Investigating the ESBWR stability with experimental and numerical tools: A comparative study

In this work, the stability of the Economic Simplified Boiling Water Reactor (ESBWR) has been studied by using a Freon-134a based experimental facility (GENESIS) and two system codes, being ATHLET 2.0a and (to a lesser extent) TRACG. During setting up the GENESIS facility and the numerical calculations, a great effort has been made to approximate the ESBWR system as accurate as possible.In general, it was found that a sufficient margin to instability exists regarding the ESBWRs nominal point. In addition, a comparison was made between the numerical and experimental results for both the thermal-hydraulic system and the reactor system. Deviations were found between the numerical and experimental results, in spite of the close similarity between the GENESIS facility and the definition of the ESBWR system in the system code. This result shows that predictions regarding real nuclear reactors, based on modeled systems, should be taken with care.     

The necessity of sample quality assessment in 14C AMS dating: The case of Cova des Pas (Menorca – Spain)

The Cova des Pas cave is a karstic cave in the cliffs of the Barranc (canyon) de Trebalúger. It is a small cave only 6.5 m deep, 4.5 m wide and 1.7 m high. Yet more than 70 burials, in foetal position, from the Early Iron Age were found in this small cave. The conservation of the archaeological remains was very unusual. Not only wood, ropes and other plant material was found, but also remains of body tissue, hair and leather. In spite of the remarkable preservation of the bodies and artefacts, the state of conservation of the bone material was very bad. The bones contained little and heavily deteriorated collagen and the organic plant material was very fragile. The special environmental conditions of the cave are the cause of these unusual preservation conditions. Although the cave is situated in a limestone cliff, the soil of the cave is very acid. Unexpectedly bad sample quality seemed to be the major drawback for AMS radiocarbon dating on hair, wood, ropes and bone collagen, as well as on bio-apatite.     

A fast block Hankel solver based on an inversion formula for block Loewner matrices

We propose a newO(p ³ n ²) algorithm for solving complexnp×np linear systems that have block Hankel structure, where the blocks are square matrices of sizep×p. Via FFTs the block Hankel system is transformed into a block Loewner system. An inversion formula enables us to calculate the inverse of the block Loewner matrix explicitely. The parameters that occur in this inversion formula are calculated by solving two rational interpolation problems on the unit circle. We have implemented our algorithm in Fortran 90. Numerical examples are included.     

The influence of preparation and doping on the reducibility of hematite by hydrogen

Samples of hematite and of hematite doped with 1 at% lithium and 1 at% vanadium are prepared by the hot kerosene drying technique. The doped samples are also prepared by an impregnation method. The various samples are used to study the reduction with hydrogen to form iron. The results indicate that the rates of reduction are strongly influenced by the particle size of the initial samples and by the repartition of the additive in the bulk and surface layer of the hematite particles. It has been shown that both additives can retard the rate of reduction. The lithium exerts its maximum influence when present in solid solution and vanadium when concentrated in the surface layer. The importance of a careful preparation of samples to be used for reduction studies, is stressed.     

Liquid jet impact damage on zinc sulphide

Zinc sulphide is an important infra-red transparent window material. When used in forward-facing aircraft components, these windows can be damaged by the impact of rain drops. The drop impact is simulated using a high-velocity jet technique and the resulting damage is described quantitatively and qualitatively for impact velocities up to 600 m sec^–1. For the 0.8 mm jets used, which simulate 4 mm diameter drop impacts, no loss of strength was observed for impacts at or below 125 m sec^–1. The calculated threshold velocity for a 2 mm drop impact of 175±5 m sec^–1 agrees well with results obtained on whirling-arm installations. Visual examination of the impact damage emphasized the importance of careful specimen preparation.     

Relations for hydration enthalpies of metalion-hydrates and stability constants of metal-dibenzoylmethane chelate complexes

Absolute hydration enthalpy (H) for cations relates well to lgK_Σ, the sum of the logarithms of the individual step chelation constants for metal-dibenzoylmethane complexes. The products $\text{d}{}^2$H and $\text{d}{}^2$lgK_Σ, where $\text{d}$ is the bond length, are essentially constant for a given cation valence (v) and increases as v². These relations fit a simple electrostatic model wherein the polarization of coordinating chelate or hydrate oxygen atoms is proportional to cation charge.     

Lack of evidence of cytoplasmic inheritance in milk production traits of dairy cattle

Heritability estimates, by year of freshening of daughter, were obtained from daughter-dam and granddaughter-granddam regressions using 61,482 triply matched first lactations of artificially sired Holstein cows obtained from the Northeast Dairy Records Processing Laboratory. After adjusting for herd-year-season effects, residual effects may include additive and other genetic effects of the animal, maternal effects, cytoplasmic effects, and other environmental effects. Analysis of residuals showed that cytoplasmic effects accounted for no variation in milk and fat yield and fat percent. Weighted yearly heritability estimates and standard errors from daughter on dam regressions were .35 +/- .01 for milk yield, .30 +/- .01 for milk fat yield, and .63 +/- .01 for milk fat percent and from daughter on granddam regressions were .34 +/- .03 for milk production, .28 +/- .03 for milk fat production, and .55 +/- .03 for milk fat percent. The differences between daughter-dam and daughter-granddam heritability estimates, which estimate twice the fraction of variance due to cytoplasmic effects, were negative and not statistically significant for milk fat yield and also were negative but highly significant for milk fat percent.     

Computing crowd loads using a nonlinear equation of motion

Structural serviceability problems such as excessive vibrations and deflections associated with human movements have recently become of great concern. The recommended design values for human loading in the current U.S. building codes and standards were developed over half a century ago and are based on strength requirements alone. Recent investigations have led to load models for individuals and small groups of people using laboratory measurements on small and medium size force platforms. The current project has been directed towards testing the group load model. We designed and built a floor system instrumented with strain gages and displacement transducers to measure dynamic loads due to large groups of people. We investigated the floor system experimentally and analytically. The input dynamic forces were determined using data from the displacement transducers and also from the strain gages. The measured results compared closely with the predicted group loads obtained from our computer simulation model developed previously.     

Macrozoobenthos of floodplain waters of the rivers rhine and meuse in the Netherlands: A structural and functional analysis in relation to hydrology

The river systems of the Rhine and Meuse include a large number of floodplain waters showing differences in hydrology and geomorphology. A classification of 100 water bodies based on their macroinvertebrate communities has been worked out as a tool for ecological management. Analyses were performed on structural (species composition) and functional (trophic relations) aspects of macrozoobenthos in relation to hydrological, vegetational, and physicochemical parameters. Based on the classification of macroinvertebrate communities, three major groups of water bodies can be distinguished, which are related to the frequency of inundation. The flood frequency constitutes the major environmental gradient which structures the zoobenthos communities in the Dutch floodplain waters. Faunal composition is mediated by substrate availability, water chemistry, and the availability of nutritional resources. This typology serves as a basis for the prediction of the impact of hydrology changes on the macrozoobenthic communities of floodplain waters of highly eutrophic and polluted rivers.