小白菜热风干燥特性研究

研究了一定条件下风速与风温对经烫漂预处理的小白菜热风干燥过程的影响,拟合了干燥曲线方程,并计算了临界含水量、传热膜系数α与传质系数kH等热风干燥动力学参数。而各条件下的小白菜干燥曲线均符合Page方程。小白菜干燥过程中的传热膜系数α与传质系数kH受风机频率影响明显,且随风机频率增大而增大,但两者均基本不受干燥温度影响。     

胡萝卜薄层干燥动力学模型研究

为探索胡萝卜热风干燥过程中水分的变化规律,本研究以胡萝卜为干燥对象,进行薄层干燥特性及模型研究,探讨不同温度、风速及物料厚度条件下胡萝卜水分比与干燥时间的关系,建立动力学模型;以Fick扩散定律为依据,确定胡萝卜一维传热传质的有效水分扩散系数并建立其数学模型。结果表明：胡萝卜薄层干燥动力学模型可用Page方程来描述,并通过回归分析确定方程系数m、k,通过多元线性回归方法得到有效水分扩散系数（Deff）与温度、风速和厚度的表达式,实验得到的Deff值在0.84×10-9～6.69×10-9 m2/s范围内随着干燥温度、风速和物料厚度的升高而增大。     

脱水米饭冷冻干燥传质模型推导与初步应用

通过控制影响传质的压力、温度等环境因素,研究了冷冻干燥过程中脱水米饭在不同压强(100、60、20 Pa)和温度(60、50、40、30℃)条件下,水分升华速率的变化情况,并建立了相应的传质方程。实验结果表明,升华速率与干燥时间存在显著的线性关系,且传质方程与辐射传热型单侧传热单侧传质模式下的实际过程一致。     

基于逆投影变换的纱筒纱线余量检测算法

纱筒纱线余量检测是纺织行业自动化生产过程中的重要一环,针对目前纱线余量检测算法检测精度低的问题,提出一种基于三点逆投影变换模型的纱筒纱线余量检测技术。根据实际生产过程中相机与纱筒的位置关系,建立三点逆投影变换模型进行初步矫正。为得到更好的图像矫正结果,设置补偿矩阵并根据内外筒位置信息优化变换矩阵,最后将逆投影变换后的图像按照改进的椭圆坐标变换模型展开为矩形,根据余量计算准则计算得到纱筒纱线余量。在自主搭建的检测平台上进行实验,结果表明,本文算法检测精度在5 mm以内,基本满足实际生产要求,可为纺织产业自动化生产提供依据。     

葡萄籽原花青素提取动力学研究

通过分析葡萄籽原花青素提取过程的传质机理,确定以溶质浓度的宏观变化描述微观过程。在质量守恒原理的基础上建立动力学方程,并通过实验对方程进行检验。运用Arrhenius 方程求出提取过程中重要的动力学参数,其表观活化能为2.08 × 104J/mol。结果表明：所建立的方程能够较好的描述葡萄籽原花青素的提取过程,原花青素提取符合扩散传质的动力学规律。     

圆纬机上不锈钢纤维纱筒底座的设计

针对不锈钢纤维在编织过程中不能由纱筒正常退绕的问题,通过分析不锈钢纤维与常规纺织纤维的摩擦性能和纱线毛羽,提出不锈钢纤维摩擦阻力大、纱线毛羽较多会对退绕产生一定影响。并结合金属纤维使用常规纱筒底座时存在的不足,设计一种底座内芯直径可无级调节的纱筒底座,避免不锈钢纱线退绕时的纱筒抖动和掉落等问题,使不锈钢纱线的退绕稳定、退绕条件一致性好,该纱筒底座也可用于其他金属纤维的退绕中,以及其他编织机上。     

铝套管锭子用经纱筒管的特点与使用

为了选好、用好铝套管锭子和经纱筒管,介绍了铝套管锭子的基本结构、特点和分类,详细分析了经纱筒管的内孔设计、外表设计和材质选择,以及正确使用铝套管锭子和经纱筒管的方法。指出:选好用好铝套管锭子和经纱筒管,关键是要熟悉其基本特性并掌握使用方法;铝套管锭子和经纱筒管品质的提高加上优秀的纺纱人才,是纺出优质纱线的必要前提与保障。     

