Real scalar field scattering in the nearly extremal Schwarzschildben de Sitter space

Reasonable approximations are introduced to investigate the real scalar field scattering in the nearly extremal Schwarzschild--de Sitter (SdS) space. The approximations naturally lead to the invertible x(r) and the global replacement of the true potential by a P?shl--Teller one. Meanwhile, the Schr?dinger-like wave equation is transformed into a solvable form. Our numerical solutions to the wave equation show that the wave is characteristically similar to the harmonic under the tortoise coordinate x, while the wave piles up near the two horizons and the wavelength tends to its maximum as the potential approaches to the peak under the radial coordinate r.     

VORTEX SHEDDING FROM A CIRCULAR CYLINDER IN OSCILLATORY FAR FLOW

By using a process of successive approximations, the Boundary-Layer equations are solved to determine the separation points of a circular cylinder in oscillatory flow under the conditions of vortex existing. Combining with the discrete vortex model, the separation points and the fluid force coefficients are calculated at different KC numbers and Re numbers, A modified Morison equation is used in calculating the inline forces, and good agreements are obtained between the calculated results and those from other's experiments.     

Exact distributions for apparent waves in irregular seas

We discuss the long-run distributions of several characteristics for the apparent waves in a Gaussian sea. Three types of one-dimensional wave records are considered: 1) the seaway in time at a fixed position; 2) the instantaneous profile along a horizontal line; 3) the encountered seaway. Exact integral forms of the joint long run distributions are derived for the apparent periods, lengths, and heights. Results of numerical approximations of these distributions are presented in examples. For the computations we considered, as the input spectra, empirical estimates of the frequency spectra as well as JONSWAP type spectra. Effective algorithms are discussed and utilized in the form of a comprehensive computer package of numerical routines.     

A review of the analyses of ocean wave groups

The most common parameters and functions used to characterize wave groups in linear seas are reviewed and interrelated in a unified manner. A three-axes representation of run lengths is used to characterize wave groups using exponential and Markov chain approximations. A relationship between four parameters (Q_p, Q_e, κ², and ρ²) and the correlation coefficient between consecutive wave heights [r_HH(1)] is demonstrated. The wave-height function method is reviewed in some detail in order to relate the run length theory with envelope theories. The theoretical estimates used to demonstrate the relationships between the various parameters must be considered as only first-order trends to parameter estimates computed from real wave data due to the statistical variability in these estimates when computed from real wave data.     

Zooidal budding in the cheilostomatous bryozoan Fenestrulina malusii var. thyreophora

Zooidal budding in Fenestrulina malusii var. thyreophora is described and notes on the budding of Micropora mortenscni are included for comparison. In both, an autozooidal bud arises from a membranous window in the exterior wall of a dietella. Dietellae themselves arise by being delimited as dichotomies of the developing lateral walls of autozooids. Because of the structural discreteness of dietellae of Fenestrulina and Micropora, and Hastings’ (1963) observation that some dietellae of Microporella occur as avicularia, dietellae in the Microporellidae and Micropora are regarded as fully formed heterozooids and not merely as incipient zooid buds, as lateral septulae are. The formation of dietellae in Fenestrulina and Micropora is a continuous process, and comparable with the con‐strictive budding of distal autozooids of Membranipora and Metrarabdotos.     

On the largest wave height in water of constant depth

Experimental evidence of the fact that, both in the laboratory and in the field, the largest wave height to water depth ratio realisable for oscillatory waves propagating in water of constant depth is about 0.55, has been published recently (Nelson, 1985); (Nelson, 1987); (Nelson, 1994). This paper presents various theoretical approaches to estimate this maximum value. In particular, the higher approximations of the Stokes and cnoidal theories give a much higher limiting wave height, close to 0.78 h, which is commonly used in engineering practice.However, the inclusion of higher harmonics, generated by a wave-maker paddle, into the analysis provides maximum wave height less than ≈ 0.6 h, which is in good agreement with observations.     

On the local equilibrium of winds and wind-waves in relation to surface drag

Local equilibrium of winds and wind-waves is discussed as a basis for research of the drag coefficient of the water surface as well as for the spectral growth of wind-waves. This hypothesis assumes, in a narrow sense, that statistical properties are determined from four physical quantities, which represent winds and wind-waves: the friction velocityu _*, the gravitational accelerationg, the powerE of the surface displacement, and the peak frequency _p of a wind-wave spectrum. Then one has only one nondimensionalcontrol parameter, which may be either the wave age or wave nonlinearity (slope) of dominant waves. In a wide-sense, one can take into account viscosity and surface tension in terms of one more additional parameter by virtue of the virtual invariance of those material constants; that parameter describes the scale ratio between dominant waves and the short waves for which viscosity or surface tension is important. A unified expression for the roughness height according to this hypothesis turns out to include Charnock's and Toba's formulas as special cases. On the basis of a preliminary analysis of the experimental data, a new empirical formula is proposed.     

