Effects of BaO on the glass formation of the PbO-B2O3-TiO2-BaO system in relation to transition temperatures

The variation of the BaO content on the quaternary PbO-B₂O₃-TiO₂-BaO system's glass formation tendency was investigated in relation to transition temperatures, such as melt temperature (T _f), liquidus temperature (T _l), crystallization temperature (T _c) and glass transition temperature (T _g). Compositions were melted between 800°C and 1300°C. In order to obtain bulk glass samples, glass formation was carried out using a preheated cylindrical brass mould without forcing the cooling rate to increase. Glass formation tendency increased with increasing the temperature ratios of T _g/T _l and T _c/T _l and with decreasing T _g/T _c. Eutectic compositions preferentially formed glasses from melts due to their low melting temperatures.     

Characterization of AMOLED pixel circuit without power line

We fabricated and evaluated the simple active matrix organic light emitting diode (AMOLED) pixel circuits without power line and proved that it is useful for the AMOLED display. Without power line in the pixel circuit we got higher-aperture ratio of emission area than the pixel with power line and the pixel with high aperture ratio can give a long life time due to lower current density of organic light emitting diode. However, the lack of power line requires the verification of the driving scheme of the pixel circuit. After fabrication of two types of AMOLED with and without power line in the pixel, we evaluated the pixel currents under various conditions. The operation of the pixel circuit without power line gave similar characteristics to that of the pixel circuit with power line. By the comparison, we verified that the pixel without power line is acceptable for the application to the AMOLED display combined with feedback compensation scheme for the uniform brightness.     

Design and application of precise analog computational circuits

New versatile building blocks for implementing analog functional circuits such as a multiplier, a squarer, and a square rooter based on functional terms of a differential input circuit are proposed and implemented in 0.25 um CMOS process. The input range of these circuits is over  ±1.0 V with a high linearity of less than 4% for 3.3 V power supply. The  ?3 dB bandwidth of all discussed circuits has been measured to over 200 MHz. The functional circuit size is 340 μm², and its typical power consumption is about 90 uW.     

The effect of boron on the abrasive wear behavior of austenitic Fe-based hardfacing alloys

The effect of boron on the abrasive wear behavior of the austenitic Fe–Cr–C–Si–B hardfacing alloys was investigated with varying boron concentration. It was found that the abrasive wear resistance of the hardfacing alloys increased up to 50% compared to that of boron-free alloys with increasing boron concentration. The mechanism of the abrasive wear resistance changed at 0.6 wt.% boron. Below 0.6 wt.% boron concentration, the abrasive wear resistance was improved almost linearly and strain-induced martensitic transformation was considered as the controlling factor for improving the resistance. Above 0.6 wt.% boron, it was observed that the primary borides started to precipitate. Further increase in boron concentration was not able to enhance the resistance due to the negligible change of primary borides’ size and volume fraction. With these results, it was concluded that two different effects of boron on the wear resistance of the austenitic Fe–Cr–C–Si–B hardfacing alloys existed depending on the boron concentration.     

Variations of electron flux and microbial community in air-cathode microbial fuel cells fed with different substrates

Microbial fuel cells (MFCs) can convert chemical energy to electricity using microbes as catalysts and a variety of organic wastewaters as substrates. However, electron loss occurs when fermentable substrates are used because fermentation bacteria and methanogens are involved in electron flow from the substrates to electricity. In this study, MFCs using glucose (G-MFC), propionate (P-MFC), butyrate (B-MFC), acetate (A-MFC), and a mix (M-MFC, glucose:propionate:butyrate:acetate = 1:1:1:1) were operated in batch mode. The metabolites and microbial communities were analyzed. The current was the largest electron sink in M-, G-, B-, and A-MFCs; the initial chemical oxygen demands (COD(ini)) involved in current production were 60.1% for M-MFC, 52.7% for G-MFC, 56.1% for B-MFC, and 68.3% for A-MFC. Most of the glucose was converted to propionate (40.6% of COD(ini)) and acetate (21.4% of COD(ini)) through lactate (80.3% of COD(ini)) and butyrate (6.1% of COD(ini)). However, an unknown source (62.0% of COD(ini)) and the current (34.5% of COD(ini)) were the largest and second-largest electron sinks in P-MFC. Methane gas was only detected at levels of more than 10% in G- and M-MFCs, meaning that electrochemically active bacteria (EAB) could out-compete acetoclastic methanogens. The microbial communities were different for fermentable and non-fermentable substrate-fed MFCs. Probably, bacteria related to Lactococcus spp. found in G-MFCs with fermentable substrates would be involved in both fermentation and electricity generation. Acinetobacter-like species, and Rhodobacter-like species detected in all the MFCs would be involved in oxidation of organic compounds and electricity generation.     

Microstructure and mechanical properties of Mg-HAP composites

In the present study, it has been attempted to develop biodegradable Mg-HAP (magnesium-hydroxyapatite) composite materials for bone replacement. At first the HAP powders were prepared by chemical synthesis process and synthesized powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Synthesized powders contain HAP as a major phase with tricalcium phosphate (β-TCP) as a minor phase. The Mg-HAP composites were prepared by adding different amounts of HAP powders to Mg melts and finally the billets were extruded. The microstructure of Mg-HAP composite was examined by optical microscope (OM). The presence of HAP in Mg matrix results in decrease of grain size of Mg-HAP composites. The theoretical and experimental hardness of the composites are compared with the addition of HAP. The tensile strength of composites is found to decrease with the addition of HAP, whereas compressive strength increases with HAP.