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1.
The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.  相似文献   

2.
A method to predict typhoon waves   总被引：2，自引：0，他引：2  
Ａｍｅｔｈｏｄｔｏｐｒｅｄｉｃｔｔｙｐｈｏｏｎｗａｖｅｓ￥ＹａｎｇＣｈｕｎｃｈｅｎｇ；ＤａｉＭｉｎｇｒｕｉ；ＧａｏＺｈｉｈｕａ；ＣｈｅｎｇＺｈａｎ；ＸｕＦｕｘｉａｎｇ；ＬｉｕＹｕ；ＬｉＦｅｎｇｊｉｎ；ＬｉＪｉｅ；ＳｕＤｏｎｇｆｕ；ＺｈａｎｇＤａｃｕｏ...  相似文献   

3.
Coastal flood risk is defined as a product of probability of event and its effect, measured in terms of damage. The paper is focused on coastal management strategies aimed to decrease risk by decreasing potential damage. We review socio-economic literature to show that total flood damage depends on individual location choices in the housing market and on individual flood risk awareness. Low flood risk awareness leads to inefficient spatial developments and increased flood risk. We show that personal experience, risk communication, financial instruments like insurance from flooding and technical instruments like building on high elevations, are factors that increase individual risk awareness. Evidence that these factors indeed affect housing prices and land use patterns is provided. We discuss proactive instruments that can be used in coastal zone management in the Netherlands to increase individual risk awareness. We argue that policy-makers may create incentives giving individuals a possibility to make location choices that lead to less total flood risk in the coastal zone area.  相似文献   

4.
A microcosm experiment was used to compare the influence of diesel contamination on two benthic salt-marsh communities, one chronically exposed to petroleum hydrocarbons for decades (Louisiana [LA]) and the other relatively uncontaminated (Mississippi [MS]). Initial meiofaunal community composition of the two sites was similar. Higher organic content of MS sediments should have reduced bioavailability, and thus the toxicity of hydrocarbons relative to the LA site. Nevertheless, although responses to diesel contamination at the two sites were generally qualitatively similar, a species-specific and several community-response variables were influenced to a much greater degree in the MS community. In particular, the abundance of total nauplii, ostracods, and copepods were negatively impacted to a greater extent in MS than in LA, as was grazing by ostracods on benthic microalgae. Nematode:copepod ratios in contaminated sediments were much higher in MS than in LA sediments. Pseudostenhelia wellsi (a benthic copepod) nauplii suffered greater adverse effects of diesel in MS than in LA. We conclude that the MS community was more sensitive to diesel contamination than was the LA community. The differential sensitivity is presumably a manifestation of different tolerances to hydrocarbon contaminants, mediated by a higher proportion of more tolerant species and/or increased tolerance among individual species in LA. Although the MS site was more sensitive to diesel contamination, qualitative response of the LA and MS communities were similar, and comparable to previous studies of diesel contamination. The spatial and temporal consistency of diesel impacts on salt-marsh communities suggests that hydrocarbon contamination results in predictable community responses. Specifically, crustacean (e.g. copepods, ostracods, and nauplii) benthos are most sensitive to hydrocarbons. Reductions in abundance and grazing activity of crustaceans leads to enhanced algal biomass, reduced copepod diversity, and alters competitive interactions among meiofauna.  相似文献   

5.
China Marine Surveillance Force was equipped with modern aerial equipments for marine lawexecute with the advantage of functioning agilely at a large scale of surveillance coverage, providing powerful all-round safeguard, which is of benefit to the harmonious and sustainable development of coastal economy. Onboard the planes, three kinds of remote sensing sensors have been installed, including a marine airborne multi-spectrum scanner (MAMS), an optical-electronic platform, and an airborne hyper-spectral system AISA+. The specifications of remote sensing platforms were introduced briefly first, then examples of water quality monitoring by airborne remote sensing were presented, including the monitoring in coastal suspended material, oil-spill and abnormal warm water, etc.  相似文献   

6.
ＰａｔｈｏｇｅｎｓａｎｄｐａｔｈｏｇｅｎｉｃｉｔｙｔｏＰｅｎａｅｕｓｏｒｉｅｎｔａｌｉｓＫｉｓｈｉｎｏｕｙｅＩＮＴＲＯＤＵＣＴＩＯＮＢａｃｔｅｒｉａ，ｅｓｐｅｃｉａｌｌｙｖｉｂｒｉｏｓａｒｅｏｎｅｏｆｔｈｅｍａｊｏｒｐａｔｈｏｇｅｎｓｔｏｃｕｌｔｕｒ...  相似文献   