Numerical Experiments of Isolated Convection under Polynya

The dense water formation process under polynya or lead is examined by numerical experiments using a three-dimensional non-hydrostatic model. Many numerical experiments on isolated convection in an initially homogeneous fluid have been performed for different sets of external parameters, in order to investigate a relationship between the convection process and the external parameters. The main focus is on the situation in which the horizontal length scale of disk-shaped buoyancy forcing (radius R) is comparable with the total water depth (H). The two dynamical regimes described in previous work—the baroclinically unstable convection and the baroclinically stable convection—are confirmed in the experiments. A horizontal shift of a convective chimney is important to a density anomaly in baroclinically stable convection. For the stable range, as R is reduced R/H < 0.7, a new regime is found, called “single-plume convection”, in which multiple convective plumes do not fully develop, and the density anomaly scale has nearly no dependency on R. This change of dependency on R is consistent with that derived by scaling analysis. The non-hydrostatic component is more significant than the hydrostatic one in the single-plume convection. The information obtained is useful for parameterizing dense water formation under ice cover in a numerical model with a large grid size; i.e., the newly formed water has a density anomaly independent of the polynya size smaller than the water depth, while the anomaly increases as the size exceeds the depth.     

Investigation of the sensitivity of the Mellor–Yamada parametrization to the choice of finite-difference analogs in a numerical three-dimensional model of the operative prediction of currents in the black sea

Within the framework of the Mellor–Yamada approach, we realize a numerical scheme for the calculation of the coefficients of turbulent viscosity and diffusion in the z -system of coordinates for the three-dimensional model of operative prediction of currents in the Black Sea. Some discrete analogs of the equations for turbulent kinetic energy and turbulence macroscale are studied. Their high sensitivity to the choice of finite-difference approximations is demonstrated. On the basis of the comparison of the results of prognostic experiments with the data of observations, we choose the best approximation of the term used to describe the generation pf turbulence energy.     

Numerical experiments on estimating the accuracy of four-dimensional analysis of hydrophysical fields using a quasi-geostrophic model of currents

The relationship between the results of four-dimensional (4-D) analysis and the approximations employed in the assimilation scheme, as well as the initial fields, is studied. The contribution made by a procedure of correcting the horizontal velocities by theT, S data to the increase of the quality of the data obtained is estimated. Numerical experiments were carried out on the data of measurements made in the observation site located in the Newfoundland energy-active zone in August 1985.Translated by Mikhail M. Trufanov.     

海带多因子生长模型建立研究

大型藻类在生长过程中吸收氮磷营养物质并进行光合作用,从而发挥生态修复和固定二氧化碳的重要作用。海带作为兼具经济价值和生态价值的典型大型藻类,其重要性不言而喻。本研究以海带（Saccharina japonica）为研究对象,以VENSIM可视化软件为平台,通过建立多种环境因子与海带生长的函数关系,构建海带多因子生长数学模型。结果表明,所建模型能够较好的模拟海带在不同环境条件下的生长状态。通过Morris函数计算了模型中各参数的灵敏度,分析了光照、温度和氮磷营养盐对海带生长的影响。研究发现：在海带养殖初期,受光照影响最大;在临近收获期,受高温的限制更为明显。除了养殖规模和养殖密度都比较大的海域,氮磷营养盐一般不会对海带生长产生抑制性影响,当营养盐成为限制因素时,氮营养盐的抑制性影响要大于磷。本研究所建模型可以对不同海区海带的生长状况和影响因素进行模拟和分析,从而为海带养殖海域的管理提供参考和借鉴。     

Approximations to directivity for linear, planar, and volumetricapertures and arrays

Even after decades of sonar design, approximations to the directivity factor (DF) or index of an array, are often used inappropriately. Many of the approximations commonly used provide accurate directivity approximations for only the simplest of array geometries. As the array's size, shape, weighting, and complexity increase, there is a renewed need for better directivity approximations. Directivity is defined as the ratio of the output signal-to-noise (SNR) of an array to the input SNR at an omnidirectional element in a spherically isotropic noise field. Calculation of directivity is obtained by integrating the magnitude-squared response of the array over all angles of incidence. In spherical coordinates, these arrival angles are denoted by an azimuthal angle &thetas; and a polar angle φ. Hence, calculation of the directivity requires a two-fold integration over the angular space defined by the azimuthal and polar angles. For complex, large-size arrays consisting of thousands of array elements, directivity calculations using numerical integration procedures can be time consuming, even on state-of-the-art computing systems. This report provides a number of accurate formulas for estimating the directivity of linear, planar, and volumetric apertures and arrays, which are allowed to have arbitrary shading coefficients, steering angles, and directional array element responses     

