一步法制二甲醚工艺及催化剂的研究

本文采用共沉淀沉积法制备了一步法合成二甲醚的双功能催化剂，并在固定床高压流动反应装置上对其催化性能进行研究，考察了MnO2助剂对Cu—ZnO—ZrO2／HZSM—5催化剂性能的影响以及工艺条件对二甲醚合成的影响。采用TPR、XRD等测试方法对催化剂进行了表征，结果证明：MnO2助剂的加入，能够增加活性中心数量，提高催化剂的活性。     

HDPE／炭黑导电复合材料的改性

本文研究了导电炭黑的品种、含量及其对高密度聚乙烯（ＨＤＰＥ）性能的影响，以及动态硫化对改善ＨＤＰＥ／导电炭黑复合材料物性的贡献。结果表明，ＨＧ－４型导电炭黑填充ＨＤＰＥ具有很好的导电性，复合材料力学性能较差；ＡＣＥＴ炭黑导电性较差，复合材料力学性能最好。炭黑并用能有效地降低生产成本，而且保持了材料的性能。动态硫化法可以克服复合材料物性差的弱点，并能保持改性材料的高导电性。在ＨＧ－４型炭黑含量为７份时，材料的拉伸强度１３ＭＰａ，断裂伸长率３５０％，体积电阻率为２．１Ω·ｃｍ。     

Bidirectional Label Propagation over Graphs

Graph-Based label propagation algorithms are popular in the state-of-the-art semi-supervised learning research. The key idea underlying this algorithmic family is to enforce labeling consistency between any two examples with a positive similarity. However, negative similarities or dissimilarities are equivalently valuable in practice. To this end, we simultaneously leverage similarities and dissimilarities in our proposed semi-supervised learning algorithm which we term Bidirectional Label Propagation (BLP). Different from previous label propagation mechanisms that proceed along a single direction of graph edges, the BLP algorithm can propagate labels along not only positive but also negative edge directions. By using an initial neighborhood graph and class assignment constraints inherent among the labeled examples, a set of class-specific graphs are learned, which include both positive and negative edges and thus reveal discriminative cues. Over the learned graphs, a convex propagation criterion is carried out to ensure consistent labelings along the positive edges and inconsistent labelings along the negative edges. Experimental evidence discovered in synthetic and real-world datasets validates excellent performance of the proposed BLP algorithm.     

Fe~(2+)注人Al_2O_3陶瓷及其退火改善材料表面电学性能的研究

对透明Al_2O_3陶瓷进行了Fe元素的离子注入。用“Van der Pauw”方法测定注入层的电阻率,并结合Hall效应测量,确定样品载流子浓度和迁移率。 本文主要阐述未经退火和退火的Fe~(2+)注入Al_2O_3陶瓷表面电性能,并应用Rutherford背散射技术等方法进行分析比较,试图得到有关晶格损伤及恢复、注入离子的纵向浓度分布,缺陷等信息。最后,简要地叙述了注入层的导电机制。     

螺旋藻泡载分离法采收的实验室研究

在一种斜臂泡沫分离装置上，较为详细地研究了泡沫塔构造、起泡剂Tween 20浓度、载气流率、pH值和乙醇浓度等因素对螺旋藻泡载采收性能的影响. 结果表明，斜臂泡沫塔可明显改善藻细胞的泡载性能, 当Tween 20浓度为100 mg/L、载气流率为30 L/h及pH=11、乙醇浓度为1%(j)时，泡载采收过程的分离因子R和浓缩倍数a可分别达到5.04~6.52和2.74~4.31.     

Polymer pendant ligand chemistry, 4. Recovery of precious metal ions from strongly acidic solution with a polymer-supported o-phenylenediamine hydrochloride ligand

We report on the synthesis and reactivity of a polymer-supported o-phenylenediamine hydrochloride ligand, PS-PDHC, using macroporous 6% crosslinked polystyrene-divinylbenzene beads. The PS-PDHC ligand was found to be highly selective to AuCl₄⁻ ions in strongly acidic solutions in the presence of other precious metal ions, PdCl₄²⁻, PtCl₄²⁻, RhCl₆³⁻, and RuCl₅²⁻ (selectivity values: 2.5, Au/Pd; 7.5, Au/Pt; 7, Au/Rh; 2.2, Au/Ru) as well as other transition metal ions, Fe ³⁺, Cr³⁺, CU²⁺, Nit+, and Mn²⁺. The sorption capacity, selectivity, kinetics of removal and recovery, and solution isotherms have been determined for AuCl₄⁻ ions in competition with the above-mentioned metal ions. The relative ease of formation of the anionic complex in 0.5 M HCI, AuCl₄⁻ was thought to be the primary reason for its selective ability to bind to the PS-PDHC ligand by an anion-exchange mechanism. Therefore, the effect of the HCI concentration on the kinetics of AuCl₄⁻ ion removal from solution was also investigated to clearly show that raising the pH from 0 to 5 caused a dramatic decrease in rate. The AuCl₄⁻ ion can be recovered quantitatively from the PS-PDHC beads using a 5% thiourea solution in 0.1 M HCl, allowing the polymer-supported ligand to be reused.     