7.
The analytical method (AM) for separation of composite waves is presented based on the Hilbert transform. It is ap-plicable to both regular and irregular trains of waves. The wave data series measured with two wave gauges in the experi-ments are separated into two series of incident and reflected waves. Then, the reflection coefficient can be easily ob-tained. The arrival of reflected waves can also be detected for improveraent of the accuracy of the reflection coefficient. The reflection performance of the physical model can be estimated exactly without calculation of wave height and phase difference. Numerical samples developed to test the method are proved to be accurate. Physical experiments are conduct-ed and compared with Goda s method and satisfactory results are obtained.  相似文献   

8.
A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domain second order theory of water waves. Liquid sloshing in a rectangular container subjected to a horizontal excitation is sim-ulated by the finite element method. Comparisons between the two theories are made based on their numerical results, It is found that good agreement is obtained for the case of small amplitude oscillation and obvious differences occur for large amplitude excitation. Even though, the second order solution can still exhibit typical nonlinear features of nonlinear wave and can be used instead of the fully nonlinear theory.  相似文献   

9.
- Based on the theory of limit analysis, the Finite Difference Method (FDM) is established for evaluating the ultimate bearing capacity of subsoils to bear the unburied pipelines. The analytical results of bearing capacity of the ideal clay is given. The approach to bearing capacity evaluation of cohesionless subsoils without surcharge is suggested. The results from this method are consistent with those obtained from model tests.  相似文献   

10.
Response of Coastal Groundwater Table to Offshore Storms   总被引：1，自引：0，他引：1  
Large groundwater table fluctuations were observed in a coastal aquifer during an offshore storm. The storm induced significant changes of the mean shoreline elevation, characterized by a pulse-like oscillation. This pulse propagated in the aquifer, resulting in the water table fluctuations. A general analytical solution is derived to quantify this new mechanism of water table fluctuation. The solution is applied to field observations and is found to be able to predict reasonably well the observed storm-induced water table fluctuations. Based on the analytical solution, the damping characteristics and phase shift of the oscillation as it propagates inland are examined.  相似文献   

11.
Number1Page1 ………………………Observation of ocean current response to 1998 Hurricane Georges in the Gulf of MexicoZHENG Quanan, LAIRonald J, HUANG Norden E, PANJiayi, LIU WTimothy15 ………………………Second-order random interfacial wave solutions for tw  相似文献   

12.
The application of Hartley transform to ocean engineering   总被引：1，自引：0，他引：1  
The Hartley transform is a real integral transform based on harmonic functions and hassome characteristics similar to the Fourier transform. Most applications in ocean engineering requiring the Fourier transform can also be performed by the Hartley transform. The fast Hartley transform is twice faster and more convenient to handle than the corresponding fast Fourier transform, so it is a real valued alternative to the complex Fourier transform in many applications. The use of the Hartley transform in ocean engineering is presented in detail in this paper, including wave spectral analysis, separation of waves, cross-correlation in PIV technique and expression of equation in the Hartley domain. The examples in the paper show deeply the advantage and efficiency of the Hartley transform over the Fourier transform.  相似文献   

13.
A finite-difference approach is used to develop a time-dependent mild-slope equation incorporating the effects of bottom dissipation and nonlinearity.The Euler predictor-corrector method and the three-point finite-difference method with varying spatial steps are adopted to discretize the time derivatives and the two-dimensional horizontal ones,respectively,thus leading both the time and spatial derivatives to the second-order accuracy.The boundary conditions for the present model are treated on the basis of the general conditions for open and fixed boundaries with an arbitrary reflection coefficient and phase shift.Both the linear and nonlinear versions of the numerical model are applied to the wave propagation and transformation over an elliptic shoal on a sloping beach,respectively,and the linear version is applied to the simulation of wave propagation in a fully open rectangular harbor.From comparison of numerical results with theoretical or experimental ones,it is found that they are in reasonable agreement.  相似文献   

14.
Marine HydrologyN.-p1-1 …………………………Numerical study on residual current and its impact on mass transport in the Hangzhou Bayand the Changjiang Estuary-I. A3-D joint model of the Hangzhou Bay and theChangjiang EstuaryZhu Shouxian (?ìê×?í), Shi Fengyan (ê**??ò), Zhu Jianrong (?ì1/2ㄈ? and DingPingxing (???1/2兴)1-15……………………………………Three dimensional diagnosic, semidiagnostic and prognostic calculations of current in theEast China Sea in April of 1994Wang Huiqu…  相似文献   

15.
This paper investigates the characteristics of reduction of the lateral vibration by use of a Tuned Mass Damper (TMD) for offshore jacket platforms under impact loading. Unlike traditional analysis, the present analysis focuses on the energy concept of TMD/structure systems. In this study, a time domain is taken. The platform is modeled as a simplified single-degree-of-freedom (SDOF) system by extraction of the first vibration mode of the structure and the excited force is assumed to be impact loading. The energy dissipation and energy transmission of the structure-TMD system are studied. Finally, an optimized TMD design for the modeled platform is demonstrated based on a new type of cost function - maxi-mum dissipated energy by TMD. Results indicate that TMD control is effective in reducing the Standard deviation of the deck motion but less effective in reducing the maximum response under impact loading.  相似文献   

