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Transformation studies of some polar pesticides in water by on-line solid-phase extraction and liquid chromatography/particle beam-mass spectrometry
, Article Analytical Letters ; Volume 33, Issue 2 , 2000 , Pages 249-263 ; 00032719 (ISSN) ; Slobodník, J ; Brinkman, U.A.Th ; Sharif University of Technology
Marcel Dekker Inc
2000
Abstract
An on-line automated method for phototransformation studies of alachlor, aldicarb, and methiocarb by means of liquid chromatography/mass spectrometry (LC/MS) with particle beam (PB) interface is described. Surface water samples were first spiked with 50 μg/l of each pesticide and then exposed to the radiation of a medium-pressure mercury lamp. Next, in regular intervals of 60 min, aliquots of 50-ml sample were enriched on a solid-phase extraction (SPE) cartridge and on-line eluted by a gradient of LC eluent onto analytical column for separation, followed by MS detection. A phototransformation experiment with each pesticide was performed twice, with MS operated in electron ionisation (EI) and...
Analysis and Modeling "Time-of-Flight Particle Sizer" with CFD
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed (Supervisor) ; Sani, Mahdi (Supervisor)
Abstract
In this study different models of an aerodynamic particle sizer and aerodynamic focusing lens were introduced and governing equations for an aerodynamic focusing lens for flow fields and particle motions were discussed. An aerodynamic focusing lens was simulated for analyzing particle motions and flow fields. Two kinds of models are considered; One was Ahmadi`s model and the other one was Wang`s model and both models are axisymmetric. The results show that for small particles (sub 30 nanometers), Brownian motions were highly effective on transmission efficiency and producing particle beams. The two models are compared and the results show that Ahmadi`s model produce narrower particle beams...
Electromechanics of suspended spiral capacitors and inductors
, Article Applied Physics Letters ; Volume 112, Issue 3 , 2018 ; 00036951 (ISSN) ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
Most electromechanical devices are in two-dimensional metallic drums under high tensile stress, which causes increased mechanical frequency and quality factor. However, high mechanical frequencies lead to small zero-point displacements xzp, which limits the single-photon interaction rate g0. For applications which demand large g0, any design with increased xzp is desirable. It is shown that a patterned drum by a spiral shape can resolve this difficulty, which is obtained by a reduction of mechanical frequency while the motion mass is kept almost constant. An order of magnitude increase in g0 and agreement between simulations and interferometric measurements is observed. © 2018 Author(s)
Development, modeling and deflection analysis of hybrid micro actuator with integrated thermal and piezoelectric actuation
, Article Meccanica ; Volume 48, Issue 5 , 2013 , Pages 1081-1091 ; 00256455 (ISSN) ; Zohoor, H ; Kargarnovin, M. H ; Sharif University of Technology
2013
Abstract
Micro actuators are irreplaceable part of motion control in minimized systems. The current study presents an analytical model for a new Hybrid Thermo Piezoelectric micro actuator based on the combination of piezoelectric and thermal actuation mechanisms. The micro actuator structure is a double PZT cantilever beam consisting of two arms with different lengths. The presented micro actuator uses the structure of electrothermal micro actuator in which polysilicon material is replaced by PZT. Also the voltage and poling directions are considered in the lengthwise of PZT beams. As a result, the piezoelectric actuation mechanism is based on d33 strain coefficient. The tip deflection of micro...
