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compressibility
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General pressure-correction strategy to include density variation in incompressible algorithms
, Article Journal of Thermophysics and Heat Transfer ; Volume 17, Issue 3 , 2003 , Pages 372-380 ; 08878722 (ISSN) ; Hosseinizadeh, S. F ; Sharif University of Technology
American Inst. Aeronautics and Astronautics Inc
2003
Abstract
This work deals with the popular topic of extending incompressible numerical formulations to the compressible or variable density regime. Based on an analogy between the incompressible and compressible governing equations, a general strategy is suitably developed to facilitate the compressible flow solution through using incompressible algorithms. It is shown that the implementation of the extended strategy to an arbitrarily incompressible algorithm requires two minor modifications in the original algorithm. In fact, two on/off switches suffice to implement the two required modifications. Switch one includes the compressible source terms to the momentum governing equations. Switch two...
Distributed Compressed Sensing (DCS) and its Application in Wireless Sensor Network (WSN)
, M.Sc. Thesis Sharif University of Technology ; Babaei Zadeh, Masoud (Supervisor)
Abstract
Recent advances in Micro-Electro-Mechanical Systems (MEMS) technology, wireless communications,and digital electronics have enabled the development of low-cost, low-power,multifunctional sensor nodes that are small in size and communicate untethered in short distances.Wireless Sensor Network (WSN) including these sensors has been utilized in many applications, namely military and environmental applications. Due to unchangeable battery in most WSNs, Power consumption is an important challenge in such systems. A sensor node expends maximum energy in data communication. Control environmental parameter is among the most important applications of WSN. The actual physical environmental information...
Comments on “Hydroelastic impact of a horizontal floating plate with forward speed” [J. Fluids Struct. 60 (2016) 97–113]
, Article Journal of Fluids and Structures ; Volume 81 , 2018 , Pages 378-382 ; 08899746 (ISSN) ; Rahbar Ranji, A ; Haddadpour, H ; Sharif University of Technology
Academic Press
2018
Abstract
This comment concerns the mathematical errors in the recent work of Wang et al. (2016). The corrected equations are presented. Deflections and critical values of compressive force and forward speed are modified. © 2018 Elsevier Ltd
Numerical study of natural convection in vertical enclosures using a novel non-Boussinesq algorithm
, Article Numerical Heat Transfer; Part A: Applications ; Volume 52, Issue 9 , 2007 , Pages 849-873 ; 10407782 (ISSN) ; Hosseinizadeh, S. F ; Sharif University of Technology
2007
Abstract
This article applies a novel non-Boussinesq numerical algorithm to solve the free-convection problem in a wide range of thin to thick vertical cavities subject to different side-wall temperatures. In this regard, the compressible flow equations are solved using a primitive incompressible method. No Boussinesq approximation and low Mach number consideration are included in the formulation. To implement the compressibility effect, the density field is calculated via the equation of state for gas. The temperature gradient is suitably varied to generate different low to high thermobuoyant fields, where the Boussinesq approximation may or may not be valid. Contrary to published works on the thin...
CodedSketch: A coding scheme for distributed computation of approximated matrix multiplication
, Article IEEE Transactions on Information Theory ; Volume 67, Issue 6 , 2021 , Pages 4185-4196 ; 00189448 (ISSN) ; Maddah Ali, M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, we propose CodedSketch, as a distributed straggler-resistant scheme to compute an approximation of the multiplication of two massive matrices. The objective is to reduce the recovery threshold, defined as the total number of worker nodes that the master node needs to wait for to be able to recover the final result. To exploit the fact that only an approximated result is required, in reducing the recovery threshold, some sorts of pre-compression are required. However, compression inherently involves some randomness that would lose the structure of the matrices. On the other hand, considering the structure of the matrices is crucial to reduce the recovery threshold. In...
