proposed segmentation model. © 2018

关键词： Blood vessels Angiography Biomineralization Bone Computerized tomography Extraction Fuzzy inference Image segmentation Physiological models Soft computing Clinical parameters Clinical practices computation complexity CT angiography Features extraction Regional segmentation Segmentation models Spatial relations

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A Novel Data Privacy-Preserving Protocol for Multi-data Users by using genetic algorithm

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SOFT COMPUTING 2019年第18期23卷 8539-8553页

作者： Pandiaraja, P. Deepa, N. MKumarasamy Coll Engn Dept Comp Sci & Engn Karur 639113 Tamil Nadu India

In this research paper, the proposed work is to put forward a Novel Data Privacy-Preserving Protocol (NDPPP) for Multi-data Users by using genetic algorithm. The data owner outsources the files in the encrypted format to the cloud. The data users can efficiently download the encrypted files from the cloud service provider without any loss of data. To provide this facility, there are certain existing mechanisms in the literature. But the existing mechanisms will result high computation complexity. By means of minimizing the computation complexity, a NDPPP for multi-data users is proposed using genetic algorithm in this research work. Genetic algorithms are usually used to produce high-quality resolutions for optimization. A new trapdoor function is proposed to preserve the data privacy by using our Data Privacy-Preserving Protocol. With the aim of avoiding numerous attacks, a secure authentication protocol is moreover developed between the trusted third party and data user. Additionally, the security is improved. Provided the leakage of data, loss of data as well as the data modification can also be avoided. The proposed work is implemented, and the implementation results of NDPPP illustrate that our protocol is efficient through computation and communication complexity. Moreover, the proposed work NDPPP is secure against various attacks like impersonation attack, eavesdropping, man-in-the-middle attack as well as replay attack.

关键词： Privacy Communication complexity computation complexity Trapdoor function Authentication Attacks

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Extended to multi-tilde-bar regular expressions and efficient finite automata constructions

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JOURNAL OF DISCRETE ALGORITHMS 2015年 33卷 58-70页

作者： Ouardi, Faissal Champarnaud, Jean-Marc Ziadi, Djelloul Mohammed V Univ LRI Dept Comp Sci Fac Sci Rabat Morocco Univ Rouen LITIS F-76821 St Etienne France

Several algorithms have been designed to convert a regular expression into an equivalent finite automaton. One of the most popular constructions, due to Glushkov and to McNaughton and Yamada, is based on the computation of the Null, First, Last and Follow sets (called Glushkov functions) associated with a linearized version of the expression. Recently Mignot considered a family of extended expressions called Extended to multitilde-bar Regular Expressions (EmtbREs) and he showed that, under some restrictions, Glushkov functions can be defined for an EmtbRE. In this paper we present an algorithm which efficiently computes the Glushkov functions of an unrestricted EmtbRE. Our approach is based on a recursive definition of the language associated with an EmtbRE which enlightens the fact that the worst case time complexity of the conversion of an EmtbRE into an automaton is related to the worst case time complexity of the computation of the Null function. Finally we show how to extend the ZPC-structure to EmtbREs, which allows us to apply to this family of extended expressions the efficient constructions based on this structure (in particular the construction of the c-continuation automaton, the position automaton, the follow automaton and the equation automaton). (C) 2015 Elsevier B.V. All rights reserved.

关键词： Regular expressions and languages Finite automata computation complexity

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Hybrid uplink multi-carrier CDMA interference-cancellation receiver

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IEE PROCEEDINGS-COMMUNICATIONS 2001年第2期148卷 119-124页

作者： McCormick, AC Grant, PM Thompson, JS Univ Edinburgh Dept Elect & Elect Engn Signals & Syst Grp Edinburgh EH9 3JL Midlothian Scotland

A novel interference cancellation detector, which combines an initial phase of cancelling one or more users per iteration depending on the tentative decision metrics, followed by maximum likelihood detection for the last few users, is proposed for multi-carrier CDMA uplink communication. Simulation results compare the system with a number of other multi-user detection receivers for an uplink multipath multi-user problem. The number of iterations and computation complexity are compared with a successive interference cancellation approach. The influence of the near-far effect and of poor channel estimation is also investigated.

关键词： Signal detection uplink multipath multi-user problem computational complexity Multiple access communication multi-user detection receivers computation complexity poor channel estimation Mobile radio systems successive interference cancellation Electromagnetic compatibility and interference interference cancellation receiver radio receivers hybrid receiver iterations Rayleigh channels multi-carrier CDMA uplink communication code division multiple access iterative methods multiuser channels mobile radio maximum likelihood detection simulation results multipath channels interference suppression tentative decision metrics near-far effect

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NOVEL SUBSPACE DISTORTION MEASUREMENT FOR EFFICIENT IMPLEMENTATION OF IMAGE VECTOR QUANTIZER

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ELECTRONICS LETTERS 1990年第7期26卷 480-482页

作者： PO, LM CHAN, CK Dept. of Electron. Eng. City Polytech. of Hong Kong Kowloon Tong Hong Kong

An efficient distortion measure based on a novel subspace is proposed for 4*4 image mean residual vector quantisers (MRVQ). The dimensionality of the coder distortion measure is reduced from 16 to 4, maintaining the v... 详细信息

关键词： coder distortion measure computation complexity computational complexity dimensionality reduction encoding image vector quantiser mean residual vector quantisers memory requirements picture processing subspace distortion measurement

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