Search for: geometrical-features
0.009 seconds

    Real-time Vision-based Approach for Estimating Tool-tissue Contact Force with Application to Laparoscopic Surgery

    , M.Sc. Thesis Sharif University of Technology Taheri, Mohammad (Author) ; Behzadipour, Saeed (Supervisor)
    Lack of force feedback during minimally invasive procedures is one of the downsides of such interventions and might result to excessive damage to surrounding tissues. The goal of the present research is to introduce a vision-based approach to estimate contact forces on soft tissues. In this approach, a model was developed in which, image of deformation of a sample soft tissue, under the jaws of laparoscopic gripper, is the input and the output is the gripper force. In this work, a FEM of soft tissue in contact with jaws of a laparoscopic tool is developed. . In the model, the effects of friction between the tool and tissue is considered which was not included in the previous studies. After... 

    Water propagation in two-dimensional petroleum reservoirs

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 445 , 2016 , Pages 102-111 ; 03784371 (ISSN) Najafi, M. N ; Ghaedi, M ; Moghimi Araghi, S ; Sharif University of Technology
    In the present paper we investigate the problem of water propagation in 2 dimensional (2D) petroleum reservoir in which each site has the probability p of being occupied. We first analyze this propagation pattern described by Darcy equations by focusing on its geometrical features. We find that the domain-walls of this model at p=pc ≃ 0.59 are Schramm-Loewner evolution (SLE) curves with κ=3.05 ∓ 0.1 consistent with the Ising universality class. We also numerically show that the fractal dimension of these domain-walls at p=pc is Df ≃ 1.38 consistent with SLEκ=3. Along with this analysis, we introduce a self-organized critical (SOC) model in which the water movement is modeled by a chain of... 

    Vibration analysis of a composite Timoshenko beam with actuating layers under motion of a uniformlly traveling partially disributed mass

    , Article ASME International Mechanical Engineering Congress and Exposition, IMECE 2007, Seattle, WA, 11 November 2007 through 15 November 2007 ; Volume 9 PART C , 2008 , Pages 1933-1942 ; 0791843033 (ISBN); 9780791843031 (ISBN) Ahmadian, M. T ; Pirbodaghi, T ; Paak, M ; Hassanpour, S ; Sharif University of Technology
    In this paper, a thorough investigation of response of a composite Timoshenko simply-supported beam with actuating layers, under the motion of a partially distributed mass is studied and a control system based on the feedback of beam's deflection velocity is applied to alleviate and suppress the vibration of the beam in either case when the mass is still traveling on the beam or departed the beam. The actuating layers are made up of Terfenol-D smart material which are sensitive to magnetic field (magnetostrictive materials) and this trait makes them very suitable to be used for vibration control. They introduce damping to the system through which the energy of system dissipates. The response... 

    Tolerance analysis of mechanical assemblies based on fuzzy - Small degrees of freedom (F-SDOF) model

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 12 November 2010 through 18 November 2010 ; Volume 3, Issue PARTS A AND B , 2010 , Pages 519-524 ; 9780791844274 (ISBN) Khodaygan, S ; Movahhedy, M. R ; Sharif University of Technology
    Tolerances naturally generate an uncertain environment for design and manufacturing. In this paper, a novel fuzzy based tolerance representation approach for modeling the variations of geometric features due to dimensional tolerances is presented. The two concepts of fuzzy theory and small degrees of freedom are combined to introduce the fuzzy-small degrees of freedom model (F-SDOF). This model is suitable for tolerance analysis of mechanical assemblies with linear and angular tolerances. The presented method is compatible with the current dimensioning and tolerancing standards. The application of the proposed methodology is illustrated through presenting an example problem  

    Numerical study of aero- acoustic characteristics in an automotive air-intake system

    , Article 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life ; Volume 7 , 2013 , Pages 5990-5999 ; 9781632662675 (ISBN) Jahani, K ; Beigmoradi, S ; Sharif University of Technology
    OAL-Osterreichischer Arbeitsring fur Larmbekampfung  2013
    Compartment noise has gained significant importance to meet customer expectation. One of the dominant sources of noise from whole engine as a system is the one which is induced from fresh air intake. Geometrical features in air induction systems (AIS) airflow path are often responsible for unusual noise due to the complex air flow structure and its interaction with the internal acoustic field. To reduce air intake noise basically resonator and expansion chamber are used on automotive vehicles. Resonators are widely used for noise reduction of air induction systems. Although, airflow bench tests are faster to evaluate various alternate design geometries, understanding the mechanism of such... 

