Observation and modelling of barrel droplets on vertical fibres subjected to gravitational and drag forces

Extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment or flow of drops from fibres as airflow velocity increases. A detailed experimental study of the aforementioned processes was conducted using glass filter fibres and H(2)O aerosol, which coalesce on the fibre to form barrel droplets with small contact angles. The droplets were predominantly observed in the Reynolds transition (or unsteady laminar) flow region. The droplet oscillation appears to be induced by the onset of vortexes in the flow field around the droplet as the increasing droplet size increases the Reynolds number. Flow in this region is usually modelled using the classical two-dimensional Karman vortex street, and there exist no 3D equivalents. Therefore to model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and inhibiting such oscillation. The agreement between the model and experimental results is acceptable for both the radial and transverse oscillations.     

Quantitative stability of multistage stochastic programs via calm modifications

In this paper, we revisit the quantitative stability of multistage stochastic programs. Different from the single calm modification used in Küchler (2008), we introduce two types of calm modifications which leads to a much simpler proof and tighter upper bound for the difference of optimal values of multistage stochastic programs under different stochastic processes than those of Küchler (2008). In addition, we avoid those restrictive assumptions in Küchler (2008) and the filtration distance in Heitsch et al. (2006). Finally, we illustrate our results with two numerical examples.     

溶剂浸泡对驻极体空气过滤材料性能的影响

通过过滤效率的跟踪测试,研究了聚丙烯熔喷非织造布驻极体空气过滤材料经各种不同溶剂浸泡后过滤性能的变化规律,比较了不同过滤效率测试方法对测试结果的影响。结果表明：溶剂浸泡后聚丙烯熔喷无纺布驻极体空气过滤材料的过滤效率都有不同程度的下降,下降幅度随水、甲醛、乙醇、异丙醇和丙酮的顺序逐渐增加,其下降规律与溶剂浸泡后滤材表面电位的衰减规律相一致,并与溶剂和聚丙烯分子间相互作用（溶胀作用）程度相关联。过滤效率对驻极体电场有很强的依赖性,其大小还与测试方法有关。     

Use of thiopropyl sepharose for preparation of 2-nitro-5-thiobenzoic acid

A simple method is described for preparation of 2-nitro-5-thiobenzoic acid (NTB), a compound with versatile applications but is commercially unavailable. In this method, NTB is produced by the reduction of 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) with thiopropyl sepharose, which is then separated from NTB by filtration. Two molecules of NTB can be generated from each molecule of DTNB when a large excess of thiopropyl sepharose is used. Thiopropyl sepharose is commercially available and can be readily regenerated for repeated use in the preparation of NTB. This method is simple and more effective than any other reported methods of NTB preparation.     

Behavior of extracellular polymers and bio-fouling during hydrogen fermentation with a membrane bioreactor

The characteristics of membrane fouling were investigated by examining the behaviors of extracellular polymer substances (EPSs) produced by hydrogen-producing bacteria during hydrogen fermentation from a submerged membrane bioreactor (MBR). The MBR consisted of a 1.4-L submerged membrane filtration tank and 3-L hydrogen fermenter. An intermittent suction operation was selected to maintain stable filtration performance. The operation of the suction pump was alternately shifted to ON for 7 min followed by OFF for 3 min, with bio-gas sparging at a flow rate of 5.0 L/m²/h (LMH), and manually regulated. Most of the EPS during the continuous hydrogen fermentation using an MBR had accumulated in the reactor because they were retained by the membrane by adsorption onto the polymeric membrane surface. The amount of proteins in the EPS extracted was increased to 179 mg/L and that of carbohydrates was increased to 58 mg/L. Cu²⁺, Mg²⁺, Zn²⁺ in the EPS were increased in the range of 1.6–3.3 mg/L. The high concentration of EPS that is produced has a higher chelation potential in the formation of ligand complexes with metals or cations than that in a conventional continuous stirred tank reactor (CSTR). The EPS directly affected the decrease in the permeate flux, which resulted in the clogging of the membrane.     

