人工神经网络在中浓纸浆流体化仿真研究中的应用

中浓纸浆悬浮液在剪切室内流动时,其所受剪切应力与湍流发生器的几何形状、转速及浆料浓度都有关系,通过改进算法的BP网络对实验数据的拟合,人工神经网络模拟仿真了各个因素对中浓纸浆所受剪切应力产生的影响,此外通过网络训练达到的稳定模型,可以预测中浓纸浆在更高浓度和湍流发生器转速下所受的剪切应力值.     

中浓红麻纸浆和磨木纸浆的流体化研究（广东省科委科技基金资助课题）

中浓纸浆由于浓度高，纤维交织成多孔状且可压缩的具有粘弹性的网络，故中浓纸浆要实现流体化，就必须对纤维网络施加足够大的剪切应力。本文介绍了一种经过改进的转子剪切实验装置，并对红麻纸浆和磨木纸浆分别做了流体化实验，从而对中浓纸浆流体化作了较为深入的探讨。     

中浓红麻纸浆和磨木纸浆的流体化研究

中浓纸浆由于浓度高，纤维交织成多孔状切可压缩的具有粘弹性的网络，故中浓纸浆要实现流体化，就必须对纤维网络施加足够大的剪切应力。本文介绍了一种经过改进的转子剪切实验装置，并对红麻纸浆和磨木红浆分别做了流体化实验，从而对中浓乐流体化作了较为深入的探讨。     

中浓浆泵螺旋叶片式湍流发生器的设计及其性能测试

湍流发生器是离心式中浓纸浆泵的关键部件,其作用是使纸浆实现流体化并进行气液分离。本文提出了螺旋叶片式湍流发生器的湍流临界转速的计算公式,设计了不同直径的湍流发生器并利用中浓泵测试系统进行了测试。测试结果证明,实验数据分析与公式计算结果相符。为优化湍流发生器的结构设计奠定了基础。     

基于CFD方法优化离心式中浓浆泵湍流发生器结构的研究

基于CFD方法在FLUENT 6.0软件平台上模拟了湍流发生器作用下中浓纸浆悬浮液的三维流场,并根据模拟结果对离心式中浓浆泵湍流发生器的结构进行了优化设计。实验表明,优化结构的湍流发生器在较低能量消耗的前提下对中浓纸浆悬浮液的湍流流动、气体分离都有更好的贡献。因此在工程实际中,CFD方法对缩短设计周期、降低资金消耗具有重要作用。     

用广义雷诺数判别纤维悬浮液的流动类型和湍流程度

从研究纸浆悬浮液的流动机理出发,采用广义雷诺数来判断纸浆悬浮液的湍流程度。在流动系统中测得纸浆悬浮液在低浓条件下的流态系数 n 和浓度系数 K.回归出浓度 c 与 n 和 k 的关系;根据广义雷诺数的定义,得到以浓度 c 表示的广义雷诺数表达式,以此作为判别纸浆悬浮液湍流程度的计算公式。并在雷诺实验装置中进行验证,证安了公式的准确性。     

中浓纸浆漂白过程混合技术的研究

分析了中浓纸浆漂白过程中纸浆与漂白剂的混合机理,通过中浓纸浆流体化实验,研究了中浓纸浆混合过程的网络强度、湍流粘度、单位体积能耗及混合时间等特性参数,并对中浓纸浆混合器的设计方法及提高混合效果的影响因素进行了探讨.     

中浓纸浆悬浮液塞流流动的实验研究

采用高压气送及数据采集的方法系统地研究了中浓纸浆悬浮液在圆管内寒流流动的流体动力学特征,计算了中浓纸浆悬浮液流动的相关流体动力学参数,分析了纸浆的流动特性与纸浆密度及外界作用力的内在关系,以及中浓纸浆悬浮液达到稳定塞流时的流动形态.还研究探讨了中浓纸浆悬浮液塞流流动的多孔介质现象.在工程上可为中浓纸浆与漂剂混合后寒流段各相间的物理作用提供一定的流体动力学依据,进而使各类漂剂最大程度地在纸浆中进行扩散和均匀分布.     

CMC对漂白针叶木浆悬浮液屈服应力的影响及其应用

通过向漂白针叶木浆中添加CMC来改善纸浆悬浮液的流变特性,并对纸浆悬浮液的屈服应力进行了研究。结果表明,在稳态剪切条件下,纸浆悬浮液的屈服应力τy随浆浓Cm的增大而迅速增大,两者符合指数关系τy=aCbm,且添加CMC不影响两者的指数关系;对于浓度一定的纸浆悬浮液,随CMC添加量的增加,纸浆悬浮液的屈服应力先减小后增大,当添加相对绝干浆质量约1.5%的CMC时,纸浆悬浮液的屈服应力显著减小;随浆浓的增大,CMC对其屈服应力的影响也越来越显著,向浆浓为4%的漂白针叶木浆中添加1.5% CMC时,纸浆悬浮液的屈服应力下降最多,降低了16.2%,且纸浆的搅拌能耗明显降低,降低约40.6%;此外,添加CMC会降低纸浆初始流态化时的能量耗散因子εF,使得纸浆更易于输送。实验结果可为漂白针叶木浆的输送、筛选和混合等过程的工艺节能降耗和装备技术研发与优化提供理论依据。     

纸浆纤维悬浮液流动的数值分析

本文分析了有关宾汉流体的计算及湍流两相流的现状,选择纸浆纤维悬浮液的研究模型,对其数值模拟进行了初探.通过对直圆管中纸浆纤维悬浮液两相湍流的模拟,证明了流核区的存在(r/R=0～0.2).纤维相和液相的速度分布说明滑移扩散连续介质模型的正确性,将不同初始湍流强度进行比较,可进一步解释有关"阻力减小"的现象.     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the