双面胶印机离合压机构设计

离合压机构直接影响到印刷机工作的稳定性.从双面胶印机的特点出发,设计出一种由上下橡皮滚筒完成动作的离合压机构.通过选择三次多项式的运动规律,分析离合压机构运动过程的时序,求出了离合压凸轮的轮廓曲线.该设计方法同样适用于印刷机其它机构的设计.     

基于UG软件的旋转式递纸机构运动分析

旋转式递纸机构是胶印机中的关键机构,它主要由凸轮机构和四杆机构组成,是一个组合机构.文章根据测绘得到的凸轮轮廓离散坐标及四杆长度,通过传统凸轮轮廓的光顺处理以及曲线拟合与UG软件分析的结果进行比较,获得了凸轮机构的输出运动规律.根据运动分析结果,提出了一种基于UG软件对递纸机构设计的新方法.     

基于UG的通用凸轮曲线三次开发技术

凸轮曲线是凸轮驱动从动件的运动曲线,它影响到凸轮机构的效率、精度以及寿命,故在凸轮设计中十分重要.为快速有效地进行凸轮机构设计,总结推导了通用凸轮曲线公式,综合应用Visual C++6.0、UG/OPEN MenuScript、UG/OPEN UIStyler和UG/OPEN API等开发工具,开发了基于UG软件的通...     

基于虚拟样机技术的印刷机离合压机构研究

为了提高产品设计质量,降低成本,缩短研发周期,在印刷机设计过程中采用了虚拟样机技术对三点支撑式离合压机构进行了研究。通过建立三维数字化建模、机构装拆仿真、调整模拟、运动仿真,对机构的物理、力学性能进行分析、模拟、预测,对关键零件进行受力分析并给出了应力-应变图,对关键机构的关键运动点给出了位移、速度、加速度曲线,实现了设计方案的快速实施。结果表明:在由凸轮驱动的离合压机构中,随着印刷速度的增大,离合压机构在工作过程中易产生冲击与振动。因此,提高凸轮的加工精度,可减少印刷过程中产生的振动与冲击,提高印刷质量。     

汽车空调箱风门驱动机构的设计研究

运用机械机构设计原理和CATIA软件的运动学模块,创建汽车空调箱风门驱动机构的运动仿真。使用CATIA的law特性驱动风门和凸轮,生成曲柄销轴在凸轮上的运动轨迹的方法来设计凸轮。对其轨迹进行压力角的分析与调整,减小压力角来减小机构的扭矩。对机构零件的配合间隙和材料特性的选用,来减小机构的噪音。通过凸轮槽的设计以及机构零件的配合间隙和材料的选用,为运动机构设计及改进提供理论依据和设计经验。     

经编机成圈机构的运动学分析

采用UG软件建立高速经编机传动及成圈机构的CAD模型,通过UG/Motion模块对其进行运动学仿真,并分别分析了槽针、针芯、梳栉这3个主要成圈部件的相对运动关系,得出了能够正确实现成圈运动的配合关系曲线。在此基础上,指出了梳栉最佳横移时间以及成圈机构的运动特性对经编机运行的影响。     

基于PLC的胶印机离合压机构控制系统设计

为了精确稳定地控制胶印机的离合压机构,在分析顺序离合压工作条件和要求的基础上,设计了针对并联气缸驱动离合压机构的气动控制回路;依据系统控制要求,进行了以PLC为控制器的系统硬件选型和软件设计,实现了离合压的自动控制,并通过仿真软件对系统进行验证。结果表明,系统符合印刷工艺过程的要求。     

虚拟样机技术在织机打纬机构分析中的应用

共轭凸轮打纬机构是控制织机的关键部件,是决定织机运动速度和平稳的关键因素之一。利用ADAMS软件建立了共轭凸轮打纬机构的虚拟样机,分别对共轭凸轮打纬机构进行了运动学、动力学仿真分析,该分析方法有助于稳定和提高打纬质量。     

新型粉末包装机往复式横封机构设计

传统的往复式横封机构有凸轮式和气缸式。针对凸轮式横封机构凸轮轮廓不合理容易引起震动和噪声,气缸式横封机构速度改变时存在较大冲击以及气缸密封性等问题,课题组提出了一种新型粉末包装机往复式横封机构。课题组采用解析法与三维软件相结合的方法对该机构进行研究,建立了粉末包装机往复式横封机构的数学模型,对横封机构的执行末端横封头进行了受力分析和运动学分析。通过SolidWorks软件进行三维建模,并运用SolidWorks Motion对横封机构的横封头进行了运动学模拟仿真。结果表明该横封机构具有平稳、噪声小等优点,可方便地进行调速,适应多种包装袋长的横封要求。     

曲柄滑块机构滑块匀速运动研究

在普通滑块机构中增加一个带凸轮槽的可改变曲柄长度的装置,从而实现了滑块在工作行程中的匀速运动。使用复数矢量法和动态静力学理论对该机构进行了运动学和动力学解析。采用SolidWorks软件的Motion模块对变长度曲柄滑块机构进行建模仿真和运动分析,获得机构的运动特性曲线和动力学特性曲线。结果表明,变长度曲柄滑块机构中滑块实现匀速运动是可行的。     

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.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

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.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.