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    Synthesis and microstructural properties of a geopolymer cement with high silica materials

    , Article Journal of Ceramic Processing Research ; Volume 13, Issue 4 , 2012 , Pages 425-428 ; 12299162 (ISSN) Asadi, M ; Naghizadeh, R ; Nemati, A ; Arzani, K ; Nassiri, R ; Sharif University of Technology
    JCPR  2012
    Abstract
    Activities conducted in this study can be divided into two general sections: synthesis and analysis and identifies the properties. A geopolymeric cement production process includes two steps of thermal activation and alkaline activation. Geopolymers are cementitious materials synthesized by a polycondensation reaction between an aluminate and silicate. The geopolymeric structures of the products were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). XRD results showed that there are no significant differences between the XRD patterns of geopolymers and metakaolin. The structure of the geopolymer is typically... 

    A novel forensic image analysis tool for discovering double JPEG compression clues

    , Article Multimedia Tools and Applications ; Volume 76, Issue 6 , 2017 , Pages 7749-7783 ; 13807501 (ISSN) Taimori, A ; Razzazi, F ; Behrad, A ; Ahmadi, A ; Babaie Zadeh, M ; Sharif University of Technology
    Springer New York LLC  2017
    Abstract
    This paper presents a novel technique to discover double JPEG compression traces. Existing detectors only operate in a scenario that the image under investigation is explicitly available in JPEG format. Consequently, if quantization information of JPEG files is unknown, their performance dramatically degrades. Our method addresses both forensic scenarios which results in a fresh perceptual detection pipeline. We suggest a dimensionality reduction algorithm to visualize behaviors of a big database including various single and double compressed images. Based on intuitions of visualization, three bottom-up, top-down and combined top-down/bottom-up learning strategies are proposed. Our tool... 

    A novel forensic image analysis tool for discovering double JPEG compression clues

    , Article Multimedia Tools and Applications ; Volume 76, Issue 6 , 2017 , Pages 7749-7783 ; 13807501 (ISSN) Taimori, A ; Razzazi, F ; Behrad, A ; Ahmadi, A ; Babaie Zadeh, M ; Sharif University of Technology
    Abstract
    This paper presents a novel technique to discover double JPEG compression traces. Existing detectors only operate in a scenario that the image under investigation is explicitly available in JPEG format. Consequently, if quantization information of JPEG files is unknown, their performance dramatically degrades. Our method addresses both forensic scenarios which results in a fresh perceptual detection pipeline. We suggest a dimensionality reduction algorithm to visualize behaviors of a big database including various single and double compressed images. Based on intuitions of visualization, three bottom-up, top-down and combined top-down/bottom-up learning strategies are proposed. Our tool... 

    Microstructure and compressibility of SiC nanoparticles reinforced Cu nanocomposite powders processed by high energy mechanical milling [electronic resource]

    , Article Ceramics International ; Volume 40, Issue 1, Part A, January 2014, Pages 951–960 Akbarpour, M.R. (Mohammad Reza) ; Salahi, E ; Alikhani Hesari, F ; Simchi, A ; Kim, H. S ; Sharif University of Technology
    Abstract
    Cu/SiC nanocomposite powders with homogeneously distributed nanosize SiC particles were produced by high energy mechanical milling (MM). Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and micro-hardness and density measurements were performed to understand the effects of microstructure and hardness on compaction behavior during MM. The effects of SiC nanoparticle content and mechanical milling time on apparent density (AD) and tap density (TD) of the nanocomposite powders were systematically investigated. The Hausner ratio (HR), defined as TD to AD, were estimated to evaluate friction between the particles. Increasing MM duration and SiC content resulted... 

    Cold compaction behavior and pressureless sinterability of ball milled WC and WC/Cu powders

    , Article Science of Sintering ; Volume 48, Issue 1 , 2016 , Pages 71-79 ; 0350820X (ISSN) Hashemi, S. R ; Ardestani, M ; Nemati, A ; Sharif University of Technology
    International Institute for the Science of Sintering (IISS)  2016
    Abstract
    In this research, cold compaction behavior and pressureless sinterability of WC, WC-10%wtCu and WC-30%wtCu powders were investigated. WC and WC/Cu powders were milled in a planetary ball mill for 20h. The milled powders were cold compacted at 100, 200, 300 and 400 MPa pressures. The compressibility behavior of the powders was evaluated using the Heckel, Panelli-Ambrosio and Ge models. The results showed that the PanelliAmbrosio was the preferred equation for description the cold compaction behavior of the milled WC and WC-30%wtCu powders. Also, the most accurate model for describing the compressibility of WC-10%wtCu powders was the Heckel equation. The cold compacts were sintered at 1400oC.... 

