Loading...
Search for:
analytical-formulation
0.006 seconds
Prediction of the noise spectrum in optoelectronic oscillators: An analytical conversion matrix approach
, Article Journal of the Optical Society of America B: Optical Physics ; Vol. 31, issue. 8 , August , 2014 , p. 1915-1925 ; ISSN: 07403224 ; Hosseini, S. E ; Banai, A ; Sharif University of Technology
Abstract
In this paper an analytical formulation based on the conversion matrix approach for characterizing the oscillator noise spectra as well as the phase and amplitude noise spectra for a single-loop optoelectronic oscillator (OEO) is presented. The validity of this approach is verified by comparing our results regarding the noise spectra of the OEO against the results of two references in the literature. The first reference presents simulation results, and the second reference presents both simulation and measurement results, and good agreement is seen between the results of the new method and those of the references. The advantage of the new approach is the simplicity of the theory as well as...
Progressive bearing failure modeling of composites with double-bolted joints at mesoscale level
, Article Archive of Applied Mechanics ; Vol. 84, issue. 5 , May , 2014 , p. 657-669 ; 09391533 ; Hosseini Kordkheili, S. A ; Toozandehjani, H ; Sharif University of Technology
Abstract
Both numerical and experimental researches are carried out to study the strength of the composite double-bolted joints and the bearing damage propagation. A mesoscale level progressive damage model along with analytical formulation is used to predict the bearing failure of carbon-epoxy composite plates. This damage model is introduced as a user material subroutine in the commercial software ABAQUS, and the maximum failure load is calculated. In order to validate the numerical results, experimental tests are also conducted in which comparison between the results shows an excellent agreement. Furthermore, the effects of the bolt distances on the maximum failure load are studied. The results...
Analytical modeling of a Minimally Invasive Surgery grasper actuated by shape memory alloy wires
, Article International Conference on Robotics and Mechatronics, ICRoM 2013 ; Feb , 2013 , Pages 147-151 ; 9781467358118 (ISBN) ; Zabihollah, A ; Sharif University of Technology
2013
Abstract
Minimally Invasive Surgery (MIS) is getting common these days. MIS robots using special tools can perform surgery precisely as humans. This is only possible with dexterous end-effectors and a well-controlled system. Local, lightweight and powerful actuators positioned at end-effectors provide the ability to decrease the degrees of freedom and simplify the design. This paper discusses a grasper design actuated by Shape Memory Alloy (SMA) wires that can be used in MIS robotics. The properties of a commercially available shape memory alloy are explored and analytical formulations for the actuation procedure are developed. The grasper actuated by SMA wires is studied and the procedure of...
An analytical formulation enabling analysis of resonance eigenmodes and their interferences in scattering from plasmonic nanostructures, applications in engineering the radiation loss
, Article IEEE Journal of Quantum Electronics ; Volume PP, Issue 99 , 2016 ; 00189197 (ISSN) ; Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
An analytic formulation revealing exact contribution of different factors affecting the interference interaction between eigenmodes of a scatterer is presented by utilizing our previously reported modal scattering power formula. For special case of arbitrary multilayer concentric and nonconcentric nanoshells, a recursive method for analytically calculating the T-matrix, and each of these factors is derived. Results for a three layer structure showing the conditions for constructive and destructive interference interactions are discussed in details. It is shown that the interference interaction can occur in the vicinity of the overlapping resonance frequencies of the two spatially overlapping...
Employing coupled cavities to increase the cooling rate of a levitated nanosphere in the resolved sideband regime
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 35, Issue 7 , 2018 , Pages 1563-1569 ; 07403224 (ISSN) ; Mehrany, K ; Sharif University of Technology
OSA - The Optical Society
2018
Abstract
In this paper, we investigate cooling of a levitated nanosphere in a system of coupled cavities in the resolved sideband regime. Thanks to the presence of an extra resonance in the coupled cavity cooling system, the coupling strength can be maximized at the optimum detuning. In this fashion, the intracavity photon number is increased, and thereby the cooling rate is enhanced and the strong coupling regime is achieved without resorting to increased driving laser power. The underlying physics of the increased cooling efficiency in the system of coupled cavities in the resolved sideband regime proposed here and that of the already reported system of coupled cavities in the unresolved sideband...
On the contact mechanics of a rolling cylinder on a graded coating. Part 1: Analytical formulation
, Article Mechanics of Materials ; Vol. 68, issue , 2014 , p. 207-216 ; Guler, M. A ; Adibnazari, S ; Sharif University of Technology
Abstract
In this paper, the fully coupled rolling contact problem of a graded coating/substrate system under the action of a rigid cylinder is investigated. Using the singular integral equation approach, the governing equations of the rolling contact problem are constructed for all possible stick/slip regimes. Applying the Gauss-Chebyshev numerical integration method, the governing equations are converted to systems of algebraic equations. A new numerical algorithm is proposed to solve these systems of equations. Both the coupled and the uncoupled solutions to the problem are found through an implemented iterative procedure. In Part I of this paper, the analytical formulation of the rolling contact...
