谷朊粉干燥系统中尾气回收的研究

提出在谷朊粉干燥过程中对尾气进行回收利用问题.通过传热效率和传热单元数方法计算谷朊粉尾气回收系统理论节能效率与实际节能效率进行对比,做出能源节约效率图,通过最小二乘法拟舍出现场环境温度与能源节约率的经验公式,对尾气回收系统设计及干燥系统能耗计算具有一定指导意义.     

基于离散元法的螺旋喂料器流量计算修正

针对螺旋喂料器实际流量检测值与传统计算式计算值相差较大的问题,采用响应面试验对螺旋喂料器的流量计算式进行修正。考虑到实际试验的复杂性,采用离散元仿真流量值与计算式计算值的比值作为响应,以对流量比值影响显著的螺距、转速、管径为试验因素设计响应面试验,得到3个因素与响应值之间的二阶回归方程,由此进一步得到螺旋喂料器的流量计算式。为进一步验证修正后流量计算式的可行性,根据设计要求,用SolidWorks软件建立三维模型并进行仿真分析,发现仿真所得流量值为1.258t/h,与修正式计算所得流量值1.210t/h的误差为3.97%,表明了流量修正计算式的合理性。     

超临界二氧化碳萃取藿香叶浸膏的数学模型

考察在超临界二氧化碳萃取藿香叶浸膏工艺中萃取时间、二氧化碳流量、萃取温度、萃取压力四个因素对萃取率的影响.利用单因素试验以及正交试验得到相应实验数据,对这些数据进行多元多项式拟合,得到反映工艺条件与萃取率之间关系的数学模型,由此模型计算出最佳工艺条件.     

基于渗透二项式定律的多层织物多孔介质建模研究

为了构建一个能真实反映织物特征的多孔介质模型,首先测试不同厚度的织物在不同压差下的气流速度;然后对测试数据进行拟合分析得到压降与气流速度之间的函数关系,并利用多孔介质数学模型与拟合函数之间的关系,得到多孔介质模型的参数;最后利用多孔介质模型进行流体计算,证明模型可以用于模拟分析。结果表明:在一定范围下,压降和气流速度之间具有二次函数关系;得出函数拟合值与测试值之间的误差小于7%,模拟值与测试值之间的误差小于6%。所以,随着织物厚度增加函数关系趋于一致,构建的多孔介质模型符合织物的实际情况,并可以用于研究气流在织物内部的流动特征。     

新的计算VAR的可行方法

理论的VaR(风险值)与实际应用之间存在着很大的距离。为了缩短这种差距,本文提出了一个计算VaR的新方法。并利用实际的收益率分布检验了模型,表明新的方法较正态分布更能精确的计算实际的VaR及分布。     

条形织物的折皱弯曲性研究

把弹性较好的条形织物看成是一个具有内摩擦约束的弹性条，通过简单的流变模型及公式将织物在弯曲折皱过程中的重要性质表征出来；对毛、毛／涤及尼龙条形织物在折皱时力与变形的关系进行了分析与计算，利用织物在KES-FB-3压缩仪上得到的实验数据、实测点计算所得的模型参数，能较好地反映织物折皱弯曲规律。理论计算值与实测值吻合程度较好。     

基于压缩弹簧的PPS/PET交织粘扣带力学模型研究

以压缩弹簧为基础,建立了聚苯硫醚/聚酯(PPS/PET)交织粘扣带的单钩强力力学模型,并进而建立了粘扣带剥离强度与剪切强度力学模型,再通过实际测试,修正模型中的参数,得到了粘扣带剥离强度与剪切强度的理论计算式。经试验检验可知,由理论计算式计算的粘扣带的理论强度与实测强度的偏差百分率小于2.5%,故该强度力学模型可在有限范围内用于PPS/PET交织粘扣带剥离强度与剪切强度的计算和预测。     