    Effects of drying temperature and aggregate shape on the concrete compressive strength: Experiments and data mining techniques

    , Article International Journal of Engineering Transactions C: Aspects ; Volume 33, Issue 9 , 2020 , Pages 1780-1791 Reza Kashyzadeh, K ; Ghorbani, S ; Forouzanmehr, M ; Sharif University of Technology
    Materials and Energy Research Center  2020
    Abstract
    The main purpose of this paper is to assess the impact of the geometry and size of the aggregate, as well as the drying temperature on the compressive strength of the ordinary concrete. To this end, two aggregates with sharp and round corners were prepared in three different aggregate sizes. After preparing concrete samples, the drying operations were carried out in the vicinity of room temperature, cold wind, and hot wind. Next, the linear relationship between the concrete strength and the studied parameters was estimated using Multiple Linear Regression (MLR) method. Finally, the Taguchi Sensitivity Analysis (TSA) and Decision Tree Analysis (DTA) were applied in order to determine the... 

    Ground-state energy and compressibility of a disordered two-dimensional electron gas

    , Article International Journal of Modern Physics B ; Volume 21, Issue 13-14 , 2007 , Pages 2134-2144 ; 02179792 (ISSN) Tanatar, B ; Subaşi, A. L ; Esfarjani, K ; Fazeli, S. M ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2007
    Abstract
    Two-dimensional (2D) electron systems in the presence of disorder are of interest in connection with the observed metal-insulator transition in such systems. We use density functional theory in its local-spin density approximation (LSDA) to calculate the ground-state energy of a 2D electron system in the presence of remote charged impurities which up on averaging provides disorder. The inverse compressibility calculated from the ground-state energy exhibits a minimum at a critical density controlled by the disorder strength. Our findings are in agreement with experimental results. © World Scientific Publishing Company  

    Effects of liquid second viscosity in high-amplitude sonoluminescence

    , Article Chinese Physics Letters ; Volume 21, Issue 2 , 2004 , Pages 356-359 ; 0256307X (ISSN) Moshaii, A ; Sadighi Bonabi, R ; Taeibi Rahni, M ; Daemi, M ; Sharif University of Technology
    Allerton Press Inc  2004
    Abstract
    The well-known Rayleigh-Plesset (RP) equation is the base of nearly all hydrodynamical descriptions of the sonoluminescence phenomenon. A major deficiency of this equation is that it accounts for viscosity of an incompressible liquid and compressibility, separately. By removing this approximation, we have modified the RP equation, considering effects of liquid second viscosity. This modification exhibits its importance at the end of an intense collapse, so that the new model predicts the appearance of a new picosecond bouncing during high-amplitude sonoluminescence radiation. This new bouncing produces very sharp (sub-picosecond) peaks on the top of the sonoluminescence pulse. These new... 

    The effect of carbon on the restoration phenomena during hot deformation of carbon steels

    , Article Zeitschrift fuer Metallkunde/Materials Research and Advanced Techniques ; Volume 94, Issue 8 , 2003 , Pages 916-921 ; 00443093 (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Zebarjad, S. M ; Sharif University of Technology
    Carl Hanser Verlag  2003
    Abstract
    A study has been made to determine the influence of the carbon content on the kinetics of dynamic and static recrystallization during and after hot deformation of carbon steels. For this purpose, single- and double-hit hot compression experiments at various strain rates and temperatures together with the Avrami-type kinetics equation and Bergstrom approach have been utilized to investigate recrystallization behavior. The results show that the apparent activation energy of hot deformation decreases with increasing carbon content and this phenomenon results in a faster dynamic recrystallization at high temperatures and/or low strain rates. Also, increasing carbon content leads to a higher rate... 

