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  • Articles  (3,087)
  • 2010-2014  (3,087)
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  • Applied Physics A  (1,984)
  • IEEE/ASME Transactions on Mechatronics  (652)
  • Modelling and Simulation in Engineering  (237)
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  • Technology  (3,087)
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  • Articles  (3,087)
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  • 101
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    Development of Mechanostimulated Patch-Clamp System for Cellular Physiological Study (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-04-30
    Description: Mechanosensitive ion channels play important roles for sensing and responding to the mechanical stimuli signals in living life. Here we report the development of a mechanostimulated patch-clamp system for simultaneous recording of external stimuli and acquisition of cellular physiological responses. This system integrates a custom-designed planar patch-clamp system with a robot-assisted atomic force microscope (AFM) system. The former, with a microfluidic channel, can realize not only recording electrical signals but also exchanging intracellular solution; while the latter, enhanced by robotic techniques (local scan force feedback, augmented reality vision feedback), can generate force stimuli with controllable patterns and magnitudes under the operator's real-time monitoring. To verify the performance of the developed system, we first measured the whole-cell current of the voltage-gated potassium ion channel Kv1.1 expressed on Human Embryonic Kidney (HEK293) cells and then recorded the mechanosensitive ion channel current in a mouse neuroblastoma cell line (Neuro2 A) in the whole-cell configuration during the AFM indenting on the membrane surface; finally, confirmed the ability to exchange intracellular solution by delivering propidium iodide into the captured cell through intracellular solution. The results prove the effectiveness of the system.
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 102
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    Adaptive Fault-Tolerant Spacecraft Attitude Control Design With Transient Response Control (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper proposes an adaptive fault tolerant attitude controller, based on variable structure control, to address tracking control problem of spacecraft in the presence of unknown actuator failure, control input saturation and external disturbances. In contrast to traditional robust fault tolerant attitude controllers, the proposed controller is capable of controlling the transient response of the closed loop system by means of a dedicated parameter. Also this method does not require exact knowledge of the actuator faults and is implemented with uncertain value of fault information. By adjusting a simple parameter dynamically and using Lyapunov direct method and the properties of quaternion representation, the ultimate boundedness of attitude and angular velocity errors in presence of external disturbances is proven. Numerical simulations used to prove the success of proposed controller in achieving high attitude performance in the presence of external disturbances, inexact knowledge of fault information, actuator failures and control input saturation.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 103
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    Design and Development of a Single-Motor, Two-DOF, Safe Manipulator (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents the design and development of a novel two degrees-of-freedom safe robot manipulator. Magnetorheological clutches are incorporated in the design to enable antagonistic actuation at the joints. A single unidirectional motor supports bidirectional actuation of all joints. Unlike most current safe robots, high-quality actuation is preserved, while the manipulator weight and effective inertia are reduced. This is achieved by relocating the driving motor to the base of the robot. Moreover, magnetorheological clutches have been shown to pose superior torque to mass, and torque to inertia characteristics over conventional servo motors, further contributing to the reduction of manipulator mass and inertia. The manipulator exhibits both high performance and intrinsic safety as a result of mechanically passive dynamics. A set of experiments is performed to validate the manipulator performance.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 104
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    A Nonlinear Controller for Pneumatic Servo Systems: Design and Experimental Tests (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper is dedicated to the problem of pneumatic cylinder control without pressure measurement. Based on the theory of homogeneous, finite-time stable, ordinary differential equations, a state-feedback nonlinear controller is proposed. The closed-loop system stability is proved and an attraction domain of the controller is given. The performances and the effectiveness of the proposed controller are illustrated against an experimental setup consisting of a pneumatic cylinder controlled by a dSPACE dS1103 microcontroller.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 105
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    MRI-Safe Robot for Endorectal Prostate Biopsy (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper reports the development of an MRI-Safe robot for direct (interventional) MRI-guided endorectal prostate biopsy. The robot is constructed of nonmagnetic and electrically nonconductive materials, and is electricity free, using pneumatic actuation and optical sensors. Targeting biopsy lesions of MRI abnormality presents substantial clinical potential for the management of prostate cancer. This paper describes MRI-Safe requirements and presents the kinematic architecture, design, and construction of the robot, and a comprehensive set of preclinical tests for MRI compatibility and needle targeting accuracy. The robot has a compact and simple three degree-of-freedom (DoF) structure, two for orienting a needle-guide and one to preset the depth of needle insertion. The actual insertion is performed manually through the guide and up to the preset depth. To reduce the complexity and size of the robot next to the patient, the depth setting DoF is remote. Experimental results show that the robot is safe to use in any MRI environment (MRI-Safe). Comprehensive MRI tests show that the presence and motion of the robot in the MRI scanner cause virtually no image deterioration or signal-to-noise ratio change. Robot's accuracy in bench test, CT-guided in-vitro, MRI-guided in-vitro , and animal tests are 0.37, 1.10, 2.09, and 2.58 mm, respectively. These values are acceptable for clinical use.
    Print ISSN: 1083-4435
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 106
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    Estimating Dynamics On-the-Fly Using Monocular Video For Vision-Based Robotics (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: Estimating the physical parameters of articulated multibody systems (AMBSs) using an uncalibrated monocular camera poses significant challenges for vision-based robotics. Articulated multibody models, especially ones including dynamics, have shown good performance for pose tracking, but require good estimates of system parameters. In this paper, we first propose a technique for estimating parameters of a dynamically equivalent model (kinematic/geometric lengths as well as mass, inertia, damping coefficients) given only the underlying articulated model topology. The estimated dynamically equivalent model is then employed to help predict/filter/gap-fill the raw pose estimates, using an unscented Kalman filter. The framework is tested initially on videos of a relatively simple AMBS (double pendulum in a structured laboratory environment). The double pendulum not only served as a surrogate model for the human lower limb in flight phase, but also helped evaluate the role of model fidelity. The treatment is then extended to realize physically plausible pose-estimates of human lower-limb motions, in more-complex uncalibrated monocular videos (from the publicly available DARPA Mind’s Eye Year 1 corpus). Beyond the immediate problem-at-hand, the presented work has applications in creation of low-order surrogate computational dynamics models for analysis, control, and tracking of many other articulated multibody robotic systems (e.g., manipulators, humanoids) using vision.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 107
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    A Simple and Parallel Algorithm for Real-Time Robot Localization by Fusing Monocular Vision and Odometry/AHRS Sensors (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: Vision and odometry/attitude and heading reference system (AHRS, three-axial gyroscopes, accelerometers, and magnetometers) sensors fusion strategy is prevalent in the recent years for the robot localization, due to its low cost and effectiveness in global positioning system (GPS)-denied environments. In this paper, a new adaptive estimation algorithm is proposed to estimate the robot position by fusing the monocular vision and odometry/AHRS sensors, and utilizing the properties of perspective projection. By the new method, the robot can be localized in real time in the GPS-denied and mapless environments, and the localization results can be theoretically proved convergent to their real values. Compared to other methods, our algorithm is simple to implement and suitable for parallel processing. To achieve the real-time performance, the algorithm is implemented in parallel using graphics processing unit (GPU), and therefore, it can be easily integrated into mobile robots’ tasks like navigation and motion control, which need the real-time localization information. Simulations and experiments were conducted to validate the good convergence and longtime robustness performances of the proposed real-time localization algorithm.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 108
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    IEEE/ASME Transactions on Mechatronics information for authors (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Print ISSN: 1083-4435
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 109
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    IEEE/ASME Transactions on Mechatronics publication information (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Print ISSN: 1083-4435
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 110
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    Tracking of Triangular Reference Signals Using LQG Controllers for Lateral Positioning of an AFM Scanner Stage (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents the design of an internal reference model-based optimal linear quadratic Gaussian (LQG) controller for the lateral positioning of a piezoelectric tube actuator (PTA) used in an atomic force microscope (AFM). In this control design, internal modeling of the reference signal and system error are considered. As a result, the steady-state tracking error is minimized. In addition to the LQG controller, a vibration compensator is incorporated with the plant to suppress the vibration of the PTA at the resonance frequency. It achieves a high closed-loop bandwidth and significant damping of the resonant mode of the PTA, which enables a reference triangular signal to be tracked. Comparison of performance of the optimal LQG controller augmented with a vibration compensator and a PI controller demonstrates that the proposed controller shows significant improvements over the existing AFM PI controller.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 111
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    Event-Based Localization in Ackermann Steering Limited Resource Mobile Robots (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents a local sensor fusion technique with an event-based global position correction to improve the localization of a mobile robot with limited computational resources. The proposed algorithms use a modified Kalman filter and a new local dynamic model of an Ackermann steering mobile robot. It has a similar performance but faster execution when compared to more complex fusion schemes, allowing its implementation inside the robot. As a global sensor, an event-based position correction is implemented using the Kalman filter error covariance and the position measurement obtained from a zenithal camera. The solution is tested during a long walk with different trajectories using a LEGO Mindstorm NXT robot.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 112
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    Shape Tracking of Planar Hyper-Flexible Beams via Embedded PVDF Deflection Sensors (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: In this paper, we present an embedded shape-sensing method for soft robotics. Soft actuators and structures are paramount for safe human–robot interaction and are of interest in biomimetics, biotechnology and defense. Control of compliant manipulators is challenging because of their large deformations, hence a form of shape feedback is required. We propose a tracking system for continuum structures using deflection sensors made of polyvinylidene fluoride (PVDF), a thin piezoelectric polymer. We demonstrate that hyper-flexible beam shapes may be parameterized with a small set of basis functions and that the deflection sensors can be used to determine the weights of the basis functions. In other words, shape reconstruction of the beam shape is reduced to solving a linear interpolation problem defined by the sensors. Interpreting the sensors with this method can reduce the cumulative errors associated with piecewise methods. We demonstrate shape tracking of a hyper-flexible beam in two-dimensional (2-D) on two experimental test beds: a pneumatic bellows actuator and a hyper-flexible plastic ruler. In addition, the data were used in simulation, for systematic investigation of several aspects: number of sensors, their relative-size, and the type of basis functions used for parameterization. We demonstrate tracking capabilities and propose guidelines for the ideal sensor layout. Our approach facilitates kinematic monitoring and control of continuum manipulators and flexible structures.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 113
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    Adaptive Knee Joint Exoskeleton Based on Biological Geometries (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents a relatively complete analytical model of a knee joint interacting with a two-link exoskeleton for investigating the effects of different exoskeleton designs on the internal joint forces/torque in the knee. The closed kinematic chain formed by the leg and exoskeleton has a significant effect on the joint forces/torque in the knee. A bio-joint model is used to capture this effect by relaxing a commonly made assumption that approximates a knee joint as a perfect engineering pin-joint in designing an exoskeleton. Based on the knowledge of a knee-joint kinematics, an adaptive knee-joint exoskeleton has been designed to eliminate negative effects associated with the closed leg-exoskeleton kinematic chain on a human knee. For experimental validation, the flexion motion of an artificial human knee is investigated comparing the performances of five exoskeleton designs against the case with no exoskeleton. Analytical results that estimate internal forces/torque using the kinematic and dynamic models (based on the properties of a knee joint) agree well with data obtained experimentally. This investigation illustrates the applications of the analytical model for designing an adaptive exoskeleton that minimizes internal joint forces due to a knee-exoskeleton interaction.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 114
