复卷机负荷分配控制策略的分析与实现

针对复卷机在复卷过程中前后底辊电机转矩控制的工艺要求,分析了负荷分配产生的原因及控制原理,提出了一种基于矢量变频器的主从控制方式,该方法不仅能使前后底辊电机保持同步,保持复卷中的张力恒定,而且使后底辊电机很好地跟随前底辊电机转矩的变化,达到负荷分配控制的目的.     

造纸机负荷分配系统分析

岳阳造纸厂1号纸机，幅宽4m，速度600m／min。传动系统是德国AEG公司提供的MIDISEMI可控硅直流系统。纸机在网部、压榨部、1组供缸采用了多电机传动，应用了负荷分配自动控制电路。本文将对压榨部负荷控制的线路、原理、稳定性进行分析。1压榨部的多点传动及负荷分配原因压榨部由5台电机传动，其中一压电机是主导电机。真空引纸辊、一压、二压共带一床毛毯，三压带一床毛毯。一压沟纹辊与真空辊摩擦带另一床毛毯。二压、三压靠与石辊的相互摩擦传递力矩。见图1。要求二压、三压速度必须严格协调。我们先分析它们的负荷分配方式。直流电…     

基于卡尔曼滤波器的切纸机控制系统设计

针对切纸机的纸幅精度问题,采用变频控制与伺服控制相结合的方案,设计了以STM32单片机为核心的切纸机混合电气控制系统.采用M/T法测速和卡尔曼滤波结合的方法得到送纸辊的速度,从而降低送纸辊速度的采集误差.实验证明在高速下,该方法可以实时得到送纸辊及切纸机电机转速.由误差分析可得,切纸精度达±1mm,证明了本控制系统的可...     

复卷机退纸辊电机的选型依据及选型优化方案

针对目前国内复卷机退纸辊电机配置普遍偏高的问题,介绍了退纸辊电机在调速范围、额定功率、额定转矩和断纸停机时间等方面的选型依据。并以山东某纸厂复卷机为例,采用恒转矩调速与恒功率调速相结合的调速方式,给出了退纸辊电机选型所需参数的计算方法,提出了降低退纸辊电机配置的2种选型优化方案。     

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。     

ACS800在2600/350多缸纸机负荷分配中的应用与研究

介绍了纸机中负荷分配的原理以及设计方法,讨论了设计负荷分配时可能遇到的问题和解决方法,提出了在纸机传动控制系统中负荷分配设计的重要性。介绍了ACS800系列直接转矩控制变频器在2600/350多缸纸机负荷分配方面的重要应用,讨论了通信、连锁、参数设置及实际使用中的一些注意事项。     

纸机负荷分配的耦合特性分析与仿真研究

根据纸机传动系统中存在的负荷分配易失衡等特点,分析了单分部间多电机拖动同一负载时传动点间耦合关系的特性,基于交流异步电机空间矢量控制的数学模型,提出了刚性耦合负荷分配采用总线通信转矩控制,以及柔性耦合负荷分配采用总线通信转速控制的控制策略;再利用MATLAB/SIMULINK软件对这两种控制策略进行建模与仿真,最终验证了两种控制策略的可行性与实用性。     

高精度切纸机控制系统设计

根据现代高速双刀切纸机的工艺要求,针对切纸机切割精度的问题,采用变频控制与伺服控制相结合的方案,设计了以STM32为核心的切纸机控制系统,以降低生产成本,提高切纸精度。介绍了切纸机的工艺流程和控制方案,以及切纸机控制系统的组成。分析了切纸辊和送纸辊编码器脉冲的采集与处理,送纸辊电机速度的给定以及通过T法对送纸辊电机实时速度的采集。说明了利用增量式PID和实际的各个参数对切纸辊变频器模拟量的给定。对采集的送纸辊速度和实际切长进行了误差分析。通过现场调试切纸精度满足工业要求,证明了本切纸机控制系统的可行性。     

复卷机前后底辊负荷分配控制方法的改进

阐述了复卷机前后底辊的负载特性及在保证底辊和纸卷接触点压区压力恒定的情况下前后底辊的转矩分配控制策略.对以往电气传动系统中前后底辊负荷分配控制方法进行了改进,实际应用中卷取效果较好.     

纸机多点传动的负荷分配器

南平造纸厂新投产的两台3150纸机的网部与压榨部采用多点同步传动的方式驱动,但是在设计时没有考虑多点同步传动各电机之间的负荷分配问题,因此,在生产时只要工艺条件稍有变化,多点传动中的两台电机的负荷就失去平衡。一台电机的电流剧增甚至过电流跳闸,而另一台电机的负荷降低直至作发电机运行。特别是4纸机的传递压榨辊与真空压榨辊的两台电机,由于机械     

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.     

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     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press