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    Experimental investigation of the roles of blood volume and density in finger photoplethysmography

    , Article IEEE Sensors Journal ; Volume 13, Issue 5 , 2013 , Pages 1397-1398 ; 1530437X (ISSN) Keikhosravi, A ; Zahedi, E ; Attar, H. M ; Aghajani, H ; Sharif University of Technology
    Using simultaneous photoplethysmogram (PPG) and pulse transducer signals from the same finger, a high correlation (Mean: 98.6, STD: 1) is obtained between the AC part of the PPG and estimated volume changes (after normalization). These results point to the fact that in the resting fingertip, PPG signal variations are only due to volume changes and that blood density does not change thus has no contribution  

    Introducing an adaptive robust controller for artificial heart

    , Article Proceedings of the IEEE RAS and EMBS International Conference on Biomedical Robotics and Biomechatronics, 24 June 2012 through 27 June 2012 ; June , 2012 , Pages 413-418 ; 21551774 (ISSN) ; 9781457711992 (ISBN) Ravanshadi, S ; Jahed, M ; Sharif University of Technology
    Prolonged and uncontrolled high shear stresses and turbulence can cause hemolysis, while alternating and low-level stresses may contribute to platelet activation and thrombus formation. Such deficiencies are reported for Total Artificial Heart (TAH) systems which are generally not fully capable of dynamic adaptation to sudden pressure and volume changes. This study introduces an adaptive robust controller for a linear motor based TAH (LMTAH) which overcomes such shortcomings. Proposed controller performance is compared with simulated natural heart in normal and stressed physiological conditions. Application of adaptive robust control results in flows with less stress variation and... 

    The measurement of suction stress characteristic curve for a highly collapsible loessial soil

    , Article Geotechnical Special Publication, 17 March 2015 through 21 March 2015 ; Volume GSP 256 , 2015 , Pages 2482-2491 ; 08950563 (ISSN) ; 9780784479087 (ISBN) Haeri, S. M ; Khosravi, A ; Ghazizadeh, S ; Anderson, J. B ; Iskander, M ; Suleiman, M. T ; Laefer, D. F ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2015
    This paper describes results of an advanced suction controlled triaxial test device on a loessial soil in an attempt to define the constitutive relationship between suction stress and matric suction (suction stress characteristic curve) for highly collapsible soils. Due to the presence of void spaces with different degrees of collapse potential within the soil matrix, the collapse phenomenon in loess is believed to be a continuous-stepwise reduction in volume rather than a sudden drop during wetting. Due to this unique volume change behavior, the definition of the suction stress characteristic curve for loess may require a soil-specific experimental testing approach capable of making precise... 

    Hydraulic Behavior of Infilled Fractured Rocks under Unsaturated Conditions

    , Article Joint Geotechnical and Structural Engineering Congress 2016, 14 February 2016 through 17 February 2016 ; 2016 , Pages 1708-1718 ; 9780784479742 (ISBN) Khosravi, A ; Mousavi, S ; Dadashi Serej, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    Slip along fractures or hydrothermal alternation may lead to formation of weak layers of soils intercalated between the existing rock layers. In this situation, characterization of the behavior of rock fractures requires consideration of a complicated interaction of mechanical properties and geometrical characteristics of the fracture, coupled together with the properties of infill materials. Of the most important parameters which may considerably affect the behavior of an infilled fractured rock are the hydraulic properties of the infill material. These properties reflect the water retention ability of the infill material and determine the meniscus arrangements between the particles. This... 

    A critical state constitutive model for the isotropic thermal compression of structured sand–bentonite buffers

    , Article Indian Geotechnical Journal ; Volume 49, Issue 4 , 2019 , Pages 398-408 ; 09719555 (ISSN) Shirasb, A ; Karimi, A. H ; Hamidi, A ; Ahmadi, M. M ; Sharif University of Technology
    Springer  2019
    The sand–bentonite mixture is used as the buffer layer in nuclear waste disposals. The buffer layer, as a non-permeable protective layer, is generally exposed to temperature gradients and the long-term subjection to temperature results in creep and more intact structure for the layer. In the present study, thermally induced structure and its effects on the isotropic compression behavior and volume change behavior of buffer layer are evaluated. Thermal consolidation tests were conducted using a modified triaxial cell capable of handling temperatures up to 90 °C. In order to investigate the effects of thermal gradients on the behavior of the mixture, saturated specimens were cured at constant... 

    Saturated hydraulic conductivity of problematic soils measured by a newly developed low-compliance triaxial permeameter

    , Article Engineering Geology ; Volume 278 , 2020 Sadeghi, H ; AliPanahi, P ; Sharif University of Technology
    Elsevier B.V  2020
    Research on the reliable characterization of saturated permeability has received great yet necessary attention globally. However, most studies were carried out on soils with a volumetric tendency being almost insensitive to water saturation or at least with this hidden assumption. This is clearly not the case when dealing with the two broad categories of problematic soils, including collapsible and expansive soils. As confirmed by previous research, at least one-fifth of the planet comprises of these soils with a relatively fair distribution. Therefore, the main objective of this study is to introduce a low-compliance double cell/burette permeameter to track all volumetric changes during the... 

    Three-dimensional desiccation modeling of very soft soils

    , Article Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering: The Academia and Practice of Geotechnical Engineering ; Volume 1 , 2009 , Pages 421-424 ; 9781607500315 (ISBN) Pak, A ; Samimi, S ; Sharif University of Technology
    Self-weight consolidation and desiccation phenomena of ultra soft soils and slurries have important implications in mining, coastal, and environmental engineering. Disposal of mine tailings behind tailings impoundments, transportation of dredged materials and land reclamation, and disposing of sludge in water/wastewater treatment facilities are some of the engineering applications where self-weight consolidation and desiccation of slurries are of concern. Numerical modeling of desiccation phenomenon is a relatively new subject that enables geotechnical engineers to better manage the large volume of mine tailings, dredged materials, and other slurries that are disposed in confined disposal...