Multihypothesis compressed video sensing technique
, Article IEEE Transactions on Circuits and Systems for Video Technology ; Volume 26, Issue 4 , 2016 , Pages 627-635 ; 10518215 (ISSN) ; Karimi, M ; Marvasti, F ; Sharif University of Technology
Abstract
In this paper, we present a compressive sampling and multihypothesis (MH) reconstruction strategy for video sequences that has a rather simple encoder, while the decoding system is not that complex. We introduce a convex cost function that incorporates the MH technique with the sparsity constraint and the Tikhonov regularization. Consequently, we derive a new iterative algorithm based on these criteria. This algorithm surpasses its counterparts (Elasticnet and Tikhonov) in recovery performance. Besides, it is computationally much faster than Elasticnet and comparable with Tikhonov. Our extensive simulation results confirm these claims
A truly incompressible smoothed particle hydrodynamics based on artificial compressibility method
, Article Computer Physics Communications ; Volume 210s , 2017 , Pages 10-28 ; 00104655 (ISSN) ; Hejranfar, K ; Sharif University of Technology
Abstract
In the present study, a truly incompressible smoothed particle hydrodynamics based on the artificial compressibility method for simulating steady and unsteady incompressible flows is proposed and assessed. The incompressible Navier–Stokes equations in the primitive variables formulation using the artificial compressibility method proposed by Chorin in the Eulerian reference frame are written in a Lagrangian reference frame to provide an appropriate incompressible SPH algorithm. The proposed SPH formulation implemented here is based on an implicit dual-time stepping scheme to be capable of time-accurate analysis of unsteady flows. The advantage of the Artificial Compressibility-based...
An efficient lossless medical image transformation method by improving prediction model
, Article International Conference on Signal Processing Proceedings, ICSP, 24 October 2010 through 28 October 2010 ; 2010 , Pages 728-731 ; 9781424458981 (ISBN) ; Mortazavi, M ; Ghorshi, S ; IEEE Beijing Section; The Chinese Institute of Electronics (CIE); The Institution of Engineering and Technology (IET); Union Radio Scientifique Internationale (URSI); National Natural Science Foundation of China ; Sharif University of Technology
Abstract
Medical images include human body picture and it is used in diagnosis purpose [1]. Lossless compression of medical image is an application of medical imaging. During lossless compression task, transformation algorithm can be used to increase compression ratio. In Real time applications such as telemedicine and online diagnosis, hardware implementation accelerates the process. Hence, for such purposes medical compression is better to be simple. Lossless JPEG and JPEG2000 are some compression method. JPEG2000 gives better compression ratio. However, it is complex. In this paper an efficient method of lossless image transformation has been introduced by improving prediction model. Simulation...
Roi-based 3D human brain magnetic resonance images compression using adaptive mesh design and region-based discrete wavelet transform
, Article International Journal of Wavelets, Multiresolution and Information Processing ; Volume 8, Issue 3 , 2010 , Pages 407-430 ; 02196913 (ISSN) ; Shooshtari, P ; Sharif University of Technology
Abstract
Due to the large volume required for medical images for transmission and archiving purposes, the compression of medical images is known as one of the main concepts of medical image processing. Lossless compression methods have the drawback of a low compression ratio. In contrast, lossy methods have a higher compression ratio and suffer from lower quality of the reconstructed images in the receiver. Recently, some selective compression methods have been proposed in which the main image is divided into two separate regions: Region of Interest (ROI), which should be compressed in a lossless manner, and Region of Background (ROB), which is compressed in a lossy manner with a lower quality. In...
Effects of saturation degrees, freezing-thawing, and curing on geotechnical properties of lime and lime-cement concretes
, Article Cold Regions Science and Technology ; Volume 160 , 2019 , Pages 242-251 ; 0165232X (ISSN) ; Saberian, M ; Tao, Z ; Mojtahedi, S.F ; Li, J ; Ghasemi, M ; Rezvani, S. S ; Li, W ; Sharif University of Technology
Elsevier B.V
2019
Abstract
There are very limited researches carried out to investigate the influence of saturation degrees, freezing-thawing, and curing times on geotechnical properties of lime concrete (LC) and lime-cement concrete (LCC) due to the capillary action and changes in groundwater table. Subsequently, the primary goal of this research is to investigate the influence of these parameters on mechanical properties of LC and LCC using unconfined compression tests, namely uniaxial compressive strength (UCS), stress-strain behavior, deformability index (I D ), secant modulus (E S ), failure strain, bulk modulus (K), resilient modulus (M R ), brittleness index (I B ), and shear modulus (G). At first, the...