Steady-state creep analysis of polymer matrix composites using complex variable method
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 227, Issue 10 , 2013 , Pages 2182-2194 ; 09544062 (ISSN) ; Mondali, M ; Abedian, A ; Sharif University of Technology
2013
Abstract
A new analytical formulation is presented to study the steady-state creep in short fiber composites using complex variable method. In this new approach, both the fiber and matrix creep at low stresses and temperatures. To analyze the crept fiber, a plane stress model was used. Important novelties of the present analytical method are determination of displacement rates with proper boundary conditions in the crept fibers and also using the complex variable method in creep analyzing. It is noteworthy that the method can be useful to study the creep behavior in polymeric matrix composites due to their high capability of creep. Moreover, another significant application of the present method is to...
On the contact mechanics of a rolling cylinder on a graded coating. Part 2: Numerical results
, Article Mechanics of Materials ; Volume 66 , 2013 , Pages 134-159 ; 01676636 (ISSN) ; Alinia, Y ; Adibnazari, S ; Sharif University of Technology
2013
Abstract
The analytical formulation of the fully coupled and the uncoupled rolling contact mechanics problems for all possible stick/slip regimes are derived in Part I (Alinia et al., 2013). In this part, we focus on the numerical algorithm, the iteration procedure and the numerical results. The coupled and the uncoupled solutions corresponding to each of the assumed stick/slip regimes are provided. The uncoupled solution provides an acceptable approximation to the problem for small coefficient of friction values. However, for high values of the coefficient of friction the problem should be solved in fully coupled form. In addition, the effect of several parameters such as the stiffness ratio, the...
An enhanced continuum modeling of the ideal strength and the angle of twist in tensile behavior of single-walled carbon nanotubes
, Article Journal of Applied Physics ; Volume 114, Issue 5 , 2013 ; 00218979 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2013
Abstract
By utilizing the fourth-, sixth-, eighth-, and tenth-order elastic moduli tensors of graphene a highly nonlinear constitutive model for it is proposed. Subsequently, an accurate analytical formulation, describing the entire tensile behavior of single-walled carbon nanotubes (SWCNTs) from their initial unloaded states through their ideal strengths, is made possible. The angle of twist which is a critical parameter that varies with the tensile loading is also calculated within the current framework. The estimated value of the theoretical strength of SWCNTs with different chiralities and radii as well as that of graphene ranges from 0.39 to 0.44 TPa. Some peculiarities associated with chirality...
Generating uniform irradiance in the Fresnel region by quasi-optical beam shaping of a millimeter-wave source
, Article Optics Express ; Volume 27, Issue 22 , 2019 , Pages 32135-32146 ; 10944087 (ISSN) ; Ahmadi-Boroujeni, M ; Tehranian, A ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
In this paper, we report on the design, simulation and measurement of a flat-top beam shaper (FBS) lens for a millimeter-wave (mm-wave) antenna coupled source. The beam shaper is designed to transform the pseudo-Gaussian beam of the mm-wave source into a flat-top beam of sharp roll-off at a specific distance in the Fresnel region. Firstly, relying on the geometrical optics principles, we propose an analytical formulation for the design of lens profiles. Next, a simple optimization method based on the full-wave simulation of the lens and the mm-wave antenna is suggested to tune the analytically extracted lens profile. The optimized lens profile is then studied to assess its performance...
Generating uniform irradiance in the fresnel region by quasi-optical beam shaping of a millimeter-wave source
, Article Optics Express ; Volume 27, Issue 22 , 2019 , Pages 32135-32146 ; 10944087 (ISSN) ; Ahmadi Boroujeni, M ; Tehranian, A ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
In this paper, we report on the design, simulation and measurement of a flat-top beam shaper (FBS) lens for a millimeter-wave (mm-wave) antenna coupled source. The beam shaper is designed to transform the pseudo-Gaussian beam of the mm-wave source into a flat-top beam of sharp roll-off at a specific distance in the Fresnel region. Firstly, relying on the geometrical optics principles, we propose an analytical formulation for the design of lens profiles. Next, a simple optimization method based on the full-wave simulation of the lens and the mm-wave antenna is suggested to tune the analytically extracted lens profile. The optimized lens profile is then studied to assess its performance...
