Microwave and infrared dielectric response of tunable Ba1−xSrxTiO3 ceramics

The dielectric properties, infrared (IR) dielectric response and Raman spectra of tunable microwave (MW) Ba_1?xSr_xTiO₃ (x = 0.4, 0.5, 0.6 and 0.7) ceramics were studied systematically as functions of composition and temperature. It was found that, with increasing the content of Sr from 40% to 70%, the permittivity of the Ba_1?xSr_xTiO₃ ceramics decreased from 7200 to 640 while the dielectric tunability decreased from 50.1% to 5.4% measured at 10 kHz. It is particularly interesting that the MW dielectric loss tangent was significantly decreased from 1.5 × 10^?2 to 7.4 × 10^?4. Complex permittivity spectra obtained by fitting the infrared data were also extrapolated to MW frequency and compared with the dielectric data near 1 GHz. For the samples with x = 0.4 and x = 0.5, the dielectric loss measured at ～1 GHz was much higher than that calculated at 10 GHz, which is presumably due to the Debye-type dielectric relaxation in GHz region. However, the dielectric loss of the samples with x = 0.6 and x = 0.7, extrapolated from IR range, was in agreement with that measured at MW frequency. Low-temperature Raman scattering showed that the band at 760 cm^?1 assigned to the Ti?O₃ torsional mode markedly sharpens and shifts upward with increasing content of Sr. This is an indication that the bonding between cations and anions was tightened due to the substitution of Ba with Sr, which explains well the decrease in dielectric permittivity, loss and tunability with increasing concentration of Sr.     

High speed steel produced by spray forming

In this paper, ASP2030 (A30) high speed steel (HSS) was produced by spray forming and the microstructure was studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The spray formed A30 (SF A30) steel exhibited a very uniform and fine microstructure consisting of martensite, retained austenite and uniformly distributed network carbides. Microstructure refining can be explained in terms of the rapid solidification of spray forming. M₂C, MC and M₆C type carbides were found in the as-sprayed A30 HSS by XRD and TEM. A uniform distribution of carbides was obtained after forging and annealing. The microstructure properties of SF A30 steel indicate that spray forming can be considered as a cost-effective route for the production of A30 steels and other highly alloyed steels.     

Energy performance of residential buildings in Singapore

Energy consumption of buildings takes up about a third of Singapore's total electricity production. In this paper, we present a pioneering study to investigate the energy performance of residential buildings. Beginning with an energy survey of households, we established the air-conditioning usage patterns and modelled residential buildings for computer simulations. An ETTV equation for residential buildings was developed. Employing this equation, we demonstrated how to achieve improved energy efficiency in residential buildings. Two types of residential buildings, namely, point block and slab block, were modelled and parametric runs performed. ETTV impacts the energy consumption of residential buildings and thus lowering the ETTV will result in reduced building heat load. Results from the developed equation showed that a unit decrease in ETTV resulted in 4% and 3.5% reduction in annual cooling energy for point block and slab block residential buildings, respectively. In addition, a set of simple energy and load estimating equations were developed using computer simulation and local climatic data. These equations provided a means of estimating the annual cooling energy consumption of residential buildings in Singapore.     

Microstructure and Thickness of 55 pct Al-Zn-1.6 pct Si-0.2 pct RE Hot-Dip Coatings: Experiment, Thermodynamic, and First-Principles Study

The microstructure and thickness of 55 pct A1-Zn-1.6 pct Si-0.2 pct RE coatings during continuous hot-dip on Q235 steel were investigated in this work. The experimental results revealed that the intermetallic layer was composed of the Fe₂Al₅, FeAl₃, and α-FeAlSi phases. The results of thermodynamic calculations with Pandat software package (CompuTherm, LLC, Madison, WI) indicated that FeAl₃ and α(β)-FeAlSi phase precipitated during the period of temperature cooling, which was consistent with experimental result. Then, the thickness of intermetallic layer was characterized. It was shown that the thickness of intermetallic layer decreased after 0.2 wt pct RE was added. Finally, a first-principles calculation was performed to interpret the effect mechanism of RE on the thickness of intermetallic layer. The results indicated that La substitution in Fe₂Al₅ and FeAl₃ phases could grab electronic charges from Al atoms and weaken the formation of Fe-Al compounds.     

Pathogenic Mechanisms of Hypertrophic Cardiomyopathy beyond Sarcomere Dysfunction

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiovascular disorder, affecting 1 in 500 people in the general population. Although characterized by asymmetric left ventricular hypertrophy, cardiomyocyte disarray, and cardiac fibrosis, HCM is in fact a highly complex disease with heterogenous clinical presentation, onset, and complications. While HCM is generally accepted as a disease of the sarcomere, variable penetrance in families with identical genetic mutations challenges the monogenic origin of HCM and instead implies a multifactorial cause. Furthermore, large-scale genome sequencing studies revealed that many genes previously reported as causative of HCM in fact have little or no evidence of disease association. These findings thus call for a re-evaluation of the sarcomere-centered view of HCM pathogenesis. Here, we summarize our current understanding of sarcomere-independent mechanisms of cardiomyocyte hypertrophy, highlight the role of extracellular signals in cardiac fibrosis, and propose an alternative but integrated model of HCM pathogenesis.     

Use of Elastic Conductive Adhesive as the Bonding Agent for the Fabrication of Vertical Structure GaN-Based LEDs on Flexible Metal Substrate

Through the use of elastic conductive adhesive (ECA) as the bonding agent and patterned laser lift-off technology, a flexible metal substrate technology for the fabrication of vertical structured GaN-based light-emitting diodes (flex-LEDs) was proposed and demonstrated. It showed that the flex-LEDs have negligible changes in dominant wavelength-current and light output intensity-current-voltage characteristics when subjected to an external bending stress, indicating that the ECA used in the present technology performed well as a buffer to external stresses. As compared with conventional sapphire substrate GaN-based LEDs, Flex-LEDs with a chip size of 600 x 600 mum² showed an increase in light output intensity (power) about 216% (80%) at 120 mA with an essential decrease in forward voltage from 3.51 to 3.3 V.     

Glass biochip fabrication by laser micromachining and glass-molding process

Due to their low cost, small size, and high-speed performance, biochips are often used in various bio-experiments. Compared with polymer-based biochips, glass-based substrates are less sensitive to heat and organic environments. This study presents a hybrid processing approach that uses laser micromachining (LMM) and precision glass molding (PGM) techniques to mass-produce glass-based biochips. A silicon carbide (SiC) mold with an outside diameter of 20 mm was used to hot emboss biochip channels measuring 200 μm wide and 185 μm deep. This study also identifies the optimal conditions for glass molding when processing soda-lime glass for biochip applications, and discusses the influence of the major processing parameters on biochip channel depth. This study uses the Taguchi method to assess the effects of several molding parameters on larger-the-better performance characteristics. The experiments in this study consider the effects of several molding parameters, such as molding temperature, pressing force, moving speed, temperature holding time, and vacuum environment, to achieve optimum characteristics for biochip channels. Orthogonal array analysis indicates that the optimal process parameters includes a 620 °C molding temperature, 1 kN pressing force, 5 mm/min moving speed, 60 s temperature holding time, and a vacuum-free environment. This study also investigates the surface roughness of glass biochip channels.