蜂窝纸板防振性能实验分析

针对不同厚度的蜂窝纸板在正弦变频振动测试中的加速度传递,绘制其不同衰减系数的振动传递率曲线,为蜂窝纸板在防振包装设计中的应用提供了参考数据。     

采用恢复力-状态映射法对蜂窝纸板动态特性建模

随着蜂窝纸板在缓冲包装中的逐渐广泛应用,蜂窝纸板的特性研究越来越受到重视。本文采用蜂窝纸板—质量系统模拟包装系统,将恢复力-状态映射法应用到蜂窝纸板的特性研究问题中。构造出实验系统,采用随机振动实验记录任一瞬时系统的加速度、速度和位移,构造出蜂窝纸板的恢复力-状态映射图,根据该映射图得出厚度为30～60mm的蜂窝纸板的弹性力及阻尼力,由实验结果可看出,蜂窝纸板的弹性力是位移的非线性函数,而阻尼力与速度成正比,并采用最小二乘法识别出不同厚度的蜂窝纸板的线性及非线性弹性系数、阻尼系数。利用该模型模拟出蜂窝纸板—质量系统的振动传递率曲线,并与实验结果进行对比。结构表明,该模型可准确预测蜂窝纸板—质量系统的共振频率,但对于共振峰值的预测具有一定的误差,本文对可能造成误差的因素进行了分析。     

准静态压缩下蜂窝纸板应力-应变模型

本文对蜂窝纸板进行准静态压缩实验,获得力一位移数据,借助Maflab软件,对其进行处理.通过Gauss拟合函数,获得精度较高的蜂窝纸板应力-应变模型,比较了纸板厚度、材质对平压强度的影响;通过蜂窝纸板静态缓冲系数-应力曲线,分析比较了厚度、面纸和芯纸的定量对其缓冲性能的影响.结果表明,纸板厚度对蜂窝纸板的平压强度和缓冲性能影响较小,而面纸和芯纸的定量对其影响较大.     

双芯蜂窝纸板的平压性能及加工工艺研究

为解决蜂窝纸板抗压强度提高与成本增加之间的矛盾,提出了双芯蜂窝纸板的设计方案,在现有单芯蜂窝纸板加工工艺的基础上,确定了双芯蜂窝纸板的加工工艺,应用河北省唐山市唐海圆鸣蜂窝纸板生产有限公司的设备制作了110g/m~2与220g/m~2两种纸芯组成的20mm厚的双芯蜂窝纸板样本,并对20mm厚的110g/m~2单芯蜂窝纸板及110g/m~2与220g/m~2双芯蜂窝纸板的平压性能进行了实验,同时采用了有限元方法对两种蜂窝纸板的性能进行了仿真分析,通过实验数据及仿真分析数据的双重验证可以看出双芯蜂窝纸板的平压性能有了大幅提高。通过成本分析,提出的新型双芯蜂窝纸板的成本增加较少,是一种高性价比的材料。     

基于横向振动频率的轴向运动纱线张力测量

为高效、便捷地检测纱线张力,构建了一种基于横向振动频率的非接触检测纱线张力方法。利用弦振动原理推导出纱线横向振动方程,根据纱线振动方程计算纱线振动频率。以轴向运动纱线的张力、速度和频率的拟合公式,通过测量纱线的振动频率可方便快捷地计算出纱线张力。将计算结果经过广义回归神经网络(GRNN)模型进行拟合,进一步提高测量结果的准确性。采用高速相机测量纱线的横向振动位移,并检测纱线的振动频率。利用频率法对32 tex纱线在设定张力分别为40和60 cN,速度分别为6和2 m/s时的张力进行测量。结果表明,利用振动频率测量纱线张力的数据经GRNN拟合,其曲线整体趋势与张力传感器测量的张力趋势相同且更加平滑,便于对生产过程中张力的控制,该方法具有有效性和准确性。     

SVM回归法在佛手精油β-环糊精包合工艺优化中的应用

采用了基于统计学习理论的支持向量机(SVM)回归方法对佛手精油β-环糊精包含物制备的工艺条件进行了预测及优化。通过正交试验为构建SVM回归模型提供了基础数据,并运用交叉验证对模型参数进行了优化。回归结果显示,回收率SVM模型(MSE=0.003,R2=0.958 1)和包埋率SVM模型(MSE=0.007,R2=0.900 8)得到的回归预测值和试验测定值拟合良好,两者相对误差小于0.1%的回归值比例分别为100%和88.0%,表明SVM回归法可精确地预测挥发油β-环糊精包含物制备工艺状况,从而获取更为可靠的最优化工艺条件。     

夹层结构纸板压缩剪切性能试验研究

采用改进的组合式压缩剪切夹具,测试不同厚度的蜂窝纸板和高强瓦楞复合纸板横、纵向的剪切载荷一位移数据并绘制了相应曲线以及对应的抗剪切强度柱状图。测试结果表明：对于夹层结构纸板纵向样品的抗剪切能力大于横向样品;在用纸定量和质量相同时,相同方向的蜂窝和高强瓦楞复合纸板的抗剪切能力随厚度的增加而降低,相同厚度和方向蜂窝纸板的抗剪切能力大于高强瓦楞复合纸板,蜂窝纸板的抗剪切性能比高强瓦楞复合纸板更好。研究结果对于夹层结构纸板的进一步应用提供了压缩剪切方面的依据。     

基于相对湿度影响的蜂窝纸板平台应力表征

研究相对湿度对蜂窝纸板平台应力的影响,测试4个典型湿度条件下蜂窝原纸的纵向屈服强度,引入六边形金属蜂窝平台应力理论并进行修正,建立了基于相对湿度影响的蜂窝纸板平台应力模型,并与实验实测数据进行比较验证.结果表明,建立的模型能较准确地反映环境相对湿度对蜂窝纸板平台应力的影响.     

多层托盘货物单元的振动传递性能研究

文章介绍了托盘集装单元的动力学模型,通过扫频振动实验和定频振动实验确定了各层货箱的固有频率,探讨了其固有频率和振动传递率与堆码高度之间的关系。结果表明,在一定振动频率范围内,对于多层堆码的高粘弹性货箱,底层货箱的固有频率高于顶层货箱的,振动传递率峰值所在频率取决于货箱堆码高度。     

清香型原酒中乙酸乙酯和乳酸乙酯的快速分析研究

研究利用近红外技术建立清香型原酒乙酸乙酯和乳酸乙酯的快速检测方法.通过光谱预处理和波数范围的选择与优化,最终得到R2线性关系良好,交叉验证均方根RMSECV较小的最优模型.在对模型进行验证实验中,其近红外预测值与化学实测值之间的R2分别为0.9572和0.9648,预测误差分别为1.37％和1.25％.结果 表明,所得...     

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