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mathematical-models
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Analytical modeling of strength in randomly oriented PP and PPTA short fiber reinforced gypsum composites
, Article Computational Materials Science ; Volume 50, Issue 5 , 2011 , Pages 1619-1624 ; 09270256 (ISSN) ; Sangghaleh, A ; Nazari, A ; Pourjavad, N ; Sharif University of Technology
Abstract
Fiber reinforced gypsum are prevalent building materials in which short fibers with high tensile strength are embedded into a gypsum matrix to produce supplemental strong and lightweight construction materials. Due to confrontation to a rising risk of death and economic disaster in earthquake-prone areas, quake-resistant materials and structures should be employed for building constructions. Gypsum based composites as a unique candidate for this purpose reduce the risks and produce much confident construction materials for residential buildings. In this work tensile strength of gypsum composites with different volume fraction of polypropylene (PP) and poly-paraphenylene terephthalamide...
Predictive equations to estimate spinal loads in symmetric lifting tasks
, Article Journal of Biomechanics ; Volume 44, Issue 1 , Jan , 2011 , Pages 84-91 ; 00219290 (ISSN) ; Plamondon, A ; Shirazi Adl, A ; Larivière, C ; Parnianpour, M ; Sharif University of Technology
2011
Abstract
Response surface methodology is used to establish robust and user-friendly predictive equations that relate responses of a complex detailed trunk finite element biomechanical model to its input variables during sagittal symmetric static lifting activities. Four input variables (thorax flexion angle, lumbar/pelvis ratio, load magnitude, and load position) and four model responses (L4-L5 and L5-S1 disc compression and anterior-posterior shear forces) are considered. Full factorial design of experiments accounting for all combinations of input levels is employed. Quadratic predictive equations for the spinal loads at the L4-S1 disc mid-heights are obtained by regression analysis with adequate...
Turbulent flow in converging nozzles, part one: Boundary layer solution
, Article Applied Mathematics and Mechanics (English Edition) ; Volume 32, Issue 5 , 2011 , Pages 645-662 ; 02534827 (ISSN) ; Farhanieh, B ; Firoozabadi, B ; Sharif University of Technology
2011
Abstract
The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer assumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The...
Competitive distribution system planning model integration of dg, interruptible load and voltage regulator devices
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 34, Issue 6 , 2010 , Pages 619-635 ; 10286284 (ISSN) ; Porkar, S ; Abbaspour Tehrani Fard, A ; Poure, P ; Saadate, S ; Sharif University of Technology
Abstract
Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies, and new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economical fields, it is reasonable to consider Distributed Generation (DG) as a viable option to solve the lacking electric power supply problem. This paper presents a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an...
Linear and non-linear vibration and frequency response analyses of microcantilevers subjected to tip-sample interaction
, Article International Journal of Non-Linear Mechanics ; Volume 45, Issue 2 , 2010 , Pages 176-185 ; 00207462 (ISSN) ; Mahmoodi, S. N ; Jalili, N ; Zohoor, H ; Sharif University of Technology
2010
Abstract
Despite their simple structure and design, microcantilevers are receiving increased attention due to their unique sensing and actuation features in many MEMS and NEMS. Along this line, a non-linear distributed-parameters modeling of a microcantilever beam under the influence of a nanoparticle sample is studied in this paper. A long-range Van der Waals force model is utilized to describe the microcantilever-particle interaction along with an inextensibility condition for the microcantilever in order to derive the equations of motion in terms of only one generalized coordinate. Both of these considerations impose strong nonlinearities on the resultant integro-partial equations of motion. In...
Joint edge detection and motion estimation of cardiac MR image sequence by a phase field method
, Article Computers in Biology and Medicine ; Volume 40, Issue 1 , 2010 , Pages 21-28 ; 00104825 (ISSN) ; Jahed, M ; Preusser, T ; Sharif University of Technology
Abstract
In this paper a variational framework for joint segmentation and motion estimation is employed for inspecting heart in Cine MRI sequences. A functional including Mumford-Shah segmentation and optical flow based dense motion estimation is approximated using the phase-field technique. The minimizer of the functional provides an optimum motion field and edge set by considering both spatial and temporal discontinuities. Exploiting calculus of variation principles, multiple partial differential equations associated with the Euler-Lagrange equations of the functional are extracted, first. Next, the finite element method is used to discretize the resulting PDEs for numerical solution. Several...
