基于改进PSO算法的PID优化用于黑液液位控制

制浆过程中碱回收蒸发工段黑液液位控制直接影响着黑液浓度和蒸发效率。针对黑液液位非线性、大时滞及时变性的特点,传统PID方法控制精度较低,使用标准粒子群算法可以优化PID参数,提高精度,但是收敛速度慢,整定时间长。针对这些问题,采用改进的粒子群算法来整定PID参数,通过动态调整惯性因子和加速因子,以及改进收敛准则等方法来提高粒子群算法的全局寻优能力和收敛速度,并在MATLAB/SIMULINK仿真实验平台上,比较了传统PID方法、标准PSO算法和改进PSO算法对黑液液位的控制效果,结果表明改进PSO算法优化的PID控制缩短了调节时间,降低了超调量,说明改进粒子群算法优化后的黑液液位PID控制具有更快的响应速度和更好的鲁棒性,有效地提高了控制质量。     

基于自适应变异差分进化算法的溶解氧浓度控制系统

溶解氧是造纸中段废水好氧处理过程中的重要参量,但溶解氧过程控制回路存在大时滞、非线性等问题,常规PID控制难以收到理想效果。本课题在分析差分进化算法的基础上,提出了一种自适应变异差分进化算法,用于PID控制器的参数优化,实现对溶解氧浓度的精准控制。MATLAB仿真结果表明,与常规PID控制和基于传统差分进化算法的PID控制相比,本算法具有响应速度快、超调量小的优点,能够收到良好的控制效果。本算法已经投入实际应用,COD_(Cr)去除率达到84.5%,BOD去除率达到93.4%,水处理系统运行良好,能够实现废水达标排放。     

基于H∞最优控制理论的粒子群优化算法在造纸定量控制中的应用

针对造纸定量控制系统具有非线性、时滞、多干扰等控制难点,本课题提出一种基于H_∞最优控制理论的粒子群优化算法(PSO)优化PID参数。改进的PSO具有对控制系统过程模型的依赖性小、参数整定简单、鲁棒性和抗干扰性强的特点。与传统算法相比,基于H_∞最优控制理论的PSO可以高效地找出符合设计要求的PID调节参数,不会陷入局部最优,且使系统性能指标达到最优或次最优。并且,仿真结果也验证了该算法的有效性和实用性。     

基于PSO的BP-PID碾米机组控制系统优化

针对当前碾米机组之间流量稳定性差,单机效率低、碾白不均衡或过碾致碎米增加等问题,提出了基于粒子群算法(PSO)优化BP-PID控制的碾米机组控制系统;运用多机协同优化技术,通过调控在线碾米单机的碾除糠粉比例及其匹配的运行参数实现流量平衡控制;通过BP神经网络训练PID控制器的参数建立碾米机组调控数学模型,并引入PSO对BP神经网络的性能进行优化。仿真试验表明,经PSO优化的控制系统的响应速度更快,其稳态精度有所提高,且具有良好的控制效果。     

基于粒子群算法优化PIDNN的流浆箱解耦控制

针对气垫式流浆箱的总压和浆位之间存在严重耦合的情况,探讨使用粒子群算法优化的PID神经元网络对其进行解耦控制。建立一个双输入双输出PID神经元网络控制系统,用粒子群算法优化网络的初始权重后,再采用误差反向传播算法进行修正,最终实现完全解耦。仿真结果表明,经粒子群算法优化后的神经元网络能够有效地消除总压与浆位之间的耦合,大大缩短调试时间,具有更高的控制精度,能够用于气垫式流浆箱的控制。     

基于PSO算法的PID控制器参数优化及其在置换蒸煮立锅温差控制中的应用

在介绍置换蒸煮工艺流程的基础上,对置换蒸煮控制系统的控制要点和难点进行了分析。针对蒸煮过程中蒸煮立锅顶部药液温度和底部药液温度的差值的控制问题,设计了一种基于PSO(粒子群优化)算法优化PID控制器参数的温度-流量串级控制策略。MATLAB/Simulink仿真结果表明,该控制方案具有算法简单、搜索能力快、效率高等优点,能够有效地解决PID参数优化问题;实际应用结果表明,该方案非常有效。     

基于PSO优化PID的造纸定量控制系统设计

纸张定量控制在造纸工艺中至关重要,不仅关系到纸张的生产效率和质量,还关系到纸张制造企业的成本问题。为此,设计一种基于PSO优化PID的造纸定量控制系统。该系统通过粒子群算法优化PID控制器的三个控制参数,让PID控制效果达到最佳,然后将传感器采集到的纸浆浓度、流量与设定值相比较,最后利用优化后的PID控制器根据偏差值控制浆泵转速和稀释水阀出水流量,从而使造纸定量达到最优。结果表明:与传统PID的造纸定量控制系统相比,所设计系统应用下,造纸定量在46～50 g/m~2之间波动,满足了设置的控制精度目标,即生产工艺±5 g/m~2偏差规定要求,证明了系统的控制性能。     

改进遗传算法PID参数优化在吹贯蒸汽流速控制中的应用

纸机干燥部吹贯蒸汽流速控制是解决烘缸积水问题的一项重要措施。吹贯蒸汽流速控制通常采用PID控制器,而传统的PID控制方法的控制精度较低、参数整定耗时较长,难以达到理想的控制效果。本课题在对基本遗传算法进行分析的基础上,提出了一种改进的遗传算法,并将该算法用于PID控制器参数优化,实现对纸机干燥部吹贯蒸汽流速的精确控制。MATLAB仿真实验结果表明,与常规PID控制器和基于基本遗传算法的PID控制器相比,基于改进遗传算法的PID控制系统具有响应速度快、超调量小、鲁棒性强的优点,能够获得理想的控制效果。文中所述算法已投入实际应用,明显提高了二次蒸汽的利用效率,能够获得可观的经济效益。     

基于改进粒子群优化IPSO算法的茶叶烘干机温度控制策略

针对茶叶烘干机热效率低,温度不稳定、茶叶品质不易保证的问题,对燃煤式热风干炉进行研究,通过对粒子群算法(PSO)进行混沌处理,得出了一种改进粒子群算法(IPSO),然后通过IPSO对模糊PID控制器的参数进行优化,以解决粒子群算法易早熟、寻优效率低以及PID参数无法实时在线调整的缺点。根据热风炉的实时温度,自动调节热风炉的排烟量,以实现烘干机的温度恒定。同时,采用优化后的模糊PID控制策略对系统进行了仿真和测试。结果表明,该研究所用方法能根据烘干机温度有效控制热风炉排烟量,从而实时控制热风温度,实现恒温控制的目的。     

基于改进粒子群优化的主动磁悬浮轴承模糊PID控制

针对主动悬浮轴承(Active Magnent Bearing,AMB)系统控制参数多、结构复杂等因素,采用模糊PID控制算法并结合改进的粒子群优化算法对其进行控制。通过提出合适的目标函数克服对系统先验知识掌握的不足,采用粒子群优化算法对模糊PID控制器的参数进行调节。仿真结果表明,通过与模糊PID控制的系统相比,采用粒子群优化的模糊PID的控制器性能更优良。     

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.     

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.     

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.     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.