挤压加工参数对重组米生产过程及产品膨胀度的影响

为了考察重组米生产过程中挤压加工变量对几种系统参数与产品膨胀度的影响,试验以杂交籼米（9?718品种）为原料,利用响应面模型,以螺杆转速、进料速度、进料含水率以及末端机筒温度为输入变量,以挤压系统参数（物料温度、模头压强、扭矩、比机械能和产品含水率）和重组米膨胀度为响应变量,探索在重组米生产过程中加工变量与系统参数及产品膨胀度的关系。结果表明,压强、比机械能和产品膨胀度都受到4个挤压变量的显著影响,但是物料温度受进料速度影响不显著,马达扭矩受末端机筒温度影响不显著,产品含水率仅受进料含水率的显著影响。比机械能与螺杆转速正相关,与进料速度、进料含水率和末端机筒温度负相关。所得二次回归模型均拟合良好,建立的挤压数学模型可应用于重组米生产,为重组米工业化生产的过程预测和产品性质预测提供参考。     

高水分大豆蛋白组织化生产工艺和机理分析

以低温豆粕为原料，应用带冷却工艺的双螺杆挤压实验室工作站，开发出高水分组织化大豆蛋白产品的生产工艺；分析了螺杆转速、物料湿度、喂料速度和机筒温度等操作参数对产品质构和色泽的影响规律；利用扫描电镜对高水分组织化大豆蛋白产品的微观结构进行了观察和分析。结果表明：机筒温度在150℃左右时，产品具有较好的组织化度、色泽及口感；随着物料水分的增加，产品的组织化度、粘着性和明度指数逐渐增加，而硬度和咀嚼度逐渐降低；随着螺杆转速的增加，产品的组织化度、硬度、粘着性和咀嚼度均有增加的趋势；喂料速度对产品的表观形态影响较大，喂料速度较大时，产品表观粗糙、组织化度降低。单因素实验优选的操作参数为：机筒温度145℃～155℃，物料湿度45％～50％，螺杆转速90～160 r/min，喂料速度20～40 g/min。结合对生产工艺和产品微观结构分析，提出了高水分组织化大豆蛋白产品形成过程的“膜状气腔”理论假设，以供讨论和指导生产实践。     

水产沉性粒饲料挤压蒸煮工艺对其物性影响

选用双螺杆挤压机对水产全价配合原料进行挤压熟化,以沉性水产硬颗粒饲料理化特性(膨化度、堆积密度、糊化度、耐久性和水中稳定性)为重要指标,采用表面响应分析法研究了物料水分含量(25～35%)、套筒温度(90～150℃)和螺杆转速(80～100 r/min)对其挤压工艺和饲料理化特性的影响规律,SEM分析其微观结构。结果表明：物料水分、套筒温度和螺杆转速均显著影响饲料的理化特性。中高物料水分和套筒温度及低螺杆转速时,才能获得理想的沉性高熟化水产颗粒饲料,其理化特性具有低膨化度(1.15),高堆积密度(754.7 g/L)、糊化度(882.3 g/kg)、耐久性(96.6%)和水中稳定性(89.1%)。SEM分析显示优化条件(物料水分30%,套筒温度120℃,螺杆转速80 r/min)下生产的颗粒饲料结构光滑质密。     

鸡肉-大米膨化食品双螺杆挤压工艺参数的优化研究

以鲜鸡肉和大米为原料，对双螺杆挤压工艺条件进行研究，以期开发出新型鸡肉挤压膨化休闲食品，提高鸡肉的附加值。试验采用可旋转中心组合设计，综合考查物料湿度(X₁)、机筒温度(X₂)和螺杆转速(X₃)三个变量对糊化率(Y)的影响。在此基础上由试验数据推导出描述糊化率的二次回归模型，并对变量进行响应面分析，得出最佳挤压工艺条件为：物料湿度35％、机筒温度123℃、螺杆转速220 r/min。     

挤压玉米粉制备高麦芽糖浆工艺优化

为缩短超高麦芽糖浆的生产周期、节约能源,该文系统地研究了挤压玉米粉作预处理后生产高麦芽糖浆的工艺,分析了机筒温度、螺杆转速、模孔直径及物料水分与麦芽糖含量、糖浆收率的关系。结果表明:挤压工艺的因素排序为机筒温度>物料含水率>螺杆转速>模孔直径;最佳挤压条件为:59℃、23%、200r/min、6mm,液化10min,糖化8h,经高效液相色谱分析,所制备的糖浆中麦芽糖质量分数为69.19%,糖浆收率可达100.62%,研究结果可为工业化生产麦芽糖提供数据参考。     