基于ANSYS CFX的织物透气性数值计算

为了快速设计出透气性符合实际要求的织物,并研究气流在织物内部的运动和压力、压强的变化规律,文章提出了利用ANSYS CFX对织物透气性进行数值计算的方法。首先建立织物模型,再在此基础上对织物模型进行处理,然后对不同压强下的织物进行数值计算。结果表明:气流主要通过织物孔隙和纱线之间的间隙,并且通过孔隙时由于迁移加速度的存在速度会增加;通过空隙时在纱线表面会存在很大的剪切力和压力;模拟值与实验值进行比较得到的模拟误差小于16%,所以得到的模型可以反映织物的实际特征。造成误差的主要原因包括:测试偶然误差、模型参数误差、边界条件与测试条件之间的差别。     

梗丝填充值与烟支吸阻关系的建模及应用

为控制卷烟吸阻的稳定性,研究梗丝填充值对烟支吸阻的影响程度,进行了梗丝填充值与烟支吸阻的线性回归分析。结果表明:梗丝填充值与烟支吸阻之间存在正相关关系;所建模型预测结果与实测结果的相对偏差的绝对值均在2%以内,与实际验证拟合度较好。在实际生产应用中,如果排除烟丝含水率、烟支质量、滤棒压降等因素的影响外,利用此模型,可以用控制梗丝填充值的有效措施来控制烟支吸阻。     

清酒过滤指标的控制

<正>啤酒过滤工段的主要工作是:把发酵液稀释到最终销售产品的浓度;控制清酒浊度小于公司标准0.2EBC;溶解氧小于25ppb;控制清酒二氧化碳的含量和卫生指标达到公司的要求;另外还有消耗控制等。以下的一些措施是工作多年的经验,供同行参考。1过滤过程溶解氧的控制(1)脱氧水溶解氧的控制1)制备脱氧水前用水置换稀释机、脱氧水罐、管路内的空气,再用二氧化碳置换系统内的水,二氧化碳纯度达到99.9%以上,系统保持正压,压力大于O.1Mpa.     

Predictive modelling and validation of Listeria innocua growth at superatmospheric oxygen and carbon dioxide concentrations

The effect of superatmospheric oxygen and carbon dioxide concentrations on the growth of Listeria innocua, which was used as a model organism for the pathogen Listeria monocytogenes, was evaluated. The bacteria were grown on a nutrient agar surface at 7 degrees C. Three carbon dioxide levels (0%, 12.5% and 25%) were combined with different levels of high oxygen concentrations (above 20%) based on a mixture design. The applied oxygen concentrations did not significantly influence the growth. High CO2 concentrations, on the contrary, reduced the maximum specific growth rate and prolonged the lag time. An overall model to describe the growth of L. innocua under high carbon dioxide conditions was constructed based on nine growth experiments, using a weighted one-step regression procedure. The influence of carbon dioxide on lag time and maximum specific growth rate was described using Ratkowsky-type models and inserted in the Baranyi equation. The model described the growth very well. To assess the validity of the model, 14 additional experiments were carried out. There was a good correlation of the model predictions and observed validation data.     

Indirect methods for characterization of carbon dioxide levels in fermentation broth

Various factors which influence dissolved carbon dioxide levels were indirectly evaluated in pilot scale and laboratory studies. For pilot scale studies, off-gas carbon dioxide (percentage in exit air) was measured using a mass spectrometer and then its potential impact on dissolved carbon dioxide concentrations qualitatively examined. Greater volumetric air flowrates reduced off-gas carbon dioxide levels more effectively at lower airflow ranges and thus lowered expected dissolved carbon dioxide levels through gas stripping. Lower broth pH values decreased off-gas carbon dioxide levels but increased expected dissolved carbon dioxide levels due to the pH-dependence of the gas/liquid carbon dioxide equilibrium. While back-pressure increases had an insignificant effect on off-gas carbon dioxide levels, they directly affected expected dissolved carbon dioxide levels according to Henry's law. Laboratory studies, conducted using both uninoculated and inoculated fermentation media, quantified the response of the media to pH changes with bicarbonate addition, specifically its buffering capacity. This effect then was related qualitatively to expected dissolved carbon dioxide levels. Higher dissolved carbon dioxide levels, as demonstrated by reduced pH changes with bicarbonate addition, thus would be expected for salt solutions of increased ionic strength and higher protein content media. In addition, pH changes with greater bicarbonate additions declined for fermentation samples taken over the course of a one week cultivation, most likely due to the higher protein content associated with biomass growth. The presence of weak acids/bases initially in the media or formed as metabolic by products, as well as the concentration of buffering ions such as phosphate, also were believed to be important contributing elements to the buffering capacity of the solution.     

