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mixing
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Numerical simulation of centrifugal serpentine micromixers and analyzing mixing quality parameters
, Article Chemical Engineering and Processing: Process Intensification ; Volume 104 , 2016 , Pages 243-252 ; 02552701 (ISSN) ; Madadelahi, M ; Akbari, A ; Sharif University of Technology
Elsevier, B.V
2016
Abstract
Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular...
Three-dimensional numerical simulation of a novel electroosmotic micromixer
, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 25-33 ; 02552701 (ISSN) ; Madadelahi, M ; Abdorahimzadeh, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Lab-on-a-chip (LOC) systems have been widely used in chemical and medical analyses. In this study, a novel T-shaped electroosmotic micromixer was simulated and the effects of different parameters on the mixing process were examined. These parameters include; inlet angle, number of conducting hurdles, arrangements of the hurdles, geometry of hurdles and chambers, aspect ratios of the channel cross-sectional profile, hurdle radius, and depth. It was found that the inlet angle has a direct influence on mixing index (σ). The effect of various number of hurdles (one, two, three and four hurdles) and their orientations was investigated. Simulations revealed that using two conducting hurdles is the...
Numerical study of ignition process in turbulent shear-less methane-air mixing layer
, Article Flow, Turbulence and Combustion ; Volume 99, Issue 2 , 2017 , Pages 411-436 ; 13866184 (ISSN) ; Tabejamaat, S ; Mani, M ; Farshchi, M ; Sharif University of Technology
Springer Netherlands
2017
Abstract
In this work, ignition process in a turbulent shear-less methane-air mixing layer is numerically investigated. A compressible large eddy simulation method with Smagorinsky sub-grid scale model is used to solve the flow field. Also, a thickened flame combustion model and DRM-19 reduced mechanism are used to compute species distribution and the heat release. Non-reacting mean and RMS axial velocity profiles and mean mixture fraction are validated against experimental data. Instantaneous mixture fraction contours show that the large bursts penetrate from the fuel stream into that of the oxidizer and vice versa and a random behaviour in the cross-stream direction. Flame kernel initiation, growth...
A fast online bandwidth empirical mode decomposition scheme for avoidance of the mode mixing problem
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 20 , 2018 , Pages 3652-3674 ; 09544062 (ISSN) ; Hosseini Kordkheili, S. A ; Navazi, H. M ; Sharif University of Technology
SAGE Publications Ltd
2018
Abstract
The main objective of this work is to propose a scheme to extract intrinsic mode functions of online data with an acceptable speed as well as accuracy. For this purpose, an individual block framework method is firstly employed to extract the intrinsic mode functions. In this method, buffers are selected such that they overlap with their neighbors to prevent the end effect errors with no need for the averaging process. And in order to avoid the mode mixing problem, a bandwidth empirical mode decomposition scheme is developed to effectively improve the results. Through this scheme, an auxiliary function made of both high- and low-frequency components corresponding to noise and dominant...
Shape effect of cavity flameholder on mixing zone of hydrogen jet at supersonic flow
, Article International Journal of Hydrogen Energy ; Volume 43, Issue 33 , 2018 , Pages 16364-16372 ; 03603199 (ISSN) ; Mahyari, A ; Barzegar Gerdroodbary, M ; Abdollahi, A ; Amini, Y ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Cavity flameholder is known as an efficient technique for providing the ignition zone. In this research, computational fluid dynamic is applied to study the influence of the various shapes of cavity as flameholder on the mixing efficiency inside the scramjet. To evaluate different shapes of cavity flame holder, the Reynolds-averaged Navier–Stokes equations with (SST) turbulence model are solved to reveal the effect of significant parameters. The influence of trapezoidal, circle and rectangular cavity on fuel distribution is expansively analyzed. Moreover, the influence of various Mach numbers (M = 1.2, 2 and 3) on mixing rate and flow feature inside the cavity is examined. The comprehensive...
