Multi-dimensional hydrodynamic code SOVA for interfacial flows: Application to the thermal layer effect

Eulerian, three-dimensional, numerical code, which conserves mass, momentum and energy simultaneously both in the Lagrangian and remap steps, is developed. The use of special form of linear viscosity provides a weaker time step restriction as compared with the Courant condition. The code is designed to investigate the multi-material problems, including dusty flows. The performance of the code is illustrated by the modeling of shock wave interaction with a dusty thermal layer. Received 15 June 1998/ Accepted 6 January 1999     

An efficient algorithm for detecting particle contact in non-uniform size particulate system

Algorithms for detecting particle collision play an important role in the discrete element method (DEM) for the simulation of granular flow systems since the time taken to detect the contact pairs usually occupies a considerable proportion of the total CPU time for the simulation. In this study, we developed a new octree algorithm called multi-octree algorithm, for detecting candidate contact pairs. The so-called multioctree algorithm adopts the topology of octree for detecting possible contacts, in which t...     

Formation and analysis of particulate carbon in a synthetic lubricant

The formation of discrete carbonaceous particles has been investigated for a conventional synthetic ester-based lubricant degraded in thermal and thermal–oxidative environments. Experimental factors included oxidative and nonoxidative environments, high and low humidities, and the presence or lack of a metal catalyst surface, with all samples generated at 250 °C. Characterization performed for changes in antioxidant content, IR spectroscopy, molecular weight, total acid number, viscosity, and uv/vis absorbance spectrometry were used to determine the influences of the aforementioned variables on the rates of oil degradation and formation of high-molecular-weight species. Discrete carbonaceous particle formation was analyzed using Einstein's relationship for the viscoelastic behavior of particles in Newtonian fluids and by calculating associated radii of gyration. This viscoelastic behavior of the particles in solution is used to demonstrate how the absorption behavior of the carbonaceous degradation products tracks the discrete particulate species. The results show the formation of particulate species to be diffusion-limited after antioxidant depletion, and optical absorption analysis is shown to be a viable technique for monitoring the formation of discrete carbonaceous particles during lubricant degradation. Received: 29 February 2000/Accepted: 3 January 2000     

Titanium compounds as coatings on polystyrene latices and as hollow spheres

Sub-micron-sized anionic polystyrene latices have been coated with uniform layers of amorphous titanium dioxide by hydrolysis of titanium tetrabutoxide in ethanolic solutions containing the polymer cores. The thickness of the coating layer could be altered by adjusting the concentration of titanium tetrabutoxide and the amount of polymer latex added to the system. Hollow colloidal spheres of crystal titanium dioxide were obtained by calcination of the so-coated polystyrene latices at an elevated temperature. Received: 29 July 1999/Accepted in revised form: 15 October 1999     

针剂中异物的光电检测方法研究

针剂在实际生产过程中容易混入异物颗粒,异物颗粒影响人体健康,因此针剂在出厂前必须进行异物检测.本文提出了一种基于光阻法的针剂异物的检测方法,介绍了检测原理及其信号处理方法,单瓶静态实验表明,该方法与人工检测方法比较,符合率为96.30%.针对检测区域和测试时间过小所造成的漏检可能,提出了双光路检测方法,并通过实验论证了其可行性.     

Dust trapping in vortex pairs

The motion of tiny heavy particles transported in a co-rotating point vortex pair, with or without particle inertia and sedimentation, is investigated. The dynamics of non-inertial sedimenting particles is shown to be chaotic, under the combined effects of gravity and of the circular displacement of the vortices. This phenomenon is very sensitive to the particles’ inertia, if any. By using a nearly hamiltonian dynamical system theory for the particles’ motion equation written in the rotating reference frame, one can show that small inertia terms of the particles’ motion equation strongly modify the Melnikov function of the homoclinic trajectories and heteroclinic cycles of the unperturbed system, as soon as the particles’ response time is of the order of the settling time (Froude number of order unity). The critical Froude number above which chaotic motion vanishes and a regular centrifugation takes place is obtained from this Melnikov analysis and compared to numerical simulations. Particles with a finite inertia, and in the absence of gravity, are not necessarily centrifuged away from the vortex system. Indeed, these particles can have various equilibrium positions in the rotating reference frame, like the Lagrange points of celestial mechanics, according to whether their Stokes number is smaller or larger than some critical value. An analytical stability analysis reveals that two of these points are stable attracting points, so that permanent trapping can occur for inertial particles injected in an isolated co-rotating vortex pair. Particle trapping is observed to persist when viscosity, and therefore vortex coalescence, is taken into account. Numerical experiments at large but finite Reynolds number show that particles can indeed be trapped temporarily during vortex roll-up, and are eventually centrifuged away once vortex coalescence occurs.     

Parameter inference in small world network disease models with approximate Bayesian Computational methods

Small world network models have been effective in capturing the variable behaviour of reported case data of the SARS coronavirus outbreak in Hong Kong during 2003. Simulations of these models have previously been realized using informed “guesses” of the proposed model parameters and tested for consistency with the reported data by surrogate analysis. In this paper we attempt to provide statistically rigorous parameter distributions using Approximate Bayesian Computation sampling methods. We find that such sampling schemes are a useful framework for fitting parameters of stochastic small world network models where simulation of the system is straightforward but expressing a likelihood is cumbersome.     

蓄压型液舱用于沿海LNG运输的研究

提出了解决沿海液化天然气运输的一种方案。针对小型LNG船的关键设备蓄压型独立液舱存储液化天然气,进行了理论计算和模拟试验,并对影响液舱压力和运输时间的主要因素进行了研究分析。对LNG运输的时间进行预测,论证了该种小型LNG船在近海或沿海运输的可行性,为开发用于近海运输的小型LNG船,提供了理论依据。