Effects of ITO thin films on microstructural and photocatalytic properties of layered TiO2/ITO films prepared via an extended deposition period

This study elucidates how indium tin oxide (ITO) thin film affects the microstructural and photocatalytic properties of layered TiO₂/ITO films prepared by DC magnetron sputtering. Two ITO substrates, as-received ITO (aITO) and in situ sputtered ITO (sITO), are adopted herein. Photocatalytic measurements of methylene blue and dimethyl sulfoxide indicate that the layered TiO₂/sITO film has greater photocatalytic oxidation than the TiO₂/aITO catalyst. According to photoelectrochemical tests, the latter exhibits a completely opposite activity to that of the former. Secondary ion mass spectrometry elemental depth profiles reveal that tin atoms in the sITO film really permeate into the growing TiO₂ film and promote the formation of the crystalline Ti_1−xSn_xO₂ layer. Additionally, cross-sectional transmission electron microscopy images and the selective area diffraction patterns show the difference between the diffusion of tin in the two catalysts. The photocatalytic oxidation capability is further enhanced in the layered TiO₂/sITO film because of an increase in the bandgap energy and a positive shift in the Fermi level energy of the Ti_1−xSn_xO₂ layer. Conversely, tin diffusion is limited in the aITO substrate under controlled conditions, in such a manner that a Schottky barrier can form at the TiO₂/aITO interface. Therefore, photogenerated electrons can be efficiently transferred from the overlaid TiO₂ film to the aITO substrate, producing a remarkable photocurrent density under UV illumination. Microstructural measurements reveal that the growth of the reactive {0 0 1} facets and columnar porous structure are favored by the synergetic effect of ITO substrate and an extended period of deposition. Accordingly, the photocatalytic capabilities are further raised.     

Carbonyl compounds in the roadside environment of Hong Kong

The levels of carbonyl compounds were determined at the roadside urban station at the Hong Kong Polytechnic University (HKPU) campus during January 2002 to February 2002. Nine carbonyl compounds were quantified in this study. Temperature and solar radiation were found to affect the photochemical reactions of the carbonyls. Formaldehyde/acetaldehyde ratio ranged from 1.27 to 1.35. Strong correlations between formaldehyde and acetaldehyde were found, in the time period 1800-2100, which indicated that they were originated from the same sources during this time period. Roadside carbonyl samples were also collected at four other roadside environments during 2001. Kwai Chung (KC) station showed the highest average formaldehyde and acetaldehyde concentrations due to its highest traffic flow, especially for diesel vehicles. High concentration of toluene emitted from gasoline-fueled vehicles was believed to be the cause of high benzaldehyde level at the Central (CT) station through the photochemical oxidation of toluene. The average concentrations of formaldehyde and acetaldehyde in Hong Kong are well within the ranges reported in roadside environments of other urban cities. However, Mexico City in Mexico and Cairo in Egypt had much higher concentration levels of formaldehyde and acetaldehyde than in Hong Kong roadside environment due to the incomplete combustion of different fuel compositions.     

Fabrication and Characterization of Benzocyclobutene Optical Waveguides by UV Pulsed-Laser Illumination

Buried-type benzocyclobutene (BCB) optical waveguides fabricated by UV pulsed-laser illumination are proposed and comprehensively characterized in this paper. The fabrication process is greatly simplified as compared to conventional dry-etched ridge-type BCB waveguides. The measured propagation loss at 1548 nm is as low as 0.6 dB/cm due to the buried waveguide structure. And the produced refractive index change is dependent upon the number of laser shots such that single-mode waveguides with different mode sizes can be tailored for efficient coupling. Furthermore, rigorous analyses of surface damage threshold, rms roughness, and chemical characteristics under different illumination conditions are presented to illustrate the design considerations and the chemical mechanism of the UV-induced BCB waveguides     

A Low-Latency Multi-layer Prefix Grouping Technique for Parallel Huffman Decoding of Multimedia Standards

Huffman coding is a popular and important lossless compression scheme for various multimedia applications. This paper presents a low-latency parallel Huffman decoding technique with efficient memory usage for multimedia standards. First, the multi-layer prefix grouping technique is proposed for sub-group partition. It exploits the prefix characteristic in Huffman codewords to solve the problem of table size explosion. Second, a two-level table lookup approach is introduced which can promptly branch to the correct sub-group by level-1 table lookup and decode the symbols by level-2 table lookup. Third, two optimization approaches are developed; one is to reduce the branch cycles and the other is parallel processing between two-level table lookup and direct table lookup approaches to fully utilize the advantage of VLIW parallel processing. An AAC Huffman decoding example is realized on the Parallel Architecture Core DSP (PAC DSP) processor. The simulation results show that the proposed method can further improve about 89% of decoding cycles and 33% of table size comparing to the linear search method.

Design and fabrication of multiple-valued multiplexer using negative differential resistance circuits and standard SiGe process

The design of a four-valued multiplexer using the negative differential resistance (NDR) circuit is demonstrated. The NDR circuit used in this work is made of the Si-based metal–oxide–semiconductor field-effect-transistor (MOS) and the SiGe-based heterojunction bipolar transistor (HBT). However we can obtain the NDR characteristic in its combined I–V curve by suitably arranging the MOS parameters. This novel multiplexer is made of MOS–HBT–NDR-based decoders and inverters. The fabrication is based on the standard 0.35 μm SiGe BiCMOS process.     

