On the limiting parameters of artificial cavitation

Artificial cavitation, or ventilation, is produced by releasing gas into the liquid flow. One of the objectives of creating this multiphase flow is to reduce frictional and sometimes wave resistance of a marine vehicle completely or partially immersed in the water. Flows around surface ships moving along the water–air boundary are considered in this paper. It is favorable to achieve a negative cavitation number in the developed cavitating flow under the vessel’s bottom in order to generate additional lift. Cavities, formed in the flow, have limiting parameters that are affected by propulsion and lift-enhancing devices. Methods for calculating these influences and the results of a parametric study are reported.     

舰船灭火系统现状与发展

论述了舰船灭火系统的现状与发展，重点进行了卤代烷灭火系统的替代可行性分析。     

A fuzzy set theory approach to flagging out: towards a new Chinese shipping policy

The paper seeks to model the benefits and costs involved in the decision to flag out, and to provide arguments for alternative policies, aiming to counteract this age-long phenomenon. Based on the analysis of the evolution of worldwide and Chinese flagging out, the emphasis in the paper is on the comprehensive effect assessment of flagging out and the required adjustment of Chinese shipping policy. To identify the determinants of such an adjustment, the paper introduces fuzzy set theory and related models, aimed to assess the economic effects of flagging out through the use of context-dependent economic and societal indicators (factors). The degree to which such indicators contribute to the choice of flag decision is assessed through a questionnaire survey. In parallel, and in the context of the determinant analysis of fuzzy models, the paper probes into the ‘policy competition’ and ‘government intervention’ policies to counteract flagging out. In the same context, a comparative analysis of shipping policies between China and traditional maritime countries is undertaken, in order to assess the current ‘openness’ of the Chinese shipping policy and explore possible policy alternatives. The paper concludes that the preferred policy alternative for China would be the establishment of second international ship register.     

高校应如何在社区开展海洋环境教育

文章通过分析当前海洋环境教育的现状,提出高校在社区开展的海洋环境教育中应包括海洋权益教育、资源、海洋自然灾害教育、海洋有毒生物教育以及可持续发展教育等内容。在实施的同时,要注重运用求真务实的科学态度,采取各种社区海洋环境教育形式,通过在社区墙报栏开展公民的海洋环境教育、举办海洋知识讲座、海洋生物标本展览以及利用寒暑假举办社区的中小学生夏令营等形式来开展海洋环境教育,营造浓厚的海洋环境教育氛围,并在此基础上积极利用媒体的作用,介绍和宣传社区海洋环境教育活动等建议,以达到进一步完善社区环境教育,寻求把海洋环境教育融入当前的社区环境教育中的途径,达到普及海洋环境知识和增强人们海洋意识的效果。     

Wave characteristics and extreme parameters in the Bohai Sea

This paper is aimed at the whole Bohai Sea,as the complement and improvement of wave characteristics and extreme parameters.Wave fields were simulated in the Bohai Sea by using wave model SWAN from 1985 to 2004.The input data based on the hindcast of high-resolution wind fields from RAMS and water level fields from POM,which have been tested and verified well.Comparisons of significant wave heights between simulation and station observations show a good agreement in general.By statistical analysis,the wave characteristics such as significant wave heights, dominant wave directions and their seasonal variations are discussed.In addition,main wave extreme parameters and directional extreme values particularly for 100-year return period are investigated.     

Climatic parameters of wind-field variability in the Black Sea region: Numerical reanalysis of regional atmospheric circulation

A reanalysis of atmospheric circulation in the Black Sea region is performed with a high spatial resolution of 25 × 25 km for the period from 1958 to 2001. Climatic wind speed fields are estimated, as are their spatial structure and seasonal variability. Mesoscale regions of cyclonic and anticyclonic speed vorticity, which are connected with edge effects and orography, are distinguished. To single out the monsoon mechanism in the annual votricity cycle, numerical experiments on the sensitivity that the regional atmospheric circulation has to the sea-surface temperature perturbations have been carried out. Large-scale regional peculiarities of the surface wind field are considered for different seasons. The vorticity of the surface wind speed and strength is assessed. Large annual average values of the vorticity are obtained which are comparable with the range of seasonal variability; they evidence the defining role that wind plays in the generation and seasonal variability, as well as the average cyclonic water circulation in the Black Sea.     