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    Bioinspired Hydrodynamic Force Feedforward for Autonomous Underwater Vehicle Control (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: It is believed that the lateral line found in most fish and some other aquatic organisms plays an important role in many behaviors by providing hydrodynamic information about the surrounding fluid. This paper presents a lateral line inspired feedforward control design for the autonomous underwater vehicles. The goal of this paper is to improve maneuvering accuracy for underwater exploration and environmental monitoring. The proposed controller takes pressure measurements at multiple locations over the entire vehicle hull and forms a B-spline surface approximation of the pressure distribution. Hydrodynamic forces acting on the vehicle are then estimated and passed to the controller for the improved trajectory tracking performance. The algorithm is formulated in such a way that the force estimation is a linear, fixed weight combination of the pressure signals, which enables rapid online computation. The performance of the feedforward controller is simulated in conjunction with the “robust integral of the sign of the error” control design. Trajectory tracking is investigated for control accuracy in the presence of localization errors. Reduced tracking errors are observed with the feedforward design. Experimental tests with pressure sensors on a moving cylinder further vindicate the force estimation algorithm.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 115
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    Active Motion Control of a Hydraulic Free Piston Engine (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: The free piston engine (FPE), as an alternative of the conventional internal combustion engine, could significantly impact the energy consumption and emissions of both on-highway and off-highway vehicles. In an FPE, the piston motion is dependent on the combustion chamber gas dynamics and the loading dynamics in real time. One of the technical barriers that prevents the wide spread of this technology is the lack of precise piston motion control. In this paper, we present the modeling and control of a hydraulic FPE with an opposed-piston opposed-cylinder design. Specifically, a comprehensive system model is first built and validated to study the dynamics of the engine operation. The simulation studies lead to the design of an active piston motion controller, which acts as a virtual crankshaft by utilizing energy in the storage element to regulate the piston to follow a predefined trajectory. With a designated optimal trajectory, the virtual crankshaft ensures stable and robust operation in engine motoring. Preliminary combustion testing results and analysis are also included in this paper.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 116
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    Energy Regenerative Suspension Using an Algebraic Screw Linkage Mechanism (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents the development of a novel energy-regenerative suspension mechanism. The system consists of a mass-spring unit coupled with an algebraic screw kinematic pair, a rotary permanent magnet synchronous generator (PMSG), and a three-phase boost charger connected to a battery. The algebraic screw converts the translational vibration into a reciprocating rotary motion which drives the PMSG through a planetary gearhead. A pulse-width-modulated three-phase boost converter is then used to convert the energy generated by the rotary machine into battery charge. To this end, a control and switching algorithm is utilized that makes the battery appear as a pseudo-resistor across the terminals of the rotary machine. Introducing this pseudo-resistive characteristic across the machine produces the same effect as mechanical damping with an energy regenerative function. The design and analysis of the regenerative suspension mechanism are presented by considering the dynamics of the electromechanical device, parameters of the suspension system, and the base excitation input profile. Experimental results are presented that evaluate performance of the proposed regenerative damper on a small-scale suspension system, which demonstrate the feasibility of building energy-regenerative dampers.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 117
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    Soft Actuator Mimicking Human Esophageal Peristalsis for a Swallowing Robot (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: Provision of modified foods and drinks is one of the approaches for dysphagia management, which is based on the assumption that food with proper texture and rheological properties will allow dysphagia patients to swallow safely and maintain adequate nutrition. However, lack of information about the in vivo swallowing process and its interaction with food flow has obstructed the effective management of dysphagia. In the esophageal swallowing stage, masticated food is transported through the esophagus to the stomach by a peristaltic mechanism, which is generated by sequential contraction and relaxation of esophageal muscles. Inspired by this behavior, a soft actuator is proposed to provide a nonrisk environment aiming to facilitate investigations of the most effective properties of food for the management of the swallowing disorders. The wave-like motion is first specified according to the in vivo measurement of human esophageal peristalsis. Finite-element analysis simulations are carried out to aid the structure design before prototype manufacture. Constructed by casting silicon rubber in a three-dimensional (3-D) printed customized mold, the novel actuator has soft structure resembling its human counterpart, which has a flexible muscular structure. Multiple layers of inflatable chambers are embedded and distributed along the axis of a food passage regularly, which locates at the center of the actuator. The actuator is capable of generating a peristaltic wave and pushing a bolus along the passage. The closure of the tube and the velocity of the propagation wave are going to be adjusted to achieve the trajectories recorded experimentally, by regulating the compressed air pressure pumped into chambers actively.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 118
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    Reduced-Order Dynamic Model of Permanent Magnet and HTSC Interaction in an Axisymmetric Frame (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: This paper presents a reduced order model for a permanent magnet (PM) and high-temperature superconductor (HTSC) in an axisymmetric frame. This model is formulated as a bond-graph to aid integration into system models for applications such as lift bearings, where the nonlinear force–displacement interactions are important for stability analysis and control design. The reduced-order model is based on the mechanical and electromagnetic interaction between a PM and bulk HTSC. Performance of the proposed reduced-order model is compared to finite element method (FEM) analysis and experimental tests to confirm the static and transient performance.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 119
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    Impulsive Actuation in Robot Manipulators: Experimental Verification of Pendubot Swing-Up (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: There are many benefits of using impulsive actuation in dynamical systems; therefore, control systems with impulsive inputs have been widely investigated. All of these investigations, however, have been theoretical in nature and few have reported experimental implementation. This paper discusses continuous-input approximations of impulsive forces in robot manipulators and their implementation in a simple pendulum (one-link robot) using an electric motor. The insights gained from the pendulum experiments are used to implement an existing algorithm for swing-up of the pendubot based on impulsive forces. The experimental results validate the swing-up algorithm but, more importantly, establish the feasibility of using impulsive inputs for robots and other electromechanical systems.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 120
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    IEEE Xplore Digital Library (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 121
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    Memory-Based Passivation Approach for Stable Haptic Interaction (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: Inspired from the graphical interpretation of passivity in a position versus force xy graph, this paper proposes a new concept of passivation method to increase the dynamic range of impedance in which a haptic interface can passively interact. The position versus force graph represents the energy behavior in a one-port haptic interface while the haptic interface is traveling in (pressed) or out of (released) a virtual environment (VE). It interprets that to make the one-port system passive, it is sufficient to bound the releasing path below the pressing path in the position versus force graph. To realize the bound, the computed force output from the VE is saved into a designated memory, addressed by current position, while the haptic interface is pressed. Thereafter, the saved force can be reused to upper-bound the releasing path below the saved pressing path while the haptic interface is released. The proposed method is generalized from preliminary work by including interaction with a moving virtual object and multi-DOF extension, together with more systematic and detailed explanations about the methods. In particular, we reconfigure the one-port moving virtual object as a two-port haptic controller and a connected one-port moving inertia. This reconfiguration allows implementation of the preliminary approach including the interaction with moving virtual objects by using an error versus force passivity instead of a position versus force passivity. This two-port extension also allows generalization of the proposed method to multi-DOF interactions by introducing virtual proxy as a virtual moving object. The proposed method is tested with a single and a multi-DOF haptic interface and shows better performance than the recently proposed field-programmable gate array-based time-domain passivity approach .
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    Magnetic Signature Attenuation of an Unmanned Aircraft System for Aeromagnetic Survey (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-04-30
    Description: A novel magnetic signature attenuation technique based on reconfiguring the location and orientation of the onboard magnetic sources of an unmanned aircraft system (UAS) is presented in this paper. The UAS, GeoSurv II, is intended for high-resolution aeromagnetic survey which requires the magnetic signature of the aircraft to be very low. Genetic algorithm (GA) is used to find an optimum configuration given multiple objective functions motivated by the application. The magnetic field contribution from a single servomotor onboard GeoSurv II is modeled as a single permanent magnet dipole, which is then used to build the cost function for the GA routine. The optimization/simulation outcome suggests very little alteration in the current configuration of the GeoSurv II servomotors resulting in a substantial improvement of the overall magnetic signature of the UAS. The simulation results are validated by practical experimentation. The experimental results, in addition to the simulation results, further confirm that the GA optimized configuration substantially outperforms the current configuration in terms of magnetic signature of GeoSurv II.
    Print ISSN: 1083-4435
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    Polymer-Based Flexible Visuo-Haptic Display (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: We report a flexible visuo-haptic display that allows for interactive haptic feedback on the visual display. The visuo-haptic display is fabricated by integrating a dielectric elastomer (DE) based thin film actuator array into a flexible display and pressure sensors. The DE actuator array consists of nine active cells, which generate thickness-mode deformation in response to voltage signal. The flexible display presents images of the aligned three alphabet characters at each section in 3 × 3 matrix during light propagation via optical multiwaveguide. The pressure sensors are placed on the bottom of the DE actuator array for haptic feedback. The performance of the DE actuators is proved to be capable of realizing sufficient vibro-tactile sensation in the perceivable range of human touch sense. The integrated system enables the visual display to provide interactive haptic feedback such as key pressing, contact vibration sensations, etc., in accordance with user input.
    Print ISSN: 1083-4435
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    Nonlinear Controller With the Dead-Zone and Saturation for Optical Disk Drive Systems in the Presence of External Shocks (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Description: In this paper, a nonlinear controller with dead-zone and saturation is proposed in order to improve the antishock performance. Since using dead-zone and saturation improves the stability margin, we can use a higher gain for the dead-zone than in the previous methods. In addition, we find that the overall controller with a linear lead-lag controller has an improved stability margin over controllers with the PID linear control in this application. The experimental results confirmed that the proposed method provides improved protection against external shock.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    Do what you do better with What's New @ IEEE Xplore (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-04-30
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Local melting/solidification during peritectic solidification in a steep temperature gradient: analysis of a directionally solidified Al–25at%Ni (2014)
    Springer
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    Publication Date: 2014-03-05
    Description: Melting of primary Al 3 Ni 2 phase and solidification of Al 3 Ni peritectic phase during directional solidification of an Al–25at%Ni peritectic alloy have been investigated. In a steep temperature gradient of up to 50 K/mm and at a pulling rate of 20 μm/s, an incomplete coverage of peritectic Al 3 Ni phase on the surface of the primary Al 3 Ni 2 phase has been observed. Below the peritectic temperature in the presence of the incomplete coverage, melting of primary Al 3 Ni 2 on the one side and solidification to the Al 3 Ni peritectic phase on the other side proceed swiftly via diffusion through the interphase liquid layer. Theoretical calculations based on an incomplete-coverage-related melting/solidification model are in close agreement with the experimental measurements.
