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Approximate minimum diameter
, Article 23rd International Conference on Computing and Combinatorics, COCOON 2017, 3 August 2017 through 5 August 2017 ; Volume 10392 LNCS , 2017 , Pages 237-249 ; 03029743 (ISSN); 9783319623887 (ISBN) ; Homapour, H ; Seddighin, M ; Sharif University of Technology
Springer Verlag
2017
Abstract
We study the minimum diameter problem for a set of inexact points. By inexact, we mean that the precise location of the points is not known. Instead, the location of each point is restricted to a continuous region ({Imprecise} model) or a finite set of points ({Indecisive} model). Given a set of inexact points in one of {Imprecise} or {Indecisive} models, we wish to provide a lower-bound on the diameter of the real points. In the first part of the paper, we focus on {Indecisive} model. We present an (formula presented) time approximation algorithm of factor (1+epsilon) for finding minimum diameter of a set of points in d dimensions. This improves the previously proposed algorithms for this...
A holistic survey on mechatronic Systems in Micro/Nano scale with challenges and applications
, Article Journal of Micro-Bio Robotics ; 2021 ; 21946418 (ISSN) ; Jalili, N ; Ahmadian, M. T ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Micro/Nano mechatronic systems might be defined as systems that include nano- or micro-scale components. These components can be sensors, actuators, and/or physical structures. Furthermore, the high-precision control laws for such small scales are important to ensure stability, accuracy, and precision in these systems. In this writing, four categories of such small-scale systems are considered by providing multifarious novel or key examples from the literature: control engineering and modeling, design and fabrication, measurement engineering, and sensor/actuator development. The applications discussed in the examples vary from nano-positioners, crucial in systems such as atomic force...
Utilizing the moiré deflectometry-based detection method improves the detection sensitivity for gold nanoparticles trapped by optical tweezers
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 38, Issue 7 , 2021 , Pages 2135-2140 ; 07403224 (ISSN) ; Khorshad, A. A ; Sharif University of Technology
The Optical Society
2021
Abstract
Gold nanoparticles (GNPs) are very often used as handles for nanotechnological micromanipulation. In this regard, optical trapping of GNPs is of great importance, in which locating the trapped GNP within the focal spot with nanometer precision is crucial. Very recently, we have introduced a new position detection system for optical tweezers based on moiré deflectometry (MD). Here we show, both theoretically and experimentally, that an MD detection system could provide significantly larger detection sensitivity for a trapped GNP compared to that provided by conventional back focal plane (BFP) detection systems. For instance, for a trapped 200 nm GNP, the detection sensitivity provided by the...
A low voltage, high speed current mode sample and hold for high precision applications
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 1 , 2005 , Pages 269-272 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Bakhtiar, M. S ; Sharif University of Technology
2005
Abstract
This paper presents a zero-voltage switching current mode sample and hold(S/H) circuit. The proposed S/H has 12 bit linearity at 180MHz sampling rate for 1.5v supply voltage. The S/H circuit is designed for 0.18μm CMOS technology
Continuous quantum clock with high precision and long recurrence time
, Article Physical Review A ; Volume 106, Issue 2 , 2022 ; 24699926 (ISSN) ; Nikaeen, M ; Bahrampour, A ; Sharif University of Technology
American Physical Society
2022
Abstract
Continuous clocks, i.e., clocks that measure time in a continuous manner, are regarded as an essential component of sensing technology. Precision and recurrence time are two basic features of continuous clocks. In this paper, in the framework of quantum estimation theory various models for continuous quantum clocks are proposed, and all tools of quantum estimation theory are employed to seek the characteristics of clocks with high precision and long recurrence time. Then, in a resource-based approach, the performances of the proposed models are compared. It is shown that quantum clocks based on an n two-qubit system not only can have better precision than quantum clocks based on a 2n...
Analysis and Evaluation of Security Vulnerabilities of Precision time Protocol (PTP) and Securing IEEE61850 based Digital Substations
, Ph.D. Dissertation Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Nowadays, power systems and substations are the most important components of the vital infrastructure of a country, which handle the production, transmission and distribution of the electrical energy. Automation systems increase the efficiency of the power industry while making remote control possible, but the use of computer-based control systems is a potential field for cyberattacks which may cause equipment destruction and electricity network destabilization. One of the main requirements for the utilization of digital substations is the synchronization between different equipment used in it. Several algorithms and protocols have been proposed so far for time synchronization in distributed...
Precise position control of shape memory alloy actuator using inverse hysteresis model and model reference adaptive control system
, Article Mechatronics ; Volume 23, Issue 8 , December , 2013 , Pages 1150-1162 ; 09574158 (ISSN) ; Sayyaadi, H ; Sharif University of Technology
2013
Abstract
Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input-output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward-feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized...
