Loading...
Search for:
tavakoli--zeinab
0.133 seconds
Total 223 records
Design and Fabrication of Microfluidic System as Concentration Gradient Generator
, M.Sc. Thesis Sharif University of Technology ; Saadatmand, Maryam (Supervisor)
Abstract
According to today’s medicine progress, the need for improving the medical facilities have been increased. Within the human body, the biomolecules concentration gradient is regulating the cell functions. Biological processes such as immune response, wound healing, and cancer metastasis have been affected by the bimolecular concentration gradient. So understanding the cell behavior in the presence of a chemical gradient can improve the understanding from these biological processes, and also would help in medical researches. On the other hand, finding the appropriate dose of the drugs and in some cases finding the most effective drug is a clinical challenge that made a new field of research in...
Using Information Beyond Text to Generate Language Embedding Vectors
, M.Sc. Thesis Sharif University of Technology ; Sameti, Hossein (Supervisor)
Abstract
In this thesis, we introduce a novel Artificial Intelligence (AI) system inspired by the philosophical and psychoanalytical concept of imagination as a ``Re-construction of Experiences". Our AI system is equipped with an imagination-inspired module that bridges the gap between textual inputs and other modalities, enriching the derived information based on previously learned experiences. A unique feature of our system is its ability to formulate independent perceptions of inputs. This leads to unique interpretations of a concept that may differ from human interpretations but are equally valid, a phenomenon we term as ``Interpretable Misunderstanding". We employ large-scale models,...
Optical Injection Phase-Locked Loop Application in Continuous-variable Quantum Key Distributions
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
The primary objective of this thesis is to provide solutions addressing some security loopholes in continuous variables quantum key distribution protocols. The coherent detection method is utilized in this particular quantum key distribution scheme, which is a phase-sensitive detection. To measure in the quantum noise limit in the detection part, we need a local optical oscillator, which must possess a high intensity and a consistent phase correlation with the quantum signal. Therefore, reconstructing the emitter’s reference phase in the receiver’s detection system is considered as one of the most critical challenges in these protocols. In order to attain this goal, in the early versions of...
Investigation of the Performance of Microbial Fuel Cell Based on Shewanella Bacteria with the Aim of Nanostructured Materials
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheila (Supervisor) ; Sanaee, Zeinab (Co-Supervisor)
Abstract
The development of clean, renewable and alternative sources of fossil fuels has increased in recent years due to various factors such as environmental pollution, reduced fossil fuel resources and increased energy consumption. The application of microbial fuel cells is one of the clean energy production methods using renewable sources such as municipal sewage. The microbial fuel cell converts the chemical energy stored in organic materials into electrical energy and simultaneously purifies the sewage. Increasing current density and power density are the most important challenges for microbial fuel cells. In this study, the two biocatalysts of Shewanella Oneidensis MR1 and Escherichia coli...
Organic halides and nanocone plastic structures enhance the energy conversion efficiency and self-cleaning ability of colloidal quantum dot photovoltaic devices
, Article Journal of Physical Chemistry C ; Volume 121, Issue 18 , 2017 , Pages 9757-9765 ; 19327447 (ISSN) ; Simchi, A ; Tavakoli, R ; Fan, Z ; Sharif University of Technology
American Chemical Society
2017
Abstract
This paper presents solid-state ligand exchange of spin-coated colloidal lead sulfide quantum dot (PbS QD) films by methylammonium iodide (MAI) and integration of them in depleted heterojunction solar (DHS) devices having an antireflecting (AR) nanocone plastic structure. Time-resolved photoluminescence measurements determine a shorter lifetime of the charge carries on a semiconductor (TiO2) electron transfer layer for the MAI-passivated QD films as compared with those with long-chain aliphatic or short thiol ligands. Consequently, the DHS device yields improved power conversion efficiency (>125%) relative to oleic-acid-passivated PbS QD films. Using anodized aluminum oxide templates, an...
