静电纺丝拉伸模型与实验

利用珠链纤维模型对静电场作用下聚合物溶液的纺丝拉伸过程进行模拟,通过计算纺丝过程中聚合物射流细度随时间的动态变化,可得到不同工艺条件下所纺纤维的直径。为了验证模型的可行性,采用聚乙烯醇溶液进行静电纺丝实验,初步探讨纤维细度与接收距离之间的关系。实验结果表明,当接收距离在14~40 cm范围内,纤维直径随接收距离的增加有逐渐变细的趋势。通过与模拟结果的对比可以看出,在接收距离小于30 cm时,实验数据和模拟结果吻合较好。     

2.5维机织复合材料的几何结构模型与验证

为验证2.5维机织复合材料结构与其力学性能的关系,基于对材料断面显微照片的观察和分析,假定纤维束截面为为跑道形,建立了2.5维机织复合材料的单元结构模型。借助模型推导出纱线在几种典型结构（浅交弯联、浅交直联、深角联）的单元体结构内的纱线长度、接结经的取向角和纤维体积分数,并对材料进行拉伸、压缩性能预测。制作了满足要求的2.5维机织复合材料实验件并对其进行力学性能测试,通过试验值和预测值的对比,验证几何模型的正确性。     

卵形体农产品大小头自动定向翻转运动仿真模型建立与试验验证

为了深入探讨卵形体农产品大小头自动定向中翻转运动规律的影响因素和动力学特性,降低实际试验成本,设计了由卵形体、输送辊、导向杆组成的数字化虚拟样机(仿真模型),并运用ADAMS运动仿真技术对卵形体翻转运动过程进行了仿真,创建了翻滚距离和导向杆作用距离仿真值的测量方法;在此基础上,对不同长轴L、短轴B、蛋形角θ和输送辊中心距E、导向杆弯曲角度γ、输送速度v条件下仿真值和实际试验值进行比较分析。结果表明,仿真结果与实测结果呈现相同的变化规律,相对误差均在10%以内,所建的仿真模型是可信和有效的,利用该模型研究翻转运动规律是可行的。     

Numerical simulation and experimental investigations of air drawing model and air jet flow field model in wide slot positive pressure spunbonding process

An air drawing model of polymers and a model of the air jet flow field model in wide slot positive pressure spunbonding process are established. The air jet flow field model is solved by means of the finite difference method. The numerical simulation computation results of distributions of the air velocity match quite well with the experimental data. We find that the variation of the density and the specific heat capacity of polymer melt at constant pressure with polymer temperature have much effects on fiber diameter. The newly developed formulas were incorporated into a spunbonding theoretical model to predict the fiber diameter of nonwoven web. The air drawing model of polymer is solved with the help of the distributions of the air velocity measured by a Particle Image Velocimetry (PIV). The predicted fiber diameters agree with the experimental data well. It can be concluded that the higher air pressure, higher air velocity and air temperature can yield the finer fibers diameter. The higher inlet pressure and smaller jet angle will all cause higher x-axis position of air velocity and air pressure, which are beneficial to the air drawing of the polymer melt and thus to reducing the fiber diameter.     

An experimental verification of cut-pile carpet compression behavior

In a recent theoretical work by the authors, a new theoretical approach to the cut-pile carpet compression based on elastic stored energy was developed. In this study, cut-pile compression behavior was experimentally investigated and the proposed theoretical model verified. Cut-pile carpet samples with three types of pile yarns and five pile density levels were produced and their compression behavior was tested under a constant compressive stress. Then the total energy of pile deformation was calculated and analyzed. Predicted results based on the presented theory show a fairly good agreement with experimental results.     

