对虾养殖生态系不同粒级浮游生物呼吸率和初级生产率测定

1997年6～8月于山东省海阳市黄海集团公司养虾场,用5个实验围隔研究了对虾池不同粒级浮游生物的呼吸率和初级生产率.结果表明:(1)小型、微型及超微型浮游生物的呼吸率平均分别为0.07,0.38及0.31mg/(dm3·d),占各粒级浮游生物总呼吸率的9%,50%及41%.小型、微型及超微型浮游植物的生产率平均分别为0.04,1.26及0.15mg/(dm3·d),占相应粒级浮游植物总生产率的3%,87%及10%.各粒级浮游生物呼吸率占相应粒级浮游植物生产率的比例为:小型浮游生物175%;微型浮游生物30%;超微型浮游生物207%.(2)小型浮游动物、超微型浮游动物(含细菌)的呼吸率显著高于相应粒级浮游植物呼吸率,微型浮游植物的呼吸率明显高于微型浮游动物呼吸率.不同粒级浮游植物呼吸率的大小顺序为微型、超微型、小型,不同粒级浮游动物呼吸率顺序为超微型(含细菌)、微型、小型.     

Formation rates of subtropical underwater in the Pacific Ocean

Water mass formation rates were calculated for subtropical underwater (STUW) in the North and South Pacific by two partially independent methods. One is based on the World Ocean Circulation Experiment (WOCE)/TOGA drifter array over two periods: 1988–1992, and 1992–1996. Drifter velocities were used to calculate two components of the subduction rate, lateral induction and vertical pumping. The second method used CFC-12 data (1987–1994) from WOCE and Pacific Marine Environmental Laboratory to calculate ages on σ_θ surfaces. Subduction rates were estimated from the inverse age gradient. The two subduction rate methods are independent, but they share a common identification of STUW formation area based on satellite-derived surface temperature maps. Using both methods, one can put bounds on the formation rates: 4–5 Sv in the North and 6–7 Sv in the South Pacific. The drifter calculated STUW subduction rates for 1988–1992 and 1992–1996 are 21 and 13 m/yr in the North Pacific and 25 and 40 m/yr in the South. The CFC-12 calculated STUW subduction rate in the North Pacific is 26 m/yr, and 32 m/yr in the South. The South Pacific rates exceed those in the North Pacific. Consistent differences between the two methods support earlier studies, they conclude that mixing contributes to STUW formation in addition to the larger-scale circulation effects. The drifter and tracer rates agree well quantitatively, within 22%, except for the second period in the North Pacific and there are some differences in spatial patterns. Tracer rates integrate over time, and drifters allow analysis of interannual variability. The decrease in subduction rate between periods in the North Pacific is due to negative lateral induction entraining STUW into the mixed layer. The increase in the South Pacific rate is due to an increase in the vertical pumping. Although Ekman pumping is in phase in the North and South, the subduction rate is out of phase. These results confirm that subduction depends on the large-scale circulation and a combination of the outcrop pattern and air–sea fluxes. Temporal differences in rates and partitioning between the hemispheres are consistent with interannual changes in gyre intensity and current positions.     

Patterns and rates of fluid flow during burial diagenesis of the Middle Jurassic Lincolnshire Limestone, eastern England

A phase of ferroan burial calcite from the Middle Jurassic Lincolnshire Limestone exhibits a systematic spatial arrangement of oxygen isotopic characteristics. Mean δ¹⁸O values of the ferroan calcites from each of 15 core and outcrop localities over a study area 25 × 25 km were obtained. These values show a marked depletion from west to east across the study area of approximately 3‰, such that the oxygen isotopic composition of the ferroan calcites can be contoured. The systematic change in oxygen isotopic composition across the study area is believed to have recorded the thermal gradient in the limestone during ferroan calcite precipitation. This thermal gradient can be partially attributed to approximately 200 m of differential burial of the Lincolnshire Limestone across the study area during the Chalk deposition, with a maximum burial of 550 m to the east of the area at this time. A component of up-dip fluid flow (from east to west) through the formation is required to generate the temperature enhancements above those predicted for conduction alone by simple differential burial. Using a finite-difference step computer program, rates of fluid flow during ferroan calcite precipitation are calculated to be approximately 25 m/year. This rate of fluid flow is considerably greater than rates usually predicted for buried sedimentary basins. The causes of such rapid, probably relatively short-lived flow-rates may be the sudden dewatering of adjacent shales, the release of overpressure within the formation of interest, seismic pumping, or fluid circulation round a supracrustal convective loop.     