Spindle speed variation for regenerative chatter suppression in turning process with tool wear effect
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 4 , 2010 , Pages 619-626 ; 9780791849187 (ISBN) ; Vossoughi, G ; Rahaeifard, M ; Movahhedy, M ; ASME Turkey Section ; Sharif University of Technology
Abstract
Chatter suppression in machining processes results in more material removal rate, high precision and surface quality. In this paper, a single degree of freedom model of orthogonal turning process is used to set up the delay differential equation of motion with considering the tool wear effect as a contact force between the workpiece and tool flank surfaces. Sinusoidal spindle speed variations with different frequencies around the mean speed are modulated to disturb the regenerative mechanism. The optimal amplitudes of the speed modulations are found based on a genetic algorithm such that the input energy to the turning process is minimized. Results of the stability analysis and the...
Precise assembly of metallic nanoclusters as building blocks of nanostructures: A molecular dynamics study
, Article Proceedings of the ASME Design Engineering Technical Conference, 15 August 2010 through 18 August 2010 ; Volume 4 , 2010 , Pages 819-826 ; 9780791844120 (ISBN) ; Meghdari, A ; Jalili, N ; Amiri, F ; Design Engineering Division and Computers in Engineering Division ; Sharif University of Technology
Abstract
Molecular dynamics simulations are used to study the assembly of metallic nanoclusters using manipulation process. These particles are assumed as potential building blocks for bottom-up manufacturing of nanoscale structures. One of the key factors in the assembly of nanoclusters is their precise positioning by a manipulation system. Prediction of the corresponding behavior under the influence of working conditions is of crucial importance for planning of controlled positioning and assembly of nanoclusters. The focus of the present research is on ultra-fine metallic nanoclusters. The effects of material type and manipulation strategy on the success of the process are investigated by molecular...
Investigation of critical influential speed for moving mass problems on beams
, Article Applied Mathematical Modelling ; Volume 33, Issue 10 , 2009 , Pages 3885-3895 ; 0307904X (ISSN) ; Mofid, M ; Vafai, A ; Sharif University of Technology
2009
Abstract
A traveling mass due to its mass inertia has significant effects on the dynamic response of the structures. According to recent developments in structural materials and constructional technologies, the structures are likely to be affected by sudden changes of masses and substructure elements, in which the inertia effect of a moving mass is not negligible. The transverse inertia effects have been a topic of interest in bridge dynamics, design of railway tracks, guide way systems and other engineering applications such as modern high-speed precision machinery process. In this study an analytical-numerical method is presented which can be used to determine the dynamic response of beams carrying...
Position control of ionic polymer-metal composites using fuzzy logic
, Article 2008 ASME International Mechanical Engineering Congress and Exposition, IMECE 2008, Boston, MA, 31 October 2008 through 6 November 2008 ; Volume 11 , 2009 , Pages 575-581 ; 9780791848722 (ISBN) ; Honarvar, M ; Alasty, A ; Meghdari, A ; Zohor, H ; Sharif University of Technology
2009
Abstract
The Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers which generate large deformation under a low driving voltage. In this paper an empirical model of IPMC is developed by measuring the step response of a 23 mmx3.6 mmx0.16 mm IPMC strip in a cantilever configuration. Moreover, a model-based precision position control of an IPMC base on the fuzzy logic is presented. Open-loop position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeatability and reliability. A CCD camera was used to observe the closed loop response of the IPMC strip in order to control this...
Investigation and Implementation of Ultra High Speed Algorithms for Frequency Measurement
, M.Sc. Thesis Sharif University of Technology ; Pezeshk, Amirmansour (Supervisor) ; Sanaei, Esmaeel (Supervisor)
Abstract
The purpose of this project is to detect the instantaneous frequency of an unknown signal which has a frequency range from 2GHz to 18GHz, and its amplitude is limited. In the first step, this signal is amplified, and its amplitude is limited and then it is converted to a digital sequence using a mono-bit scheme and entered the FPGA through an ultra-fast serial port. After that, the algorithm of this project is supposed to do two main processing stages on the received stream of pulses. Detection should be performed in the first phase. It means that it should be determined whether the received pulse sequence is a random sequence made by noise or an almost regular sequence due to a sinusoidal...
Precise Cosmology with Redshift Space Distortion and Calculating Pecular Velocity of SNe type Ia
, M.Sc. Thesis Sharif University of Technology ; Baghram, Shant (Supervisor)
Abstract
The distance measurement is the corner stone of the modern cosmology. They are measured via ”Doppler Effect”, accordingly the distances in cosmology are obtained in red-shift space. Despite the cosmological background expansion, the peculiar velocities due to the local density contrast distort these measurements. One of the main challenges in upcoming cosmological studies is to distinguish the peculiar velocity effect from the background expansion.Supernova Type Ia as standard candles can be think of a crucial observation to address the above problem. In this thesis, we study the effect of cosmological perturbations on distance-redshift relation of the SNIa. The corrective effects are from weak...
Soil Moisture Monitoring in Precision Agriculture Using Estimation Theories
, Ph.D. Dissertation Sharif University of Technology ; Nobakhti, Amin (Supervisor)
Abstract
Monitoring of soil moisture plays an essential role in correct decision making and implementation of any closed loop control system in precision agriculture. On the one hand, continuous using of a lot of moisture sensors and monitoring of soil moisture via direct measurement is restricted by practical prohibitions. On the grounds that activation of a lot of sensors continuously requires communication of a large amount of information and causes high power consumption for a moisture monitoring system. On the other hand, using remote sensing methods such as satellite methods, for moisture monitoring in arbitrary spatial and time resolution for control purposes, is not practically possible. The...