16.
ＭａｒｉｎｅＨｙｄｒｏｌｏｇｙＮ .- ｐ1- 1………………………………ＣｉｒｃｕｌａｔｉｏｎａｎｄｉｔｓｓｅａｓｏｎａｌｖａｒｉａｂｉｌｉｔｙｉｎｒｅｇｉｏｎａｒｏｕｎｄｔｈｅＫｅｒｇｕｅｌｅｎＰｌａｔｅａｕＳｈｉＪｉｕｘｉｎ(史久新 ) ,ＬｅＫｅｎｔａｎｇ(乐肯堂 )ａｎｄＢｙｕｎｇＨｏＣｈｏｉ1- 19………………………………ＩｍｐｌｅｍｅｎｔａｔｉｏｎａｎｄａｐｐｌｉｃａｔｉｏｎｏｆａｎｅｓｔｅｄｎｕｍｅｒｉｃａｌｓｔｏｒｍｓｕｒｇｅｆｏｒｅｃａｓｔｍｏｄｅｌｉｎｔｈｅＥａｓｔＣｈｉｎａＳｅａＹｕＦｕｊ…  相似文献   

17.
The existing methods of downward continuation of potential field cannot be used to continue the aeromagnetic data to the marine surface because of the limited continuation distance. An iteration method for the downward continuation of potential field with a much larger continuation distance has been developed, which can continue the aeromagnetic data to the marine surface and get the marine - magnetic chart with the same scale as the aeromagnetic data. This downward continuation method will greatly raise the ef- ficiency of marine - magnetic investigation. The principle of the iteration method is presented. The method is demonstrated on synthetic models and real aeromagnetic data. Also, the error brought by continuation is discussed. The efficiency of the iteration method for the downward continuation of potential field is compared with the fast fourier transform （FFT） method, the former is much better than the latter.  相似文献   

18.
In Norway there is a long tradition of allocating fish resources among the fishers. In modern times this has been done through specific allocation keys. This article describes the development of the allocation system for the offshore (trawler) and coastal fleets. The allocation system is closely related to stock assessment and the fixing of global quotas (TACs) as well as structural policies to prevent “capacity creep”. All three systems can be seen as institutions, where the TAC-machine is firmly established while the two others are under pressure, largely due to competition on the global fish market. The established goal of maintaining a diversified fishing fleet is now gradually being dismantled, with repercussions for coastal employment and settlement patterns. The coastal fleet is per 2013 something entirely different from the situation in 1990, when the coastal fisheries were effectively closed. Sooner or later this development is bound to change also the management institutions, and in particular the allocation system and the closely related structural policies.  相似文献   

19.
Fishery managers are faced with the challenge of maintaining sustainable fisheries at the lowest possible cost while conforming to international and national obligations. Given that fisheries range from low to high value, there is a real need to understand how to trade ecological and economic risks, and the various costs associated with their management, against the benefits from catch. Key to this is an understanding of (a) the costs corresponding to a given level of acceptable risk, or conversely, (b) the change in risk given a change in cost investment. This paper first defines biological, economic and ecosystem risk at a whole-of-fishery level, and then develops a simple model to quantify the trade-offs between risk, cost and catch. Using as case studies Australia's federally managed fisheries that range from data-rich to data-poor, risk was quantified for target species in terms of both their limit and target reference points (defined as “biological risk” and “economic risk”, respectively), and for ecosystems in terms of overall ecological impact (defined as “ecosystem risk”). A statistical linear model was used to quantify the risk–cost–catch frontier for each of the three forms of risk. The most parsimonious models were statistically significant for each. However, the management and research costs were mostly positively correlated with risk, indicating that these tended to be reactive to risk, as opposed to risk decreasing in response to increased costs. The only model where this was not the case was for the ecosystem risk, which is probably because these risks have only recently been assessed and the management response to these risks across all the fisheries has so far been limited. For target species risks, it was not possible to develop a model for proactive use. However, the method itself has merit and, if the costs were defined to a greater level of resolution, and/or a time-dynamic modelling approach considered, these issues could potentially be addressed.  相似文献   

20.
Marine Hydrologyl·····,·····,·····,·········……The equilibrium range of wind wave frequency spectrum wi砚5‘,绍‘扒夕(5.‘.”h沙)(文圣常),z加爪夕建灿。妇(张大错),〔〕饭,及汤面(陈波海)耐G翻尹如尹翻夕 (郭佩芳)13·,,···················,·····,·…伪mbined refraetion andd‘ffraetion models for sea wa低over comPlieated toPograPhy andw亘th eur- te月ts jn shallow water 玩及侧昭尹如(尹宝树)耐J如吩八”翻(蒋德才)25-···.--····-·····-·····…  相似文献   

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