挤压参数对组织化大豆蛋白持水性的影响

试验以脱脂低温豆粕为原料,以德国布拉本德双螺杆挤压实验室工作站（DSE-25型）为设备,研究了挤压温度、物料含水率以及螺杆构型对产品持水性的影响。结果表明：物料含水率和螺杆构型对产品持水率有极显著影响（p〈0.01）;挤压温度对产品的持水率没有显著影响;挤压温度、物料含水率和螺杆构型对产品吸水率有极显著影响（p〈0.01）。影响产品持水率程度的大小顺序为物料含水率、螺杆构型、挤压温度;影响产品吸水率程度的大小顺序为螺杆构型、挤压温度、物料含水率。产品吸水率随着挤压温度的升高而增加。产品的持水率和吸水率随着物料含水率的提高先增加,随后略有降低。与配备输送元件的构型相比,配备反向元件、齿型盘和捏合块的构型显著增加了产品的持水性。工艺参数和螺杆构型对大豆组织化蛋白的吸水率的影响相对较大,对持水率影响相对较小。产品良好的组织结构是提高产品持水性的必要条件。     

不同挤压参数对大豆粕蛋白质结构的影响

该文系统研究了油脂提取前挤压膨化预处理工艺对大豆粕蛋白质表面疏水性、游离巯基含量的影响，分析了物料水分、膨化温度、δ段长度、模孔长度、螺杆转速等不同挤压参数与蛋白质结构变化的关系，建立了挤压参数与粕蛋白质游离巯基含量关系的量化模型。结果表明：低物料水分、低膨化温度、短模孔可以减少挤压膨化预处理工艺过程中蛋白质结构的破坏程度。相反，高物料水分、高温挤压膨化时，会加剧蛋白质分子内部疏水基的暴露和蛋白质的交联。在此基础上改进的挤压膨化预处理工艺更有利于蛋白质结构的改善。     

脱胚玉米啤酒辅料的挤压蒸煮系统参数对其糖化过程的影响

该文通过实验室试验,研究了作啤酒辅料的脱胚玉米挤压蒸煮系统诸参数(模孔孔径、套筒温度、物料含水率、螺杆转速和模板内表面至螺杆末端端面的距离)，对醪液的主要考察指标（麦汁的过滤速度、碘值、浸出物收得率）的影响规律. 研究表明，挤压蒸煮脱胚玉米可以作啤酒辅料，其醪液的淀粉在糖化过程中被降解得彻底，淀粉的利用率较高。     

双螺杆二次挤压法制备方便米饭的工艺研究

该文采用可旋转中心组合设计,综合考查机筒温度、物料湿度和螺杆转速三个变量对挤压方便米饭复水率的影响,推导出描述复水率的二次回归模型,并对变量进行响应面分析,得出最佳工艺条件为:机筒温度为120℃、物料湿度为33%,螺杆转速为200 r/min.在该条件下制得的方便米饭复水3 min后,复水率达285%,硬度和弹性值都达到原料籼米米饭的水平.     

香菇双螺杆挤压膨化机的设计与试验

针对现有双螺杆挤压膨化设备生产香菇膨化产品时存在物料堵塞、预熟度低、作业参数缺失等问题而导致生产的产品膨化率低、吸水性差、硬度高等缺陷,该研究设计了一种香菇双螺杆挤压膨化设备,并对设备中的关键部件喂料搅拌防堵装置、预熟调质装置与双螺杆结构参数进行了设计与确定。同时,为探究设备中的作业参数对产品膨化性能的影响,研究了设备的螺杆转速、膨化温度、物料含水率对产品的膨化率、硬度、脆度、吸水性的影响。结果表明:影响膨化率的显著性顺序依次为螺杆转速、物料含水率、膨化温度;影响硬度的显著性顺序依次为螺杆转速、膨化温度、物料含水率;影响脆度的显著性顺序依次为膨化温度、物料含水率、螺杆转速;影响吸水性的显著性顺序依次为膨化温度、物料含水率、螺杆转速。其次,结合各因素交互作用的影响规律与目标优化结果,得出设备的最佳作业参数为:螺杆转速167.23r/min,膨化温度151.68℃,物料含水率16.83%,此时,产品的膨化率、硬度、脆度、吸水性分别为4.04%、18.61N、-8.46mm/cm^2、313.86%。将优化后的参数值在设备中进行了生产性应用,得到生产值与优化值的误差均小于4%,最大生产率为165 kg/h。与扬州大学机械工程学院实验室内的现有设备相比,在提高物料送料的连续性与调质熟化度的基础上,膨化率提高了25.00%,硬度降低了48.21%、脆度提升了40.55%、吸水性提高了62.35%。因此,该机的设计可为香菇膨化产品的开发提供了一种较为成熟的技术装备。     