Generalised synchronisation of spatiotemporal chaos using feedback control method and phase compression

Coupled map lattices are taken as examples to study the synchronisation of spatiotemporal chaotic systems. First, a generalised synchronisation of two coupled map lattices is realised through selecting an appropriate feedback function and appropriate range of feedback parameter. Based on this method we use the phase compression method to extend the range of the parameter. So, we integrate the feedback control method with the phase compression method to implement the generalised synchronisation and obtain an exact range of feedback parameter. This technique is simple to implement in practice. Numerical simulations show the effectiveness and the feasibility of the proposed program.     

Accretion rates in brackish marshes of a Chesapeake Bay estuarine tributary

Vertical accretion rates were determined for brackish marshes in an estuarine tributary on the Eastern Shore of Chesapeake Bay. These rates determined on the basis of the peak phase of early European settlement as recorded in pollen spectra of the marsh sediments range between 0. 18 to 0.74 cm yr⁻¹ over approximately the last 194 years and generally decrease down the estuary. More recent accretion rates (estimated from changes in pine pollen concentration) appear to have accelerated, exceeding the present local rate of sea level rise. The implications for using estuarine marsh accretion rates as surrogates for changes in sea level are discussed.     

GMDH-GEP to predict free span expansion rates below pipelines under waves

ABSTRACT

In this research, group method of data handling (GMDH) as a one of the self-organized approaches is utilized to predict three-dimensional free span expansion rates around pipeline due to waves. The GMDH network is developed using gene-expression programming (GEP) algorithm. In this way, GEP was performed in each neuron of GMDH instead of polynomial quadratic neuron. Effective parameters on the three-dimensional scour rates include sediment size, pipeline geometry, and wave characteristics upstream of pipeline. Four-dimensionless parameters are considered as input variables by means of dimensional analysis technique. Furthermore, scour rates along the pipeline, vertical scour rate, and additionally scour rates in the left and right of pipeline are determined as output parameters. Results of the proposed GMDH-GEP models for the training stages and testing ones are evaluated using various statistical indices. Performances of the GMDH-GEP models are compared with artificial neural network (ANN), GEP, GMDH, and traditional equations-based regression models. Moreover, sensitivity analysis and parametric study are conducted to perceive influences of different input parameters on the three-dimensional scour rates.     

Bed load transport under irregular waves plus current from Monte Carlo simulations of parameterized models with application to ripple migration rates observed in the field

The bed load transport rate under random waves plus current has been predicted for a large range of wave–current conditions. A parameterized model valid for regular waves plus current has been used in Monte Carlo simulations, assuming the wave amplitudes to be Rayleigh distributed. The mean value, standard deviation and numerical estimates of the probability density function of the bed load transport rate are presented for a wide range of wave–current conditions. It appears that overall the effect of the current is dominating the bed load transport rate. Moreover, a significant scatter of the bed load transport rate under random waves plus current is found. Such a scatter is also found in field measurements by Amos et al. [J. Coast. Res. 15 (1999) 1]. Predicted ripple migration rates in the bed load regime have been compared with those obtained from field measurements by Amos et al. [J. Coast. Res. 15 (1999) 1], taking the bed load transport rate to be proportional to the ripple migration rate times the ripple height. Overall, the predictions capture the qualitative as well as the quantitative behaviour of the ripple migration rates in a wide range of wave–current conditions; the ripple migration rates, and thereby the bed load, are predicted within the correct order of magnitude for a wide range of wave–current conditions.     

直接数字频率合成技术在声学释放器中的应用

直接数字频率合成技术(DDS)是一种新的频率合成方法,它具有转换时间短、相位变化连续、全数字可编程等优点.文中介绍了ADI公司生产的AD7008芯片作为频率信号源在声学释放器中的应用.     

Ensuring confidence in radionuclide-based sediment chronologies and bioturbation rates

Sedimentary records of naturally occurring and fallout-derived radionuclides are widely used as tools for estimating both the ages of recent sediments and rates of sedimentation and bioturbation. Developing these records to the point of data interpretation requires careful sample collection, processing, analysis and data modeling. In this work, we document a number of potential pitfalls that can impact sediment core records and their interpretation. This paper is not intended as an exhaustive treatment of these potential problems. Rather, the emphasis is on potential problems that are not well documented in the literature, as follows: (1) the mere sampling of sediment cores at a resolution that is too coarse can result in an apparent diffusive mixing of the sedimentary record at rates comparable to diffusive bioturbation rates observed in many locations; (2) ²¹⁰Pb profiles in slowly accumulating sediments can easily be misinterpreted to be driven by sedimentation, when in fact bioturbation is the dominant control. Multiple isotopes of different half lives and/or origin may help to distinguish between these two possible interpretations; (3) apparent mixing can occur due simply to numerical artifacts inherent in the finite difference approximations of the advection diffusion equation used to model sedimentation and bioturbation. Model users need to be aware of this potential problem. Solutions to each of these potential pitfalls are offered to ensure the best possible sediment age estimates and/or sedimentation and bioturbation rates can be obtained.     