Wavelet-based 2-D ECG data compression method using SPIHT and VQ coding
, Article EUROCON 2007 - The International Conference on Computer as a Tool, Warsaw, 9 September 2007 through 12 September 2007 ; December , 2007 , Pages 133-137 ; 142440813X (ISBN); 9781424408139 (ISBN) ; Fatemizadeh, E ; Sharif University of Technology
2007
Abstract
An improved wavelet-based 2-D ECG data compression method is presented which employs a double stage compression. In the first stage the set partitioning in hierarchical trees (SPIHT) algorithm is used to compress the 2-D data array formed by cutting and beat-aligning the heartbeat data sequence. In the second stage vector quantization is applied to the residual image obtained from the previous stage. The 2-D approach utilizes both inter-beat and inter-sample redundancies in the ECG signal The proposed algorithm is applied to several records in the MIT-BIH arrhythmia database. Results show lower Percent Root mean square Difference (PRD) than 1-D methods and several 2-D methods for the same...
Efficient compression of ECG signals based on two dimensional wavelet transform and SPIHT coding algorithm
, Article 2005 International Conference on Mathematics and Engineering Techniques in Medicine and Biological Sciences, METMBS'05, Las Vegas, NV, 20 June 2005 through 23 June 2005 ; 2005 , Pages 82-86 ; 9781932415834 (ISBN) ; Rabiee, H. R ; Ghanbari, M ; Sharif University of Technology
2005
Abstract
Signal compression is an important element encountered in data storage applications. Over the years various techniques for data reductions have been proposed. In this paper we introduce an effective method for compressing semi-periodic signals. Although the approach is applicable to any semi-periodic signal, our attention is focused on the compression of electrocardiogram (ECG) signals. An ECG signal is composed of many similar beats which makes it to behave semi-periodic This paper deals with beat variation periods and exploits the correlation between cycles (inter-beat) and correlation within each cycle (intra-beat) for compression. For efficient compression a 2-dimensional array is...
Surface oxidization effect on the mechanical behavior of aluminum nanopowders under triaxial compression test
, Article Applied Surface Science ; Volume 606 , 2022 ; 01694332 (ISSN) ; Khajehpour, B ; Rezaei Sameti, A ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this paper, the impression of surface oxidization on the aluminum nanopowders is investigated using the reactive molecular dynamics (MD) method under the triaxial compression tests. Validation of the computational model is examined with the experimental results, which demonstrates an acceptable accuracy of the numerical simulations. The MD simulations are performed in three stages; relaxing the nanopowders at 300 K and 0.1 MPa, confining the nanopowders under hydrostatic pressure, and imposing the deviatoric stress through the triaxial compression. Evolutions of the relative density with pressure, stress with strain, and dislocation density with strain are derived together with the...
Analysis of Universal Coding Algorithms for Some Special Classes of Information Sources
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Behroozi, Hamid (Supervisor)
Abstract
The coding and compression of information sources with special probability distribution is the center of concentration of researchers in this field in the last decades. In this dissertation, after a concise introduction to source coding, we focus on the universal source coding and data compression from an algorithmic and information theoretic point of view. First we introduce the fundamental concepts of source coding and data compression. Then, we analysis some algorithms on integer coding and verify their universality and asymptotically optimality. Usually statistics of information sources is not available in communication systems and storage devices, so that applying universal source...
Persian Sentence Compression Using Constituency Analysis of Sentences
, M.Sc. Thesis Sharif University of Technology ; Izadi, Mohammad (Supervisor)
Abstract
The amount of ever-growing generated data increases the need for automatic methods in text processing. As a solution, sentence compression and text summarization are considered as methods of managing and dealing with this huge amount of data. Additionally, Sentence compression is also useful in different text processing systems such as text summarization, news condensation, information extraction and question-answering systems. A sentence compression system takes a long sentence as input and returns a shorter form of the sentence in a way that its important information and grammaticality is preserved. In this thesis, we devise a rule-based extractive sentence compression method. This...