日常使用方式对一次性医用口罩微观结构和过滤效率的影响

The global spread of Corona Virus Disease 2019 (COVID-19) makes face masks become common protective equipment for daily life. This paper introduces the protection mechanism of disposable medical face masks, and investigates the changes of microstructure and filtration efficiency of disposable medical face masks after use and disinfection. It is helpful to get more understanding about protective effect of face masks.     

改进多路软硬件划分算法的筛选法

文章提出筛选法对基于抽象体系结构模板的多路软硬件划分算法进行了改进,从而使整个软硬件划分-任务调度过程的时间大大缩短。该方法在原算法的软硬件划分和任务调度过程之间加入了一个筛选步骤,对软硬件划分结果的硬件面积进行预估,依据预估的结果进行筛选,筛选后满足要求的划分方案才进行调度,从而大大减少了调度过程的工作量。实验结果表明,加入筛选步骤后,在最终结果性能基本不损失的前提下,整个软硬件划分-任务调度过程的速度有明显提高。     

The (in)significance of apparent viscosity in full-scale municipal membrane bioreactors

Ten pilot and full-scale municipal membrane bioreactor (MBR) plants throughout Europe were investigated during the period 2007–2008 using the Delft Filtration Characterisation method. Next to information on filterability the data also contain the necessary information to determine the apparent viscosity of activated sludge. The aim of this study was to quantify variations in the apparent viscosity of activated sludge in pilot and full-scale municipal MBR plants and correlate them with membrane performance. A statistical analysis was carried out in order to quantify the significance of the correlations between apparent viscosity and activated sludge characteristics. The main factor influencing activated sludge's apparent viscosity was found to be total suspended solids. Temperature was found not to have a direct impact on apparent viscosity within the range of temperatures of the pilot and full-scale municipal MBR plants studied (9.7–27.4°C). In terms of the reversible fouling potential and membrane performance, activated sludge filterability and MBR plant membrane permeability were not statistically affected by activated sludge's apparent viscosity variations. Therefore, even if apparent viscosity plays a major role in terms of oxygen transfer efficiency, it is not relevant when optimising membrane fouling control and membrane performance of current, full-scale municipal MBR applications.     

Precise Size-Selective Sieving of Nanoparticles Using a Highly Oriented Two-Dimensional Supramolecular Polymer

The development of size-selective membranes with well-defined nanopores towards the precise separation of nanometer-sized substances is a challenging task to achieve. Here a supramolecular membrane is presented that comprises a highly oriented, honeycomb-like, 2D supramolecular polymer on a polycarbonate filter support. It enables precise size-selective sieving of colloidal nanoparticles (NPs). Owing to the uniform parallel-aligned nanocavities within the 2D supramolecular polymers, the composite membrane shows a high size-selectivity with a sub-nanometer accuracy in the cutoff size of about 4.0 nm. In principle, the species of size-separable particles are unlimited, as demonstrated by quantum dots, noble metal, and metal oxide NPs. This supramolecular membrane combined with filtration advances the potential of NPs in terms of their monochromatic emission and size monodispersity, and also enables rapid removal of small magnetic NP adsorbents that are otherwise difficult to capture.     

Periodic Solutions to Porous Media Equations of Parabolic-elliptic Type

This paper is concerned with a equation, which is a model of filtration in partially saturated porous media, with mixed boundary condition of Dirichlet-Neumann type {∂_tb(u) - ∇ • a [∇u + k(b(u))] = f \qquad in \quad (0, ∞) × Ω u = h(t, x) \qquad on \quad (0, ∞) × Γ_0 v • a [∇u + k(b(u))] = g(t, x) \qquad on \quad (0, ∞) × Γ_1 We have proved that there exists one and only one periodic solution of the problem under the data f, g and h with same period. Moreover, we have proved that the unique periodic solution ω is asymptotically statble in the sense that for any solution u of the problem b(u(t)) - b(ω(t)) → 0\qquad in L²(Ω) as t → ∞.