Surface engineering of TiO2 ETL for highly efficient and hysteresis-less planar perovskite solar cell (21.4%) with enhanced open-circuit voltage and stability
, Article Advanced Energy Materials ; Volume 8, Issue 23 , 2018 ; 16146832 (ISSN) ; Yadav, P ; Tavakoli, R ; Kong, J ; Sharif University of Technology
Wiley-VCH Verlag
2018
Abstract
Interfacial studies and band alignment engineering on the electron transport layer (ETL) play a key role for fabrication of high-performance perovskite solar cells (PSCs). Here, an amorphous layer of SnO2 (a-SnO2) between the TiO2 ETL and the perovskite absorber is inserted and the charge transport properties of the device are studied. The double-layer structure of TiO2 compact layer (c-TiO2) and a-SnO2 ETL leads to modification of interface energetics, resulting in improved charge collection and decreased carrier recombination in PSCs. The optimized device based on a-SnO2/c-TiO2 ETL shows a maximum power conversion efficiency (PCE) of 21.4% as compared to 19.33% for c-TiO2 based device....
Efficient, hysteresis-free, and flexible inverted perovskite solar cells using all-vacuum processing.Efficient, hysteresis-free, and flexible inverted perovskite solar cells using all-vacuum processing
, Article Solar RRL ; 2020 ; Yadav, P ; Prochowicz, D ; Tavakoli, R ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
The fabrication of efficient perovskite solar cells (PSCs) using all-vacuum processing is still challenging due to the limitations in the vacuum deposition of the hole transporting layer (HTL). Herein, inverted PSCs using copper (II) phthalocyanine (CuPC) as an ideal alternative HTL for vacuum processing are fabricated. After proper optimization, a PSC with a power conversion efficiency (PCE) of 20.3% is achieved, which is much better than the PCEs (16.8%) of devices with solution-based CuPC. As it takes a long time to dissolve CuPC in the solution-based device, the evaporation approach has better advantage in terms of fast processing. In addition, the device with the evaporated CuPC HTL...
Efficient perovskite solar cells based on Cdse/Zns quantum dots electron transporting layer with superior UV stability
, Article Physica Status Solidi - Rapid Research Letters ; Volume 14, Issue 6 , 2020 ; Prochowicz, D ; Yadav, P ; Tavakoli, R ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Stability is the main challenge in the field of perovskite solar cells (PSCs). Finding new strategies is required to protect the PSCs from deteriorating agents such as humidity, heating, and illumination. Herein, a new electron transporting layer (ETL), i.e., CdSe/ZnS quantum dots (QDs), is proposed for the fabrication of efficient and stable PSCs. CdSe/ZnS QDs layer not only works as an ETL but also has downshifting property, which can improve both efficiency and stability of the PSCs. Using CdSe/ZnS QDs ETL with green emission, a PSC with maximum power conversion efficiency (PCE) of 18% is achieved. More importantly, the device shows great UV stability, much better than the device with...
Synthesis, Evaluation and Modification of Suitable Metal–Organic Frameworks (MOFS) for Desulfurization of Hydrocarbon Cuts
, M.Sc. Thesis Sharif University of Technology ; Khorashe, Farhad (Supervisor) ; Hajjar, Zeinab (Co-Supervisor) ; Soltanali, Saeed (Co-Supervisor)
Abstract
During fuel combustion, aromatic sulfur compounds in energy fuels convert into sulfur oxides, which cause major environmental problems such as acidic rain, global warming, and air pollution. Absorption desulfurization is one of the promising and economical methods to remove these sulfur compounds from fuels. Metal-organic frameworks (MOFs) are a class of nanoporous materials that are of interest for use as adsorbents due to their high specific surface area, unique surface adsorption properties, high adsorption capacity, tunable porosity, flexible dynamic behavior, and diversity in functional and metal groups. In this research, we first synthesized five metal-organic frameworks, namely...
Multimaterial topology optimization by volume constrained Allen-Cahn system and regularized projected steepest descent method
, Article Computer Methods in Applied Mechanics and Engineering ; Vol. 276 , 2014 , pp. 534-565 ; ISSN: 00457825 ; Sharif University of Technology
2014
Abstract
A new computational algorithm is introduced in the present study to solve multimaterial topology optimization problems. It is based on the penalization of the objective functional by the multiphase volume constrained Ginzburg-Landau energy functional. The update procedure is based on the gradient flow of the objective functional by a fractional step projected steepest descent method. In the first step, the new design is found based on the projected steepest descent method to ensure the reduction in the objective functional, simultaneously satisfying the control constraints. In the second step, regularization step, an H1 regularity of the solution is ensured while keeping the feasibility of...
