Dipyrenylpyridines for electron-transporting materials in organic light emitting devices and their structural effect on electron injection from LiF/Al cathode

3,5-Dipyrenylpyridine (PY1) and 2,6-dipyrenylpyridine (PY2) were synthesized to achieve not only efficient electron injection from cathode but also high electron mobility. The both of compounds showed much higher electron mobilities than that of Alq₃, and have a similar ionization potential and electron affinity. However, the barrier height of electron injection from cathode to PY1 in an organic light emitting device was much smaller than that to PY2, probably due to the steric hindrance to the central pyridine group. These results suggest that the chemical affinity of electron-transporting materials with cathode is more important than their own electron affinity to improve the electron injection.     

Tensile and impact properties of fully green composites reinforced with mercerized ramie fibers

The purpose of this study is to create a natural fiber-reinforced fully green composite with excellent toughness. By treating ramie plied yarns in a high concentration alkali solution, the reinforcements were mercerized. Results of tensile tests showed that unidirectional composites using mercerized ramie yarns exhibited two to three times larger fracture strain, without a marked decrease in strength, than composites using untreated yarns. In addition, mercerization for the ramie yarns brings a better interfacial strength to the composites. Laminated composites using mercerized ramie yarns also showed approximately twice larger impact energy than composites using untreated yarns. Thus, mercerization for natural fibers is expected for application to mechanical materials requiring a high toughness.     

Postbuckling behaviour of stainless steel (SUS304) columns under loading-unloading cycles

Based on the equilibrium configuration paths, this study investigates the postbuckling behaviour, including the shape recovery capability, of stainless steel (SUS304) columns after a complete loading-unloading cycle. Experiments were conducted and later numerical simulation was carried out in order to analyze the observed buckling and postbuckling behaviour. Large deflection analysis is necessary for slender columns. Moreover, comparison of the experimental critical load with analytical predictions verifies the fact that physical nonlinearity should be taken into account to analyze the column’s buckling behaviour comprehensively. Thus, based on large deflection theory as well as the nonlinear stress-strain relations, the load-deformation curves of the columns during a complete loading-unloading cycle have been predicted by using the finite element modelling (FEM) code ANSYS.Precise and quantitative analyses of the results verify the fact that the material’s stress-strain properties, both in tension and compression, attribute to the column’s buckling behaviour.     

Quantitative acoustic emission source characterization of microcrackings in steel

Acoustic emission (AE) source wave analysis is a new NDE technique for the investigation of dynamic fracture process. We applied this technique to the quantitative characterization of crack sources in ductile fracture. Using two samples of ASTM A533B steel with different sulfur content, acoustic emissions during fracture toughness tests were detected, located, and analyzed. The detected AE signals were classified into two types according to the analyzed source waveforms. One was a signal due to microcracking at the MnS inclusion, and the other was a signal due to coalescence of the voids. The results of the source wave analysis showed that microcracking at the inclusions was due to Mode I type tension crack with sizes of 10–30 µm, and the coalescence of the voids was due to tension shear mixed cracks with sizes of 60–100 µm. It was confirmed that this technique is very effective for the quantitative evaluation of microcrackings and for the detection of the nucleation and growth of cracks.     

Acute ingestion of yerba mate infusion (Ilex paraguariensis) inhibits plasma and lipoprotein oxidation

