On the propulsion quality of ships operating at restricted water depth

The propulsive efficiency of marine vehicles has been investigated from the point of view of the effect of restricted waters of the propulsion characteristics. Model tests have been performed for both single-screw and twin-screw vessels. Also optimum propulsion data for modern sea-going single-screw merchant ships operating in unrestricted waters are presented for the sake of general comparison.     

Seasonal Changes in Soluble Carbohydrates, Starch, and Energy Content in Mediterranean Seagrasses

Abstract. In all scagrass species investigated, rhizomes were the main storage organs for soluble carbohydrate reserves, and the highest levels were found in Cymodocea nodosa (U cria ) A scherson . Sucrose was the primary soluble carbohydrate identified in Posidonia oceanica (L.) D elile , and Zostera noltii H ornem . This disaccharide was dominant in Cymodocea nodosa roots, as well as in its rhizome in winter. Myo-inositol was the main cyclitol in Zostera noltii. In Cymodocea nodosa leaves 1-chiro-inositol was the main sugar component; it was also present to a lesser extent in the roots and rhizomes. The amounts of glucose and fructose were correlated with growth to a certain extent in all species. Higher amounts of starch were stored in the rhizomes of Posidonia oceanica and Zostera noltii. The energy content of Mediterranean scagrasses was significantly higher than in tropical species. No distinct seasonal trend in energy content could be observed.     

Seasonal Changes in Nitrogen, Free Amino Acids, and C/N Ratio in Mediterranean Seagrasses

Abstract. Seasonal changes in nitrogen, free amino acids, and carbon were investigated in the three Mediterranean seagrasses Posidonia oceanica, Cymodocea nodosa , and Zostera noltii. Leaves, rhizomes, roots, as well as dead plant material were analysed separately. Highest N-concentrations were obtained in the winter months, regardless of species or plant part. In contrast to the other two species, the N-content in Posidonia was higher in the rhizomes than in the leaves.
In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking in Posidonia , was the main component in Cymodocea. In Posidonia , FAA decreased from 320umol g^-1 (dry wt) in leaf sheaths to 1.5 umol g^-1 (dry wt) in the leaf tips. The function of proline as a possible storage and/or stress metabolite is discussed.
High C/N values in dead P. oceanica and C. nodosa rhizomes as well as in P. oceanica wrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detached C. nodosa and Z. noltii leaves, which began to decompose shortly after detachment from the plants.     

Coral Recruitment and Regeneration on a Maldivian Reef 21 Months after the Coral Bleaching Event of 1998

Abstract. This paper describes the quantitative inventory of stony corals on a Maldivian reef after the bleaching event of 1998. The detailed data, collected in March 1999 and March 2000, comprise survival, new recruitment and regenerates. They were obtained in 6 transects laid out randomly on the reef flat, on 22 Acropora tables on 6 sites at the reef edge and on 39 Porites lobata blocks and 1 Diploastrea heliopora colony. The present cover of living zooxanthellate corals is reduced to ca. 2 – 5 % of its previous state. Acroporidae and Pocilloporidae were practically wiped out, while Poritidae survived partly and Agariciidae (esp. Pavona) are now the dominant group. New settlements on dead Acropora tables were mainly Agariciidae, followed by Acroporidae and Pocilloporidae. Regenerates on Porites were pronounced and the apparent yearly increase in mass was about threefold that of Diploastrea, which is 3 – 4 mm per year. The influence on reef ecology in terms of coral substrate and species, possible sources of larvae, change of guilds in reef builders, other species and the prospect for further development of the reef, with respect to growth versus erosion, is discussed.     

Multi-Scale Texture Modeling

Patterns of crystallographic preferred orientation are referred to as texture. The specific subject of texture analysis is the experimental determination and interpretation of the statistical distribution of orientations of crystals within a specimen of polycrystalline material, which could be metals or rocks. The objective is to relate an observed pattern of preferred orientation to its generating processes and vice versa. In geosciences, texture of minerals in rocks is used to infer constraints on their tectono-metamorphic history. Since most physical properties of crystals, such as elastic moduli, the coefficients of thermal expansion, or chemical resistance to etching depends on crystal symmetry and orientation, the presence of texture imparts directional properties to the polycrystalline material. A major issue of mathematical texture analysis is the resolution of the inverse problem to determine a reasonable orientation density function on SO(3) from measured pole intensities on , which relates to the inverse of the totally geodesic Radon transform. This communication introduces a wavelet approach into mathematical texture analysis. Wavelets on the two-dimensional sphere and on the rotational group SO(3) are discussed, and an algorithms for a wavelet decomposition on both domains following the ideas of Ta-Hsin Li is given. The relationship of these wavelets on both domains with respect to the totally geodesic Radon transform is investigated. In particular, it is shown that the Radon transform of these wavelets on SO(3) are again wavelets on . A novel algorithm for the inversion of experimental pole intensities to an orientation density function based on this relationship is developed.     

