概念教学过程中的四个阶段

本文详细阐述了概念教学的四个阶段：（1）概念的引入；（2）概念的形成；（3）概念的巩固；（4）概念的深化和扩张。     

浅谈寒冷地区煤矿井筒保温防冻设计

指出了严寒地区煤矿进风井筒保温热负荷计算应注意的问题,将井筒供热设备热风炉和空气加热器的供热特点进行了比较。     

引气混凝土在海水中冻融循环后单轴强度试验研究

为研究冻融循环对中国北方寒冷地区混凝土结构产生的不利影响,利用混凝土快速冻融试验机,对海水中引气混凝土分别进行了0、100、200、300、400次快速冻融循环试验,并对冻融循环后的混凝土进行了单轴压力学性能试验。测得冻融循环后混凝土的质量损失,动弹性模量以及单轴抗压强度。根据试验结果,系统分析了冻融循环次数对混凝土单轴抗压强度的影响。结论表明:随冻融循环次数的增加,海水中引气混凝土的单轴强度逐渐降低,并具有一定规律性。可为北方寒冷地区着海工混凝土构筑物的抗冻设计提供理论依据。     

冷冻对CuCl_2溶液水团簇结构及CuCl_2与牛血清白蛋白相互作用的影响

为了考察CuCl_2溶液经冷冻作用后分子结构的改变及其生物功能,测定了其冷冻前后电导率和~(17)O-NMR化学位移和半峰宽的变化及随时间的变化规律,并进一步利用荧光光谱、紫外光谱、傅立叶红外光谱和圆二色光谱研究了与冷冻前后的CuCl_2作用后牛血清白蛋白(BSA)的构象变化。研究表明,CuCl_2溶液经冷冻处理后水团簇变小,这一过程可保持8 h左右。光谱实验结果表明冷冻处理后的CuCl_2与BSA的相互作用趋弱,对BSA的增色效应降低,配位诱导作用减小,对α-螺旋结构的氢键破坏作用减弱。红外曲线拟合结果显示与冷冻前后的CuCl_2作用后,BSA的α-螺旋结构由45.9%分别下降到31.8%和33.0%,β-折叠结构由21.1%分别增大到29.1%和26.5%,无规结构则都有所增多。CD谱结果与其一致。用冷冻处理水溶解BSA后与CuCl_2反应,同样具有使CuCl_2与BSA相互作用趋弱的效果,表明冷冻对CuCl_2与BSA相互作用变弱的效应是由于水的分子团簇结构变化引起的。     

Characterization of solid standards prepared by freeze‐drying

Solid standards prepared by freeze‐drying consistently showed a high degree of homogeneity. The freezing process, completed in fractions of a second, preserves the original homogeneous distribution of the dopants, and the subsequent sublimation step would minimize any disturbance. Compared to those prepared by conventional methods such as blending and spiking, freeze‐dried standards exhibited superior lateral distribution and better uniform depth distribution. There is, however, a concentration constraint for achieving homogeneity. At 5% doping, segregation was observed in both lateral and depth distribution. Many tungsten standards doped with 10–28 elements ranging from 10 to 200 ppm were successfully prepared and used as controls for a number of analytical techniques including glow discharge mass spectrometry (GDMS) and d.c.‐arc optical emission spectroscopy (OES). Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of Copper Chromite by Vaccum Freezing Drying Method and Its Catalytic Activity for Sulfuric Acid Decomposition

Iodine sulfur (IS) process is one of the most promising routes for massive and CO₂‐free hydrogen production. Among the three reactions IS process composed, decomposition of sulfuric acid is the most energy intensive step and has to be conducted in the presence of catalyst. In this work, copper chromite (CuCr₂O₄) was prepared, characterized, and used as the catalyst for sulfuric acid decomposition reaction. The co‐precipitation preparation method of CuCr₂O₄ which featured in vacuum freezing drying (VFD), was applied, and the main factors which influence the structure of CuCr₂O₄ such as pH values of the co‐precipitation solution and calcination temperature were investigated. Results showed that pH value affected the size of copper chromite granule, when pH was between 7 and 8, the size of prepared CuCr₂O₄ was in nanometer scale. Calcination temperature influenced the purity of the crystal. The samples were characterized by XRD, TEM and BET. The catalytic activity of CuCr₂O₄ prepared by VFD was evaluated and compared with CuCr₂O₄ prepared by usual co‐precipitation method and Pt/Al₂O₃. Results showed that the activity of CuCr₂O₄ was close to that of Pt catalyst, but apparently higher than that of CuCr₂O₄ prepared by usual method. In addition, it presents good stability in the 70 h test. Therefore, it was promising to be used in the sulfuric acid decomposition step of IS process.     

真空冷冻干燥设备的先进控制系统

对应用于宇航，军事，医药，营养保健食品等领域的真空冷冻干燥设备ＺＬＧ－３０等，用ＯＭＲＯＮ ＰＬＣ／４０Ｐ及单片机８０３２／ＥＵ８１８Ｐ１５构成手动，自动控制系统进行了硬件配置及软件设计；并针对不同冻干物料的工艺要求，采取ＤＲＡ算法和临界比例法两种自适应，自整定控制方法，解决了被控对象主控参数－温度的滞后等问题，实现稳定，可靠的自动化冻干过程。     

Morphological,mechanical, and in vitro cytocompatibility analysis of poly(vinyl alcohol)–silica glass hybrid scaffolds reinforced with cellulose nanocrystals

Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricated using the freeze-drying method. In this study, we develop molecular-level-based hybrid scaffolds with possible bioactivity behavior by adding silica sol–gel. The results showed a highly porous structure and a significant improvement in mechanical performance (stiffness) of hybrid scaffolds with an increased content of cellulose nanocrystals followed by the addition of silica-based bioactive glass. In vitro cell study with MC3T3-E1 cells on hybrid scaffolds for 1 and 3 days revealed good cell adhesion and growth. Thus, the obtained hybrid scaffold may be a competitive candidate for bone tissue engineering applications.     

加热方式对真空冷冻干燥热质传递机理的影响

1引言真空冷冻干燥（简称真空冻干）是多孔介质在低温低压下相变界面移动的耦合传热传质过程，其数学模型带有典型的非线性，难于精确求解［‘，2］。从应用上而言，真空冻干具有设备投资高，能耗大，干燥时间长的缺点。能量的供应即加热方式、升华水汽的流动条件、物料的输运性质是影响真空冻干性能的主要因素间。本文以牛肉的真空冷冻干燥过程为例，建立过程的非稳态数学模型，利用数值求解的结果，结合实验分析，研究了通过千层的辐射加热和通过冻结层的导热加热条件下真空冻干过程中传热传质的机理，分析了加热方式对缩短干燥时间的影响…