Search for: hierarchical-structures
Total 34 records
Two-level Robust Control of Large-scale Systems
Sharif University of Technology
In this thesis, two-level optimal control of uncertain and non-uncertain large-scale systems is presented. In the proposed two-level approach, using a decomposition/coordination framework, the large-scale system is first decomposed into several interactive subsystems, at the first-level, where a smaller optimization problem is solved at each subsystem. At the second-level, a substitution type prediction method, as a coordination strategy, is used to predict the interaction between subsystems. The coordinator mainly evaluates the next update for the coordination parameters and continues to exchange information with the first-level, so that the overall optimum solution is obtained. It is shown...
Portfolio Management: Combining Hierarchical Models with Prior Hierarchical Structure, M.Sc. Thesis Sharif University of Technology ; Arian, Hamid Reza ; Zamani, Shiva
I investigate methods of integrating prior hierarchical structure into hierarchical portfolio optimization methods. My contributions to the literature are forming a prior hierarchical structure based on investors' priorities and generating a unique representative distance matrix, which can be used as an input to other portfolio optimization methods too. In addition, I use SIC and GICs industry classifications as priory information for S&P500 companies and use them as a complementary input to the Hierarchical Risk Parity model and Hierarchical Equal Risk Contribution and compare the resultant portfolios' performance with (López de Prado, 2019)’s method of integrating prior information and...
Simulation of the Self-organized Critical Models on the
Sharif University of Technology
Moghimi Araghi, Saman
Human’s Brain Network
Self-organized critical phenomena are interesting phenomena which are ubiquitous in nature. Examples include mountain ranges , coastlines and also activities in the hu-man's brain. In these processes, without fine-tuning of any external parameter such as the temperature, the system exhibits critical behavior. In other words, the dynamics of the system, drives it towards an state in which long range correlations in space and scaling behaviors can be seen.The first successful model which could characterize such systems was BTW model, introduced by Bak , Tang and Wiesenfeld in 1987. This model, later named Abelian sandpile model, was very simple and because of this simplicity, a large amount of...
Image Categorization Using Deep Learning, M.Sc. Thesis Sharif University of Technology ; Jafari Siavoshani, Mahdi ; Rabiee, Hamid Reza
The representation of data inﬂuences the explanation factors of data variations. Thus,the success of learner algorithms depends on the data representation. Our main contribution in this thesis is learning of high level and abstract representation using deep structure. One of the fundamental examples of representation learning is the AutoEncoders. The auto-encoder is a rigid framework that doesn’t consider explanation factors in terms of statistical concepts. So, the auto-encoders can be re-interpreted by seeing the decoder as the statistical model of interest. The role of encoder is a mechanism for inference in the model described by the decoder. Our purpose is to design such model with...
Hybrid Multilayer Evolutionary Algorithms and Its Applications in Optimization, M.Sc. Thesis Sharif University of Technology ; Bagheri Shouraki, Saeed
Evolutionary algorithms have gradually established a strong foothold as powerful search methods and have been widely applied to solve problems in many disciplines. By the way the performance of these algorithms in hierarchical applications is not satisfying. In order to improve the performance and applicability, numerous sophisticated mechanisms have been introduced and integrated into EAs. In this thesis we have tried to implement a multilayer evolutionary algorithm in order to overcome the problem. The practical results show this improvement any various aspects.
Two-level robust optimal control of large-scale nonlinear systems, Article IEEE Systems Journal ; Volume 9, Issue 1 , 2015 , Pages 242-251 ; 19328184 (ISSN) ; 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...
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) ; 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,...
Towards a knowledge based approach to style driven architecture design, Article Procedia Computer Science, 5 March 2015 through 6 March 2015 ; Volume 62 , 2015 , Pages 236-244 ; 18770509 (ISSN) ; Habibi, J ; Alidoosti, R ; Parvizi Mosaed, A ; Bahrami, M ; Sharif University of Technology
Nowadays, knowledge is the key to success in all software engineering processes. This valuable knowledge, obtained through analysis, design, development, and maintenance processes of the system, should be saved and reused in designing and developing current and similar systems. Using pre-existing knowledge is a practical approach which reduces design complexity, improves software architecture design and manages software quality. In this paper, we describe an approach to create architecture design knowledge using a hierarchical structure of architectural styles based on quality attributes. Knowledge is most importance asset of our approach that reuses similar domains, correlates architectures...
Three-dimensional bioprinting of functional skeletal muscle tissue using gelatin methacryloyl-alginate bioinks, Article Micromachines ; Volume 10, Issue 10 , 2019 ; 2072666X (ISSN) ; 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...
