操作参数对PEM燃料电池中水迁移的影响

质子膜内水分和阴极多孔电极中液态水含量是PEM燃料电池正常运行的控制因素。本文给出了一个用于研究PEM燃料电池内水迁移的稳态、等温、两相流模型。模型耦合了连续方程、动量守恒方程和物质守恒方程,以及水在质子膜中传递方程。运用试验结果验证了模型的有效性。分析模拟结果表明,增大系统操作压力、升高电池操作温度和降低加湿温度将会使质子膜中水的净迁移通量增大;增大操作压力、降低操作温度和升高加湿温度会增加阴极CTL与GDL界面上液态水含量。     

Circulation model for water circulation and purification in a water Cerenkov detector

Owing to its low cost and good transparency, highly purified water is widely used as a medium in large water Cerenkov detector experiments. The water circulation and purification system is usually needed to keep the water in good quality. In this work, a practical circulation model is built to describe the variation of the water resistivity in the circulation process and compared with the data obtained from a prototype experiment. The successful test of the model makes it useful in the future design and optimization of the circulation/purification system.     

Simulation of water potential for the electronic structureof serine

First-principles, all-electron, \textit{ab initio} calculations have been performed to construct an equivalent water potential for the electronic structure of serine (Ser) in solution. The calculation is composed of three steps. The first step is to search for the configuration of the Ser + NH₂O system with a minimum energy. The second step is to calculate the electronic structure of Ser with the water molecule potential via the self-consistent cluster-embedding method (SCCE), based on the result obtained in the first step. The last step is to calculate the electronic structure of Ser with the dipole potential after replacing the water molecules with dipoles. The results show that the occupied states of Ser are raised by about 0.017~Ry on average due to the effect of water. The water effect can be successfully simulated by using the dipole potential. The obtained equivalent potential can be applied directly to the electronic structure calculation of protein in solution by using the SCCE method.     

Theoretical study of the electronic structure of LiNa and LiNa<Superscript>+</Superscript> molecules

Adiabatic potential energy, spectroscopic constants, dipole moments, and vibrational levels of the lowest electronic states of the alkali dimer LiNa molecule dissociating into Na (3s, 3p, 4s, 3d, and 4p) + Li (2s, 2p, 3s, and 3p) in ^1,3Σ, ^1,3Π, and ^1,3Δ symmetries are presented. Adiabatic results are also reported for ²Σ, ²Π, and ²Δ electronic states of the molecular ion LiNa⁺ dissociating into Li (2s, 2p, 3s, and 3p) + Na⁺ and Li⁺  + Na(3s, 3p, 4s, 3d, and 4p). We use an ab initio approach involving a non-empirical pseudopotential for the Li (1s²) and Na (1s²2s²2p⁶) cores and core valence correlation correction. A very good agreement is obtained for some lowest states of the LiNa and LiNa⁺ molecules for spectroscopic constants with the available theoretical works. The existence of numerous avoided crossings between electronic states of ²Σ and ²Π symmetries is related to the charge transfer process between the two ionic systems Li⁺Na and LiNa⁺.     

经典单色短峰水波理论的三阶完备解

针对经典的有限水深三阶单色短峰波,考虑环境均匀流效应,赋予一新的解析解,从而与原经典解析解构成完备的解析解.这就在第二阶解、第三阶解结构上显示出多种相互作用机制.     

Experimental Study on Soft X-ray Contact Microscopy for Biological Specimens

Using Hefei Synchrotron radiation as X-ray source and photoresist PMMA as recording medium, soft X-ray contact microscopic imaging experiment on hydrated leaf epidermal cells of a kind of dicotyledon is performed and its latent image is read out by a light microscope. Several main factors degrading the resolution of the image are discussed in detail.     

加速器电水锤数值模拟与实验研究

强流加速器水介质形成线放电或击穿形成的冲击波对陶瓷真空界面具有破坏作用。为获得该冲击载荷的信息,应用通用软件ANSYS/LS-DYNA建立了一种水下爆炸有限元模型,将电弧放电等效为爆炸源,模拟得到了冲击波传播时序、压力历史曲线及陶瓷板的加速度响应;为验证模型的有效性,应用"针-板"电极水开关在输出电脉冲40～50 ns、幅值100～300 kV可调的10级陡化前沿Marx发生器上开展了电水锤缩比实验研究。实测了不同击穿电压下冲击波峰压、波速和主脉冲宽度,并依据经验公式计算了放电沉积能量和冲击波能量,平均约17%的间隙放电能量转换为冲击波机械能。对冲击波能量与峰压关系进行了拟合,并与数值模拟结果进行了比较,二者变化趋势基本一致,量级上吻合较好。     