Manufacture & Design of a Programmable Micro Syringe for Injecting of Biodegradable Photo Polymers
, M.Sc. Thesis Sharif University of Technology ; Durali, Mohammad (Supervisor) ; Toyserkani, Ehsan (Co-Advisor)
Abstract
The micro-scale channel creation in Osteochondral scaffolds is a prominent issue in tissue engineering. In this project we tried to identify the relevant parameters to obtain the method for injecting a biodegradable photo polymer to achieve a micro channel by predictable size.Due to inadequate accuracy in measuring the properties of the non –Newtonian working fluid, it was decided to use the Newtonian fluid equations in this study. The relevant equations for injecting the liquid under constant pressure were extracted. The modeling and design of micro syringe system was then completed. Using the made set up experiment to measure the fluid viscosity were performed.The next step was the...
Quantum metrology in open systems: Dissipative cramer-rao bound
, Article Physical Review Letters ; Volume 112, Issue 12 , 2014 ; 00319007 (ISSN) ; Mehboudi, M ; Rezakhani, A. T ; Sharif University of Technology
American Physical Society
2014
Abstract
Estimation of parameters is a pivotal task throughout science and technology. The quantum Cramér-Rao bound provides a fundamental limit of precision allowed to be achieved under quantum theory. For closed quantum systems, it has been shown how the estimation precision depends on the underlying dynamics. Here, we propose a general formulation for metrology scenarios in open quantum systems, aiming to relate the precision more directly to properties of the underlying dynamics. This feature may be employed to enhance an estimation precision, e.g., by quantum control techniques. Specifically, we derive a Cramér-Rao bound for a fairly large class of open system dynamics, which is governed by a...
A novel brushless synchro: Operation principle and experimental results
, Article 2013 21st Iranian Conference on Electrical Engineering, ICEE 2013 ; 2013 , 14-16 May ; 9781467356343 (ISBN) ; Ghafarzadeh, M ; Abedini, R ; Aliabad, A. D ; Kamali, E. A ; Sharif University of Technology
2013
Abstract
In synchroes and resolvers, brushes and slip-rings produce a lot of noise in the output signal. Compared to encoders, the application of such position sensors in precision control systems are restricted because of their lower accuracy. In this research, a novel scheme of a brushless synchro is introduced. In this scheme, the secondary windings are mounted on the stator and the stator magnetic flux passes a certain path in the rotor and induces voltage in the secondary windings. The operation principle is clearly described in the paper and by using 2D finite element method the novel synchro is initially designed and analyzed. The stator winding's turns is calculated by a method based on...
Change point estimation of high-yield processes with a linear trend disturbance
, Article International Journal of Advanced Manufacturing Technology ; Volume 69, Issue 1-4 , May , 2013 , Pages 491-497 ; 02683768 (ISSN) ; Khedmati, M ; Sharif University of Technology
2013
Abstract
In this paper, the maximum likelihood estimator (MLE) of the change point in a high-yield process when a linear trend disturbance occurs in the proportion nonconformity of the process is first derived. Then, the performances of the proposed change point estimator in terms of both accuracy and precision are compared to the MLE of the change point designed for step changes. The results of the comparison analysis that is performed using Monte Carlo simulation experiments show that not only the average estimates of the change point estimator designed for linear trends are closer to the real change point, but also its mean square error is smaller than the one of the estimator designed for step...
Out-of-plane buckling of Y-braced frames with rigid joints
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 166, Issue 1 , 2013 , Pages 28-37 ; 09650911 (ISSN) ; Vafai, A ; Kazemi, M.T ; Sharif University of Technology
2013
Abstract
Because of the complicated buckling characteristics of Y-shaped bracings, calculation of their strength is beyond routine engineering procedures. A method based on slope-deflection equations incorporating stability functions has been used for computation of buckling eigenvalues and effective length factors. Lateral strength is computed based on the least buckling strength of bracing members. This study is limited to bracings with similar sections and fixed end connections resisting out-of-plane rotation. Lateral strengths predicted by the analytical method for two cases are compared with experimental results on full-scale specimens. It is shown that the proposed analytical method predicts...
Power system stability assessment during restoration based on a wide area measurement system
, Article IET Generation, Transmission and Distribution ; Volume 6, Issue 11 , 2012 , Pages 1171-1179 ; 17518687 (ISSN) ; Karimi, M. J ; Ranjbar, A. M ; Shirani, A ; Sharif University of Technology
2012
Abstract
Online power system stability assessment during restoration has not been strongly addressed yet. The introduction of wide area measurement systems (WAMS), however, made it possible to monitor the stability online. This study technically presents a detailed analysis of stability during restoration using WAMS. The power system build-up strategy is used as the restoration approach, based on which the early and the last stages of restoration are to divide the power system into islands and interconnect them, respectively. In fact, the practical use of WAMS at the early stages of restoration provides precise determination of generators loading steps. Moreover, unification of phase angle references...