Erosion—corrosion characteristics of a 2.25 Cr-1 Mo steel exposed at low particle velocities

The erosion-corrosion characteristics of a 2.25 Cr-1 Mo steel at low particle velocities and elevated temperatures were determined using a nozzle type laboratory erosion tester. The tests were performed with 180–360 μm angular alumina particles at 60° angle of impingement at low particle velocities of 2.6–8.2 m/s and in the temperature interval 20–600°C. The steel was tested both in the as-received condition as well as in two preoxidized conditions. The erosion-corrosion rate of the steel, both in the as-received and in the preoxidized conditions, was found to increase with increasing particle velocity. In contrast, the wastage rates were relatively independent of temperature in the temperature range investigated, the only exception being specimens exposed to the lowest particle velocity (2.6 m/s) at the very highest temperature, i.e. 600°C, which displayed a drastic increase in wastage. Specimens preoxidized at 700°C exhibited a somewhat higher erosion rate compared with non-preoxidized specimens and specimens preoxidized at 500°C. Microscopy revealed four different major wastage mechanisms, i.e. (i) plastic deformation, cracking and micro chipping of surface material of a size corresponding to the area impinged by eroding particles, (ii) chipping of somewhat larger oxide fragments (up to 10–15 μm in diameter), (iii) chipping or spalling of relatively large oxide fragments (up to 30–50 μm in diameter), and (iv) spalling along the steel-oxide interface or within an oxide layer due to cohesive failure, of larger (up to 500 μm in diameter) oxide layer fragments. In the present study extensive spalling was only observed for non-preoxidized specimens exposed to the lowest particle velocity (2.6 m/s) and the two highest specimen temperatures (550°C and 600°C).     

The consumption of convenience foods: reference groups and eating situations

The theory of reasoned action was applied to study situational influence on the consumption of TV dinners. We investigated five situations, which were either time-related (weekdays vs weekends) or social (“dinner alone”, “dinner with family”, and “dinner with friends”). The intention to use a TV dinner decreased from “alone” via “with family” to “with friends”, but did not differ between weekdays and weekends. Subjective norms were a stronger influence on intentions than attitudes in all situations, except for “weekdays” and “dinner alone”. Primary reference groups were a stronger influence on intentions than secondary reference groups, and the motivation to comply with a particular reference group increased substantially when it joined for dinner. Consumption frequency for TV dinners was higher in households where the person responsible for meal preparation held a paid job, and it was positively related to the number of hours that this person was employed.     

How light conditions influence theoretical pelagic to benthic primary production ratios in small lakes

Theoretical pelagic primary production of phytoplankton and benthic primary production of periphyton were modelled for two small lakes in Estonia (Northeast Europe). Although located only 500 m apart, the water colour and light attenuation of these two lakes differed markedly. The Secchi depth (SD) in the clear‐water lake was 4.5 m and only 0.47 m in the dark‐water lake. The total phosphorus (TP) concentrations were, respectively, 15 μg/l and 28 μg/l. An empirical model whose inputs were morphometric, light conditions and dissolved organic carbon parameters obtained from in situ measurements was employed for the present study. The model calculated primary production with a time‐step of 10 min, and a spatial resolution of 10 cm, from sunrise to sunset and from lake surface to lake bottom. The primary production of periphyton and phytoplankton was almost equal in the clear lake, whereas only phytoplankton contributed to whole‐lake primary production in the dark lake because of the stronger light attenuation in the water column. The results of the present study indicated the depth‐distribution profiles differed dramatically between the two lakes. The clear lake had a deep, U‐shaped curve, with the productive layer reaching considerable depth soon after sunrise and maintaining a similar profile throughout the light hours. In contrast, the dark lake production declined rapidly with increasing depth, whereas the profile changed over the day reaching the greatest depth at noon.     

Pt nanoparticles sputter-deposited on TiO2/MWCNT composites prepared by atomic layer deposition: Improved electrocatalytic activity towards the oxygen reduction reaction and durability in acid media

Acid-treated multi-walled carbon nanotubes (MWCNTs) were decorated with TiO₂ using the atomic layer deposition (ALD) technique followed by uniform distribution of platinum nanoparticles (PtNPs) through magnetron sputtering. Surface analyses were performed by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical decontamination and characterization of the Pt-TiO₂/MWCNT electrodes were carried out by CO stripping followed by cyclic voltammetry in acid media. The oxygen reduction reaction (ORR) was studied in O₂-saturated 0.05 M H₂SO₄ solution using the rotating disk electrode (RDE) method. Durability of the prepared catalysts was examined by repetitive potential cycling. Electrochemical data obtained was analyzed and compared to that of the commercial Pt/C catalyst. It was revealed that the Pt-TiO₂/MWCNT catalysts possess higher ORR activity and better durability as compared to that of the commercial Pt/C.     