Creating and detecting micro-macro photon-number entanglement by amplifying and deamplifying a single-photon entangled state
, Article Physical Review Letters ; Volume 110, Issue 17 , April , 2013 ; 00319007 (ISSN) ; Lvovsky, A ; Simon, C ; Sharif University of Technology
2013
Abstract
We propose a scheme for the observation of micro-macro entanglement in photon number based on amplifying and deamplifying a single-photon entangled state in combination with homodyne quantum state tomography. The created micro-macro entangled state, which exists between the amplification and deamplification steps, is a superposition of two components with mean photon numbers that differ by approximately a factor of three. We show that for reasonable values of photon loss it should be possible to detect micro-macro photon-number entanglement where the macrosystem has a mean number of one hundred photons or more
Vibration of Euler Bernoulli and Timoshenko beams in large overall motion on flying support using finite element method
, Article Scientia Iranica ; Volume 19, Issue 4 , 2012 , Pages 1105-1116 ; 10263098 (ISSN) ; Kakavand, F ; Sharif University of Technology
Elsevier
2012
Abstract
The equations of motion for a beam on a flying support for EulerBernoulli and Timoshenko Beam Theories is derived. In modeling and attempting to have an accurate model at high speeds, a stretch variable instead of conventional axial deformation is used. For a planar rotating beam and a spatial rotating beam, equations of motion are lineralized and verified. Finite element and Newmark direct integration methods are employed for numerical simulations
Generation of motional entangled coherent state in an optomechanical system in the single photon strong coupling regime
, Article Journal of Modern Optics ; Volume 62, Issue 19 , Jul , 2015 , Pages 1685-1691 ; 09500340 (ISSN) ; Shakeri, S ; Hamidi, O ; Zandi, M. H ; Bahrampour, A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
The single-photon strong coupling in the deep-resolved sideband of the optomechanical system induces photon blockade (PB) effect. For the PB cavity, an initial mechanical coherent state evolves into superposition of phonon cat states entangled with the cavity Fock states. Measurement of the cavity photon number states produces phonon even and odd cat states. The information leakage effect of two photon states on the fidelity of cat states is calculated, it is shown that for low average phonon number this effect is negligible and decreases by increasing the two photon cavity state. The Lindblad equation is solved numerically to obtain the environmental effects on the fidelity of cat states
Optomechanical coupling strength in various triangular phoxonic crystal slab cavities
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 35, Issue 6 , 2018 , Pages 1390-1396 ; 07403224 (ISSN) ; Khorasani, S ; Sharif University of Technology
OSA - The Optical Society
2018
Abstract
Enhancement of interaction between optical and mechanical fields is one of the main goals of cavity optomechanics as a newly founded physics context. If the coupling rate between these fields exceeds their decay rates from the cavity, then preparation of quantum entangled states between photons of the electromagnetic field and phonons of the mechanical field becomes feasible. Among different types of cavities, phoxonic crystal (PxC) cavities have attracted attention in recent years because they can confine optical and mechanical fields simultaneously. In this paper, we introduce four PxC slabs which exhibit simultaneous photonic and phononic bandgaps. All of these crystals have a triangular...
Generation of attosecond electron bunches by the relativistic Weibel instability
, Article Physics of Plasmas ; Volume 25, Issue 1 , 2018 ; 1070664X (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
The relativistic Weibel instability and temperature anisotropy can generate electron bunches of attosecond duration which makes it an attractive method for the generation and amplification of tunable ultrashort pulses. In this paper, the effect of the relativistic Weibel instability and temperature anisotropy on generating attosecond electron bunches is investigated. Calculations show that with the reduction relativistic parameter, γ, by a factor of 2, increasing 14.6% of the relativistic Weibel instability leads to about 62% reduction of the nanobunching gain saturation time and the density perturbation generated by the temperature anisotropy and the relativistic Weibel instability. The...
Two-axis dielectric laser acceleration using two orthogonal laser pulses in a dual-grating base structure
, Article Applied Optics ; Volume 59, Issue 7 , 2020 , Pages 2135-2140 ; Madanipour, K ; Bahrampour, A ; Sharif University of Technology
OSA - The Optical Society
2020
Abstract
In this paper, two-axis dielectric laser acceleration is proposed by introducing a dual-grating base laser accelerator structure excited with two orthogonal propagating ultrashort laser pulses. A 2D periodic structure is designed that provides phase synchronicity between the relativistic particle beam and orthogonal propagating laser pulses. In this way, the particle beam can gain energy from both laser pulses simultaneously. It is numerically demonstrated that utilizing this method increases both the acceleration gradient and acceleration factor up to90%in comparison with dual-grating dielectric laser acceleration. Also, deflecting force elimination, particle beam quality, and bunch...
