共查询到20条相似文献，搜索用时 46 毫秒
1.
为对北极地区进行更深入和更细致的探索，助力我国参与北极事务和开发利用北极资源，越来越多的国内学者对北极问题展开研究。文章梳理国内北极问题研究的理论和方法，并分别从来源、应用和展望等方面对现有理论和方法进行分析和总结。研究结果表明:国内北极问题研究的理论主要包括渐进决策理论、地缘政治理论和地缘势理论、通权论和“通实力”理论、国际公共品理论和公共价值管理理论以及多层治理理论和协同治理理论，方法主要包括定性分析方法、定量分析方法、定性与定量相结合的分析方法以及多学科交融的新型方法；基于相关理论和方法尚缺乏纵向支撑、系统体系和量化分析的现状，未来北极问题研究的发展趋势为研究体系增强系统性、学科交融、研究理论富于实用性以及研究方法融入更多量化分析。 相似文献
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Comparison of Linear Level I Green-Naghdi Theory with Linear Wave Theory for Prediction of Hydroelastic Responses of VLFS 总被引：4，自引：0，他引：4
Very Large Floating Structures (VLFS) have drawn considerable attention recently due to their potential significance in the exploitation of ocean resources and in the utilization of ocean space. Efficient and accurate estimation of their hydroelastic responses to waves is very important for the design. Recently, an efficient numerical algorithm was developed by Ertekin and Kim (1999). However, in their analysis, the linear Level I Green-Naghdi (GN) theory is employed to describe fluid dynamics instead of the conventional linear wave (LW) theory of finite water depth. They claimed that this linear level I GN theory provided betler predictions of the hydroelastic responses of VLFS than the linear wave theory. In this paper, a detailed derivation is given in the conventional linear wave theory framework with the same quantity as used in the linear level I GN theory framework. This allows a critical comparison between the linear wave theory and the linear level I GN theory. it is found that the linear level 相似文献
3.
Approximate Stream Function wavemaker theory for highly non-linear waves in wave flumes 总被引：1，自引：0，他引：1
An approximate Stream Function wavemaker theory for highly non-linear regular waves in flumes is presented. This theory is based on an ad hoc unified wave-generation method that combines linear fully dispersive wavemaker theory and wave generation for non-linear shallow water waves. This is done by applying a dispersion correction to the paddle position obtained for non-linear long waves. The method is validated by a number of wave flume experiments while comparing with results of linear wavemaker theory, second-order wavemaker theory and Cnoidal wavemaker theory within its range of application. 相似文献
4.
D. L. Kriebel 《Ocean Engineering》1992,19(1)
Theoretical results for second-order wave run-up around a large diameter vertical circular cylinder are compared to results of 22 laboratory experiments conducted in regular nonlinear waves. In general, the second-order theory explains a significant portion of the nonlinear wave run-up distribution measured at all angles around the cylinder. At the front of the cylinder, for example, measured maximum run-up exceeds linear theory by 44% on average but exceeds the nonlinear theory by only 11% on average. In some cases, both measured run-up and the second-order theory exceed the linear prediction by more than 50%. Similar results are found at the rear of the cylinder where the second-order theory predicts a large increase in wave amplitude for cases where the linear diffraction theory predicts little or no increase. Overall, the nonlinear diffraction theory is found to be valid for the same relative depth and wave steepness conditions applicable to Stokes second-order plane-wave theory. In the last section of the paper, design curves are presented for estimating the maximum second-order wave run-up for a wide range of conditions in terms of the relative depth, relative cylinder size, and wave steepness. 相似文献
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用 Monte Carlo方法数值模拟海浪 ,研究其波包曲线跨某参考水平的波包中空波包所占的平均比例 ,并与 Ditlevsen和 L indgren关于空波包的理论相比较。结果表明 ,在二阶近似下该理论近似适用于海浪。在此基础上对 Longuet- Higgins的群性波包理论进行修正。修正后的理论与数值结果的比较表明本文所做的修正是十分有效的。修正后的群性波包理论克服了原理论的某些固有缺陷 相似文献
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Existing hydroelastic theories are reviewed. The theories are classified into different types: two-dimensional linear theory, two-dimensional nonlinear theory, three-dimensional linear theory and three-dimensional nonlinear theory. Applications to analysis of very large floating structures (VLFS) are reviewed and discussed in details. Special emphasis is placed on papers from China and Japan (in native languages) as these papers are not generally publicly known in the rest of the world. 相似文献
