Producing High-Quality Titanium Alloy by a Cost-Effective Route Combining Fast Heating and Hot Processing

Powder metallurgy is a very attractive method for producing titanium alloys, which can be near-net-shape formed and have freedom in composition selection. However, applications are still limited due to product affordability. In this paper, we will discuss a possible cost-effective route, combining fast heating and hot processing, to produce titanium alloys with similar or even better mechanical properties than that of ingot metallurgy titanium alloys. Two titanium alloys, Ti-5Al-5V-5Mo-3Cr (Ti-5553) and Ti-5Fe, were successfully produced from HDH titanium powder and other master alloy powders using the proposed processing route. The effect of the processing route on microstructural variation and mechanical properties have been discussed.     

Applying Analytical Hierarchy Process to a WiMAX Performance Evaluation Model

Evaluating performance of individual features of WiMAX technology is a topic of widespread discussion. Currently, there is no quantitative way of measuring WiMAX technology so that wireless operators can meet their design objectives. This paper outlines a set of design criteria for WiMAX and provides a decision-making aid that ranks the importance of criteria using Analytic Hierarchy Process (AHP). This ranking should sufficiently reflect market expectations of the relative importance of various design criteria. A model integrating AHP priorities with enhanced Data Envelopment Analysis (DEA) is the basis for formulating a technological value in simple,comparable format. A case study is provided to show how this technological value is used to evaluate a three year network deployment plan. In the future, this model could be extended to WiMAX equipment suppliers for the purpose of validating performance targets of individual criteria, and enhancing supplier roadmaps for future network development.     

A decision tree method for building energy demand modeling

This paper reports the development of a building energy demand predictive model based on the decision tree method. This method is able to classify and predict categorical variables: its competitive advantage over other widely used modeling techniques, such as regression method and ANN method, lies in the ability to generate accurate predictive models with interpretable flowchart-like tree structures that enable users to quickly extract useful information. To demonstrate its applicability, the method is applied to estimate residential building energy performance indexes by modeling building energy use intensity (EUI) levels. The results demonstrate that the use of decision tree method can classify and predict building energy demand levels accurately (93% for training data and 92% for test data), identify and rank significant factors of building EUI automatically. The method can provide the combination of significant factors as well as the threshold values that will lead to high building energy performance. Moreover, the average EUI value of data records in each classified data subsets can be used for reference when performing prediction. One crucial benefit is improving building energy performance and reducing energy consumption. Another advantage of this methodology is that it can be utilized by users without requiring much computation knowledge.     

Analysis of PCR-based methods for characterization of Listeria monocytogenes strains isolated from different sources

Listeria monocytogenes strains, isolated from various sources (food, environment, and animals), were used to test different PCR-based methods to investigate their capability to define the strain origin. RAPD-PCR with three primers and the SAU-PCR method, in which the DNA was first digested with the Sau3A restriction endonuclease and then amplified with a primer designed on the restriction site, were carried out, and the profiles obtained were used to perform cluster analysis. Based on the cluster analysis of Listeria spp. strains, obtained from international collections, the coefficient of similarity was selected. The results obtained showed that the methods tested in the study gave different levels of differentiation between the strains tested. The RAPD protocol using the P1254 primer and the SAU-PCR gave appreciable results only for strains isolated from animals and from a food processing plant in two different periods of the year 2003. Better differentiation was observed using the RAPD-PCR with primer D8635. As a matter of fact, it was able to distinguish L. monocytogenes obtained from different species of animals, different food samples and strains from the same production plant isolated in different periods of the year. Also primer M13 gave positive results, but the coefficient of similarity to use had to be increased to 80%. On the basis of the results observed, RAPD-PCR with primers D8635 and M13 should be considered reliable tools for epidemiological investigations focusing on L. monocytogenes.     

Effects of chilling rate on outgrowth of Clostridium perfringens spores in vacuum-packaged cooked beef and pork

Cooked, chilled beef and cooked, chilled pork were inoculated with three strains of Clostridium perfringens (NCTC 8238 [Hobbs serotype 2], NCTC 8239 [Hobbs serotype 3], and NCTC 10240). Inoculated products were heated to 75 degrees C, held for 10 min in a circulating water bath to heat activate the spores, and then chilled by circulating chilled brine through the water bath. Samples were chilled from 54.4 to 26.6 degrees C in 2 h and from 26.6 to 4.4 degrees C in 5 h. Differences in initial C. perfringens log counts and log counts after chilling were determined and compared with the U.S. Department of Agriculture (USDA) stabilization guidelines requiring that the chilling process allow no more than 1 log total growth of C. perfringens in the finished product. This chilling method resulted in average C. perfringens increases of 0.52 and 0.68 log units in cooked beef and cooked pork, respectively. These log increases were well within the maximum 1-log increase permitted by the USDA, thus meeting the USDA compliance guidelines for the cooling of heat-treated meat and poultry products.     

