数值计算

The calculated free vibration frequencies and mode shapes of the whole structural model compare well with measured values. The influences of the various supporting conditions upon the frequencies of the trashrack and the free vibration characteristics of the single rack bars were then studied.

对栅架整体结构模型的自振频率和振型进行了量测，并与数值计算结果作了对比，二者基本吻合，说明成果是可靠的；此外，还对栅架支承条件对拦污栅自振频率的影响以及单根栅条的自振频率特性进行了探讨。

When applied random fields are trimodal, the critical properties including the possibility of the existence of the tricritical points and rcentrance phenomena are numerically analyzed in detail.

无规场取双峰和三峰分布时，通过数值计算对系统的临界特性包括三临界点和重入现象存在的可能性作了详细的研讨。

Fourthly, in baffled and unbaffled reactor, the improved ALE (Arbitrary Lagrange-Euler) method is applied to compute and simulate the 3D-flow field of air-water mixture, the velocity and kinetic energy distributions are analyzed and the processes of flow development are simulated, the results are validated with flow visualization experiment.

然后，采用改进的ALE(Arbitrary Lagrange-Euler)方法，对有、无挡板的反应器的气液混合物三维流场进行数值计算和模拟，分析了反应器内的速度和动能分布，模拟了流场的发展过程，并用流场显示实验进行了验证。

The altitude characteristics and velocity characteristics of three types of solid ducted rocket, which are choked solid ramrocket with fixed mass flow rate of fuelrich gas generator, unchoked one and the one working under fixed mass ratio of air to fuel, were numerically studied.

通过数值计算，分析了燃气流量固定的壅塞式固体火箭冲压发动机、等空燃比工作的固体火箭冲压发动机和非壅塞固体火箭冲压发动机的高度特性和速度特性。

Numerical solutions show that stockholders choose to exercise the investment option too early compared to the unleveled enterprise. Compared with value-maximizing policy, stockholders are inclined to overinvestment under the equity-maximizing investment policy, which affects the investment option value and optimal leverage choice, and does harm to the interests of bondholders. When debt constrained, the enterprise decreases the investment trigger first, and then increases it as constraints become more binding.

数值计算显示，与无负债企业相比，杠杆企业具有过度投资倾向以加快实现负债融资所带来的利息税盾价值；与企业价值最大化策略相比，在股东权益最大化目标下，股东具有较早执行投资期权的动机，影响投资期权价值和最优财务杠杆的选择，并侵害了债权人的利益。

With the support of a major research grant of Zhejiang Province (No. 001101027) and the Plan of Promoting Education of Excellence of Zhejiang University in the 21st Century, this dissertation is devoted to address the above problems and fabricate an L-band EDFA with low cost, high performance and technological innovation.First the mechanism of an erbium doped fiber amplifier is introduced. Various theoretical models based on classical rate propagation equations are summarized and compared for their applications. We use a modified numerical model based on the Giles model, which agrees with the experimental results well. This serves as the theoretical base for the whole thesis and will be used to optimize the characteristics of EDFAs. A novel method based on a map of noise figure and gain is proposed to analyze efficiently the dependence of the noise figure and gain for EDFAs on the EDF length and the pump power. The characteristics of various EDFAs are studied and compared.Secondly, some important parameters are introduced to describe the characteristics of EDFAs. The methods and the experimental setups for measuring the gain and noise figure of an EDFA are emphasized. We introduce how to measure the characteristics of each component of an EDFA, especially the gain and absorption coefficient of an erbium doped fiber.Thirdly, four types of simple and novel L-band EDFA structures with low noise, high gain and low gain ripple are proposed to satisfy the requirement of a DWDM system. They can be classified into two categories. In the first category, a single ASE pumping is served asa secondary pump. This category includes the following three types. Type: a new construction using a fiber Bragg grating in an unpumped EDF section at the input side. Type: a new structure of L-Band EDFA with two-stage pumps, which utilizes the forward ASE as a second pump.

本论文本着科技创新、服务于生产实践的精神，以设计价格低廉，性能优越、结构合理简单的L-band EDFA为目标，依托浙江省科技厅重大科学基金资助项目(001101027)和浙江大学振兴教育计划资助的全光网络的搭建—《光通信技术》课程实验建设项目，展开了如下工作：首先，介绍了掺铒光纤放大器的工作原理，归纳总结了基于速率方程基础的EDFA的各种理论模型，分析比较了各个模型的特点和适用场合，最终选择完善的Giles理论模型作为本论文分析设计EDFA的理论基础；针对实际实验条件提出了修正的EDFA模型的数值计算方法；创新地提出了增益—噪声系数全局分析法，直观有效地分析了EDFA的增益和噪声系数与掺铒光纤长度和泵浦功率的依赖关系，并对各种EDFA的性能作了全面的比较；第二，介绍了掺铒光纤放大器特性参数的定义与测量方法，重点介绍了噪声系数和增益系数的测量方法及实验装置；介绍了组成掺铒光纤放大器各组件的特性测量方法，重点介绍了测量掺铒光纤参数的方法和实验装置；第三，针对WDM系统对L-band EDFA谱平坦、低噪声、高增益的要求，我们创新地提出了四种不同的L-band EDFA结构，按设计思路可以分为两大类：一类是基于单抽运二级泵浦法，这一类包括在未泵浦掺铒光纤的输入端插入一根布拉格光纤光栅的两段L-band的EDFA的新结构；基于前向ASE光作为二级泵浦源推动下一级EDF工作的泵浦分配、两段级联L-band的EDFA的新结构；基于单根光纤光栅、泵浦分配、两段级联的EDFA；另一类则是基于同时应用前后向C-band ASE作二级泵浦源的双抽运法，如基于前后向ASE光作为二级泵浦源的三段级联L-band的EDFA的新结构。

Based on FEA mainly, secondly theory analysis,combined with joint tests, parametric analysis influencing loading-carrying capacity is carried out to acquire loading-carrying capacity formulae of unstiffened andstiffened joints.

本论文在研究加劲节点的过程中，主要以数值计算为主、理论推导为辅，并结合节点试验，共同分析影响加劲节点承载力的因素，以得到承载力的公式。

The flow field of a waterjet propulsion system,which is meshed by structural and unstructural grids,was calculated numerically with the steady state multiple frame of reference method.

采用结构化网格与非结构化网格相结合的方式划分了喷水推进系统的流场区域，采用稳态多参考系方法进行了数值计算。

Satisfactory results of numberical calculations usingS - matix variational approach for Cs + O2→Cs++O2- ion - pair formation system have been obtained.

作为上述公式的应用，对Cs+O_2→Cs~++O_2~-反应体系作了数值计算并取得了满意结果。

To study on the turbulent flow in a centrifugal pump with vaned diffusers, based on CFD method, three-dimensional turbulent flow field in suction chamber, impeller and diversion shell was calculated at three different operating conditions, and the velocity and pressure distribution in diversion shell were obtained.

以带有空间导叶的离心泵为研究对象，通过CFD方法，在三种工况下，对包括吸入室、叶轮和导流壳在内的全三维湍流场进行数值计算，获得了导流壳内的速度分布和压力分布。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。