Sagittal range of motion of the thoracic spine using inertial tracking device and effect of measurement errors on model predictions
, Article Journal of Biomechanics ; Volume 49, Issue 6 , 2016 , Pages 913-918 ; 00219290 (ISSN) ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
Abstract
Range of motion (ROM) of the thoracic spine has implications in patient discrimination for diagnostic purposes and in biomechanical models for predictions of spinal loads. Few previous studies have reported quite different thoracic ROMs. Total (T1-T12), lower (T5-T12) and upper (T1-T5) thoracic, lumbar (T12-S1), pelvis, and entire trunk (T1) ROMs were measured using an inertial tracking device as asymptomatic subjects flexed forward from their neutral upright position to full forward flexion. Correlations between body height and the ROMs were conducted. An effect of measurement errors of the trunk flexion (T1) on the model-predicted spinal loads was investigated. Mean of peak voluntary total...
Theoretical modeling of actin-retrograde-flow passing clusters of confined T cell receptors
, Article Mathematical Biosciences ; Volume 283 , 2017 , Pages 1-6 ; 00255564 (ISSN) ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
Elsevier Inc
2017
Abstract
Through the activation process of T cells, actin filaments move from the cell periphery toward the cell center. The moving filaments engage with T cell receptors and thus contribute to transportation of the signaling molecules. To study the connection between the moving actin filaments and T cell receptors, an experiment available in the literature has measured filaments flow velocity passing over a region of confined clusters of receptors. It shows that flow velocity decreases in the proximity of the receptors, and then regains its normal value after traversing the region, suggesting a dissipative friction-like connection. In this work, we develop a minimal theoretical model to re-examine...
A novel regression imputation framework for Tehran air pollution monitoring network using outputs from WRF and CAMx models
, Article Atmospheric Environment ; Volume 187 , 2018 , Pages 24-33 ; 13522310 (ISSN) ; Karimi, S ; Hosseini, V ; Yazgi, D ; Torbatian, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Missing or incomplete data in short or long intervals is a common problem in measuring air pollution. Severe issues may arise when dealing with missing data for time-series prediction schemes or mean analysis. This study aimed to develop a new regression imputation framework to impute missing values in the hourly air quality data set of Tehran and enhance the applicability of Tehran Air Pollution Forecasting System (TAPFS). The proposed framework was designed based on three types of features including measurements of other stations, WRF and CAMx physical models. In this framework, elastic net and neuro-fuzzy networks were efficiently combined in a two-layer structure. The framework was...
Modeling, simulation, and employing dilution–dialysis microfluidic chip (DDMC) for heightening proteins refolding efficiency
, Article Bioprocess and Biosystems Engineering ; Volume 41, Issue 5 , 2018 , Pages 707-714 ; 16157591 (ISSN) ; Masoudi, M. M ; Shamloo, A ; Habibi Rezaei, M ; Moosavi Movahedi, A. A ; Sharif University of Technology
Springer Verlag
2018
Abstract
Miniaturized systems based on the principles of microfluidics are widely used in various fields, such as biochemical and biomedical applications. Systematic design processes are demanded the proper use of these microfluidic devices based on mathematical simulations. Aggregated proteins (e.g., inclusion bodies) in solution with chaotropic agents (such as urea) at high concentration in combination with reducing agents are denatured. Refolding methods to achieve the native proteins from inclusion bodies of recombinant protein relying on denaturant dilution or dialysis approaches for suppressing protein aggregation is very important in the industrial field. In this paper, a modeling approach is...
Fully-coupled mathematical modeling of actomyosin-cytosolic two-phase flow in a highly deformable moving Keratocyte cell
, Article Journal of Biomechanics ; Volume 67 , January , 2018 , Pages 37-45 ; 00219290 (ISSN) ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Interaction between intracellular dynamics and extracellular matrix (ECM) generally occurred into very thin fragment of moving cell, namely lamellipodia, enables all movable cells to crawl on ECM. In fast-moving cells such as fish Keratocytes, Lamellipodia including most cell area finds a fan-like shape during migration, with a variety of aspect ratio function of fish type. In this work, our purpose is to present a novel and more complete two-dimensional continuum mathematical model of actomyosin-cytosolic two-phase flow of a self-deforming Keratocyte with circular spreaded to steady fan-like shape. In the new approach, in addition to the two-phase flow of the F-actin and cytosol, the...