马铃薯淀粉废液超滤传质过程的研究

采用超滤设备对马铃薯淀粉生产过程中的废液进行循环浓缩,研究在室温、操作压力为0.16 MPa循环浓缩时,膜通量与料液中蛋白质的质量浓度之间的变化规律,得到马铃薯淀粉废液超滤浓缩过程中的传质方程,依据传质方程求出形成凝胶层的马铃薯蛋白质质量浓度为71.582 g/L;依据阻力模型理论,建立操作压力与膜通量的模型,并探讨不同操作压力区域对膜通量的影响。     

去氨方式与碱丝光对棉织物性能的影响

一、引言去氨过程是液氨处理中具有重大意义的一个步骤,不同的去氨方式将带来完全不同的处理效果。去氨方式的种类很多,归纳起来主要有两大类:温热去氨与干热去氨。湿热去氨是利用热流(热水流或热蒸汽流)处理吸氧后去除;干热去氨则是利用干热烘燥使织物上的氨挥发     

鱼肉馅货架期预测的电子鼻评价与研究

本实验研究了不同的储存温度下鲤鱼肉馅的的品质变化。对鲤鱼肉馅在不同的贮存温度(-4、2、8℃)和贮存时间下理化指标TVB-N﹑菌落总数进行测定,建立2个指标的级动力学模型,与Arrhenius方程有很高的拟合度,鱼肉馅的货架期可以通过挥发盐基氮的预测模型得到准确的预测。用电子鼻对鱼肉馅的挥发性气味的变化进行分析,对获得的数据进行传感器信号和主成分(PCA)分析,以样品响应的稳定值为特征值进行信号分析和处理表明S2(氨氧化物)、S3(氨类)2个传感器的响应信号的变化曲线符合1级动力学模型,挥发盐基氮和菌落总数与S2传感器的变化曲线趋势是一致的。PCA分析表明挥发性气味随贮存时间的延长而发生改变,这种变化是非常显著的。通过分析可以看出电子鼻对挥发性气味的分析与理化指标有良好的对应性。     

Efficiency of urease and nitrification inhibitors in reducing ammonia volatilization from diverse nitrogen fertilizers applied to different soil types and wheat straw mulching

BACKGROUND: Some authors suggest that the absence of tillage in agricultural soils might have an influence on the efficiency of nitrogen applied in the soil surface. In this study we investigate the influence of no‐tillage and soil characteristics on the efficiency of a urease inhibitor (N‐(n‐butyl)thiophosphoric triamide, NBPT) and a nitrification inhibitor (diciandiamide, DCD) in decreasing ammonia volatilization from urea and ammonium nitrate (AN), respectively. RESULTS: The results indicate that ammonia volatilization in soils amended with urea was significantly higher than in those fertilized with AN. Likewise, the main soil factors affecting ammonia volatilization from urea are clay and sand soil contents. While clay impedes ammonia volatilization, sand favours it. The presence of organic residues on soil surface (no‐tillage) tends to increase ammonia volatilization from urea, although this fact depended on soil type. The presence of NBPT in urea fertilizer significantly reduced soil ammonia volatilization. This action of NBPT was negatively affected by acid soil pH and favoured by soil clay content. CONCLUSION: The presence of organic residues on soil surface amended with urea increased ammonia volatilization, and was particularly high in sandy compared with clay soils. Application of NBPT reduced ammonia volatilization although its efficiency is reduced in acid soils. Concerning AN fertilization, there were no differences in ammonia volatilization with or without DCD in no‐tillage soils. Copyright © 2011 Society of Chemical Industry     

Computational fluid dynamics modeling of mass transfer for aroma compounds recovery from aqueous solutions by hydrophobic pervaporation

In this work, a mass transfer study on aroma compound recovery by pervaporation process was performed using a model based on solution–diffusion theory. CFD method was employed to solve the governing mass transfer equations by considering the flux coupling. Concentration profiles of penetrants inside the membrane as well as permeation flux and aroma permeate concentration through the membrane were determined. The modeling results were validated by the experimental data obtained for pervaporative recovery of isopentyl acetate and n-hexanol from their binary aqueous solutions with composite PDMS membrane. The influence of key operating parameters such as feed aroma concentration and temperature on the flux and permeate concentration was also investigated theoretically and experimentally. The results showed that the aroma permeate concentration as well as the total and partial fluxes increased with an increase in the feed aroma content and feed temperature. The predicted results were in good agreement with experimental data.     

