HYCAT: Hybrid hydrofoil catamaran concept

A hybrid marine vehicle concept has been developed which utilizes a combination of static and dynamic support. This concept, termed HYCAT² for HYdrofoil CATamaran, combines a planing catamaran hull with two fully submerged hydrofoils mounted in tandem fore and aft. The hullform is developed by adding a high length/beam ratio, high deadrise sidehull along the keel of each catamaran demihull. The sidehull, which is the only portion immersed when operating foilborne, provides buoyancy support. Spray strips provide discontinuities which separate the flow and provide dynamic lift in addition to the hydrofoils. Stability in the heave, pitch and roll degrees of freedom is achieved through the displacement dependent sidehull buoyancy and the rate and displacement dependent lift developed by the spray strips and hydrofoils. A comprehensive series of model tests has been conducted to characterize the smooth and rough water performance.     

Sound velocity,density, and related properties along a transect across the Bay of Bengal

Physical properties, sound velocity and density of 95 core samples from ten locations along a transect (parallel to 15°N latitude) across the Bay of Bengal were measured. Results indicate that sound velocities range from 1,482 to 1,679 m/s (av: 1,583 m/s) and densities from 1,338 to 1,757 kg/m³ (av: 1,527 kg/m³). It has been observed that dark colored clays and sandy clays show higher values of sound velocity and density than the average values. A comparative study of the same with that of the sediment cores collected from the Norwegian basin, Mediterranean Sea, and Hatteras, Nares Abyssal plains, western North Atlantic Ocean was done.     

Virgin rock temperatures from well logs — accuracy analysis for some advanced inversion models

Temperature data from 18 measurement series obtained during logging of the Oseberg field in the northern North Sea are presented. Because the measurement series are taken at approximately the same depth, they should give identical temperatures after depth correction, and are suitable for assessing the performance of different models used to determine virgin rock temperatures from well log information.We have used this data set to test the properties of the different models given by Shen and Beck (1986). Although these models were built to simulate closely the thermal recovery of a well and are unbiased, the uncertainties in the temperature estimates when applied to real data are found to be no less than those from simpler (biased) models. This fact confirms the conclusion of Hermanrud (1989a) who showed that physical factors other than those presently accounted for significantly influence the thermal recovery of a borehole.     

The behaviour of a Cu(II) ion selective electrode in seawater; copper consumption capacity and copper determinations

Determinations of copper consumption capacity (CuCs.C) and labile copper concentrations in surface coastal seawater, using a copper ion selective electrode (Cu-ISE) potentiometric method under predominantly diffusive conditions, are reported. For evaluation of the copper concentrations, the points of the endpoint contiguity zone of the CuCs.C titration curve were treated by an ISE multiple standard addition technique. The results were compared with those obtained by means of a Chelex-100 (calcic form) ‘batch’ procedure-potentiometric stripping analysis.The labile copper of the sample was determined at concentrations down to 10.70 nM with an average RSD of 12%, independent of the Cu-ISE employed. For adjacent subsamples, the mean CuCs.C values obtained for El Way seawater were equivalent to 81.05 and 48.00 nM copper, with an RSD of 4 and 7%, and for Isla Santa Maria seawater the value was equivalent to 70.27 nM copper, with an RSD of 7%. The theoretical approach of the electrode diffusive mechanism proposed, which would depend, fundamentally, on the adsorptive, complexing and reducing properties of the dissolved organic matter in the seawater sample, allows simultaneous analytical determination of CuCs.C and labile copper concentration in seawater.     

Mechanisms controlling the temporal variation of the sea ice edge in the Southern Ocean

This paper examines the mechanism controlling the short time-scale variation of sea ice cover over the Southern Ocean. Sea ice concentration and ice velocity datasets derived from images of the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) are employed to reveal this mechanism. The contribution of both dynamic and thermodynamic processes to the change in ice edge location is examined by comparing the meridional velocity of ice edge displacement and sea ice drift. In the winter expansion phase, the thermodynamic process of new ice production off the ice edge plays an important role in daily advances of ice cover, whereas daily retreats are mostly due to southward ice drift. On the other hand, both advance and retreat of ice edges in the spring contraction phase are mostly caused by the dynamic process of the ice drift. Based on the above mechanism and the linear relation between the degree of ice production at the ice edge and northward wind speed, the seasonal advance of ice cover can be roughly reproduced using the meridional velocity of ice drift at the ice edge.     

The Levant Slumps and the Phoenician Structures: collapse features along the continental margin of the southeastern Mediterranean Sea

Two distinct series of slumps deform the upper part of the sedimentary sequence along the continental margin of the Levant. One series is found along the base of the continental slope, where it overlies the disrupted eastern edge of the Messinian evaporites. The second series of slumps transects the continental margin from the shelf break to the Levant Basin. It seemed that the two series were triggered by two unrelated, though contemporaneous, processes. The shore-parallel slumps were initiated by basinwards flow of the Messinian salt, that carried along the overlying Plio-Quaternary sediments. Seawater that percolated along the detachment faults dissolved the underlying salt to form distinctly disrupted structures. The slope-normal slumps are located on top of large canyons that cut into the pre-Messinian sedimentary rocks. A layer of salt is found in the canyons, and the Plio-Quaternary sediments were deposited on that layer. The slumps are bounded by large, NW-trending faults where post-Messinian faulted offset was measured. We presume that the flow of the salt in the canyons also drives the slope-normal slumps. Thus thin-skinned halokynetic processes generated the composite post-Tortonian structural patterns of the Levant margin. The Phoenician Structures are a prime example of the collapse of a distal continental margin due to the dissolution of a massive salt layer.     