Swing up and arm trajectory tracking of the furuta pendulum with sliding mode control, Article 5th RSI International Conference on Robotics and Mechatronics, IcRoM 2017, 25 October 2017 through 27 October 2017 ; 2018 , Pages 346-351 ; 9781538657034 (ISBN) ; Nikzad Goltapeh, A ; Sharif University of Technology
In this paper, the swing-up problem of the Furuta pendulum has been solved by introducing a new combined method based on the frequency response, and the sliding mode method. Furthermore, a trajectory tracking controller has been introduced and applied to the Furuta pendulum; which the pendulum remained regulated at the upward position, while the arm tracks a desired time-varying trajectory. The hierarchical sliding mode control (HSMC) approach has been employed to achieve the mentioned goals. The Furuta system is made up of two subsystems. Based on this physical structure, the hierarchical structure of the sliding surfaces is designed as follows: first, the sliding surface of each subsystem...
State of the art review on design and manufacture of hybrid biomedical materials: Hip and knee prostheses, Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 231, Issue 9 , 2017 , Pages 785-813 ; 09544119 (ISSN) ; Farahmand, F ; Sharif University of Technology
The trend in biomaterials development has now headed for tailoring the properties and making hybrid materials to achieve the optimal performance metrics in a product. Modern manufacturing processes along with advanced computational techniques enable systematical fabrication of new biomaterials by design strategy. Functionally graded materials as a recent group of hybrid materials have found numerous applications in biomedical area, particularly for making orthopedic prostheses. This article, therefore, seeks to address the following research questions: (RQ1) What is the desired structure of orthopedic hybrid materials? (RQ2) What is the contribution of the literature in the development of...
Searching for galactic hidden gas through interstellar scintillation: the OSER project, Article Proceedings of Science, 18 August 2008 through 22 August 2008, Stockholm ; 2008 ; 18248039 (ISSN) ; Ansari, R ; Habibi, F ; Sharif University of Technology
Considering the results of baryonic compact massive objects searches through microlensing , cool molecular hydrogen (H2 - He) clouds should now be seriously considered as a possible major component of the Galactic hidden matter. It has been suggested that a hierarchical structure of cold H 2 could fill the Galactic thick disk  or halo , providing a solution for the Galactic hidden matter problem. This gas should form transparent "clumpuscules" of ∼ 10 AU size, with a column density of 1024-25cm-2, and a surface filling factor smaller than 1%. The OSER project (Optical Scintillation by Extraterrestrial Refractors) is proposed to search for scintillation of extra-galactic sources...
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 ; 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...
Preparation and characterization of superhydrophobic and highly oleophobic FEVE-SiO2 nanocomposite coatings, Article Progress in Organic Coatings ; Volume 138 , 2020 ; 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...
Photoelectrochemical water-splitting using CuO-Based electrodes for hydrogen production: a review, Article Advanced Materials ; Volume 33, Issue 33 , 2021 ; 09359648 (ISSN) ; 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,...
Mining distributed frequent itemsets using a gossip based protocol, Article Proceedings - IEEE 9th International Conference on Ubiquitous Intelligence and Computing and IEEE 9th International Conference on Autonomic and Trusted Computing, UIC-ATC 2012 ; 2012 , Pages 780-785 ; Mirian Hosseinabadi, S. H ; Mashayekhi, H ; Habibi, J ; Sharif University of Technology
Recently, there has been a growing attention in frequent itemset mining in distributed systems. In this paper, we present an algorithm to extract frequent itemsets from large distributed datasets. Our algorithm uses gossip as the communication mechanism and does not rely on any central node. In gossip based communication, nodes repeatedly select other random nodes in the system, and exchange information with them. Our algorithm proceeds in rounds and provides all nodes with the required support counts of itemsets, such that each node is able to extract the global frequent itemsets. For local iteration and generation of candidate itemsets, a trie data structure is used, which facilitates 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) ; Ahmadian, M. T ; Firozbakhsh, K ; Aghdam, M. M ; Sharif University of Technology
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...
Influence of new superhydrophobic micro-structures on delaying ice formation, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 595 , 2020 ; 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...
Highly concurrent latency-tolerant register files for GPUs, Article ACM Transactions on Computer Systems ; Volume 37, Issue 1-4 , 2021 ; 07342071 (ISSN) ; Mirhosseini, A ; Hajiabadi, A ; Ehsani, S. B ; Falahati, H ; Sarbazi Azad, H ; Drumond, M ; Falsafi, B ; Ausavarungnirun, R ; Mutlu, O ; Sharif University of Technology
Association for Computing Machinery 2021
Graphics Processing Units (GPUs) employ large register files to accommodate all active threads and accelerate context switching. Unfortunately, register files are a scalability bottleneck for future GPUs due to long access latency, high power consumption, and large silicon area provisioning. Prior work proposes hierarchical register file to reduce the register file power consumption by caching registers in a smaller register file cache. Unfortunately, this approach does not improve register access latency due to the low hit rate in the register file cache. In this article, we propose the Latency-Tolerant Register File (LTRF) architecture to achieve low latency in a two-level hierarchical...
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) ; 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...