Search for: chemical-activation
0.008 seconds
Total 54 records

    Methane Adsorption on Activated Carbon Prepared from Lignocellulosic Materials

    , M.Sc. Thesis Sharif University of Technology Zaroudi, Maryam (Author) ; Kazemeini, Mohammad (Supervisor) ; Bozorgzadeh, Hamid Reza (Supervisor)
    One of the methods for adsorption of natural gas that has economical, operational and environmental preferences as an alternative energy source is storage as an adsorbed phase in porous material. ANG is superior to CNG and LNG technologies in terms of economy and safety. Carbonaceous nanostructures with pore diameter of 0.8-1.4 nm can be proper adsorbents for methane adsorption. In this work, cellulose and lignin which form lignocellulosic material’s structure, has been used as precursor for producing activated carbon. The activated carbon prepared has been used as adsorbent for adsorption of methane. The use of hydrothermal pretreatment followed by carbonization and chemical activation is... 

    Modeling of platinum extraction from used reforming catalyst in iodine solutions

    , Article ECS Transactions ; Volume 41, Issue 17 , 2012 , Pages 45-51 ; 19385862 (ISSN) ; 9781607683070 (ISBN) Moghaddam, H. R ; Baghallha, M ; Sharif University of Technology
    Platinum extraction from spent reforming catalysts in iodine solutions under atmospheric pressure and at temperatures up to 95°C was previously investigated in our group. In this system, platinum is oxidized from the spent catalyst with tri-iodide. In some of the experiments, it was observed that platinum extraction peaked and then decreased. This indicates that a precipitation reaction slowly occurs that removes the dissolved Pt ions from the solution. Power-law rate equation for the Pt extraction to PtI6 2- and the precipitation of the dissolved platinum to PtI 4(s) was implemented to model the experimental Pt extraction data. The activation energies for the platinum dissolution reaction... 

    Low-Reynolds-number predator

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 6 , December , 2015 ; 15393755 (ISSN) Ebrahimian, M ; Yekehzare, M ; Ejtehadi, M. R ; Sharif University of Technology
    American Physical Society  2015
    To generalize simple bead-linker model of swimmers to higher dimensions and to demonstrate the chemotaxis ability of such swimmers, here we introduce a low-Reynolds predator, using a two-dimensional triangular bead-spring model. Two-state linkers as mechanochemical enzymes expand as a result of interaction with particular activator substances in the environment, causing the whole body to translate and rotate. The concentration of the chemical stimulator controls expansion versus the contraction rate of each arm and so affects the ability of the body for diffusive movements; also the variation of activator substance's concentration in the environment breaks the symmetry of linkers' preferred... 

    Cooperative abnormality detection in fluidic medium molecular communication

    , Article 2020 Iran Workshop on Communication and Information Theory, IWCIT 2020 ; 26-28 May , 2020 Khaloopour, L ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    In this paper, we study the problem of cooperative abnormality detection using mobile sensors in a fluidic medium, based on a molecular communication setup. The sensors are injected into the medium to search the environment for the abnormality. To reduce the effects of sensor imperfection, we propose a cooperative scheme where the sensors activate each other by releasing some molecules (i.e., markers), into the medium after they sense an abnormality. A number of fusion centers (FC) are placed at specific locations in the medium, which absorb all sensors arrived at their locations. By observing the states of the received sensors, each FC decides whether an abnormality exists in its... 

    Theoretical concept study of cooperative abnormality detection and localization in fluidic-medium molecular communication

    , Article IEEE Sensors Journal ; Volume 21, Issue 15 , 2021 , Pages 17118-17130 ; 1530437X (ISSN) Khaloopour, L ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    In this paper, we propose a theoretical framework for cooperative abnormality detection and localization systems by exploiting molecular communication setup. The system consists of mobile sensors in a fluidic medium, which are injected into the medium to search the environment for abnormality. Some fusion centers (FC) are placed at specific locations in the medium, which absorb all sensors arrived at their locations, and by observing its state, each FC decides on the abnormality existence and/or its location. To reduce the effects of sensor imperfection, we propose a scheme where the sensors release some molecules (i.e., markers) into the medium after they sense an abnormality. If the goal... 

