石墨表面改性对MgO-C耐火材料抗氧化性能的改善(英文)

石墨常作为传统MgO-C耐火材料的碳源。石墨在经酸化剂改性后,可在表面产生负电荷,从而增强铝相的涂覆率。从弥散度和氧化性能方面对改性后的石墨与天然石墨进行了比较。首先,将经过和未经过表面改性的石墨颗粒分别添加至酸化剂Al(NO3)3悬浮液中,并在室温下过滤,得到改性后的石墨。试验表明:改性后的石墨较天然石墨具有更好的弥散性,其Al相涂覆率得到了增强。在氧化性能方面,优化后的石墨没有Al涂层时,在900°C热处理时与空气充分氧化;而有Al涂层时,则在900°C时开始氧化,在1000°C时充分氧化,并分别变为灰色和白色。可见,由于Al涂层在石墨表面均匀覆盖,Al相涂覆率的提高增强了石墨的抗氧化性能。     

Stability and robustness of discrete event dynamic systems

In this paper, the general concepts of stability of discrete event dynamic systems are defined and investigated. We present the stability in the sense of Lyapunov with resiliency, by incorporating the Lyapunov stability concepts (Michel and Miller 1977, Passino et al. 1994) with the concept of stability in the sense of error recovery (Ozveren and Willsky 1991a). We also provide algorithms for verifying stability and obtaining the domain of attraction. Upon the proposed stability concepts, we address the issue of robust stability and stabilizability. We assume that the plant G is not known exactly but we only know that it belongs to a set of models. In robust stability, we analyse the stability of the common invariant states set of all possible plant models. Then we derive the necessary and sufficient conditions for the robust stabilizability, i.e. the existence of a supervisor which makes the uncertain system robustly stable.     

EFFECT OF FAR-INFRARED HEATER ON THE PHYSICOCHEMICAL CHARACTERISTICS OF GREEN TEA DURING PROCESSING

ABSTRACT

The green tea leaves (Camellia sinensis var. sinensis) were irradiated by a far‐infrared (FIR) heater during the roasting and drying step, resulting in three different treatments produced. Green tea was extracted by soaking the leaves in water, and the components were analyzed. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, increased total phenolic contents of green tea from 116.30 to 171.77 mg/g, and total flavanol contents from 17.54 to 24.76 mg/g, compared with the non‐irradiated control. Ascorbic acid contents also increased from 3.07 to 4.20 mg/g. The amounts of epicatechin gallate and epigallocatechin gallate were significantly increased from 2.41 to 4.59 mg/mL and 20.61 to 28.54 mg/mL, respectively, compared with the non‐irradiated control. FIR irradiation increased Nitrite Scavenging Ability of green tea at pH 3.0 and pH 4.2, while there was no significant difference at pH 6.0. Sweetness, umami and aroma of green tea were enhanced by FIR irradiation, while bitterness and astringency were decreased compared with those of the control. These results show that FIR heating during the green tea process affected the chemical properties of green tea, and the FIR heater can be applied to increase the physicochemical qualities of green tea.

PRACTICAL APPLICATIONS

Green tea, a widely consumed drink, has received much attention because of the beneficial biological effects attributable to its excellent antioxidant activity. In this article, a far‐infrared (FIR)‐heater for industrial application was used during the processing of green tea leaves, and the chemical characteristics and quality of FIR‐treated green tea were determined. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, significantly increased phenolic, flavanol, ascorbic acid, epicatechin gallate, epigallocatechin gallate contents and nitrite‐scavenging activity compared with non‐irradiated control. Sensory evaluation also showed a positive effect of FIR irradiation. The results indicated that FIR heater could be easily applied to increase the quality of green tea in the processing line.     

Evaluation of the Quality of Cookies Supplemented with Distillers' Dried Grain Flours

Distillers' dried gram (DDG) samples collected from various distillers differed in protein, ash, fat, and fiber contents, and colors. When distiller's dried gram flour (DDGF) was mixed with wheat flour at a 15 or 25% (w/w) replacement level for making sugar cookies, the replacement could decrease the width and thickness and darken the color of sugar cookies. DDGF was found suitable as a supplement for preparing dark-colored cookies to enrich their protein and fiber contents. Sensory evaluations of 15% DDGF supplemented bar, spice and chocolate cookies showed that they were all acceptable.     