Clarity performance variables of polluted water

Clarity performance variables of polluted water at different conditions of bioflocculation were studied through a set of laboratory experiments using the shake flask technique. The study was based on the relationship between physical properties of developed bioflocs and some environmental parameters. The physical properties included floc sizes and numbers, solution turbidity and the ratio of unsettled floc numbers (ufn) to total floc numbers (tfn) and settled floc volume (sfv) to total floc volume (tfv). The environmental parameters were the application of different sources of wastewaters, using of filamentous, floc forming, and natural bacteria, mixed at different speeds. The results indicated that various sources of wastewater mixed at different speeds, in the presence of various categories of bacteria allowed the development of flocs possessing a wide range of physical properties. Clarity performance was directly proportional with the ratio of sfv/tfv and inversely proportional with ufn/tfn. These ratios, on one hand, and with the floc sizes, numbers and solution turbidity, on the other hand, were discussed from the view point of their importance in clarity performance efficiency measurement of wastewater.     

用于灌溉耕地制图的特征变量优选

灌溉耕地制图可以为粮食安全、水资源管理和气候变化等相关研究提供数据基础.构建和选择表征灌溉耕地信息的特征变量是灌溉耕地制图最重要的环节之一.该研究选择有良好灌溉信息数据基础的美国内布拉斯加州为研究区,基于已有灌溉耕地空间分布图和灌溉信息数据,提取灌溉耕地和雨养耕地的样本,计算了样本的4类82个特征变量,利用随机森林对比...     

Spatial analysis of categorical soil variables with the wavelet transform

This paper describes a wavelet transform for the analysis of categorical (multistate) soil variables, i.e. ones (such as profile classes) that have two or more discrete states. The states are transformed to a continuous variable by a mapping which is optimized by scale and location to highlight local variation. The method is illustrated with data from a transect across a gilgai landscape in Australia. A categorical variable on relief, with three states, was recorded from the sample sites, from which soil cores had also been collected and analysed. The wavelet analysis showed a transient feature of the variation at scales up to 32 m. There was an interval where the characteristic alternation of depressions with the level plain was interrupted. The variation at scale 64 m appeared to be non-stationary. The relief was more variable on one side of a change point than it was on the other. This complex variation of relief was matched by that of the electrical conductivity of the soil, most strongly at the 64-m scale. The periodicity of conductivity, and the strength of its correlation with relief, were also different either side of the change point identified in the analysis of relief alone. Conductivity also showed similar transient features to relief. Evidently the wavelet transform can be used to elucidate the variation of categorical soil variables. The information from such an analysis is likely to be useful for planning surveys of the soil to measure continuous variables by sampling and laboratory analysis.     

Comparison of spatial variables over subregions using a block bootstrap

In environmental and agricultural studies, it is often of interestto compare spatial variables across different regions. Traditional statistical tools that assume independent samples are inadequate because of potential spatial correlations. In this article, spatial dependence is accounted for by a random field model, and a non parametric test is developed to compare the overall distributions of variables in two neighboring regions. Sampling distribution of the test statistic is estimated by a spatial block bootstrap. For illustration, the procedure is applied to study root-lesion nematode populations on a production farm in Wisconsin. Choices of the bootstrap block size are investigated via a simulation study and results of the test are compared to traditional approaches.     

