复卷机张力控制系统的设计及应用

针对复卷机退纸辊退卷张力控制系统中存在多扰动与非线性的问题,以退纸辊退卷张力为研究对象,提出一套完整的控制方案,在张力控制中引入了模糊PID算法,并加以应用。为解决交流传动下系统产生的回馈能量处理问题,对系统主电路硬件结构进行了公共直流母线设计,该设计已应用于浙江金华某纸厂复卷机项目的退纸辊退卷张力控制系统,取得了良好的控制效果。     

变张力单点控制复卷机

本文对影响复卷机纸卷质量的诸因素进行了分析,认为下引纸四点控制式复卷机造价高,中小纸厂难以接受;退纸张力对纸卷紧度的影响大于压区压力的影响;并指出了ZWJ型上引纸复卷机双支承辊差速传动的不合理性;提出了变张力单点控制的理论并设计了一套控制系统用于纸厂,取得了较好的效果。     

复卷机退卷张力自动控制系统设计

针对复卷机工作时退卷张力控制难的问题,在分析了退卷张力对纸幅质量影响的基础上,确定了退纸辊的控制要求并对控制方案进行合理选择,完成了复卷机退卷张力自动控制系统的硬件和软件设计。将公共直流母线结构应用于复卷机传动控制系统中,能充分利用再生能量,提高复卷机运行效率;对退纸辊控制部分进行软件模块化编程,使其具有普适性。该退卷张力自动控制系统在实际中的运用效果较好,适当改动即可适用于多种复卷场合下退卷张力的控制。     

额定速度下复卷机复合张力计算机辅助控制系统

考虑到传统系统在控制复卷机复合张力时存在超调量高、上升时间长、稳态误差大的问题,提出了额定速度下复卷机复合张力计算机辅助控制系统设计与实现。根据复卷机复合张力计算机辅助控制系统总体架构,设计了复卷机复合张力控制变频器和复卷机复合张力计算机辅助控制器,完成了系统的硬件设计;系统的软件设计中,在额定速度下,分析了复卷机退纸辊的动态补偿情况,结合复卷机复合张力计算机辅助控制程序的设计,实现了复卷机复合张力的计算机辅助控制。测试结果表明,文中控制系统在控制复卷机复合张力时,可以降低超调量、缩短上升时间并减小稳态误差,具有更好的控制性能。     

交流复卷机退纸辊的控制策略

针对交流复卷机退纸辊传动的控制难点,分析了退纸辊电机的选型依据,提出了退纸辊正常运行时发电回馈的能量流向,建立了复卷机退卷纸幅张力控制的两种数学模型,并提出了两种退卷张力控制的方案。     

高速下引纸复卷机的张力控制策略

比较了高速下引纸复卷机中几种常用张力控制方式的优劣,并且将触摸屏和可编程序控制器(PLC)引入复卷机张力控制系统,提高了高速运转下连续恒张力控制的稳定性,实现了对不同纸张所需张力的大小的随意设定。     

复卷机退纸辊转动惯量补偿问题的分析

复卷机退纸辊转动惯量的补偿可以保证张力恒定,从而保证了复卷的质量.分析了稳态和变速过程中造成张力波动的主要因素以及如何实时补偿转动惯量以保证恒张力控制,并提出了实际中基于欧陆590控制器的转动惯量补偿系统.     

复卷机传动控制系统的应用

福建越秀邵武制浆造纸有限公司于１９９２年从加拿大引进GL＆V公司的复卷机，其车速为１５４０m／min，用于配套西安－维美德生产的２６４０纸机，但由于原控制系统存在的问题制约了生产，公司于２００１年初与厦门青润技术发展有限公司合作，采用SIEMENS公司最新的传动控制技术，重新设计了复卷机的传动控制系统及其辅助控制系统。本文主要介绍此控制系统的构成、原理及各部分功能。１工艺流程及要求１．１工艺流程纸幅从退纸辊引出（可使用上引纸和下引纸两种方式），经导纸辊通过纵切机构，从前后底辊之间由底部绕上，而后卷在纸芯上…     

交流复卷机的间接张力控制

针对交流传动复卷机中影响间接张力控制的各因素进行了具体分析,给出了退纸辊交流电机在复卷机稳态运行和加减速运行时电磁转矩计算公式,利用现场总线技术控制退纸辊电机的变频器按照规定转矩运行就可以实现间接张力的控制。实际使用证明这种间接张力控制的方法可以接近直接张力控制的效果。     

复卷机退纸系统联轴器的改进

我公司1760mm ZWJ16复卷机为下引纸式复卷机,其退纸系统由退纸架、刚性联轴器、磁粉制动器组成。工作时,纸卷吊到退纸架上,用刚性联轴器将磁粉制动器与卷纸辊连接起来,通过控制磁粉制动器,从而控制纸幅的张力。     

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.     

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