光子晶体光纤的色散特性

本文用有效折射率模型 ,分析了光子晶体光纤的色散特性 ,定量给出了光子晶体光纤双折射特性与光纤参数之间的关系 ,指出了光子晶体光纤具有多个零色散波长 ,对相关现象作出了合理的解释。     

WDM系统中色散的实时监测

简单地推导了相位调制下的单音频率在传输光纤中其功率与光纤色散、光纤距离之间的关系，并介绍了在DWDM系统中可以利用相位调制法进行实时监测色散。此方法对于40GHz系统的色散实时监测提供了很好的参考方法。仿真结果表明，在未考虑光纤非线性效应的情况下有很高的精确性，当考虑非线性效应时，其传输距离会由于传输速率的影响而受到限制。     

Microstructure and Mechanical Behavior of Mechanically Alloyed ODS Ni-Base Superalloy for Aerospace Gas Turbine Application

The gamma prime precipitation strengthening behavior and oxide dispersion strengthening behavior of mechanically alloyed oxide dispersion strengthened (ODS) Ni-base superalloys have been investigated. The most important microstructural feature affecting the elevated temperature strength of ODS alloys was found to be the grain aspect ratio. Grain aspect ratio after zone annealing was sensitively related to the primary grain size in as-extruded Ni-base superalloy. There was a suitable range of primary grain size to obtain a coarse elongated grain structure after zone annealing. The large grain aspect ratio above a critical value of about 20 resulted in an increase in stress-rupture life more than two orders of magnitude at 950°C. The size and distribution of the gamma prime precipitates were dependent on the solution heat treatment conditions. The microstructural parameters on the gamma prime precipitates significantly affected on the stress-rupture property of ODS Ni-base superalloy at the intermediate temperature range.     

The dispersion relation and eigenfunction expansions for water waves in a porous structure

The Sollitt-and-Cross model of water-wave motion in a porous structure involves a free-surface condition which contains a complex parameter. This leads to two particular difficulties when this model is used in conjunction with eigenfunction expansion techniques. First of all the roots of the dispersion relation are themselves complex and therefore difficult to locate by standard numerical methods. Secondly, the vertical eigenfunction problem is not self-adjoint and standard expansion theorems do not apply. In this paper it is shown how these two difficulties may be resolved with the aid of the theories of, respectively, complex variables and non-self-adjoint differential operators. In particular, a method is described that allows the explicit calculation of the roots of the dispersion relation, and the appropriate expansion theorem is given.     

单模光纤的PMD

讨论了单模光纤的偏振模色散PMD，包括PMD与单模光纤的几何尺寸及应力的非圆对称的关系模间耦合的影响。PMD具有瞬时统计特性以及采用Monte Carlo模拟软件对光缆产品的PMDQ进行估算。     

常压蒸馏强化剂的研制与工业应用

研究以某炼油厂脱盐、脱水后的原油为原料 ,采用非离子型高分子有机聚合物作活性添加剂 ,强化常压蒸馏过程。介绍了常压蒸馏强化的机理 ,测定了强化剂对轻质油收率及产品质量的影响。实验室及工业应用结果表明 ,在原料油中加入 2 0 0 μg/ g的强化剂 ,可使轻质油收率提高 1.3个百分点以上 ,且产品质量有所改善。     

渐变芯各向异性光纤零偏振模色散的预言

本文用一阶微扰理论研究渐变芯各向异性光纤的偏振特性。结果表明,在单模区域,如果芯层和包层的材料双折射异号,那么零偏振模色散总是能达到。这项研究从理论上给出一个新的方法,设计具有零偏振模色散的色移保偏光纤。     

Measurement of Diffusion in Ternary Liquid Mixtures by Light Scattering Technique and Comparison with Taylor Dispersion Data