Investigation on optimization design of equivalent water depth truncated mooring system

The oil industry is now increasingly concentrating their efforts and activities in connection with developing fields in deeper waters, ranging typically from 500 m to 3000 m worldwide. However, the modeling of a full-depth system has become difficult presently; no tank facility is sufficiently large to perform the testing of a complete FPS with compliant mooring in 1000 m to 3000 m depth, within reasonable limits of model scale. Until recently, the most feasible procedure to meet this challenge seems to be the so-called “hybrid model testing technique”. To implement this technique, the first and important step is to design the equivalent water depth truncated mooring system. In this work, the optimization design of the equivalent water depth truncated mooring system in hybrid model testing for deep sea platforms is investigated. During the research, the similarity of static characteristics between the truncated and full depth system is mainly considered. The optimization mathematical model for the equivalent water depth truncated system design is set up by using the similarity in numerical value of the static characteristics between the truncated system and the full depth one as the objective function. The dynamic characteristic difference between the truncated and full depth mooring system can be minished by selecting proper design rule. To calculate the static characteristics of the mooring system, the fourth order Runge-Kutta method is used to solve the static equilibrium equation of the single mooring line. After the static characteristic of the single mooring line is calculated, the static characteristic of the whole mooring system is calculated with Lagrange numerical interpolation method. The mooring line material database is established and the standard material name and the diameter of the mooring line are selected as the primary key. The improved simulated annealing algorithm for continual & discrete variables and the improved complex algorithm for discrete variables are employed to perform the optimization calculation. The C++ programming language is used to develop the computer program according to the object-oriented programming idea. To perform the optimization calculation with the two algorithms mentioned above respectively and the better result is selected as the final one. To examine the developed program, an example of equivalent water depth truncated mooring system optimum design calculation on a 100,000-t, turret mooring FPSO in water depth of 320 m are performed to obtain the conformation parameters of the truncated mooring system, in which the truncated water depth is 160 m. The model test under some typical environment conditions are performed for both the truncated and the full depth system with model scale factor λ=80. After comparing the corresponding results from the test of the truncated system with those from the full depth system test, it’s found that the truncated mooring system design in this work is successful. Supported by the National Natural Science Foundation of China (Grant Nos. 10602055 and 40776007) and the Natural Science Foundation of China Jiliang University (Grant No. XZ0501)     

A primitive-variable Riemann method for solution of the shallow water equations with wetting and drying

A Riemann flux that uses primitive variables rather than conserved variables is developed for the shallow water equations with nonuniform bathymetry. This primitive-variable flux is both conservative and well behaved at zero depth. The unstructured finite-volume discretization used is suitable for highly nonuniform grids that provide resolution of complex geometries and localized flow structures. A source-term discretization is derived for nonuniform bottom that balances the discrete flux integral both for still water and in dry regions. This primitive-variable formulation is uniformly valid in wet and dry regions with embedded wetting and drying fronts. A fully nonlinear implicit scheme and both nonlinear and time-linearized explicit schemes are developed for the time integration. The implicit scheme is solved by a parallel Newton-iterative algorithm with numerically computed flux Jacobians. A concise treatment of characteristic-variable boundary conditions with source terms is also given. Computed results obtained for the one-dimensional dam break on wet and dry beds and for normal-mode oscillations in a circular parabolic basin are in very close agreement with the analytical solutions. Other results for a forced breaking wave with friction interacting with a sloped bottom demonstrate a complex wave motion with wetting, drying and multiple interacting wave fronts. Finally, a highly nonuniform, coastline-conforming unstructured grid is used to demonstrate an unsteady simulation that models an artificial coastal flooding due to a forced wave entering the Gulf of Mexico.     

高压液态重水的拉曼光谱研究

应用金刚石压腔结合拉曼光谱技术研究了重水在291 K,0.1～800 MPa条件下的拉曼谱图。结果表明：压力增大的过程中,重水的拉曼伸缩振动光谱向低频方向移动,并且频移和压力基本呈线性相关。频移没有突变,没有发生相的转变。将重水的拉曼谱峰分解为代表分子内O—D振动的高频峰和代表分子间氢键振动的低频峰。研究这两种不同类型谱峰的性质,发现代表分子间氢键的低频峰峰面积在不同的压力范围内呈现出不同的变化特征,压力对分子间氢键的影响并不是持续不变的。拉曼峰的峰面积反映的是产生这种拉曼峰的振动的数目,峰面积的变化反映了特征振动数目的变化。由于分子间氢键的强相互作用,水分子总是倾向于形成对称的空间五分子四面体结构,因此最大峰面积代表了最稳定的五分子团簇结构。