Pre-annealing effect of electroless Ni−B deposit as a diffusion barrier for electroplated Cu electrodes

Ni−B film of 1 μm thickness was electrolessly deposited on an electroplated Cu bus electrode. The film, which encapsulates the Cu bus electrodes, prevents Cu oxidation and serves as a diffusion barrier against Cu contamination of the transparent dielectric layer in a plasma display during the firing process at 580 °C. The microstructure of theas-deposited barrier film was amorphous phase and crystallized to Ni and Ni₃B after annealing at 300 °C. The good barrier properties observed here can be explained by Ni₃B precipitates at the grain boundaries acting as a fast diffusion path via pre-annealing at 300 °C before the firing process at 580 °C.     

Thermal stability and electric properties of Ba0.7Sr0.3TiO3 parallel plate capacitor with nano-Cr interlayer

A novel sandwich structure of Ba_0.7Sr_0.3TiO₃/Cr/Ba_0.7Sr_0.3TiO₃ (BST/Cr/BST) was sputtered onto Pt/Ti/SiO₂/Si substrate. With the insertion of a Cr layer, the leakage currents are decreased and the thermal stability of the specimens is enhanced. Temperature coefficient of capacitance (TCC) of specimens with BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms can achieve about 83% lower than those with BST (400 nm) monolayer. However, the dielectric constant of the BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms decreases to about 37% of that BST monolayer. The leakage current densities under an electric field of 125 kV/cm at 90 °C are 4 × 10^− 4 A/cm² and 9 × 10^− 1 A/cm² for BST (200 nm)/Cr (2 nm)/BST (200 nm) and monolayer BST (400 nm), respectively. X-ray diffraction results indicate the formation of a CrO₃ secondary phase after annealing at 700 °C or above in O₂ atmosphere. The root causes for the improvement of leakage currents and thermal stability with the insertion of nano-Cr interlayer are explored. The results show the insertion of Cr-nanolayer improves the electric properties for application in capacitors.     

Sensorless permanent-magnet synchronous motor drive using a reduced-order rotor flux observer

A sensorless permanent-magnet synchronous motor (PMSM) drive is developed. A second-order Luenberger observer is used to estimate the position of the rotor flux and hence the rotor speed. The observer is computationally efficient as it has a simple structure and does not involve mechanical parameters. An integral-feedback method is adopted for the estimation of the rotor speed. The inner current loop is realised using a decoupling and diagonal internal model control algorithm. Details of the sensorless control system are given and the feasibility of the proposed method is verified through simulation and experiments. Satisfactory estimation accuracy is obtained even when the drive operates at very low speeds and also during rotor speed reversals.     

Reciprocal influences in children's and families' adaptation to early childhood wheezing.

Objective: The objective of the present study was to demonstrate the reciprocal relationships between family adaptation to illness and children's medication use over time among children who presented with wheezing illness in infancy but have varying illness outcomes by age 4. Design: A longitudinal design and latent growth curve models (LGM) were used to predict change in family and caregiver adaptation to illness and children's medication use over three years among 140 infants with wheezing, among families from low socioeconomic, multi-ethnic backgrounds. Main Outcome Measures: One LGM predicted level and change (slope) of family adaptation to illness from children's baseline medication use. The second LGM predicted level and change (slope) of children's medication use from baseline family adjustment to illness. In both models, illness severity, caregivers' psychological resources, and emergency department use were covaried with the independent variable. Results: Two latent growth models were found to adequately fit the data and demonstrate full reciprocal relations between family adaptation to illness and children's medication use while accounting for baseline variables. Baseline measures of caregiver psychological functioning and illness severity were also significant predictors of family adaptation and children's medication use over time. The two models were not statistically different for children with and without active asthma at 4 years of age. Conclusion: Findings support the reciprocal effects model of child and family influences on pediatric illness and underscore the importance of early indicators of individual and family functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychological resilience and dysfunction among hospitalized survivors of the SARS epidemic in Hong Kong: A latent class approach.

Objective: To examine trajectories of psychological functioning using latent class analysis on a sample of hospitalized survivors of the 2003 severe acute respiratory syndrome (SARS) epidemic in Hong Kong. Design: A longitudinal study of 997 survivors, recruited from among 1,331 individuals hospitalized for SARS, were interviewed at 6, 12, and 18 months after hospitalization. Main Outcome Measures: Psychological and physical functioning at each time point was measured using the 12-item Medical Outcome Study Short-Form Health Survey (SF-12). Results: Four latent classes were identified-chronic dysfunction, delayed dysfunction, recovery, and resilience. All groups had better physical health than the chronic group. Resilient and recovered individuals had greater social support and less SARS-related worry, and resilient individuals were more likely to be male. The resilient group also had greater social support than the delayed group and better physical functioning than the recovered group. Conclusion: This study demonstrated that longitudinal outcome trajectories following a major health-threat event in an Asian sample bear close resemblance to prototypical trajectories observed in trauma studies using Western samples. Unique predictors of the trajectories included factors observed in previous studies, such as social support, as well as factors of particular relevance to a major disease outbreak, such as SARS-related worry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of Steady Horseshoe Vortex System near Junction of Square Cylinder and Base Plate