双螺杆压缩机CFD仿真分析及实验验证

针对双螺杆压缩机流体域形状复杂并随时间变化的特点,运用STAR CCM+软件进行计算流体动力学(CFD)分析,并搭建试验平台验证分析结果的准确性。通过对比仿真监测点和与之相对应的试验实测点的压力,两者在压力值和压力波动周期等方面具有较好的一致性,验证了CFD分析结果的可信度。     

北京市售巴氏杀菌乳的消费调查及实验验证研究

目的了解北京地区消费者巴氏杀菌乳的消费习惯,评估储存温度和时间对巴氏杀菌乳中微生物数量的影响,为消费者正确储存巴氏杀菌乳提供依据。方法北京10个行政区各选择1个大型超市进行问卷调查,调查内容包括巴氏杀菌乳的饮用频率、储存温度和时间等。依据调查结果模拟消费者储存条件,结合微生物生长规律,采用正交试验方法探究温度和时间对巴氏杀菌乳中菌落总数及金黄色葡萄球菌(Staphylococcus aureus)数量的影响。结果调查问卷结果表明,18岁以下、18～54岁和55岁以上的消费者中,每天饮用巴氏杀菌乳的比例最高分别为15.4%、49.0%和75.9%;所调查消费者中,将巴氏杀菌乳储存在2～6℃、室温、-20℃的比例分别为75.0%、14.6%、5.5%;模拟实验结果表明储存温度对巴氏杀菌乳中微生物影响更大, 37℃储存48h后,菌落总数和S.aureus数量达到1.26×10~5CFU/mL和1.20×10~4 CFU/mL。结论北京市饮用巴氏杀菌乳的消费者主要集中在中老年人群;部分消费者(24.2%)不明确巴氏杀菌乳的正确储存温度;不当的储存温度导致巴氏杀菌乳中的菌落总数和金黄色葡萄球菌的数量增加。     

混合均匀度回归模型的建立与验证

为了揭示混合机工作过程中混合均匀度的变化规律,为混合机的设计和使用提供理论基础,在试验的基础上,通过回归方法建立了混合均匀度的回归模型,并用实例进行了验证和分析,研究结果表明,建立的回归模型适用性广,可为混合机的设计和使用提供技术依据.     

用KM小鼠实验验证肉类寒热性物质基础的判别模型

通过Fisher判别法、聚类分析、因子分析等多种分析方法建立了肉类寒热性的数学判别模型,为寒热性肉类的判别提供了依据。通过SPF级KM小鼠的肛温、饮水量、脏器重量和血液生化指标来验证数学模型的寒热性。      

Metabolic control analysis for lysine synthesis using Corynebacterium glutamicum and experimental verification

Metabolic control analysis was carried out for the lysine biosynthetic pathway in Corynebacterium glutamicum ATCC 21253 using mechanism-based kinetic models developed for enzymatic reactions for this pathway. The rate-limiting steps during lysine production were determined with the aid of flux control coefficients, which indicated that the lysine synthesis flux is governed mainly by both aspartokinase and permease activity in the export system. Analyses indicated that an increase in the activity of aspartokinase would significantly alleviate its effect on the overall flux, and the limiting step is expected to shift to permease and other lysine synthetic enzymes. The influences of many participating precursors and cofactors on lysine synthesis flux were also investigated through the calculation of response coefficients for individual parameters. Although most parameters were not found to exert significant influences on lysine flux, extracellular lysine concentration was found to have a substantial effect on lysine production, and detailed analysis indicated that a decrease in the external lysine concentration will enhance the metabolite synthesis considerably and shift the control from export step to other steps. Although a decrease in external pH (pH0) seems to increase lysine flux, consideration of the export carrier concentration in response to external pH confirmed the optimum pH0 to be 7.0. Two types of recombinant strains overexpressing aspartokinase and dihydrodipicolinate synthase were constructed to verify the results obtained from metabolic sensitivity analysis.     

静电纺丝法浅析

文章对静电纺丝的国内外现状做了简单介绍,阐述了静电纺丝的机理特别是泰勒锥的形成过程,分析了工艺参数对静电纺丝产品的影响,并对静电纺丝的应用前景以及产业化生产问题进行了预测。     

