Dielectric and piezoelectric properties of [0 0 1] and [0 1 1]-poled relaxor ferroelectric PZN–PT and PMN–PT single crystals

The properties of PZN–PT and PMN–PT single crystals of varying compositions and orientations have been investigated. Among the various compositions studied, [0 0 1]-optimally poled PZN-(6–7)%PT and PMN-30%PT exhibit superior dielectric and piezoelectric properties, with K^T ≈ 6800–8000, d₃₃ ≈ 2800 pC/N, d₃₁ ≈ −(1200–1800) pC/N for PZN-(6–7)%PT; and K^T = 7500–9000, d₃₃ = 2200–2500 pC/N and d₃₁ = −(1100–1400) pC/N for PMN-30%PT. These two compositions are also fairly resistant to over-poling. The [0 0 1]-poled electromechanical coupling factors (k₃₃, k₃₁ and k_t) are relatively insensitive to crystal composition. [0 1 1]-optimally poled PZN-7%PT single crystal also exhibits extremely high d₃₁ values of up to −4000 pC/N with k₃₁ ≈ 0.90–0.96. While [0 1 1]-poled PZN-7%PT single crystal becomes over-poled with much degraded properties when poled at and above 0.6 kV/mm, PZN-6%PT crystal shows no signs of over-poling even when poled to 2.0 kV/mm. The presence of a certain amount (i.e., 10–15%) of orthorhombic phase in a rhombohedral matrix has been found to be responsible for the superior transverse piezoelectric properties of [0 1 1]-optimally poled PZN-(6–7)%PT. The present work shows that flux-grown PZN–PT crystals exhibit superior and consistent properties and improved over-poling resistance to flux-grown PMN–PT crystals and that, for or a given crystal composition, flux-grown PMN–PT crystals exhibit superior over-poling resistance to their melt-grown counterparts.     

A 5 GHz LC-VCO frequency synthesizer for unlicensed band of WiMAX

This paper presents a low power and low phase noise CMOS integer-N frequency synthesizer based on the charge-pump Phase Locked Loop (PLL) topology. The frequency synthesizer can be used for IEEE 802.16 unlicensed band of WiMAX (World Interoperability for Microwave Access). The operation frequency of the proposed design is ranged from 5.13 to 5.22 GHz. The proposed Voltage-Controlled Oscillator (VCO) achieves low power consumption and low phase noise. The high speed divider is implemented by an optimal extended true single phase clock (E-TSPC) prescaler. It can achieve higher operating frequency and lower power consumption. A new frequency divider is also proposed to eliminate the hardware overhead of the S counter in the conventional programmable divider. The proposed frequency synthesizer consists of a phase-frequency detector (PFD), a charge pump, a low-pass loop filter, a VCO, and a frequency divider. The simulated phase noise of the proposed VCO is −121.6 dBc/Hz at 1 MHz offset from the carrier frequency. The proposed frequency synthesizer consumes 13.1 mW. The chip with an area of 1.048 × 1.076 mm² is fabricated in a TSMC 0.18 μm CMOS 1P6M technology process.     

Phase equilibria in the Ge-Mn-Ti ternary system at 973 K, 1073 K and 1173 K

Phase relationships in the Ge-Mn-Ti ternary system have been studied through alloy samples approach. Assisted with Electron Probe Microanalysis (EPMA) and X-ray diffraction (XRD) techniques, isothermal sections at 973 K, 1073 K and 1173 K of this system were constructed and existence of 2 ternary phases, i.e. GeMnTi and Ge₂MnTi, were confirmed. In addition, remarkable ternary solubilities in some binary compounds were detected, e.g. Ge in Mn₂Ti and Mn in Ge₅Ti₆ can be up to 15 at% and 50 at% at 1173 K, respectively. Furthermore, the substitution of Ti by Mn atoms in Ge₅Ti₆ was confirmed with Rietveld refinement results of solid solutions, Ge₅(Mn_0.30Ti_0.70)₆ and Ge₅(Mn_0.67Ti_0.33)₆.     