基于主成分分析验证气调对番茄品质的影响

研究低温环境下不同体积分数的混合气体对番茄感官品质、营养价值的影响。以番茄作为试验研究对象,通过预冷处理,选择开孔率5%的聚乙烯食品包装袋包装,放在温度为8 ℃ CO2体积分数为6%的气调箱内,用N2调节O2体积分数为2%、4%、6%、8%和10%。每隔2 d检测一次番茄品质（质量损失率、色差L*值、TSS、TA及主观评价）之后对6个评价指标进行标准化处理,采用主成分分析法建立得分函数,并用传统感官评价验证得分模型。试验研究表明：4% O2+6% CO2气调环境下番茄各项指标可以维持较好的水平。综合函数评价得分显示在长期气调保鲜过程中,低氧环境有利于番茄保持较高品质。传统感官评价方式与综合函数有一致性。主成分分析法表明4% O2+6% CO2的气调环境下具有较高的得分水平,可以显著维持保鲜过程中番茄的营养价值,并延长气调保鲜周期。     

分散红11在超临界二氧化碳中的溶解度及其模型拟合

为实现超临界二氧化碳(CO₂)染色的工业化应用,采用自主研发的高压超临界流体实验装置,在温度为353.15~393.15 K、压力为16~24 MPa条件下,利用动态法测量了分散红11(1,4-二氨基-2-甲氧基蒽醌)在超临界二氧化碳中的溶解度,并采用Chrastil经验模型和MST方程对实验结果进行拟合,探讨影响分散染料在超临界CO₂中溶解度的因素。结果表明:压力越高,二氧化碳密度越大,分散红11在超临界CO₂中的溶解度越高;随温度升高,分散红11的溶解度先增加后降低;分散红11的最优溶解度工艺条件为温度383.15 K,压力24 MPa;Chrastil经验模型关联水平在0.90以上,MST方程关联水平为0.55,Chrastil经验模型关联结果优于MST方程。     

重组毕赤酵母表达人血清白蛋白-人白介素2融合蛋白过程的代谢特性

分析了重组甲醇营养型毕赤酵母在5L多参数自控发酵罐上生产人血清白蛋白-人白介素2融合蛋白(HSA-IL-2)的发酵过程。在使用多种在线传感器和离线检测参数的基础上,应用相关性分析的方法将细胞生长的关键酶(乙醇氧化酶、葡萄糖-6-磷酸脱氢酶和异柠檬酸脱氢酶)酶活和代谢特性相关联。实验结果显示,甲醇诱导后葡萄糖-6-磷酸脱氢酶和异柠檬酸脱氢酶的酶活分别下降了46.1%和66.8%,说明胞内代谢流发生了迁移:三羧酸循环(TCA)和磷酸戊糖途径(HMP)中代谢流通量下降,甲醇完全氧化代谢成为主要代谢流。此外,在不同控制策略下,乙醇氧化酶的酶活和重组蛋白HSA-IL-2表达量也呈现出一定的差异。高溶氧低甲醇控制方式下HSA-IL2的表达量达到27mg/L,比低溶氧高甲醇条件下的表达量高33.7%。     

Synchronization affector of autonomous short-period-sustained oscillation of Saccharomyces cerevisiae