    PF-DRAM: A precharge-free DRAM structure

    , Article 48th ACM/IEEE Annual International Symposium on Computer Architecture, ISCA 2021, 14 June 2021 through 19 June 2021 ; Volume 2021-June , 2021 , Pages 126-138 ; 10636897 (ISSN); 9781665433334 (ISBN) Rohbani, N ; Darabi, S ; Sarbazi Azad, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Although DRAM capacity and bandwidth have increased sharply by the advances in technology and standards, its latency and energy per access have remained almost constant in recent generations. The main portion of DRAM power/energy is dissipated by Read, Write, and Refresh operations, all initiated by a Precharge phase. Precharge phase not only imposes a large amount of energy consumption, but also increases the delay of closing a row in a memory block to open another one. By reduction of row-hit rate in recent workloads, especially in multi-core systems, precharge rate increases which exacerbates DRAM power dissipation and access latency. This work proposes a novel DRAM structure, called... 

    Preparation of Nano Adsorbent from Cellulose-based Material for Gas Storage

    , M.Sc. Thesis Sharif University of Technology Heidari, Sara (Author) ; Kazemeini, Mohammad (Supervisor) ; Rashidi, Alimorad (Co-Advisor)
    Natural gas (NG) has emerged as an alternative energy source in transportation sector as it provides clean combustion and hence lowers exhaust pollution. NG can be stored as an adsorbed phase in porous materials and is referred to ANG. The use of adsorbent materials for storing NG, at relatively low pressure (3.5–4 MPa), is a possibility for making ANG technology competitive with CNG. Among all adsorbents, carbon nanostructures with pore diameter (0.8-1.4 nm) has shown the highest adsorption capacity of natural gas. In the present study, cellulose has been used as the carbonaceous precursor and Activated Carbon (AC) has been prepared using hydrothermal carbonization of cellulose followed by... 

    Preparation of Herbal Biomass as Extractive Phases for Trace Determination of Pesticides

    , Ph.D. Dissertation Sharif University of Technology Keikavousi Behbahan, Arnavaz (Author) ; Bagheri, Habib (Supervisor) ; Mahdavi, Vahideh (Supervisor)
    The main approach of this thesis is to study the performance and efficiency of agricultural biomass derived extractive phases in sample preparation methods. In this regard, different types of agricultural biomasses and various important factors in the production of biochar from biomass were studied by two physical and chemical methods. Accordingly, different types of biochars have been made and applied in different extraction setups along with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and gas chromatography-electron capture (GC-ECD) to detect agricultural pesticides. Also, validated developed methods were used to investigate the safety of some highly... 

    Effects of cold severe plastic deformation and heating on dendritic and non-dendritic structures: A356 alloy

    , Article International Journal of Cast Metals Research ; Volume 27, Issue 5 , 1 October , 2014 , Pages 312-320 ; ISSN: 13640461 Dodangeh, A ; Kazeminezhad, M ; Aashuri, H ; Sharif University of Technology
    In this research the effects of cold deformation and heating to the semi-solid temperature on microstructure and mechanical properties of cast dendritic and non-dendritic structures of A356 alloy were investigated. To produce the non-dendritic samples, the semi-solid slurry was obtained by electromagnetic stirring and rheoforged and then the samples were heated to semi-solid temperature. In order to impose the deformation to the dendritic and non-dendritic samples, multidirectional forging process was used. Non-dendritic samples were deformed with applying one to three passes of the multidirectional forging and then were kept at the semi-solid range of temperature again. Microstructural and... 

    Variations in trunk muscle activities and spinal loads following posterior lumbar surgery: A combined in vivo and modeling investigation

    , Article Clinical Biomechanics ; Volume 30, Issue 10 , 2015 , Pages 1036-1042 ; 02680033 (ISSN) Jamshidnejad, S ; Arjmand, N ; Sharif University of Technology
    Background Iatrogenic injuries to paraspinal muscles during posterior lumbar surgery cause a reduction in their contractile cross-sectional area and thus presumably their postoperative activation. This study investigates the effect of such intraoperative injuries on postoperative patterns of muscle activations and spinal loads during various activities using a combined modeling and in vivo MR imaging approach. Methods A three-dimensional, multi-joint, musculoskeletal model was used to estimate pre- and postoperative muscle forces and spinal loads under various activities in upright and flexed postures. According to our in vivo pre- and postoperative (∼ 6 months) measurements in six patients... 