Effect of thrust on the aeroelastic instability of a composite swept wing with two engines in subsonic compressible flow
, Article Journal of Fluids and Structures ; Volume 36 , 2013 , Pages 18-31 ; 08899746 (ISSN) ; Askarian, A. R ; Zarifian, P ; Sharif University of Technology
2013
Abstract
This paper aims to investigate aeroelastic stability boundary of subsonic wings under the effect of thrust of two engines. The wing structure is modeled as a tapered composite box-beam. Moreover, an indicial function based model is used to calculate the unsteady lift and moment distribution along the wing span in subsonic compressible flow. The two jet engines mounted on the wing are modeled as concentrated masses and the effect of thrust of each engine is applied as a follower force. Using Hamilton's principle along with Galerkin's method, the governing equations of motion are derived, then the obtained equations are solved in frequency domain using the K-method and the aeroelastic...
CS-ComDet: A compressive sensing approach for inter-community detection in social networks
, Article Proceedings of the 2015 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining, ASONAM 2015, 25 August 2015 through 28 August 2015 ; 2015 , Pages 89-96 ; 9781450338547 (ISBN) ; Rabiee, H. R ; Movaghar, A ; Ghalebi, E ; Nazemian, A ; Pei, J ; Tang, J ; Silvestri, F ; Sharif University of Technology
Association for Computing Machinery, Inc
2015
Abstract
One of the most relevant characteristics of social networks is community structure, in which network nodes are joined together in densely connected groups between which there are only sparser links. Uncovering these sparse links (i.e. intercommunity links) has a significant role in community detection problem which has been of great importance in sociology, biology, and computer science. In this paper, we propose a novel approach, called CS-ComDet, to efficiently detect the inter-community links based on a newly emerged paradigm in sparse signal recovery, called compressive sensing. We test our method on real-world networks of various kinds whose community structures are already known, and...
Deformation behavior of AA2017-SiCp in warm and hot deformation regions
, Article Materials and Design ; Volume 67 , February , 2015 , Pages 318-323 ; 02613069 (ISSN) ; Ranjbar Motlagh, S ; Mirbagheri, S. M. H ; Akhgar, J. M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In this work, the flow stress behavior of a metal matrix composite AA2017-10% SiCp was studied by means of the uni-axial compression test. The composite was first produced by stir casting technique and then, hot extrusion with the ratio of 18:1 was carried out to achieve a microstructure with a homogeneous distribution of SiC particles. In the next stage, the isothermal compression tests were conducted on the cylindrical specimens up to the true strain of 0.6. The experiments were performed at temperatures between room temperature to 400°C and strain rates of 0.003, 0.03 and 0.3s-1. Negative strain rate sensitivity was observed in the temperatures less than 250°C indicating the occurrence of...
Joint compressive single target detection and parameter estimation in radar without signal reconstruction
, Article IET Radar, Sonar and Navigation ; Volume 9, Issue 8 , September , 2015 , Pages 948-955 ; 17518784 (ISSN) ; Babaie Zadeh, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this study, a detector/estimator is proposed for compressed sensing radars, which does not need to reconstruct the radar signal, and which works directly from compressive measurements. More precisely, through direct processing of the measurements, and without the need for reconstructing the original radar signal, the system performs target detection, and then estimates range, Doppler frequency shift and radar cross section in the presence of a Gaussian clutter. It can be seen that for large compression ratios, the detection performance and estimation quality is comparable with a common radar system while having a much lower data rate and with less computational load
A gaussian process regression framework for spatial error concealment with adaptive kernels
, Article Proceedings - International Conference on Pattern Recognition, 23 August 2010 through 26 August 2010, Istanbul ; 2010 , Pages 4541-4544 ; 10514651 (ISSN) ; 9780769541099 (ISBN) ; Rabiee, H. R ; Pourdamghani, N ; Rohban, M. H ; Sharif University of Technology
2010
Abstract
We have developed a Gaussian Process Regression method with adaptive kernels for concealment of the missing macro-blocks of block-based video compression schemes in a packet video system. Despite promising results, the proposed algorithm introduces a solid framework for further improvements. In this paper, the problem of estimating lost macro-blocks will be solved by estimating the proper covariance function of the Gaussian process defined over a region around the missing macro-blocks (i.e. its kernel function). In order to preserve block edges, the kernel is constructed adaptively by using the local edge related information. Moreover, we can achieve more improvements by local estimation of...