Evaluation of various ammonia assays for testing of contaminated muscle food products

ABSTRACT:  The indophenol method, ammonia ion selective electrode (ISE), Reflectoquant® test strips, and salicylate methods were evaluated to determine those that can be used for in-plant rapid testing of meat contaminated by ammonia refrigerant leaks. Ground eye of round beef samples were spiked with 25, 50, 100, or 200 ppm ammonia as (N) and the amounts recovered were corrected for typical background levels. The recovery of ammonia from spiked meat filtrates by ISE ranged from 98.3% to 100%± 2%, and the recovery of ammonia from spiked meat samples by ISE-perchloric acid method ranged from 90% to 110%± 8%. The measurement of ammonia in spiked meat samples by the Reflectoquant test strips ranged from 77.4% to 96.9%, but the standard deviation was higher than 14%. The recovery using the salicylate methods was less than 63% when meat samples were spiked with 25 or 50 ppm ammonia. Both indophenol and ammonia ISE are precise, give excellent recovery, and can be used for testing ammonia contamination in meat. Ammonia background levels of various commercial meat products was determined using the ammonia ISE and ranged from 87 to 166 ppm.     

Evaluation of a system of wind tunnels for field studies of ammonia loss from grassland through volatilisation

Rates of ammonia (NH₃) loss from a ryegrass sward measured using a system of small wind tunnels were compared with concurrent measurements made using a micrometeorological mass balance method. Measurements were made during two experiments within a circular plot (radius 10m) treated with urea at a rate of 200kgNha^?1. In the first experiment, air speed through the tunnels was adjusted as necessary to maintain a value of approximately 1ms^?1. This value differed on most occasions from the mean ambient wind speed which was measured at a height of 250mm and which ranged from 0.61 to 2.95ms^?1. Rates of loss measured using the wind tunnels differed by a factor of between two and five from those measured using the mass balance method; there was no consistent pattern in the differences between the rates of loss. The total losses of NH₃ measured during 15 days were equivalent to 49.1 and 30.2kg Nha^?1 for the mass balance and wind tunnel methods, respectively. In the second experiment, air speed through the tunnels was adjusted as necessary to maintain a value as close as possible to the mean ambient wind speed measured at a height of 250mm. Rates of NH₃ loss measured using the two methods did not differ significantly; total losses of NH₃ during 17 days were equivalent to 96.9 and 101kg Nha^?1 for the mass balance and wind tunnel methods, respectively. The difference between the findings of the two experiments could be attributed to the direct effect of air speed through the tunnels rather than to differences between ambient temperatures and those inside the tunnels. During and following periods of rain the rates of loss measured using the tunnels were up to six times greater than those observed with the mass balance method. Rates of loss measured by the two methods became similar again when the tunnels were moved following rain. The study demonstrates that enclosures can be designed and operated to provide reliable measurements of the rate of NH₃ loss from grassland. Potential applications of the two methods are discussed.     

The effect of steam flaked or dry ground corn and supplemental phytic acid on nitrogen partitioning in lactating cows and ammonia emission from manure

The effect of starch source and supplemental phytic acid (PA) on N partitioning and excretion and ammonia volatilization from dairy manure was evaluated with 8 midlactation cows. Cows were randomly assigned to treatments in replicated 4 x 4 Latin squares with four 18-d periods. Diets were 61% forage, 25% starch, 17.2% crude protein, and 31% neutral detergent fiber and included dry ground corn (DG) or steam flaked corn (SF) with no supplemental P (L; 0.34% P) or supplemental purified PA (0.45% P) to provide additional P from a non-mineral source. Total collection of milk, urine, and feces was conducted on d 16 to 18 of each period. Cows fed SF had lower dry matter (DM) intakes than those fed DG, which, in addition to increased starch digestibility and ruminal fermentation, contributed to higher DM digestibility. Cows fed SF had reduced feces and urine excretion compared with cows fed DG. Also, N intake for cows fed SF was lower, and N digestibility was higher, compared with cows fed DG; therefore, N excretion in both feces and urine was reduced in these cows. Despite the differences in DM intake, lactation performance was not affected by starch sources. Therefore, the efficiency of N utilization increased with SF. Addition of PA did not affect N intake or utilization. Feces and urine were subsampled from each cow, and wet feces and urine were mixed in sealed chambers in the proportions excreted. Ammonia volatilization was measured for 36 h using acid traps sampled on a planned time course. Nitrogen at time zero (A0), rate of ammonia emission (k), and residual N (R) were calculated using the exponential decay model At = A0 e(-kt) + R. Rate of ammonia loss from mixed feces and urine was lower from cows fed SF than from those fed DG. Altering dietary starch source to improve nutrient digestibility and to reduce N excretion by lactating cows may provide opportunity to reduce ammonia losses from manure.     

