Search for: hierarchical-structures
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    Three-dimensional bioprinting of functional skeletal muscle tissue using gelatin methacryloyl-alginate bioinks

    , Article Micromachines ; Volume 10, Issue 10 , 2019 ; 2072666X (ISSN) Seyedmahmoud, R ; Çelebi Saltik, B ; Barros, N ; Nasiri, R ; Banton, E ; Shamloo, A ; Ashammakhi, N ; Dokmeci, M. R ; Ahadian, S ; Sharif University of Technology
    MDPI AG  2019
    Skeletal muscle tissue engineering aims to fabricate tissue constructs to replace or restore diseased or injured skeletal muscle tissues in the body. Several biomaterials and microscale technologies have been used in muscle tissue engineering. However, it is still challenging to mimic the function and structure of the native muscle tissues. Three-dimensional (3D) bioprinting is a powerful tool to mimic the hierarchical structure of native tissues. Here, 3D bioprinting was used to fabricate tissue constructs using gelatin methacryloyl (GelMA)-alginate bioinks. Mechanical and rheological properties of GelMA-alginate hydrogels were characterized. C2C12 myoblasts at the density 8 × 106 cells/mL... 

    A lightweight hierarchical authentication scheme for internet of things

    , Article Journal of Ambient Intelligence and Humanized Computing ; Volume 10, Issue 7 , 2019 , Pages 2607-2619 ; 18685137 (ISSN) Akbarzadeh, A ; Bayat, M ; Zahednejad, B ; Payandeh, A ; Aref, M. R ; Sharif University of Technology
    Springer Verlag  2019
    The Internet of Things (IoT) technology enables numerous things with different processing power and storage capacity to communicate and share data with each other. Considering the constrained devices of the IoT network in terms of processing and storage, designing a lightweight authentication scheme is quite important. So in this paper, we propose a lightweight authentication scheme based on Chebyshev Chaotic Maps. In the proposed scheme we apply a hierarchical structure to define different access controls for various entities. We then provide a formal analysis via the BAN logic to show the security of our scheme. Moreover, we compare our proposed scheme with previous ones in terms of... 

    Graphic: Graph-based hierarchical clustering for single-molecule localization microscopy

    , Article 18th IEEE International Symposium on Biomedical Imaging, ISBI 2021, 13 April 2021 through 16 April 2021 ; Volume 2021-April , 2021 , Pages 1892-1896 ; 19457928 (ISSN); 9781665412469 (ISBN) Pourya, M ; Aziznejad, S ; Unser, M ; Sage, D ; Sharif University of Technology
    IEEE Computer Society  2021
    We propose a novel method for the clustering of point-cloud data that originate from single-molecule localization microscopy (SMLM). Our scheme has the ability to infer a hierarchical structure from the data. It takes a particular relevance when quantitatively analyzing the biological particles of interest at different scales. It assumes a prior neither on the shape of particles nor on the background noise. Our multiscale clustering pipeline is built upon graph theory. At each scale, we first construct a weighted graph that represents the SMLM data. Next, we find clusters using spectral clustering. We then use the output of this clustering algorithm to build the graph in the next scale; in... 

    Detection of Apnea Bradycardia from ECG Signals of Preterm Infants Using Layered Hidden Markov Model

    , Article Annals of Biomedical Engineering ; Volume 49, Issue 9 , 2021 , Pages 2159-2169 ; 00906964 (ISSN) Sadoughi, A ; Shamsollahi, M. B ; Fatemizadeh, E ; Beuchée, A ; Hernández, A. I ; Montazeri Ghahjaverestan, N ; Sharif University of Technology
    Springer  2021
    Apnea-bradycardia (AB) is a common complication in prematurely born infants, which is associated with reduced survival and neurodevelopmental outcomes. Thus, early detection or predication of AB episodes is critical for initiating preventive interventions. To develop automatic real-time operating systems for early detection of AB, recent advances in signal processing can be employed. Hidden Markov Models (HMM) are probabilistic models with the ability of learning different dynamics of the real time-series such as clinical recordings. In this study, a hierarchy of HMMs named as layered HMM was presented to detect AB episodes from pre-processed single-channel Electrocardiography (ECG). For... 