瓯江口外潮汐通道区滩槽冲淤演变分析及其调整机制的探讨

基于瓯江口外潮汐通道区的历史水深地形资料,利用地理信息系统技术,建立不同年份的数字高程模型(DEM),利用DEM进行数字化冲淤定量计算,分析特征地貌冲淤演变过程,并结合水文泥沙条件,对其演变和调整机制进行了初步探讨。结果表明:(1)1933—2005年的72 a间,瓯江口外潮汐通道区底床总体表现为微量冲刷,平均冲刷厚度为27 cm,冲刷速率为0.375 cm/a。(2)特征地貌单元经历了较大幅度的冲淤演变和形态调整,深槽处于较稳定的冲刷拓展过程;温州浅滩持续淤积,近年来人类活动的影响加快其淤积;中沙浅滩和重山沙嘴受冲刷移动最终合二为一。(3)在自然的潮流动力作用下,浅滩与深槽之间进行泥沙交换运移,是研究区滩槽冲淤演变的主要调整机制。     

间隔取液法延长化学镀镍液寿命的研究

研究了通过间隔取液法延长化学镀镍液使用寿命的技术,通过孔隙率试验测定镀层耐孔蚀性能。结果表明,间隔取液法可以有效地延长镀液的使用寿命,镀液中有害离子Na ,SO42-,HPO3-的临界浓度分别为1.99,0.626和0.486mol/L。当取液量>11%时,镀液中的有害离子均不超过其临界浓度,镀液可以循环使用。     

Using the ensemble Kalman filter to estimate multiplicative model parameters

This paper proposes a simple approach to estimating multiplicative model parameters using the ensemble square root filter. The basic idea, following previous studies, is to augment the state vector by the model parameters. While some success with this approach has been reported if the model parameters enter as additive terms in the tendency equations, this approach is problematic if the model parameters are multiplied by the state variables. The reason for this difficulty is that multiplicative parameters change the dynamical properties of the model, and in particular can cause the model to become dynamically unstable. This paper shows that model instability can be avoided if the usual persistence model for parameter update is replaced by a temporally smoothed version of the update model. In addition, the augmentation approach can be interpreted as two simultaneously decoupled ensemble Kalman filters for the model state and the parameter state, respectively. Implementation of the parameter estimation does not require changing the data assimilation algorithm—it just has to be supplemented by a parameter estimation step that is similar to the state estimation step. Covariance localization is found to be necessary not only for the model state, but also for augmented model parameters, if they are spatially dependent. The new formulation is illustrated with the Lorenz-96 model and shown to be capable of estimating additive and multiplicative model parameters, as well as the state, under relatively challenging conditions (e.g. using 20 observations to estimate 120 unknown variables).     

从海岸地貌学看河海划界的可操作性

根据河海划界的可操作性的要求,探讨了海岸地貌学指标在河口区划分中的作用,并通过对河口区与河流、海洋之间的动态联系的阐述,提出河口区管理方式的建议.河口是海岸带陆海相互作用的典型环境,具有物理、化学、地质、生物和环境等多种复杂动力学过程,每一个河口都是高度个性化的.在为数不多的体现河口共性的参数中,海岸地貌学指标可用来确定河口区的内、外边界.根据河流水力学特征和河口过程的可容空间范围特征,河口-河流的分界点可用B-L曲线(B为河岸宽度,L为距离原点沿河流轴线的累积长度)上的拐点位置来表示.而按照河口为"半封闭水域"的定义,河口-海洋分界线可采用围封河口水域的海岸线的包络线.河口水域受到河流和海洋的双重影响,且河口区的自然演化和人类开发活动也会影响河流和海洋.因此,在我国河口区管理上应建立海洋和其他管理部门之间的协调机制.     