Global parameter estimation of the Cochlodinium polykrikoides model using bioassay data

Cochlodinium polykrikoides is a notoriously harmful algal species that inflicts severe damage on the aquacultures of the coastal seas of Korea and Japan. Information on their expected movement tracks and boundaries of influence is very useful and important for the effective establishment of a reduction plan. In general, the information is supported by a red-tide(a.k.a algal bloom) model. The performance of the model is highly dependent on the accuracy of parameters, which are the coefficients of functions approximating the biological growth and loss patterns of the C. polykrikoides. These parameters have been estimated using the bioassay data composed of growth-limiting factor and net growth rate value pairs. In the case of the C. polykrikoides, the parameters are different from each other in accordance with the used data because the bioassay data are sufficient compared to the other algal species. The parameters estimated by one specific dataset can be viewed as locally-optimized because they are adjusted only by that dataset. In cases where the other one data set is used, the estimation error might be considerable. In this study, the parameters are estimated by all available data sets without the use of only one specific data set and thus can be considered globally optimized. The cost function for the optimization is defined as the integrated mean squared estimation error, i.e., the difference between the values of the experimental and estimated rates. Based on quantitative error analysis, the root-mean squared errors of the global parameters show smaller values, approximately 25%–50%, than the values of the local parameters. In addition, bias is removed completely in the case of the globally estimated parameters. The parameter sets can be used as the reference default values of a red-tide model because they are optimal and representative. However, additional tuning of the parameters using the in-situ monitoring data is highly required.As opposed to the bioassay data, it is necessary because the bioassay data have limitations in terms of the in-situ coastal conditions.     

Long-term effects of a toxic algal bloom on subtidal soft-sediment macroinvertebrate communities in Wellington Harbour, New Zealand

The long-term effects (>1 year) of a naturally occurring toxic plankton bloom (Karenia brevisulcata) on subtidal benthic macroinvertebrate communities were investigated in Wellington Harbour, a semi-enclosed temperate embayment in New Zealand. For 3 years communities were sampled at three different sites in the harbour. Analyses revealed that community recovery following the bloom was site-specific. Multivariate analyses indicated that at one site community composition was approaching recovery 3 years post-bloom. At the second site, a sequential recovery process was indicated, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The nature of the hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and differed little in their composition pre- and post-bloom, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom and exhibited temporal differences in composition consistent with successional models. Complete recovery to a pre-disturbance climax community dominated by K-selected species is likely to take 4–5 years, if not interrupted by other disturbances. Given the increased occurrence of harmful algal blooms worldwide, more monitoring and manipulative studies are needed to further evaluate the effects of such disturbances on macrobenthic communities.     

Inter‐ and intra‐colonial genotypic diversity in hermatypic hydrozoans of the family Milleporidae

Genetic diversity is the basis for adaptation and therefore of primary scientific interest, especially in species that are threatened by anthropogenic challenges, e.g. climate change and/or pollution. Coral reefs are among the most threatened but also the most diverse ecosystems and have therefore been studied quite extensively. So far, most investigations have focused on scleractinian corals while the equally important reef builders, the hydrozoans, have been less considered. Here we provide the first study of genotypic variability as well as intra‐colonial genetic variability, the co‐occurrence of more than one genotype within a single colony, in Milleporidae based on microsatellites. We analysed two geographically distinct populations from the Millepora dichotoma complex, one from the Red Sea and one from the Great Barrier Reef. Additionally, a population of Millepora platyphylla was analysed from French Polynesia. We compared microsatellite multilocus genotypes and cytochrome c oxidase subunit I haplotypes for each of the three field sites to detect levels of genotypic diversity at the intra‐ and inter‐specific levels. Furthermore, we examined all species for the occurrence of intra‐colonial genetic variability, a recently described mechanism in scleractinian corals that might enhance the adaptive potential of sessile organisms. We found both species and all field sites to be genotypically variable. Twelve mitochondrial haplotypes and 27 multilocus microsatellite genotypes were identified. In addition, intra‐colonial genetic variability was detected in the M. dichotoma complex from the Great Barrier Reef as well as in M. platyphylla from French Polynesia. All of the intra‐colonial genetically variable colonies consisted of one main genotype and a second divergent genotype caused by somatic mutations (mosaicism). Our study proves that Milleporidae are genetically variable and that the phenomenon of intra‐colonial genetic variability also occurs in this important reef‐building family.     