Solutions to the functional equation I(x, y) = I(x, I(x, y)) for three types of fuzzy implications derived from uninorms

This paper investigates an iterative Boolean-like law with fuzzy implications derived from uninorms. More precisely, we characterize the solutions to the functional equation I(x, y) = I(x, I(x, y)) that involve RU-, (U, N)- and QLU-implications generated by the most usual classes of uninorms.     

Growth and electrical properties of highly (0 0 1)-oriented Pb(Zr0.52Ti0.48)O3 thin films on amorphous TiN buffered Si(1 0 0)

Pb(Zr_0.52Ti_0.48)O₃ (PZT) ferroelectric thin films with LaNiO₃ (LNO) as bottom electrodes have been grown on amorphous TiN buffered Si(1 0 0) substrates by pulsed laser deposition. It was found that highly (0 0 1)-oriented LNO films could be obtained even if TiN underlayers were amorphous. XRD analyses showed that the subsequently deposited PZT films were also preferentially (0 0 1)-oriented due to the template effect of the perovskite structured LNO films. Dielectric constant of the PZT thin films remained almost constant with frequency in the range from 10³ to 10⁶ Hz, and tangent loss was as small as 0.02 at high frequencies. The remnant polarization and coercive field of an Au/PZT/LNO capacitor were typically 20 μC/cm² and 30 kV/cm, respectively. C–V and I–V characteristics revealed the capacitance and leakage current variations with applied voltage were asymmetric when the bottom electrode was negatively as well as positively biased, indicating that ferroelectric/electrode interfaces and space charges play an important role in the electrical properties of ferroelectric capacitors.     

Design,fabrication, and testing of MEMS solid propellant thruster array chip on glass wafer

This paper presents the internal ballistic design, fabrication procedure, and performance evaluation of a micro-electro mechanical systems (MEMS) solid propellant thruster array chip. The internal ballistic design was carried out to predict the performance of the thruster. Two different ignition models were used. The numerical results gave a maximum thrust of 3840 mN, and a total impulse of 0.42 mNs at the local ignition model. A photosensitive glass wafer only was used as the bare material for the thruster. The stability of the micro-igniter was improved by using a glass membrane with a thickness of tens of microns. The average thickness of the membrane was 35 μm. The proposed micro-igniter had a level of power consumption appropriate to ignite the solid propellant. The thermal, electrical, and mechanical characteristics of the fabricated micro-igniter were measured. The solid propellant was loaded into the propellant chamber without resort to a special technique due to the high structural stability of the glass membrane. An MEMS solid propellant thruster (MSPT) array was fabricated through anisotropic etching of photosensitive glass. An ignition control system was developed to control the ignition sequence. Ignition and combustion tests of the fully assembly MEMS thruster were performed successfully. The minimum ignition delay was 27.5 ms with an ignition energy of 19.3 mJ. The average of the measured maximum thrust and total impulse were 3619 mN and 0.381 mNs, respectively.     

Design,fabrication and vacuum operation characteristics of two-dimensional comb-drive micro-scanner

We present design, fabrication, and characteristics of two-dimensional micro-machined comb-drive scanner to operate in vacuum. The scanner can be actuated in two orthogonal axes using the slanted electrostatic comb-drive and silicon conductive V-shaped torsion hinges fabricated from a silicon-on-insulator wafer. The resonant frequencies of the inner mirror and the gimbal frame are 40 kHz and 162 Hz, respectively. The resonant frequency ratio is 247. The optical scanning angles for the inner mirror and the gimbal frame are 11.5° and 14° at the operation voltages of 12 and 10 V in 1 Pa vacuum, respectively. These driving voltages are smaller by the factors of about 21 and 3 than those in atmosphere, respectively. The dependence of quality factor on pressure for the inner mirror and the gimbal frame is also experimentally investigated and compared with the theoretical calculation based on air-friction models.     

Detailed check of the LDA + U and GGA + U corrected method for defect calculations in wurtzite ZnO

Based on a detailed check of the LDA + U and GGA + U corrected methods, we found that the transition energy levels depend almost linearly on the effective U parameter. GGA + U seems to be better than LDA + U, with effective U parameter of about 5.0 eV. However, though the results between LDA and GGA are very different before correction, the corrected transition energy levels spread less than 0.3 eV. These more or less consistent results indicate the necessity and validity of LDA + U and GGA + U correction.     