Tip tracking control of a micro-cantilever Timoshenko beam via piezoelectric actuator
, Article JVC/Journal of Vibration and Control ; Vol. 19, issue. 10 , 2013 , pp. 1561-1574 ; ISSN: 10775463 ; Salarieh, H ; Alasty, A ; Shabani, R ; Sharif University of Technology
Abstract
In this paper, the tip tracking control problem of a Timoshenko micro-cantilever beam is investigated. The beam is actuated by a piezoelectric layer laminated on one side of the beam. Dynamic equations of the beam and piezoelectric layer are found using the Hamilton principle. By employing the Galerkin projection method, state space representation of the system is derived. Then, a cascade control loop is used for tracking control of the beam's tip. The cascade control structure consists of an inner loop stabilizer and an outer loop proportional-integral-derivative controller. The stabilizer has a linear feedback form whose states are obtained through a linear observer which is based on the...
Continuous model for flexural vibration analysis of Timoshenko beams with a vertical edge crack
, Article Archive of Applied Mechanics ; 2014 ; ISSN: 09391533 ; Ebrahimi, A ; Behzad, M ; Sharif University of Technology
Abstract
In this paper, a continuous model for flexural vibration of beams with a vertical edge crack including the effects of shear deformation and rotary inertia is presented. The crack is assumed to be an open-edge crack perpendicular to the neutral plane. A quasi-linear displacement filed is suggested for the beam, and the strain and stress fields are calculated. The governing equation of motion for the beam has been obtained using Hamilton principle. The equation of motion is solved with a modified weighted residual method, and the natural frequencies and mode shapes are obtained. The results are compared to the results of similar model with Euler–Bernoulli assumptions and finite element model...
A timoshenko beam element based on the modified couple stress theory
, Article International Journal of Mechanical Sciences ; Vol. 79, issue , 2014 , pp. 75-83 ; ISSN: 00207403 ; Asghari, M ; Ahmadian, M. T ; Sharif University of Technology
Abstract
Since the classical continuum theory is neither able to evaluate the accurate stiffness nor able to justify the size-dependency of micro-scale structures, the non-classical continuum theories such as the modified couple stress theory have been developed. In this paper, a new comprehensive Timoshenko beam element has been developed on the basis of the modified couple stress theory. The shape functions of the new element are derived by solving the governing equations of modified couple stress Timoshenko beams. Subsequently, the mass and stiffness matrices are developed using energy approach and Hamilton's principle. The formulations of the modified couple stress Euler-Bernoulli beam element...
Dynamic green function for response of timoshenko beam with arbitrary boundary conditions
, Article Mechanics Based Design of Structures and Machines ; Volume 42, Issue 1 , 2 January , 2014 , Pages 97-110 ; ISSN: 15397734 ; Mofid, M ; Sharif University of Technology
Abstract
This paper presents the dynamic response of uniform Timoshenko beams with arbitrary boundary conditions using Dynamic Green Function. An exact and direct modeling technique is stated to model beam structures with arbitrary boundary conditions subjected to the external load that is an arbitrary function of time t and coordinate x and the concentrated moving load. This technique is based on the Dynamic Green Function. The effect of different boundary conditions, load, and other parameters is assessed. Finally, some numerical examples are shown to illustrate the efficiency and simplicity of the new formulation based on the Dynamic Green Function
Nonlinear dynamic analysis of a timoshenko beam resting on a viscoelastic foundation and traveled by a moving mass
, Article Shock and Vibration ; Vol. 2014 , 2014 ; ISSN: 10709622 ; Kargarnovin, M. H ; Sharif University of Technology
Abstract
The dynamic response of a Timoshenko beam with immovable ends resting on a nonlinear viscoelastic foundation and subjected to motion of a traveling mass moving with a constant velocity is studied. Primarily, the beam's nonlinear governing coupled PDEs of motion for the lateral and longitudinal displacements as well as the beam's cross-sectional rotation are derived using Hamilton's principle. On deriving these nonlinear coupled PDEs the stretching effect of the beam's neutral axis due to the beam's fixed end conditions in conjunction with the von-Karman strain-displacement relations is considered. To obtain the dynamic responses of the beam under the act of a moving mass, derived nonlinear...
