固支简支端部边界条件下同轴圆柱壳体的流致不稳定性研究

基于Paiedoussis等同轴圆柱壳体流致不稳定性的数学模型和研究方法，分析了固支－简支端部约束条件下同轴圆柱壳体系统的流致不稳定性，结果表明：同两端固支相比，固支－简支端部边界下壳体系统的失稳临界流速更低。     

沸腾通道中汽液两相流压力降型不稳定性集总参数非线性模型

使用集总参数非线性型模型来分析蒸发管中汽液两相流压力降型劝，结果表明：压力降型不稳定性可以用二阶常微分方程来描述。     

应用隔板抑制液体火箭发动机不稳定燃烧的数值模拟

对液体火箭发动机燃烧室内有隔板和无隔板两种情况进行了燃烧不稳定性数值模拟。气相控制方程组在欧拉坐标系下描述，对方程组用预测校正步差分格式求解；液相控制方程组在拉格朗日坐标系下描述，液相蒸发规律用高压蒸发模型来计算。湍流模型采用ｋ－ε双方程模型，湍流燃烧模型采用ＥＢＵ模型。在计算出有隔板和无隔板的燃烧室内热态解稳态参数值后，通过加入初始扰动来模拟爆炸弹对燃烧稳定性的评定试验，比较了燃烧室头部有隔板和     

On Destabilization via Active Stiffness

Corless and Leitmann [2] have shown that a damped simple oscillator can be destabilized by varying the spring stiffness. The present note establishes that this result is closely related to the variational approach to absolute stability theory [1,6] both in substance and in method of proof. In particular, several key ideas employed in [2] appear in the work of Brockett [1].     

板状结构流致振动的研究

采用二维不可压缩无粘流体模型，探讨了板状结构的流致振动问题。发现板在两端简支、中点联结松动时，结构首先出现屈曲失稳，而不会发生颤振失稳。求得了具体结构参数情况下的第一阶屈曲临界流速，计算了结构参数变化对临界流速的影响。     

Elastic-plastic fracture mechanics assessment of test data for circumferential cracked pipes

This paper presents experimental validation of two reference stress based methods for circumferential cracked pipes. One is the R6 method where the reference stress is defined by the plastic limit load. The other is the enhanced reference stress method, recently proposed by the authors, where the reference stress is defined by the optimised reference load. Using 38 published pipe test data, the predicted maximum instability loads according to both methods are compared with the experimental ones for pipes with circumferential through-thickness cracks and with part circumferential surface cracks. It is found that the R6 method gives conservative estimates of the maximum loads for all cases. Ratios of the experimental maximum load to the predicted load range from 0.54 to 0.98. On the other hand, the proposed method gives overall closer maximum loads than R6, compared to the experimental data. However, for part through-thickness surface cracks, the estimated loads were slightly non-conservative for four cases, and possible reasons are fully discussed.     

Mathematical Simulation of Radiation Instability and a Possible Method of Taking Instability into Account in Realization of the Unit of Power of Laser Radiation and Dissemination of the Unit of Power

The present study is devoted to mathematical simulation of the instability of laser radiation. An algorithm for establishing the shape of continuous laser radiation received at the input of a measuring system is presented.     

Dynamic asymmetrical instability of elastic–plastic beams

Dynamic instability of elastic–plastic beam is investigated by employing a three-degree-of-freedom (3-DoF) beam model. Especially, asymmetrical instability induced by symmetrical load is discussed. The asymmetrical instability is considered as a second-order buckling mode. Four types of perturbations, i.e., geometrical misalignment, material property mismatch, unsymmetry of applied load and disturbance of boundary conditions, are introduced to activate the asymmetrical responses. The asymmetrical response is characterized by a modal participation factor α₂ which corresponds to an asymmetrical mode shape. Phase plane trajectories and Poincaré map are used to illustrate the chaotic characteristics of the beam response. Results show that if the perturbations are small enough, the perturbation type has negligible influence on the critical load for the occurrence of the asymmetrical instability, which implies that the asymmetrical instability is an intrinsic feature of the beam system. However, with the increase of the magnitude of the perturbations, the influence of the asymmetrical vibration is expanded to a large extension of loading parameter.     

Modulation instability in a dispersion oscillating fibre pumped by a broad band pulse

We numerically investigate the modulation instability generated in a dispersion oscillating fibre pumped by a chirped pulse with a broad bandwidth. We highlight that the side bands are wide, not symmetric in frequency about the pump and several instantaneous side bands can spectrally overlap with each other in one side, while they are well located in the other side. We also show that the spectral distribution can be intuitively explained with an analogy in which the fibre is pumped by a tuneable continuous wave.     

Modelling and inference reveal nonlinear length-dependent suppression of somatic instability for small disease associated alleles in myotonic dystrophy type 1 and Huntington disease

More than 20 human genetic diseases are associated with inheriting an unstable expanded DNA simple sequence tandem repeat, for example, CTG (cytosine–thymine–guanine) repeats in myotonic dystrophy type 1 (DM1) and CAG (cytosine–adenine–guanine) repeats in Huntington disease (HD). These sequences mutate by changing the number of repeats not just between generations, but also during the lifetime of affected individuals. Levels of somatic instability contribute to disease onset and progression but as changes are tissue-specific, age- and repeat length-dependent, interpretation of the level of somatic instability in an individual is confounded by these considerations. Mathematical models, fitted to CTG repeat length distributions derived from blood DNA, from a large cohort of DM1-affected or at risk individuals, have recently been used to quantify inherited repeat lengths and mutation rates. Taking into account age, the estimated mutation rates are lower than predicted among individuals with small alleles (inherited repeat lengths less than 100 CTGs), suggesting that these rates may be suppressed at the lower end of the disease-causing range. In this study, we propose that a length-specific effect operates within this range and tested this hypothesis using a model comparison approach. To calibrate the extended model, we used data derived from blood DNA from DM1 individuals and, for the first time, buccal DNA from HD individuals. In a novel application of this extended model, we identified individuals whose effective repeat length, with regards to somatic instability, is less than their actual repeat length. A plausible explanation for this distinction is that the expanded repeat tract is compromised by interruptions or other unusual features. We quantified effective length for a large cohort of DM1 individuals and showed that effective length better predicts age of onset than inherited repeat length, thus improving the genotype–phenotype correlation. Under the extended model, we removed some of the bias in mutation rates making them less length-dependent. Consequently, rates adjusted in this way will be better suited as quantitative traits to investigate cis- or trans-acting modifiers of somatic mosaicism, disease onset and progression.