Kinematic and dynamic identification of parallel mechanisms

In this paper, we provide a comprehensive method to perform the physical model identification of parallel mechanisms. This includes both the kinematic identification using vision and the identification of the dynamic parameters. A careful attention is given to the issues of identifiability and excitation. Experimental results obtained on a H4 parallel robot show that kinematic identification yields an improvement in the static positioning accuracy from some 1 cm down to 1 mm, and that dynamic parameters are globally estimated with less than 10% relative error yielding a similar error on the control torque estimation.     

Cationic P⋯N interaction in XH3P+⋯NCY complexes (X = H,F, CN,NH2, OH; Y = H,Li, F,Cl) and its cooperativity with hydrogen/lithium/halogen bond

The geometries, interaction energies and bonding properties of cationic pnicogen bond (CPB) interactions are studied in binary XH₃P⁺⋯NCY (X = H, F, CN, NH₂, OH; Y = H, Li, F, Cl) complexes by means of MP2/aug-cc-pVTZ calculations. Interaction energies of these binary complexes span a large range, from −16.36 kcal/mol in (NH₂)H₃P⁺⋯NCF to −71.36 kcal/mol in FH₃P⁺⋯NCLi complex. The spin–spin coupling constant across P⋯N interaction depends considerably on the nature of X and Y substituents. The characteristic of CPB interactions is analyzed in terms of parameters derived from quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. The charge transfer from the nitrogen base to the cationic acid stabilizes these pnicogen–bonded complexes. For a given XH₃P⁺, the net charge transfer value increases as the interaction energy of the complex becomes more negative, i.e., NCLi > NCCl > NCH > NCF. Moreover, mutual influence between the CPB and hydrogen/halogen/lithium bond is studied in the ternary XH₃P⁺⋯NCY⋯NCH complexes. The results indicate that the formation of a Y⋯N interaction tends to strengthen CPB in the ternary systems.     

Angular vertical comb actuators assembled on-chip using in-plane electrothermal actuators and latching mechanisms

We have designed, fabricated and tested self-aligned angular vertical comb-drive (AVC) actuators by on-chip assembly using in-plane electrothermal actuators and latching mechanisms. The on-chip assembly process is carried out by engaging latching mechanism connected to the torsion bars through the off-centered thinned down silicon beams. When the latching mechanism is fully engaged, the assembled AVC actuator forms permanent initial tilt angle by the retraction force of electrothermal actuators. The AVC actuators and latching mechanisms are fabricated on a silicon-on-insulator (SOI) wafer using three photomasks and three times of deep etch steps. The maximum optical scan angle of 30.7° is achieved at 4.56 kHz under the sinusoidal driving voltage of 0–80 V applied to the AVC actuator. After the reliability test performed by operating the actuator for 1.6 × 10⁸ cycles at its resonance, the measured optical scan angle variation and resonant frequency change were within 1.1% and 8 Hz, respectively, and the robustness of the latched mechanism was ensured.     

Mechanical design and characterization of a resonant magnetic field microsensor with linear response and high resolution

A resonant magnetic field microsensor based on Microelectromechanical Systems (MEMS) technology including a piezoresistive detection system has been designed, fabricated, and characterized. The mechanical design for the microsensor includes a symmetrical resonant structure integrated into a seesaw rectangular loop (700 μm × 450 μm) of 5 μm thick silicon beams. An analytical model for estimating the first resonant frequency and deflections of the resonant structure by means of Rayleigh and Macaulay's methods is developed. The microsensor exploits the Lorentz force and presents a linear response in the weak magnetic field range (40–2000 μT). It has a resonant frequency of 22.99 kHz, a sensitivity of 1.94 V T^?1, a quality factor of 96.6 at atmospheric pressure, and a resolution close to 43 nT for a frequency difference of 1 Hz. In addition, the microsensor has a compact structure, requires simple signal processing, has low power consumption (16 mW), as well as an uncomplicated fabrication process. This microsensor could be useful in applications such as the automotive sector, the telecommunications industry, in consumer electronic products, and in some medical applications.     