Modeling formulation and a new heuristic for the railroad blocking problem
, Article Applied Mathematical Modelling ; Volume 56 , 2018 , Pages 304-324 ; 0307904X (ISSN) ; Shafahi, Y ; Sharif University of Technology
Elsevier Inc
2018
Abstract
The railroad blocking problem is an important issue at the tactical level of railroad freight transportation. This problem consists of determining paths between the origins and destinations of each shipment to minimize the operating and user costs while satisfying the railroad supply and demand restrictions. A mixed-integer program (MIP) is developed to find the optimal paths, and a new heuristic is developed to solve the proposed model. This heuristic decomposes the model into two sub-problems of manageable size and then provides feasible solutions. We discuss the performance of the proposed heuristic for a set of instances with up to 90 stations. A comparison with the CPLEX MIP solver...
Enhancing active electro-kinetic micro-mixer efficiency by introducing vertical electrodes and modifying chamber aspect ratio
, Article Chemical Engineering and Processing - Process Intensification ; Volume 142 , 2019 ; 02552701 (ISSN) ; Sani, M ; Saidi, M. S ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Micro-mixers are considered as vital components of Micro Total Analysis systems (μTAS). Major objective in the design of micro-mixers is achieving high mixing quality in short mixing times. In this paper, numerical simulation of some micro-mixer designs has been carried out to understand the detailed flow pattern and thereby to propose modifications for improving mixing efficiency. It is well known that inducing convection will provide turbulent like behavior with corresponding mixing enhancement. In micro systems to drive the flow, electro-osmotic force is usually used by introducing electrodes. In this work, mixing electrodes have been implemented to induce convection and eddies. This...
A milp model for incorporating reliability indices in distribution system expansion planning
, Article IEEE Transactions on Power Systems ; Volume 34, Issue 3 , 2019 , Pages 2453-2456 ; 08858950 (ISSN) ; Abbaspour, A ; Fotuhi-Firuzabad, M ; Farzin, H ; Moeini-Aghtaie, M ; Lehtonen, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Reliability cost is considered as an inevitable criterion in expansion planning studies of distribution systems. However, nonlinear expressions of reliability indices aggravate complexity of planning studies. To address this issue, this letter proposes a novel method to linearize mathematical model of the reliability-based distribution expansion planning problem. Using this variant of reliability indices, reliability costs can easily be involved in mixed-integer linear programming model of distribution expansion planning. Validity of the derived expressions is tested by simulation results. © 1969-2012 IEEE
Mixing in a novel double coaxial spinning disks reactor
, Article Chemical Engineering and Processing - Process Intensification ; Volume 159 , February , 2020 ; Molaei Dehkordi, A ; Bagheri Farahani, H ; Sharif University of Technology
Elsevier B. V
2020
Abstract
High mixing efficiency that is of great importance in various industrial processes is a significant feature of spinning disk reactors. This work was focused on the characterization of mixing in a new reactor called Double Spinning Disk Reactor (DSDR) by adopting a competitive parallel reaction system known as iodide–iodate test reaction. The proposed DSDR consists of two coaxial rotating disks that the feeds are introduced into the gap between them. The mixing improves with an increase in the rotational speed of the disk, the radial distance of the feed introduced through the lower disk, and its number of feed points, while an increase in each of the feed flow rate and the distance between...