    Robust optimal control for large-scale systems with state delay

    , Article Transactions of the Institute of Measurement and Control ; Vol. 36, Issue. 4 , June , 2014 , pp. 551-558 ; ISSN: 01423312 Rahmani, M ; Sadati, N ; Sharif University of Technology
    Optimal control of large-scale uncertain dynamic systems with time delays in states is considered in this paper. For this purpose, a two-level strategy is proposed to decompose the large-scale system into several interconnected subsystems at the first level. Then optimal control inputs are obtained by minimization of convex performance indices in presence of uncertainties, in the form of states and interactions feedback. The solution is achieved by bounded data uncertainty problems, where the uncertainties are only needed to be bounded and it is not required to satisfy the so-called 'matching conditions'. At the second level, a simple substitution-type interaction prediction method is used... 

    Two-level optimal load-frequency control for multi-area power systems

    , Article International Journal of Electrical Power and Energy Systems ; Volume 53, Issue 1 , December , 2013 , Pages 540-547 ; 01420615 (ISSN) Rahmani, M ; Sadati, N ; Sharif University of Technology
    In large-scale power systems, classical centralized control approaches may fail due to geographically distribution of information and decentralized controllers result in sub-optimal solution for load-frequency control (LFC) problems. In this paper, a two-level structure is presented to obtain optimal solution for LFC problems and also reduce the computational complexity of centralized controllers. In this approach, an interconnected multi-area power system is decomposed into several sub-systems (areas) at the first-level. Then an optimization problem in each area is solved separately, with respect to its local information and interaction signals coming from other areas. At the second-level,... 

    Two-level robust optimal control of large-scale nonlinear systems

    , Article IEEE Systems Journal ; Volume 9, Issue 1 , 2015 , Pages 242-251 ; 19328184 (ISSN) Sadati, N ; Rahmani, M ; Saif, M ; Sharif University of Technology
    Finding an optimal control strategy for a nonlinear uncertain system is a challenging problem in the area of nonlinear controller design. In this paper, a two-level control algorithm is developed for robust optimal control of large-scale nonlinear systems. For this purpose, using a decomposition/coordination framework, the large-scale nonlinear system is first decomposed into several smaller subsystems, at the first level, where a closed-form solution as a feedback of states and interactions is obtained to optimize each subsystem. At the second level, a substitution-type prediction method, as a coordination strategy, is used to compensate the nonlinear terms of the system and to predict the... 

    Autonomous unmanned helicopter landing system design for safe touchdown on 6DOF moving platform

    , Article 5th International Conference on Autonomic and Autonomous Systems, ICAS 2009, Valencia, 20 April 2009 through 25 April 2009 ; 2009 , Pages 245-250 ; 9780769535845 (ISBN) Esmailifar, S. M ; Saghafi, F ; Sharif University of Technology
    In this research, an adaptive control system is designed for a safe touchdown of an unmanned helicopter during its landing phase on a 6DOF moving platform. In this paper the landing phase is divided into the approach and touchdown stages. In the first stage, the helicopter tries to attenuate the initial position and direction errors and in the next stage, the platform's attitude is tracked for a safe touchdown. The hierarchical structure of the proposed control system includes supervisory and tracking levels. The supervisory level recognizes the landing stage and the tracking level controls and compensates the errors based on SDRE (State Dependent Riccati Equation) method. The robustness and... 

    A novel superhydrophilic/superoleophobic nanocomposite PDMS-NH2/PFONa-SiO2 coated-mesh for the highly efficient and durable separation of oil and water

    , Article Surface and Coatings Technology ; Volume 394 , 2020 Amirpoor, S ; Siavash Moakhar, R ; Dolati, A ; Sharif University of Technology
    Elsevier B.V  2020
    A surface to separate oil–water mixtures is a global concern and highly needed particularly in oil industries. The present study was conducted to create a novel superhydrophilic/superoleophobic nanocomposite coating on the stainless-steel mesh for the aim of oil/water separation. Different hydrophilic resins along with PFOA as oleophobic agent with 15 flours in its chemical structure and various oxide nanoparticles containing SiO2 and TiO2 at different concentrations were studied to achieve superhydrophilic/superoleophobic surface. The fabricated nanocomposites were fully characterized via field-emission scanning microscopy (FESEM), atomic force microscopy (AFM) and Fourier-transform... 