Interactions between microclimatic variables and the soil microbial biomass

Summary Soil moisture, temperature, microbial substrate-induced respiration and basal respiration were monitored in two plots in an agricultural field from April 30 to September 25, 1987, and in a further two plots from May 26 to August 27, 1988. An attempt to relate biological variables to microclimatic variables was made through the use of correlation analysis. The microbial substrate-induced and basal respiration were both strongly positively correlated with the soil moisture content, and to a lesser extent positively related to soil temperature, especially when partial correlation was used to control for variation in soil moisture. Short-term changes in substrate-induced and basal respiration were correlated with changes in soil moisture but were largely independent of soil temperature. The ratio of basal to substrate-induced respiration (indicating the respiration: biomass ratio and therefore ecosystem stability or persistence) was negatively associated with the soil moisture content and in some instances with soil temperature when partial correlation analysis (correcting for soil moisture variation) was used. This suggests that the climatic conditions which contributed to the lowest ecosystem stability were low temperature, low moisture conditions.     

气象要素时间分辨率对参考作物蒸散估算的影响

参考作物蒸散(reference evapotranspiration,ET0)的准确估算是农业水资源合理利用的重要环节。为了明确气象要素不同时间分辨率对参考作物蒸散估算的影响,该文基于寿县国家气候观象台2007-2013年观测资料,将1min时间分辨率数据平均值作为真实值,分析了10、20、30、40、60 min、4次/d(02:00、08:00、14:00、20:00)和3次/d(08:00、14:00、20:00)这7种不同时间分辨率对逐日气温、风速、太阳辐射、相对湿度和日、月及年参考作物蒸散(ET0)估算的误差情况。结果表明:ET0和气象要素的误差整体上随时间分辨率降低而增大。4个气象因子中,日平均风速估算受时间分辨率变化的影响最显著,误差最大;其次是太阳辐射。逐日ET0估算在7种时间分辨率的平均绝对相对误差(mean absolute relative error,MAPE)依次为0.53%、1.01%、1.38%、1.72%、2.46%、4.72%和6.14%,表明10至60min时间分辨率的估算效果相较3次/d和4次/d有明显改善。10至40 min的绝对误差超过95%都在-0.20~0.20 mm/d区间内,误差较小且集中度高;太阳辐射时间分辨率变化对ET0估算误差贡献最大,其次是风速,这主要是由于两个要素本身对分辨率较敏感且分别是ET0辐射项和动力项的主要组成因子。时间分辨率的变化对累计后长时间尺度ET0的影响较小,月和年ET0的误差明显小于逐日ET0,月ET0在7种时间分辨率的MAPE值依次为0.13%、0.21%、0.27%、0.40%、0.50%、1.18%和1.48%;各年ET0相对误差(relative error,PE)的绝对值多数均小于0.50%。     

Physicochemical variables affecting the rheology and microstructure of rennet casein gels

The rheology and microstructure of a rennet casein system were studied in the pH range from 5.8 to 12.0 during cooling from 80 to 5 degrees C at four cooling rates: 0.5, 0.1, 0.05, and 0.025 degrees C/min. A dramatic increase in storage modulus with pH was observed during cooling at a fixed cooling rate. Continuous networks were formed for gels at pH 7.2 and above, while a discontinuous network was observed for gels below pH 6.5. The monotonic increase in storage modulus with pH could be correlated to the number of net (negative) charges and the strength of the hydrophobic interactions. At a higher pH, the protein micelles were larger due to weaker hydrophobic interactions and stronger repulsive electrostatic interactions resulting from more charges. When these protein micelles aggregated into flocs during cooling, the flocs had similar sizes at different pH values but a smaller fractal dimension at a higher pH. Consequently, for systems of the same protein and salt concentrations, more flocs were present in the gels at a higher pH, which subsequently generated more cross-links and a higher storage modulus. The pH also determined how the cooling rate affected the gel properties. At pH 5.8 and 6.5, the gels were firmest at the fastest cooling schedule, and the cooling rate did not show a trend in affecting the gel strength at the other three rates. On the other hand, a slower cooling rate generated a firmer gel at pH 7.2 and 12.0. The analysis of casein interactions suggests that the cooling rate affected the casein floc size only when repulsive interactions enabled a slow flocculation (at higher pH values) comparable with temperature change rates during cooling. For rennet casein gels of pH within the range of processed cheese products (pH 5.8 and 6.5), particle or cluster rearrangements created more uniform networks for gels cooled at slower schedules and weakened the structure.     

Effects of environmental and biological variables on the toxicity of mercuric chloride

This study evaluated the effects of environmental and biological variables on the toxicity (LC₅₀) of mercuric chloride on the fish Notopterus notopterus. The results reveal that the change in temperature, dissolved oxygen, pH and fish size in experiments is highly significant both at 1 and 5% levels except in size, where it is insignificant at 1% level.