    Numerical simulation for efficient mixing of newtonian and non-Newtonian fluids in an electro-osmotic micro-mixer

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 107 , 2016 , Pages 11-20 ; 02552701 (ISSN) Shamloo, A ; Mirzakhanloo, M ; Dabirzadeh, M. R ; Sharif University of Technology
    Elsevier  2016
    The present study, deals with a new mixing technique using a two-phase electrode array, which is charged with alternating current (AC) signals, located in specific parts of the geometry. This significantly contributes to a chaotic mixing mechanism using a low amplitude AC voltage within a micro-channel. Study analysis demonstrates that the optimization of the effective parameters such as geometrical features, voltage amplitude, fluid inlet velocity, AC frequency and phase lag for a defined fluid can lead to an optimum and highly efficient mixer by considerably increasing disturbances in a primary highly ordered laminar flow. Three different geometries of micro mixer are studied; one-ring... 

    Microstructure and mechanical properties of copper processed by twist extrusion with a reduced twist-line slope

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 4 , 2014 , pp. 2232-2241 ; Online ISSN: 1543-1940 Latypov, M. I ; Yoon, E. Y ; Lee, D. J ; Kulagin, R ; Beygelzimer, Y ; Seyed Salehi, M ; Kim, H. S ; Sharif University of Technology
    Pure copper processed by a twist extrusion process with a reduced twist-line slope is investigated. Twist extrusion is a severe plastic deformation technique which is promising for scale-up because it allows for processing of relatively large metallic bars. On the way to commercialization, decreasing costs associated with processing is critical for twist extrusion. As one of the measures, reducing the twist-line slope - an important geometrical feature of twist extrusion - can be advantageous in terms of processing costs. The current study seeks to elucidate effects of reducing the twist-line slope on the microstructure, mechanical properties, and their heterogeneity in the processed metal,... 

    Healthy and diseasedin vitromodels of vascular systems

    , Article Lab on a Chip ; Volume 21, Issue 4 , 2021 , Pages 641-659 ; 14730197 (ISSN) Hosseini, V ; Mallone, A ; Nasrollahi, F ; Ostrovidov, S ; Nasiri, R ; Mahmoodi, M ; Haghniaz, R ; Baidya, A ; Salek, M. M ; Darabi, M. A ; Orive, G ; Shamloo, A ; Dokmeci, M. R ; Ahadian, S ; Khademhosseini, A ; Sharif University of Technology
    Royal Society of Chemistry  2021
    Irregular hemodynamics affects the progression of various vascular diseases, such atherosclerosis or aneurysms. Despite the extensive hemodynamics studies on animal models, the inter-species differences between humans and animals hamper the translation of such findings. Recent advances in vascular tissue engineering and the suitability ofin vitromodels for interim analysis have increased the use ofin vitrohuman vascular tissue models. Although the effect of flow on endothelial cell (EC) pathophysiology and EC-flow interactions have been vastly studied in two-dimensional systems, they cannot be used to understand the effect of other micro- and macro-environmental parameters associated with... 

    Fuzzy-small degrees of freedom representation of linear and angular variations in mechanical assemblies for tolerance analysis and allocation

    , Article Mechanism and Machine Theory ; Volume 46, Issue 4 , April , 2011 , Pages 558-573 ; 0094114X (ISSN) Khodaygan, S ; Movahhedy, M. R ; Foumani, M. S ; Sharif University of Technology
    Tolerances naturally generate an uncertain environment for design and manufacturing. In this paper, a novel fuzzy based tolerance representation approach for modeling the variations of geometric features due to dimensional tolerances is presented. The two concepts of fuzzy theory and small degrees of freedom are combined to introduce the fuzzy-small degrees of freedom model (F-SDOF). This model is suitable for tolerance analysis of mechanical assemblies with linear and angular tolerances. Based on the fuzzy concept, a new index (called the assemblability index) is introduced which signifies the fitting quality of parts in the assembly. Graphical and numerical representations of tolerance... 

    Experimental and numerical investigation of hydrodynamic performance of a new surface piercing propeller family

    , Article Ocean Engineering ; Volume 264 , 2022 ; 00298018 (ISSN) Seif, M. S ; Teimouri, M ; Sharif University of Technology
    Elsevier Ltd  2022
    Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation... 

    Direct evidence for conformal invariance of avalanche frontiers in sandpile models

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 79, Issue 3 , Volume 79, Issue 3 , 2009 ; 15393755 (ISSN) Saberi, A.A ; Moghimi-Araghi, S ; Dashti-Naserabadi, H ; Rouhani, S ; Sharif University of Technology
    Appreciation of stochastic Loewner evolution (SLEκ), as a powerful tool to check for conformal invariant properties of geometrical features of critical systems has been rising. In this paper we use this method to check conformal invariance in sandpile models. Avalanche frontiers in Abelian sandpile model are numerically shown to be conformally invariant and can be described by SLE with diffusivity κ=2. This value is the same as value obtained for loop-erased random walks. The fractal dimension and Schramm's formula for left passage probability also suggest the same result. We also check the same properties for Zhang's sandpile model. © 2009 The American Physical Society