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    Effect of magnetic field annealing and size on the giant magnetoimpedance in micro-patterned Co-based ribbon with a meander structure (2014)
    Springer
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    Publication Date: 2014-03-05
    Description: Micro-patterned Co-based amorphous ribbons (Metglas ® 2714A) with a meander structure are fabricated by MEMS technology and the giant magnetoimpedance (GMI) effects are measured at different magnetic fields and frequencies. The effect of magnetic field annealing and size (line width and line length) on the GMI effect is investigated. It is found that the GMI effect in the transverse magnetic field-annealed state is larger than that in longitudinal magnetic field-annealed state and nonfield-annealed state. The maximum GMI effect increases from 82 % for the sample with 5 mm length to 150 % for the sample with 10 mm length, and the maximum GMI effect decreases with the increase of the line width.
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    Nanoparticle plume dynamics in femtosecond laser ablation of gold (2014)
    Springer
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    Publication Date: 2014-03-05
    Description: This paper describes some recent results on femtosecond laser ablation of gold. We have studied both the fast vapour/plasma and slow nanoparticle plumes using Langmuir probe, time-resolved ICCD imaging and time-resolved optical absorption measurements. The nanoparticle plume dynamics was analysed by comparing the optical emission absorption measurements with an adiabatic isentropic model of ablation plume expansion, leading to an estimate of the amount of material in the nanoparticle plume.
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    Hydrothermal synthesis of 3D Cu 0.45 Mn 0.55 O 2 nanostructures; lattice vibrations and novel photoluminescence properties (2014)
    Springer
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    Publication Date: 2014-03-20
    Description: In this paper, Novel 3D Cu 0.45 Mn 0.55 O 2 nanoarchitectures self-assembled by interconnecting densely stacked nanosheets have been successfully synthesized by facile hydrothermal growth method. The crystalline phase, morphology, particle size and component of the as-prepared nanomaterial were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy and Raman spectroscopy. FESEM analysis shows that the size of 3D Cu 0.45 Mn 0.55 O 2 nanostructures is in the range of 1–1.5 μm, and the thickness of interconnected nanosheets is about 45 nm on the average. The structural features of as-synthesized Cu 0.45 Mn 0.55 O 2 nanostructures are studied to analyze the near-neighbor environment of oxygen coordination around manganese and copper cations reported for the first time using Raman scattering spectroscopy. Moreover, the novel photoluminescence spectra of the as-prepared Cu 0.45 Mn 0.55 O 2 nanostructures are reported exhibiting prominent emission bands located in red-violet spectral region.
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    Size, crystal structure and morphology changes of IATO nanoparticles effect on its optical property (2014)
    Springer
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    Publication Date: 2014-03-20
    Description: Controlling and changing size, crystal structure and morphology of antimony and tin-doped indium oxide (IATO) nanoparticles can effectively influence their specific optical properties. Nanocube-like, nanorod-like and nanosphere-like IATO nanoparticles have been fabricated from 20 to 200 nm in diameter by sintering as-prepared precursors with distinct crystallographic structures and morphologies. These nano-sized precursors are either cubic In(OH) 3 or orthorhombic InOOH with different crystallographic sizes and shapes due to the use of different solvents (deionized water, absolute ethyl alcohol and ethylene glycol) in hydrothermal synthesis process. Characterization and comparison of experimental samples have detailedly demonstrated that desired optical properties of IATO nanoparticles should be attained by appropriate change of size, crystal structure and morphology of IATO nanoparticles.
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    Improving metal-enhanced photoluminescence by micro-pattern of metal nanoparticles: a case study of Ag–ZnCdO system (2014)
    Springer
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    Publication Date: 2014-03-20
    Description: Micro-pattern of Ag nanoparticles and Ag film is inserted between ZnCdO film and the substrate to enhance the photoluminescence (PL) of ZnCdO films, achieving enhancement ratio of 21.2 and 7.1, respectively. Time-resolved photoluminescence shows that the PL lifetime of Ag/ZnCdO films is longer than that of bare ZnCdO, which is attributed to surface modification and surface plasmons coupling. The improved enhancement in the sample with Ag pattern is attributed to the fact that periodic Ag structure offers additional scattering mediums and thus increases the light extraction efficiency.
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    Mathematical Modeling of Moisture Sorption Isotherms and Determination of Isosteric Heats of Sorption of Ziziphus Leaves (2014)
    Hindawi
    Details
    Publication Date: 2014-04-28
    Description: Desorption and adsorption equilibrium moisture isotherms of Ziziphus spina-christi leaves were determined using the gravimetric-static method at 30, 40, and 50°C for water activity ranging from 0.057 to 0.898. At a given , the results show that the moisture content decreases with increasing temperature. A hysteresis effect was observed. The experimental data of sorption were fitted by eight models (GAB, BET, Henderson-Thompson, modified-Chung Pfost, Halsey, Oswin, Peleg, and Adam and Shove). After evaluating the models according to several criteria, the Peleg and Oswin models were found to be the most suitable for describing the sorption curves. The net isosteric heats of desorption and adsorption of Ziziphus spina-christi leaves were calculated by applying the Clausius-Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was given.
    Print ISSN: 1687-5591
    Electronic ISSN: 1687-5605
    Topics: Computer Science , Technology
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    Structural and optical properties of ZnSe thin films stacked with PbSe submonolayers (2014)
    Springer
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    Publication Date: 2014-03-05
    Description: Structural and optical properties of Zinc Selenide (ZnSe) thin films stacked with multiple Lead Selenide (PbSe) submonolayers (ML) were studied. Thermal evaporation was preferred to produce ZnSe–PbSe thin films with the PbSe ML thickness ranges from 2.5 to 10 nm. Polycrystalline nature of the ZnSe was revealed through high resolution X-ray diffractometer measurement. The development of micro strain at the interfaces with increasing PbSe ML thickness was observed. A cross-sectional TEM image shows well-ordered periodicity and reproducibility of the layer thickness. The enhancement of optical absorption of ZnSe was identified upon stacking of PbSe ML. The evidence for quantum confinement in PbSe ML was revealed by the obtained red shift in band gap (2.5–1.8 eV) values as well as photoluminescence emission at 1,071 nm. The presence of tensile strain in the ZnSe layers upon staking of PbSe ML was discussed by the shift in LO phonon modes in Raman spectra.
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    Regulating the thermal response of PNIPAM hydrogels by controlling the adsorption of magnetite nanoparticles (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Thermoswitchable magnetic hydrogels are being extensively investigated because of their great potential for medical applications. Indeed, they can behave as smart carriers able to transport drugs to a chosen part of the body and release them via magneto-thermal activation by an external alternating magnetic field. We report on the magnetization of the thermosensitive poly(N-isopropylacrylamide) hydrogel through the adsorption of controlled amounts of magnetite nanoparticles. We show that the temperature at which the hydrogel contraction occurs (i.e. the lower critical solution temperature) can be controlled from 32  ∘ C to 52  ∘ C by varying the concentration of adsorbed nanoparticles. This is clearly shown by photon correlation spectroscopy. The results are an advance in the use of the magnetized poly(N-isopropylacrylamide) hydrogel as a flexible and adjustable nanomaterial and are of great interest in numerous applications which require drug release on demand.
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    Direct fabrication of graphene/zinc oxide composite film and its characterizations (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Graphene-based composites represent a new class of materials with potential for many applications. Graphene can be attached to a metal, a semiconductor, or any polymer for enhancing properties. In this work, a new mixed dispersion approach for graphene-based composite has taken on. Graphene flakes (〈4 layers) and a well-known semiconductor zinc oxide (ZnO) (〈50 nm particle size) have dispersed in N -methyl-pyrrolidone. We deposited graphene/ZnO composite thin film by a simple, low-cost, environmentally friendly and non-vacuum electrohydrodynamic atomization process on silicone substrate. Experiments have been carried out by changing flow rate and applied potential while keeping stand-off distance and substrate velocity constant, to discover the optimum conditions for obtaining a high-quality thin film. It has been explored that high-quality thin composite film is obtained at optimum flow rate of 300 μl/h at 6.3 kV applied potential after curing for 2 h at 300 °C. Graphene/ZnO thin composite film has been characterized using Field emission scanning electron microscopy, Ultra-violet Visible near Infra Red spectroscopy, X-ray diffraction, Raman Spectroscopy and 3D-Nanomap. For electrical behavior analysis, a simple diode Indium tin oxide/(poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/polydioctylfluorene-benzothiadiazole(F8BT)/(Graphene/ZnO) has fabricated. It is observed that at voltage of 0.3 V, the current in organic structure is at low value of 1.20 × 10 −3  Amp/cm 2 and after that as further voltage was applied, the device current increased by the order of 110 and reaches up to 1.32 × 10 −1  Amp/cm 2 at voltage 2 V.
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    The effects of chemical composition and distribution on the preservation of phytolith morphology (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Different types of phytolith even when coming from the same plant react to high temperatures in different ways. To understand the behavior of phytoliths upon heating, we examined composition and distribution of some elements within different phytolith types using SEM-EDS and synchrotron radiation μ-X-ray fluorescence. By analyzing phytoliths from rice husk, rice leaf and Than tree leaf, we find that the compositions and distributions of metal oxides within different phytolith types are quite different. It is well known that metal oxides have been used as fluxing agent to reduce the melting temperature of SiO 2 in the production of glass, and different metal oxides can be used to produce a variety of glass with diverse features. Similarly, metal elements including potassium, magnesium and calcium in phytoliths should also act as a fluxing agent under high temperature, and the differential compositions and distributions of these metal elements within the phytoliths resulted in the variable reaction to heating. In sum, there is a negative relationship between the flux elements composition in phytoliths, and the temperatures at which phytoliths deform; furthermore, potassium and calcium in the rice leaf phytolith are almost evenly distributed in all parts, which may cause the phytolith’s shape to deform evenly. In comparison, Than tree leaf phytolith is found to have a high percentage of potassium and calcium located exclusively on the outside, which may explain why the deformation of Than tree leaf phytolith occurs firstly at the outside.
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    Screen printing for producing ferroelectret systems with polymer-electret films and well-defined cavities (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: We report a process for preparing polymer ferroelectrets by means of screen printing—a technology that is widely used for the two-dimensional patterning of printed layers. In order to produce polymer-film systems with cavities that are suitable for bipolar electric charging, a screen-printing paste is deposited through a screen with a pre-designed pattern onto the surface of a polymer electret film. Another such polymer film is placed on top of the printed pattern, and well-defined cavities are formed in-between. During heating and curing, the polymer films are tightly bonded to the patterned paste layer so that a stable three-layer system is obtained. In the present work, polycarbonate (PC) films have been employed as electret layers. Screen printing, curing and charging led to PC ferroelectret systems with a piezoelectric d 33 coefficient of about 28 pC/N that is stable up to 100  ∘ C. Due to the rather soft patterned layer, d 33 strongly decreases already for static pressures of tens of kPa. The results demonstrate the suitability of screen printing for the preparation of ferroelectret systems.
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    Possibility of room-temperature multiferroism in Mg-doped ZnO (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Room-temperature multiferroic properties in Mg-doped ZnO samples are reported wherein Mg replaces Zn in the ZnO matrix and retains hexagonal wurtzite structure. The saturation magnetisation is increased from ∼2×10 −4  emu/g to 3×10 −4  emu/g for the dilute doping of 2 % Mg in pure ZnO and the ferroelectricity is also increased. Higher concentration of Mg does not lead to a significant enhancement in the magnetisation but improves the ferroelectric properties. An X-ray absorption spectroscopic study shows an enhancement in O vacancies with dilute doping of Mg. The origin of the multiferroic behaviour is understood based on their crystal and electronic structures.