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In this paper, by non-dimensional analysis, it is found that finite-depth theory is more appropriate to the study of internal solitary waves (ISWs) in the South China Sea (SCS) than shallow-water theory. The 1-degree grid data of monthly mean temperature and salinity data at standard levels in the SCS are used to solve the linearized vertical eigenvalue problem. The nonlinear parameter and the wave phase speed are computed, then the nonlinear phase speed and the characteristic half-width of ISWs are calculated respectively by two different theories to investigate the difference between these two parameters in the SCS. The nonlinearity is the strongest near the continental slope of the SCS or islands where the bottom topography changes sharply, it is stronger in summer than that in winter; it increases (decreases) as pycnocline depth deepens (shallows), stratification strengthens (weakens) and pycnocline thickness thins (thickens). The nonlinear wave phase speed and the characteristic half-width are the largest in deep sea area, they then reduce peripherally in shallower water. The nonlinear wave phase speed in the SCS changes slightly with time, but the characteristic half-width changes somewhat larger with time. In most of the SCS basin, the nonlinear wave phase speed derived from shallow-water theory is very close to that derived from finite-depth theory, but the characteristic half-width derived from shallow-water theory is about 0.2–0.6 times larger than that derived from finite-depth theory. The ISW induced horizontal current velocity derived from shallow-water theory is larger than that derived from finite-depth theory. Some observed and numerical modeled ISW characteristic half-widths are compared with those derived from shallow-water and finite-depth theories, respectively. It is shown that, the characteristic half-widths derived from finite-depth theory agree better with observational and numerical modeled results than those derived from shallow-water theory in most cases, finite-depth theory is more applicable to the estimation of ISW characteristic half-widths in the northern SCS. It is also suggested that, to derive the precise ISW parameters in further study, the physical non-dimensional ratios which are related with ISW characteristic half-width, amplitude, thermocline and water depths should be calculated, so that an appropriate theory can be chosen for estimation. 相似文献
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本文概述了近２００年来大地构造理论建立与发展历史。当今大地构造理论研究的现状,各种学派的理论观点,特别是板块构造理论在地学革命中对大地构造理论发展的影响,随之产生的地体构造和新的全球构造观。尽管板块构造理论曾一度占据主导地位,但有关大陆构造、全球构造、造山作用和运动机制等一些基本问题尚未得到完满的解决。７０年代以来,国际上开展一系列重大调查研究计划,使地球科学朝着“广、精、深”方向发展,这将有力地 相似文献
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A theoretical expression of the wave power striking a rectilinear array of wave energy convertion devices in a random sea is derived. The theory is then applied to a linear array which is 1 km in length. For purposes of illustration, the Pierson-Neumann-James directional spectrum is used to represent the random sea. Comparison of the results obtained by using the present theory with those obtained from the previously accepted theory shows significant differences. First, the maximum available power predicted by the present theory is 75% of that predicted by the former theory. Secondly, power transmission is predicted when the wind direction and the array axis are parallel, whereas no power transmission was formerly predicted for this condition. 相似文献
10.
《Ocean Engineering》2007,34(3-4):362-370
The conceptual design of a very large floating structure (VLFS) requires a convenient computer code for predicting hydroelastic behavior of it. The code should not be time consuming, but it should be flexible for all environmental conditions. In order to meet the needs, we apply the ray theory for predicting hydroelastic behavior of a mat-like VLFS. The hydroelastic behavior of the VLFS is treated as wave propagation in the platform. The theory itself is based on the classical ray theory, which yields a quick computational scheme. The parabolic approximation is applied to smoothing the discontinuous deformation obtained by the classical ray theory. An experimental technique in a small wave tank with a mini scale model has been developed. Through comparisons with the mini scale experiment and other data found in literatures, it is confirmed that the ray theory has enough accuracy for the conceptual design, unless the assumptions of the ray theory are completely violated. 相似文献
11.