瘤背石磺体内重金属铜和镉的净化研究

为降低瘤背石磺(Onchidium struma)体内超标重金属铜和镉的含量,保证其食品安全,作者通过底泥添加木鱼石土(富含锌、硒等)、饲料添加蛋白核小球藻(Chlorella pyrenoidosa)粉以及维生素C对瘤背石磺体内Cd和Cu进行净化,探究不同实验组对瘤背石磺体内Cd和Cu的净化效果。结果表明,对照组单纯用玉米粉暂养对瘤背石磺重金属的排出有一定的效果,但远远低于试验组在底泥中添加木鱼石土、在饲料中添加蛋白核小球藻粉及维生素C的效果。在瘤背石磺产品生产过程中,通过在底泥中添加木鱼石土、在饲料中添加蛋白核小球藻粉及维生素C能高效地降低其体内重金属铜和镉的含量,达到可食用的目的,保证食品安全。     

Analysis of primary production in the Seto Inland Sea, Japan, using a simple ecosystem model

A simple model of lower trophic level ecosystem has been created to analyze possible environmental control of primary production in eight sub-areas of the Seto Inland Sea. The primary production rates observed by Hashimotoet al. (1997a) in these sub-areas are well reproduced by the model, including horizontal processes such as horizontal transport of nutrients and vertical processes such as vertical mixing, light intensity and sinking of particulate matter. Without taking account of horizontal processes the model also successfully reproduces the observed primary production rates in some areas, but if fails to reproduce those in the others. This shows that the relative importance of the horizontal transport on the primary production differs are by area. Two time scales,T _z andT _H, are introduced to explain this difference.T _z is a vertical cycling time of material, which is defined as the time during which the stock of the material in the water column is utilized for primary production;T _H is the horizontal transit time of the material. The relative importance of the horizontal process is well explained by theT _H/T _z ratio; that is, the horizontal transport process is important in the areas where this ratio is small. Further the possible mechanisms of nutrient supply for the primary production in each sub-area are investigated using this model.     

Effects of irradiance on pigment signatures of harmful algae during growth process

Three harmful algal bloom (HAB) species, Phaeocystis globosa, Thalassiosira rotula, and Proro-centrum donghaiense were isolated from the coast of China and cultured in batches at three light intensities (40, 70 and 150 μmol photons·m^-2·s^-1). The variation patterns of cell numbers and growth rates with light intensity during growth process were different among species. In P. globosa and T. rotula, maximum growth rates were found at 150 μmol photons·m^-2·s^-1 and ranged from 0.60 divisions per day in T. rotula, to 1.17 divisions per day in P. globosa. The highest growth rate of P. donghaiense, however, was found at 70 μmol photons·m^-2·s^-1 (0.36 divisions per day). In general, all the three HAB species showed adaptation to increasing light intensity by decreas-ing cellular concentrations of chlorophyll a (Chl a), but the variation patterns during the growth process were species-specific. The cellular concentrations of Chl a in P. donghaiense and T. rotula increased gradually with incubation time, but the opposite trend was found in P. globosa. Most of the pigment ratios and pigment indices of these three species were nearly constant during the growth process and showed small changes at different light intensities illustrating the applicability of chemotaxonomy during the initial and developing stages of HAB events, which is very important to study the ecological issues related to HAB species. Ratios of photoprotective carotenoids, such as diadinoxanthin, diatoxanthin and β,β-carotene to total chlorophylls a (Tchl a) showed the trend of increasing with the increase of light intensity during growth process. The species-specific and pigment-specific variations in pigment ratios/indices at different light intensities during growth pro-cess probably reflected the differences in the pigment composition as well as the adaption capabilities of different species to the changes of physical conditions.     

Scour effects on bearing capacity of composite bucket foundation for offshore wind turbines

Abstract

Composite bucket foundation (CBF) is a wide-shallow foundation for offshore wind turbines, which can be transported and installed with the turbine as one unit at a one-step operation. Compared with deep pile foundations, its structural stability is more sensitive to the scouring by waves and currents. In this paper, a three-dimensional finite element model with CBF and surrounding soil is established to estimate the failure mode at different given soil scour conditions. The loading on CBF for offshore wind turbines is characterized by relatively small vertical loading V, larger horizontal loading H, and bending moment M, and the effect of erosion on bearing capacity of CBF is determined by using the fixed displacement ratio method. In addition, the failure envelopes of the CBF applied in H–M and V–H–M loading modes are obtained. Results indicate that the bearing capacity of CBF under horizontal loading and bending moment will be significantly reduced by the decrease in the embedded depth of CBF due to the scouring depth and extent, as well as the H–M, and V–H–M failure envelopes. The structural stability safety factor of CBF under different scouring conditions can be obtained through the three-dimensional envelope surface with respect to scouring depth and extent.