    An investigation of the silicon role on austenite recrystallization

    , Article Materials Letters ; Volume 56, Issue 6 , 2002 , Pages 984-989 ; 0167577X (ISSN) Serajzadeh, S ; Karimi Taheri, A ; Sharif University of Technology
    2002
    Abstract
    The role of silicon on austenite recrystallization was investigated using hot compression experiments on a low carbon and a high silicon steel samples. The models were proposed to describe the hot deformation behavior of metals regarding dynamic recovery. The rate of static recrystallization was found lower in the silicon steel in comparison with low carbon steel. Silicon was found to produce a lower rate of dynamic recovery due to its effect on the austenite staking fault energy  

    On a new approach for finding the kern of a beam section

    , Article Engineering Structures ; Volume 23, Issue 9 , 2001 , Pages 1080-1084 ; 01410296 (ISSN) Mofid, M ; Shadnam, M. R ; McCabe, S. L ; Sharif University of Technology
    2001
    Abstract
    A new approach is presented that can be used to determine the kern of a general arbitrary section with any shape and conditions. The method is simple, practical and powerful, and is based on elementary calculus. Geometries containing curved boundaries and arbitrary shapes can be handled easily with the analytical equations presented, while the numerically specified shape of any other cross-section can also be analyzed by using a numerical form of the exact governing equations developed. The correctness of the results has been ascertained by comparison with analytical solutions, as well as with examples presented in the literature, and very good agreement has been achieved. © 2001 Elsevier... 

    Simple lossless and near-lossless medical image compression based on enhanced DPCM transformation

    , Article IEEE Pacific RIM Conference on Communications, Computers, and Signal Processing - Proceedings ; 2011 , Pages 66-72 ; 9781457702518 (ISBN) Sepehrband, F ; Mortazavi, M ; Ghorshi, S ; Choupan, J ; Sharif University of Technology
    2011
    Abstract
    Medical images include information about human body which are used for different purposes such as surgical and diagnostic plans. Compression of medical images is used in some applications such as profiling patient's data and transmission systems. Regard to importance of medical images information, lossless or near-lossless compression is preferred. Lossless JPEG, JPEG-LS and lossless version of JPEG2000 are few well-known methods for lossless compression. JPEG2000 is one of the latest and provides good compression ratio, however, it is complex [1]. In real time application which needs hardware implementation, low complex algorithm accelerates compression process. In this paper, a lossless... 

    Generalised secure distributed source coding with side information

    , Article IET Communications ; Volume 4, Issue 18 , 2010 , Pages 2262-2272 ; 17518628 (ISSN) Salimi, S ; Salmasizadeh, M ; Aref, M. R ; Sharif University of Technology
    2010
    Abstract
    New inner and outer bounds on the achievable compression-equivocation rate region for generalised secure data compression with side information are given that do not match in general. In this setup, two senders, Alice and Charlie intend to transmit information to Bob via channels with limited capacity so that he can reliably reconstruct their observations. The eavesdropper, Eve, has access to one of the channels at each instant and is interested in the source of the same channel at the time. Bob and Eve also have their own observations, which are correlated with Alice's and Charlie's observations. In this model, two equivocation and compression rates are defined with respect to the sources... 

    Monte Carlo simulation of recrystallization with hardness input of cold worked metal

    , Article Materials Science and Engineering A ; Volume 496, Issue 1-2 , 2008 , Pages 389-392 ; 09215093 (ISSN) Kazeminezhad, M ; Sharif University of Technology
    2008
    Abstract
    A Monte Carlo model on the basis of hardness input is developed to predict the annealing microstructure of deformed specimens in tensile, compression, and tensile + compression tests. From experimental value of hardness, the stored energy of the deformed specimens is calculated and entered into the Monte Carlo model. The consistency between the simulation results and experimental data shows that the developed model based on hardness input can be more practical since the effect of different deformation states is considered for estimating of stored energy. © 2008 Elsevier B.V. All rights reserved  

    Efficient Compression of ECG Signals based on two dimensional wavelet transform and DCT decimation

    , Article IWSSIP 2005 - 12th International Workshop on Systems, Signals and Image Processing(SSIP-SPI, 2005), Chalkida, 22 September 2005 through 24 September 2005 ; 2005 , Pages 317-322 ; 0907776205 (ISBN); 9780907776208 (ISBN) Moazanii Goudarzi, M ; Rabiee, H. R ; Ghanbari, M ; Sharif University of Technology
    2005
    Abstract
    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 constructed from the one dimensional ECG signal using decimation and interpolation in the discrete cosine transform (DCT) domain. Since reasonable results in image compression have been achieved by means of set partitioning in hierarchical trees (SPIHT) algorithm, we use SPIHT algorithm to code the 2-D wavelet transform of the ECG signals. Experimental results on selected records of ECG from... 