Effect of different geometries in simulation of 3D viscous flow in francis turbine runners
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 363-369 ; 10263098 (ISSN) ; Dadfar, R ; Pirali, A. P ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
Overall turbine analysis requires large CPU time and computer memory, even in the present days. As a result, choosing an appropriate computational domain accompanied by a suitable boundary condition can dramatically reduce the time cost of computations. This work compares different geometries for numerical investigation of the 3D flow in the runner of a Francis turbine, and presents an optimum geometry with least computational effort and desirable numerical accuracy. The numerical results are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on 3D computation of incompressible internal flows, 1989) in which the geometry and detailed best efficiency...
Automatic segmentation, detection, and diagnosis of abdominal aortic aneurysm (AAA) using convolutional neural networks and hough circles algorithm
, Article Cardiovascular Engineering and Technology ; Volume 10, Issue 3 , 2019 , Pages 490-499 ; 1869408X (ISSN) ; Mohammadi, M ; Dehlaghi, V ; Ahmadi, A ; Sharif University of Technology
Springer New York LLC
2019
Abstract
Purpose: An abdominal aortic aneurysm (AAA) is known as a cardiovascular disease involving localized deformation (swelling or enlargement) of aorta occurring between the renal and iliac arteries. AAA would jeopardize patients’ lives due to its rupturing risk, so prompt recognition and diagnosis of this disorder is vital. Although computed tomography angiography (CTA) is the preferred imaging modality used by radiologist for diagnosing AAA, computed tomography (CT) images can be used too. In the recent decade, there has been several methods suggested by experts in order to find a precise automated way to diagnose AAA without human intervention base on CT and CTA images. Despite great...
Activated carbon/metal-organic framework nanocomposite: Preparation and photocatalytic dye degradation mathematical modeling from wastewater by least squares support vector machine
, Article Journal of Environmental Management ; Volume 233 , 2019 , Pages 660-672 ; 03014797 (ISSN) ; Abdi, J ; Taghizadeh, M ; Taghizadeh, A ; Hayati, B ; Shekarchi, A. A ; Vossoughi, M ; Sharif University of Technology
Academic Press
2019
Abstract
Herein, Kiwi peel activated carbon (AC), Materials Institute Lavoisier (MIL-88B (Fe), and AC/MIL-88B (Fe) composite were synthesized and used as catalysts to degrade Reactive Red 198. The material properties were analyzed by the FTIR, BET-BJH, XRD, FESEM, EDX, TGA, and UV–Vis/DRS. The BET surface area of AC, MIL-88B (Fe) and AC/MIL-88B (Fe) was 1113.3, 150.7, and 199.4 m2/g, respectively. The band gap values (Eg) estimated by Tauc plot method, were obtained 5.06, 4.19 and 3.79 eV for AC, MIL-88B (Fe) and AC/MIL-88B (Fe), respectively. The results indicated that the AC/MIL-88B (Fe) composite had higher photocatalytic activity (99%) than that of pure AC (79%) and MIL-88B (Fe) catalysts (87%)....
A stability-based model of a growing spine with adolescent idiopathic scoliosis: A combination of musculoskeletal and finite element approaches
, Article Medical Engineering and Physics ; Volume 64 , 2019 , Pages 46-55 ; 13504533 (ISSN) ; Rouhi, G ; Arjmand, N ; Adeeb, S ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Using a combined musculoskeletal and finite element (FE) approach, this study aimed to evaluate stability-based muscle forces in a spine with adolescent idiopathic scoliosis (AIS) as compared to a normal spine; and subsequently, determine the effects of stress distribution on the growth plates (GPs) of the growing spine. For this purpose a nonlinear 3D FE model of one normal and one scoliotic thoracolumbar spine, consisting of GPs attached to rigid L1 to L4 vertebrae, were developed using computed tomography images coupled with a growth modulation using the Stokes’ model. Corresponding well with recent in-vivo and in-vitro studies, results of the models predicted intradiscal pressures at the...