Corrected formulation for estimation of ripple in large aspect ratio tokamaks
, Article Journal of Fusion Energy ; Volume 31, Issue 2 , 2012 , Pages 195-197 ; 01640313 (ISSN) ; Khorasani, S ; Sharif University of Technology
Abstract
The finite number of toroidal field coils of a tokamak destroys the perfect axisymmetry of the device. The coils produce a short wavelength ripple in the toroidal magnetic field strength as a field line follows round the torus, which becomes important in transport and confinement properties of plasma. Hence, a quick and accurate estimation of ripple becomes important. We have noticed that a previously reported analytical formulation by Princeton Plasma Physics Laboratory team is not applicable to our large aspect ratio tokamak, and have devised a slightly modified form which has greatly improved the accuracy of the analytical fit
A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces
, Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2012
Abstract
Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...
Performance optimization based on analytical modeling in a real-time system with constrained time/utility functions
, Article IEEE Transactions on Computers ; Volume 60, Issue 8 , Aug , 2011 , Pages 1169-1181 ; 00189340 (ISSN) ; Movaghar, A ; Sharif University of Technology
2011
Abstract
We consider a single-processor firm real-time (FRT) system with exponential interarrival and execution times for jobs with relative deadlines following a general distribution. The scheduling policy of the system is first-come first-served (FCFS) and the capacity of the system is arbitrary. This system is subject to an arbitrary-shaped time/utility function (TUF), which determines the accrued utility of each job according to its completion time. It is considered that the system power consumption at different working states is predetermined for each processor speed. We have proposed an exact analytical method for the calculation of specific performance and power-related measures of the system....
An exact analysis for the hoop elasticity and pressure-induced twist of CNT-nanovessels and CNT-nanopipes
, Article Mechanics of Materials ; Volume 82 , 2015 , Pages 47-62A ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier
2015
Abstract
Carbon nanotubes (CNTs) with and without end caps may be used for fluid storage and transport, respectively, referred to as CNT-nanovessel and CNT-nanopipe. The determination of the stiffness in the hoop (circumferential) and radial directions, ideal hoop strength, and hoop stress-strain curve of such nanostructures is of particular interest. Due to the proposed viewpoint, a chiral free-standing single-walled CNT (SWCNT) has a natural angle of twist and natural extension along the axis of the tube. For example, for the SWCNT (9,3) with diameter of 0.85 nm and chirality angle of 13.9°, the natural angle of twist per unit length is 1.45×10-3 rad/nm. Previously, only Vercosa et al. (2010) who...
Formulation of differential transfer matrix method in cylindrical geometry
, Article Proceedings of SPIE - The International Society for Optical Engineering, 25 January 2010 through 28 January 2010 ; Volume 7597 , January , 2010 ; 0277786X (ISSN) ; 9780819479938 (ISBN) ; Khorasani, S ; Rashidian, B ; Mohammadi, S ; Sharif University of Technology
2010
Abstract
Transfer and scattering matrix methods are widely in use for description of the propagation of waves in multilayered media. When the profile of refractive index is continuous, however, a modified formulation of transfer matrices does exist, which provides a complete analytical solution of the wave phenomena in such structures. Previously reported variations of the so-called Differential Transfer Matrix Method (DTMM) had been limited to Cartesian geometry where layered media form one-dimensional structures and plane waves are used as basis functions. In this work, we extend the formalism to cylindrical geometry with radial symmetry, in which Bessel functions need to be employed as basis...
Calculation of the additional constants for fcc materials in second strain gradient elasticity: Behavior of a nano-size bernoulli-euler beam with surface effects
, Article Journal of Applied Mechanics, Transactions ASME ; Volume 79, Issue 2 , 2012 ; 00218936 (ISSN) ; Ahmadpoor, F ; Tehranchi, A ; Sharif University of Technology
2012
Abstract
In addition to enhancement of the results near the point of application of a concentrated load in the vicinity of nano-size defects, capturing surface effects in small structures, in the framework of second strain gradient elasticity is of particular interest. In this framework, sixteen additional material constants are revealed, incorporating the role of atomic structures of the elastic solid. In this work, the analytical formulations of these constants corresponding to fee metals are given in terms of the parameters of Sutton-Chen interatomic potential function. The constants for ten fcc metals are computed and tabulized. Moreover, the exact closed-form solution of the bending of a...
Performance evaluation of asynchronous multi-carrier code division multiple access for next-generation long-reach fibre optic access networks
, Article IET Optoelectronics ; Volume 9, Issue 6 , 2015 , Pages 325-332 ; 17518768 (ISSN) ; Beyranvand, H ; Salehi, J. A ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this study, the authors evaluate the performance of asynchronous optical multi-carrier code division multiple access (MC-CDMA) for intensity modulated/direct detection systems to be used in next-generation optical access networks. The proposed system employs Gold sequence in frequency-domain to provide asynchronous resource sharing. In long-reach passive optical networks, fibre impairments degradation to the performance of ordinary optical CDMA can be avoided by frequency-domain digital compensation methods in the proposed MC-CDMA. In comparison with orthogonal frequency division multiple access, peak-to-average power ratio in the proposed MC-CDMA is reduced and asynchronous resource...