WAVE FORCE ON PIER GROUP

In the case of pier-group structures in offshore engineering construction, the calculation of wave forces on piers is quite complicated due to the wave scattering effect on the piers in group. In this paper, the diffraction problem of two piers with unequal diameters is studied and formulas for calculating wave forces on piers are given on the basis of MacCamy-Fuchs linear wave diffraction theory with a strict consideration on the phase difference between the piers in a pier-group.     

A Three-Point Method for Separating Incident and Reflected Waves over A Sloping Bed

This study presents a three-point method for separating incident and reflected waves to explain normally incident waves' propagating over a sloping bed. Linear wave shoaling is used to determine changes in wave amplitude and phase in response to variations of bathymetry. The wave reflection coefficient and incident amplitude are estimated from wave heights measured at three fixed wave gauges with unequal spacing. Sensitivity analysis demonstrates that the proposed method can predict the reflection and amplitude of waves over a sloping bed more accurately than the two-point method.     

GCM experiments on changes in atmospheric predictability associated with the PNA pattern and tropical SST anomalies

Based on results from a simple three-level quasi-geostrophic model, Lin and Derome suggested that atmospheric predictability is influenced by the Pacific/North American (PNA) pattern. In the present study, predictability experiments are conducted with the Canadian Centre for Climate Modelling and Analysis general circulation model (CCCma GCM). A 47-yr integration of the GCM with specified sea surface temperature (SST) for the years 1948–94 is first performed. Forecasts are initiated whenever the PNA pattern is in a strong positive or strong negative phase during this simulation. For each forecast, an ensemble of six initial conditions is generated with small random perturbations. Forecasts initiated when the PNA is in its positive phase have smaller growth rates of ensemble standard deviation than forecasts initiated when the PNA is in its negative phase. Regional characteristics of the prediction spread are also examined. Similar experiments are conducted to determine the relationship between atmospheric predictability and SST anomalies in the tropical Pacific. Forecasts initiated when tropical SST anomalies are positive have smaller growth rates of ensemble standard deviation than forecasts initiated when tropical SST anomalies are negative. However, cases with positive tropical SST anomalies but without a strong PNA pattern show a similar prediction spread to cases with negative SST anomalies. The results suggest that, in comparison to the PNA pattern, the influence of tropical SST anomalies is only secondary. A set of three-layer diagnostic equations is used to analyze the GCM results. It is speculated that the transient eddies have a stronger influence on the circulation anomalies (and therefore reduce the atmospheric predictability more) in the negative PNA phase than in the positive PNA phase.     

Shallow water temporal coherence of broadband acoustic signals in the presence of internal waves

Temporal coherence is closely related to single path phase rate. The single path phase rates in a shallow water environment were obtained by applying two different multipath models [Dyson, Munk, and Zetler, J. Acoust. Soc. Am., vol. 59, pp. 1121-1133, 1976 and Mikhalevsky, J. Acoust. Soc. Am., vol. 66, pp. 751-762, 1979] on simulated data with internal waves. The estimated phase rates were consistent between the two models. In contrast, previous application of the same models on deep water data showed a factor of 8 difference in their phase rates. The phase rates derived from the models become independent of range after a uniform phase distribution is reached in the (-/spl pi/,/spl pi/) region. The shallow water coherence time varies considerably with depth at a given range. The depth dependence is explained with a correlation function constructed with mode depth functions.     

Characteristics of the boundary layer at the bottom of a solitary wave

The results of direct numerical simulations of the boundary layer generated at the bottom of a solitary wave are described. The numerical results, which agree with the laboratory measurements of Sumer et al. (2010) show that the flow regime in the boundary layer can be laminar, laminar with coherent vortices and turbulent. The average velocity and bottom shear stress are computed and the results obtained show that the logarithmic law can approximate the velocity profile only in a restricted range of the parameters and at particular phases of the wave cycle. Moreover, the maximum value of the bottom shear stress is found to depend on the dimensionless wave height only, while the minimum (negative) value depends also on the dimensionless boundary layer thickness. Diagrams and simple formulae are proposed to evaluate the minimum and maximum bottom shear stresses and their phase shift with respect to the wave crest.     