Coupling parameters of the MIT OBS at two nearshore sites

A model representing the coupling of an ocean-bottom seismometer (OBS) to the seafloor as a mass-spring-dashpot system satisfactorily explains the results of transient tests performed on different instruments during the Lopez Island intercomparison test. In this paper, we compare the results obtained for the MIT OBS at Lopez Island to results from similar tests at a dockside site at Woods Hole, Massachusetts. The vertical instrument response at the Lopez Island site shows a highly damped resonance at a frequency of 22 Hz, whereas the response at the Woods Hole site shows a marked resonance at 13 Hz. The difference between the responses at the two sites can be qualitatively attributed to the difference between the surficial sediments.     

On the ability to estimate narrow-band signal parameters usingtowed arrays

Using the Cramer-Rao lower bound (CRLB) as an indicator of potential performance, the limits on the estimation and resolution capabilities of a towed line array of uniformly spaced hydrophones to provide frequency and bearing information about narrowband signals are examined. It is assumed that a monochromatic plane wave arrives at the array for each source. Several versions of the bounds are computed using different assumptions about which parameters have known values and about the way in which the samples are taken in space and in time. It is shown that the CRLB values for different situations can be compared to provide information about the effective use of a moving aperture for estimation of the parameters of narrowband signals arriving at the array. It is also shown that adding at least one hydrophone occupying a fixed position in space can improve the bearing estimates of a towed array by supplying additional frequency information if both the bearings and frequencies of the sources are unknown     

Average grain-size parameters of unlithified sediments in the World Ocean

The high diversity of grain-size parameters of marine and oceanic sediments is determined by hydrodynamical and gravitational processes. Grain-size spectra of the sediments in the World Ocean are represented by two main types. Filtering organisms that passively inherit the proportions of clayey fractions in suspended matter only accelerate the deposition of fine particles, not influencing their distribution at the bottom.     

Interhemispheric distinctions in wind-regime parameters in the polar mesosphere-lower thermosphere

The wind circulations in the mesosphere-lower thermosphere at polar latitudes of the Northern and Southern hemispheres are compared on the basis of long-term monthly-mean data on the prevailing zonal and meridional winds and on the parameters of diurnal and semidiurnal migrating tides obtained from the international network of radar stations. Comparison of the seasonal cycles and vertical profiles of the prevailing winds and tide parameters points to the existence of significant distinctions between the hemispheres. These distinctions are most clearly pronounced, first, in the prevailing meridional winds (for example, the annual mean winds in the polar regions have opposite directions in different hemispheres) and, second, the annual cycles of semidiurnal-tide amplitudes, as well as the character of changes in the tide phase with height, are fundamentally different for the Northern and Southern hemispheres. Along with these, significant distinctions are revealed in the prevailing zonal winds and in the diurnal-tide parameters.     

Grain-size parameters of marine sediments

In their average grain-size parameters (K _d , K _dl), recent sediments of the northern Caspian Sea and the Barents Sea shelf are similar, while the sediments of the Norwegian Sea are closer to their counterparts of the World Ocean. Seaward, the content of the subcolloidal fraction increases against the background of the decreasing proportions of coarse-and medium-grained pelite matter.     

简便的水文频率计算方法

在概率分布线型确定下,水文频率计算就是根据样本资料估算其中包含的参数。计算P-Ⅲ型分布参数的方法很多,目前常采用的最简单的方法是三点法,用图解适线求参数。本文中笔者建议用二点法直接利用K值表求参数。该方法简便,且不易出错。同时又能保证适线法的精度要求。     

Remote sensing studies in the Haikou Bay Calculation of the deposition parameters

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