LARGE TIME BEHAVIOR OF SOLUTIONS TO SOME DEGENERATE PARABOLIC EQUATIONS

The purpose of this paper is to study the limit in L ¹(Ω), as t → ∞, of solutions of initial-boundary-value problems of the form u_t ? Δw = 0 and u ∈ β(w) in a bounded domain Ω with general boundary conditions ?w/?η + γ(w) ? 0. We prove that a solution stabilizes by converging as t → ∞ to a solution of the associated stationary problem. On the other hand, since in general these solutions are not unique, we characterize the true value of the limit and comment the results on the related concrete situations like the Stefan problem and the filtration equation.     

Automorphisms for Skew PBW Extensions and Skew Quantum Polynomial Rings

In this work, I study the automorphisms of skew PBW extensions and skew quantum polynomials. I use Artamonov's works as reference for getting the principal results about automorphisms for generic skew PBW extensions and generic skew quantum polynomials. In general, if I have an endomorphism on a generic skew PBW extension and there are some x _i , x _j , x _u such that the endomorphism is not zero on these elements and the principal coefficients are invertible, then endomorphisms act over x _i as a _i x _i for some a _i in the ring of coefficients. Of course, this is valid for quantum polynomial rings, with r = 0, as such Artamonov shows in his work. We use this result for giving some more general results for skew PBW extensions, using filtred-graded techniques. Finally, I use localization to characterize some class the endomorphisms and automorphisms for skew PBW extensions and skew quantum polynomials over Ore domains.     

Molecular associations in acacia gums

The tendency of polysaccharides to associate in aqueous solution has long been recognised. Molecular associations can profoundly affect their performance in a given application due to its influence on the molecular weight, shape and size. This will ultimately determine how the molecules will interact with each other, with other molecules and with water. There are several factors, such as hydrogen bonding, hydrophobic association, ion mediated association, electrostatic interaction, concentration dependence and the presence of proteinaceous components, which affect this behaviour. Our objective is to highlight the role of the proteinaceous component, present in acacia gum, to promote associations when the gum is subjected to various processing treatments such as maturation, spray drying and irradiation. The results demonstrate the ability of the proteinaceous component to promote hydrophobic associations which influence the size and proportion of the arabinogalactan high molecular weight component (AGP). Heat treatment in solid state (maturation) increases the hydrophobic character of the gum and hence its emulsification performance. Spray drying also involves aggregation through hydrophobic association but changes the surface properties of peptide moieties to become more hydrophilic compared to the association promoted by the maturation treatment in the solid state. Irradiation induced cross-linking, in the presence of unsaturated gas, was used to introduce C–C bonds into the carbohydrate moiety and thus confirms the hydrophobic association prompted by the heat used in the maturation and spray drying. This association can be reversed by treatments, such as filtration or high pressure homogenisation. The results reported here reconcile the contradiction about structure of gum arabic proposed by the wattle-blossom and twisted hairy rope models and shows that the AGP fraction is basically an aggregated fraction made up of AG units stabilized by low molecular weight highly proteinaceous components.

Correlation between charge decay and solvent effect for melt-blown polypropylene electret filter fabrics

Melt-blown polypropylene electret fabrics are widely used as air filter media. However, its filtration efficiency gradually decays in application process. This paper is to investigate the correlation between filtration efficiency decay and solvent effect. Experimental results show that filtration efficiency displays a regular decrease when polypropylene electret fabrics are exposed to solvents in the sequence of water, ethanol, isopropanol and acetone. The results can be correlated to solubility parameter difference between polypropylene and solvent according to the Flory–Huggins swelling theory. Smaller solubility parameter difference leads to greater decay of filtration efficiency owing to greater affinity between polypropylene and solvent.     

Numerical modeling of deposition-release mechanisms in long-term filtration: validation from experimental data

A numerical phenomenological filtration model based on the combination of existing modeling approaches for simulating the transport of suspended particles in saturated porous medium is presented. The model accounts for the decreased physical straining with the distance from the inlet and the amount of deposited particles in the deposition kinetics. The particle release flux is a function of the local shear stress exerted by the flow on the pore surfaces. The proposed model is validated by interpreting a series of experimental data, realized in a laboratory sand column. The results show that the present model allows simulating the presence of a plateau in the breakthrough curves in the light of the shear stress conditions, and the spatial profile of deposited particles in the porous medium in the light of the straining profile.     