    Data compression technique for high resolution wireless photoplethysmograph recording system

    , Article International Conference on Space Science and Communication, IconSpace ; 2013 , Pages 345-349 ; 21654301 (ISSN) ; 9781467352314 (ISBN) Chong, K. S ; Zahedi, E ; Gan, K. B ; Mohd. Ali, M. A ; Sharif University of Technology
    2013
    Abstract
    Multi-site photoplethysmography is an optoelectronic technique that measures changes in blood volume associated with cardiac contraction. Photoplethysmogram (PPG) recording enables researchers to study the vascular and hemodynamic properties of human subjects. Currently, there is no commercial system available in the market to perform multi-channel PPG recording. The measurements can be obtained from fingertips, ear lobes and toes due to their low absorption and high degree of vasculature. The main objective of this project is to develop a suitable data compression algorithm for two-channel simultaneous high resolution wireless PPG recording system. MATLAB software was used during the... 

    New rectangular partitioning methods for lossless binary image compression

    , Article International Conference on Signal Processing Proceedings, ICSP, 24 October 2010 through 28 October 2010 ; 2010 , Pages 694-697 ; 9781424458981 (ISBN) Kafashan, M ; Hosseini, H ; Beygiharchegani, S ; Pad, P ; Marvasti, F ; Sharif University of Technology
    Abstract
    In this paper, we propose two lossless compression techniques that represent a two dimensional Run-length Coding which can achieve high compression ratio. This method works by partitioning the block regions of the input image into rectangles instead of working by runs of adjacent pixels, so it is found to be more efficient than 1D RLE Run-length Coding for transmitting texts and image. In the first method, length and width of consecutive black and white rectangles are transmitted. The idea of this method is new and it can be very effective for some images which have large blocks of black or white pixels. But in the second method only black rectangles are considered in order to transmit and... 

    Multi-period lot sizing and job shop scheduling with compressible process times for multilevel product structures

    , Article International Journal of Production Research ; Volume 51, Issue 20 , 2013 , Pages 6229-6246 ; 00207543 (ISSN) Karimi Nasab, M ; Seyedhoseini, S. M ; Modarres, M ; Heidari, M ; Sharif University of Technology
    2013
    Abstract
    This paper presents mathematical modelling of joint lot sizing and scheduling problem in job shop environment under a set of working conditions. The main feature of the problem is to deal with flexible machines able to change their working speeds, known as process compressibility. Furthermore, produced items should be assembled together to make final products. In other words, the products have a multilevel structure, shown with bill of materials. As the problem is proved to be strongly NP-hard, it is solved by a memetic algorithm here. Computational experiences on the data of Mega Motor company are reported. Also, further experiences on random test data confirm the performance of the... 

    Compressed sensing and multiple image fusion: An information theoretic approach

    , Article Iranian Conference on Machine Vision and Image Processing, MVIP ; 2013 , Pages 339-342 ; 21666776 (ISSN) ; 9781467361842 (ISBN) Keykhosravi, K ; Mashhadi, S ; Engineers (IEEE) Antennas and Propagation Society; The Institute of Electrical and Electronics ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    In this paper, we propose an information theoretic approach to fuse images compressed by compressed sensing (CS) techniques. The goal is to fuse multiple compressed images directly using measurements and reconstruct the final image only once. Since the reconstruction is the most expensive step, it would be a more economic method than separate reconstruction of each image. The proposed scheme is based on calculating the result using weighted average on the measurements of the inputs, where weights are calculated by information theoretic functions. The simulation results show that the final images produced by our method have higher quality than those produced by traditional methods, especially... 

    Successive concave sparsity approximation for compressed sensing

    , Article IEEE Transactions on Signal Processing ; Volume 64, Issue 21 , 2016 , Pages 5657-5671 ; 1053587X (ISSN) Malek Mohammadi, M ; Koochakzadeh, A ; Babaie Zadeh, M ; Jansson, M ; Rojas, C. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    In this paper, based on a successively accuracy-increasing approximation of the ℓ0 norm, we propose a new algorithm for recovery of sparse vectors from underdetermined measurements. The approximations are realized with a certain class of concave functions that aggressively induce sparsity and their closeness to the ℓ0 norm can be controlled. We prove that the series of the approximations asymptotically coincides with the ℓ1 and ℓ0 norms when the approximation accuracy changes from the worst fitting to the best fitting. When measurements are noise-free, an optimization scheme is proposed that leads to a number of weighted ℓ1 minimization programs, whereas, in the presence of noise, we propose...