On the prediction of shrinkage defects by thermal criterion functions
, Article International Journal of Advanced Manufacturing Technology ; Vol. 74, issue. 1-4 , Jun , 2014 , p. 569-579 ; Sharif University of Technology
2014
Abstract
The goal of the present study is to predict the formation of solidification induced defects in castings by thermal criteria functions. In a criterion function method, the heat transfer equation is firstly solved, and then the susceptibility of defect formation at every point in the casting is predicted by computing a local function, criterion function, using results of the thermal analysis. In the first part of the paper, some famous criteria functions, in particular, the Pellini and Niyama criteria, are analyzed and their shortcomings are discussed in details. Then, a new criterion function is suggested to decrease the shape-dependency issue of the former criteria. The feasibility of the...
Computationally efficient approach for the minimization of volume constrained vector-valued Ginzburg-Landau energy functional
, Article Journal of Computational Physics ; Volume 295 , August , 2015 , Pages 355-378 ; 00219991 (ISSN) ; Sharif University of Technology
Academic Press Inc
2015
Abstract
The minimization of volume constrained vector-valued Ginzburg-Landau energy functional is considered in the present study. It has many applications in computational science and engineering, like the conservative phase separation in multiphase systems (such as the spinodal decomposition), phase coarsening in multiphase systems, color image segmentation and optimal space partitioning. A computationally efficient algorithm is presented to solve the space discretized form of the original optimization problem. The algorithm is based on the constrained nonmonotone L2 gradient flow of Ginzburg-Landau functional followed by a regularization step, which is resulted from the Tikhonov regularization...
Unconditionally energy stable time stepping scheme for Cahn-Morral equation: Application to multi-component spinodal decomposition and optimal space tiling
, Article Journal of Computational Physics ; Volume 304 , 2016 , Pages 441-464 ; 00219991 (ISSN) ; Sharif University of Technology
Academic Press Inc
2016
Abstract
An unconditionally energy stable time stepping scheme is introduced to solve Cahn-Morral-like equations in the present study. It is constructed based on the combination of David Eyre's time stepping scheme and Schur complement approach. Although the presented method is general and independent of the choice of homogeneous free energy density function term, logarithmic and polynomial energy functions are specifically considered in this paper. The method is applied to study the spinodal decomposition in multi-component systems and optimal space tiling problems. A penalization strategy is developed, in the case of later problem, to avoid trivial solutions. Extensive numerical experiments...
Optimal design of multiphase composites under elastodynamic loading
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 300 , 2016 , Pages 265-293 ; 00457825 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
An algorithm is proposed to optimize the performance of multiphase structures (composites) under elastodynamic loading conditions. The goal is to determine the distribution of material in the structure such that the time-averaged total stored energy of structure is minimized. A penalization strategy is suggested to avoid the checkerboard instability, simultaneously to generate near 0-1 topologies. As a result of this strategy, the solutions of presented algorithm are sufficiently smooth and possess the regularity of H1 function space. A simple method for the continuum adjoint sensitivity analysis of the corresponding PDE-constrained optimization problem is presented. It is general and can be...
On the coupled continuous knapsack problems: projection onto the volume constrained Gibbs N-simplex
, Article Optimization Letters ; Volume 10, Issue 1 , 2016 , Pages 137-158 ; 18624472 (ISSN) ; Sharif University of Technology
Springer Verlag
2016
Abstract
Coupled continuous quadratic knapsack problems (CCK) are introduced in the present study. The solution of a CCK problem is equivalent to the projection of an arbitrary point onto the volume constrained Gibbs N-simplex, which has a wide range of applications in computational science and engineering. Three algorithms have been developed in the present study to solve large scale CCK problems. According to the numerical experiments of this study, the computational costs of presented algorithms scale linearly with the problem size, when it is sufficiently large. Moreover, they show competitive or even superior computational performance compared to the advanced QP solvers. The ease of...
