Color degradation kinetics of pineapple puree during thermal processing

Improvement of color, as a quality attribute of processed pineapple puree, has been made possible by the increase in knowledge of kinetic of color change. The kinetics of color degradation of pineapple puree were investigated during heat treatment at 70-110 °C in order to cover the temperature range that used in preheat and sterilization of commercial aseptic pineapple puree. Color changes associated with heat-treated puree were monitored using Hunter colorimeter (L, a, b, total color difference—ΔE) and Browning index (A₄₂₀). The changes in L and b values fitted well to the first-order kinetic model while ΔE, a value, and Browning index followed the zero-order kinetic. The dependence of the rate constant on temperature was represented by an Arrhenius equation. The results suggested that ΔE and lightness, based on activation energy, were the most sensitive measures of color change at temperature range 70-90 and 95-110 °C, respectively.     

压力条件对不同尺寸条缝喷嘴换热的影响

以条缝喷嘴型的上下冲击式速冻机内部流场为研究对象,利用计算流体力学(Computational Fluid Dynamics,CFD)数值模拟和实地测试,对比了3种尺寸的喷嘴结构分别在不同压力(190,170,160Pa)条件下3种不同尺寸的喷嘴结构,条件下内部流场及换热特性的区别。结果表明:条缝喷嘴T_0在190Pa条件下的出口风速、努塞尔特数、均匀性比在170Pa条件下的理想,同时横流风速也低。条缝喷嘴T_1在170Pa条件下的出口风速、努塞尔特数、均匀性比在160Pa条件下的理想,但横流风速反而增加。条缝喷嘴T_2与T_0在同一入口压力下相比,只有横流风速较低。在换热强度方面,当入口压力为190Pa时,条缝喷嘴T_1所对应的钢带表面的局部努塞尔特数最大,而T_0与T_1的平均努塞尔特数相差不大。在换热均匀度方面,条缝喷嘴T_0在入口压力为190Pa时的不均匀度最低,换热最均匀。故当空气的质量流量相同时,入口压力为190Pa时所对应的条缝喷嘴T_0能更好地提升换热效率,有利于提升食品的冻结速率。     

两类显示器色光性能的对比测试

为了明晰高端应用的CRT和LCD显示器的色光特性,测试分析了两类各一个显示屏幕在暗室和明室环境中色光的位置均匀性、光亮度和色度、CIE_xy色品域,及其随水平观测角度的变化等特性。实验结果表明：两个显示器在暗室环境中,7个不同色光在屏幕9个位置面法线方向的颜色标准偏差在1.8以内,明室中会增大为3.0以内。明室、暗室中,色光的性能随水平观测角而变化;面法线方向上,LCD显示器的光亮度及色品域均大于CRT显示器;随着观测方向与屏幕面法线方向夹角的增加,均表现为光亮度减小、颜色变化增大,在可接受的颜色差异内,CRT显示器形成面法线水平方向两侧约±25°角的可视范围,而LCD的情况降低为±20°左右;此外,该可视角度内,两个显示器各自的色品域几乎保持不变。     

1036MW燃煤机组锅炉制粉系统煤种适应性研究

目前国内电煤价格节节攀高,燃煤发电厂为了降低成本,燃用偏离设计煤种的劣质煤,导致锅炉制粉系统出力受限,安全、经济性能降低.在试验的基础上分析了1 036 MW火电机组制粉系统对煤种的适应性,确定了磨煤机在燃用不同煤种时的最大出力,针对实际情况对磨煤机风煤比进行了调整,并提出应定期标定一次风量及在计算磨煤机最小运行风量时,要考虑燃煤水份、粘度等参数的建议.     

改造激冷辊水系统提高粗化膜表面状态均匀性

双向拉伸聚丙烯薄膜生产线激冷辊水温波动是导致粗化膜粗糙度及雾度不均匀性的主要原因.通过薄膜生产线激冷辊水系统改造,激冷辊水温波动幅度控制在0.5～0.7℃之间,改善了粗化薄膜粗糙度及雾度的均匀性.     

膨胀梗粒在烟支中的有效利用率及分布均匀性

利用乙醇悬浮法测定了膨胀梗粒在烟丝中的掺配比例为5%,10%,15%和20%时的有效利用率及其在烟支中的分布均匀性,结果表明:在试验范围内,①在掺配比例20%以内,膨胀梗粒在烟支中含量的变异系数小于5%,说明其在烟支中分布均匀性较好;②随着膨胀梗粒在卷烟配方中掺配比例的增加,其在卷烟中含量的标准偏差增大,即随着掺配比例的增加,膨胀梗粒在烟支中的分布均匀性呈下降趋势;③随着膨胀梗粒在卷烟配方中掺配比例的增加,其有效利用率降低。     

双发射天线对混响室场性能影响的数值分析

提出了双天线激励混响室的方法,研究了双天线激励对混响室场性能的影响。分析了双天线改善混响室场均匀性的原理,对单天线激励下的混响室模型以及处于不同位置的双天线激励下的混响室模型进行了仿真计算,从场均匀性和场强两个方面研究了双天线对混响室场性能的影响,对双天线影响场强的机理进行了分析。研究表明:采用双天线激励改善了混响室工作区域的场均匀性;采用双天线可以降低对功率放大器的要求,降低大型混响室测试成本。最后对双发射天线在大型混响室中的应用进行了探讨和展望。     

Tetrazolium Staining,Mitochondria, and Barley Quality

Triphenyl tetrazolium chloride (TTC) staining of individual isolated barley aleurone layers was carried out under aseptic conditions and the amount of formazan generated under a standardized incubation period was quantified. The nature of the tests minimized or excluded the influences of grain damage, ageing or contaminating microorganisms. Embryos from selected Triumph barley grains, having intensely or poorly staining aleurone layers, were grown on to maturity. Collected grain was analysed and embryos from the highest‐staining progeny from the high‐staining aleurone line and the lowest‐staining progeny of the low‐staining aleurone line were grown on to yield grain of the second selected generations. Aleurone layers of the high‐staining line continued to stain intensely, respired strongly, and generated large amounts of α‐amylase in response to gibberellic acid and embryos from these grains respired and grew vigorously, as did whole grains. In contrast, the aleurone layers of grains from the low‐staining line continued to stain poorly and respired weakly, generated little α‐amylase in response to gibberellic acid, the embryos respired slowly and lacked vigour and, like the whole grains, grew poorly. It is proposed that these results are the consequence of the selection procedure separating lines with superior and inferior mitochondria. If this apparently novel approach using TTC staining is confirmed as being valid, it opens a new way for plant breeders to select for more vigorous cereal lines.     

混合絮凝及周进周出沉淀池工艺设计

旺隆污水处理厂二期工程中,一级处理采用混合、絮凝、沉淀池工艺。设计采用机械混合、网格反应和周进周出矩形沉淀池的优化和改良方案,能够明显改善对悬浮物及胶体有机物的处理效果,减少后续构筑物的处理负荷和处理费用。     

三偏心蝶阀密封应力均匀性的数值仿真

本文对三偏心蝶阀密封面接触问题进行了非线性有限元分析。在密封副不干涉的基础上,对三偏心蝶阀密封副的接触密封进行了静态数值仿真;并重点阐明了轴向偏心、径向偏心、角偏心对密封应力分布均匀性的影响。研究对降低阀门的关闭力矩,进一步提高三偏心蝶阀的使用寿命有指导意义。