变速箱齿轮拍击柔体动力学分析与优化

为探究变速箱内齿轮在空载时的拍击历程,从而降低齿轮的拍击噪声,优化整车的NVH。根据实际工况,在ADAMS软件中,建立变速箱齿轮的柔体动力学拍击模型,完成了发动机扭振与负载的模拟,通过对模型进行仿真,分析主从动齿轮在稳态时的角速度以及啮合力关系。分析了齿轮在受到发动机扭振激励下的拍击过程。通过频域分析可知,齿轮产生拍击是由于发动机的扭振频率及其倍频所产生。对齿轮的转动惯量进行优化,同时优化齿轮的角加速度激励,降低了齿轮的拍击力,减小了拍击噪声。     

角向磨光机异常噪声的测试分析

以频谱分析为手段,对某型号角向磨光机异常噪声样品进行测试分析,确定了齿轮副啮合噪声为主要噪声源,探讨产生机理;分析得知由于激振力频率与齿轮箱某阶固有频率耦合共振而放大了振动和噪声水平,进而提出了改善的建议。     

基于ANSYS的弹性支承的悬臂转盘-轴承系统模态分析

针对悬臂转盘系统在高速旋转时的振动、不稳定等现象,建立弹性支承悬臂转盘-轴承系统动力学模型并计算理论临界转速,应用ANSYS有限元软件对带有预应力的转盘-轴承系统进行了模态分析,分析转盘系统额定转速、轴承支承刚度、轴承间跨度和转盘厚度对转盘-轴承系统固有频率的影响,得到了各阶固有频率和固有振型。结果显示:额定转速和轴承支承刚度是影响转盘-轴承系统模态参数的主要因素,在相同工况条件下,同阶固有频率与额定转速成一元三次方程变化。同时转盘系统固有频率都随着额定转速和轴承支承刚度的增大而增大。     

结合Solidworks和ANSYS的斜齿圆柱齿轮模态分析

通过利用三维建模软件Solidworks对齿轮进行精确建模,然后将实体模型导入ANSYS有限元分析软件,并通过选择单元类型、定义材料模型、划分网格等一系列操作建立机构的有限元模型。介绍了基于ANSYS的模态分析理论,通过加载条件,求解出固有频率,通过扩展模态,从而获得齿轮机构的5阶模态参数。通过这样的分析研究,能够大大减少发生共振的可能,并且对于齿轮的优化设计和故障诊断提供了参考依据。     

行星齿轮减速器内齿圈模态分析

采用循环对称模型及全六面体网格对行星齿轮内齿圈的结构进行有预应力的模态分析,运用多点约束技术(MPC)模拟螺栓约束,使模型在尽可能小的计算规模下获得尽可能精确的计算结果,并通过试验对计算结果加以验证,计算得到内齿圈的前四阶模态.结果表明:啮合预紧力对内齿圈的固有频率和模态影响不大;而较长齿面会导致齿圈部分振动较大.     

供水管道系统噪声控制的研究

针对供水管道系统的噪声问题，建立模拟供水泵房管道系统的实验模型，对管系的噪声、振动信号进行采集和处理，运用功率谱和声振相干方法分析了管道振动的原因；采用工作模态分析方法对实验管道结构进行了模态分析，得到了管系的固有频率和振型等参数；利用谐响应分析技术得到了管系在激振下的响应情况；提出相应改造措施，取得了良好的减振降噪效果。结合理论和实验结果，系统地总结了管道系统减振降噪的控制措施，提出设计管系应遵循的原则。     

不完全齿轮盘的有限元自由模态分析

不完全齿轮盘是海带打结机构的主要驱动部件,其振动频率和振型对海带打结机构的平稳运行具有重要意义。文章利用ANSYS建立不完全齿轮盘的有限元仿真模型,并进行自由模态分析,得出不完全齿轮盘前八阶的固有频率和振型。仿真结果表明,齿轮盘的各阶固有频率和振型避开了共振区间,验证了设计方案的合理性。     

基于ANSYS Workbench的木工四头高速电主轴模态分析

高速电主轴的固有频率与相应的模态结构形状是其结构设计时的重要参数,而模态分析可用于计算结构的固有频率和模态结构形状。本文基于有限元分析软件ANSYS Workbench对四头高速电主轴模态进行了分析,考察了轴承刚度对电主轴模态特性的影响,并针对外界约束条件选用了合适方法来提取出电主轴的前八阶振型,得出其临界转速。结果表明:相邻两阶阵型表现为正交状态,轴承的动刚度对主轴单元的固有频率及各阶振型有很大影响,电主轴设计合理,可安全运行。     

一种压缩机用滑动轴承实验设计

大型压缩机转子实际运行过程中转速很高(可达60000r/min),而齿轮啮合、气流冲击总会给转子带来一定的扰动。这就导致了滑动轴承在这种高速轻载工况下不得不面对一系列稳定性问题。文章提出一种压缩机用滑动轴承实验设计方案。设计的实验台系统包括实验轴承及实验转子、驱动装置、加载装置、数据采集和润滑装置5个部分,并设计了常规工况、超速工况、参数识别、故障诊断、轴承性能评判等实验内容。同时结合有限元软件仿真分析设计了低速可行性验证实验为压缩机用滑动轴承实验设计方案提供可行性验证和相应的测试准备。     

递纸机构实验台测试技术的研究

为了了解递纸机构的动态特性,建立了递纸机构实验台。通过对实验台的噪声测试,得到了实验台在各种工作速度下噪声的主要频率;通过对实验台的振动测试,得到了实验台本身的各阶固有频率。在此基础上,结合理论计算所得到的齿轮的啮合频率,找到了实验台在各种速度下的噪声源。结果表明,递纸机构实验台的噪声与其本身的固有频率有较大关系。实验台的拉梁、罩壳等也会产生噪声,在某些速度下,这些噪声会成为主要噪声源。     

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.     

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.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

The Ministry of Environmental Protection Issued "Feasible Technology Guidelines for Pollution Prevention and Control in Wood Pulping Process of the Paper Industry (Trial)" and Two Other Guiding Technical Documents

On December 27t＂, 2013, the Ministry of Environmenta Protection announced that, in order to implement ＂The Environmental Protection Law of the People＇ s Republic of China＂, improve the working system in environmenta protection technologies, and promote technologica advancement in pollution prevention, the Ministry of Environmental Protection sponsored the formulation of three guiding technical documents including ＂Feasible Technology Guidelines for Pollution Prevention and Contro n Wood Pulping Process of the Paper Industry （Trial）＂     

1~(st) Intelli-Tissue~ EcoEc Tissue Machine Supplied by PMP Group Successfully Put into Operation in China

正On April 29th,2014,Intelli-Tissue EcoEc tissue machine supplied by PMP Group successfully put into operation at Hebei Xuesong Paper Co.,Ltd.,this is the first such kind of paper machine of PMP Group in China.