When the yeast Saccharomyces cerevisiae was grown under aerobic continuous culture, an autonomous shortperiod-sustained oscillation appeared. This oscillation was observed in concentrations of various extracellular and intracellular parameters, such as ethanol, acetate, glycogen, dissolved oxygen and intracellular pH. In this work the synchronization affecter of this oscillation was investigated. Ethanol was found not to be the synchronizer of the oscillation because a pulse of ethanol did not affect the phase or period of the oscillation. The oscillation was dependent on the aeration rate, i.e., the oscillation occurred only between 150 and 600 ml min⁻¹. However, the oxygen concentration did not influence synchronization as an upward shift in the oxygen concentration of the gas flow did not affect the sustainability of the oscillation. On the other hand, synchronization was stopped by an enhanced gas flow rate, keeping dissolved oxygen tension at the oscillatory condition, suggesting that synchronization was caused by a volatile compound in the culture. A stepwise increase in carbon dioxide concentration of the gas flow rate ceased synchronization, yet the oscillation seem to continue in each individual cell. Oscillatory behaviour of intracellular pH and carbon dioxide evolution rate showed a phase difference of 90 degrees. Based on these facts it is postulated that carbon dioxide, through the influence of its dissociation on intracellular pH, could be the synchronization affector of the autonomous short-period-sustained oscillation of S. cerevisiae.     

Effect of moderate electric fields in the permeation properties of chitosan coatings

Edible films and coatings can provide additional protection for food, while being a fully biodegradable, environmentally friendly packaging system. Preliminary works have shown that the presence of a moderate electric field during the preparation of chitosan coating solutions may influence e.g. their transport properties. If such effect is confirmed, moderate electric fields could be used to tailor edible films and coatings for specific applications. The aim of this work was to determine the effect of field strength on functional properties of chitosan coatings (obtained from lobster from the Cuban coasts). Four different field strengths were tested (50, 100, 150, 200 V cm⁻¹) and, for each electric field treatment, the water vapor, oxygen and carbon dioxide permeabilities of the films formed were determined, together with their color, opacity and solubility in water. The surface microstructure of the films was analyzed using atomic force microscopy (AFM).The results showed that ohmic heating had statistically significant effects on film's physical properties and structure. In general, the most pronounced effect of the field strength was observed for treatments made at 100 V cm⁻¹ or higher, a positive correlation being found between the water vapor, oxygen and carbon dioxide permeability coefficients and field strength. The AFM results show that the surface of chitosan films is much more uniform when an electric field is applied, which may be related with a more uniform gel structure leading to the differences observed in terms of transport properties.     

Gas exchange in modified atmosphere packaging. 1: A new theoretical approach for micro-perforated packs

Gas transport and exchange through the perforations in micro-perforated packs used in modified atmosphere packaging were numerically modelled by using Stephan-Maxwell laws, and, outside these perforations, by Fick's law. the model accounts simultaneously for oxygen, carbon dioxide, nitrogen, argon and water vapour. Fruit and vegetable respiration was approximated by Michaelis-Menten kinetics depending on oxygen concentration with an uncompetitive inhibition due to carbon dioxide. Concentration equilibrium was reached after 2 to 3 days, depending on the void volume and on the diffusion properties of the packs. the equilibrium concentrations were dependent on the number of perforations, their diameter, the thickness of the film and the temperature. However, a pack which makes 10% oxygen possible within the pack at 10°C might induce anaerobiosis at 20°C.     

Determination of CO2 origin (natural or industrial) in sparkling bottled waters by 13C/12C isotope ratio analysis

This paper describes an isotope control method designed to identify the origin of CO₂ in sparkling bottled waters. The method is based on the analysis of the ¹³C/¹²C ratio in the dissolved inorganic carbon (DIC) of carbonated bottled water. Natural carbonated natural water has δ¹³C_PDB (DIC) values between −8‰ and +7‰. Generally, the industrial carbon dioxide injected into mineral bottled water is produced from hydrocarbons by burning or chemical processing. Hydrocarbons, and their derived CO₂, are characterised by a low ¹³C/¹²C ratio. Thus, a single analysis distinguishes the carbon dioxide in the bottled water (i.e. either from a natural source or added exogenous CO₂ of industrial origin). Rarely, CO₂ can be obtained from other industrial sources, mainly as a by-product of fermentation plants. Nevertheless, the carbon isotope fingerprint allows detection of the industrial gas injected in most of these cases.