The effect of tenderizing acids on linoleic acid oxidation during marination of pork

The oxidation of lipids in different prefabricated meat products may have detrimental effects on the organoleptic properties and/or safety of meat, and poses a serious health concern. The oxidation processes may be accelerated by acids that are added to some products, e.g., marinated meat. In this work, the oxidation of free polyunsaturated fatty acids during pork marination in the presence of different acidifiers was investigated. It was demonstrated by the measurement of thiobarbituric acid reactive substances (TBARS) and by liquid chromatography - tandem mass spectroscopy that the highest degree of oxidation occurred in acetic acid and lactic acid marinades, whereas the oxidation was significantly suppressed by citric and ascorbic acids. Among the primary products of oxidation, 9,12,13-trihydroxy-10-octadecenoic acid and two isomers of hydroxy-epoxy-octadecenoic acid were dominating. A nearly linear correlation between TBARS values and total content of these two hydroxy-fatty acids was observed.     

Novel polarization-type moisture meter for determining moisture content of wood above fibre saturation point

Resistance-type wood moisture meters are not reliable at moisture contents above the fibre saturation point. The aim of this study was to develop an alternative polarization-type wood moisture meter and to analyse the different calibration methods of this moisture meter in comparison with the traditional resistance-type wood moisture meter calibration method. A significant decrease (up to 3.5% of moisture content) in the tolerance interval of a single measurement was attained by introducing and integrating the original electrical wood charging number into the calibration model of the novel wood moisture meter with electric polarization effect for a high wood moisture content (MC) above 100%. The tolerance interval convergence was analysed using the traditional method of increasing the number of measurements and averaging the results and was compared to the novel method of compensating for random deviations, as used in this study. To calibrate the wood moisture meter, the wood’s electrical resistance and electrical capacitance timelines during the electrical charging cycle were registered in real time (online) with a preselected measuring speed and saved to the microcomputer memory. When the measurements were completed, the measurement data was processed by the device’s microcomputer. This novel polarization-type moisture meter allows for the moisture content of specific tree species to be predicted by selecting a suitable calibration model from a set of eight. The novel wood moisture meter can be used to monitor wood drying and to determine seasonal variations in the moisture content of growing trees.

     

Luminescence characterization of ultrathin MgO films of high crystallinity prepared by pulsed laser deposition

Thin MgO films with thicknesses ranging from 127 to 35 nm were prepared by pulsed laser deposition on Si substrates. The crystalline films were smooth (rms roughness 0.6–1.2 nm) with an average density of 3.5 g/cm³. Cathodoluminescence study revealed emissions peaked at 7.65 eV and ascribed to the edge emission of large radius exciton states as well as luminescence due to the F and F⁺ colour centres in the range of 2–4 eV. This luminescence is efficiently excited in the absorption band peaked at 6.2 eV and in the intrinsic absorption with the onset at 7.4 eV via energy transfer processes.     

Cubic Spline Collocation for Volterra Integral Equations

In the standard step-by-step cubic spline collocation method for Volterra integral equations an initial condition is replaced by a not-a-knot boundary condition at the other end of the interval. Such a method is stable in the same region of collocation parameter as in the step-by-step implementation with linear splines. The results about stability and convergence are based on the uniform boundedness of corresponding cubic spline interpolation projections. The numerical tests given at the end completely support the theoretical analysis. Received: January 15, 2002; revised July 27, 2002 Published online: December 19, 2002     

Type systems equivalent to data-flow analyses for imperative languages

We show that a large class of data-flow analyses for imperative languages are describable as type systems in the following technical sense: possible results of an analysis can be described in a language of types so that a program checks with a type if and only if this type is a supertype of the result of applying the analysis. Type-checking is easy with the help of a certificate that records the “eureka”-bits of a typing derivation. Certificate-assisted type-checking amounts to a form of lightweight analysis à la Rose. For secure information flow, we obtain a type system that is considerably more precise than that of Volpano et al., but not more sophisticated. Importantly, our type systems are compositional.