Surface morphology and I-V characteristics of single-crystal,polycrystalline, and amorphous silicon FEA's

This letter reports the surface morphology and current-voltage (I-V) characteristics of single-crystal silicon (c-Si), polycrystalline silicon (poly-Si), and amorphous silicon (a-Si) field emitter arrays (FEAs). As-deposited a-Si film has a smoother surface than poly-Si film. The surface morphology of the a-Si remains smooth even after phosphorus doping and oxidation at 950°C to be improved in emission characteristics, i.e., smaller anode current deviation among arrays smaller gate current, and higher failure voltage than those of poly-Si FEAs. Such improved characteristics can be explained by the smooth surface morphology which is kept during doping and oxidation. The surface roughness and emission characteristics of a-Si FEAs are comparable to those of c-Si FEAs     

Microwave dielectric properties of Mg4Nb2O9 ceramics produced by hydrothermal synthesis

Mg₄Nb₂O₉ ceramics have been prepared by a hydrothermal synthesis in order to reduce the sintering temperature. The sintering and microwave dielectric properties of the hydrothermally processed Mg₄Nb₂O₉ were studied under various sintering temperatures ranging from 900 to 1300°C. The highest Q×f _o value of 26,069 GHz was obtained at the sintering temperature of 1300°C and is attributed to the increased density and appropriate grain growth. τ _f value of ?17.1 ppm/°C was improved by the addition of TiO₂ and τ _f value of 6.7 ppm/°C was obtained at 20 wt% TiO₂. Chemical compatibility of Mg₄Nb₂O₉ with Ag was tested to identity the possibility of using Mg₄Nb₂O₉ for an LTCC application. Since any secondary phase was not observed in the XRD pattern of the mixtures of Mg₄Nb₂O₉ and Ag powder heat treated at 900°C, it was considered that the Mg₄Nb₂O₉ system is applicable to the multilayer microwave devices using Ag as an electrode.     

Shrinkage cracking of styrene butadiene polymeric emulsion‐modified concrete using rapid‐hardening cement

This study was performed to resolve the problem of cracks caused by the rapid hydration heat produced during the early setting stages of rapid‐hardening cement. To address the hydration heat of rapid‐hardening cement, we prepared a modified rapid‐hardening cement using calcium sulfoaluminate clinker combined with a styrene butadiene (SB) polymer. The performance of SB polymeric emulsion‐modified concrete made from modified rapid‐hardening cement was assessed by determining shrinkage (change in length, and plastic and autogenous shrinkage). The modified rapid‐hardening cement in combination with SB polymeric emulsion effectively reduced cracking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural evolution during crystallization in phase separated Ti–Y–Al–Co metallic glass

Structural evolution during heat treatment of melt spun Ti₃₆Y₂₀Al₂₄Co₂₀ alloy was studied using differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. The as-melt spun Ti₃₆Y₂₀Al₂₄Co₂₀ specimen showed a hierarchical complex microstructure consisting of Ti-rich and Y-rich amorphous phases and crystallized with two-step process. Crystallization in the phase separated two phase mixture took place in a confined mode due to different thermal stability and complex microstructure, resulting in various nano-scaled microstructural formation ranging from fine distribution of crystalline particles in amorphous matrix to fine distribution of amorphous particles in crystalline matrix.     

Analytical techniques with a cyclotron on polymers

Nuclear analytical techniques (PIXE, RBS and ERDA) have been applied to investigate diffusion processes in polymer light-emitting diodes (PLEDs), employing a 30 MeV AVF cyclotron. The techniques prove to be useful in identifying the origin of the diffusion process and the nature of molecules transported from the hole injecting ITO electrode into the polymer layer.     

Authentication and correction of digital watermarking images

A novel function for image watermarking is introduced. The proposed function gives a restoration/correction capability to image watermarking as well as the detection and localisation of alterations. The basic idea of the proposed watermarking technique is to adopt conventional error control coding techniques for generating a watermark.     

Honey major protein characterization and its application to adulteration detection

The major proteins in honey have different molecular weights depending upon the honeybee species. To confirm the origin of major honey proteins, honey protein produced by Apis cerana or Apis mellifera were purified and analyzed by MALDI-TOF. Two major proteins were identified as a major royal jelly protein 1. Although two major proteins shared primary structure, they showed different molecular weights of 56 and 59 kDa, respectively. To discriminate the honeybee species producing honey using SDS–PAGE, artificial marker proteins, 56 and 59 kDa, were produced from Escherichia coli. Two artificial marker proteins were co-electrophoresed with honey samples and the difference in molecular weight was readily distinguished by SDS–PAGE. Therefore, the measurement of major proteins in honey is a useful method to discriminate the honey that produced from different honeybee species.     

Improved configuration of supported nickel catalysts in a steam reformer for effective hydrogen production from methane

The heat and mass transfer characteristics in a steam reformer are investigated via experimental and numerical approaches and a new configuration of packed catalysts is proposed for effective hydrogen production. Prior to the numerical investigation, parametric studies are carried for the furnace temperature, steam-to-carbon (S:C) ratio, and gas flow rate. After validation of the developed code, numerical work is undertaken to determine the relationship of the operating parameters. Based on the experimental and numerical results, and with the goal of obtaining optimum heat transfer characteristics and an efficient catalyst array, a new configuration for the packed bed is proposed and numerically investigated taking into account the endothermicity of the steam reforming reaction. A bed packed repeatedly with inert and active catalysts is found to be an efficient means to obtain the same, or better, hydrogen production with small amounts of the active catalysts compared with a typical steam reformer.     

Monolithically integrated grating cavity tunable lasers

A novel grating cavity tunable laser is proposed and experimentally demonstrated. It is realized by monolithically integrating a semiconductor optical amplifier, a dispersive element, a phase-control section, and an etched diffraction grating in a single chip. Tuning operation is based on electrically controlled beam deflection provided by dispersive element and phase matching by phase-control section. With the electrical control, the wavelength tuning of 8.5 nm with a sidemode suppression ratio of about 35 dB has been successfully achieved.