共查询到18条相似文献，搜索用时 437 毫秒
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大鹏湾夜光藻赤潮的营养动力学模型 总被引：1，自引：0，他引：1
根据大鹏湾夜光藻Noctilucascintillans赤潮发生要素的结构关系，利用生物种群生态学和营养动力学的原理，提出夜光藻－硅藻－营养物质三者相关的动力学模型，模型中的参数将体现海况环境的有关因素。文中利用微分方程动力系统理论对模型作出定性分析，给出赤潮发生与否的某些判别条件；并根据1991年3月1日一4月30日大鹏湾所发生的夜光藻赤潮数据分别对1次赤潮全过程和有连续3次赤潮的情形进行了有效的数值模拟，所得结果对赤潮的预测预报研究有一定的参考价值。 相似文献
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大鹏湾夜光藻赤潮的营养动力学模型 总被引：11，自引：0，他引：11
根据大鹏湾夜光藻赤潮发生要素的结构关系，利用生物种群生态学和营养动力学的原理，提出夜光藻－硅藻－营养物质三者相关的动力学模型，模型中的参数瘵体现海况环境的有关因素。文中利用微分方程动力系统理论对模型作出定性分析，给出赤潮发生与否的某些判别条件；并根据１９９１年３月１日－４月３０日大鹏湾所发生的夜光藻赤潮数据地１次赤潮全过程和有连续３次赤潮的情形进行了有效的数值模拟，所得结果对赤潮的预测预报研究有一 相似文献
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Nonlinear Dynamics and Bifurcations of a Supercavitating Vehicle 总被引：1，自引：0，他引：1
In this effort, a numerical study of the bifurcation behavior of a supercavitating vehicle is conducted. The vehicle model is nonsmooth; this is a result of the planing force acting on the vehicle. With a focus on dive-plane dynamics, bifurcations with respect to a quasi-static variation of the cavitation number are studied. The system is found to exhibit rich and complex nonlinear dynamics including nonsmooth bifurcations such as the grazing bifurcation; smooth bifurcations such as Hopf bifurcations, cyclic fold bifurcations, and period-doubling bifurcations; and aperiodic behaviors such as transient chaotic motions and chaotic crises. The tailslap phenomenon of the supercavitating vehicle is identified as the consequence of a Hopf bifurcation followed by a grazing event. It is shown that the occurrences of these bifurcations can be delayed or triggered earlier by using dynamic linear feedback control laws employing washout filters. 相似文献
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A time-domain 3 Degrees of Freedom model is developed to investigate nonlinear dynamics and impact loads during float-over installations, which generally involve multi-body interactions between wave-induced vessel motions and nonlinear constraint components. By replacing the time-consuming convolution in calculating the retardation function, a more efficient method, i.e. state-space model, is applied to evaluate part of the radiation force. The established model, incorporating the multi-body interactions, is applied to study the nonlinear impact on Leg Mating Unit (LMU) by considering the sway, heave and roll motions of the float-over system. The structural characteristics are considered when modelling the characteristics of LMU. The dynamic behaviors of a given system is investigated in the form of bifurcation diagrams, along with impact map, amplitude spectrum and power spectral density (PSD). It is found that bifurcation phenomena, or a large angle of docking cone could dominate the installation due to the increased impact loads. 相似文献
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锗对几种微藻生长的影响 总被引：6，自引：0，他引：6
根据锗对微囊藻、聚球藻和钝顶螺旋藻生长影响的研究表明，锗对藻类生长的影响因种类而异：微囊藻对锗的耐受能力较强，在培养范围内（０￣２５ｍｇ／ｄｍ＾３，ＧｅＯ２），锗对其生长具促进作用；钝顶螺旋藻的正常生长浓度要低于２５ｍｇ／ｄｍ＾３，当锗浓度达２５ｍｇ／ｄｍ＾３时，生长受明显抑制；聚球藻对锗较敏感，锗浓度超过１２．５ｍｇ／ｄｍ＾３时会抑制其生长，甚至起毒害作用。文中还探讨了锗对藻类生长影响与藻细胞所 相似文献
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铅离子对海洋浮游植物生长影响的研究 总被引：4，自引：0，他引：4
采用一次培养实验方法，研究了Pb^2 对8种常见海洋浮游植物生长的影响。在Logistic生长模型的基础上，结合Lorentz方程和GaussAmp方程，引入Pb^2 浓度项，建立新的方程来描述Pb^2 存在条件下海洋浮游植物的生长过程，并且通过对实验数据的非线性拟合，验证该方程是合理的。实验拟合结果表明，高浓度Pb^2 (c(Pb^2 )≥2500μg／L)对浮游植物的生长普遍有抑制作用，而较低浓度Pb^2 (c(Pb^2 )≤100μg／L)则易促进赤潮异弯藻(Heterosigma akashiuo Hada)、旋链角毛藻(Chaetoceros curvisetus Cleve)、三角褐指藻(Pheodactylum tricormutum Bohlin)、中肋骨条藻(Skeletonema costatum (Greville) Cleve)、青岛大扁藻(Platymonas helgolanidica Kylin var tsingtaoensis)、亚心型扁藻(Platymonas subcordiformis)的生长，它们最佳的促进生长浓度分别为：1991、2523、101、1488、627、509μg／L,但对于海洋原甲藻(Prorocentrum micans Ehrenberg)、裸甲藻(Gymnodinium sp．)的生长没有明显的影响。应用该方程在一定程度上不仅可以根据浮游植物的生长情况．推测相应海区的Pb^2 污染物浓度；而且也可以预测不同浓度Pb^2 条件下，相应海区的海洋浮游植物的生长情况。 相似文献
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海洋生态系统动力学模型的可预测性是模型应用的重要限制因子之一,而模型稳定性则是模型可预测性的前提。本文提出了一个基于降维理论的方法,用于研究质量守恒的营养盐-浮游植物-浮游动物-碎屑(NPZD)这类海洋生态系统动力学模型的稳定性和Hopf分岔。研究结果显示,NPZD模型的非奇异平衡点是稳定的,而当模型参数在临界值附近变动时可能会发生Hopf分岔。同时,本文采用数值模拟的方法对该理论分析结果进行了实例验证。本文提出的基于降维理论的方法能够从理论上有效分析质量守恒系统的稳定性问题和Hopf分岔。 相似文献
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Analytical expressions of the bifurcation boundaries for symmetric spread mooring systems 总被引：4，自引：0，他引：4
For a general symmetric Spread Mooring System .(SMS), the five necessary and sufficient conditions for stability are derived analytically. It is shown that only two conditions are dominant in symmetric ship moorings. The equations derived in this paper provide analytical means for determining static and dynamic loss of stability, as well as elementary singularities and roots to chaos, of symmetric SMS configurations, such as those recommended by the American Petroleum Institute. Thus, first it becomes easy to identify the morphogenesis occurring when a bifurcation boundary is crossed; and second, it is possible to determine the dependence of a symmetric SMS on any design parameter—such as mooring line length, orientation, pretension, etc. Theoretical results are verified by comparison to numerical results generated with nonlinear dynamics and codimension one and two bifurcation theory. The mathematical model of the SMS consists of the nonlinear third order manoeuvring equations without memory of the horizontal plane slow motion dynamics—surge, sway, and yaw—of a vessel moored to several terminals. Mooring lines are modeled as synthetic nylon ropes, chains, or steel cables. External excitation consists of time independent current, wind, and mean wave drift forces. 相似文献