    Dependency modeling of steady state grain size on the stacking fault energy through severe plastic deformation

    , Article Materials Letters ; Volume 159 , November , 2015 , Pages 410-412 ; 0167577X (ISSN) Parvin, H ; Kazeminezhad, M ; Sharif University of Technology
    Elsevier  2015
    Recent investigations have shown that the steady state grain size of severely deformed materials is dependent on the stacking fault energy. In this paper, a model is presented to investigate such a dependency which uses thermodynamics based calculations. The present model shows that the relationship between the steady state grain size and the stacking fault energy of material is in power law form, directly. Furthermore, the model shows that the steady state grain size has an exponential relationship with the self-diffusion activation energy and a decrease in the self-diffusion activation energy increases the steady state grain size. The model predictions are in good agreement with the... 

    Two multimodal approaches for single microphone source separation

    , Article European Signal Processing Conference, 28 August 2016 through 2 September 2016 ; Volume 2016-November , 2016 , Pages 110-114 ; 22195491 (ISSN ; 9780992862657 (ISBN) Sedighin, F ; Babaie Zadeh, M ; Rivet, B ; Jutten, C ; Sharif University of Technology
    European Signal Processing Conference, EUSIPCO  2016
    In this paper, the problem of single microphone source separation via Nonnegative Matrix Factorization (NMF) by exploiting video information is addressed. Respective audio and video modalities coming from a single human speech usually have similar time changes. It means that changes in one of them usually corresponds to changes in the other one. So it is expected that activation coefficient matrices of their NMF decomposition are similar. Based on this similarity, in this paper the activation coefficient matrix of the video modality is used as an initialization for audio source separation via NMF. In addition, the mentioned similarity is used for post-processing and for clustering the rows... 

    Multimodal soft nonnegative matrix go-factorization for convolutive source separation

    , Article IEEE Transactions on Signal Processing ; Volume 65, Issue 12 , 2017 , Pages 3179-3190 ; 1053587X (ISSN) Sedighin, F ; Babaie Zadeh, M ; Rivet, B ; Jutten, C ; Sharif University of Technology
    In this paper, the problem of convolutive source separation via multimodal soft Nonnegative Matrix Co-Factorization (NMCF) is addressed. Different aspects of a phenomenon may be recorded by sensors of different types (e.g., audio and video of human speech), and each of these recorded signals is called a modality. Since the underlying phenomenon of the modalities is the same, they have some similarities. Especially, they usually have similar time changes. It means that changes in one of them usually correspond to changes in the other one. So their active or inactive periods are usually similar. Assuming this similarity, it is expected that the activation coefficient matrices of their... 

    Formation of a catalytically active intermediate for oxidation in H2O2/ionic liquid system: experimental and theoretical investigations

    , Article Research on Chemical Intermediates ; Volume 43, Issue 4 , 2017 , Pages 2615-2625 ; 09226168 (ISSN) Alinezhad, H ; Vafaeezadeh, M ; Mahmoodi Hashemi, M ; Sharif University of Technology
    Springer Netherlands  2017
    Abstract: A metal-free method for activation of hydrogen peroxide (H2O2) is introduced using piperidinium trifluoroacetate (PPHTFA) ionic liquid as catalyst. The catalyst has been used for selective oxidation of thioanisole to its corresponding sulfoxide at room temperature. It was found that the selectivities were reduced by increasing the reaction temperature. In this work, no organic solvents or metallic salts were used for activation of H2O2. Mechanistic studies suggested that the reaction proceeds via in situ formation of trifluoro hydroperoxy species as an active catalytic intermediate. Formation of the catalytic intermediate was screened by NMR, IR and Mass Spectroscopy analysis.... 

    A Mechanobiological model for damage-induced growth in arterial tissue with application to in-stent restenosis

    , Article Journal of the Mechanics and Physics of Solids ; Volume 101 , 2017 , Pages 311-327 ; 00225096 (ISSN) Fereidoonnezhad, B ; Naghdabadi, R ; Sohrabpour, S ; Holzapfel, G. A ; Sharif University of Technology
    Elsevier Ltd  2017
    In-stent restenosis (ISR) is one of the main drawbacks of stent implementation which limits the long-term success of the procedure. Morphological changes occurring within the arterial wall due to stent-induced mechanical injury are a major cause for activation of vascular smooth muscle cells (VSMCs), and the subsequent development of ISR. Considering the theory of volumetric mass growth and adopting a multiplicative decomposition of the deformation gradient into an elastic part and a growth part, we present a mechanobiological model for ISR. An evolution equation is developed for mass growth of the neointima, in which the activation of VSMCs due to stent-induced damage (injury) and the... 