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    Size exclusion chromatography for analyses of fibroin in silk: optimization of sampling and separation conditions (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: A direct goal of this paper was to improve the methods of sample preparation and separation for analyses of fibroin polypeptide with the use of size exclusion chromatography (SEC). The motivation for the study arises from our interest in natural polymers included in historic textile and paper artifacts, and is a logical response to the urgent need for developing rationale-based methods for materials conservation. The first step is to develop a reliable analytical tool which would give insight into fibroin structure and its changes caused by both natural and artificial ageing. To investigate the influence of preparation conditions, two sets of artificially aged samples were prepared (with and without NaCl in sample solution) and measured by the means of SEC with multi angle laser light scattering detector. It was shown that dialysis of fibroin dissolved in LiBr solution allows removal of the salt which destroys stacks chromatographic columns and prevents reproducible analyses. Salt rich (NaCl) water solutions of fibroin improved the quality of chromatograms.
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    Controllable vertically aligned ZnO nanorods on flexible polyethylene naphthalate (PEN) substrate using chemical bath deposition synthesis (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Zinc oxide (ZnO) nanorods were successfully grown on polyethylene naphthalate substrates with a seed layer using a wet chemical bath deposition method at a low temperature. Using various precursor concentrations, the diameter, length, and density of the ZnO nanorods were controlled, and their optical and crystallinity properties were investigated. X-ray diffraction and field emission scanning electron microscopy were used to examine the structure and morphology of the ZnO nanorods. The obtained ZnO nanorods were hexagonal and grew vertically from the substrate in the (002) direction along the c -axis. The low compressive strain values confirmed the high-quality crystal structure of the synthesized ZnO nanorods. A 0.050 M precursor concentration resulted in nanorods with a uniform diameter along their entire length and diameters ranging from 10 nm to 40 nm. The photoluminescence results indicated that the ZnO nanorods grown using a 0.050 M precursor concentration exhibited the sharpest and most intense PL peaks in the UV range compared with the other samples. Therefore, the precursor concentration considerably influenced the growth of the ZnO nanorods. These ZnO nanorods can be greatly applied for the development of flexible, elastic electronic, and optoelectronic devices.
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    Intermediate Ce 3+ defect level induced photoluminescence and third-order nonlinear optical effects in TiO 2 –CeO 2 nanocomposites (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: We report on the linear and nonlinear optical studies of TiO 2 –CeO 2 nanocomposites. It was found that the band gap of the nanocomposite can be tuned by varying Ce/Ti content. Nonlinear absorption characteristics of these samples were studied by employing open aperture Z-scan technique using an Nd:YAG laser (532 nm, 7 ns, 10 Hz). It has been observed that as the CeO 2 amount increases, band gap of the nanocomposites decreases and the reason proposed for the change in band gap is the smudging of localised states of Ce 3+ into the forbidden energy gap, thus acting as the intermediate state. Fluorescence studies confirmed the above argument. Nonlinear investigation revealed that with increase in the CeO 2 amount, the two-photon absorption coefficient increased due to the modification of TiO 2 dipole symmetry. Suitable candidature of the nanocomposites for the fabrication of nonlinear optical devices was proved by determining the optical limiting threshold.
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    Optimization of ZnSe film growth conditions for p-type doping (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Wide bandgap semiconductors such as ZnSe and ZnO have attracted great interest due to their applications in solar cells, light emitting diodes, and lasers. However, these wide bandgap semiconductors are frequently difficult to be doped to heavy concentrations, greatly limiting their application. A substrate holder with a natural temperature gradient was developed for batch growth of films at different deposition temperatures, in order to investigate ZnSe film growth and doping challenges. Thin ZnSe films were grown by pulsed laser deposition and characterized using X-ray diffraction, optical transmission and reflection, Raman spectroscopy, and Energy Dispersive X-ray analysis. Deposition temperature and film stoichiometry (Zn:Se) are shown to be significant factors affecting ZnSe growth and doping. ZnSe films with improved crystallinity have been obtained by enriching with selenium and depositing at an optimized temperature. Heavily p-type ZnSe films with hole concentrations of ~2.7 × 10 19  cm −3 and resistivities of ~0.099 Ohm cm have been obtained (compared with previous reports of ~1 × 10 18  cm −3 and ~0.75 Ohm cm). The results, which are consistent with previous theoretical prediction of compensating defects in ZnSe films, can help to optimize ZnSe growth conditions and understand doping challenges in wide bandgap semiconductors.
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    Effect of ultrasonic treatment before and after hydrothermal process on the morphologies and formation mechanism of ZnO nanorods (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: ZnO nanorods were fabricated by ultrasonic treatment before and after a hydrothermal process. The morphology and structure of the nanorods were individually characterized by scanning electron microscopy and X-ray diffraction. The results show that before the hydrothermal process, fore-ultrasonic treatment can directly gain ZnO nanorods which mainly experienced four conversion stages from initial bulk Zn(OH) 2 , a coexisting phase of bulk Zn(OH) 2 with ZnO nanoslices, ZnO nanoslices with flower-like ZnO nanorods and finally to purely flower-like ZnO nanorods. After the hydrothermal process, the post-ultrasonic treatment mainly influences the aggregation degree of the ZnO nanorods. The formation mechanism of ultrasonic treatment on ZnO nanorods is also discussed.
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    Identification of optimal ALD process conditions of Nd 2 O 3 on Si by spectroscopic ellipsometry (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: Variable angle spectroscopic ellipsometry (VASE) is used to investigate the thickness and optical properties of Nd 2 O 3 films deposited by atomic layer deposition (ALD) at various process conditions. It is found that the films exhibit good thickness uniformity and an almost constant growth rate of 0.42 Ǻ/cycle in the temperature region of 290–330 °C. Further examination of the imaginary part of the dielectric functions of the selected samples demonstrates that all optically observable dielectric-related defects are located in the interface layer between the silicon substrate and the native oxide rather than in the bulk Nd 2 O 3 layer. And, the defects within the band gap of the interface are found to be strongly affected by the deposition temperature. In the deposition temperature range of 300–320 °C, only one absorption peak of 3.53 eV besides the silicon substrate’s critical features is observed, indicating that the Si/SiO 2 /Nd 2 O 3 stacks contain the fewest interfacial defects. Then the optimal ALD process condition for Nd 2 O 3 is determined as Nd(thd) 3 (thd = 2,2,6,6,-tetramethyl-3,5-heptanedionato) evaporation temperature: 185 °C, deposition temperature: 300–320 °C, saturation condition: Nd(thd) 3 and pulse time longer than 0.5 s.
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    Photothermal investigation Study of ZnO thin films: effects of Zn and O polar substrate (2014)
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    Publication Date: 2014-01-26
    Description: ZnO thin films were grown by metal-organic chemical vapor deposition on Zn- and O-polar surfaces of ZnO substrate. The effect of Zn- and O-polar substrate on the surface morphology and opto-thermal proprieties has been studied. Hall-measurements were used to determine the carrier concentration of the deposited films. Photothermal deflection spectroscopy (PDS) was used to determine the optical absorption spectrum and the gap energy by comparing experimental amplitude of the photothermal signal to the corresponding theoretical one. Thermal conductivity and diffusivity were also deduced from the photothermal deflection measurements. The found values were very low due to the thermal resistivity of the layer–substrate interface.
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    Controlling magnetic properties of iron oxide nanoparticles using post-synthesis thermal treatment (2014)
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    Publication Date: 2014-01-26
    Description: Changes in morphological and magnetic properties of Fe 3 O 4 nanoparticles before and after annealing are investigated in the present work. The nanoparticles are synthesized in a standard capacitively coupled plasma enhanced chemical vapour deposition system with two electrodes using ferrocene as the source compound. Post annealing, due to the sintering process, the particles fuse along with recrystallization. This results in increased size of the nanoparticles and the interparticle interaction, which play a major role in deciding the magnetic properties. X-ray diffraction patterns of the samples before and after annealing indicate a phase change from Fe 3 O 4 to Fe 2 O 3 . Annealing at 200  ∘ C causes the apparent saturation magnetization to increase from 6 emu g −1 to 15 emu g −1 . When annealed at 500 ∘ C, the magnetic properties of the nanoparticles resemble those of the bulk material. The evidence for the transition from a superparamagnetic state to a collective state is also observed when annealed at 500 ∘ C. Variation of the magnetic relaxation data with annealing also reflects the change in the magnetic state brought about by the annealing. The correlation between annealing temperature and the magnetic properties can be used to obtain nanocrystallites of iron oxide with different sizes and magnetic properties.
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    Performance and stability studies of inverted polymer solar cells with TiO 2 film as a buffer layer (2014)
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    Publication Date: 2014-01-26
    Description: TiO 2 based inverted polymer solar cells (PSCs) with a structure of fluorine-doped tin oxide (FTO)/TiO 2 /P3HT:PCBM/PEDOT:PSS/Ag presented excellent air stabilities,; the power conversion efficiency (PCE) of devices exhibited only 15 % decay as compared to the highest value while being exposed in air-condition for more than 20 days. Interestingly, an overall enhancement of PCE from 3.5 % to 3.9 % was observed while the PSCs were exposed in air-condition up to 3 days; the improvement of performance was attributed to the TiO 2 films’ oxygen and water protection effect and the oxidation of Ag, which will benefit to form an effective work function match with the HOMO of P3HT leading to improved ohmic contact. However, the performance slowly decreased when the exposure time remains longer due to the physical adsorbed oxygen. UV–ozone treatment on the TiO 2 films’ leads to the formation of a metal-deficient oxide that results in a decreased PCE for the devices. Finally, X-ray photo-emission spectroscopy (XPS) was used to analyze the compositional changes of the TiO 2 films while they were exposed in air-condition or treated by UV–ozone.
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    Effect of laser annealing using high repetition rate pulsed laser on optical properties of phosphorus-ion-implanted ZnO nanorods (2014)
    Springer
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    Publication Date: 2014-01-26
    Description: The effect of high repetition rate pulsed laser annealing with a KrF excimer laser on the optical properties of phosphorus-ion-implanted zinc oxide nanorods has been investigated. The recovery levels of phosphorus-ion-implanted zinc oxide nanorods have been measured by photoluminescence spectra and cathode luminescence images. Cathode luminescence disappeared over 300 nm below the surface due to the damage caused by ion implantation with an acceleration voltage of 25 kV. When the annealing was performed at a low repetition rate of the KrF excimer laser, cathode luminescence was recovered only in a shallow area below the surface. The depth of the annealed area was increased along with the repetition rate of the annealing laser. By optimizing the annealing conditions such as the repetition rate, the irradiation fluence and so on, we have succeeded in annealing the whole damaged area of over 300 nm in depth and in observing cathode luminescence. Thus, the effectiveness of high repetition rate pulsed laser annealing on phosphorus-ion-implanted zinc oxide nanorods was demonstrated.
