Aerodynamic characteristics of a hybrid trimaran model     

Konstantin I. Matveev  Victor A. Dubrovsky 《Ocean Engineering》2007,34(3-4):616-620

Ultra fast marine vehicles can substantially benefit from aerodynamic unloading. The subject of this study is aerodynamics of a hybrid trimaran that comprises three wave-piercing planing hulls and a wing-shaped superstructure. This configuration is characterized by high efficiency and good seaworthiness at speeds about twice those of contemporary fast ferries and combat ships. Aerodynamic coefficients of the above-water structure of the hybrid trimaran were measured in a wind tunnel. A computer code based on the vortex lattice method is applied for modeling steady aerodynamics of this structure in a range of attack angles. The application of an interceptor at the pressure side of the wing is shown to produce significant increase in aerodynamic lift.  相似文献   

Distribution of Sessile Invertebrates
in a Rocky Sublittoral Community off Rimsky‐Korsakov Islands (Sea of Japan)     

Konstantin S. Tkachenko  Alexey V. Zhirmunsky 《Marine Ecology》2002,23(3):253-267

Abstract. The dependence of the vertical distribution of sessile macrobenthos upon environmental physical factors was studied in a community inhabiting rocky substrata at 2 to 15 m depth near the Rimsky‐Korsakov Islands (Peter the Great Bay, Sea of Japan). Three separate groups of species were distinguished within this community. The main dominant species are the anthozoan Metridium senile and the mussel Crenomytilus grayanus. Water movement, bottom inclination and topographic position of the studied sites in respect to prevailing water flows influence the spatial structure of sessile invertebrates. No vertical zonation in the scale of the studied sublittoral area below the 2 m depth level was observed. The studied factors are believed to condition the observed mosaic of patches characterized by specific composition, with a single species being dominant.  相似文献   

Lunar fortnightly modulation of tidal mixing near Kashevarov Bank, Sea of Okhotsk, and its impacts on biota and sea ice     

Konstantin A. Rogachev  Eddy C. Carmack  Alexander S. Salomatin  Marina G. Alexanina 《Progress in Oceanography》2001,49(1-4)

Here we examine the consequences of strong tidal mixing on spatial and temporal distributions of biota and sea ice above Kashevarov Bank, Sea of Okhotsk, using data from field surveys (hydrography, pressure gauge and current meter moorings, and bio-acoustic soundings) and remote sensing (NOAA AVHRR). Fortnightly variations in the amplitude of diurnal tidal currents, primarily resulting from the K₁–O₁ interaction, are shown to dominate water motion over the bank. These currents (with maximum velocities 2 m s⁻¹) create a sharp tidally-mixed front that separates well-mixed water above the bank from stratified water along its flanks. Such mixing draws water upward from the cold dichothermal layer (100–150 m) into the surface layer, and thus serves to ventilate the intermediate layers of the Sea of Okhotsk. In summer, fortnightly modulation of the tidal mixing creates temporal variations in water column stratification, a critical factor in the joint supply of nutrients and light required to sustain phytoplankton growth. As such, chlorophyll-a and oxygen values vary in response to the fortnightly cycle, and zooplankton likewise form dense aggregations within the tidally-mixed front in response to the phytoplankton production. It is further noted that the brood cycle of dominant zooplankton species on the bank matches the fortnightly modulation of the tidal currents. In winter, tidal mixing draws relatively warm water upward from mid-depth to maintain a polynya that cyclically opens and closes in response to fortnightly variation in vertical heat flux.  相似文献   

Impact of repetitive thermal anomalies on survival and development of mass reef‐building corals in the Maldives          下载免费PDF全文

