1,720,978 research outputs found
Sensorless control for hysteresis compensation of AFM scanner by modified Rayleigh model
No full textA novel modified Rayleigh model was developed for compensating hysteresis problem of an atomic force microscope (AFM) scanner. In high driving fields, piezoelectric actuators that integrated a scanner have severe hysteresis, which can cause serious displacement errors. Piezoelectric hysteresis is from various origins including movement of defects, grain boundary effects, and displacement of interfaces. Furthermore, because its characteristic is stochastic, it is almost impossible to predict the piezoelectric hysteresis analytically. Therefore, it was predicted phenomenologically, which means that the relationship between inputs and outputs is formulated. The typical phenomenological approach is the Rayleigh model. However, the model has the discrepancy with experiment result as the fields increase. To overcome the demerit of the Rayleigh model, a modified Rayleigh model was proposed. In the modified Rayleigh model, each coefficient should be defined differently according to the field direction due to the increase of the asymmetry in the high fields. By applying an inverse form of this modified Rayleigh model to an AFM scanner, it is proved that hysteresis can be compensated to a position error of less than 5%. This model has the merits of reducing complicated fitting procedures and saving computation time compared with the Preisach model.X1178sciescopu
Constitutive relations for piezoelectric benders under various boundary conditions
No full textIn this article, the constitutive relations of three types of piezoelectric bender-the unimorph bender, bimorph bender and triple-layer bender-are derived based on beam theory under the quasi-static equilibrium condition. The relation coefficients are expressed in terms of the geometrical and material properties of the benders. Constitutive relations are derived for a range boundary conditions (fixed-free, fixed-roll and fixed-simply supported) under conditions allowing different lengths of the piezoelectric and elastic layers. The complicated constitutive relations can be easily formulated and verified by using the function for handling symbolic calculations. The derived constitutive relations may assist in the determination of the optimal values of geometrical parameters in the design of actuators and sensors for particular applications. (C) 2004 Elsevier B.V. All rights reserved.X112120sciescopu
Development of XY scanner with minimized coupling motions for high-speed atomic force microscope
No full textThe design and fabrication processes of a novel scanner with minimized coupling motions for a high-speed atomic force microscope (AFM) were addressed. An appropriate design modification was proposed through the analyses of the dynamic characteristics of existing linear motion stages using a dynamic analysis program, Recurdyn. Because the scanning speed of each direction may differ, the linear motion stage for a high-speed scanner was designed to have different resonance frequencies for the modes, with one dominant displacement in the desired directions. This objective was achieved by using one-direction flexure mechanisms for each direction and mounting one stage for fast motion on the other stage for slow motion. This unsymmetrical configuration separated the frequencies of two vibration modes with one dominant displacement in each desired direction, and hence suppressed the coupling between motions in two directions. A pair of actuators was used for each axis to decrease the crosstalk between the two motions and give a sufficient force to actuate the slow motion stage, which carried the fast motion stage. A lossy material, such as grease, was inserted into the flexure hinge to suppress vibration problems that occurred when using an input triangular waveform. With these design modifications and the vibration suppression method, a novel scanner with a scanning speed greater than 20 Hz is achieved.X113sciescopu
Detection mechanism of spontaneous polarization in ferroelectric thin films using electrostatic force microscopy
No full textMechanism on the detection of spontaneous polarization in a Pb(Zr0.5Ti0.5)O-3 (PZT) film using contact mode of electrostatic force microscopy (EFM) is investigated. Theoretical calculations are performed on deflections induced by electrostatic force (u(omega)(e)) between the tip and the sample and electromechanical vibrations (u(omega)(p)) of the ferroelectric materials, respectively. From the calculation, u(omega)(e) and u(omega)(p) are 3.73 x 10(-9) and 1.77 x 10(-13) m; Enhanced mode of EFM shows the complete cancellation of the EFM image induced by the electrostatic force between the tip and the film through controlling de voltage. Hence, electrostatic force effect is a main contributor on the detection mechanism of spontaneous polarization using EFM in contact mode.X1115sciescopu
Fast solving technique for mechanical dynamic characteristic in electromagnetic motional system by electro-mechanical state equation including extracted circuit parameter
No full textThis paper presents a method of the fast solving technique for electro-mechanical motional systems. Various numerical analysis methods such as finite element method (FEM), boundary element method (BEM) and others employ time-stepping method to analyze the dynamic characteristics of electromechanical systems. Since the system matrix must be solved at each incremental time, this time-stepping method proves to be time-consuming. To solve these problems, this paper presents a fast solving technique by using the extracted circuit parameters and electro-mechanical coupled state equations. To show validity and usefulness of proposed method, two electromagnetic motional systems were tested, and the time-stepping method using FEM was compared with the proposed method.X116sciescopu
An application of polarized domains in ferroelectric thin films using scanning probe microscope
No full textThe feasibility of utilizing PZT films as future data storage media was investigated using a modified AFM. Applying voltages between a conductive AFM tip and the PZT films causes the switching of ferroelectric domains. The domains are observed using an EFM imaging technique. The experimental results and calculations revealed that the electrostatic force generated between the polarized area and the tip is a main contributor for the imaging of the polarized domains. The written features on ferroelectric films were less than 100 nm in diameter, implying the possibility of realizing data storage devices with ultra-high area density. The disappearance of the polarized images without any applied voltage was observed, which is a drawback in this application of PZT thin films.X1120sciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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