EFFECT OF HOT WATER IMMERSION ON PEEL COLOR OF PEARS AND ON WHITE ROT CAUSED BY BOTRYOSPHAERIA BERENGERIANA

Abstract The effectiveness of hot water immersion (HWI) on peel color and the control of white rot caused by Botryosphaeria berengeriana on wound-inoculated European pears, cv. La-France, were investigated. After HWI at 40, 45, 48, 50, 52 and 54C for varying immersion periods, the pears were held at 20C, ≥ 90% RH (simulated retail conditions). The peel color (L*, a*, b*) was determined before and after HWI treatment. The dominant role of L* suggested that peel darkening was the major factor in color change of the HWI treated pears. The L* value of 54 was judged as the border line for acceptability and less than 51 resulted in browning. Similarly the critical points for a*, b*, chroma, hue and ΔE* were found to be −6, 34, 35, 100, and 8, respectively. Disease incidence recorded 7 days after treatment revealed that High Temperature Short Time (HTST) treatment of 54C for 3 min reduced incidence about 85% with good retention of color. Both temperature and immersion period are to be carefully selected to prolong shelf-life and retain the peel color quality of 'La-France'pears.     

基于平面应变试验的修正塑性功硬化软化模型

以改良型平面应变仪为基础,通过一系列平面应变和三轴压缩试验,对砂土的应力应变特性进行了研究,推导出以修正塑性功为硬化参数的本构关系。改良型平面应变仪较好地解决了加载面的摩擦及约束问题,能保证ε2的控制精度,并采用了合理的变形量测整理方法。本文提出的弹塑性模型仍以传统塑性理论为框架,其弹性特性、破坏准则、硬化参数及塑性势等均直接从试验曲线推导,以修正塑性功为硬化参数的硬化准则函数能反映硬化及软化的全过程曲线,并从试验结果推导了非关联流动准则塑性势函数。该模型结构较为清晰,参数选取规范,模型验证表明计算结果与试验结果较为吻合。     

Thermal Transitions of Myosins/Subfragments from Black Marlin (Makaira mazara) Ordinary and Dark Muscles

Thermal transitions were studied by means of differential scanning calorimetry (DSC) and a spectrophotometric method. Three endothermic peaks (40, 43, 50°C: ordinary muscle; 46, 54, 62°C: dark muscle) were observed in DSC thermograms of both myosins. Thermograms of S-l fragments showed one peak (41°C: ordinary muscle, 43°C: dark muscle). But ordinary and dark muscle rod fragments gave two peaks (41, 62°C) and one peak (58°C), respectively. The spectrophotometric results also showed two thermal transitions for both myosins and one transition for their S-1 fragments. However, the rod from ordinary muscle myosin had two transitions, whereas that from dark muscle myosin had one transition.     

Rheological Properties of Heat-Induced Ovalbumin Gels Prepared by Two-step and One-step Heating Methods

Ovalbumin gave a transparent solution, transparent gel, or opaque gel on heating at low ionic strength, but a turbid gel, or turbid suspension at high ionic strength (one-step heating). The ovalbumin solution, once heated at low ionic strength, gave a transparent gel with a second heating at high ionic strength (two-step heating). Textural parameters of hardness and adhesiveness, viscoelastic parameters from creep curves, breaking energy and water-holding capacity of these gels were measured. Transparent gels by the one- or two-step heating were firm and elastic and had high water-holding capacity. Turbid gels by one-step heating were soft and less elastic and had low water-holding capacity. The relationship between gel properties and structure was discussed.     

Deamidation and Functional Properties of Food Proteins by the Treatment with Immobilized Chymotrypsin at Alkaline pH

Ovalbumin, lysozyme, 7S globulin, 11S globulin, and gluten were treated with immobilized chymotrypsin on controlled-pore glass at pH 10 at 20°C to improve their functional properties. Optimum pH of deamidation of ovalbumin by immobilized chymotrypsin was 10, where proteolysis was very limited. Deamidation percentages of ovalbumin, lysozyme, 7S globulin, 11S globulin, and gluten were 10.0, 8.4, 6.0, 5.0, and 8.0, respectively. SDS polyacrylamide gel electrophoretic patterns of ovalbumin and lysozyme showed no difference between untreated and treated proteins, while those of soy proteins and gluten showd that larger molecular weight fractions were dissociated into smaller molecular size fractions. Solubility of gluten was greatly improved at all pHs, 2-12. Both emulsifying and foaming properties of proteins were improved by treatment with immobilized chymotrypsin.     

Preparation and Characterization of Machinable Mica Glass-Ceramics by the Sol-Gel Process

The preparation and characterization of machinable mica glass-ceramics by the sol-gel process are described. The thermal behavior of the precursor and the optimum conditions for calcination, molding, and sintering are given. Physical, chemical, thermal, electrical, and mechanical properties are investigated, and the machinability of the ceramics is discussed.     

列车动力学模型时变环境参数自适应辨识

考虑列车制动性能与制动距离对列车安全的重要影响, 分析了列车运行的动力学特性, 构建了列车离散化制动模型,并针对影响列车制动性能的关键参数 — 钢轨粘着系数难以直接观测、随钢轨环境变化的特点, 提出基于滑动窗口与最大期望理论的轮轨粘着系数在线辨识算法. 首先, 依据数据特征确定滑动窗口位置与窗口尺寸; 然后, 构造列车动力学模型参数的条件数学期望, 并结合粒子滤波与粒子平滑算法以及贝叶斯理论, 估计预设模型参数下的列车运行状态; 在此基础上, 分析粘着系数的后验概率, 并极大化条件数学期望对模型参数预设进行优化更新, 进而实现模型真实参数的逐步逼近. 最后, 考虑雪地、隧道等场景下的粘着系数变化, 对本文方法进行了仿真验证, 并数值分析了粘着系数对制动距离的影响. 仿真结果表明本文算法可快速、准确地对粘着系数进行实时辨识, 掌握轮轨间实时粘着状态.     

采用修正塑性功硬化参数的双屈服面模型及应用

 首先对国内外双屈服面模型的发展进行回顾,指出土体模型中双屈服面概念的必要性和合理性。其次以平面应变试验结果为基础,直接推导出双屈服面模型各部分关系式,其中体积屈服面以塑性功为硬化参数,硬化函数与试验结果吻合程度较好,剪切屈服面以修正塑性功为硬化参数,满足了其与硬化面关系唯一性的要求,并可反映硬化–软化全过程。为使其能较方便地应用于数值计算方法,推导适用于双屈服面模型的弹塑性刚度矩阵。最后应用该模型对一高填土工程的变形进行计算,比较显示其与实测结果较为吻合。     

SEDIMENTATION OF PARTICLES IN NON-NEWTONIAN FLUIDS

The influence of non-Newtonian flow behavior on sedimentation velocity of particles is investigated using an approximate solution for the motion of an assemblage of solid spheres presented previously by the authors. It is theoretically predicted that the pseudoplaslicity decreases the sedimentation velocity and its reduction is pronounced at large voidage. The present theory is discussed using the available empirical correlations.