Konstantin S. Tkachenko 《Marine Ecology》2015,36(3):292-304

The distribution of dominant coral genera and their response to the recent sea temperature anomalies in the last three decades are analyzed across reefs of the Maldivian Archipelago, which spans 860 × 120 km in the central Indian Ocean. The Maldives suffered one of the worst coral mortality rates in the Indian Ocean in the 1998 warming event and experienced two sub‐lethal thermal anomalies in 2003 and 2010. The results showed that the Acropora proved an important driver of post‐1998 recovery and has become a major dominant genus in most Maldivian reefs at present. The average coral cover and proportion of acroporids have decreased from south to north and represent correspondently 70.6/59% for the southern atoll, 62/53% for the central atoll and 33/10.3% for the northernmost atoll. Stylophora, Seriatopora and the hydrocoral Millepora were not found and are considered candidates for local extirpation from the Maldives. Higher thermal variability and frequency of thermal stress might lead to the decrease in the abundance of susceptible taxa in the northernmost atoll. No phase‐shift to algae‐dominated reefs was observed in any of the three locations. Factors contributing to coral recovery and acclimatization are discussed.  相似文献   

Thorite versus huttonite: stability, electronic properties and X-ray emission spectra from first-principle calculations     

Igor R. Shein  Konstantin I. Shein  Alexander L. Ivanovskii 《Physics and Chemistry of Minerals》2006,33(8-9):545-552

The structural, electronic properties and stability of thorium orthosilicate ThSiO₄ polymorphs: thorite and huttonite are investigated by means of the full-potential linearized augmented-plane-wave method with the generalized gradient approximation for the exchange-correlation potential (FLAPW-GGA). The forbidden gaps of thorite and huttonite are estimated at about 7.8 and 7.6 eV, respectively. It is found that Th5f states in ThSiO₄ partially overlap with occupied O2p bands. The data obtained showed that thorite is more stable than huttonite; in turn both ThSiO₄ polymorphs are unstable with respect to their constituent binary oxides (thorianite ThO₂ and α-quartz SiO₂) in agreement with the experiments. The theoretical shapes of X-ray emission (XES) (Si,O)Kα,β spectra for thorite, huttonite as well as for SiO₂ and ThO₂ are calculated and discussed. We show that the XES spectroscopy near the (Si,O)K edge may be very useful technique not only for detailed investigation of the bulk-electronic structure of Th silicates but also for the phase analysis of complex mineral samples containing these species.  相似文献   

Relaxation time distribution from time domain induced polarization measurements   总被引：3，自引：0，他引：3  

Andrey Tarasov  Konstantin Titov 《Geophysical Journal International》2007,170(1):31-43

We propose an algorithm for inverting time domain induced polarization data to a relaxation time distribution. The algorithm is based on the (Tikhonov) regularized solution of the 1^st kind Fredholm integral equation. We test the algorithm on synthetic data, and show its robustness for a noise level, typical of laboratory time domain measurements. We also show that, for the inversion purpose, the time domain data must be obtained with the different current wavelengths. We then test the algorithm on the experimental data recently obtained on brine-saturated medium-grained quartz sand (average grain diameter of 4 × 10⁻⁴ m), and on sand mixtures. For the medium-grained sand, relaxation time distribution contains a main peak at 25 s. Different amounts (3%, 8% and 12%) of fine-grained quartz sand (average grain diameter of 1.12 × 10⁻⁴ m) were added to the medium-grained quartz sand. For the sand mixture, an additional peak is observed in the relaxation time distributions, in the time range from 1.0 to 2.5 s. The magnitude of the second peak increases with the increase of the fine-grained sand content. Therefore, the experimental data show that peaks in the relaxation time distributions are related to the grain size. On the basis of the known peak location, and of the known grain size value, we obtained the values of the diffusion coefficient, which were found to be of the same order of magnitude as those in the bulk solution.  相似文献   

Suitability of biogenic carbonate of Lithospermum fruits for C dating     

Konstantin Pustovoytov  Simone Riehl 《Quaternary Research》2006,65(3):508-518

Lithospermum (Boraginaceae) belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits. In this genus, carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp. Fossil Lithospermum fruits (nutlets) with well-preserved calcified tissues commonly occur in Quaternary sediments and cultural layers. We tested the suitability of biogenic carbonate of Lithospermum fruits for radiocarbon dating using a total of 15 AMS measurement results from four modern and 11 fossil samples. The ¹⁴C data from modern samples suggest that Lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets. In general, the ages determined through ¹⁴C dating of fossil fruitscorresponded well with the absolute-age intervals for archaeological sites over the last 5000 yr. Biogenic carbonate of Lithospermum fruits, like that of Celtis, represents a new source of chronological information for late Quaternary studies.  相似文献   