Experimental blood glucose interval identification of patients with type 1 diabetes

Many problems are confronted when characterizing a type 1 diabetic patient such as model mismatches, noisy inputs, measurement errors and huge variability in the glucose profiles. In this work we introduce a new identification method based on interval analysis where variability and model imprecisions are represented by an interval model as parametric uncertainty.The minimization of a composite cost index comprising: (1) the glucose envelope width predicted by the interval model, and (2) a Hausdorff-distance-based prediction error with respect to the envelope, is proposed. The method is evaluated with clinical data consisting in insulin and blood glucose reference measurements from 12 patients for four different lunchtime postprandial periods each.Following a “leave-one-day-out” cross-validation study, model prediction capabilities for validation days were encouraging (medians of: relative error = 5.45%, samples predicted = 57%, prediction width = 79.1 mg/dL). The consideration of the days with maximum patient variability represented as identification days, resulted in improved prediction capabilities for the identified model (medians of: relative error = 0.03%, samples predicted = 96.8%, prediction width = 101.3 mg/dL). Feasibility of interval models identification in the context of type 1 diabetes was demonstrated.     

Passive single chip wireless microwave pressure sensor

A novel micromachined passive wireless pressure sensor is presented. The device consists of a tuned circuit operating at 10 GHz fabricated on to a SiO₂ membrane, supported on a silicon wafer. A pressure difference across the membrane causes it to deflect so that an antenna circuit detunes. The circuit is remotely interrogated to read off the sensor data wirelessly. The chip area is 5 mm × 4 mm and the membrane area is 2 mm² with a thickness of 4 μm. Two on-chip passive resonant circuits were investigated: a meandered dipole and a zigzag antenna. Both have a physical length of 4.25 mm. The sensors show a shift in their resonant frequency in response to changing pressure of 10.28–10.27 GHz for the meandered dipole, and 9.61–9.58 GHz for the zigzag antenna. The sensitivities of the meandered dipole and zigzag sensors are 12.5 kHz/mbar and 16 kHz/mbar respectively.     

The effects of 0.2 Hz varying latency with 20–100 ms varying amplitude on simulator sickness in a helmet mounted display

The relationship between the occurrence of simulator sickness (SS) and varying latency in a helmet-mounted display (HMD) was explored in this study. Previous work has always considered latency to be a constant. The aim of this research was to determine if a latency that varied over time would impact the experience of SS for HMD users. An object location task was used while viewing real, live video scenes via HMD. A planned comparisons approach was utilized with four experimental conditions, 2 of them having constant latency (0 ms added to system baseline, 200 ms added to system baseline) and 2 of them having sinusoidally varying latency (100 ms amplitude at 0.2 Hz frequency, and 20–100 ms varying amplitude at 0.2 Hz frequency). These conditions allowed for the assessment of the effects of constant latency vs. varying latency on the experience of SS. The results indicated that a varying latency is associated with greater experience of SS among HMD users than constant latency. Results also indicated, as has other recent research, that added constant latency on its own does not appear to be associated with the experience of higher levels of SS in an HMD.     

Hybrid wireless sensor network for building energy management systems based on the 2.4 GHz and 400 MHz bands

In this paper, a hybrid wireless sensor network (WSN) system is considered and implemented for the building energy management systems. Characteristics of the radios, which are based on the 2.4 GHz and 400 MHz bands, respectively, are analyzed for the building environments. For battery-operated portable sensors, narrow-bandwidth radios of the 400 MHz band are employed in a star connection between their parent nodes. Between the parent nodes, a mesh network is constructed for an efficient and fast data transmission based on the wide-bandwidth radios of the 2.4 GHz band. The hybrid WSN system is implemented and tested for a building environment and provides a reliable wireless communication link for gathering sensing data.     

