共查询到20条相似文献，搜索用时 15 毫秒
1.
针对当前水深自动选取中水深点与岸线的协调匹配问题,提出了一种与岸线协调的水深自动选取方法。通过分析资料水深点与岸线的平面位置关系,提取出与岸线协调的待选水深点;从航海安全角度考虑,优先选取浅水深点;在此基础上,分别定义水深点与岸线弯曲处、平直处的协调度,并建立协调度评估模型;通过定量计算协调度,选取出与岸线协调匹配的水深点。实验结果表明,所提方法能在岸线弯曲处优先选取出协调的水深点,同时能保证在岸线平直处附近所选取的水深点分布合理;所提方法能够较好地考虑水深点与岸线的图上位置关系,避免水深注记中断岸线、水深注记"上陆"的情况出现。 相似文献
2.
EPSONDE is a tethered free-fall profiling system used to obtain temperature microstructure and velocity turbulence data to a depth of at least 1500 m. EPSONDE, which carries a variety of slow and fast sensors, is deployed on a loose kevlar multiconductor cable by a specialized wire-handling system. Data are transmitted from this underwater unit (1792 samples per second) to a shipboard system which includes a dedicated microcomputer for data logging and online data processing. The performance of this system is demonstrated by discussing a study of turbulent mixing processes in a lens of Mediterranean water (a MEDDY) found at a depth of 1000 m in the Canary basin. These studies indicate that turbulent kinetic energy dissipation may be an important mechanism in determining the decay and lifetime of a MEDDY 相似文献
3.
Results of laboratory studies of the damping of gravity–capillary waves on a water surface covered with a film of petroleum product (diesel fuel) in a wide range of change in a film thickness are presented. A nonmonotonic dependence (with a local maximum) of a damping coefficient on film thickness is discovered. Numerical calculations of the dispersion equation for gravity–capillary waves in the presence of a viscoelastic film of arbitrary thickness, which confirmed the existence of the maximum of the damping coefficient as a function of film thickness, are performed. Based on a comparison of the calculation results and the data of laboratory measurements of wave characteristics, the values of parameters in the diesel fuel films are estimated in a wide range of a change in their thickness. 相似文献
4.
From the results of a parameter optimization process based on a “minimum feasible volume” criterion, it is shown that the optimum shape for a transatlantic, deep-diving, autonomous submersible is a “low drag” hull shape with a displaced volume of 4.4 m3, a length of 5.97 m and a maximum diameter of 1.33 m. Calculations show that a vehicle of these dimensions, travelling in a minimum drag “cruise” configuration at a depth of 3000 m, say, and at a velocity of 2.5 m/sec could have a maximum range of 7000 km provided the “hotel” power consumption is kept low. 相似文献
5.
Satoshi Sakai 《Progress in Oceanography》1986,17(3-4)
Laboratory experiments with a rotating tank confirm the bifurcation character of a barotropic flow driven by an inflow and an outflow described by Sakai (1986). The model, a circular basin with a topographic β-effect, simulates a mid-latitude oceanic feature. At a low Rossby number, stationary Rossby waves are observed which are symmetrical with a line connecting the inlet and the outlet. As the Rossby number increases, a bifurcation occurs and two kinds of vortex flows are observed. In the vortex, potential vorticity is almost uniform. In addition to the two vortex flows, a jet-like inertial flow can also be observed. In general, thre results of these experiments agree well with those of a low-order model and a numerical model. 相似文献
6.
This paper investigates a wavefilter which could effectively eliminate re-reflected waves generated in a wave flume over a certain range of wave periods. The wavefilter is not required to change its thickness for different incoming wave periods and is, therefore, termed here a permanent wavefilter. The structure comprises of a set of multilayer porous media. Their related properties such as porosities, friction factors and thickness are sought with the hope of developing a structure which could serve the desired purpose.A theoretical study has been performed. It was found that a multilayer porous media could eliminate re-reflected waves without resorting to adjusting the medium property whenever wave period changes, only if the thickness of the media has to exceed a certain amount.Generally speaking, a thicker multilayer porous media is needed for longer-period waves, while a thinner one is suitable for shorter-period waves. The wavefilter considered here could serve both eliminating re-reflected waves and also providing a desired median wave height if all of those related factors of the media have been properly selected and if the generated waves are restricted to not too wide a range of wave periods. However, it is unlikely that a wavefilter with fixed thickness can remain effective over too wide a range of wave period. 相似文献
7.
