Influence of liquid nitrogen quenching on the evolution of metastable phases during plasma spraying of (ZrO2–5 wt.% Y2O3)–20 wt.% Al2O3 coatings

The preparation of nanostructured (ZrO₂–5 wt.% Y₂O₃)–20 wt.% Al₂O₃ coatings by atmospheric plasma spraying of commercially available micron-scale powders is reported. Materials were prepared by means of a standard spraying technique and by using an improved technique that allows for the quenching of the material using liquid nitrogen-cooled substrates. Quenching leads to the controlled formation of metastable phases. The influence of liquid nitrogen cooling on the formation of the metastable phases was studied by X-ray diffraction under a grazing incidence angle of 1°. A significant increase in the amount of the metastable zirconia phase and a more homogeneous composition along the thickness were found compared to the regularly sprayed coatings. All materials were subjected to a thermal treatment for 1 h at 1400 °C to study the evolution of stable phases.     

Influence of the elaboration process on the peptide fraction with angiotensin I-converting enzyme inhibitor activity in sparkling wines and red wines aged on lees

The influence of some variables on the manufacturing process for sparkling and red wines on the angiotensin I-converting enzyme inhibitory (ACEI) activity has been studied. Ageing on lees significantly influenced the angiotensin I-converting enzyme inhibitor activity in sparkling wines. It reached maximum values at 9 months, decreasing afterwards. In red wines, the ACEI activity also increased in the wines aged on lees. In both wines, hydrophobic peptides were responsible for the ACEI activity. These peptides would make a much greater contribution to the total activity if present in higher proportions. It would therefore be advantageous to increase their concentrations in wines, either by using starting materials with high initial peptide contents or by using a highly autolytic yeast, giving a greater degree of hydrolysis of wine proteins, and higher concentrations of peptides with ACEI activity.     

Elderly drivers: Future challenges?

The objective of this paper is to describe and interpret the results from a public opinion poll about elderly drivers to provide useful information regarding future challenges related to elderly drivers. The introduction describes demographic developments, factors affecting elderly drivers, crash rates of elderly drivers and characteristics of crashes of elderly drivers. This information is used to provide a context to interpret the results of the public opinion poll. A total of 1238 drivers completed the interview, which required an average of approximately 15 min per respondent. It was administered by telephone to a random sample of Canadian drivers by Opinion Search Inc., in September 2007. Criteria for inclusion were having a valid driver's license and having driven in the past 30 days. Data were weighted according to region, gender and age to avoid bias. Univariate frequency distributions, their 95% confidence intervals and Chi-square statistics were calculated taking account of the stratified and weighted sampling design. Also, multivariate logistic regression was performed, accounting for the design effects of the used sampling design. Lower levels of concern about the issue of elderly drivers were found among the public at large and especially among elderly drivers. While general support for actions to protect elderly drivers was high, elderly drivers were less supportive for a measure requiring them to complete training to maintain their driving privileges. The results from this survey are contrasted against what is known from the literature about the issue of elderly drivers and conclusions regarding future challenges are drawn.     

A Monte Carlo methodological approach to plant availability modeling with maintenance, aging and obsolescence

In this paper we present a Monte Carlo approach for the evaluation of plant maintenance strategies and operating procedures under economic constraints. The proposed Monte Carlo simulation model provides a flexible tool which enables one to describe many of the relevant aspects for plant management and operation such as aging, repair, obsolescence, renovation, which are not easily captured by analytical models. The maintenance periods are varied with the age of the components. Aging is described by means of a modified Brown–Proschan model of imperfect (deteriorating) repair which accounts for the increased proneness to failure of a component after it has been repaired. A model of obsolescence is introduced to evaluate the convenience of substituting a failed component with a new, improved one. The economic constraint is formalized in terms of an energy, or cost, function; optimization studies are then performed using the maintenance period as the control parameter.     

Changes of meat quality characteristics and intramuscular connective tissue of beef semitendinosus muscle during postmortem aging for Chinese Yellow bulls

This study was designed to explore the changes of meat quality characteristics and intramuscular connective tissue of beef semitendinosus muscle during postmortem aging for Chinese Yellow bulls. Semitendinosus muscles were obtained at day 4 postmortem and then further aged for different periods. Chemical determinations, histological and mechanical measurements were performed for the raw and cooked steaks on days 4, 11, 14, 21, and 28 postmortem, respectively. The results showed that postmortem aging resulted in an increase in moisture content and collagen solubility, a decrease in filtering residues, primary perimysial thickness, fibre diameter, Warner‐Bratzler shear force, and transition temperature of the endomysium. The synergic effects of the myofibril and the intramuscular connective tissue determined the tenderness of aged beef.     