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    Light propagation in porous ceramics: porosity and optical property studies using tunable diode laser spectroscopy (2014)
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    Publication Date: 2014-01-26
    Description: By integrating gas in scattering media absorption spectroscopy and frequency domain photon migration a new method is developed for the study of optical porosity and optical properties of porous media, in our case ceramics. The optical porosity is defined as the ratio of the path length through the gas-filled pores and the physical path length through the whole medium. The effective refractive index of the porous ceramics is also retrieved based on the optical porosity, which is then used to evaluate the reduced scattering coefficients of the porous ceramics. The combined method provides a new way to study light propagation in porous media. A modified Looyenga model is proposed to study the relationship between the physical porosity and the effective refractive index of the porous medium, which also connects the optical and physical porosities, and provides the possibility to use the present method for porosimetry analysis.
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    Circular polarization converters based on bi-layered asymmetrical split ring metamaterials (2014)
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    Publication Date: 2014-02-03
    Description: In this paper, a kind of bi-layered asymmetrical split ring metamaterial was proposed as a circular polarization converter. Simulations and experiments at the microwave regime showed that the proposed structures can achieve the conversions from right-handed circularly polarized electromagnetic waves to left-handed ones and the reversed conversions in the opposite propagating direction. The linear to circular polarization transmission coefficients and the surface currents were investigated to understand the mechanism of the circular polarization conversions. Moreover, we optimized the proposed metamaterials by increasing the distance between the two metal layers. The proposed circular polarization converters have applications in microwave wave plates and metamaterial antennas.
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    Spectroscopic evidence of positive clusters in Ag colloids obtained by laser ablation in aqueous solutions (2014)
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    Publication Date: 2014-02-03
    Description: We have found evidence of positive cluster formation during the laser ablation process of a silver target in aqueous solutions. In particular, by employing in situ shot-by-shot UV–vis spectroscopy in the early stages of the ablation, we observed a weak and unstable absorption band around 266 nm and a more stable one around 290 nm, which could be assigned to charged clusters like Ag 3 2+ and Ag 4 2+ , respectively. Surface-enhanced Raman scattering experiments performed with a test molecule adsorbed on a silver colloid obtained in pure water were compatible with the presence of Ag 4 2+ active sites on the surface of the Ag nanoparticles.
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    Preliminary comparative study of laser-prepared DLC and Cr-doped DLC for bacteria adhesion (2014)
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    Publication Date: 2014-02-03
    Description: Diamond-like carbon (DLC) and Cr-doped DLC (chromium content 0–18 at.%) layers were deposited by dual pulsed laser ablation. The composition was analyzed using electron probe X-ray microanalysis with wavelength-dispersive spectrometers. Carbon and chromium bonds were determined by X-ray photoelectron spectroscopy. Ethylene glycol, diiodomethane and deionized water were used to measure contact angles and for the calculation of the surface free energy (SFE). Antibacterial properties were studied using gram positive and negative bacteria. The influence of the SFE, hydrophobicity, surface roughness and the zeta potential on antibacterial properties of doped layers was discussed. The relationships between physical and bio-properties are discussed.
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    Two intermediate bands solar cells of InGaN/InN quantum dot supracrystals (2014)
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    Publication Date: 2014-02-22
    Description: Two intermediate bands solar cells (2-IBSC) of In x Ga 1− x N/InN cubic quantum dot supracrystals were designed in this work. Position and width of the two IBs were determined, the performance parameters including short circuit current density, open circuit voltage and photoelectric conversion efficiency were numerically calculated, and their variations with adjustable variables such as In content, average size of QDs and interdot spacing were further discussed. Within a certain range, the influence from these adjustable variables on the first IB stronger than that on the second one was indicated. The cause of the maximum efficiency in the present cell lower than the one of another 2-IBSC with different material [Jenks and Gilmore, J Renew Sustain Energy 2:013111 ( 2010 )] was probed, while the reason for the maximum efficiency of the studying device near to that of 1-IBSC with same material [Zhang and Wei, Appl Phys A 113:75 ( 2013 )] was clarified.
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    IEEE/ASME Transactions on Mechatronics publication information (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    New Geometric Approaches to the Analysis and Design of Stewart–Gough Platforms (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: In general, rearranging the legs of a Stewart–Gough platform, i.e., changing the locations of its leg attachments, modifies the platform singularity locus in a rather unexpected way. Nevertheless, some leg rearrangements have been recently found to leave singularities invariant. Identification of such rearrangements is useful not only for the kinematic analysis of the platforms, but also as a tool to redesign manipulators avoiding the implementation of multiple spherical joints, which are difficult to construct and have a small motion range. In this study, a summary of these singularity-invariant leg rearrangements is presented, and their practical implications are illustrated with several examples including well-known architectures.
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    Bounded Assignment Formation Control of Second-Order Dynamic Agents (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: A constructive design of bounded formation controllers is proposed to force $N$ mobile agents with second-order dynamics to track $N$ reference trajectories and to avoid collision between them. Instead of a prior assignation of the reference trajectories to the agents, optimal assignment algorithms are used to assign desired reference trajectories to the agents to obtain optimal criteria such as linear summation and bottleneck functions of the initial traveling distances of the agents. After the reference trajectories are optimally assigned, the bounded formation control design is based on a new bounded control design technique for second-order systems and new pairwise collision avoidance functions. The pairwise collision functions are functions of both relative positions and relative velocities of the agents instead of only relative positions as in the literature. The proposed results are illustrated on a group of underactuated omnidirectional intelligent navigators in a vertical plane.
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    Robust Discrete-Time MRAC With Minimal Controller Synthesis of an Electronic Throttle Body (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: The electronic throttle body (ETB) is a fundamental actuator for regulating the air mass coming into an internal combustion engine; hence, it is used to control the engine torque in any modern drive-by-wire configuration. To cope with the nonlinear and discontinuous dynamics of this automotive device, in this paper a novel discrete-time model reference adaptive control (MRAC) method is designed and experimentally tested on an ETB installed on a 2-L engine. The control strategy extends the class of the minimal control synthesis (MCS) algorithms for discrete-time systems by adding an explicit discrete-time adaptive integral action and an adaptive robust term. An in-depth experimental investigation shows that the proposed control method is a viable solution as it is robust with respect to nonlinear torques acting on the plant, and it guarantees better performance than those provided by other MRAC strategies especially for small reference signals around the limp-home position where plant nonlinearities strongly affect the ETB dynamics.
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    Enhanced performance of InGaN light-emitting diodes with InGaN and composition-graded InGaN interlayers (2014)
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    Publication Date: 2014-02-23
    Description: The effects of InGaN light-emitting diodes (LEDs) with InGaN and composition-graded InGaN interlayers in the space of multiple quantum wells and electron blocking layer are studied numerically. The electrostatic field, energy band diagrams, carrier concentrations, light–current–voltage performances, and internal quantum efficiency (IQE) are investigated. Simulation results show that the light output power and IQE are both largely improved over the conventional LED structure due to the improvement in hole injection efficiency and electron blocking capability, especially for the LED with composition-graded InGaN interlayer.
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    Minimizing Energy Consumption of Wheeled Mobile Robots via Optimal Motion Planning (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents a new optimal motion planning aiming to minimize the energy consumption of a wheeled mobile robot in robot applications. A model that can be used to formulate the energy consumption for kinetic energy transformation and for overcoming traction resistance is developed first. This model will provide a base for minimizing the robot energy consumption through a proper motion planning. To design the robot path, the A $^*$ algorithm is employed to generate an energy-efficient path where a new energy-related criterion is utilized in the cost function. To achieve a smooth trajectory along the generated path, the appropriate arrival time and velocity at the defined waypoints are selected for minimum energy consumption. Simulations and experiments are performed to demonstrate the energy-saving efficiency of the proposed motion planning approach.
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    Modeling and Sensorless Direct Torque and Flux Control of a Dual-Airgap Axial Flux Permanent-Magnet Machine With Field-Weakening Operation (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents the modeling and motion-sensorless direct torque and flux control of a novel dual-airgap axial-flux permanent-magnet machine optimized for use in flywheel energy storage system (FESS) applications. Independent closed-loop torque and stator flux regulation are performed in the stator flux ( x–y) reference frame via two PI controllers. This facilitates fast torque dynamics, which is critical as far as energy charging/discharging in the FESS is concerned. As FESS applications demand high-speed operation, a new field-weakening algorithm is proposed in this paper. Flux weakening is achieved autonomously once the $y$ -axis voltage exceeds the available inverter voltage. An inherently speed sensorless stator flux observer immune to stator resistance variations and dc-offset effects is also proposed for accurate flux and speed estimation. The proposed observer eliminates the rotary encoder, which in turn reduces the overall weight and cost of the system while improving its reliability. The effectiveness of the proposed control scheme has been verified by simulations and experiments on a machine prototype.
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    Superconducting Noncontact Device for Precision Positioning in Cryogenic Environments (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: In this paper, a noncontact linear positioner based on superconducting magnetic levitation for high-precision positioning has been tested under cryogenic conditions (∼20 K and ∼10 $^{-6}$ Pa). The prototype is able to achieve submicrometric positioning resolution of 230 ± 30 nm RMS along a stroke of ±9 mm length with a current resolution of 15 μA, and a peak current requirement lower than ±500 mA. In addition, it was demonstrated that an open-loop control strategy could be used for positioning the moving part with the accuracy of the order of 1 μm. On the other hand, deviations of the slider position were found to be ±650 μrad for the pitch, lower than 100 μrad for the yaw, ±2000 μrad for the roll, and ±4 μm for the lateral run, all of them related to a full stroke motion. These results reveal a good performance of the device and demonstrate the potential of a new tool for applications, where high-precision positioning is required within a long range in cryogenic environments like far-infrared interferometry.
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    Dynamic Visual Servoing With Chaos Control for Redundant Robots (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents a new dynamic visual control system for redundant robots with chaos compensation. In order to implement the visual servoing system, a new architecture is proposed that improves the system maintainability and traceability. Furthermore, high performance is obtained as a result of parallel execution of the different tasks that compose the architecture. The control component of the architecture implements a new visual servoing technique for resolving the redundancy at the acceleration level in order to guarantee the correct motion of both end-effector and joints. The controller generates the required torques for the tracking of image trajectories. However, in order to guarantee the applicability of this technique, a repetitive path tracked by the robot-end must produce a periodic joint motion. A chaos controller is integrated in the visual servoing system and the correct performance is observed in low and high velocities. Furthermore, a method to adjust the chaos controller is proposed and validated using a real three-link robot.
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    Hybrid Power Plant Design for a Long-Range Dirigible UAV (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Unmanned aerial vehicle (UAV) dirigibles are well suited for surveillance and surveyance missions since they can hover and maintain lift without consuming energy and can be easily deflated for packaging and transportation. The challenge is developing a long endurance system while maintaining a low unit cost. This paper presents a novel hybrid power plant design that addresses both of these requirements. The lightweight design consists of a 4-stroke 14cc gasoline engine in-line with a brushless dc motor/generator and variable pitch propeller capable of producing a maximum power output of 250 W. A method was also developed to compare its performance and endurance to other power plant configurations that could be used in dirigible UAVs. Overall, the proposed hybrid power plant has 674% increase in energy density over that of a purely electric system, thereby proportionally increasing UAV flight time for the same power and weight.