Phase equilibria in Fe–Sn–Ti ternary system at 1073 K and 1273 K

Phase equilibria in the Fe–Sn–Ti ternary system at 1073 and 1273 K were experimentally investigated through alloy sampling approach facilitated with electron probe micro-analyzer and X-ray diffraction. Two ternary compounds TiFe₂Sn and Ti₂FeSn were detected. Ten 3-phase equilibria at 1073 K, including β(Ti)+Ti₃Sn+FeTi, Ti₃Sn+FeTi+Ti₅Sn₃, FeTi+Ti₅Sn₃+Ti₂FeSn, Ti₂FeSn+Fe₂Ti+TiFe₂Sn, Ti₂FeSn+Ti₅Sn₃+Ti₆Sn₅, FeTi+Fe₂Ti+Ti₂FeSn, Ti₂FeSn+Ti₆Sn₅+TiFe₂Sn, TiFe₂Sn+Ti₆Sn₅+Liquid, TiFe₂Sn+Fe₅Sn₃+Liquid and α(Fe)+Fe₂Ti+TiFe₂Sn, and seven 3-phase equilibria including β(Ti)+Ti₃Sn+FeTi, Ti₃Sn+FeTi+Ti₅Sn₃, Ti₃Sn+Ti₂Sn+Ti₅Sn₃, FeTi+Fe₂Ti+Ti₅Sn₃, Fe₂Ti+Ti₂FeSn+Ti₅Sn₃, Ti₂FeSn+Fe₂Ti+TiFe₂Sn and Ti₂FeSn+Ti₆Sn₅+TiFe₂Sn at 1273 K were experimentally confirmed. At 1073 K, the homogeneity ranges of Ti₂FeSn were 45.5–51.4 at% Ti and 24–27.7 at.% Sn while TiFe₂Sn exhibited a large homogeneity range of 46.9–66.4 at% Fe and 22.7–26.4 at% Sn, the solubility of Sn in Fe₂Ti,Fe in Ti₅Sn₃, Ti in Fe₅Sn₃ and Fe in Ti₆Sn₅ can be up to 4.6 at.%, 10.2 at%, 3.7 at% and 21 at%, respectively, while at 1273 K, Solubility of Sn in Fe₂Ti considerably increased to 10.8 at%, Fe in Ti₅Sn₃ changes little. According to the measured phase relations, an invariant reaction was further deduced, which was Fe₂Ti+Ti₅Sn₃↔FeTi+Ti₂FeSn occurring between 1073 K and 1123 K.     

Development of a slender continuum robotic system for on-wing inspection/repair of gas turbine engines

The maintenance works (e.g. inspection, repair) of aero-engines while still attached on the airframes requires a desirable approach since this can significantly shorten both the time and cost of such interventions as the aerospace industry commonly operates based on the generic concept “power by the hour”. However, navigating and performing a multi-axis movement of an end-effector in a very constrained environment such as gas turbine engines is a challenging task. This paper reports on the development of a highly flexible slender (i.e. low diameter-to-length ratios) continuum robot of 25 degrees of freedom capable to uncoil from a drum to provide the feeding motion needed to navigate into crammed environments and then perform, with its last 6 DoF, complex trajectories with a camera equipped machining end-effector for allowing in-situ interventions at a low-pressure compressor of a gas turbine engine. This continuum robot is a compact system and presents a set of innovative mechatronics solutions such as: (i) twin commanding cables to minimise the number of actuators; (ii) twin compliant joints to enable large bending angles (±90°) arranged on a tapered structure (start from 40 mm to 13 mm at its end); (iii) feeding motion provided by a rotating drum for coiling/uncoiling the continuum robot; (iv) machining end-effector equipped with vision system. To be able to achieve the in-situ maintenance tasks, a set of innovative control algorithms to enable the navigation and end-effector path generation have been developed and implemented. Finally, the continuum robot has been tested both for navigation and movement of the end-effector against a specified target within a gas turbine engine mock-up proving that: (i) max. deviations in navigation from the desired path (1000 mm length with bends between 45° and 90°) are ±10 mm; (ii) max. errors in positioning the end-effector against a target situated at the end of navigation path is 1 mm. Thus, this paper presents a compact continuum robot that could be considered as a step forward in providing aero-engine manufacturers with a solution to perform complex tasks in an invasive manner.