I. P. Chunchuzov S. N. Kulichkov O. E. Popov V. G. Perepelkin 《Izvestiya Atmospheric and Oceanic Physics》2010,46(5):597-607
A wave theory of propagation of an acoustic pulse in a moving stratified atmospheric layer above the ground with a finite
impedance of an underlying ground surface is developed. The shapes of acoustic signals in a near-ground atmospheric waveguide,
which are formed due to temperature inversion and a vertical shear of the wind velocity, are calculated based on this theory.
These signals are compared with those measured during the experiments where vertical profiles of the wind velocity and temperature
in an atmospheric boundary layer have been continuously controlled using a sodar, a temperature profile meter, and acoustic
anemometers or thermometers mounted on a 56-meter-high mast. The joint action of a near-ground acoustic waveguide, the impedance
of the underlying surface, and a vertical layered structure of the boundary atmospheric layer on a signal shape far from the
acoustic source are studied. 相似文献
8.
Two new types of mechanism for the generation of tidal residual flow are revealed with the use of a hydraulic model experiment. A remarkable anticlockwise tidal residual circulation is formed in a model bay due to the presence of a tidal current, the Coriolis force and a horizontal boundary. A similar circulation is also formed due to the presence of a bottom slope, a horizontal boundary and a tidal current which flows normal to the inclination of the bottom slope. The residual circulation in the Sea of Iyo in the Seto Inland Sea is considered to be due to a combination of the effects of the Coriolis force, a bottom slope, a horizontal boundary and the tidal current. We classified some of the generation mechanisms of tidal residual flow which have been described to date into seven types on the basis of vorticity considerations. 相似文献
9.
S. V. Semkin V. P. Smagin V. N. Savchenko 《Izvestiya Atmospheric and Oceanic Physics》2008,44(2):255-259
The feasibility of generating additional acoustic harmonics in the geomagnetic field during the propagation of an acoustic wave in a conducting medium through a region with a variable electromagnetic field is considered. Two possible mechanisms of such generation are analyzed: a parametric mechanism and a mechanism associated with ponderomotive forces (dynamic). Expressions are derived for three acoustic harmonics generated by a magnetic dipole with a variable magnetic moment. 相似文献
10.
利用扫描电子显微镜对我国6种热带海参(蛇目白尼参、玉足海参、花刺参、梅花参、子安辐肛参和巨梅花参)背脊部骨片的组成和结构进行了观察。结果表明,蛇目白尼参骨片有3种类型的花纹样体和1种杆状体;玉足海参骨片有2种类型的桌形体和1种扣形体;花刺参骨片有2种类型的桌形体、1种C形体和1种花纹样体;梅花参骨片有4种类型的杆状体;子安辐肛参骨片有1种花纹样体;巨梅花参骨片有1种杆状体、1种拟桌形体和1种颗粒体。结果显示,与之前学者光镜下观察的结果存在差异,玉足海参桌形体底盘中央是单孔而非4孔;花刺参桌形体立柱之间没有横梁连接。并发现了新的骨片类型:蛇目白尼参Ⅲ型花纹样体和杆状体;玉足海参顶部周缘小孔桌形体;花刺参顶部5簇小齿桌形体;梅花参Ⅱ型、Ⅲ型、Ⅳ型杆状体。 相似文献
11.