    Fabrication and the electrochemical activation of network-like MnO2 nanoflakes as a flexible and large-area supercapacitor electrode

    , Article Journal of Solid State Electrochemistry ; Volume 22, Issue 11 , 2018 , Pages 3507-3514 ; 14328488 (ISSN) Mardi, S ; Moradlou, O ; Moshfegh, A. Z ; Sharif University of Technology
    Porous network-like MnO2 thick films are successfully synthesized on a flexible stainless steel (SS) mesh using a simple and low-cost electrodeposition method followed by an electrochemical activation process. Morphology, chemical composition, and crystal structure of the prepared electrodes before and after the activation process are determined and compared by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The results show that the implementation of the electrochemical activation process does not change the chemical composition and crystal structure of the films, but it influences the surface morphology of the MnO2... 

    Bounds on the approximation power of feed forward neural networks

    , Article 35th International Conference on Machine Learning, ICML 2018, 10 July 2018 through 15 July 2018 ; Volume 8 , 2018 , Pages 5531-5539 ; 9781510867963 (ISBN) Mehrabi, M ; Tchamkerten, A ; Isvand Yousefi, M ; Sharif University of Technology
    International Machine Learning Society (IMLS)  2018
    The approximation power of general feedforward neural networks with piecewise linear activation functions is investigated. First, lower bounds on the size of a network are established in terms of the approximation error and network depth and width. These bounds improve upon state- of-the-art bounds for certain classes of functions, such as strongly convex functions. Second, an upper bound is established on the difference of two neural networks with identical weights but different activation functions. © The Author(s) 2018  

    Coupled hydro-mechanical analysis of underground gas storage at Sarajeh field, Qom formation, Iran

    , Article Journal of Natural Gas Science and Engineering ; Volume 92 , 2021 ; 18755100 (ISSN) Bakhtiari, M ; Shad, S ; Zivar, D ; Razaghi, N ; Sharif University of Technology
    Elsevier B.V  2021
    Production or injection of fluids from/in an underground storage site causes variations of pore pressure and stress states. These fluctuations significantly affect implications for hydraulic fracturing, wellbore integrity, top surface subsidence and heave, fault-reactivation, and stability of reservoir and caprock. Therefore, in order to keep optimal conditions during the process of gas injection and production, it is of paramount importance to have accurate estimates of the pore pressure. In this investigation, coupled fluid flow and geomechanical simulations, as well as rock mechanical tests, are performed on the Sarajeh field, Iran to investigate the geomechanical behavior of the Sarajeh... 

    Temperature dependence of serrated flow, strain-rate sensitivity and activation volume in a Ti-based bulk metallic glass

    , Article Journal of Non-Crystalline Solids ; Volume 553 , 2021 ; 00223093 (ISSN) Asadi Khanouki, M. T ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
    Elsevier B. V  2021
    In this study, the influence of temperature on serrated flow behavior, strain rate sensitivity (SRS) and effective activation volume in a Ti-based bulk metallic glass (BMG) bent at different strain rates has been investigated. Results reveal that the fundamental origin of shear deformation is related to the time-dependent structural relaxations, which occur during deformation at special temperatures and strain rates. Furthermore, the localized structural relaxation processes at intermediate temperatures cause an inelastic shuffling within cages and mitigate the activation of STZs. The main reason of negative SRS at intermediate temperatures is due to the insufficient time for structural... 

    Subject-specific and function-specific applicability of a hand-forearm musculoskeletal model

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 27, Issue 6 , 2015 ; 10162372 (ISSN) Hosseininejad, S ; Farahmand, F ; Fateh, H. R ; Forogh, B ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2015
    There is ambiguity on the quantitative validity of the predictions revealed by musculoskeletal models for muscle forces. This study investigated the consistency between the predictions of a musculoskeletal model of the upper limb and the experimental data for a number of different subjects and functional tasks. Six normal subjects performed isokinetic eccentric or isotonic concentric contraction tests of the wrist muscles in well controlled conditions, using a robotic apparatus, and the net joint torque and angular velocities, as well as the surface electromyograms (EMG) signals of the muscles, were recorded. The experiments were then simulated using a parametric musculoskeletal model of...