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    Design and Optimization of a Tubular Linear Electromagnetic Vibration Energy Harvester (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents the design and optimization of tubular linear electromagnetic transducers (LETs) for the applications of large-scale vibration energy harvesting from vehicle suspensions, tall buildings, or long-span bridges. The LETs are composed of magnet and coil assemblies, which convert the vibration energy into electricity when moving relatively with each other. The parameters of the LETs, such as the thickness of the magnets in the axial direction and the thickness of the coils in the radial direction, are optimized using finite-element method to achieve high power density and damping density. Four LETs with different configurations namely, single-layer axial magnets and steel spacers, double-layer axial magnets and steel spacers, single-layer axial and radial magnets, double-layer axial and radial magnets are investigated for further improvement. It is found that the parameter optimization can increase the power density [W/m $^{3}$ ] of LETs to 3.8 times compared with the initial design by Zuo and coworkers, and the double-layer configuration with both radial and axial magnets can improve the power density up to 5.6 times, approaching to the energy dissipation rate of traditional oil dampers. A prototype using off-shelf axial NdFeB magnet is built and tested on a vibration shaker. The experiment results show that the prototype of 63.5 mm ( $2.5^{primeprime}$ ) outer diameter and 305 mm (12 in) compressed length can harvest 2.8 W power at 0.11 m/s relative velocity and provide a damping coefficient of 940 N·s/m. It is estimated that average 26–33 W electrical power and 1680–2142 N·s/m damping coefficient can be achieved at 0.25 m/s root-mean-square velocity for different LETs of $3^{primeprime}$ outer diameter and $12^{primeprime}$ compressed length.
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  • 165
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    Damping and Tracking Control Schemes for Nanopositioning (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Fast and accurate tracking of reference trajectories is highly desirable in many nanopositioning applications, including scanning probe microscopy. Performance in common positioning stage designs is limited by the presence of lightly damped resonances and actuator nonlinearities such as hysteresis and creep. To improve the tracking performance in such systems, several damping and tracking control schemes have been presented in the literature. In this paper, six different control schemes are presented and applied to a nanopositioning system for experimental comparison. They include schemes applying damping control in the form of positive position feedback, integral resonant control, integral force feedback, and passive shunt-damping. Also, general pole placement in the form of model reference control, as well as a control scheme requiring only a combination of a low-pass filter and an integrator, is presented. The control schemes are fixed-structure, low-order control laws, for which few results exist in the literature with regard to optimal tuning. A practical tuning procedure for obtaining good tracking performance for five of the control schemes is, therefore, presented. Experimental results show that the schemes provide similar performance, and the main differences are due to the specific implementation of each scheme.
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    High-Accuracy Tracking Control of Hydraulic Rotary Actuators With Modeling Uncertainties (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Structured and unstructured uncertainties are the main obstacles in the development of advanced controllers for high-accuracy tracking control of hydraulic servo systems. For the structured uncertainties, nonlinear adaptive control can be employed to achieve asymptotic tracking performance. But modeling errors, such as nonlinear frictions, always exist in physical hydraulic systems and degrade the tracking accuracy. In this paper, a robust integral of the sign of the error controller and an adaptive controller are synthesized via backstepping method for motion control of a hydraulic rotary actuator. In addition, an experimental internal leakage model of the actuator is built for precise model compensation. The proposed controller accounts for not only the structured uncertainties (i.e., parametric uncertainties), but also the unstructured uncertainties (i.e., nonlinear frictions). Furthermore, the controller theoretically guarantees asymptotic tracking performance in the presence of various uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems. Extensive comparative experimental results are obtained to verify the high-accuracy tracking performance of the proposed control strategy.
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    The Variable Stiffness Actuator vsaUT-II: Mechanical Design, Modeling, and Identification (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: In this paper, the rotational variable stiffness actuator vsaUT-II is presented. This actuation system is characterized by the property that the apparent stiffness at the actuator output can be varied independently from its position. This behavior is realized by implementing a variable transmission ratio between the internal elastic elements and the actuator output, i.e., a lever arm with variable pivot point position. The pivot point is moved by a planetary gears mechanism, which acquires a straight motion from only rotations, thereby providing a low-friction transmission. The working principle details of the vsaUT-II are elaborated and the design is presented. The actuator dynamics are described by means of a lumped parameter model. The relevant parameters of the actuator are estimated and identified in the physical setup and measurements are used to validate both the design and the derived model.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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  • 168
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    Design and Actuator Selection of a Lower Extremity Exoskeleton (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Lower extremity exoskeletons are wearable robots that integrate human intelligence with the strength of legged robots. Recently, lower extremity exoskeletons have been specifically developed for transportation of disabled individuals. This paper summarizes the anthropomorphic design of a lower extremity exoskeleton named “walking supporting exoskeleton (WSE).” WSE has been developed to support some fundamental motions (walking, sitting, standing, etc.) of disabled individuals who lost leg muscular activities completely or partially. WSE has two degrees of freedom per leg which are powered by electrical actuators. This paper discusses critical design criteria considered in mechanical design and actuator selection of WSE.
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  • 169
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    An Analytical Approach to Integral Resonant Control of Second-Order Systems (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Systems with colocated sensor–actuator pairs exhibit the interesting property of pole–zero interlacing. Integral resonance control (IRC) exploits this property by changing the pole–zero interlacing to zero-pole interlacing. The unique phase response of this class of systems enables a simple integral feedback controller to add substantial damping. Over the past few years, IRC has proven to be extremely versatile and has been applied to a wide variety of systems whose dominating dynamics of interest can be accurately modeled by second-order transfer functions. To date, a manual approach has been employed to determine the parameters of the IRC scheme, namely the feed-through term and the integral gain. In this paper, the relationship between the feed-through term, integral gain, and achievable damping is derived analytically for undamped/lightly damped second-order systems. The relationship between damping controller and an outer servo loop is also derived. These results add to the current understanding of colocated systems and automate the design of IRC controllers with a specified damping and tracking bandwidth. The presented results are applied to design and implement a damping and tracking controller for a piezoelectric nanopositioning stage.
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  • 170
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    An $bm{O(nlog n)}$ Shortest Path Algorithm Based on Delaunay Triangulation (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: In Euclidean and/or $lambda$ -geometry planes with obstacles, the shortest path problem involves determining the shortest path between a source and a destination. There are three different approaches to solve this problem in the Euclidean plane: roadmaps, cell decomposition, and potential field. In the roadmaps approach, a visibility graph is considered to be one of the most widely used methods. In this paper, we present a novel method based on the concepts of Delaunay triangulation, an improved Dijkstra algorithm and the Fermat points to construct a reduced visibility graph that can obtain the near-shortest path in a very short amount of computational time. The length of path obtained using our algorithm is the shortest in comparison to the other fastest algorithms with $O(nlog n)$ time complexity. The proposed fast algorithm is especially suitable for those applications which require determining the shortest connectivity between points in the Euclidean plane, such as the robot arm path planning and motion planning for a vehicle.
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  • 171
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    Sensorless Position Control For Piezoelectric Actuators Using A Hybrid Position Observer (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Soft piezoelectric actuators are extensively used in micro- and nanopositioning applications. Traditional sensorless position control approaches use a hysteresis mapping between voltage and position in a voltage feedforward control scheme in order to compensate for hysteresis errors. However, several factors such as frequency, temperature, and aging influence this mapping. Recently, charge control for positioning is also attracting interest among researchers due to the linear relationship between position and charge. However, a sophisticated hardware design is required to minimize charge drift. In this study, a new sensorless position control technique is proposed which requires neither an accurate inverse mapping nor a sophisticated charge amplifier in order to compensate for hysteresis. A constitutive relationship is employed to infer position from charge measurement through current integration. To eliminate drift from the charge-based measurement, an observer is presented in this study which uses a second self-sensing position estimate that is based on the variation of effective piezoelectric capacitance with stroke. The proposed observer is tested as a position feedback sensor inside a simple integrating control loop and applied to step profiles of variable stroke and sinusoidal profiles of constant and mixed frequencies. The responses are compared with a laser interferometer and the maximum observer error between the laser and the observer is 0.89 $,mu hbox{m}$ ( $〈$ 3% of the maximum stroke) over a frequency range of 10 to 100 Hz.
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  • 172
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    Optimization of Tension Distribution for Cable-Driven Manipulators Using Tension-Level Index (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Cable-driven manipulators (CDMs) are a special class of parallel manipulators driven by cables instead of rigid links. Due to the unilateral driving property of cables, CDMs require redundant actuation to maintain positive cable tensions. As a result of actuation redundancy, there exist an infinite number of possible cable tension solutions for a particular CDM pose. In this paper, a tension optimization method is proposed to obtain adjustable tension solution for CDMs. Adjustable tension solution is important because it enables the avoidance of tension limits and allows the stiffness of the CDM to be regulated. Tension-level indices are introduced to provide a systematic and practical way of setting the desired cable tensions level. The adjustable tension solution for each pose is obtained using a modified gradient projection method. The proposed method is generic and can be applied to CDMs with any number of redundant actuation. Simulation results show that the method is computationally efficient and the tension solutions can be manipulated by changing the tension-level indices. The simulation results have also been validated by experimental studies.
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  • 173
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    Data-Based Modeling of Vehicle Crash Using Adaptive Neural-Fuzzy Inference System (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Vehicle crashes are considered to be events that are extremely complex to be analyzed from the mathematical point of view. In order to establish a mathematical model of a vehicle crash, one needs to consider various areas of research. For this reason, to simplify the analysis and improve the modeling process, in this paper, a novel adaptive neurofuzzy inference system (ANFIS-based) approach to reconstruct kinematics of colliding vehicles is presented. A typical five-layered ANFIS structure is trained to reproduce kinematics (acceleration, velocity, and displacement) of a vehicle involved in an oblique barrier collision. Subsequently, the same ANFIS structure is applied to simulate different types of collisions than the one which was used in the training stage. Finally, the simulation outcomes are compared with the results obtained by applying different modeling techniques. The reliability of the proposed method is evaluated thanks to this comparative analysis.
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  • 174
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    Direct Joint Space State Estimation in Robots With Multiple Elastic Joints (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: For robots with joint elasticity, discrepancies exist between the motor side and the load side (e.g., the link of the robotic joint). Thus, the load side (end-effector) performance can hardly be guaranteed with motor side measurements alone. In this paper, a computationally efficient load side state estimation scheme is proposed for the multi-joint robot with joint elasticity, which is equipped with motor encoders and a low-cost end-effector MEMS sensor such as a three-axial accelerometer. An optimization-based inverse differential kinematics algorithm is developed to obtain the load side joint state rough estimates. With these rough estimates, the estimation problem is decoupled into simple second-order kinematic Kalman filter for each joint to refine the joint position and velocity estimates. Maximum likelihood principle is utilized to estimate the fictitious noise covariances used in the Kalman filter. Both offline and online solutions are derived. The extensions to other sensor configurations are discussed as well. The effectiveness of the developed method is validated through the simulation and the experimental study on a 6-DOF industrial robot.