NMR relaxation measurements of biofouling in model and geological porous media   总被引：1，自引：0，他引：1  

Sarah L. Codd  Sarah J. Vogt  Jennifer A. Hornemann  Adrienne J. PhillipsJames E. Maneval  Konstantin R. Romanenko  Logan HansenAlfred B. Cunningham  Joseph D. Seymour 《Organic Geochemistry》2011,42(8):965-971

Recently 2D nuclear magnetic resonance (NMR) relaxation techniques have been able to access changes in pore structures through surface and diffusion based relaxation measurements. This research investigates the applicability of these methods for measuring pore and surface changes due to biofilm growth in various model porous systems and natural geological media. Model bead packs of various construction containing 100 μm borosilicate and soda lime glass beads were used to demonstrate how changes in the measured relaxation rates can be used to non-invasively verify and quantify biofilm growth in porous media. However significant challenges are shown to arise when trying to implement the same techniques to verify biofilm growth in a natural geological media.  相似文献   

Convergence of Liapunov series for Huygens–Roche Figures     

Konstantin V. Kholshevnikov  Sergei L. Kurdubov 《Celestial Mechanics and Dynamical Astronomy》2004,89(1):83-96

According to the classical theory of equilibrium figures, surfaces of equal density, potential and pressure concur (let us call them isobars). Isobars can be represented by means of Liapunov power series in small parameter q, up to the first approximation coinciding with the centrifugal to gravitational force ratio at the equator. Liapunov has proved the existence of the universal convergence domain: the above mentioned series converge for all bodies (satisfying a natural condition that the density ρ decreases from the center to the surface) if |q| < q*. Using Liapunov’s algorithm and symbolic manipulation tools, we have found q*= 0.000370916. Evidently, the convergence radius q* may be much greater in common situations. To comfirm it it is reasonable to consider two limiting and one or two intermediate cases for the density behaviour: ρ is a constant, the Dirac’s δ-function, linear function of the distance from the center, etc. And indeed, in the previous paper we find a three orders of magnitude greater value for homogeneous figures. In the present paper we find that in the opposite case of Huygens-Roche figures (a point-mass surrounded by a weightless atmosphere) the convergence radius is unexpectedly large and coincides with the well-known biggest possible value q*= 0.541115598 for such a class of figures. To ascertain it we ought to use numerical calculations, so our main result is demonstrated by means of a computer assisted proof. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The compressibility of Fe- and Al-bearing phase D to 30 GPa     

Konstantin D. Litasov  Eiji Ohtani  Akio Suzuki  Kenichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(3):159-167

High-pressure in situ X-ray diffraction experiment of Fe- and Al-bearing phase D (Mg_0.89Fe_0.14Al_0.25Si_1.56H_2.93O₆) has been carried out to 30.5 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch–Murnaghan equation of state to the P–V data yields values of V ₀ = 86.10 ± 0.05 ų; K ₀ = 136.5 ± 3.3 GPa and K′ = 6.32 ± 0.30. If K′ is fixed at 4.0 K ₀ = 157.0 ± 0.7 GPa, which is 6% smaller than Fe–Al free phase D reported previously. Analysis of axial compressibilities reveals that the c-axis is almost twice as compressible (K _c  = 93.6 ± 1.1 GPa) as the a-axis (K _a  = 173.8 ± 2.2 GPa). Above 25 GPa the c/a ratio becomes pressure independent. No compressibility anomalies related to the structural transitions of H-atoms were observed in the pressure range to 30 GPa. The density reduction of hydrated subducting slab would be significant if the modal amount of phase D exceeds 10%.  相似文献