Electrospraying and Electrospinning of Chocolate Suspensions

Novel applications of efficient and economical techniques such as electrospraying and electrospinning in chocolate processing could be a strategy to help manufacturers improve declining sales growth rate in a saturated confectionery market. In this study, electrosprayed near-monodisperse particles have been produced using chocolate suspensions. Electrospun fibres have also been created from a commercial chocolate sauce. The effects of process parameters such as sugar concentration, addition of electrolytes (NaCl), flow rate, applied voltage and collection distance on the production and morphology of as-sprayed chocolate particles were studied. A positive linear trend in the electrosprayed chocolate particle diameter and diameter distribution range with increasing sugar concentration in the chocolate suspension was demonstrated. Sugar concentrations of 30–35%w/w resulted in very fine, near-monodisperse chocolate particles. Trace amounts of electrolyte at 1%w/w were found to decrease the average particle diameter and improve the monodispersity of the particles produced. The addition of NaCl at low concentrations increased the electrical conductivity and, to a lesser extent, the surface tension of the chocolate samples. Further increases in NaCl concentration to 3%w/w did not bring any additional decrease in the average diameter of the chocolate particles. In addition, the observed modes of electrospraying and the characteristics of chocolate particles obtained under these were investigated. Bead-on-string morphology was commonly observed among electrospun chocolate fibres. Moreover, satellite particles and very fine fibres were obtained during the transition between electrospraying and electrospinning. The continuous alternating shape of elongated spheres and thin fibres may have the potential for varying the microtexture of the chocolate products.     

喷气织机主喷嘴引纬流场数值模拟与实验验证

为了充分了解主喷嘴射流速度分布以便于优化喷气织机引纬系统的工艺参数,本文利用计算流体动力学软件Fluent对主喷嘴引纬流场进行数值模拟,得到主喷嘴出口射流中心线上的速度分布曲线及垂直于中心线的不同截面内流场的速度等值线图。为了验证数值模拟的合理性,通过实验获取了流场中不同点的速度,并与数值模拟结果做了分析比较,最终表明：在主喷嘴出口处速度实验测试值比数值模拟值小了约60m/s,随着流场延伸两者差距不断缩小,在距主喷嘴出口70mm以后两者具有较好的一致性。主喷嘴引纬流场的数值模拟结果在生产实践中值得借鉴。     

Electrospinning of food-grade polysaccharides

A range of polysaccharides of different sources was investigated with respect to their ability to form fibers using electrospinning from aqueous solutions. Polysaccharides were chosen from different sources i.e. from plants, seaweeds and micro-organisms. The polysaccharides derived from plant sources were exudates (galactomannans, glucomannans) and other vegetable sources (e.g. starch, methylcellulose). The polysaccharides from the seaweeds were carrageenans and alginate and the polysaccharides from microbial origin ranged from non-branched (pullulan) to brush-like (e.g. dextran). The polysaccharides could be divided into three categories according to their electrospinning behaviour. The first category was able to form fibers, the second category was able to form a jet but no fibers and the third category (largest, containing all charged polysaccharides tested) was not able to form a jet at all. Possible reasons for a particular type of spinning behaviour are discussed, starting from the characterization of the polysaccharides and their solutions. The intrinsic viscosity, shear viscosity and conductivity were determined for the different polysaccharide solutions. Based on these results, possible relations with electrospinning behaviour are discussed. It was concluded that the overlap concentration and shear thinning properties of the polysaccharides are crucial for successful spinning. Concentrations in the range between 10 and 20 in units of the overlap concentration, probably giving rise to a sufficiently high Trouton ratio, were found to be a necessary condition for spinnability. Equipment settings and conductivity are of secondary importance and merely play a role in optimization of the process.     

食品微生物定量风险分级模型初探与验证

目的 构建吉林省食品微生物定量风险分级模型并进一步验证。方法 利用食物消费量、交叉污染和烹调行为等相关数据,以2014年吉林省食品微生物监测数据为例,通过风险矩阵对不同致病菌污染所致人群健康风险进行风险分级并利用Risk Ranger进一步验证。结果 通过分级模型发现调理生猪肉中存在沙门菌污染,乳与乳制品和三明治中单增李斯特菌污染存在中风险;发现41.67%的食源性疾病病例由沙门菌引起;中式凉拌素菜导致的食源性疾病人数最多,占所有病例的69.06%;75.22%的食源性疾病病例是由于不完全烹调所致;经Risk Ranger进一步验证提出应对“调理生猪肉-沙门菌”组合优先进行风险评估,不完全烹调及其干预措施是评估的重点环节;根据年发病率推算,吉林省2 700万人中,每年约有3.6万人发生食源性疾病。结论 吉林省食品微生物定量风险分级模型初步建立,但需要进一步修正模型参数,更加准确的估算发病率。     

