Search for: d-spacing
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    A new method for coverage in wireless sensor networks

    , Article 8th IEEE International Symposium on Dependable, Autonomic and Secure Computing, DASC 2009, 12 December 2009 through 14 December 2009, Chengdu ; 2009 , Pages 369-372 ; 9780769539294 (ISBN) Attarzadeh, N ; Barati, A ; Movaghar, A ; Sharif University of Technology
    The manner of organizing the sensors in the wireless sensor network for increasing the capability and optimized using of the sensors is of great importance. Hence considering coverage parameter in every Wireless Sensor Network (WSN) is extremely essential and critical. The matter of overlapping covered area by sensors in 2D space had been considered until now. This paper is suggested a pattern in which no more are the sensors located at the same surface, but using the 3D geometrical figures like cube, pyramid and etc, in which the sensors were spreading about the different surfaces. Locating the sensors on the different surfaces can be useful under conditions where the space is not in same... 

    3D offline path planning for a surveillance aerial vehicle using B-splines

    , Article International Conference on Advanced Mechatronic Systems, ICAMechS, Luoyang ; 2013 , Pages 306-311 ; 23250682 (ISSN) ; 9781479925193 (ISBN) Nabi Abdolyousefi, R ; Banazadeh, A ; Sharif University of Technology
    This paper presents an offline path planning method in 3D space for a surveillance aerial vehicle. In this method, the aerial vehicle is supposed to visit particular points on the path, and the collision between the vehicle and the fixed obstacles in the environment must be avoided. In order to accomplish the mission, first, the path is generated using B-splines. Then, the feasibility of tracking the designed path for the vehicle is considered by analyzing the vehicle's dynamic constraints, such as limitations on deflections of control surfaces. The analysis is supported by a simulation. Potential extension of the proposed analysis to multiple aerial vehicles has been also discussed at the... 

    Development of a new analytical tool to design hierarchical truss beams for natural frequency

    , Article Journal of Mechanical Science and Technology ; Volume 25, Issue 10 , October , 2011 , Pages 2495-2503 ; 1738494X (ISSN) Fazli, N ; Malaek, S. M. B ; Abedian, A ; Teimouri, H ; Sharif University of Technology
    A set of recursive equations are introduced for optimum design of a wide range of hierarchical truss beams to satisfy a minimum required natural frequency. The design equations are based on a general analytical solution, which are derived based on a critical dimensional analysis. A practical example is examined in both 2D and 3D spaces, which promises substantial mass reduction, as much as 99%, when using high order hierarchical truss beams. The results are verified by numerical evaluation of three case studies. The approach looks also very promising to design nanostructures when it comes to the problems associated with vibration  

    An analytical 3-D model for calculating eddy-current damping force for a magnetic levitation system with permanent magnet

    , Article IEEE Transactions on Magnetics ; Volume 48, Issue 9 , Sept , 2012 , Pages 2472-2478 ; 00189464 (ISSN) Ebrahimian, M ; Khodabakhsh, M ; Vossoughi, G ; Sharif University of Technology
    IEEE  2012
    An analytical solution for obtaining steady-state eddy-current-based force on a levitated permanent magnet above a plate with linear conductivity in the field of an electromagnet having cylindrical symmetry is presented in this paper. In literature, the force due to eddy current in this levitation system have been used for high precision positioning of a levitated permanent magnet without providing an explicit analytical model. In this system, a change in the coil's current and also the motion of the levitated permanent magnet in 3-D space generate eddy current in the plate. A novel explicit solution for obtaining damping forces due to these eddy currents is obtained as a function of... 

    Incorporating multiscale micromechanical approach into PLSNs with different intercalated morphologies

    , Article Journal of Applied Polymer Science ; Volume 119, Issue 6 , September , 2011 , Pages 3347-3359 ; 00218995 (ISSN) Yazdi, A. Z ; Bagheri, R ; Kazeminezhad, M ; Heidarian, D ; Sharif University of Technology
    The objective of the present study is to predict Young's modulus of polymer-layered silicate nanocomposites (PLSNs) containing fully intercalated structures. The particular contribution of this article is to consider the changes in structural parameters of different intercalated morphologies in vicinity of each other. These parameters include aspect ratio of intercalated stacks, number of silicate layers per stack, d-spacing between the layers, modulus of the gallery phase, and volume fraction of each intercalated morphology. To do this, the effective particle concept has been employed and combined with the Mori-Tanaka micromechanical model. It has been shown that the simultaneous effects of... 

