UNI-Copter: A portable single-rotor-powered spherical unmanned aerial vehicle (UAV) with an easy-to-assemble and flexible structure

Journal of Mechanical Science and Technology - This paper presents the design and modeling of the UNI-Copter, a portable spherical unmanned aerial vehicle (UAV) that is powered by a single rotor....     

Stable pairwise time synchronization in the application layer for capillary machine-to-machine networks

This paper presents the design and performance evaluation of a stable pairwise time synchronization protocol (abbreviated SPS) for capillary machine-to-machine (M2M) networks that provides underlying platform independence and operational stability, even under harsh conditions. SPS achieves the first criterion using a novel technique whereby the M2M device captures incoming or outgoing moments of timing messages. The second criterion is achieved by adaptively adjusting the resynchronization interval. Extensive simulations are conducted to demonstrate the validity and effectiveness of SPS.     

An improved space-vector-based hysteresis current controller

In this paper, an improved space-vector-based hysteresis current controller (SVBHCC) is proposed. The controller determines a set of space vectors from a region detector and applies a space voltage vector selected according to the main HCC. A set of space vectors including the zero voltage vector to reduce the number of switchings is determined from the information of the current errors, which are wider than those of the main HCC. A simple hardware implementation is proposed and the good experimental results of the SVBHCC for a squirrel cage motor are also shown     

A method of compliance control of redundant manipulators

A compliance control method of redundant manipulators is presented. This method is based on the new stiffness model, which allows to modulate accarate joint stiffness of realizing the end effector stiffness to be varied with task requirements. A control model is developed and implemented by the proposed method in a three degree of freedom planar redundant manipulator. Also its effectiveness is validated.     

Control of voice coil motor nanoscanners for an atomic force microscopy system using a loop shaping technique

The voice coil motor nanoscanner has the advantages of large working range, easy control, and low cost compared to the conventional lead zirconate titanate driven nanoscanner. However, it has a small damping problem which causes mechanical vibration. The mechanical vibration reduces the accuracy as well as servobandwidth, which deteoriates the atomic force microscopy (AFM) image of the samples. In order to solve the vibration problem, the loop shaping technique [for vertical (z)] and input prefilter [for lateral (xy)] are applied. Experimental results of the proposed techniques are presented for vertical (z) and lateral (xy) scanner. Finally, the AFM images are provided to investigate its effect.     

A line-voltage-sensorless synchronous rectifier

A line-voltage-sensorless control for three-phase pulsewidth-modulated (PWM) synchronous rectifiers is presented. A line synchronization and unity power factor control are described. Indirect synchronization without sensing the line voltage allows a standard vector-controlled inverter to be used as a synchronous rectifier without requiring any additional hardware. Furthermore, the line synchronization can be properly operated under line voltage distortion or notching and line frequency variation. All control functions are implemented with a single-chip microcontroller. It is shown via experimental results that the proposed controller gives good performance for the synchronous rectifier     

Simulation of Ca2+-activated Cl- current of cardiomyocytes in rabbit pulmonary vein: implications of subsarcolemmal Ca2+ dynamics

In recent studies, we recorded transiently activated outward currents by the application of three-step voltage pulses to induce a reverse mode of Na+-Ca2+ exchange (NCX). We found that these currents were mediated by a Ca2+-activated Cl- current. Based on the recent reports describing the atrial Ca2+ transients, the Ca2+ transient at the subsarcolemmal space was initiated and then diffused into the cytosolic space. Because the myocardium in the pulmonary vein is an extension of the atrium, the Ca2+-activated Cl- current may reflect the subsarcolemmal Ca2+ dynamics. We tried to predict the subsarcolemmal Ca2+ dynamics by simulating these current traces. According to recent reports on the geometry of atrial myocytes, we assumed that there were three compartments of sarcoplasmic reticulum (SR): a network SR, a junctional SR and a central SR. Based on these structures, we also divided the cytosolic space into three compartments: the junctional, subsarcolemmal and cytosolic spaces. Geometry information and cellular capacitance suggested that there were essentially no T-tubules in these cells. The basic physical data, such as the compartmental volumes, the diffusion coefficients and the stability coefficients of the Ca2+ buffers, were obtained from the literature. In the simulation, we incorporated the NCX, the L-type Ca2+ channel, the rapid activating outward rectifier K+ channel, the Na+-K+ pump, the SR Ca2+-pump, the ryanodine receptor, the Ca2+-activated Cl- channel and the dynamics of Na+, K+, Ca2+ and Cl-. In these conditions, we could successfully reconstruct the Ca2+-activated Cl- currents. The simulation allowed estimation of the Ca2+ dynamics of each compartment and the distribution of the Ca2+-activated Cl- channel and the NCX in the sarcolemma on the junctional or subsarcolemmal space.     

Preparation of gradient polyacrylate brushes in microchannels

Gradient poly(2-hydroxyethyl methacrylate) brushes were synthesized by surface-initiated atom transfer radical polymerization (ATRP) confined within a microfluidic system on a silicon wafer. For ATRP, surface initiator, 11-((2-bromo, 2-methyl) propionyloxy) undecyltrichlorosilane (BUC), was synthesized, and allowed to self-assemble in a monolayer on the Si wafer, as analyzed by XPS to confirm the presence of an ester group of BUC. A solution containing 2-hydroxyethylmethacrylate, Cu catalyst, and bipyridin was allowed to flow in a microchannel and polymerize, resulting in the brushes with a gradient of thickness on the Si wafer. Using ellipsometry and ATR-IR, we verified the gradients of well established brushes on the Si wafer. AFM and contact angle data showed that wettability of the brushes did not exhibit a linear relationship with hydrophilicity.     

Fabrication and properties of macro-porous SiC using Al2O3–Y2O3–SiO2 as bonding additives

Macro-porous SiC was fabricated without using pore-forming agents by an in situ reaction bonding process. A bonding additive, Al₂O₃–Y₂O₃–SiO₂, with a low melting temperature was mixed with SiC particles and sintered at 1500 °C and 1600 °C for 1 h in Ar. Macro-porous SiC with a porosity of 32.7–45.9%, a pore size of 3.4–4.2 μm, and a relatively narrow and uniform pore size distribution was fabricated by varying the amount of bonding additive. The flexural strength of macro-porous SiC prepared at 1500 °C increased from 47.2 MPa to 71.2 MPa while the porosity decreased from 45.9% to 42.8%, respectively. When the sintering temperature of the macro-porous SiC was increased to 1600 °C, the flexural strengths were significantly reduced to 32.6–35.6 MPa, along with a reduction in porosity and pore size. The permeability of macro-porous SiC prepared at 1500 °C varied from 1.59 × 10^?12 m² to 1.26 × 10^?12 m², depending on the porosity. As the sintering temperature increased from 1500 °C to 1600 °C, the permeability decreased to less than 1.00 × 10^?12 m² because of the reduced porosity and average pore size. The electrical resistivity of macro-porous SiC prepared at 1500 °C and 1600 °C varied from 2.7 × 10⁸ Ω-cm to 1.4 × 10⁹ Ω-cm and from 1.3 × 10⁸ Ω-cm to 1.7 × 10⁹ Ω-cm, respectively, with increasing volume percent of bonding additives. The relatively high electrical resistivity was apparently due to neck bonding phase between SiC particles formed by phases consisting of Y₂Si₂O₇, YAG, and residual Al₂O₃.