With growing computational power, the first-order wave-maker theory has become well established and is widely used for numerical wave flumes. However, existing numerical models based on the first-order wave-maker theory lose accuracy as nonlinear effects become prominent. Because spurious harmonic waves and primary waves have different propagation velocities, waves simulated by using the first-order wave-maker theory have an unstable wave profile. In this paper, a numerical wave flume with a piston-type wave-maker based on the second-order wave-maker theory has been established. Dynamic mesh technique was developed. The boundary treatment for irregular wave simulation was specially dealt with. Comparisons of the free-surface elevations using the first-order and second-order wave-maker theory prove that second-order wave-maker theory can generate stable wave profiles in both the spatial and time domains. Harmonic analysis and spectral analysis were used to prove the superiority of the second-order wave-maker theory from other two aspects. To simulate irregular waves, the numerical flume was improved to solve the problem of the water depth variation due to low-frequency motion of the wave board. In summary, the new numerical flume using the second-order wave-maker theory can guarantee the accuracy of waves by adding an extra motion of the wave board. The boundary treatment method can provide a reference for the improvement of nonlinear numerical flume. 相似文献
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基于二阶斯托克斯波理论推导了辐射应力的垂向分布表达式,通过算例讨论了辐射应力在深水和有限水深条件下的垂向分布规律,并与基于微幅波理论的辐射应力进行了比较.结果表明,在波浪非线性不强时,基于二阶斯托克斯波理论的辐射应力与基于微幅波理论的辐射应力表达式计算结果接近;而当水深较浅波浪非线性较强时,基于二阶斯托克斯波理论的辐射应力在近表面处明显大于基于微幅波理论的辐射应力.采用二阶斯托克斯波理论推导的波浪辐射应力更为合理地反映了波浪非线性效应. 相似文献
13.
Results of an experimental study of the effect of surface proximity on hydrofoil lift are presented. The biplane image theory, a horseshoe vortex model and momentum theory are described in relation to the effect of surface proximity on hydrofoil lift and drag. The biplane image theory and the horseshoe vortex model are shown to predict the same effect on lift, and are seen to be in good agreement with the experimental data. The Payne momentum theory is seen to differ significantly from the measured results. The data indicate a significant reduction in lift at depths less than two chords with very little effect at greater depth. 相似文献
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辽宁海洋生态补偿研究文献甚少,直面主要课题是机制创新。文章基于公共物品理论、外部性理论、生态价值理论、环境正义理论和可持续发展理论,遵循行为明确性原则、科学性原则、协商性原则、可操作性原则和动态性原则,依照海洋生态系统服务功能、海洋资源资产服务功能、海洋生态系统损害评估、海洋生态系统损失评估报告、海洋生态系统补偿与受偿主体确定、海洋生态系统补偿金额确定、海洋生态系统补偿执行、海洋生态系统补偿监控、海洋生态系统补偿评估与终结等运作程序创建了海洋生态补偿机制。进而,从提升社会公众认知、明确生态补偿制度、完善生态补偿机制、选定价值评估方法和评估生态补偿效益维度,探讨了海洋生态补偿实践路径。 相似文献
15.
In this paper the variations of radiation stress and mean water level are studied for the two-dimensional shoaling and breaking of progressive, periodic waves on a plane, gently sloping laboratory beach. Observations of radiation stress and mean water level were made for two initial conditions. The observed variations are compared to the variations as calculated by a linear theory, James' nonlinear theory, and a new nonlinear theory based on Cokelet's work. It is shown that the nonlinear theories are qualitatively and quantitatively superior to the linear theory, thus indicating that the effects of finite amplitude are important for the present case. 相似文献
16.
吕宋海峡深层水体体积输运的诊断分析 总被引：1，自引：0，他引：1
使用WOD09, WOA05, WOA01和SODA四种水文数据,利用水力学理论对吕宋海峡的深层水体体积输运进行了估计。结果表明：由于忽略了摩擦和地形等因素的影响,水力学理论得到的输运结果是深层体积输运的上限。不同数据以及吕宋海峡东西两侧选取的不同区域,都对水力学理论的体积输运估计存在显著影响。SODA数据在吕宋海峡附近的深层海区存在偏差,得到体积输运估计明显偏大,因而不适用于水力学理论进行吕宋海峡深层水体体积输运的估计。为对于南海的环流、混合及生态环境存在重要影响的吕宋海峡深层水体体积输运进行合理估计,对利用水力学理论估计深层水体体积输运的研究方法做了进一步探讨。 相似文献
17.
The study describes a new fixed-frequency Stokes wave theory that differs from previous Stokes wave theories that fix the wave number. The present wave expansion analytically reveals that the wavelength increases with wave height and exceeds than the wavelength obtained by linear wave theory. A method proposed to comparably transform the wave celerity of Fenton's [Fenton, J.D., 1985. A fifth-order Stokes theory for steady waves. Journal of Waterway, Port, Coastal and Ocean Engineering 111, 216–234.] wave theory to the present one. A direct calculation of the wavelength is introduced for practical solutions, avoiding the need to solve a nonlinear equation using an iterative numerical method. 相似文献
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本文提出了一种地震折射液的虚拟射线理论,根据该理论,只要已知地表层的速度,即可直接由折射波信息提取地震参数,从而可实现折射界面的反演。 文中通过实际介质模型的计算机实验结果,验证了该理论的正确性。 相似文献