基于高通量计算的成形过程分析

目的介绍一种来自材料基因组计划的方法,由高通量计算、高通量实验与数据管理构成,并以45#钢为例,介绍高通量计算与高通量实验的优势。方法先以模拟软件与理论结合,预测研发方向,再设计合适高通量的实验方案,最后将所得数据建立数据库,方便管理。以45#大型钢铸锭为例,以COMSOL软件模拟3种不同钢锭成形过程,设计实验方案,记录过程参数,并记录于数据库中。结果 COMSOL软件在高通量计算中扮演重要角色,其强大的耦合功能让模拟精度更高,各项参数也较为准确。透过模拟得知,约2.9 h后,20 t钢锭凝固厚度最厚达约500 mm,此时将中间液芯挤出,可减少划痕等缺陷的产生,并将凝固过程的缺陷挤出。结论材料基因组计划在材料研发的进程中能起到较大的指导作用,因此在国家支持下国内已有多个项目开展,将此研究方法用于传统浇铸工业的步骤中具有一定的推广价值。     

Biopolymer-stabilized emulsions on the basis of interactions between β -lactoglobulin and ι -carrageenan

ι-Carrageenan and β-lactoglobulin (β-lg) stabilized oil-in-water (O/W) emulsions, which can be used for the oral administration of bioactive but environmentally sensitive ingredients, have been successfully prepared. The effects of protein/polysaccharide ratios, total biopolymer concentration, environmental stress (thermal processing and sonication), and pH on the complex formation between ι-carrageenan and β-lactoglobulin have been investigated. We found that β-lactoglobulin andι-carrageenan stabilized emulsions can be formed at pH values of 6.0, 4.0, and 3.4. However, the microstructures of emulsions stabilized by β-lactoglobulin and ι-carrageenan was identified by optical microscopy, and it indicated that the emulsion prepared at pH 6.0 flocculated more extensively, while its hydrodynamic radius was much bigger than those prepared at pH 4.0 and 3.4. Regarding rheological properties, the emulsion of pH 6.0 showed a more solid-like behavior but with a lower viscosity than those of pH 4.0 and 3.4. The optimum concentration ranges for β-lg andι-carrageenan to form stable emulsions at pH 4.0 and 3.4 were 0.3wt-%―0.6wt-% and 0.4wt-%―0.7wt-%, respectively.     

Development of an axial-type fan with an optimization method

An axial-type fan that operates at a relative total pressure of 671Pa and a static pressure of 560Pa with a flowrate of 416.6m³/min is developed using an optimization technique based on the gradient method. Prior to the optimization of the fan blade, a three-dimensional axial-type fan blade is designed based on the free-vortex method along the radial direction. Twelve design variables are applied to the optimization of the rotor blade, and one design variable is selected for optimizing a stator which is located behind the rotor to support a fan-driving motor. The total and static pressure are applied to the restriction condition with the operating flowrate on the design point, and the efficiency is chosen as the response variable to be maximized. Through these procedures, an initial axial-fan blade designed by the free vortex method is modified to increase the efficiency with a satisfactory operating condition. The optimized fan is tested and compared with the performance obtained with the same class fan to figure out the optimization effect. The test results show that the optimized fan not only satisfies the restriction conditions but also operates at the same efficiency even though the tip clearance of the optimized fan is greater than 30%. The experimental and numerical tests show that this optimization method can improve the efficiency and operating pressures on axial-type fans.     

原位增韧SiC-YAG复相陶瓷的致密化

以β－ＳｉＣ粉加入少量作为晶种的α－ＳｉＣ为起始原料,通过高温热处理过程中的相变和长柱状晶粒生长来制备原位增韧ＳｉＣ基复相陶瓷;调整埋烧工艺控制高温热处理过程中液相挥发和保持稳定的化学计量比,以保证上全部晶化为ＹＡＧ相,着重解决了长柱状晶粒生长过程中的致密化。发现在完全形成紧密的网络状结构之前,长柱状晶粒的形成可能延缓致密化速率,但不会由此中止致密化过程。通过调整热处理条件,制备得到了完全致密化（