Buffering packetised data: an examination of the crossover effect

Buffer analysis has traditionally relied heavily on the use of traffic models with short range (exponentially decaying) autocorrelation, e.g. Poisson and Markov modulated Poisson processes. Recent literature has suggested the presence of traffic with slowly (hyperbolically) decaying autocorrelation functions; these sources collectively and individually seem to be exhibiting the phenomenon of long range dependence (LRD). Furthermore, it has been claimed that this sort of traffic may exhibit behaviour, when buffered, that is advantageous in that a smaller buffer may be required than would be the case with non-LRD traffic. This phenomenon has been named the crossover effect, and the authors quantify its relevance to ATM networking, using simulation studies of a homogenous mix of chaotic sources. These show that there is a crossover effect, but the key finding is that this effect is much nearer to a buffer length of zero than was predicted by previous theoretical studies, actually occurring at a value so low that it has no practical significance     

Moisture migration in idealized bilayer systems: relationships among water-associated properties, structure, and texture

The effects of composition and thermal treatment on the water sorption and diffusional properties of idealized protein gels arranged in bilayer configurations were determined; these water binding/migration properties were related to the mechanical characteristics of the gels. Samples were prepared from whey protein concentrate (WPC), they consisted of water:WPC ratios of 1.5 to 5.67, and were thermally set for 20–60 min. Moisture migration rates from samples interfaced with filters were determined, as were moisture sorption capacities of samples immersed in water. The physical properties of the gels were assessed by uniaxial compression and microscopy. Results showed that gel strength and consequent extent of protein interaction—as affected by thermal treatment—controlled the ability of the gel structure to absorb water. Sorption was exponentially correlated with gel modulus and linearly correlated with a function of protein content, heating time, and immersion time. Rates of diffusion from interfaced gels were dependent solely on water content. It was concluded that the degree of protein interaction, whether influenced by concentration or thermal treatment, affected network extensibility and thus the capacity of the gels to act as receptors of moisture. Results have implications for the functionality of shelf-stable sandwiches and other multicomponent foods.     

Immobilization of inert TRISO-coated fuel in glass for geological disposal

Vitrification of TRISO-coated gas reactor fuel particles was achieved via two methods: glass melting and sintering. Inert TRISO-coated fuel particles and a borosilicate glass were used. With glass melting at 1200-1300 °C floatation and decomposition of carbon and silicon carbide occurred. Thermal pre-treatment of the particles for oxidation of pyrocarbon did not improve the coating properties of the glass. During cooling most of the particles floated and sorbed on the crucible or mold walls. The sintered glass at 700 °C showed better coating properties of the TRISO-coated fuel particles despite higher porosity compared to glass made by melting. Aqueous leaching properties of glass with particles are similar regardless the mode of fabrication, indicating the good chemical durability of the sintered glass. Sintered glasses may constitute a good technique for TRISO-coated fuel particles immobilization for an eventual deep geological disposal.     

Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya

Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land‐cover types and subwatersheds contributing run‐off to the sampling sites in the River Njoro. Standard Digital Elevation Model‐based routines were used to establish the watershed area contributing run‐off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land‐use types and the size of the subwatersheds. The mid‐stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large‐scale farming with intense, well‐preserved riparian and in‐stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small‐scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid‐reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land‐use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near‐stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.     

Performance of a non‐load‐bearing steel stud gypsum board wall assembly: Experiments and modelling

A gypsum wall assembly was exposed to an intense real‐scale compartment fire. For the wall assembly, temperatures were measured at the exposed face, within the stud cavity, and at the unexposed face during the fire exposure. Total heat flux gauges were used to measure the temporal variation of the energy incident on the walls, and cameras, both visual and infrared, were used to image the unexposed face of the wall assembly during the fire exposure. The behaviour of the wall assembly under the fire load is discussed as are current model results for a simulation of the fire test. Copyright © 2006 John Wiley & Sons, Ltd.     

A novel technique to prepare LiNbO3 at low temperature

Fresh niobium hydroxide was first precipitated from NbF₅ solution using an aqueous ammonium hydroxide under basic conditions. Then a simple procedure of mixing lithium and niobium hydroxides together and heating at a low temperature (400 °C) produced pure ultrafine single phase LiNbO₃ (LN). In the literature, this is the lowest temperature so far reported on the formation of LN. The phase content and lattice parameters are determined by X-ray diffraction (XRD). The average particle size and morphology were studied by transmission electron microscopy (TEM).     

On the recent papers by Nagode et al.

The recent work Professor Nagode and colleagues is discussed with respect to the use of mixture Weibull models.     

Gender differences in career decision making: The content and structure of preferences.

To identify possible sources of the observed differences in the career choices of women and men, three facets of career preferences were examined: the relative importance attributed to career-related aspects, the within-aspect preferences (i.e., desirable characteristics of occupations), and the structure of aspects derived from these within-aspect preferences. The career-related preferences of 2,000 young adults who were in the process of making their career decisions were analyzed. These career-related preferences were elicited during their dialogues with a computer-assisted career guidance system. The analyses revealed (a) only small gender differences in the relative importance of the aspects, (b) considerable gender differences in the within-aspect preferences, and (c) certain gender differences in the structure of aspects. The findings and their possible theoretical and practical implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of magnesium content on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castings

A study of the effect of magnesium concentration on the ageing behaviour as measured by the hardness of 380 alloy was conducted for three levels of magnesium, namely 0.06 (base alloy), 0.33 and 0.5 wt%, for water-chilled castings (dendrite arm spacing ∼ 10–15 μm). Differential scanning calorimetry analysis of as-cast samples was carried out to determine the changes in the reactions of the phases obtained during alloy solidification, employing heating rates of 0.1 and 1.0°Cs⁻¹, up to approximately 700°C. Two heat treatments were applied to the as-cast alloys: T5 comprising ageing at 25 (room temperature), 155, 180, 200 and 220°C, for times up to 200 h, and T6 comprising solution heat treatment at 480 °C or 515°C for 8 h, followed by quenching in warm water at 60°C, followed by immediate artificial ageing at 155 or 180°C for varying times up to 100h. The results show that the higher hardness values obtained with T6 treatment can be explained by the excess precipitation of magnesium-containing phases in the as-solidified alloys. This precipitation could be eliminated under the high cooling-rate conditions prevalent in die-casting operations so that T5 treatment may be used to replace T6 treatment to produce the same hardness values. In addition, solution heat treatment in the low-temperature range (480–515°C) is adequate to produce the required changes in silicon morphology and dissolution of magnesium in the matrix. No significant difference in hardness behaviour was observed when the magnesium content was increased beyond 0.3 wt%.