Yerba mate extract (Ilex paraguariensis) is a source of phenolic compounds that possesses in vitro antioxidant activities and may contribute to a reduction in the risk of cardiovascular disease. In this study we examined the acute effects of the consumption of mate infusion on ex vivo plasma and low-density lipoprotein (LDL) oxidation, plasma antioxidant capacity, and platelet aggregation. Twelve healthy fasted subjects ingested 500 mL of mate infusion and blood samples were collected before and 1 h after mate intake. Lipid peroxidation of plasma and LDL was monitored by the measurement of cholesteryl-ester hydroperoxides (CE-OOH) and cholesterol oxides. The plasma antioxidant capacity was measured as ferric-reducing antioxidant potential (FRAP). Platelet aggregation was evaluated in platelet-rich plasma stimulated with adenosine diphosphate and coagulation was tested in platelet-poor plasma. Ingestion of mate infusion diminished the ex vivo oxidizability of both plasma and LDL particles. After mate intake, the CE-OOH levels were around 50% lower in plasma oxidized with copper or 2,2′-azobis[2-amidine-propane-hydrochloride] (AAPH) and the lag time to plasma oxidation increased 2-fold (P < 0.05). Copper- and AAPH-induced LDL peroxidation were also inhibited by around 50% and 20%, respectively, after mate consumption (P < 0.05). The levels of various oxysterols were significantly reduced in oxidized-plasma and LDL (P < 0.05) and FRAP increased by 7.7% after mate intake (P < 0.01). However, mate consumption did not inhibit platelet aggregation or blood coagulation. In summary, intake of yerba mate infusion improved the antioxidant capacity and the resistance of plasma and LDL particles to ex vivo lipid peroxidation.     

IEC阵风作用下箱梁断面的气动特性分析

基于二维非定常不可压缩雷诺平均N-S方程和RNG k-ε湍流模型,采用CFD（computational fluid dynamics）方法对箱梁断面在IEC（international electrotechnical commission）阵风以? 5°～+ 5°攻角作用下的气动力及流场特性进行数值模拟分析,获得了IEC阵风作用过程中箱梁断面的三分力系数的总体变化特征、入口边界静压变化特性及流场内静压的顺压和逆压特性等。分析表明,IEC阵风模型比TSI（technical specifications for interoperability）阵风模型更适于桥梁气动力的数值模拟分析。     

Ziegler-Natta/茂金属复合催化剂聚合性能的研究

制备了Ziegler-Natta/茂金属复合(Z-M)催化剂,用SEM技术对其形貌进行了表征,在10L丙烯液相本体聚合模试装置上对Z-M催化剂的氢调敏感性进行了评价。通过一段丙烯本体均聚、二段乙烯-丙烯近恒温恒压气相共聚模拟Spheripol-Ⅱ工艺制备了系列聚丙烯(PP)釜内合金;考察了二段共聚时的聚合反应动力学、乙烯与丙烯配比(n(C3)∶n(C2))对PP釜内合金性能的影响。实验结果表明,在一段均聚时Z-M催化剂具有较好的氢调敏感性,得到的均聚PP粒子具有较好的流动性;在二段共聚时,Z-M催化剂能在较长的共聚时间内保持较平稳、较高的共聚活性,改变n(C3)∶n(C2)时PP釜内合金中乙丙橡胶的质量分数可调(7.19%~10.75%),熔体流动速率(10min)可调(14.0~26.5g);n(C3)∶n(C2)对合金弯曲模量的影响不大;当n(C3)∶n(C2)=1.7时制备的PP釜内合金具有最大的冲击强度(92.9J/m)。     

Cu材料激光表面强化研究

采用激光技术对Cu基材进行表面强化处理。使用扫描电镜(SEM)、电子能谱计(EDS)和X射线衍射仪(XRD)对强化表面进行显微组织和物相分析,并测试了样品的显微硬度、耐磨性能和导电性能。结果表明,激光强化层无裂纹,组织细小均匀、呈快速凝固特征,强化层具有较高的硬度(平均硬度为625HV0.1)和良好的耐磨性,其磨损失重仅为纯Cu基材的1/5,而激光表面强化使导电性略微降低。激光表面强化层硬度和耐磨性的提高可归因于颗粒强化、细晶强化和固溶强化的共同作用,而导电性的降低程度主要受稀释率的影响。     

Experimental study on hysteresis phenomena of shock wave structure in an over-expanded axisymmetric jet

In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.