查询词典 natural oscillation

The low-dimensional Galerkin method is generalized to solve the flow around arbi-trarily translating circular cylinder.Active control problems of wakes behind circularcylinders are numerically investigated by only small number of modes.The in-line andtransverse oscillation of a circular cylinder with proper frequency produce Karman vor-tex street successfully in some subcritical regime,vhereas the transverse oscillation of acircular cylinder with 1.8 times the natural shedding frequency can effectively suppressthe Karman vortex street at a slightly supercritical Re.

将低维Galerkin方法推广至可以求解任意平移运动圆柱的绕流问题，用较少的模数值研究了圆柱尾迹的主动控制问题，在亚临界Re数下圆柱以适当的频率沿流向和横向振动均成功地激发出Karman涡街；而在略高于临界Re数下圆柱以1.8倍自然脱涡频率沿横向振动明显地抑制了Karman涡街；再现了超临界Re数横向及流向振动圆柱绕流的频率锁定等复杂非线性现象。

1Niche construction can lead to stable coexistence of diverse genotypes in spatially structured population, which supports a stable polymorphism even without heterozygote superiority.(2)With habitat deterioration, niche construction accelerates the formation of steady polymorphism and hence impedes the harmful influences of environment on the population, which might embody a life-history strategy of organism under the unfavorable environment.(3)Niche construction results in the coexistence with alternative polymorphism through genotype-environment feedback and limited gene flow.(4)The niche-constructing organism is an active force to alter its environment and hence the direction of natural selection in order to better survival.(5)Spatial dynamics and distribution pattern of metapopulation are profoundly influenced by time-lagged niche construction.(6)Metapopulation size can reach a fixed level in the recency effect and equal weighting of time lag but is statistical stability in primacy effect, which implies the primacy effect is most remarkable.(7)The increment in the relative weightingof each generation\' niche construction and the length of time lag are significant factors for system destabilization.(8)Moderate capacity of positive niche construction benefits the metapopulation persistence.(9)The narrowing of niche breadth can decrease the metapopulation size and thereby increase the extinction risk.(10)The coupled function of time lag and niche construction make the system oscillation and generate the spiral wave, spiral-broken and circular wave in heterogeneous habitat.The spatial distributions of metapopulation and resource content are complementary due to a phase lag of their both frequencies.(12)Metapopulation persistence with niche construction depends not only on the balance between colonization and extinction, but also on the balance between the ability of niche construction and natural dissipation of habitat.(13)Metapopula-tion can survive under certain condition when the percent of suitable patches in habitat is lower than the ration of extinction to colonization.(14)Two thresholds exist in the process of transition of habitat quality dynamics from unsuitable to suitable, which include the intensity of niche construction and the initial condition of system.(15)Metapopulation size is positive correlated with the ability of positive niche construction, which means that organism or population who has strongly positive influences on their environment plays an important role to maintain the available habitat.

通过上述几个方面的研究，主要得出以下15条结论：(1)生态位构建可使空间结构种群，甚至是在没有杂合子优势的条件下，形成多种可能的稳定基因型分布模式；(2)随着环境的破坏与恶化，种群的生态位构建作用加速其较早形成稳定多态以阻碍环境对种群的不利影响，解释了有机体在不利环境下的一种生活史对策；(3)生态位构建作用通过基因型—环境反馈机制及有限的基因交流导致基因型多态的稳定共存；(4)有机体的生态位构建作用是一种积极的动力改变环境进而改变其自然选择的方向；(5)生态位构建的时滞作用对集合种群动态和空间分布产生深刻影响；(6)集合种群大小在时滞的崭新效应和等权重效应下达到一固定值，而在首位效应下达到统计稳定，表明首位效应的影响最显著；(7)首位效应下生态位构建相对权重的增量和时滞的长度是影响系统不稳定性动态的关键因素；(8)适中的生态位构建强度有利于集合种群的续存；(9)生态位宽度变窄会减少集合种群的数量从而增加其灭绝风险；(10)时滞和生态位构建的双重作用使系统产生周期振荡，并在异质性环境中产生稳定的螺旋波，破碎的螺旋波和环形波三种分布模式；(11)集合种群与资源含量的空间分布因为相滞而互补；(12)具有生态位构建的集合种群续存不仅取决于侵占率与灭绝率之间的平衡，而且依赖于生态位构建能力同其生境的自然消耗速率之间的妥协；(13)当生境中适合侵占的斑块比例小于其侵占率与灭绝率之比时，生态位构建作用促使集合种群在一定条件下续存：(14)生境斑块的状态从不适合到适合转变过程中存在生态位构建强度和系统初始条件这两个阈值；(15)集合种群的大小同正生态位构建能力正相关，意味着对环境具有较强正作用的有机体对维持有效生境起积极作用。

In all of the movements and exercises the first and most important principle to remember is to allow the natural oscillation of the breath to be reflected in your body.