    Influence of new superhydrophobic micro-structures on delaying ice formation

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 Kamali Moghadam, R ; Taeibi Rahni, M ; Javadi, K ; Davoudian, S. H ; Miller, R ; Sharif University of Technology
    Elsevier B.V  2020
    Drop motion on different types of new proposed micro-structure surfaces has been numerically investigated to find the optimum structure in view point of ice formation delaying. The droplet automatically moves on the inclined surfaces due to gravity forces. To validate the numerical algorithm, three different bench mark problems have been considered. The results indicate that the present algorithm is trustable for the presented numerical simulations. Then the validated numerical approach has been used to simulate droplet motion on nine proposed superhydrophobic surfaces in the same conditions. Comparison the drop motion on different micro-structure surfaces at different time indicate that... 

    Photoelectrochemical water-splitting using CuO-Based electrodes for hydrogen production: a review

    , Article Advanced Materials ; Volume 33, Issue 33 , 2021 ; 09359648 (ISSN) Siavash Moakhar, R ; Hosseini Hosseinabad, S. M ; Masudy Panah, S ; Seza, A ; Jalali, M ; Fallah Arani, H ; Dabir, F ; Gholipour, S ; Abdi, Y ; Bagheri Hariri, M ; Riahi Noori, N ; Lim, Y. F ; Hagfeldt, A ; Saliba, M ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    The cost-effective, robust, and efficient electrocatalysts for photoelectrochemical (PEC) water-splitting has been extensively studied over the past decade to address a solution for the energy crisis. The interesting physicochemical properties of CuO have introduced this promising photocathodic material among the few photocatalysts with a narrow bandgap. This photocatalyst has a high activity for the PEC hydrogen evolution reaction (HER) under simulated sunlight irradiation. Here, the recent advancements of CuO-based photoelectrodes, including undoped CuO, doped CuO, and CuO composites, in the PEC water-splitting field, are comprehensively studied. Moreover, the synthesis methods,... 

    A bio-inspired modular hierarchical structure to plan the sit-to-stand transfer under varying environmental conditions

    , Article Neurocomputing ; Volume 118 , 2013 , Pages 311-321 ; 09252312 (ISSN) Sadeghi, M ; Emadi Andani, M ; Parnianpour, M ; Fattah, A ; Sharif University of Technology
    Human motion planning studies are of considerable importance in producing human-like trajectories for various industrial or clinical applications (e.g. assistive robots). In this case, the capability of Central Nervous System (CNS) in generating a large repertoire of actions can be inspirational to develop more efficient motion planning approaches. Here, inspired by structural and functional modularity in the CNS, a novel modular and hierarchical model is developed to plan the sit-to-stand (STS) transfer under varying environmental conditions. In this model, the planning process is distributed among several functionally simple modules. The cooperation of modules enables the model to plan the... 

    Micromechanics and constitutive modeling of connective soft tissues

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Volume 60 , 2016 , Pages 157-176 ; 17516161 (ISSN) Fallah, A ; Ahmadian, M. T ; Firozbakhsh, K ; Aghdam, M. M ; Sharif University of Technology
    Elsevier Ltd 
    In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical... 

    Preparation and characterization of superhydrophobic and highly oleophobic FEVE-SiO2 nanocomposite coatings

    , Article Progress in Organic Coatings ; Volume 138 , 2020 Ghadimi, M.R ; Dolati, A ; Sharif University of Technology
    Elsevier B.V  2020
    Here, an excellent superhydrophobic and highly oleophobic nanocomposite coating composed of fluoroethylene-vinyl ether (FEVE) resin as a matrix for modified SiO2 nanoparticles was synthesized on a stainless-steel wire mesh substrate via a facile sol-gel method. The surface morphology, microstructure, composition, and roughness of the coatings were investigated by field emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The most efficient coating with superhydrophobicity and high oleophobicity feature indicates the water and oil repellency with contact angles (CAs) of 152° and 141°, respectively, with the high...