周期logistic脉冲收获系统的优化控制策略

研究一类由周期logistic模型描述的种群系统的脉冲优化控制问题．在给定时刻对种群同时进行比例和常量脉冲收获,在系统保持周期变化的前提下,考虑收获成本因素,以最大经济净收益为目标,研究收获努力量及收获常数对收益的影响,并确定最优的脉冲收获控制策略．利用关于脉冲微分系统的极值原理和一些分析技巧,获得了最优控制策略及最优收益的确切表达式．     

周期脉冲L-V竞争系统解的全局渐近性质

研究一类具有脉冲效应的Lotka-Volterra周期竞争系统.利用脉冲微分系统的比较原理,Floquet理论及一些分析技巧研究了系统解的有界性及渐近性质,并建立了系统正周期解存在惟一及全局吸引的条件.最后用实例进行数值模拟,解释说明了所获得的主要结论.     

The global asymptotic properties of the solutions of periodic imulsive L-V competition system

研究一类具有脉冲效应的Lotka-Volterra周期竞争系统.利用脉冲微分系统的比较原理,Floquet理论及一些分析技巧研究了系统解的有界性及渐近性质,并建立了系统正周期解存在惟一及全局吸引的条件.最后用实例进行数值模拟,解释说明了所获得的主要结论.     

一类具有分布时滞的脉冲Logistic系统的周期正解

利用Gaines和Mawhin的重合度理论,研究了一类具有分布时滞的脉冲Logstic系统,获得了该系统至少存在一个周期正解的充分条件.     

具有脉冲的生态传染病模型周期解的存在性(英文)

研究了一个具有脉冲周期的传染病模型.利用Floquet理论给出了平凡周期解、半平凡周期解及无病周期解线性稳定的条件.利用重合度理论,得到了正周期解的存在性.给出了系统持久的充分条件.数值模拟验证了理论结果的正确性.     

具有时滞与饱和发生率的脉冲接种模型的研究

研究了一类具有时滞与饱和发生率的SIR脉冲接种模型,利用频闪映射得到了模型的无病周期解,进而利用比较原理给出了无病周期解全局稳定的条件及疾病控制的最大接种周期τmax,当接种周期τ<τmax时,理论上疾病可以被根除.该脉冲接种模型相比较传统的接种模型,所需成本更低,且更加有效.     

具有Holling Ⅲ类功能反应捕食系统收获模型的持久性

研究了一类具有双线性密度制约Holling Ⅲ类功能反应的非自治捕食收获系统模型.利用比较原理,得到系统一致持久的充分条件.通过构建Liapunov函数,运用Barbalart引理,得到了对应周期系统存在惟一全局渐近稳定正周期解的充分条件.     

条斑紫菜蛋白和多糖的逆流脉冲超声辅助提取技术研究

为了缩短生产周期和提高产品产量,本文采用逆流脉冲超声技术对条斑紫菜中蛋白和多糖进行提取。采用Box-Behnken中心组合设计方法结合响应面分析对脉冲超声辅助提取条件进行优化。研究得到了提取的回归方程,通过回归分析与实验验证。在提取液pH9.0、脉冲超声的工作时间4s和间歇时间2s的条件下,获得紫菜蛋白和多糖逆流脉冲超声辅助提取的最佳工艺条件为:提取时间85min、料液温度40℃、料液比19:1(mg/mL),在此最佳条件下,紫菜蛋白和多糖总得率高达37.26%,其中紫菜蛋白和多糖的得率分别为15.68%和21.58%。通过与传统的浸提法对照实验,发现利用逆流脉冲超声辅助提取紫菜中蛋白和多糖的总得率提高了116.38%,提高幅度显著。     

电解法制备超细铜粉的工艺研究

采用脉冲电解法,在硫酸铜与硫酸混合电解溶液体系中,就不同脉冲电解参数对阴极铜粉形貌和粒度的影响进行了研究.实验获得合适的脉冲参数为平均电流密度i=600 A/m2,脉冲宽度ton=8ms,占空比为1∶3,在此条件下,所得铜粉平均粒度为0.87μm,有90%颗粒粒径小于1.25μm,阴极沉积出的铜粉颗粒粒度在0.24~1.79μm之间,粒度分布均匀.     

线性包装系统关键部件三维冲击谱研究

本文研究线性包装系统关键部件在半正弦脉冲激励下的冲击特性.通过建立二自由度线性包装系统模型,得到冲击动力学方程并数值求解.依据结果得到关键部件三维冲击谱,并进一步讨论了频率比、脉冲激励幅值和系统参数对关键部件冲击谱的影响规律.结果表明,频率比、脉冲激励幅值和系统参数对关键部件冲击响应峰值影响显著.研究结论为产品包装设计提供了科学依据.     

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