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  • 175
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    Pressure-Distribution Methods for Estimating Lifting Force of a Swirl Gripper (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: The swirl gripper is a recently developed noncontact handling device that generates swirling air flow to create an upward lifting force. This force can be used to pick up a work piece placed underneath the swirl gripper without any contact. It is applicable, for example, in the semiconductor wafer manufacturing process, where contact must be avoided during the handling and moving of a work piece to minimize damage. For the purpose of indirectly estimating the lifting force of the swirl gripper, pressure-distribution methods are proposed and studied via theoretical analysis and experimental verifications in this paper. First, we show the design of the swirl gripper and briefly illustrate the mechanism by which it forms a negative pressure to create a lifting force. Then, we experimentally investigate the characteristics of the pressure distribution. Furthermore, we conduct a theoretical analysis of the pressure distribution and propose two methods for estimating the lifting force: one based on the rotation speed and a single pressure point (the ω–P method) and the other based on two pressure points (the P–P method). Then, we verify the proposed methods via a force measurement experiment. We find that the ω–P method causes considerable deviations in the calculated pressure distribution around the gap entrance of the swirl gripper, because of which the estimated force is smaller than the actual one. In contrast, we find that the P–P method can compensate for the error by directly detecting the pressure at the gap entrance with another pressure sensor. Our results show that the P–P method markedly improves the accuracy of estimating the lifting force as compared to the ω–P method. Finally, for the purpose of further improving the estimation accuracy, we increase the number of pressure points to estimate lifting force. It is made clear that the estimation accuracy is improved, and the effect is part- cularly significant for the P–P method.
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  • 176
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    Human Hand Motion Analysis With Multisensory Information (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: In order to study and analyze human hand motions that contain multimodal information, a generalized framework integrating multiple sensors is proposed and consists of modules of sensor integration, signal preprocessing, correlation study of sensory information, and motion identification. Three types of sensors are integrated to simultaneously capture the finger angle trajectories, the hand contact forces, and the forearm electromyography (EMG) signals. To facilitate the rapid acquisition of human hand tasks, methods to automatically synchronize and segment manipulation primitives are developed in the signal preprocessing module. Correlations of the sensory information are studied by using Empirical Copula and demonstrate that there exist significant relationships between muscle signals and finger trajectories and between muscle signals and contact forces. In addition, recognizing different hand grasps and manipulations based on the EMG signals is investigated by using Fuzzy Gaussian Mixture Models (FGMMs) and results of comparative experiments show FGMMs outperform Gaussian Mixture Models and support vector machine with a higher recognition rate. The proposed framework integrating the state-of-the-art sensor technology with the developed algorithms provides researchers a versatile and adaptable platform for human hand motion analysis and has potential applications especially in robotic hand or prosthetic hand control and human–computer interaction.
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  • 177
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    Design and Implementation of Model-Predictive Control With Friction Compensation on an Omnidirectional Mobile Robot (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents and discusses the implementation results of a model-predictive control (MPC) scheme with friction compensation applied to trajectory following of an omnidirectional three-wheeled robot. A cascade structure is used with an inverse kinematics block to generate the velocity references given to the predictive controller. Part of the control effort is used to compensate for the effects of static friction, allowing the use of efficient algorithms for linear MPC with constraints. Experimental results show that the proposed strategy is efficient in compensating for frictional effects as well as for tracking predefined trajectories.
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  • 178
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    Real-Time Estimation of Rollover Index for Tripped Rollovers With a Novel Unknown Input Nonlinear Observer (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Accurate detection of the danger of an impending rollover is necessary for active vehicle rollover prevention systems. A real-time rollover index is an indicator used for this purpose. A traditional rollover index detects only untripped rollovers that happen due to high lateral acceleration from a sharp turn. It fails to detect tripped rollovers that happen due to tripping from external inputs such as forces when a vehicle strikes a curb or a road bump. Therefore, this paper develops a novel new rollover index that can detect both tripped and untripped rollovers. A methodology is developed for estimation of unknown inputs in a class of nonlinear systems. The methodology is based on the nonlinear observer design and dynamic model inversion to compute the unknown inputs from output measurements. The observer design utilizes the mean value theorem to express the nonlinear estimation error dynamics as a convex combination of known matrices with time-varying coefficients. The observer gains are then obtained by solving linear matrix inequalities. The developed approach can enable observer design for a large class of differentiable nonlinear systems with a globally (or locally) bounded Jacobian. The developed nonlinear observer is then applied for rollover index estimation. The developed rollover index is also evaluated through simulations with an industry standard software, CARSIM, and with experimental tests on a 1/8th scaled vehicle. In order to verify that the scaled vehicle experiments can represent a full-sized vehicle, the Buckingham π theorem is used to show dynamic similarity. The simulation and experimental results show that the developed nonlinear observer can reliably estimate vehicle states, unknown normal tire forces, and rollover index for predicting both untripped and tripped rollovers.
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  • 179
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    A Force and Displacement Self-Sensing Piezoelectric MRI-Compatible Tweezer End Effector With an On-Site Calibration Procedure (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper describes a self-sensing technique for a piezoelectrically driven magnetic resonance imaging (MRI)-compatible tweezer style end effector, suitable for robot assisted MRI guided surgery. Nested strain amplification mechanisms are used to amplify the displacement of the piezo actuators to practical levels for robotics. By using a hysteretic piezoelectric model and a two port network model for the compliant nested strain amplifiers, it is shown that force and displacement at the tweezer tip can be estimated if the input voltage and charge are measured. One piezo unit is used simultaneously as a sensor and an actuator, preserving the full actuation capability of the device. An on-site calibration procedure is proposed that calibrates the combined electromechanical model without requiring specific loading conditions on the inner piezoelectric actuators. Experimental validation shows an average of 12% error between the self-sensed and true values.
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  • 180
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    Design and Experimental Evaluations on Energy Efficient Control Allocation Methods for Overactuated Electric Vehicles: Longitudinal Motion Case (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: The energy-efficient control allocation (EECA) scheme was previously proposed to distribute control efforts for overactuated systems by explicitly incorporating efficiency functions and working modes of redundant actuators. In this paper, three different real-time EECA schemes, namely adaptive EECA (A-EECA), KKT-based, and rule-based EECA, are proposed and compared for longitudinal speed tracking control of an electric ground vehicle (EGV) with two pairs of in-wheel motors. Two additional power resistor packs inserted in the dc circuits are applied to modify the operating efficiencies of two rear in-wheel motors, which are calibrated for experimental validations of the three EECA designs on a prototype EGV. In terms of the vehicle speed tracking performances, actuator dynamic responses, and total energy consumptions, both simulation and experimental results are evaluated and compared for the three distinct EECA methods. For the same EGV speed tracking effects, both simulation and experimental results indicate different power consumption savings are achieved by three EECA designs with different dynamic responses.
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    Comparing Approaches for Actuator Redundancy Resolution in Biarticularly-Actuated Robot Arms (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Biarticular actuators—actuators spanning two joints—play a fundamental role in robot arm designs based on the human musculoskeletal actuation structure. Unlike kinematic redundancy, actuator redundancy resulting from biarticular actuation brings advantages such as increased stability, reduced link inertia, and decreased nonlinearity of the end-effector force with respect to the force direction. The way the actuator redundancy is resolved is a fundamental problem, as it strongly characterizes robot arms performance. In this study, the six most significant actuation redundancy resolution approaches in the literature—1-norm, 2-norm, infinity-norm, phase different control (PDC), nonlinear hase different control (NLPDC), and linear programming (LP)—are analyzed with respect to their design, and experimentally compared with each other using BiWi, a biarticularly actuated and wire-driven robot arm. In addition, an integrated control framework to resolve actuator redundancy maximizing end-effector force and simultaneously minimizing the necessary input torques is proposed.
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  • 182
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    Quattroped: A Leg--Wheel Transformable Robot (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper reports on the design, integration, and performance evaluation of a novel four-leg/four-wheel transformable mobile robot, Quattroped. In contrast to most hybrid platforms that have separate mechanisms and actuators for wheels and legs, this robot is implemented with a unique transformation mechanism that directly switches the morphology of the driving mechanism between the wheels (i.e., a full circle) and 2 degrees of freedom leg (i.e., combining two half circles as a leg), so that the same system of actuation power can be efficiently utilized in both wheeled and legged modes. The design process, mechatronics, software infrastructure, behavioral development, and leg–wheel dynamic characteristics are described. The performance of the robot is evaluated in various scenarios, including driving and turning in wheeled mode, driving, step and bar crossing, irregular terrain passing, and stair climbing in legged mode. Taking advantage of the leg–wheel combination on a single platform, the comparison of the wheeled and legged locomotion is also discussed.
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    Safety-Function Design for the Control System of a Human-Cooperative Robot Based on Functional Safety of Hardware and Software (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: Human-cooperative robots (HCRs) are expected to benefit various fields. Safety functions are essential to the control system of HCRs because their hazardous movements after a system failure may cause serious injuries to operators. Therefore, their reliability must be sufficiently high relative to the estimated risk, and it is important to design a suitable safety function for the control system to match the safety level required for an HCR. We propose a methodology of safety-function design for the control system of an HCR and attempt to effectively combine design approaches for hardware and software of safety-related systems (SRSs) on the basis of the concept of functional safety. This study describes the details of the methodology for an HCR that we adopted as a platform system. First, SRS hardware with a dual-channel voting architecture was designed, and then, functional safety analysis was performed to verify whether the hardware satisfied the required safety integrity level (SIL). Next, SRS software with diverse programming, which is recommended for the required SIL, was designed by utilizing a disturbance observer. Finally, experiments were conducted on the SRS for representative failures and the safety function was verified for the control system, as set by the proposed methodology.
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    A Validated Feasibility Prototype for AUV Reconfigurable Magnetic Coupling Thruster (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: This paper presents the concept and design of a new reconfigurable magnetic-coupling thruster (RMCT). Mechanical models, as well as digital and real-world experiments, are proposed to understand the fundamental aspects of such technology. The principle of RMCT is to reorient the propeller, and therefore the thrust vector, to the desired direction without adding or moving any motors. The focus of this study is to propose a new design to solve the problems raised in a previous work on RMCT and to understand how the transmitted coupling torque behaves with regard to the new kinematics of the propeller shaft. After introducing the models underlying this thruster design, we build a numerical simulation and validate it through experimental results. The performance of this design is then discussed based on open-loop trials and its potential integration and control. The conclusion proposes guidelines for developing an underwater prototype that will be designed and tested on real autonomous underwater vehicles.
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    Dynamic Characteristics of Pressure Compensator in Underwater Hydraulic System (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
    Description: A pressure compensator for an underwater hydraulic system is studied in this paper. The compensator is used to maintain the tank pressure of the underwater hydraulic system so that it is slightly greater than the ambient pressure, allowing the system to work at any depth. The dynamic characteristics of the pressure compensator are studied using theoretical analysis, simulation and experiment. The tank pressure changes due to the step flow to the tank coming from the motion of a piston in a single-rod cylinder. This flow is caused by the unequal areas of the piston. The tank pressure change can be mathematically determined. A design procedure focusing on the dynamic characteristics of the pressure compensator is given. A compensator and underwater hydraulic system were built and the dynamic characteristics of the compensator were tested. Both simulation and experimental results conform to the analysis. The study provides a theoretical way to determine the dynamic characteristics of a pressure compensator in an underwater hydraulic system.