This paper presents an experimental investigation on the characteristics of a horseshoe vortex system near the juncture of a square cylinder and a horizontal base plate, using particle image velocimetry and flow visualization technique. Experiments were conducted for Reynolds numbers (based on the free stream velocity and the width of square cylinder) ranging from 2.0×102 to 6.0×103. The flow patterns are first classified into four major regimes: Steady horseshoe vortex system, periodic oscillation vortex system with small displacement, periodic breakaway vortex system, and irregular vortex system. The classifications can be demonstrated as a figure of Reynolds number versus the ratio of the height of square cylinder to undisturbed boundary layer thickness. The study then mainly focused on the characteristics of steady horseshoe vortex system (corresponding to Reynolds numbers ranging from 2.0×102 to 2.5×103). The nondimensional characteristics, including the horizontal and vertical distances from the primary vortex core to frontal face of the vertical square cylinder and bottom boundary of the base plate, respectively, the height of stagnation point at frontal face of the square cylinder, and the down-flow discharge as well as circulation of the primary vortex, all increase with increase of the ratio of the height of square cylinder to undisturbed boundary layer thickness. However, they all decrease with the increase of the aspect ratio (i.e., the height-to-width ratio) of the square cylinder. The study provides essential properties of a steady horseshoe vortex system and gives an insight for related engineering applications. It can be served as a basis for more complicated horseshoe vortex systems occurring at high Reynolds numbers.     

Oxidation Behavior of CuZr-Based Glassy Alloys at 400 °C to 500 °C in Dry Air

The oxidation behavior of the Cu_47.5Zr_47.5Al₅ (Cu3) and Cu₄₇Ti₃₄Zr₁₁Ni₈ (Cu4) bulk metallic glasses (BMGs) was studied over the temperature range of 400 °C to 500 °C in dry air. The oxidation kinetics of both alloys generally followed a multistage parabolic-rate law, and the steady-state parabolic-rate constants (k _p values) fluctuated with temperature for the Cu3 BMG, but increased with increasing temperature for the Cu4 BMG. The scales formed on the BMGs were strongly dependent on the temperature and alloy composition, and were composed primarily of tetragonal-ZrO₂ (t-ZrO₂) and minor amounts of Al₂O₃, Cu₂O, and CuO at 400 °C for the Cu3 BMG, while the monoclinic-ZrO₂ (m-ZrO₂) phase is present at T ≥ 425 °C, and the Cu₂O phase is absent at 500 °C. Conversely, the scales formed on the Cu4 BMG consisted exclusively of CuO at 400 °C, while minor amounts of t-ZrO₂, TiO₂, and ZrTiO₄ formed at 425 °C to 450 °C, and TiO was also detected at higher temperatures. It was found that both amorphous Cu3 and Cu4 substrates transformed into different crystalline phases, and were strongly dependent on temperature and duration of time. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred during the TMS Annual Meeting February 25–March 1, 2007, in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.     

Measurement of developing turbulent flow in a U-bend of circular cross-section

Hot-wire measurements of the full mapping of the velocity and Reynolds stress components are reported for developing turbulent flow in a strongly curved 180 deg pipe and its tangents. A slanted wire is rotated into 6 orientations and the voltage outputs from wires are combined to obtain the mean velocity and Reynolds stress components. The strength of secondary flow reaches up to the 28% of bulk mean velocity. The strong counter-rotating vortex pair induced by the transverse pressure gradient and centrifugal force imbalance grows up to Θ = 67.5° into the bend. But the vortex pair breaks down into two cell pattern after Θ=90° Core vortex formation and reversal of secondary flow direction along the bend symmetry plane is cleanly found in the secondary vector plot. At Θ=67.5° and Θ = 90° into bend a large “trough” develops in the longitudinal velocity toward the inside of the bend due to the breakdown of secondary flow. In the bend, the mean longitudinal velocity component changes little after Θ=90°, but secondary flow never achieves fully-developed state. Similar behaviors are observed in the radial and circumferential stresses.     

Effects of anodizing voltage on the anodized and hydrothermally treated titanium surface

Anodic oxidation is the process of creating a titanium oxide layer with various defects more dense and stable. In this study, a dense, stable and porous oxide layer was formed using anodic spark oxidation on pure titanium surface and hydroxyapatite crystals were formed on its surface via a hydrothermal treatment. A mixture of 0.02M−GP (Glycerolphosphate disodium salt) and 0.2M-CA (Calcium acetate) was used as an electrolyte. By increasing the anodizing voltage to 220, 260, 300, and 360 V, the effects of the anodizing voltage were examined by evaluating the film properties after anodization and a hydrothermal treatment. Breakdown occurred around 230 V. As the voltage increased after breakdown, the pore size increased. After the hydrothermal treatment, the amount of HA crystal precipitation was also increased as the voltage increased. The mean surface roughness (Ra) of the anodizing surface was also increased as the voltage increased. The Ra value was larger in the hydrothermally treated group compared with the group treated with anodization as a result of the HA crystals present on the surface after the hydrothermal treatment. Corrosion resistance of the surface modified by anodization was significantly increased in a saline solution compared to that for the non-treated group; this increased further after the hydrothermal treatment. These increases were most likely due to a thick stable oxide layer formed through anodization. Thus, it is believed that titanium with its surface modified through anodic spark oxidation would be a suitable biomaterial due to its corrosion resistance and biocompatibility.     

Simulations of the dielectric constant of bonding materials and field emission properties of CNT cathodes

The effect of the dielectric constant (k) of bonding materials in a screen-printed carbon nanotube (CNT) cathode on the field enhancement factor was investigated for high-efficiency CNT cathodes using the ANSYS software. The values obtained by a simulation study were compared to the experimental results obtained for screen-printed CNT cathodes. The field enhancement factor increased as the dielectric constant decreased, reaching a maximum value at a dielectric constant of 1, the value for a vacuum. The findings indicate that the larger sheet resistance of the bonding materials, after the firing process, can be attributed to the larger emission current of the CNT cathode. From these results, it was concluded that the best bonding materials for screen-printed CNT cathodes should have a low dielectric constant and a high sheet resistance. This finding can be used as criteria for selecting bonding materials for use in CNT pastes for highly efficient CNT cathodes.