Results of diffusion coefficient measurements by dynamic light scattering (DLS) in the ternary liquid systems, glycerol–acetone–water (GAW), and cyclohexane–methanol–toluene (CMT), are reported. Data for the GAW system are compared with Taylor dispersion (TD) measurements in overlapping concentration regions close to the critical solution point at 298.15 K. A fit of the intensity autocorrelation function (ACF) could be used to predict values and explain the physical character of the corresponding diffusion coefficients. In the vicinity of the critical solution point, the DLS measurements reveal two and more hydrodynamic relaxation modes with well separated characteristic relaxation times. From the ACF, at least two effective diffusivities, D ₁ and D ₂, can be experimentally determined. Theoretical predictions reveal that they may result from pure mass diffusion and pure thermal diffusion transport processes. A possible physical meaning of the modes D ₁ and D ₂ in the ternary liquid mixtures is discussed. When we compare the transport modes from DLS with the Taylor dispersion results, only the slowest mode represents mass diffusion, and this mode agrees very well with one of the eigenvalues of Fick’s diffusion matrix. There is no relation between the mass diffusion mode from DLS and any one of the four diffusion coefficients obtained by TD.     

ATMOSPHERIC DISPERSION OF LARGE SCALE SPILLS

Large scale spills of volatile cryogenic or pressurized ambient temperature liquids often produce denser-than-air clouds which disperse in the atmosphere in a manner that is different than trace gases. These differences are due to density or gravity-induced effects such as turbulence damping from the stable density stratification, alteration of the ambient velocity field due to gravity flow, and the source momentum flux. Also important are thermodynamic effects such as aerosol formation and flash vaporization upon release, evaporative cooling, or heat transfer from the ground modifying cloud buoyancy and turbulence. In addition, chemical reaction effects such as hydrolysis with atmospheric water vapor, polymerization, or decomposition which also affects cloud density and thermodynamics can be important. These effects are very important close to the release point but also can have dramatic effects on the cloud as it disperses downwind.

Large scale tests involving releases of heavy gases have been conducted since the early 1970's. These tests have resulted in the discovery of previously unknown and important effects, the accumulation of data for model validation, as well as accident simulation and evaluation of accident mitigation equipment and techniques. A review of recent tests and some of the important results will be presented and examples from recent test series will be used in a review of our current understanding of dense gas dispersion.

The status of computer modeling in this field will also be reviewed with an emphasis on the problems associated with Gaussian models and recent progress in intermediate and 3D conservation equation models. Two of these models, FEM3 and SLAB will be compared to data so that the observed phenomena can be understood and so that predictions can be made regarding the consequences of accidental spills of sizes of concern to industry. FEM3 simulates the dispersion of the released gas by solving the time-dependent, three-dimensional conversion equations of mass, momentum, energy, and species. This model is used as a research tool and is designed to simulate as closely as possible the physics and thermodynamics governing the dispersion process. Steady-State SLAB is based on the crosswind-averaged form of the conservation equations, using similarity profiles to determine the crosswind dependence. It also conserves mass, momentum, energy and species, but is inherently one-dimensional, and is computationally simple and fast to use.     

Synthesis, Characterization, and Processing of Cordierite-Glass Particles Modified by Coating with an Alumina Precursor

The surfaces of cordierite and glass particles were modified by coating them with an alumina precursor using a precipitation process in the presence of urea. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy, X-ray diffraction, electrophoresis, and rheological measurements were used to characterize the coated powders. SEM and transmission electron microscopy morphologies of the coated powders revealed that amorphous and homogeneous coatings have been formed around the particles. The morphology of the coated powders showed a coiled wormlike surface. The coating Al₂O₃ layer dominated the surface properties of the coated glass and cordierite powders. The influence of the coating layer on the processing ability of cordierite-based glass-ceramics substrates by tape casting was studied in aqueous media. It could be concluded that the coating of the powders facilitates the processing and yields green and sintered tapes with denser, more homogeneous microstructures compared with the uncoated powders.