Improved Light Extraction Efficiency in AlGaInP Light-Emitting Diodes by Applying a Periodic Texture on the Surface

In this letter, AlGaInP-GaP-based light-emitting diodes (LEDs) were fabricated with an Si substrate and an SiO₂-ITO-Ag omni-directional reflector using a metal-to-metal bonding technique. To enhance light extraction efficiency, a periodic texture was applied to the (Al_0.5Ga_0.5)_0.5In_0.5P surface layer of AlGaInP-Si LEDs by photolithography and a wet etching process. The exterior of the etched texture consists of a series of bowl-shaped recesses. With a 350-mA current injection, the typical output power of the AlGaInP-Si LEDs with and without the textured surface (LED-I and LED-II, respectively) were measured at approximately 118 and 81 mW, respectively, when the LED chips were bonded on the TO 46 without resin encapsulation. The enhancement of output power in LED-I can be attributed to a multitude of bowl-shaped notches on the surface, which resulted in a reduction of the reabsorption probability of the photons due to the fact that the photon path length in LED-I is shorter than in LED-II before the photons escape into the free space.     

Adaptive DS-CDMA Receiver with Code Tracking in Phase Unknown Environments

In this paper, we propose and analyze a new noncoherent receiver with PN code tracking for direct sequence code division multiple access (DS-CDMA) communication systems in multipath channels. We employ the decision-feedback differential detection method to detect MDPSK signals. An ";error signal"; is used to update the tap weights and the estimated code delay. Increasing the number of feedback symbols can improve the performance of the proposed noncoherent receiver. For an infinite number of feedback symbols, the optimum weight can be derived analytically, and the performance of the proposed noncoherent receiver approaches to that of the conventional coherent receiver. Simulations show good agreement with the theoretical derivation.     

Toxicological evaluation of transgenic rice flour with an Escherichia coli phytase gene appA by sub‐chronic feeding study in Wistar rats

BACKGROUND: Phytase is increasingly used as an ingredient in swine and poultry feeds to improve the bioavailability of phytate‐bound phosphorus and reduce the supplement of elemental phosphorus in feeds. Recently, a transgenic rise (TGR) with phytase appA gene from E. coli has been developed in Taiwan. To assure the food safety of this TGR, we performed a sub‐chronic whole‐food feeding study with Wistar rats. RESULTS: Weaned feeding male and female rats were divided into TGR and non‐TGR (NTGR) groups (20 rats per group), and fed diets containing 76.8% rice flour of TGR and NTGR, respectively. After 93 days feeding, although some hematological findings and blood chemistry values differed significantly between the TGR and NTGR groups, all values were still within the normal range for rats of this age and sex. No adverse effects of TGR were observed in terms of animal behavior, weight gain, or feed utilization rate. Necropsy at the end of the experiment indicated that neither pathological lesions nor histopathological abnormalities were present in organs such as liver, kidney, intestines and testes of rats in TGR and NTGR groups. In addition, no significant differences (P > 0.05) were observed in relative organ weights, hemograms and blood indices of rats between the two groups. CONCLUSION: These results demonstrated that in a 93‐day feeding study with Wistar rats a diet containing 76.8% of TGR flour having a phytase activity of about 1500 U kg^?1 body weight per day has no adverse effects. Copyright © 2007 Society of Chemical Industry     

Effect of bifunctional modifiers of the clay on the morphology of novolac cured epoxy resin/clay nanocomposites

Montmorillonite type clay, (PK‐802) is modified by the bifunctional modifiers (2‐phenylimidazole/benzalkonium chloride, PI/BEN or 2‐methylimidazole/benzalkonium chloride, MI/BEN) with different ratio, which contain a curing agent, BEN, and the promoters/accelerator (PI and MI). These two modifying agents are simultaneously intercalated into the gallery space of pure PK‐802. The novolac cured epoxy nanocomposites are prepared with this modified clay by crosslinking polymerization reaction. Wide‐angle X‐ray diffraction is used to measure the resulting d‐spacing of modified PK‐802 and the nanocomposites. Thermo‐gravimetric analysis is used to characterize the thermal properties of the nanocomposites. The morphology of the nanocomposites is investigated using transmission electron microscopy techniques. Well dispersion of clay into the novolac cured epoxy‐clay nanocomposites resulted when simultaneously both the modifying agents with 5:5 mole ratios are used to modify the clay instead of using single modified agent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

The application of convergent beam electron diffraction (CBED) analysis on transformation‐induced plasticity (TRIP) steels

Convergent beam electron diffraction (CBED) in transmission electron microscopy (TEM) was applied to determine local carbon concentrations in low‐carbon transformation‐induced plasticity (TRIP) steels. High‐order Laue‐zone (HOLZ) lines were experimentally obtained for comparison with simulation results. A new procedure for calculating carbon content is thus proposed. Retained austenite (RA) is classified into three types by morphology; the relationship between the carbon content and the corresponding RA morphology is discussed based on CBED results. Furthermore, results of X‐Ray diffractometry measurements are also used for comparison.