Preparation of nano-sized silicon carbide powder using thermal plasma

Nano-sized silicon carbide (SiC) powder was prepared by thermal plasma process using silicon tetrachloride (SiCl₄) and methane (CH₄). The synthesized powder was characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and particle size analyzer. The powder was dominated by β-SiC including some of α-SiC and free carbon species. The quality of the powder was varied with process conditions such as the molar ratio of H/Si and C/Si, and collecting positions. It was known that the conversion to SiC was mainly affected by the addition of hydrogen gas because it promoted the decomposition and reduction of SiCL. CH₄ was easily decomposed to carbon species for the formation of SiC as well as removal of impure oxygen, but excessive carbon suppressed the formation of crystalline SiC and resulted in the solid carbon contamination. The optimum ratio of H/Si was approx. 26 and that of C/Si was 1.1. For collecting positions, the powder collected at the vessel and filter was preferable to that at the reaction tube. The average size of the powder synthesized was estimated to be below 100 nm and uniform in distribution.     

Effect of zeolite in surface discharge plasma on the decomposition of toluene

Toluene was decomposed in a surface discharge plasma reactor packed with various zeolites. The positioning effect of the zeolite bed was also investigated Reactor-B, in which the zeolite bed was located upstream, performed much better than Reactor-A, in which the zeolite bed was located downstream. Furthermore, the decomposition efficiency in Reactor-B increased with the capacity for toluene adsorption on zeolite, while that in Reactor-A did not. The toluene adsorbed in micropores was not decomposed effectively by direct electron impact, but was decomposed by active oxygen species generated in the plasma zone on the zeolite surface. A good correlation was also observed between toluene decomposition and ozone consumption in the downward-type reactor.     

Activation of the Complement System on Human Endothelial Cells by Urban Particulate Matter Triggers Inflammation-Related Protein Production

Exposure to particulate matter (PM) is becoming a major global health issue. The amount and time of exposure to PM are known to be closely associated with cardiovascular diseases. However, the mechanism through which PM affects the vascular system is still not clear. Endothelial cells line the interior surface of blood vessels and actively interact with plasma proteins, including the complement system. Unregulated complement activation caused by invaders, such as pollutants, may promote endothelial inflammation. In the present study, we sought to investigate whether urban PM (UPM) acts on the endothelial environment via the complement system. UPM-treated human endothelial cells with normal human serum showed the deposition of membrane attack complexes (MACs) on the cell surface via the alternative pathway of the complement system. Despite the formation of MACs, cell death was not observed, and cell proliferation was increased in UPM-mediated complement activation. Furthermore, complement activation on endothelial cells stimulated the production of inflammation-related proteins. Our results revealed that UPM could activate the complement system in human endothelial cells and that complement activation regulated inflammatory reaction in microenvironment. These findings provide clues with regard to the role of the complement system in pathophysiologic events of vascular disease elicited by air pollution.     

Superiority demonstration of variance-considered machines by comparing error rate with support vector machines

To improve the performance of classification algorithms, we proposed a new varianceconsidered machine (VCM) classification algorithm in a previous study. The study showed theoretically that VCMs have lower error probabilities than SVMs. The purpose of this paper is to experimentally demonstrate the superiority of VCMs. Therefore, we verified our proposal with several case experiments using data following a Gaussian distribution with different variances and prior probabilities. To estimate performance, the experiment for each case was executed 1000 times and the error rates were averaged for accuracy. The data of each experiment have different distances between means of data, and different ratios between training data and testing data. Thus, we proved that the error rate of VCMs is lower than the error rate of SVMs, although their performances were not similar in each case. Consequently, we expect that VCMs will be applied to a variety fields.     

Zr K-edge XAS study on ZrO<Subscript>2</Subscript>-pillared aluminosilicate

The ZrO₂-pillared clay with high acidic property has been prepared by reacting 1 wt% colloidal suspension of Na⁺-montmorillonite with 1 N aqueous solution of ZrOCl₂·8H₂O and by subsequent heating. The evolution of local structure around zirconium of the intercalant stabilized in-between aluminosilicate layers upon intercalating, drying, and pillaring condition has been systematically studied by X-ray absorption spectroscopy, and compared to those of reference compounds such as ZrO₂, and ZrOCl₂ · 8H₂O and its 1 N aqueous solution. The intercalated zirconium species was identified as the Zr-tetramer, [Zr₄(OH)₁₄(H₂O)₁₀]²⁺, with an average molecular volume of 10 × 10 Å² and a thickness of 4.5 Å. Also it becomes more condensed upon drying and eventually transforms to a zirconium oxide pillar upon calcination.     

Characteristics of flamelets in spray flames formed in a laminar counterflow

A two-dimensional numerical simulation of a spray flame formed in a laminar counterflow is presented, and the flamelet characteristics are studied in detail. The effects of strain rate, equivalence ratio, and droplet size are examined in terms of mixture fraction and scalar dissipation rate. n-Decane (C₁₀H₂₂) is used as a liquid spray fuel, and the droplet motion is calculated by the Lagrangian method without the parcel model. A one-step global reaction is employed for the combustion reaction model. The results show that there appear large differences in the trends of gaseous temperature and mass fractions of chemical species in the mixture fraction space between the spray flame and the gaseous diffusion flame. The gas temperature in the spray flame is much higher than that in the gaseous diffusion flame. This is due to the much lower scalar dissipation rate and the coexistence of premixed and diffusion-limited combustion in the spray flame. For the spray flames, gas temperature and mass fractions of chemical species are not unique functions of the mixture fraction scalar dissipation rate. This is because the production rate of the mixture fraction, namely evaporation rate of the droplets, in the upstream region is not in proportion to its transport-diffusion rate in the downstream region. The behavior shows marked differences as the strain rate decreases, the equivalence ratio increases, or the droplet size decreases.     

Decomposition of Benzene Using Ag/TiO2 Packed Plasma-Driven Catalyst Reactor: Influence of Electrode Configuration and Ag-Loading Amount

This paper describes the effects of electrode configuration and the loading amount of Ag catalyst on the decomposition of gas-phase benzene using plasma-driven catalyst (PDC) reactors. Modification of ground electrode brought out a great enhancement in the energy efficiency for benzene decomposition by reducing abnormal discharges outside the reactor tube. The data of carbon balance and the selectivity of CO₂ indicated that the Ag catalyst played an important role in the decomposition of benzene, especially for the intermediates. The larger the Ag-loading amounts on the TiO₂, the better the performance of benzene decomposition in terms of the carbon balance and the selectivity of CO₂. Formation of NO₂ and N₂O indicated that the maximum specific input energy applicable to the PDC reactor should be determined not only by the decomposition efficiency but also by the formation of nitrogen oxides.     

Low power fully differential frequency doubler

A novel fully differential frequency doubler is proposed based on CMOS technology, where a stacked push-push configuration is used to generate differential output. Compared to previously reported doublers, the proposed topology has advantages in power dissipation, fundamental frequency rejection, and simplicity. By utilising the proposed doubler, a low power direct-conversion up-mixer is designed for 900 MHz applications. The fabricated up-mixer shows 5.5 dB of power conversion gain and 7.5 dBm of output IP3, while dissipating total current of 4.5 mA from 1.25 V supply.     

Improved workability using preheating in the electromagnetic forming process

Journal of Mechanical Science and Technology - Electromagnetic forming (EMF) is a high-speed method used to shape metals using a high-energy magnetic field generated by a forming coil. In this...