Comparison of different lifting analysis tools in estimating lower spinal loads – Evaluation of NIOSH criterion
, Article Journal of Biomechanics ; Volume 112 , 2020 ; Shirazi Adl, A ; Plamondon, A ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Excessive loads on the human spine is recognized as a risk factor for back injuries/pain. Various lifting analysis tools such as musculoskeletal models, regression equations and NIOSH (National Institute for Occupational Safety and Health) lifting equation (NLE) have been proposed to evaluate and mitigate associated risks during manual material handling activities. Present study aims to compare predicted spinal loads from 5 different lifting analysis tools as well as to critically evaluate the NIOSH recommended weight limit (RWL). Spinal loads were estimated under different symmetric/asymmetric lifting tasks in which hand-load mass at each task was set based on RWL from NLE. Estimated...
A three-dimensional statistical volume element for histology informed micromechanical modeling of brain white matter
, Article Annals of Biomedical Engineering ; Volume 48, Issue 4 , 2020 , Pages 1337-1353 ; Farahmand, F ; Ahmadian, M. T ; Sharif University of Technology
Springer
2020
Abstract
This study presents a novel statistical volume element (SVE) for micromechanical modeling of the white matter structures, with histology-informed randomized distribution of axonal tracts within the extracellular matrix. The model was constructed based on the probability distribution functions obtained from the results of diffusion tensor imaging as well as the histological observations of scanning electron micrograph, at two structures of white matter susceptible to traumatic brain injury, i.e. corpus callosum and corona radiata. A simplistic representative volume element (RVE) with symmetrical arrangement of fully alligned axonal fibers was also created as a reference for comparison. A...
ECG denoising and compression using a modified extended Kalman filter structure
, Article IEEE Transactions on Biomedical Engineering ; Volume 55, Issue 9 , September , 2008 , Pages 2240-2248 ; 00189294 (ISSN) ; Shamsollahi, M. B ; Sharif University of Technology
2008
Abstract
This paper presents efficient denoising and lossy compression schemes for electrocardiogram (ECG) signals based on a modified extended Kalman filter (EKF) structure. We have used a previously introduced two-dimensional EKF structure and modified its governing equations to be extended to a 17-dimensional case. The new EKF structure is used not only for denoising, but also for compression, since it provides estimation for each of the new 15 model parameters. Using these specific parameters, the signal is reconstructed with regard to the dynamical equations of the model. The performances of the proposed method are evaluated using standard denoising and compression efficiency measures. For...
Multiple interactive pollutants in water quality trading
, Article Environmental Management ; Volume 42, Issue 4 , 2008 , Pages 620-646 ; 0364152X (ISSN) ; Lence, B. J ; Shamsai, A ; Sharif University of Technology
2008
Abstract
Efficient environmental management calls for the consideration of multiple pollutants, for which two main types of transferable discharge permit (TDP) program have been described: separate permits that manage each pollutant individually in separate markets, with each permit based on the quantity of the pollutant or its environmental effects, and weighted-sum permits that aggregate several pollutants as a single commodity to be traded in a single market. In this paper, we perform a mathematical analysis of TDP programs for multiple pollutants that jointly affect the environment (i.e., interactive pollutants) and demonstrate the practicality of this approach for cost-efficient maintenance of...
Analytical study of dissipative solitary waves
, Article Physica Scripta ; Volume 77, Issue 2 , 2008 ; 00318949 (ISSN) ; Emamzadeh, M. M ; Khorasani, S ; Bobin, J. L ; Amrollahi, R ; Sodagar, M ; Khoshnegar, M ; Sharif University of Technology
2008
Abstract
In this paper, the analytical solution to a new class of nonlinear solitons is presented with cubic nonlinearity, subject to a dissipation term arising as a result of a first-order derivative with respect to time, in the weakly nonlinear regime. Exact solutions are found using the combination of the perturbation and Green's function methods up to the third order. We present an example and discuss the asymptotic behavior of the Green's function. The dissipative solitary equation is also studied in the phase space in the non-dissipative and dissipative forms. Bounded and unbounded solutions of this equation are characterized, yielding an energy conversation law for non-dissipative waves....