Type of bacterial starter culture,aging and fermentation effects on some characteristics of inoculated beef sausages

Beef sausage mixes were inoculated with either Pediococcus acidilactici with Staphylococcus xylosus or P. acidilactici with S. carnosus, subdivided and then held for 0, 24, 48 or 72 h at 8–10 °C prior to fermentation. After aging (pre-fermentation holding), the mixes were fermented for 16 h ending at 41 °C. Moisture, protein and fat contents of all sausage mixes did not differ due to holding effects over all starter cultures. The pH of mixes followed the same pattern for all mixes, declining (p < 0.05) from approximately 5.8 to pH 5.2–5.3 at 72 h aging and to 4.4–4.5 after fermentation. Total acidity of the mixes followed an inverse pattern to pH, increasing (p < 0.05) after fermentation although there was no effect due to type of starter culture. Aging had no effect on nonprotein nitrogen (NPN) content as ΔNPN among all cultures. After fermentation, however, sausages held 72 h and inoculated with S. carnosus had higher NPN contents compared to P. acidilactici alone (p < 0.05) and with S. xylosus (p < 0.10). The same effects of starter cultures on changes in total amino acid concentration were observed. Concentrations of individual amino acids showed increases depending on pre-fermentation aging period (0 h versus 72 h) followed by fermentation.     

Examination of the Aging Effects of Silicone Molds During Vacuum Casting Processes via Scanning Electron Microscopy

We present an in-depth investigation of contaminated silicone molds by use of scanning electron microscopy, that provides additional insight into the aging process of the molds. The molds lifetime in vacuum casting processes of polyurethane is limited due to contamination with the diisocyanate compound of the PUR resin. SEM investigations, combined with FIB cross-sections and EDX measurements show that three different types of particles are distributed in the contaminated silicone matrix. The particles differ in shape and size, with a range from 50 nm to 50 µm. This explains the loss in transparency and the hardened haptics of contaminated molds.     

Ammonium Perchlorate,Friend or Foe?

In part 1 of this paper, it was demonstrated that a nitroglycerine and polyethylene glycol based propellant containing ammonium perchlorate degraded at a slower rate at temperatures of 80 °C or less compared with the other two energetic materials studied which did not have this oxidizer present. It was suggested that ammonium perchlorate might act as an oxygen inhibitor reducing the oxidation rate of the polyethylene glycol binder which decreases the rate of propellant decomposition. In part 2, the specific interaction between ammonium perchlorate, nitroglycerine and polyethylene glycol is reported. It has been shown that at temperatures lower than 90 °C, if there is any uncured and unstabilised PEG present, nitroglycerine rapidly degrades in the presence of ammonium perchlorate but this is prevented if stabiliser is added. In addition, ammonium perchlorate initially appears to hinder acid hydrolysis of nitroglycerine which also slows down the degradation of polyethylene glycol based propellants. However, in the long term at low temperatures, or short term at higher temperatures, AP accelerates the decomposition of NG.     

Three‐dimensional Structural Analysis Approach for Aging Composite Solid Propellant Grains

The viscoelastic aging behavior of composite solid propellant grains is studied by a three‐dimensional thermoviscoelastic constitutive model with aging evolution, in which the crosslinking degree is taken as an aging variable. The resulting viscoelastic constitutive equations are numerically discretized into incremental form by integration algorithms, and the stress‐updating method is presented according to incremental law. Subsequently, the Abaqus‐based user material subroutine and its structural analysis module are constructed and validated through typical examples. Studies show that the results of structural analysis have high accuracy and are in well agreement with each other. The designed analysis module presents an effective aging‐mechanical analysis platform for further lifespan estimation of solid rocket motors.     

Current transport and aging in direct-current powder electroluminescent display devices

Abstract— Direct-current powder electroluminescent (DCPEL) display devices were excited by unipolar voltage pulses, and current flow through the phosphor was recorded. Devices with different formed layer thicknesses were obtained by varying the forming voltage. For a fixed electric field in the formed layer, the phosphor current did not show a substantial increase as the thickness of the formed layer increased. A model is proposed in which tunnel injection from the p-Cu₂S/i-ZnS:Mn interface of a reverse-biased p-Cu₂S/i-ZnS:Mn/n-SnO₂ structure is thought to be the controlling current mechanism. Aging studies revealed that further forming is the dominant degradation mechanism in the early stages, while load-line degradation and softening become the dominant degradation modes as the aging process is continued. The conventional DCPEL device structure was modified by introducing a thin chromium layer just prior to the deposition of the aluminum back electrode. Incorporating chromium reduced the initial series resistance of the device. A hybrid device employing a thin film (1 μm) of ZnS:Mn, sandwiched between two thin dielectric layers (5 nm), was fabricated; ZnS:Mn,Cu powder was sprayed onto the thin-film sandwich. The hybrid structure showed good luminance without forming; however, device degradation with time was still present.