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In the atomic force microscope (AFM) scanning system, the piezoscanner is significant in realizing high-performance tasks. To cater to this demand, a novel compliant two-degrees-of-freedom (2-DOF) micro-/nanopositioning stage with...
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In the atomic force microscope (AFM) scanning system, the piezoscanner is significant in realizing high-performance tasks. To cater to this demand, a novel compliant two-degrees-of-freedom (2-DOF) micro-/nanopositioning stage with modified lever displacement amplifiers is proposed in this paper, which can be selected to work in dual modes. Moreover, the modified double four-bar P (P denotes prismatic) joints are adopted in designing the flexible limbs. The established models for the mechanical performance evaluation in terms of kinetostatics, dynamics, and workspace are validated by finite-element analysis. After a series of dimension optimizations carried out via particle swarm optimization algorithm, a novel active disturbance rejection controller, including the components of nonlinearity tracking differentiator, extended state observer, and nonlinear state error feedback, is designed for automatically estimating and suppressing the plant uncertainties arising from the hysteresis nonlinearity, creep effect, sensor noises, and other unknown disturbances. The closed-loop control results based on simulation and prototype indicate that the two working natural frequencies of the proposed stage are approximated to be 805.19 and 811.31 Hz, the amplification ratio in two axes is about 4.2, and the workspace is around $120 times 120 muhbox{m}^{2}$, while the cross-coupling between the two axes is kept within 2%. All of the results indicate that the developed micro-/nanopositioning system has a good property for high-performance AFM scanning.
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This paper presents a new steel wind- and seismic-resisting wall, called a lever viscoelastic wall (LVEW) that includes a velocity-dependent VE damper and a displacement-dependent friction damper in a device, characterized by two ...
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This paper presents a new steel wind- and seismic-resisting wall, called a lever viscoelastic wall (LVEW) that includes a velocity-dependent VE damper and a displacement-dependent friction damper in a device, characterized by two different motion phases. In Phase one motion (i.e., small drifts), the VE damper which is activated by a lever delivers amplified lateral force and energy dissipation to the frame structure. In Phase two motion (i.e., medium-to-large drifts), the VE damper is constrained by a stopper and the friction damper, instead, is activated to provide frictional energy dissipation to the frame. The damping is provided by incorporating VE material and sliding friction in a wall configuration, reducing both the wind and earthquake responses of structures in a single unit. The objectives of the work were to (1) develop the force transfer mechanism and kinematics of the LVEW, (2) verify the cyclic response of LVEWs at low and large drifts, and (3) evaluate the limitation of LVEWs for the applications. Three full-scale LVEW specimens were designed and tested to validate the hysteretic response in two motion phases. The hysteretic response of LVEWs obtained from the test was compared to that from the analytical formulation.
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It is believed that serum pepsinogen levels could be useful for diagnosis of abomasal changes in cattle. Diagnosis of abomasal displacement (AD) is made via invasive and non-invasive techniques. None of the extant methods is a rel...
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It is believed that serum pepsinogen levels could be useful for diagnosis of abomasal changes in cattle. Diagnosis of abomasal displacement (AD) is made via invasive and non-invasive techniques. None of the extant methods is a reliable indication of mucosal change. The applicability of serum pepsinogen levels for the diagnosis of changes in the mucous membrane of the abomasum in experimentally induced left and right AD in sheep was investigated in fourteen rams. Abomasal fluid samples were taken andthe pH was recorded. Twelve sheep underwent induced left and right AD (six for each group). Two sheep underwent exploratory laparatomy alone to assess the effect of surgical stress on the abomasum. Blood samples were taken before surgery, at the 1st, 3rd, 5th, 7th, 9th and 11th days after surgery and at the time of necropsy and serum pepsinogen levels were measured. After two weeks the animals were slaughtered and abomasal fluid pH and types of abomasal ulcers were recorded. Significant changes in pepsinogen levels in the left displaced abomasums (LDA) group were seen on days 11 and 14 after surgery (P < 0.05). Significant changes in pepsinogen levels in the right displaced abomasum (RDA) group were seen on Days 9, 11 and 14 after surgery (P < 0.05). There was no association among the types of ulcers and the serum pepsinogen levels in AD cases. The pH increased significantly (P < 0.05) after induced AD in both groups. There were no significant changes in serum pepsinogen levels on different days aftersurgery among ulcerated and non ulcerated cases in both LDA and RDA groups (P < 0.05). Serum pepsinogen levels were significantly higher in AD groups. There was no association between the types of ulcers and serum pepsinogen levels in AD cases. It seemsthat the increase in concentration of serum pepsinogen is a good reflection of the damage to the abomasal mucousa due to AD, as was shown by the earlier increase in levels in the course of displacement in the RDA group.
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In this paper, the development of a flexure-based two-degree-of-freedom (2-DOF) nanomanipulator with modified differential lever displacement amplifier is conducted, which aims to break through the millimeter-range barrier. The ki...
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In this paper, the development of a flexure-based two-degree-of-freedom (2-DOF) nanomanipulator with modified differential lever displacement amplifier is conducted, which aims to break through the millimeter-range barrier. The kinetostatics modeling of the mechanism is established by using the pseudorigid body method, also the analytical modeling of lever is built up, as well as the dimension optimizations and the mechanism performance validations are conducted by using the Particle Swarm Optimization algorithm and the finite-element analysis method, respectively. With the consideration of hysteresis effect inherent in piezoelectric ceramics actuators, the hysteresis modeling is conducted by using the Preisach theory. To enhance the mechanism positioning performance, a novel feedforward nonlinear proportion-integration-differentiation control strategy composed by the nonlinear PID controller and the inverted Preisach hysteresis compensator is proposed in this paper. Finally, a series of closed-loop motion tracking experiments have been carried out. It indicates that the developed mechanism has achieved a millimeter workspace (3.1273 mm), nanometer scale motion resolution (40 nm), as well as a closed-loop positioning bandwidth of over 10 Hz.