Modeling of the packed bed drying of paddy rice using the local volume averaging (LVA) approach

A transient heat and mass transfer model was developed for the packed bed drying of paddy rice using the local volume averaging method in this research. The required conditions for the application of the local volume averaging were evaluated including appropriate length, time, and temperature scales and justified for fixed bed paddy rice drying. Taking local thermal equilibrium in each representative elementary volume, transient mass and heat transfer governing equations were derived. The transport mechanisms considered were conduction and diffusion as well as convection heat and mass transfer. In the model, the transport coefficients were functions of moisture content and temperature, thus they changed during drying process. The governing heat and mass transfer equations were simultaneously solved using an implicit numerical method. The simulation results were compared to available experimental data from literatures. Although the physical properties were from different independent research and independent of the experimental data used for model validation, predicted results showed a reasonable agreement with the measured data.     

液氨整理近期发展概况

简要回顾液氨整理的发展历程，分析了液氨的特性和液氨处理与碱液丝光的差别。目前，液氨处理设备有间歇式和连续式两种，液氨整理与树脂整理相结合，可赋予织物超级柔软的整理效果。对于氨气的回收主要采用吸收法。     

Simulation of Cooking Cylindrical Beef Roasts

A mathematical model was developed to predict temperature and mass transfer of cylindrical beef roasts cooked in a forced-air-convection oven. The finite difference method was used to solve the simultaneous heat and mass transfer equations. Dynamic transport properties were estimated during the cooking process. The model was tested using beef semitendinosus muscles. No difference (P>0.05) occurred between the predicted and observed cooking times. Moisture loss generally was underestimated because of the lack of compensation for dripped moisture loss during cooking. Our model is suitable for predicting cooking times.     

Application of the micrometeorological mass balance method to the determination of ammonia loss from a grazed sward

The micrometeorological mass balance method has been assessed with a view to its use in the determination of ammonia (NH₃) loss from grazed swards. The method involves the measurement of wind speed and the concentration of NH₃ in air at different heights above the sward at its windward boundary and a position leeward of the grazed area. The flux of NH₃ is calculated from these measurements and a continuous record of wind direction. Quantitative recovery of NH₃ from air flows up to 10 litre min^?1 was achieved using a simple trap containing dilute orthophosphoric acid and a gas dispersion tube. Wind speed measured at a height of 0.25 m at six different positions above a previously grazed sward varied by <2%. The NH₃ concentration at the same positions was affected by the distance between the windward edge of the sward and the sampling position (i.e. the fetch) and by heterogeneity in the distribution of sources of NH₃ (urine- or dung-affected areas). However, the normalised horizontal flux through 0.25 m (wind speedXNH₃ concentration/fetch) varied by less than ±8.1% probably due to mixing through fluctuations in wind direction (approximately ±30° on the mean) as air passed over the sources of NH₃ during each measurement period. Plots of wind speed or NH₃ concentration versus logarithm of height indicated that each approximated a linear relationship. This facilitated the calculation of the NH₃ flux per unit land area and reduced the total error to about 10%. The total loss of NH₃ derived by summing losses during individual sampling intervals of 2 to 18 h within a 24 h period was essentially the same as that derived by averaging wind speeds and NH₃ concentrations measured continuously over the same 24 h period. The flux of NH₃ from a ryegrass sward grazed by yearling steers ranged from 0.01 to 0.14 kg N ha^?1 h^?1 during a 2 day grazing period within a 28 day rotation and during the 5 days following removal of animals. A pronounced diurnal variation was observed in the flux of NH₃, the maximum occurring between 13.00 and 20.00 hours on each day. Rainfall and low rates of evapotranspiration reduced the flux to <0.02 kg N h^?1 h^?1. The total loss of NH₃ during 28 days was 20.7 kg N ha^?1.     

连续流动法测定烟草中氨含量的改进方法

为了实现烟草中氨含量的快速检测,采用二氯异氰脲酸钠代替行业标准方法中使用的次氯酸钠,建立了一种新的烟草中氨含量的连续流动测定法。实验结果表明,该法重复测定的变异系数小于3%,回收率98.83%~101.97%,具有较好的重现性和准确性。t检测结果表明本法与行业标准法测试结果之间不存在显著性差异。