TRANSALP—deep crustal Vibroseis and explosive seismic profiling in the Eastern Alps

The TRANSALP consortium, comprising institutions from Italy, Austria and Germany, carried out deep seismic reflection measurements in the Eastern Alps between Munich and Venice in 1998, 1999 and 2001. In order to complement each other in resolution and depth range, the Vibroseis technique was combined with simultaneous explosive source measurements. Additionally, passive cross-line recording provided three-dimensional control and alternative north–south sections. Profits were obtained by the combination of the three methods in sectors or depths where one method alone was less successful.The TRANSALP sections clearly image a thin-skinned wedge of tectonic nappes at the northern Alpine front zone, unexpected graben or half-graben structures within the European basement, and, thick-skinned back-thrusting in the southern frontal zone beneath the Dolomite Mountains. A bi-vergent structure at crustal scale is directed from the Alpine axis to the external parts. The Tauern Window obviously forms the hanging wall ramp anticline above a southward dipping, deep reaching reflection pattern interpreted as a tectonic ramp along which the Penninic units of the Tauern Window have been up-thrusted.The upper crystalline crust appears generally transparent. The lower crust in the European domain is characterized by a 6–7 km thick laminated structure. On the Adriatic side the lower crust displays a much thicker or twofold reflective pattern. The crustal root at about 55 km depth is shifted around 50 km to the south with respect to the main Alpine crest.     

Crustal structure of the Eastern Alps along the TRANSALP profile from wide-angle seismic tomography

The objective of the TRANSALP project is an investigation of the Eastern Alps with regard to their deep structure and dynamic evolution. The core of the project is a 340-km-long seismic profile at 12°E between Munich and Venice. This paper deals with the P-wave velocity distribution as derived from active source travel time tomography. Our database consists of Vibroseis and explosion seismic travel times recorded at up to 100 seismological stations distributed in a 30-km-wide corridor along the profile. In order to derive a velocity and reflector model, we simultaneously inverted refractions and reflections using a derivative of a damped least squares approach for local earthquake tomography. 8000 travel time picks from dense Vibroseis recordings provide the basis for high resolution in the upper crust. Explosion seismic wide-angle reflection travel times constrain both deeper crustal velocities and structure of the crust–mantle boundary with low resolution. In the resulting model, the Adriatic crust shows significantly higher P-wave velocities than the European crust. The European Moho is dipping south at an angle of 7°. The Adriatic Moho dips north with a gentle inclination at shallower depths. This geometry suggests S-directed subduction. Azimuthal variations of the first-break velocities as well as observations of shear wave splitting reveal strong anisotropy in the Tauern Window. We explain this finding by foliations and laminations generated by lateral extrusion. Based on the P-wave model we also localized almost 100 local earthquakes recorded during the 2-month acquisition campaign in 1999. Seismicity patterns in the North seem related to the Inn valley shear zone, and to thrusting of Austroalpine units over European basement. The alignment of deep seismicity in the Trento-Vicenza region with the top of the Adriatic lower crust corroborates the suggestion of a deep thrust fault in the Southern Alps.     

Laboratory Studies Of Wind Stress Over Surface Waves

Simultaneous laboratory observations of wind speed, wind stress, and surfacewind-wave spectra are made under a variety of wind forcing patterns using cleanwater as well as water containing an artificial surfactant. Under typical experimentalconditions, more than half of the total stress is supported by the wave-induced stressrather than by the surface viscous stress. When the surfactant reduces the shortwind-wave spectra, the wind stress also decreases by as much as 20–30% at agiven wind speed. When the wind forcing is modulated in time, the wind stresstends to be higher under decreasing wind than under increasing wind at a givenwind speed, mainly because the response of short wind-wave spectra to varyingwind forcing is delayed in time. These examples clearly demonstrate that therelationship between the wind speed and the wind stress can be significantlymodified if the surface wave field is not in equilibrium with the wind forcing.Next, we examine whether the wind stress is estimated accurately if the wave-inducedstress by all surface wave components is explicitly evaluated by linear superpositionand is added to the surface viscous stress. It is assumed that the surface viscous stressis uniquely related to the wind speed, and that the wind input rate is determined by thelocal, reduced turbulent stress rather than the total stress. Our wind stress estimatesincluding the wave contributions agree well with observed wind stress values, evenif the surface wave field is away from its equilibrium with the wind in the presenceof surface films and/or under time-transient wind forcing. These observations stronglysuggest that the wind stress is accurately evaluated as a sum of the wave-induced stressand the surface viscous stress. At very high winds, our stress estimates tend to be lowerthan the observations. We suspect that this is because of the enhancement of wind stressover very steep (or breaking) short wind-waves.