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1.
This paper describes a numerical method for calculating the two-dimensional hydrodynamic coefficients of one or two infinitely long, arbitrary cylinders forced to oscillate in or below the free water surface. The oscillation modes, amplitudes and phases of the cylinders may be different from one another. Finite water depth and a quay can be taken into account. Special consideration has been given to the radiation boundary conditions.The computer program developed has been tested in various two-dimensional boundary situations; it has produced results in good agreement with results obtained by other methods. 相似文献
2.
4-tert-octylphenol and 17beta-estradiol applied by feeding to flounder Platichthys flesus: induction of vitellogenin and accumulation in tissues 总被引：1，自引：0，他引：1
In order to simulate a possible natural administration route of xenoestrogens male flounder Platichthys flesus were exposed via the diet to the alkylphenol 4-tert-octylphenol. Treatment with 4-tert-octylphenol (10, 50 and 100 mg OP kg(-1) BW) or 17beta-estradiol (0.05 mg kg(-1) BW) every second day during a period of 11 days resulted in a significant increase in plasma vitellogenin (Vtg) concentrations. The induction of Vtg was greatest in the fish receiving 50 mg OP kg-' BW. A significant accumulation of 4-tert-octylphenol was found in liver and muscle tissue of the OP treated groups. The tissue concentrations of 4-tert-octylphenol and the plasma vitellogenin concentration were positively correlated. The results show that 4-tert-octylphenol accumulates in liver and muscles of flounder P. flesus, and exerts estrogenic effects such as vitellogenin induction. 相似文献
3.
4.
The Greenland Ice Sheet is thinning at an accelerating pace and the ice sheet's contribution to sea-level rise has doubled in less than a decade. New data show rapid and widespread changes in the behaviour of the ice sheet, particularly along the coastal margin. These changes coincide with a decade of sustained Arctic warming of up to 3 °C. Decay of the Greenland Ice Sheet in response to global warming will not only be governed by increased surface melting during longer and warmer summers but also by a speed-up of coastal glaciers that drain the interior ice sheet. A precise estimate of sea-level rise in the twenty-first century relies on improved theoretical treatment of these glaciers in computer models. 相似文献
5.
Poul Klenz Larsen 《Environmental Geology》2007,52(2):375-383
This paper presents an investigation of the decay of bricks in the chancel vault of Brarup Church located close to the Baltic
Sea at the island of Falster in Denmark. The aim of the work was to study a peculiar phenomenon in order to prescribe appropriate
treatment. Although protected by a lime plaster, some bricks were pulverized up to 50 mm deep from the topside. The decay
occurred in a random pattern over the structure, with undamaged bricks positioned next to deteriorated bricks. The brick structure
was investigated by Mercury Intrusion Porosiometry. All bricks had a majority of pores in the range 1–10 μm, but the decayed
bricks also had a fraction of pores with a diameter less than 100 nm. The difference may be due to a lower firing temperature,
or it may be a consequence of the salt decay. Salt analysis proved that the deteriorated bricks were contaminated with sodium
chloride, which could have degraded the brick structure. However, the powdering of the bricks may be caused by the precipitation
of gypsum, which was found in the brick powder but not in the deteriorated brick itself. According to calculations with the
computer program RUNSALT, the precipitation of gypsum is much influenced by the presence of sodium chloride. The gypsum precipitates
due to changes in temperature between 0 and 30°C and variations in relative humidity between 75 and 95%. Seasonal climatic
changes in the attic were measured to cover this interval. Perhaps sodium chloride acted as a catalyst that facilitated the
accumulation and precipitation of gypsum at the topside of the bricks. A sacrificial plaster, which is the traditional treatment
for salt contaminated structures, would not prevent such decay. 相似文献
6.