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    IEEE Xplore Digital Library (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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    Publication Date: 2014-02-22
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    Two ways to Access the IEEE Member Digital Library (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-02-22
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 188
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    Sliding-Mode Tracking Control With DNLRX Model-Based Friction Compensation for the Precision Stage (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-02-22
    Description: This paper concerns the development of a sliding-mode tracking controller with friction compensation for a precision positioning stage with cross-roller guides. Experiments including prerolling and rolling friction regimes are conducted, and then a two-stage parameter estimation algorithm is used to identify the parameters of a friction dynamic model (Dynamic NonLinear Regression with direct application of eXcitation, DNLRX, model). This model allows the estimation of the friction force in combination with the system dynamics against displacement, and can be used as a feed-forward controller to compensate for the friction effect. To compensate for model error and uncertain disturbances, an integral sliding-mode controller with a disturbance estimation scheme is designed and combined with the DNLRX feed-forward controller to control the motion of a precision stage. Experimental results show that with the proposed controller, tracking performance can be improved.
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 189
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    IEEE Global History Network (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-02-22
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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  • 190
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    A study on the pulsed laser printing of liquid-phase exfoliated graphene for organic electronics (2014)
    Springer
    Details
    Publication Date: 2014-02-25
    Description: The aim of this work is the pulsed laser printing of liquid-phase exfoliated graphene in the nanosecond regime and the optimization of the printing process on Si/SiO 2 and flexible polymer substrates (polyethylene naphthalate) via the laser-induced forward transfer technique (LIFT). The laser printing conditions and the optimum energy fluence window for reproducible deposition have been investigated, while the deposited graphene features have been studied morphologically and structurally by means of optical microscopy, micro-Raman spectroscopy and electrical characterization. LIFT experiments were carried out using the fourth harmonic (266 nm) of a pulsed ns Nd:YAG laser combined with a high-power imaging micromachining system to monitor the printing process throughout the experiments. The irradiation of our graphene solution resulted in the deposition of well-resolved patterns on different surfaces, highlighting LIFT as an alternative technique for the printing and patterning of liquid-phase exfoliated graphene for organic electronics applications.
    Print ISSN: 0947-8396
    Electronic ISSN: 1432-0630
    Topics: Technology , Physics
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  • 191
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    Resistive switching of in situ and ex situ oxygen plasma treated ZnO thin film deposited by atomic layer deposition (2014)
    Springer
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    Publication Date: 2014-02-25
    Description: In situ and ex situ oxygen plasma treatment (OPT) were applied to treat ZnO thin films deposited by thermal atomic layer deposition (T-ALD), and the resistive switching (RS) behaviors of the films were investigated. For the in situ OPT, the treatment was applied after each T-ALD cycle. For the ex situ OPT, the treatment was applied on the as-grown film. The T-ALD-grown ZnO films were defect-rich and conductive with no RS behavior. After the OPT process, the resistivity of the films increased drastically, which is believed to be mainly due to the removal of hydrogen impurities, and the films showed bipolar RS characteristics. The dominant conduction mechanisms are the trap-controlled space charge limited current and ohmic behavior at different field regions. The RS behavior was induced upon the formation/disruption of the conducting filaments. Owing to the homogeneous chemical composition and fewer defects, the resistance ratio of the in situ OPT ZnO film is higher than that of the ex situ OPT film, implying that the in situ OPT method is an efficient way to fabricate resistive random access memory devices using the ALD-grown ZnO films.
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    Topics: Technology , Physics
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  • 192
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    Fabricating and improving properties of copper matrix nanocomposites by electroless copper-coated MWCNTs (2014)
    Springer
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    Publication Date: 2014-02-25
    Description: In this study, copper (Cu) nanocomposites reinforced by coated multiwall carbon nanotubes (MWCNTs) have been fabricated with different weight fractions of MWCNT. In the first step, the as-received MWCNTs were coated with Cu using electroless deposition process. In the next step, combination of sonication and ball milling (with two milling time of 1.5 and 3 h) was used for preparing MWCNT/Cu composite powders. Finally, the disk-shaped specimens were sintered by hot-press sintering machine. Characterization of sintered nanocomposites revealed that increasing milling time led to improved mechanical properties, but higher defect density on the MWCNT sidewalls is obtained which is especially undesirable for electrical properties of nanocomposite. Our results indicated that simultaneous improvements of interface reactions and distribution uniformity of MWCNTs and Cu are key factors for obtaining enhanced mechanical properties. Accordingly, enhancement of up to ~150 and ~86 % in microhardness compared to pure Cu and 1 wt% as-received MWCNT/Cu was achieved by addition of 1 wt% Cu-coated MWCNT. On the contrary, existence of oxygen atoms in the Cu and coated MWCNT interface (from functional groups and deposited copper oxide) obstructs considerable improvement of electrical resistivity compared to as-received MWCNT/Cu nanocomposites.
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  • 193
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    Test object for emission electron microscope (2014)
    Springer
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    Publication Date: 2014-02-28
    Description: The resolution of emission electron microscopes approaches some nanometers, which leads to the need for new test objects. Microfields, which are almost always present at the sample surface, deform the trajectories of electrons forming the image. This leads to a distortion of the emission electron microscopy image and a decrease of lateral resolution. We propose a test object, where the influence of microfields conditioned by contact potential differences is compensated by a specially shaped relief of the sample surface.
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  • 194
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    Vibration analysis of nanomechanical mass sensor using carbon nanotubes under axial tensile loads (2014)
    Springer
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    Publication Date: 2014-02-10
    Description: Carbon nanotubes (CNTs) are nanomaterials with many potential applications due to their excellent mechanical and physical properties. In this paper, we proposed that CNTs with clamped boundary condition under axial tensile loads were considered as CNT-based resonators. Moreover, the resonant frequencies and frequency shifts of the CNTs with attached mass were investigated based on two theoretical methods, which are Euler–Bernoulli beam theory and Rayleigh’s energy method. Using the present methods, we analyzed and discussed the effects of the aspect ratio, the concentrated mass and the axial force on the resonant frequency of the CNTs. The results indicate that the length of CNTs could be easily changed and could provide higher sensitivity as nanomechanical mass sensor. Moreover, the resonant frequency shifts of the CNT resonator increase significantly with increasing tensile load acting on the CNTs.
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  • 195
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    Intelligent Selection of Machining Parameters in Multipass Turnings Using Firefly Algorithm (2014)
    Hindawi
    Details
    Publication Date: 2014-02-10
    Description: Determination of optimal cutting parameters is one of the most important elements in any process planning of metal parts. In this paper, a new optimization technique, firefly algorithm, is used for determining the machining parameters in a multipass turning operation model. The objective considered is minimization of production cost under a set of machining constraints. The optimization is carried out using firefly algorithm. An application example is presented and solved to illustrate the effectiveness of the presented algorithm.
    Print ISSN: 1687-5591
    Electronic ISSN: 1687-5605
    Topics: Computer Science , Technology
    Published by Hindawi
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  • 196
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    Investigation of electrical properties of HfO 2 metal–insulator–metal (MIM) devices (2014)
    Springer
    Details
    Publication Date: 2014-02-12
    Description: This paper is devoted to the study of the electrical properties of Au/HfO 2 /TiN metal–insulator–metal (MIM) capacitors in three distinctive modes: (1) alternative mode ( C – f ), (2) dynamic regime [thermally stimulated currents, TSCs I ( T )] and (3) static mode [ I ( V )]. The electrical parameters are investigated for different temperatures. It is found that capacitance frequency C – f characteristic possesses a low-frequency dispersion that arises for high temperature ( T  〉 300 °C). Accordingly, the loss factor exhibits a dielectric relaxation (with an activation energy E a  ~ 1.13 eV) which is intrinsically related to the diffusion of oxygen vacancies. The relaxation mechanisms of electrical defects in a dynamic regime (TSCs) analysis show that defect related to the TSC peak observed at 148.5 °C ( E a  ~ 1 eV) is in agreement with impedance spectroscopy ( C – f ). On the other hand, when the MIM structures are analyzed in static mode, the I – V plots are governed by Schottky emission. The extrapolation of the curve at zero field gives a barrier height of 1.7 eV.
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  • 197
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    Platinum–nickel alloy catalysts for fuel elements (2014)
    Springer
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    Publication Date: 2014-02-12
    Description: Within the framework of the methods of the electron density functional and the ab initio pseudopotential, the spatial distributions of density of valence electrons and the electron energy spectra were obtained for platinum-based films with supplement atoms of the second metal, action of mechanical stress and oxygen atoms. The most critical factors for increase of the catalyst activity during oxidization of methanol are mechanical stress and dissociated oxygen.
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  • 198
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    Effect of nano clay platelets and DNA on controlling the H-dimer of oxazine 4 perchlorate (OX4) in LbL film (2014)
    Springer
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    Publication Date: 2014-02-12
    Description: Oxazine 4 perchlorate (OX4) forms dimer even in aqueous solution. In layer-by-layer (LbL) film of OX4, dimeric sites predominate over monomeric sites. This results in the quenching of fluorescence intensity. This communication reports a study of the control of H-dimer of OX4 in LbL film by incorporating nano clay platelets. Influence of deoxyribonucleic acid molecules in controlling the H-dimeric sites of Ox4 in the LbL film has also been studied. UV–Vis absorption spectroscopic technique has been employed to study this effect. Atomic force microscopic image confirms the presence of nano clay platelets in the LbL film.
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  • 199
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    Optimal Tuning of Decentralized PI Controller of Nonlinear Multivariable Process Using Archival Based Multiobjective Particle Swarm Optimization (2014)
    Hindawi
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    Publication Date: 2014-02-13
    Description: A Multiobjective Particle Swarm Optimization (MOPSO) algorithm is proposed to fine-tune the baseline PI controller parameters of Alstom gasifier. The existing baseline PI controller is not able to meet the performance requirements of Alstom gasifier for sinusoidal pressure disturbance at 0% load. This is considered the major drawback of controller design. A best optimal solution for Alstom gasifier is obtained from a set of nondominated solutions using MOPSO algorithm. Performance of gasifier is investigated at all load conditions. The controller with optimized controller parameters meets all the performance requirements at 0%, 50%, and 100% load conditions. The investigations are also extended for variations in coal quality, which shows an improved stability of the gasifier over a wide range of coal quality variations.
    Print ISSN: 1687-5591
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  • 200
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    IEEE/ASME Transactions on Mechatronics information for authors (2014)
    Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
    Details
    Publication Date: 2014-02-22
    Print ISSN: 1083-4435
    Electronic ISSN: 1941-014X
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Published by Institute of Electrical and Electronics Engineers (IEEE) ; American Society of Mechanical Engineers (ASME)
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