V. P. Trubitsyn 《Izvestiya Atmospheric and Oceanic Physics》2012,48(7):673-682
Intraplate earthquakes are described by a model of a thrust fault in continuous or cracked media. Such a model can also be used to describe interplate earthquakes, in particular, strong earthquakes in subduction zones. However, new seismic, tectonic, and GPS data for this strong Japanese earthquake demand a more detailed model. One possible model can be a model of the elastic island plate coupled with a dipping oceanic plate with submarine mountings. These mountings, sitting on the dipping oceanic plate, hinder its motion due to coupling with asperities on the bottom of the island plate. When coupling ends, the bottom of the plate can be cut as if by a plough and an earthquake can take place. The decoupling of a mountain leads to a weaker interpolate earthquake, a forshock, and an aftershock. The main earthquake is a result of the effect of a basaltic plateau or a large mountain, which leads to the avalanching decoupling of all mountains on a large area of coupled plates. In the first approximation we can consider that, despite its deformation, an oceanic plate is constantly moving with a nearly constant velocity all times both during earthquakes and in between them. An island plate behaves similarly to an elastic plate, which permanently bends due to torque acting on its junction with a dipping oceanic plate. After the earthquake, the bending plate becomes straight. This leads to it thrusting on the oceanic plate with displacement toward the ocean, an uplift of its oceanic part, and the sinking of its island part by the following tsunami. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2001,24(4):229-235
A crustal upheaval in a coastal zone is studied by introducing a simplified theoretical model of an equivalent elastic plate on which oceanic water is acting as a static loading. With a solution for the plate, the author notes what is seen as a crustal upheaval under the loading of static oceanic water in a qualitative scope. The solution requires some assumed parameters for the plate and the loading. Some other conditions should be also given to realize a possible dynamical understanding of a sea level rise seen after global climatological warming and glacial melting. 相似文献
13.
Many conventional ship autopilots use proportional integral and derivative (PID) control algorithms to guide a ship on a fixed heading (course-keeping) or a new heading (course-changing). Such systems usually have a gyrocompass as a single sensory input. Modern sea going vessels have a range of navigation aids most of which may be interconnected to form integrated systems. It is possible to employ the navigational data to provide best estimates of state vectors (Kalman filter) and optimal guidance strategies. Such techniques require powerful computing facilities, particularly if the dynamic characteristics of the vessel are changing, as may be the case in a maneuvering situation or changes in forward speed. This paper investigates the possibility of training a neural network to behave in the same manner as an optimal ship guidance system, the objective being to provide a system that can adapt its parameters so that it provides optimal performance over a range of conditions, without incurring a large computational penalty. A series of simulation studies have been undertaken to compare the performance of a trained neural network with that of the original optimal guidance system over a range of forward speeds. It is demonstrated that a single network has comparable performance to a set of optimal guidance control laws, each computed for different forward speeds 相似文献
14.
K. A. Gorshkov I. A. Soustova D. A. Sergeev 《Izvestiya Atmospheric and Oceanic Physics》2007,43(6):785-793
On the basis of the perturbation theory developed previously by the authors for localized hydrodynamic vortices, the influence of a specified jet flow and of the structure of individual vortices on the stability of the Karman street is investigated. It is shown that, for a street of vortices with a power law of decrease in the azimuthal velocity, the jet flow suppresses instability only with respect to perturbations with wavelengths from a certain range determined by the parameters of the flow. At the same time, for streets formed from vortices with a Gaussian profile of the azimuthal velocity, even in the absence of a specified flow, there is a certain region of the street’s parameters in which the street is stable against perturbations of all scales. Thus, for the purposes of modeling quasi-two-dimensional flows in a stratified fluid by a sequence of localized vortices, which is discussed in this study, vortices with a Gaussian profile of the azimuthal velocity turn out to be preferable. The results of this study are consistent with numerous experiments on the structure of a quasi-two-dimensional wake behind a body in a stratified fluid at large Reynolds and Froude numbers. 相似文献
15.
16.
