Production of biodiesel from waste fryer grease using mixed methanol/ethanol system

Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester. To untangle this problem, two-stage (acid and alkali catalyzed) method was used for biodiesel synthesis. More than 90% ester was obtained when two-stage method was used compared to ∼ 50% ester in single stage alkaline catalyst. In the case of mixed alcohol, a relatively smaller amount of ethyl esters was formed along with methyl esters. Acid value, viscosity, and cetane number of all the esters prepared from WFG were within the range of the ASTM standard. Esters obtained from WFG showed good performance as a lubricity additive.     

IP网络资源调度与接纳控制技术研究

从IP QoS技术的研究现状出发,结合IETF的研究成果与电信网NGN的技术发展方向,阐述基于策略的端到端接纳控制框架的技术原理,在各大标准组织的技术框架内,给出一个具体的、切实可行的实现方法。     

Prediction of fire classification for wood based products. A multivariate statistical approach based on the cone calorimeter

Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd.     

Polymorphisme du dioxotriplomb (II) tetraoxosulfate (VI) Pb3O2(SO4) a basse temperature. II - Etude structurale de la phase ferroelastique gamma-Pb3O2 (SO4) par diffraction neutronique sur poudres a 2 et 45K

Full-profile neutron powder diffraction structure refinements of dioxotrilead(II)tetraoxosulfate(VI) at 2 and 45K reveal that both the alpha- and the gamma-Pb₃O₂ (SO₄) polymorphs have to be refined simultaneously at these temperatures. Accordingly, the paraelastic alpha phase is trapped in the ferroelastic gamma phase, yielding thus mixtures of both compounds in a nearly 1:1 molar ratio. Both structures are essentially similar. The slight variations of the lead-oxygen distances in the infinite edge-sharing tetrahedral (Pb₃ O₂)n double-chains force the sulfate group to adopt nearly C3v and C2v site symmetries respectively in the alpha and gamma phases. The present work is a good example of the behaviour of the DBW3.2 program (1) when mixtures of very similar structures are refined simultaneously (high correlation between some structural parameters).     

建筑师难以出精品之原因分析

指出当今建筑业良好的市场给建筑师们提供了展示自己作品的广大空间 ,但其精品却为之甚少。为此 ,对建筑业存在的一些问题及制约建筑师出精品的主、客观因素进行了分析 ,指出建筑师应提高自身素质 ,树立精品意识 ,增强市场竞争能力     

rried out. The Lagrange multipliers are

boundary conditions. A cell structure which is independent to the nodes is used to evaluate the integrals of EFG     

GAO Feng~1,LI Wei~2,TANG Zon

tific Experiment Center of Guangxi Medical University,Nanning 530021,China)Objective:To investigate the mutation pattern of adenomatous polyposis coli(APC),Kirsten-ras(K-ras) and p53 genes in sporadic colorectal cancer tissues.Meth     

Modeling of the bulk free radical polymerization up to high conversion—three stage polymerization model. II. Number-average molecular weight and apparent initiator efficiency

The equations for predicting the number-average molecular weight are derived on the basis of the three stage polymerization model (TSPM) in this paper. By applying the equations, a plotting approach is proposed to determine the apparent initiator efficiency defined as f[(α_td+1)/2] and the constant of chain transfer to monomer, where f is the initiator efficiency and α_td denotes the fraction of the termination rate constants by disproportionation. Using the approach to plot the experimental data in the literature, it is found that the chain transfer to monomer can be neglected for both methylmethacrylate (MMA) and styrene (St) polymerizations, but it can exert a significant effect on ethylmethacrylate (EMA) polymerization. In addition, the apparent initiator efficiency is found to be independent of reaction temperature and initiator concentration at each stage. The values of f[(α_td+1)/2] at gel effect stage are slightly reduced as compared with that at low conversion stage for MMA and EMA polymerizations. However, it decreases significantly at gel effect stage for St polymerization. Using the equations derived and the apparent initiator efficiencies obtained from TSPM plots, the number-average molecular weights at different conversions can be predicted. Comparisons show that the agreement between predictions and experimental data is satisfactory.     

重型车床专用喷吸钻的设计

主要介绍了喷吸钻装置的工作原理、结构设计和使用特点,并对其运行的可靠性作简要分析.此喷吸钻的设计目的主要是为了解决大型轴类(轧辊类)工件的深孔加工问题,提高实际生产中的深孔加工效率.