On the cramer-rao bound for estimating the mixing matrix in noisy sparse component analysis
, Article IEEE Signal Processing Letters ; Volume 15 , 2008 , Pages 609-612 ; 10709908 (ISSN) ; Babaie Zadeh, M ; Haddadi, F ; Jutten, C ; Sharif University of Technology
2008
Abstract
In this letter, we address the theoretical limitations in estimating the mixing matrix in noisy sparse component analysis (SCA) for the two-sensor case. We obtain the Cramer-Rao lower bound (CRLB) error estimation of the mixing matrix. Using the Bernouli-Gaussian (BG) sparse distribution, and some simple assumptions, an approximation of the Fisher information matrix (FIM) is calculated. Moreover, this CRLB is compared to some of the main methods of mixing matrix estimation in the literature. © 2008 IEEE
Optimization-based distribution system reliability evaluation: An enhanced MILP model
, Article 4th International Conference on Smart Energy Systems and Technologies, SEST 2021, 6 September 2021 through 8 September 2021 ; 2021 ; 9781728176604 (ISBN) ; Lehtonen, M ; Fotuhi Firuzabad, M ; Munoz Delgado, G ; Contreras, J ; Arroyo, J. M ; University of Vaasa ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Standard mathematical-programming-based models have attracted considerable attention for optimizing distribution system planning and operation due to their salient advantages. More specifically, mixed-integer linear programming (MILP) has proven very effective in modeling such problems. The availability of optimization software for efficiently solving MILP problems with guaranteed convergence to optimality while providing a measure of the distance to the optimal solution has made MILP models more popular. Although a plethora of efficient MILP formulations have been proposed for planning and operating studies of distribution grids, incorporating reliability into such models is still...
The effect of non-uniform magnetic field on the efficiency of mixing in droplet-based microfluidics: a numerical investigation
, Article Micromachines ; Volume 13, Issue 10 , 2022 ; 2072666X (ISSN) ; Nouri, M ; Hassani Gangaraj, M ; Shamloo, A ; Nasiri, R ; Sharif University of Technology
MDPI
2022
Abstract
Achieving high efficiency and throughput in droplet-based mixing over a small characteristic length, such as microfluidic channels, is one of the crucial parameters in Lab-on-a-Chip (LOC) applications. One solution to achieve efficient mixing is to use active mixers in which an external power source is utilized to mix two fluids. One of these active methods is magnetic micromixers using ferrofluid. In this technique, magnetic nanoparticles are used to make one phase responsive to magnetic force, and then by applying a magnetic field, two fluid phases, one of which is magneto-responsive, will sufficiently mix. In this study, we investigated the effect of the magnetic field’s characteristics...
Performance evaluation during extraction technique in modified rotating disc column: Experimental and mathematical modeling
, Article Chemical Engineering and Processing - Process Intensification ; Volume 171 , 2022 ; 02552701 (ISSN) ; Torkaman, R ; Torab Mostaedi, M ; Saremi, M ; Asadollahzadeh, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this survey, the reactive mass transfer data are determined for extraction technique in the modified rotating disc column. Mathematical models are investigated to compute the mass transfer coefficients of the dispersed phase. An increase in the dispersed phase holdup from 0.85 to 0.12 and a decrease in droplet diameter from 2.24 to 0.74 mm are observed with increasing rotation speed from 170 to 410 rpm in the optimized system. The experiments showed that the optimum transport efficiency in rotor speed of 410 rpm in this column is equal to 98.85% and 99.45% for extraction and stripping stages, respectively. The model's achievement is compared with the solvent extraction data and a...
Iterated Integrals and Periods of Algebraic Fundamental Groups
, M.Sc. Thesis Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
In This thesis, we study first the analytic properties of Iterated integrals on complex line and discuss their shuffle relations and also regularization for divergent integrals, Next we turn in to Mixed Hodge theory and define a Hopf algebra of framed Mixed Hodge -Tate Structures. Associated to any iterated integral ∫ an+1 a0 dt ta1 dt ta2 ::: dttan
we define an n-framed Mixed Hodge-Tate structure denoted by IH(a0; a1; :::; an; an+1) . These structure come from the fundamental group of Cfa1; :::; ang and for this we recall the theory of Chen and Hain for these groups. At the end calculate a coproduct formula for these elements
we define an n-framed Mixed Hodge-Tate structure denoted by IH(a0; a1; :::; an; an+1) . These structure come from the fundamental group of Cfa1; :::; ang and for this we recall the theory of Chen and Hain for these groups. At the end calculate a coproduct formula for these elements
Numerical and Analytical Study of Mixing in Y-shaped Micromixers: Electroosmotic and Poiseuille Flow of PTT Fluids
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
Abstract
Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors...