On the use of poorly soluble hygroscopic substances for modification of warm clouds and fogs

From analysis of the relationships between the equilibrium state of condensation nuclei and the relative humidity, a conclusion is made concerning the preferred use of poorly soluble substances for the generation of artificial condensation nuclei (ACN) designed for modification of warm clouds and fogs with the purpose of their dissipation and precipitation formation. The advantage of poorly soluble substances over commonly used soluble salts is that the finely dispersed part of the spectrum of the poorly soluble ACN does not deliquesce and so is not involved in the formation of cloud droplets. For experimental testing of the conclusions, preference was given to cement, whose main soluble substance is calcium oxide with a solubility of about 1 g/l. The spectrum of dispersed cement particles was measured and compared with the spectra of pyrotechnic flares widely used for modification at present. The process of formation of the cloud droplet spectra was simulated in the aerosol chamber of the Institute of Experimental Meteorology by decreasing the preliminarily generated excess pressure. It was found in these experiments that, compared to the spectra of particles formed on background condensation nuclei, the introduction of dispersed cement leads to the broadening of spectra and to a decrease in the concentration of droplets. Even at the early stage of condensation, droplets with radii of ∼20 μm appear. In this case, no “overseeding” phenomenon is observed, which, for soluble substances, manifests itself in an increase in the concentration of cloud droplets with a large ACN concentration. These effects indicate that, according to the existing concepts about the mechanism of warm-cloud modification with hygroscopic substances, the introduction of poorly soluble ACN (in particular, dispersed cement) below the base of cumulus clouds should stimulate coagulation processes and accelerate rain-formation processes. Considerations are given that the introduction of poorly soluble ACN into the already existing cumulus or stratocumulus clouds or fogs should also result in the acceleration of precipitation-formation processes or cloud dispersal. Comparison of cement powder with the well-known means of warm-cloud and fog modification is carried out. Original Russian Text ? N.P. Romanov, A.S. Drofa, N.S. Kim, A.V. Savchenko, G.F. Yaskevich, 2006, published in Izvestiya AN. Fizika Atmosfery i Okeana, 2006, Vol. 42, No. 1, pp. 80–91.     

Study of the mutual influence of the El Niño-Southern Oscillation processes and the North Atlantic and Arctic Oscillations

On the basis of the nonlinear techniques for the estimation of coupling between oscillatory systems from time series, we investigate the dynamics of climatic modes characterizing global and Northern Hemisphere (NH) processes. The North Atlantic Oscillation (NAO) and Arctic Oscillation indices and the El Niño-Southern Oscillation (ENSO) indices are analyzed in terms of the most reliable data from 1950 through 2004 and earlier data since the 19th century. These indices characterize changes in NH atmospheric pressure (specifically, sea-level pressure in the North Atlantic and NH extratropical latitudes as a whole) and in equatorial Pacific sea-surface temperature and sea-level pressure to which the strongest variations of global surface temperature and global climate on interannual time scales and of regional climatic anomalies in the NH are linked. The methods used are based on phase-dynamics modeling and nonlinear prediction models (a nonlinear version of Granger causality). From both methods and various ENSO indices, the inference about the ENSO effect on the NAO during the latter half of the 20th century and in the early 21st century is made with confidence probability of at least 0.95. The influence is characterized by a time delay of about two years. No inverse influence is found with a similar degree of reliability. Results of estimating the coupling between the ENSO and the NAO depend on the type of index that is used to describe the NAO. The ENSO effect on the NAO is detected with sufficient confidence when the NAO index is chosen to be a larger scale characteristic. However, when a more local index of the NAO is used, no statistically significant coupling to the ENSO is found. Increasing the length of the analyzed ENSO and NAO series (over more than 100 yr) does not lead to any more reliable detection of coupling. Analysis of the data for different time intervals during 1950–2004 has revealed a strengthening of the ENSO effect on the NAO, although this inference is not reliable.     

Transient biouptake flux and accumulation by microorganisms: The case of two types of sites with Langmuir adsorption

The uptake of a chemical species by an aquatic microorganism is modelled considering two kinds of sites where Langmuirian adsorption is followed by first order internalisation kinetics. Simpler models, such as only one internalisation route (while most of the adsorption takes place on non-internalising sites) or a linear isotherm for adsorption on one or both sites, become limiting cases of this double-Langmuirian model. The model considers the sites located on the spherical (or semi-spherical) surface of the organism, and takes diffusion from the medium into explicit account. The numerical solution for the internalisation flux shows a maximum. We provide an estimate for the time needed to reach a certain proximity to steady state. The transient solution confirms that the analytical expressions for the steady-state flux are usually valid and that the accumulated amounts reflect the impact of the short-time uptake. The Instantaneous Steady-State Approximation (ISSA), where an intercept of the linear regression of accumulated amount as a function of time is interpreted as an adsorbed amount, can be critically assessed with the transient numerical code for two cases: (i) when the total burden of metal on the cell is the input data and (ii) when an extraction procedure provides further information on the adsorbed and internalised amount.