耐高温水蒸汽氟橡胶的研究

对四氟化乙丙橡胶（ＴＰ－２）和氟橡胶（ＦＫＭ－２４６Ｇ）进行了耐２８０℃水蒸汽试验。结果表明：以过氧化二异丙－三烯丙基异氰脲酸酯为硫化体系的ＴＰ－２硫化胶的耐高温水蒸汽性能，明显优于以Ｎ，Ｎ＇－双肉桂叉－１，６－己二胺为硫化体系的ＦＫＭ－２４６Ｇ硫化胶和以过氧化苯甲酰为硫化体系的ＦＫＭ－２４６Ｇ硫化胶。     

Comparison of microwave and thermal cure of epoxy resins

Stoichiometric mixtures of DGEBA (diglycidyl ether of bisphenol A)/DDS (diaminodiphenyl sulfone) and DGEBA/mPDA (meta phenylene diamine) have been isothermally cured by electromagnetic radiation and conventional heating using thin film sample configurations. Fourier transform infrared spectroscopy (FTIR) was used to measure the extent of cure. Thermal mechanical analysis (TMA) was used to determine the glass transition temperatures directly from the cured thin film samples. Well-defined glass transitions were observed in the TMA thermograph for both thermal and microwave cured samples. Significant increases in the reaction rates have been observed in the microwave cured DGEBA/DDS samples. Only slight increases in the reaction rates have been observed in the microwave cured DGEBA/mPDA samples. Higher glass transition temperatures were obtained in microwave cured samples compared to those of thermally cured ones after gelation. The magnitude of increases of glass transition temperature is much larger for the DGEBA/DDS system than DGEBA/mPDA system. The microwave radiation effect was much more significant in DGEBA/DDS system than in DGEBA/mPDA system. DiBenedetto's model was used to fit the experimental T_g data of both thermal and microwave cured epoxy resins.     

高强混凝土受火后力学性能变化规律的研究

对受火后的混凝土试件进行了抗压强度、抗折强度和劈裂抗拉强度试验,讨论了温度、强度等级、试件尺寸、含水量对其高温后力学性能的影响。研究表明,受火后,抗折强度较抗压强度下降更快;高强度的混凝土在600℃前抗压强度下降不多;大尺寸混凝土试件较小尺寸混凝土试件的残余抗压强度下降慢;混凝土试件的含水率越高,相对残余抗压强度越低。采用超声波速度法和质量损失法对火灾高温后混凝土内部结构的变化进行了探讨。     

Phase behavior and density of polysulfone in binary fluid mixtures of tetrahydrofuran and carbon dioxide under high pressure: Miscibility windows

Mixtures of tetrahydrofuran (THF) and carbon dioxide (CO₂) were identified as new solvent systems for polysulfone. The miscibility and density of polysulfone in binary fluid mixtures of THF and CO₂ were investigated from 300 to 425 K at pressures up to 70 MPa. The influence of the CO₂ and polysulfone concentrations was studied, with the concentrations of the other two components kept constant. At a 4.5 wt % polymer concentration, the demixing pressures in a 10 wt % CO₂ and 90 wt % THF mixture increased with temperature (310–425 K) from 15 to 40 MPa. With increasing CO₂ concentration (from ca. 10 to 14 wt %), a significant increase (from 15 to 70 MPa at 310 K) was observed in the demixing pressures. Furthermore, with an increasing amount of CO₂, the nature of the phase boundary shifted from lower critical solution temperature behavior to upper critical solution temperature behavior. The influence of the polymer concentration was studied in the 0–5 wt % range at two CO₂ levels, with solvent compositions of 10 wt % CO₂ and 90 wt % THF and 13 wt % CO₂ and 87 wt % THF. The system with a higher level of CO₂ (13 wt %) showed highly unusual phase behavior: on pressure–composition and temperature–composition diagrams, the system displayed two distinct regions of miscibility. In the system with 10 wt % CO₂, the distinct regions of miscibility that were observed in the system with 13 wt % CO₂ partially overlapped and led to a W‐shape phase boundary. The densities of the polymer solutions were measured from the one‐phase region through the demixing point into the two‐phase region at a constant temperature. No significant change in density was found around the phase boundary; this indicated that the coexisting phases had similar densities, as is often the case with liquid–liquid phase separation in polymer solutions under high pressure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2357–2362, 2002