Christian Kronborg Henry Bender Regnar Bjerre Rud Friborg Hans O. Jacobsen Lars Kristiansen Poul Rasmussen Poul R. Sørensen Gunnar Larsen 《Boreas: An International Journal of Quaternary Research》1990,19(3):273-287
Glaciostratigraphic investigations at one key locality (Haldum), 9 major and about 160 minor localities in East and Central Jutland, Denmark, together with laboratory work, have led to the establishment of a stratigraphy consisting of 10 till units, usually separated by meltwater deposits. The stratigraphy is in some degree supported by thermoluminescence datings. The complete sequence includes one till unit with associated meltwater deposits of Menapian age, three till units with intercalated meltwater deposits of Elsterian age, marine sediments deposited during the Holsteininan, and three till units with intercalated of Elsterian age, marine sediments deposited during the Holsteinian, and three till units with intercalated glaciofluvial sedimants of Saalian age. Eemian deposits are present above this level, and the whole sequence is capped by till and meltwater deposits related to three glacial advances during the Weichselian. 相似文献
7.
The normal and shear strains obtained in torsion shear tests may be interpreted in two different ways to gain insight into (1) the type of plastic potential to be employed in hardening plasticity stress–strain models, and (2) the coincidence in physical space of the plastic strain increment direction with the stress direction during principal stress rotation. Thirty-four drained torsion shear tests were performed on hollow cylinder specimens of Santa Monica Beach sand deposited by dry pluviation. Twenty-six tests were performed on tall specimens with height of 40 cm, and eight tests were performed on short specimens with height of 25 cm to investigate the effect of the specimen height on the soil behavior in hollow cylinder specimens. Each test was conducted with the same, constant inside and outside confining pressure, σr, thus tying the value of b = (σ2–σ3)/(σ1– σ3) to the inclination, β, of the major principal stress. The directions of strain increment vectors at failure are compared with the directions corresponding to associated and non-associated flow. The relation between the directions of major principal strain increment and major principal stress during rotation of principal stress axes in physical space are investigated. 相似文献
8.
Poul V. Lade 《国际地质力学数值与分析法杂志》1988,12(4):351-370
Development of constitutive models for engineering materials is often based on a framework of elasticity and plasticity theories as developed for metals. Prsented here is a review of some of the basic differences in the experimentally observed behaviour of metals and frictional materials. Two of the distinguishing characteristics between metals and frictional materials are the absence or presence of voids and the tendency to change or maintain constant volume during compression and shear. These differences must be recognized in order to develop reasonable constitutive models for frictional materials. 相似文献
9.
Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01–0.03 dex for F, G, and K stars. Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered. The determination of high-precision stellar abundances of the elements has led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. (i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. (ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; (iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star- and cluster-formation processes are more complicated than previously thought; (iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets. We conclude that if stellar abundances with precisions of 0.01–0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account. 相似文献
10.
Ida Damgaard Poul L. Bjerg Carsten S Jacobsen Aikaterini Tsitonaki Henriette Kerrn‐Jespersen Mette M. Broholm 《Ground Water Monitoring & Remediation》2013,33(1):48-61
At a low permeability clay till site contaminated with chlorinated ethenes (Gl. Kongevej, Denmark), enhanced reductive dechlorination (ERD) was applied by direct push injection of molasses and dechlorinating bacteria. The performance was investigated by long‐term groundwater monitoring, and after 4 years of remediation, the development of degradation in the clay till matrix was investigated by high‐resolution subsampling of intact cores. The formation of degradation products, the presence of specific degraders Dehalococcoides spp. with the vinyl chloride (VC) reductase gene vcrA, and the isotope fractionation of trichloroethene, cis‐dichloroethene (cis‐DCE), and VC showed that degradation of chlorinated ethenes occurred in the clay till matrix as well as in sand lenses, sand stringers, and fractures. Bioactive sections of up to 1.8 m had developed in the clay till matrix, but sections, where degradation was restricted to narrow zones around sand lenses and stringers, were also observed. After 4 years of remediation, an average mass reduction of 24% was estimated. Comparison of the results with model simulation scenarios indicate that a mass reduction of 85% can be obtained within approximately 50 years without further increase in the narrow reaction zones if no donor limitations occur at the site. Long‐term monitoring of the concentration of chlorinated ethenes in the underlying chalk aquifer revealed that the aquifer was affected by the more mobile degradation products cis‐DCE and VC generated during the remediation by ERD. 相似文献