在所有的动作与运动中，需要记住的首要原则是：让呼吸自然的起伏波动反映在你的身体上。

Low frequency oscillation resonance mechanism of two-machine system was established in this paper. The relations between natural oscillation frequency and damping of two-machine system were analyzed.

理论推导了两机互联系统的共振机理，分析了两机互联系统固有频率与阻尼的关系。

The principle that weld pool size is well correlated with the frequency of natural oscillation excited on weld pool surface has been used for a real-time full-penetration control in the TIG welding of steel.

焊接熔池自然振荡频率与熔池尺寸之间存在良好对应关系的原理。

Finally, the so called critical oscillation frequency can be expressed as a function of oscillation amplitude and Grashof number in all the natural, mixed, and forced convection scenes.

最后，有关临界振动频率的经验公式在强制对流、混合对流以至於自然对流的形式皆不相同，本文皆已分别推导出来，且在三种的对流形式中都有相当平滑的曲线可以获得。

Proceeding from the kinetic equation, the occurrence of muscular fibre spontaneous oscillation is explained in a natural way, the period of isotonic spontaneous oscillation and the oscillation curves are consistent with experimental data, and some new theoretical results are presented.

从动力学方程出发，肌纤维自发振动的发生条件得到了自然解释，所给出的振动周期和振动曲线同实验结果相符，并给出了一些新的理论结果。

Firstly, the mechanism of heat transfer enhancement by oscillation heat surface is discussed in natural convection scene. For different oscillation amplitude and Rayleigh number, the frequency that the heat transfer rate of oscillation heat surface is higher than non-oscillation condition is found and called critical oscillation frequency. The limitation enhancement of similar physical model is still researched by this study in mixed and forced convection scenes for different amplitude and Grashof number. Generally, that a heat surface subject to a oscillation motion is advantageous to convective heat transfer is a well-known tuition.

首先探讨在垂直管道内振动高温面於自然对流领域内提升高温面热传效率的机制，并且针对不同的振幅与雷利数求得加入振动条件后，高温面散热效果可以优於稳态非振动高温面散热效果的临界振动频率；进而探讨当垂直管道流进入混合对流与强制对流范围时，在不同的振幅与葛瑞秀夫数下，亦可发现加入振动条件后，振动高温面之散热效果可以优於稳态非振动高温面散热效果的临界振动频率。

Firstly, the mechanism of heat transfer enhancement by oscillation heat surface is discussed in natural convection scene. For different oscillation amplitude and Rayleigh number, the frequency that the heat transfer rate of oscillation heat surface is higher than non-oscillation condition is found and called critical oscillation frequency. The limitation enhancement of similar physical model is still researched by this study in mixed and forced convection scenes for different amplitude and Grashof number.

首先探讨在垂直管道内振动高温面於自然对流领域内提升高温面热传效率的机制，并且针对不同的振幅与雷利数求得加入振动条件后，高温面散热效果可以优於稳态非振动高温面散热效果的临界振动频率；进而探讨当垂直管道流进入混合对流与强制对流范围时，在不同的振幅与葛瑞秀夫数下，亦可发现加入振动条件后，振动高温面之散热效果可以优於稳态非振动高温面散热效果的临界振动频率。

Numerical simulations and analytical results show: in longitudinal and oblique seas, ship may be subjected to primary parametric resonance with large roll amplitude and even capsizing, when encounter frequency is near the twice of roll natural frequency, wave length and ship length are of the same order and the wave height is larger than a certain value; in oblique seas, ship roll motion is a forcedly-parametrically excited oscillation, primary resonance occur as the encounter frequency is near the roll natural frequency, which may lead to large rolling and capsizing too.

数值仿真和解析分析结果表明：在纵浪和斜浪中，当遭遇频率接近船舶横摇固有频率的两倍，波长和船长接近，波高超过某一阈值的时候，船舶会发生主参数共振，产生大幅横摇甚至倾覆；在斜浪中，船舶发生的是参强激励横摇运动，遭遇频率接近横摇固有频率时，还会激起横摇主共振，同样会产生大幅横摇甚至倾覆。

I am accused of being overreligious," she said in her quiet, frank manner,"but that does not prevent me thinking the children very cruel who obstinately commit such suicide.""

客人们在卡罗利娜·埃凯家里，举止就文雅一些，因为卡罗利娜的母亲治家很严厉。

Designed by French fashion house Herm è s, this elegant uniform was manufactured in our home, Hong Kong, and was the first without a hat.

由著名品牌 Herm è s 设计，这件高贵的制服是香港本土制造，是我们第一套不配帽子的制服。