Modelling of an underground waste disposal site by upscaling

In this paper, we study the global behaviour of an underground waste disposal in order to have an accurate upscaled model suitable for the computations involved in safety assessment processes. We start from a detailed model describing the transport of pollutant leaking from a high number of units. Using the method of homogenization, going to the limit, we obtain first a macroscopic model where the sources are now appearing globally. Then we compute a first‐order matched asymptotic expansion and we give the error estimates for this approximation. Copyright © 2004 John Wiley & Sons, Ltd.     

The Newton filtration and d-determination of bifurcation problems related to C~0 contact equivalence

In this paper, from the Newton filtration's point of view, we construct the singular Riemannian metric and use the method in singular theory to study the bifurcation problems, and give the sufficient condition of d-determination of bifurcation problems with respect to C0 contact equivalence. The special cases of the main result in this paper are the results of Sun Weizhi and Zou Jiancheng.     

一类递减信息族的性质及其证明

构造了一类基于Brown运动的单参数递减信息族{Ht}t≥0，并证明了其某些性质。     

FREE BOUNDARY PROBLEM ARISING FROM EVAPORATION FROM POROUS MEDIUM

ＦＲＥＥＢＯＵＮＤＡＲＹＰＲＯＢＬＥＭＡＲＩＳＩＮＧＦＲＯＭＥＶＡＰＯＲＡＴＩＯＮＦＲＯＭＰＯＲＯＵＳＭＥＤＩＵＭＹＡＮＧＬＩＰＩＮＧ（杨力平）（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ＴｓｉｎｇｈｕａＵｎｉｖｅｒｓｉｔｙ，Ｂｅ...     

两指标随机过程的停止

~~(2 ) z∈ R+ 2 ,{z∈ D′{ D相似文献   

气水反冲滤池在我省的应用

过滤工艺是水处理工艺中的关键工艺，直接影响水处理效果。本文详细介绍了气水反冲滤池具有处理效果好，节约反冲洗水量，降低能耗，减少运行成本等优点，在我省具有广阔的应用前景。     

Industrial multi-stage continuous filtration process: influence of operating parameters

This paper presents a theoretical study of the effects of operating parameters on the behaviour of an industrial crossflow filtration unit. A continuous three stage unit and its application to yeast cell harvesting are considered. A model of standard industrial processing is developed, and the influence of dead volumes, start-up procedure, crossflow and permeation velocities and maximum transmembrane pressure are investigated. Concentration factors are discussed with respect to the effects due to dead volumes.     

Simple preparation and characteristics of silk fibroin microsphere

We investigated the biomaterial and pharmaceutical utility of pure silk fibroin (SF) protein as a possible for separation, using Sephadex G-25 gel filtration chromatography and simply preparing SF microsphere particles (SFMP) by spray dryer. Also, some of its physicochemical properties and morphology were investigated. Obtaining microspheres and/or submicronic particles by spray dryer method was accelerated or completed with the transition from the random coil to the β-sheet structure during spray dryer treatment. It was identified by the basic Fourier transform infrared spectroscopy of SFMP. The various pH range of SFMP’s swelling ratio is dependent on the pH of the solution, not on the occurred gelation. Morphologically, SFMP was spherical in shape, and particles, average 2±10 μm in size, were observed by scanning electron microscope and particle analyzer, respectively. The average molecular weight (M_W) of pure SF protein dissolved in calcium chloride is about 61,500 g/mol as measured by gel permeation chromatography.     

Cellulase retention and sugar removal by membrane ultrafiltration during lignocellulosic biomass hydrolysis

Technologies suitable for the separation and reuse of cellulase enzymes during the enzymatic saccharification of pretreated corn stover are investigated to examine the economic and technical viability of processes that promote cellulase reuse while removing inhibitory reaction products such as glucose and cellobiose. The simplest and most suitable separation is a filter with relatively large pores on the order of 20–25 mm that retains residual corn stover solids while passing reaction products such as glucose and cellobiose to form a sugar stream for a variety of end uses. Such a simple separation is effective because cellulase remains bound to the residual solids. Ultrafiltration using 50-kDa polyethersulfone membranes to recover cellulase enzymes in solution was shown not to enhance further the saccharification rate or overall conversion. Instead, it appears that the necessary cellulase enzymes, including β-glucosidase, are tightly bound to the substrate; when fresh corn stover is contacted with highly washed residual solids, without the addition of fresh enzymes, glucose is generated at a high rate. When filtration was applied multiple times, the concentration of inhibitory reaction products such as glucose and cellobiose was reduced from 70 to 10 g/L. However, an enhanced saccharification performance was not observed, most likely because the concentration of the inhibitory products remained too high. Further reduction in the product concentration was not investigated, because it would make the reaction unnecessarily complex and result in a product stream that is much too dilute to be useful. Finally, an economic analysis shows that reuse of cellulase can reduce glucose production costs, especially when the enzyme price is high. The most economic performance is shown to occur when the cellulase enzyme is reused and a small amount of fresh enzyme is added after each separation step to replace lost or deactivated enzyme.     

Use of intermittent jets to enhance flux in crossflow filtration

This paper deals with the influence of a new flow unsteadiness on the permeate fluxes in crossflow filtration. A pneumatically controlled valve generates intermittent jets from the main flow, causing the formation of large vortices moving downstream along the tubular membrane. The main results of the numerical calculation of such flows are given. The experimental study was carried out by filtering a bentonite suspension through an ultrafiltration mineral membrane. Time evolutions of flux were achieved in steady and unsteady operating conditions. Results concerning the influence and limits of the nozzle to tube diameter ratio and the jet velocities are discussed. The applicability of such an unsteady flow is examined with a view to effects on energy consumption and possible viscosity effects.