Hodge Structure on Fundamental Groups
, M.Sc. Thesis Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
Deligne Proved that cohomology groups of algebraic varieties over C have mixed Hodge structures.It is also proved that homotopy groups of these varieties have mixed Hodge structures in a proper sense.In this thesis using iterated integrals that introduced by Chen,we explain Hain’s approach for defining Hodge structures on truncated first homotopy groups(fundamental groups). Note that there is another approach for defining Hodge structures on homotopy groups by Morgan,that uses minimal models of Sullivan.For explaining Hain’s approach,some basic results on Hodge structures are also explained
ISO's optimal strategies for scheduling the hourly demand response in day-ahead markets
, Article IEEE Transactions on Power Systems ; Vol. 29, issue. 6 , 2014 , p. 2636-2645 ; ISSN: 8858950 ; Fotuhi-Firuzabad, M ; Shahidehpour, M ; Sharif University of Technology
Abstract
This paper presents a hierarchical demand response (DR) bidding framework in the day-ahead energy markets which integrates customer DR preferences and characteristics in the ISO's market clearing process. In the proposed framework, load aggregators submit aggregated DR offers to the ISO which would centrally optimize final decisions on aggregators' DR contributions in wholesale markets. The hourly load reduction strategies include load shifting and curtailment and the use of onsite generation and energy storage systems. The ISO applies mixed-integer linear programming (MILP) to the solution of the proposed DR model in the day-ahead market clearing problem. The proposed model is implemented...
Modeling active micromixers with multiple microstirrers using smoothed particle hydrodynamics
, Article Scientia Iranica ; Vol. 21, issue. 4 , 2014 , pp. 1390-1402 ; ISSN: 10263098 ; Pishevar, A ; Saidi, M. S ; Sharif University of Technology
Abstract
The smoothed particle hydrodynamics method is used to explore the effects of design parameters on the mixing efficiency of two types of active micromixer. First, the complex flow field and the mixing process of two separated fluids in a square mixing chamber with nine symmetric microstirrers are simulated. The influence of design parameters, such as the microstirrer rotation arrangement and the angular velocity of the microstirrer, on the mixing performance, is investigated. The mixing index parameter on ten control points is calculated and the average mixing index is compared for different cases. Simulations illustrate that the rotation arrangement of microstirrers is a key parameter in the...
Identity based universal re-encryption for mix nets
, Article 2013 10th International ISC Conference on Information Security and Cryptology, ISCISC 2013 ; Aug , 2013 , 1 - 5 ; Mohajeri, J ; Salmasizadeh, M ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
Universal Re-encryption Cryptosystems do not require the knowledge of the recipient's public key for re-encrypting a ciphertext whereas conventional Re-encryption Cryptosystems need that knowledge. In this paper, we present the first Identity-based Universal Re-encryption Cryptosystem scheme whose re-encryption algorithm does not need to have the knowledge of the recipient's identity. By generalizing the definition of Universal Semantic Security to Identity Based Universal Cryptosystems, we prove the security of our scheme. There are some applications for universal re-encryption cryptosystems which cannot be made using conventional cryptosystems. One significant application of these...
Security analysis of an identity-based mix net
, Article 2013 10th International ISC Conference on Information Security and Cryptology, ISCISC 2013 ; 2013 ; Mahmoodi, A ; Mohajeri, J ; Salmasizadeh, M ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
One of the most important systems for providing anonymous communication is the Mix nets which should provide correctness and privacy as security requirements against active adversaries. In 2009, Zhong proposed a new mix net scheme which uses identity-based cryptographic techniques and proved that it has 'correctness' and 'privacy' properties in the semi-honest model. Since the semi-honest model is a very strong assumption for practical application, we show that if a user or the last mix server is corrupted, Zhong scheme does not provide privacy against an active adversary