The alpha risk of the Taguchi method for STB type quality characteristic

One of the basic assumptions of experimental design is that the error variances are equal for all treatment combinations. On the contrary, one of the basic assumptions of Taguchi’s parameter design is that the error variances are not equal for the treatment combinations. Thus, the significant parameter levels are found by maximising the signal-to-noise ratio of the quality characteristic. In the analysis of variance (ANOVA) of the signal-to-noise ratio, the combination of column effects to better estimate error variance is referred to as pooling. Taguchi has suggested the strategy of “pooling-up”. When using the pooling-up strategy, there will be the tendency to make the alpha mistake more often. If the assumption of the former is true, then there is an alpha risk that judges some factor being significant when in fact it is not. The purpose of this paper is to investigate the alpha risk of the Taguchi method for the smaller-the-better (STB) type problem by simulation. The results show that the alpha risk is very high for several orthogonal arrays.     

Synthesis of a Ceramic Acid of Tungstated Alumina more Active than Silica-alumina for Decompositions of Cumene, Ethylbenzene, and Toluene

A ceramics acid, calcined at temperatures above 1000 °C, was obtained by impregnating aluminum hydroxide with aqueous ammonium metatungstate followed by calcining in air at 1000–1200 °C (1–5 wt% W); its acidity and catalytic activity for decompositions of toluene, ethylbenzene, and cumene are higher than those of silica-alumina.     

Mechanical reliability and durability of SOFC stacks. Part II: Modelling of mechanical failures during ageing and cycling

Intricate relationships between mechanical and electrochemical degradation aspects likely affect the durability of solid oxide fuel cell stacks. This study presents a modelling framework that combines thermo-electrochemical models including degradation and a contact thermo-mechanical model that considers rate-independent plasticity and creep of the components materials and the shrinkage of the nickel-based anode during thermal cycling. This Part II investigates separately or together the contributions of mechanical and electrochemical degradation on the behaviour during long-term operation and thermal cycling.     

Physical properties of egg whites and whole eggs relevant to microwave pasteurization

Microwave pasteurization is a novel thermal processing technology in which non-uniform heating may be a major challenge. In this study, the suitability of using egg whites (EWs) and whole eggs (WEs) as model foods to evaluate the heating uniformity and to determine the cold and hot spots during microwave pasteurization was investigated. The samples were prepared from mixtures of water with commercial EW or WE powders at different solid concentrations (20%, 25%, 27.5%, and 30%) and salt contents (0, 50, 100, and 200 mM). Critical physical properties for desirable model food systems include appropriate dielectric properties, gelation temperatures, gel strengths, and water holding capacities (WHCs). The gelation temperature of liquid EW and WE were 70 and 80 °C; both fell in the pasteurization temperature range. At 915 MHz, the dielectric constants of liquid EW and WE samples and their heat induced gels decreased with solid concentration while the loss factor was not affected. Loss factors of liquid EW and WE samples increased linearly with salt addition, which could be explained by the linear increase of electrical conductivities by adding salt. The strength and WHC of heat induced EW and WE gels increased linearly with solid concentration, while salt addition had no significant effect. The results demonstrated the suitability of using EW and WE as model foods to determine the heating uniformity during microwave pasteurization process.     

Emerging technologies for identification of disinfection byproducts: GC/FT-ICR MS characterization of solvent artifacts

Water samples from a local water treatment plant were analyzed, using gas chromatography Fourier transform ion cyclotron resonance mass spectrometry (GC/FT-ICR MS), to identify potential disinfection byproducts (DBPs). Both liquid-liquid extraction (LLE) and solid-phase microextraction (SPME) techniques were used for sample preparation prior to GC/MS analyses. Based on the averaged mass measurement accuracy (MMA) of better than five parts-per-million (<5 ppm), multiple solvent artifacts were identified. It is shown that solventless SPME can be utilized to reduce potential interferences from solvent stabilizers. Six DBPs were detected and their molecular compositions were assigned at a high level of confidence. At the ppb concentration ranges and in the broadband mass spectral detection mode, internally calibrated mass spectra provided concurrent high resolution (resolving power M/deltaM50% > 30,000 at m/z values -110) and MMA of better than one part-per-million (MMA < 1 ppm). The use of thermochemical data, such as proton affinities, as a complementary tool to enhance analytical resolution is also demonstrated.     

Effects of inhibitors on anaerobic microbial consortium with enhanced dechlorination activity in polychlorinated biphenyl mixture

Characterization was carried out on the anaerobic microbial consortium with enhanced degradation activity toward polychlorinated biphenyls in Kanechlor-300 and Kanechlor-400 mixtures in a burnt soil (BS) culture. The addition of molybdate to the BS culture resulted in the accumulation of less-chlorinated biphenyls such as 4,4'-dichlorinated biphenyl and 2,3',4-trichlorinated biphenyl; however, no such accumulation occurred without molybdate supplementation. No significant effect was observed in individual congeners in the BS culture supplemented with 2-bromoethane sulfonic acid. Analyses involving both the polymerase chain reaction-denaturing gradient gel electrophoresis of partial 16S rRNA genes and respiratory quinones showed that the predominant microorganisms in the BS culture were anaerobic Firmicutes, while sulfate reducers of the phyla Deltaproteobacteria, Firmicutes and Chloroflexi were absent in the culture amended with the inhibitors. No positive correlation was observed between the dechlorination activity and a PCR-based detection of gene fragments of known dechlorinating bacteria. These results suggest that sulfate reducers played an important role in the enhanced anaerobic dechlorination of PCBs in the BS culture.     

Development of novel method for screening microorganisms using symbiotic association between insect (Coptotermes formosanus Shiraki) and intestinal microorganisms

It is becoming increasingly difficult to isolate novel useful microorganisms from the natural environment using conventional screening methods based on pure culture techniques. A novel method for screening microorganisms in symbiotic association with insects was developed. This method involves the following two steps. In the first step, the existence of desired microorganisms that grow well by degrading difficult-to-degrade materials in the gut of insects is detected using the survivability of insects as an indicator. In the second step, the desired microorganisms are selected from the surviving insects. The second step is based on an idea that the guts of insects act as continuous-culture systems whereby microorganisms that cannot degrade diet components are washed out whereas those that can degrade diet components are retained and made to multiply in the gut. Coptotermes formosanus Shiraki was fed with an artificial diet containing phenol as a model of lignin-derived and difficult-to-degrade compound. Each C. formosanus feeding on an artificial diet containing 100 mg/l phenol had different levels of adaptation to the toxicity of phenol. About 20% of C. formosanus fed with an artificial diet containing 100 mg/l phenol died within a few days whereas others survived for more than 10 d. The structure of the intestinal microorganisms of the surviving C. formosanus fed with the 100 mg/l phenol artificial diet gradually changed and was very different from that of the bacterial communities obtained from the enrichment culture of wood-feeding C. formosanus using an artificial medium containing phenol as a sole carbon source. Furthermore, Only three species (as DGGE band) were detected from the gut of wood-feeding C. formosanus, whereas 200 times more phenol-degrading microorganisms were detected in the gut of C. formosanus feeding on a phenol artificial diet. Out of these nine species (as DGGE band) of phenol-degrading microorganisms were isolated. The screening method developed in this study can also be applied to various insects, leading to the isolation of various microorganisms that can degrade difficult-to-degrade compounds.