We propose a coherent regression model building framework to construct fish-based indices. More specifically, we concentrate on the selection of an optimal set of metrics which remains a difficult problem. The paper departs from the observation that an index of biotic integrity (IBI) is analogous to a diagnostic model in medicine assessing the health condition of a patient from a series of biomarkers. In the same vein, an IBI is a diagnostic model predicting the ecosystem condition of a site from a set of (scored) metrics. Metrics are community attributes sensitive to anthropogenic pressure and their scores express the “distance to target” to a reference condition. In a medical context, Receiver Operating Characteristic (ROC) curves are commonly used to assess the diagnostic accuracy of laboratory tests. An ROC curve plots the sensitivity of a test (Se; the capacity to detect a disease or degradation) as a function of its false positive fraction (FPF) which is the complement of the specificity (Sp = 1 - FPF; the capacity to recognise a healthy person or a reference condition). The ROC curve represents the strength of the index to discriminate between degraded and reference sites. Higher curves correspond to stronger tests as then a higher sensitivity can be combined with a lower false positive fraction. Hence, it is intuitively clear to use summary statistics of the ROC curve as criteria to optimise medical tests or biotic indices. In this paper, we illustrate the value of this modelling framework with a case study in the Zeeschelde estuary in Belgium. In essence, a “traditional” IBI is an average of metrics scoring relevant properties of the ecosystem. We demonstrate this average score model (AVG) is a special member of the more flexible predictive logistic model (PLM) family. The selection of a set of metrics becomes equivalent to variable selection in statistical model building. We apply model building techniques as best subsets regression to facilitate the search for an optimal suite of metrics from a candidate set and use cross-validation to avoid overfitting. The results show that a few metrics suffice to discriminate between most-impacted and least-impacted sites. 相似文献
17.
Sato T. Suzuki Y. Kashiwagi H. Nanjo M. Kakui Y. 《Oceanic Engineering, IEEE Journal of》1978,3(1):1-4
A laser method for the remote detection of oil present as a pollutant in the sea water using Raman backscattering and backscattered fluorescence is discussed. The scattering spectra of oils obtained by using a laser Raman spectrometer that employs a CW Ar laser are described. The backscattering spectra of oils obtained by a laser radar technique in the laboratory and the field are also described. Furthermore, theoretical performance of a laser radar with a CW laser or a pulsed laser for the detection of Raman backscattering of kerosene is discussed. 相似文献
18.
地层完整性是指剖面上所有沉积物代表的总时间与地层剖面代表的总时间之比，由于地层剖面中或多或少地发育有沉积间断，因此地层剖面的完整性是一个大于０小于１的小数。如何准确地测定地层剖面的完整性是目前仍未能解决的地质学难题，近十余年来，国外有许多研究得潜心于这一领域的研究，从不同的角度提出了各自的测定方法，这些方法包括．长期／短期沉积速率比值法，剖面厚度／全球同期平均沉积厚度比值法，潜穴化石定性估测法以及 相似文献
19.
乌鳢和白乌鳢的比较研究 总被引：2，自引：0，他引：2
根据前人的工作,乌鳢分为三个亚种,乌鳢指名亚种Ophicephalus argus argusCantor黑龙江乌鳢O.a.warpachowskii Berg和白乌鳢O.a.kimurai(Shih)本文重点对乌鳢指名亚种和白乌鳢进比较。从形态特征、乳酸脱氢酶和酯酶同工酶表型及染色体组型上,没有发现明显差异(体色除外),并且两者分布区重叠。据此,作者认为,白乌鳢不能被划为一个亚种,而只能认为是普通乌鳢(指名亚种)的变异个体。文章还对亚种划分的标准问题,进行了讨论。 相似文献
20.
S. V. Shagalov V. P. Reutov G. V. Rybushkina 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):95-108
The generation of narrow-band Rossby wave packets and the modulated vortex chains induced by them in a weakly-dissipative
zonal flow on the beta-plane with a velocity profile in the form of a shear layer is studied. The analysis is performed within
the framework of the asymptotic approach based on the distinguishing a thin critical layer inside of which the vortex chains
are formed. The evolution equations, describing the simultaneous development of a wave packet envelope and vorticity perturbations
in a nonlinear critical layer, are derived for a weakly supercritical flow. A transition to the complex dynamics of a wave
packet (low-mode turbulence) is studied within the framework of a numerical solution of the derived equations and its mechanism
is revealed. The onset of chaotic advection and anomalous diffusion of passive scalar in the critical layer is considered,
and the exponent of the diffusion law is calculated. 相似文献