Stimulation of starter culture for further reduction of foodborne pathogens during salami fermentation

This study was conducted to determine if stimulated meat starter culture (MSC; Pediococcus acidilactici) would further control Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus during salami fermentation. Manganese ion (0.005% of MnSO4) was used as a stimulator for the growth and acid production of MSC. After 24-h salami fermentation, nonstimulated MSC and stimulated MSC reduced E. coli O157:H7 levels by 1.3 and 2.3 log10 units, respectively. Nonstimulated MSC reduced L. monocytogenes levels by 1.2 log10 units, whereas the stimulated MSC achieved a 2.2-log10 reduction after 24-h fermentation. In the case of S. aureus, nonstimulated MSC and stimulated MSC reduced S. aureus levels by 1.3 and 2.3 log10 units after 24-h fermentation, respectively. Stimulated MSC by MnSO4 reduced those foodborne pathogens more effectively compared with nonstimulated MSC (P < 0.05).     

Simple thermodynamic model of the extension of solid solution of Cu–Mo alloys processed by mechanical alloying

The objective of this work is proposing a simple thermodynamic model to explain the increase in the solubility limit of the powders of the Cu–Mo systems or other binary systems processed by mechanical alloying. In the regular solution model, the effects of crystalline defects, such as; dislocations and grain boundary produced during milling were introduced. The model gives results that are consistent with the solubility limit extension reported in other works for the Cu–Cr, Cu–Nb and Cu–Fe systems processed by mechanical alloying.     

A new model system for lipid interactions in stratum corneum vesicles: effects of lipid composition, calcium, and pH

We prepared large unilamellar vesicles (LUVs) with three different stratum corneum lipid compositions: constant amounts of ceramides (55 wt %) and fatty acids (15%) with varying amounts of cholesterol sulfate (0-15%) and cholesterol (15-30%). One of the compositions served as a model for normal stratum corneum, while the second one served as a model for recessive X-linked ichthyosis stratum corneum. The third composition consisted of no cholesterol sulfate. Intervesicle lipid interactions in these LUVs were monitored by fluorescence methods for content leakage, and contents mixing at pH 9, in the absence and presence of Ca2+, and at pH 6. Since the content leakage and contents mixing assays were originally developed for phospholipid vesicles, we characterized the probe binding and the probe quenching properties for stratum corneum LUV systems, and modified the assays slightly accordingly. The time-dependent fluorescence intensity changes in the probe-containing LUVs at pH 9 and 6 and in response to the addition of calcium were monitored. Our results demonstrated that all three types of LUVs were relatively stable at pH 9. Addition of Ca2+ or decreasing the pH to 6 activated intervesicle lipid mixing followed by vesicle fusion and lysis. We found that the LUVs with no cholesterol sulfate and 30% cholesterol exhibited a more extensive Ca2+- or low-pH-activated intervesicle lipid interaction than LUVs with either 5% cholesterol sulfate and 25% cholesterol or 15% cholesterol sulfate and 15% cholesterol. These results suggest that fusogenic agents such as Ca2+ and H+ act to neutralize the fatty acids in the lipid bilayer of stratum corneum vesicles. The inclusion of 5-15% cholesterol sulfate helps to prevent the collapse of fused vesicles into other structures.     

Effects of Bi4Ti3O12 addition on the microstructure and dielectric properties of modified BaTiO3 under a reducing atmosphere

The effects of Bi₄Ti₃O₁₂ addition on the microstructure and dielectric properties of Mn-modified BaTiO₃ were investigated to develop low temperature fired BaTiO₃-based ceramics with stable temperature characteristics. The sintering temperature of Mn-doped BaTiO₃ could be reduced to 1200 °C by adding more than 1 mol% Bi₄Ti₃O₁₂. TEM results show an apparent core–shell structure with 2 mol% Bi₄Ti₃O₁₂ addition. However, it was destroyed when the Bi₄Ti₃O₁₂ content increased from 2 to 4 mol%. The permittivity decreased and the Curie temperature shifted to higher temperature when the Bi₄Ti₃O₁₂ content increased from 0 to 3 mol%. The temperature characteristic of capacitance was very close to the EIA X8R specification when 2 mol% Bi₄Ti₃O₁₂ was added due to the presence of the core–shell grain structure and raised Curie temperature. With adequate Bi₄Ti₃O₁₂ addition, the BaTiO₃-based system shows great potential for applications in EIA X8R-type multilayer ceramic capacitors.