    On the sensitivity of the nanostructural parameters on youngg"s modulus of PLSNs in fully intercalated structures

    , Article Journal of Composite Materials ; Volume 43, Issue 24 , 2009 , Pages 2921-2941 ; 00219983 (ISSN) Zehtab Yazdi, A ; Bagheri, R ; Kazeminezhad, M ; Sharif University of Technology
    Polymer-layered silicate nanocomposites have been observed to demonstrate enhanced mechanical properties particularly at low weight fractions of silicate. Experimental and theoretical investigations reveal that numerous structural parameters strongly influence the modulus of such nanocomposites. A multiscale micromechanical model is developed which considers a wide range of different affecting parameters including the particle aspect ratio, the number of silicate layers per stack, the d-spacing ratio between the layers, the penetration of polymer chains along silicate sheets, the intercalation feature, and the particle volume fraction. The developed model illustrates the accuracy and... 

    3D visibility and partial visibility complex

    , Article 2007 International Conference on Computational Science and its Applications, ICCSA 2007, Kuala Lumpur, 26 August 2007 through 29 August 2007 ; September , 2007 , Pages 208-215 ; 0769529453 (ISBN); 9780769529455 (ISBN) Nouribygi, M ; Ghodsi, M ; Sharif University of Technology
    Visibility is an important topic in computer graphics, motion planning, and computational geometry. To deal with the increasing complexity of the scenes considered, some research has been performed in visibility processing in order to accelerate the visibility determination. Two of the most studied such structures are visibility graph and visibility complex. Visibility graph is a fundamental geometric structure which is used in many applications, including illumination and rendering, motion planning, pattern recognition, and sensor networks. While the concept of visibility graph is widely studied for 2D scenes, there is no acceptable equivalence of visibility graph for 3D space. Similarly,... 

    Studies on the oxygen barrier and mechanical properties of low density polyethylene/organoclay nanocomposite films in the presence of ethylene vinyl acetate copolymer as a new type of compatibilizer

    , Article Materials and Design ; Volume 32, Issue 4 , 2011 , Pages 1806-1813 ; 02641275 (ISSN) Dadfar, S. M. A ; Alemzadeh, I ; Reza Dadfar, S. M ; Vosoughi, M ; Sharif University of Technology
    Nanocomposite films based on low density polyethylene (LDPE), containing of 2, 3, and 4. wt.% organoclay (OC) and ethylene vinyl acetate (EVA) copolymer as a new compatibilizer were prepared and characterized using rheological tests, X-ray diffraction, differential scanning calorimetry, oxygen permeation measurements, and tensile tests. There was no exfoliation or intercalation of the clay layers in the absence of EVA, while an obvious increase in d-spacing was observed when the samples were prepared with EVA present. This issue was reflected in the properties of nanocomposites. The oxygen barrier properties of the LDPE/EVA/OC film were significantly better than those of the LDPE/OC film.... 

    Manipulating failure mechanism of rapid prototyped scaffolds by changing nodal connectivity and geometry of the pores

    , Article Journal of Biomechanics ; Volume 45, Issue 16 , 2012 , Pages 2866-2875 ; 00219290 (ISSN) Amirkhani, S ; Bagheri, R ; Zehtab Yazdi, A ; Sharif University of Technology
    The performance of cellular solids in biomedical applications relies strongly on a detailed understanding of the effects of pore topology on mechanical properties. This study aims at characterizing the failure mechanism of scaffolds based on nodal connectivity (number of struts that meet in joints) and geometry of the pores. Plastic models of scaffolds having the same relative density but different cubic and trigonal unit cells were designed and then fabricated via three dimensional (3-D) printing. Unit cells were repeated in different arrangements in 3-D space. An in-situ imaging technique was utilized to study the progressive deformation of the scaffold models. Different nodal...