营养盐因子对龙须菜和菊花江蓠氮磷吸收速率的影响

本文在实验室条件下,研究了营养盐因子对龙须菜和菊花江蓠N、P吸收速率的 影响,分别对不同氮和磷的浓度、氮磷比及不同化合态氮对这两种藻类氮、磷吸收速 率的影响进行了实验与分析．结果表明:在适宜范围内,两种海藻对氮、磷的吸收速率 随介质中氮、磷浓度的增加而增加;不同氮磷对两种海藻N吸收速率的影响不存在 显著差异,但对磷吸收速率的影响非常显著,最高对磷吸收速率在介质的氮磷比为 10:1时;海藻对NH4-N的吸收速率随着NO3-N／NH4-N比的降低而增加,对PO43-P的 吸收速率与对NH4-N的吸收相似,而对NO3-N的吸收速率与对NH4-N的吸收相反．     

Determination of ammonium regeneration rates in the oligotrophic ocean by gas chromatography/mass spectrometry

A method has been developed for the determination of ammonium concentration and isotopic enrichment in seawater samples at the low nanomolar range (10–100 nmol/kg). It is based on the reaction of phenol/hypochlorite with ammonium to form indophenol, with subsequent solid phase extraction, derivatisation and analysis by Gas Chromatography Mass Spectrometry. The precision of the method was maximised by incorporating a deuterated indophenol internal standard. A system was developed which generated seawater with extremely low ammonium concentrations thus matching sample and standard matrices for quantitative analysis. Data are presented from a study of ammonium regeneration rates at three stations in the oligotrophic North–East Atlantic where ambient ammonium concentrations were < 21 nmol/kg. Results suggested that ammonium availability for phytoplankton was limited by the rate of ammonium regeneration. Efficient ammonium assimilation contributed to the very low ambient ammonium concentrations measured at these stations. The study highlights the need for the accurate determination of ammonium regeneration rates in studies of new production, particularly in extreme oligotrophic conditions. If not corrected for isotope dilution, f-ratio estimates may be overestimated by 10.7–13.7%.     

不同饵料搭配对日本对虾人工育苗存活率的影响

本文着眼于生产需求，以螺旋藻粉+虾片+日配饵料0号为Z     

Temporal variations in the deep-water colonization rates of small benthic foraminifera: the results of an experiment on Cross Seamount

Modern benthic foraminifera are important remineralizers of organic matter and a link between surface-ocean production and life in the deep sea. Assemblages of benthic foraminifera are preserved in the fossil record, providing clues to paleoceanographic conditions. These clues can be fully interpreted only when our knowledge of the biology and ecology of modern species is more complete. To study factors influencing foraminiferal colonization rates, artificial substrates were placed on Cross Seamount (18°40′N, 158°17′W) for 1 to 42 months between 1989 and 1994. The colonization rates of benthic foraminifera onto different substrates (five mineral types were used) at four water depths (800, 975, 1285 and 2000 m) were determined. Both calcareous and agglutinated foraminifera inhabited these artificial substrates at different rates. Many of the agglutinated forms colonized at a uniform rate through time. The colonization rates of other foraminifera, primarily calcareous forms, were not constant through time, nor could the variability be attributed to the controlled variables (water depth and substrate composition). Instead, these temporal variations in colonization rate corresponded with shifts in surface ocean conditions and export fluxes in the central Pacific. Other ecological observations are also presented, including size- and spatial-distributions.     

Estimation of net theoretical excavation rates in concrete and sandstone

Abstract

The estimation of excavation rates in specific geological and geotechnical conditions is one of the most delicate aspects for mining and geotechnical operations particularly offshore. Many models have been developed to study the effectiveness of a drilling tool in contact with the ground. In this article, the results of laboratory cutting tests on concrete specimens are shown. The comparison of the results of laboratory tests with different predictive models, helped to identify the most representative models. The models were then used to study in more detail, the effectiveness of the excavation tools through a parametric analysis. The research helped to define how to obtain rubrics, which can estimate the theoretical net cutting production of an excavation machine, when the power of its engines is known, or to evaluate, when the requested net cutting production is available, the power that the cutting machine must have. The findings were also applied to a sandstone previously investigated. The results are based on theoretical models and cannot be used on geomaterials with the same (or similar) geotechnical properties.     

On the determination of the mesh size for numerical simulations of shock wave propagation in near field underwater explosion

It is well known that the accuracy of mesh-based numerical simulations of underwater explosion strongly relies on the mesh size adopted in the analyses. Although a numerical analysis of underwater explosion can be performed with enough accuracy by using considerably fine meshes, such fine meshes may lead to substantially increase in the CPU time and the usage of computer memory. Thus, how to determine a suitable mesh size in numerical simulations is always a problem confronted when attempting to study the shock wave propagation resulting from underwater explosion and the subsequent response of structures. Considering that there is currently no universally accepted method for resolving this problem, this paper aims to propose a simple method to determine the mesh size for numerical simulations of near field underwater explosion. To this end, the mesh size effects on the shock wave propagation of underwater explosion are carefully investigated for different charge weights, through which the correlation between mesh sizes and charge weights is identified. Based on the numerical study, a dimensionless variable (λ), defined as the ratio of the radius of charge to the side length of element, is introduced to be the criterion for determining the mesh size in simulations. It is interesting to note that the presented method is suitable for various charge weights. By using the proposed meshing rule, adequate balance between solution accuracy and computational efficiency can be achieved for different blast scenarios in numerical simulations of underwater explosion.