实现引纸技术现代化,提高纸机效率

纸机效率是一项非常重要的技术经济指标。它直接影响纸机的产量、成本和经济效益。纸机效率取决于纸机设计的先进性和完善程度、维护保养水平、纸机管理水平、人员操作水平等诸多因素。然而,引纸技术的现代化却往往不被重视,不管引纸有多么困难,只要能引上纸就认为是可行了。很少研究如何提高引纸的快捷、可靠、安全和效率,因此,当前有许多纸机由于引纸技术水平低、装备差,严重地降低了纸机效率。Voith公司经过调查研究发现,发达国家的纸机平均效率为82%,只有1%的纸机的效率能达到97%。Voith公司对纸机效率分析后认为,由于优化引纸技术,可…     

纸机引纸系统优化

通过改善和优化纸机引纸系统达到提升纸机运行效率的目的。在对现场实际情况进行充分调查之后提出合适的方案。这些方案包括:水针系统,引纸绳系统的优化和维护,真空无绳引纸系统改造。详细介绍了真空无绳引纸系统的主要部件和功能组成。     

现代高速纸机的引纸效率分析

在生产实践中,人们关注的引纸事项是:效率问题、引纸技能问题、操作人员安全问题.用于克服断头、改善引纸的少量投资在较短的时间内就能得到回报.引纸应从成形部开始,到卷取部结束.     

真空吸移引纸毛毯的选择

真空吸移引纸装置已越来越多地在长网造纸机上使用.这种引纸方式在提高纸机车速、消除纸张断头、增加纸机效率等方面取得满意的效果.     

弧形引纸辊和橄榄引纸辊

弧形引纸辊，又称弧芯软套舒展引纸辊，是装置在表面施胶机之后，将半干的纸页舒展后进入镀铬烘缸，达到最后的干燥。1弧形引纸辊弧形引纸辊（简称弧形辊），它的外面是12毫米厚夹有编织物的橡胶筒体，简体内有5°弯曲角的弧形钢制芯轴；芯轴上在辊面宽范围内配有9只滚动轴承，轴承外圈上套有4．5毫米厚且有挠性的螺旋管，螺旋管是采用无缝钢管加工的螺旋条，截面是矩形。钢管的一端与绳轮相联接，依靠引纸绳带动绳轮、螺旋管、筒体及轴承外圈一起旋转，构成一个弯曲旋转的辊筒。弧形的钢轴静止不转，弧形的朝向通过设在操作面的蜗轮副调节…     

引纸装置在高速纸机干纸页的应用

本文介绍广纸PM1纸机从干燥部到软压光引纸装置。     

涂布机引纸系统的模块化设计

涂布机引纸系统可分解成几个相对独立的元素,将这些元素进行模块化处理,并加以分析,以实现引纸系统的最优化设计,从而从根本上解决引纸系统设计过程中的繁杂和无序.     

软压光引纸系统的设计与效果

本文从引纸基本原理出发并结合设备布置情况，大胆采用简单有效的引纸方式，成功地设计了新型软压光机引纸系统，并且运行效果良好。     

浅谈上引纸复卷机的使用

在生产卷筒纸的成品设备中，复卷机是一主要设备。国内生产的上引纸复卷机在各造纸厂中应用较广。这种设备具有引纸简单、操作直观、维修方便、价格低廉等特点。但是各使用厂家的使用效果有很大差异。上引纸复卷机结构如图所示。上引纸复卷机结构图工作原理：退纸装置用磁粉制动器来保持统幅的张力。纸幅经过导纸辊、展纸装置进入纵切机构，然后卷纸。展纸装置采用弧形杠，切刀无传动，纵切底刀同时还起着压辊的作用。纸卷靠前，后托辊带动，两辊用一台滑差电机传动，并配有固定速差，前托辊速度高5％左右。复卷完成后，托辊的制动是通过安…     

涂布机引纸系统的模块化设计

合理的引纸系统,可以使整个引纸过程达到最佳状态。文章对涂布机引纸系统包括辊筒部的绳轮、张紧装置、驱动装置、绳轮架装置以及纸头传接夹口的模块化设计作了介绍。     

3800mm纸机施胶压榨引纸绳系统改造

介绍了3800mm纸机施胶压榨引纸绳系统的技术改造情况。生产实践表明，改造后引纸绳使用寿命大大提高，从而为纸机正常生产，提高产量和经济效益创造了有利条件。     

脱氮硫杆菌硫转移酶SoxAX的建模及分子对接

硫氧化酶系统(Sulfur oxidizing,Sox)在脱氮硫杆菌(Thiobacillus denitrificans,Td)的硫代谢过程中起着至关重要的作用,其核心为Sox AXYZB,硫化物需先经Sox AX蛋白催化并转移到Sox YZ上才能进行Sox通路后续的硫氧化反应,而目前尚无脱氮硫杆菌Sox AX蛋白结构解析的报道。本文采用反向折叠法构建了Sox AX蛋白的二聚体结构并验证其合理性,并通过分子对接实验探讨Sox AX蛋白模型与硫代硫酸盐、硫化氢和亚硫酸盐等不同底物结合在构型与能量上的差异。结果表明,构建的Sox AX二聚体蛋白结构相对合理,氢键是维持Sox AX二聚体结合的主要作用力,10个短强氢键和1个π键作用力参与维持二聚体结构的稳定,Sox A的Arg160等6个残基及Sox X的Asn15等8个残基对维持二聚体结构有重要作用。分子对接试验显示氢键是维持底物与Sox AX结合的主要作用力,与底物结合的关键氨基酸为Arg210、Cys214和Gln217。在三种底物与酶结合的亲和力中以硫化氢最高、硫代硫酸盐次之、亚硫酸盐最低。     

新型高速弹力丝机

对高速弹力丝机的最新技术进行了分析,对新技术、新结构的特点进行了总结。其技术发展理念适应当今节能降耗的趋势,具有很大潜力。     

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.     

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.