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In this paper, a mechanical amplification concept for microelectromechanical systems (MEMS) physical sensors is proposed with the aim to improve their sensitivity. The scheme is implemented using a system of micromachined levers (...
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In this paper, a mechanical amplification concept for microelectromechanical systems (MEMS) physical sensors is proposed with the aim to improve their sensitivity. The scheme is implemented using a system of micromachined levers (microlevers) as a deflection amplifying mechanism. The effectiveness of the mechanism is demonstrated for a capacitive accelerometer. A proof-of-concept single-axis mechanically amplified accelerometer with an amplification factor of 40 has been designed, simulated, and fabricated, and results from its evaluation are presented in this paper. The sensor's amplified output has a sensitivity of 2.39 V/g using an open-loop capacitive pick-off circuit based on charge amplifiers. Experimental results show that the addition of the mechanical amplifier does not alter the noise floor of the sensor. The measured natural frequency of the first mode of the sensor is at 734 Hz, and the full-scale measurement range is up to 7 g with a maximum nonlinearity of 2$%$ . It is shown, through comparison with a conventional design, that the mechanically amplified accelerometer provides higher deflection without sacrificing bandwidth.$hfill$ [2011-0231]
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Commercial-off-the-shelf (COTS) capacitor-based isolation amplifiers were irradiated at the Portuguese Research Reactor (PRR) in order to determine its tolerance to the displacement damage and total ionising dose (TID). The set of...
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Commercial-off-the-shelf (COTS) capacitor-based isolation amplifiers were irradiated at the Portuguese Research Reactor (PRR) in order to determine its tolerance to the displacement damage and total ionising dose (TID). The set of experimental data shows that some of these devices are suitable for zones inside future nuclear facilities where the expected total radiation damage would be below 2.2 × 10~(13)1-MeV neutron/cm~2 and 230Gy (Si). However, some drawbacks must be taken into account by the electronic designers such as the increase of the output offset voltage and the slight modification of the transmission gain.
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This paper presents a new analysis method for bridge-type amplifiers by incorporating the effect of external loads, and establishes a theoretical model to predict the input/output displacement amplification ratio based on elastic ...
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This paper presents a new analysis method for bridge-type amplifiers by incorporating the effect of external loads, and establishes a theoretical model to predict the input/output displacement amplification ratio based on elastic beam theory. The new analytical model indicates that the displacement amplification ratio of the bridge-type amplifiers decreases significantly in the presence of external loads, and its changing rate increases with higher external loads. The analysis method is then applied to the modeling and design of a bridge type-amplifier based nano-manipulating stage, where the guiding mechanism acts as the external load of the bridge-type amplifiers. It is shown that the new analysis method can derive more accurate model of the nano-stage, which is further verified by the finite element analysis (FEA) results. The proposed method offers a new look into the analysis and design of flexure based nano-stages for real applications. (c) 2016 Elsevier B.V. All right reserved.
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We developed a conventional magneto-optical (MO) medium for the first surface magneto-optical (FSMO) recording that has a land and groove structure with a track pitch of 0.265 mum and groove depth of about 50 nm. The first surface...
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We developed a conventional magneto-optical (MO) medium for the first surface magneto-optical (FSMO) recording that has a land and groove structure with a track pitch of 0.265 mum and groove depth of about 50 nm. The first surface recording was performed on this medium, using magnetic field modulation and a blue laser optical system equipped with a high-NA objective lens. Disk noise related to reverse stacking of layers was greatly reduced by optimizing the production process for the substrate and the heat sink layers, and a practical level CNR was obtained. Bit error rate measurements were conducted assuming NRZI code and Turbo decording, and a possible power margin of 16.5 Gbit/in~2 areal density was confirmed. This result indicates a possible capacity of 10 GB for a 3.5-inch disk or 25 GB for a 5.25-inch disk.
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The small inductance of an inductive transducer generally linearly changes with a process variable, but their measurement by the usual inductive bridge circuit like the Maxwell bridge, the Maxwell–Wien Bridge, the Hay bridge, etc...
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The small inductance of an inductive transducer generally linearly changes with a process variable, but their measurement by the usual inductive bridge circuit like the Maxwell bridge, the Maxwell–Wien Bridge, the Hay bridge, etc., suffers from errors due to the effect of the stray capacitance between bridge nodal points and the ground and the stray inductance on the inductive coil, respectively. The conventional Wagner–Earth technique is not suitable for continuous measurement. In this paper, a modified operational-amplifier-based Maxwell–Wien bridge measurement technique has been proposed in which the effect of stray capacitance and inductance is minimized. In the first phase of the experiment, the bridge performance has been studied with a known variable inductor, and in the second phase, the same experimentation was done by replacing the variable inductor with an inductive coil having an adjustable core position for the measurement of displacement. The linear characteristics over a wide range of displacement with good repeatability, linearity, and variable sensitivity have been described.
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Background: As a high-performance functional material, stacked piezoelectric actuator can produce a displacement under the effect of changing voltage. Its advantages of fast response and easy operation make it to be widely applied...
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Background: As a high-performance functional material, stacked piezoelectric actuator can produce a displacement under the effect of changing voltage. Its advantages of fast response and easy operation make it to be widely applied in the precision structure field. However, its small displacement stroke and hysteresis nonlinearity affect the accuracy of the output.
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