Thermal optimization of the continuous casting process using distributed parameter identification approach—controlling the curvature of solid-liquid interface
, Article International Journal of Advanced Manufacturing Technology ; Volume 94, Issue 1-4 , 2018 , Pages 1101-1118 ; 02683768 (ISSN) ; Sharif University of Technology
Springer London
2018
Abstract
Thermal optimization of the vertical continuous casting process is considered in the present study. The goal is to find the optimal distribution of the temperature and interfacial heat transfer coefficients corresponding to the primary and secondary cooling systems, in addition to the pulling speed, such that the solidification along the main axis of strand approaches to the unidirectional solidification mode. Unlike many thermal optimization of phase change problems in which the desirable (target) temperature, temperature gradient, or interface position are assumed to be a priori known, a desirable shape feature of the freezing interface (not its explicit position) is assumed to be known in...
Smooth modeling of solidification based on the latent heat evolution approach
, Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 9-12 , 2017 , Pages 3041-3052 ; 02683768 (ISSN) ; Sharif University of Technology
Springer London
2017
Abstract
The regularity problem of heat conduction equation corresponding to modeling of solidification based on the latent heat evolution approach is considered in the present study. It is shown that the corresponding PDE is actually semi-smooth, an issue that has not been taken into account explicitly in the related literature. A general smoothing (regularization) strategy is introduced to solve this problem. More specifically, the smoothed version of the effective heat capacity method is presented in this work. The presented approach is applied to model the quasi steady-state heat transfer problem in the continuous casting process. Numerical experiments demonstrate the success of the presented...
CartGen: Robust, efficient and easy to implement uniform/octree/embedded boundary Cartesian grid generator
, Article International Journal for Numerical Methods in Fluids ; Volume 57, Issue 12 , 30 August , 2008 , Pages 1753-1770 ; 02712091 (ISSN) ; Sharif University of Technology
2008
Abstract
An efficient and easy to implement method to generate Cartesian grids is presented. The presented method generates various kinds of Cartesian grids such as uniform, octree and embedded boundary grids. It supports the variation of grid size along each spatial direction as well as anisotropic and non-graded refinements. The efficiency and ease of implementation are the main benefits of the presented method in contrast to the alternative methods. Regarding octree grid generation, applying a simple and efficient data compression method permits to store all grid levels without considerable memory overhead. The presented method generates octree grids up to a 13-level refinement (81923 grids on the...
Multilayer evaporation of MAFAPbI3-xClx for the fabrication of efficient and large-scale device perovskite solar cells
, Article Journal of Physics D: Applied Physics ; Volume 52, Issue 3 , 2019 ; 00223727 (ISSN) ; Yadav, P ; Prochowicz, D ; Tavakoli, R ; Saliba, M ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
FAPbI3 perovskites are excellent candidates for fabrication of perovskite solar cells (PSCs) with high efficiency and stability. However, these perovskites exhibit phase instability problem at room temperature. In this work, to address this challenge we use methylammonium chloride (MACl) as an additive and employed a layer-by-layer thermal evaporation technique to fabricate high-quality perovskite films on a large scale of 25 cm2. The optimized perovskite films show high crystallinity with large grains in the μm-range and reveals phase stability due to the presence of MACl after the annealing process. Finally, we achieved PSCs with 17.7% and 15.9% for active areas of 0.1 cm2 and 0.8 cm2,...
A Dopant-free hole transporting layer for efficient and stable planar perovskite solar cells
, Article Physica Status Solidi - Rapid Research Letters ; Volume 14, Issue 7 , 2020 ; Si, H ; Yadav, P ; Prochowicz, D ; Tavakoli, R ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Herein, a new dopant-free organic material, PV2000, as a stable hole transporting layer (HTL) for the fabrication of stable and efficient perovskite solar cells (PSCs) is introduced. For this purpose, planar PSCs using a triple-A cation perovskite composition are fabricated and the commonly used 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) HTL is replaced by dopant-free PV2000 polymer. The characterization results disclose that the PV2000 has a great thermal stability, good hole mobility, and suitable band alignment that matches well with the valence band of triple-A cation perovskite. After proper optimization of PV2000 film thickness, a planar PSC...