A generalized model for aerobic granule-based sequencing batch Reactor. 2. Parametric sensitivity and model verification

The sensitivity of the effluent chemical oxygen demand, NH4+-N and volatile suspended solids concentrations toward the stoichiometric and kinetic coefficients, oxygen diffusivity, characteristics of granules, and operating parameters was analyzed. With such a parametric sensitivity analysis, calibration of the model, which was established for describing aerobic-granule-based sequencing batch reactor (SBR) in the accompanying paper, was performed by comparing the measured and predicted values for model components. Thereafter, the established model was verified with the experimental results for four aerobic-granule-based SBRs with different granule sizes and fed with different wastewaters. The verification results show that the model established in this work was applicable to simulating and predicting the performance of an aerobic-granule-based SBR.     

静电纺间位芳纶纤维的制备及其性能

以N,N-二甲基乙酰胺（DMAc）为溶剂,加入LiCl和CaCl2制备2种溶解体系,研究了间位芳纶纤维在2种溶解体系中的溶解性能及芳纶溶液的静电纺丝性能。间位芳纶纤维在N,N-二甲基乙酰胺中只能发生有限溶胀,氯化盐的加入有利于芳纶纤维的快速溶解。盐的种类及质量分数对纤维的溶解量、溶解时间以及溶液的黏度具有重要的影响。利用制得的溶液,采用高压静电纺丝技术制备了直径100～500nm的纳米芳纶纤维,纳米纤维直径随纺丝溶液质量分数和盐质量分数的增加而增大。以LiCl/DMAc为溶解体系制得的纳米纤维的均匀性随黏度增大而逐渐提高,且纤维形貌优于在CaCl2/DMAc溶解体系中制得的纤维,但以CaCl2/DMAc溶解体系制得的纳米纤维其热性能明显优于LiCl/DMAc溶解体系纺得的纳米纤维。LiCl/DMAc溶解体系中芳纶溶液质量分数为11％时,制得的纳米芳纶纤维非织造布的力学性能最优。     

静电纺纳米聚乙烯吡咯烷酮及其共混纤维的研究

采用静电法纺制出纳米聚乙烯吡咯烷酮(PVP)纤维及其共混纤维,借助旋转粘度计、电导率仪、扫描电镜(SEM)等测试表征方法,确定了纺制静电纺纳米PVP纤维的较好工艺:p(PVP)=180 g/L,纺丝电压15 kV.并研究了PvP与聚环氧乙烷(PEO)、共聚维酮S-630及聚偏氟乙烯(PVDF)的共混纺丝.结果表明,纳米PVP/PEO共混纤维的形貌较好.     

静电纺丝纳米纤维的方法与应用现状

主要介绍了利用不同的静电纺丝收集装置设计得到多种排列形式的纳米纤维聚集体及聚合物纳米纤维的应用.说明了静电纺丝技术可以得到各种各样的聚集体,是目前制备纳米纤维比较有效的方法,提高了由纳米纤维制备的产品质量,可以应用于特定的改性方面.     

喷气涡流纺纱线拉伸断裂强力预测模型构建与验证

为更好理解喷气涡流纺纱线结构对纱线强力的影响机制,实现纱线结构优化设计,首先在观察与分析喷气涡流纺纱线结构基础上,构建了喷气涡流纺纱线的几何结构模型;阐述了喷气涡流纺纱线内纤维的受力情况,以此得出喷气涡流纺纱线拉伸断裂强力的数学模型;通过对喷气涡流纺纱线拉伸断裂强力预测值与实测值的比较进行模型验证。研究结果表明：纱线强力预测模型对纱线拉伸断裂强力的预测结果与实测值较接近,同时,纱线中毛羽纤维造成的纱线半径计算的误差会影响到模型预测结果的精确性。