Tip tracking control of a micro-cantilever Timoshenko beam via piezoelectric actuator
, Article JVC/Journal of Vibration and Control ; Volume 19, Issue 10 , 2013 , Pages 1561-1574 ; 10775463 (ISSN) ; Salarieh, H ; Alasty, A ; Shabani, R ; Sharif University of Technology
2013
Abstract
In this paper, the tip tracking control problem of a Timoshenko micro-cantilever beam is investigated. The beam is actuated by a piezoelectric layer laminated on one side of the beam. Dynamic equations of the beam and piezoelectric layer are found using the Hamilton principle. By employing the Galerkin projection method, state space representation of the system is derived. Then, a cascade control loop is used for tracking control of the beam's tip. The cascade control structure consists of an inner loop stabilizer and an outer loop proportional-integral-derivative controller. The stabilizer has a linear feedback form whose states are obtained through a linear observer which is based on the...
Vibration analysis of delaminated Timoshenko beams under the motion of a constant amplitude point force traveling with uniform velocity
, Article International Journal of Mechanical Sciences ; Volume 70 , 2013 , Pages 39-49 ; 00207403 (ISSN) ; Jafari Talookolaei, R. A ; Ahmadian, M. T ; Sharif University of Technology
2013
Abstract
A composite beam with single delamination traveled by a constant amplitude moving force is modeled accounting for the Poisson's effect, shear deformation and rotary inertia. The mechanical behavior between the delaminated surfaces is modeled using a piecewise-linear spring foundation. The governing differential equations of motion for such system are derived. Primarily, eigen-solution technique is used to obtain the natural frequencies and their corresponding mode shapes of such beam. Then, the Ritz method is employed to derive the dynamic response of the beam due to the moving force. The obtained results for the free and forced vibrations of beams are verified against reported similar...
Mechanical behavior analysis of micro-scaled functionally graded timoshenko beams by the strain gradient theory
, Article Proceedings of the ASME Design Engineering Technical Conference ; Volume 5 , 2012 , Pages 67-73 ; 9780791845042 (ISBN) ; Kahrobaiyan, M. H ; Rahaeifard, M ; Ahmadian, M. T ; Movahhedy, M. R ; Akbari, J ; Sharif University of Technology
2012
Abstract
In this paper, a size-dependent formulation is developed for Timoshenko beams made of functionally graded materials (FGM). The developed formulation is based on the strain gradient theory;a non-classical continuum theory able to capture the size-effect in micro-scaled structures. Considering the material length scale parameters of the FG beams vary through the thickness, the new equivalent length scale parameters are proposed as functions of the constituents' length scale parameters to describe the size-dependent static and dynamic behavior of FG microbeams. The governing differential equations of equilibrium and both classical and nonclassical sets of boundary conditions are derived for the...
Forced vibration of delaminated Timoshenko beams subjected to a moving load
, Article Science and Engineering of Composite Materials ; Volume 19, Issue 2 , June , 2012 , Pages 145-157 ; 0334181X (ISSN) ; Ahmadian, M. T ; Jafari-Talookolaeia, R. A ; Sharif University of Technology
Abstract
A composite beam with single delamination under the action of moving load has been modeled accounting for the Poisson's effect, shear deformation, and rotary inertia. The existence of the delamination changes the stiffness of the structure, and this affects the dynamic response of the structure. We have used a constrained mode to simulate the behavior between the delaminated surfaces. Based on this mode, eigensolution technique is used to obtain the natural frequencies and their corresponding mode shapes for the delaminated beam. Then, the Ritz method is adopted to derive the dynamic response of the beam subjected to a moving load. The obtained results for the free and forced vibrations of...
An investigation on effects of traveling mass with variable velocity on nonlinear dynamic response of an inclined Timoshenko beam with different boundary conditions
, Article International Journal of Mechanical Sciences ; Volume 52, Issue 12 , 2010 , Pages 1694-1708 ; 00207403 (ISSN) ; Kargarnovin, M. H ; Farsi, S ; Sharif University of Technology
2010
Abstract
In this paper, the nonlinear dynamic response of an inclined Timoshenko beam with different boundary conditions subjected to a traveling mass with variable velocity is investigated. The nonlinear coupled partial differential equations of motion for the bending rotation of cross-section, longitudinal and transverse displacements are derived using Hamilton's principle. These nonlinear coupled PDEs are solved by applying Galerkin's method to obtain dynamic response of the beam under the act of a moving mass. The appropriate parametric studies by taking into account the effects of the magnitude of the traveling mass, the velocity of the traveling mass with a constant acceleration/ deceleration...