TD-LTE集群通信系统中基于小区筛选和AHP的切换算法研究

为了提高TD-LTE集群通信系统中用户的切换成功率以及降低阻塞率,文章根据TD-LTE及集群通信的特点,提出一种基于小区筛选(Filtration)机制结合层次分析法(Analytic Hierarchy Process)的切换算法(FAHP)。该算法在利用筛选机制保证目标小区满足通信需求的情况下,结合层次分析法选择出合理的目标小区。仿真分析结果表明,与传统的切换算法相比,该算法能有效提高用户的切换成功率,降低系统的阻塞率。     

Metabolic fingerprinting of high-fat plasma samples processed by centrifugation- and filtration-based protein precipitation delineates significant differences in metabolite information coverage

Metabolomics and metabolic fingerprinting are being extensively employed for improved understanding of biological changes induced by endogenous or exogenous factors. Blood serum or plasma samples are often employed for metabolomics studies. Plasma protein precipitation (PPP) is currently performed in most laboratories before LC–MS analysis. However, the impact of fat content in plasma samples on metabolite coverage has not previously been investigated. Here, we have studied whether PPP procedures influence coverage of plasma metabolites from high-fat plasma samples. An optimized UPLC-QTOF/MS metabolic fingerprinting approach and multivariate modeling (PCA and OPLS-DA) were utilized for finding characteristic metabolite changes induced by two PPP procedures; centrifugation and filtration. We used 12-h fasting samples and postprandial samples collected at 2 h after a standardized high-fat protein-rich meal in obese non-diabetic subjects recruited in a dietary intervention. The two PPP procedures as well as external and internal standards (ISs) were used to track errors in response normalization and quantification. Remarkably and sometimes uniquely, the fPPP, but not the cPPP approach, recovered not only high molecular weight (HMW) lipophilic metabolites, but also small molecular weight (SMW) relatively polar metabolites. Characteristic SMW markers of postprandial samples were aromatic and branched-chain amino acids that were elevated (p < 0.001) as a consequence of the protein challenge. In contrast, some HMW lipophilic species, e.g. acylcarnitines, were moderately lower (p < 0.001) in postprandial samples. LysoPCs were largely unaffected. In conclusion, the fPPP procedure is recommended for processing high-fat plasma samples in metabolomics studies. While method improvements presented here were clear, use of several ISs revealed substantial challenges to untargeted metabolomics due to large and variable matrix effects.     

驻极体空气过滤材料消静电实验研究

选取4片不同级别的驻极体空气过滤材料,对滤料消除静电效应前后的计数效率和PM2.5净化效率等性能参数进行了试验研究,消静电方法采用的是异丙醇浸泡法,试验用气溶胶为KCl固态气溶胶。试验结果表明:采用异丙醇浸泡法能够在一定程度上消除驻极体过滤材料本身所带的静电;消除静电效应后滤料对不同粒径颗粒的计数效率均有所下降,特别是颗粒物粒径越小,过滤效率下降的幅度也越大;消静电后滤料对PM2.5的净化效率也有所下降。研究结果揭示了采用驻极体过滤材料制造而成的带静电过滤器在实际使用过程中可能存在的因静电消失后带来的效率下降风险,试验数据也能为将来空气过滤器国家相关标准的修订提供参考建议。     

高性能水基钻井液处理剂研究进展及发展趋势

钻井液是石油钻井工程的“血液”,具有清洁井眼、保护钻具、稳定井壁和平衡地层压力等重要作用。本文综述了高性能水基钻井液处理剂的研究进展,主要包括抑制剂、润滑剂、包被剂和降滤失剂,包含了国内外的最新研究成果,也涉及国外油服公司和化学品公司在工程现场已经规模应用的先进产品。最后在现有高性能水基钻井液处理剂研究及应用的基础上,对其发展趋势进行了展望。     

Simple fabrication of Cu~(2+) doped calcium alginate hydrogel filtration membrane with excellent anti-fouling and antibacterial properties

Herein,copper ion doped calcium alginate(Cu~(2+)/CaAlg) composite hydrogel filtration membranes were prepared by using natural polymer sodium alginate(NaAlg) as raw material.The thermal stability and structure of the composite membranes were characterized by thermogravimetric analysis and infrared spectroscopy.The mechanical strength,anti-fouling performance,hydrophilicity and filtration performance of the membrane were studied.The results show that Cu~(2+)/CaAlg hydrogel membrane has excelle nt mechanical properties and thermal stability.The anti-swelling ability of the membrane was greatly enhanced by doping Cu~(2+).After three alternate filtration cycles,the flux recovery rate of Cu~(2+)/CaAlg hydrogel membrane can still reach 85%,indicating that the membrane has good antipollution performance.When the operation pressure was 0.1 MPa,the rejection of coomassie brilliant blue G250 reached 99.8% with a flux of 46.3 L m ~2 h ~1,while the Na_2 SO_4 rejection was less than 10.0%.The Cu~(2+)/CaAlg membrane was recycled after 24 h in the filtration process,and its flux and rejection rate did not decrease significantly,indicating that the hydrogel membrane has long-term application potential.The Cu~(2+)/CaAlg membrane has a wide range of applications prospect in dye desalination,fine separation and biopharmaceutical technology fields.