一种新型超支化聚芳亚胺高分子的合成及表征

通过苯酚,甲醛,苯胺的曼尼希反应及产物的环氧化反应,得到了含一个环氧基团和二至三个亚氨基团的新型超支化单体。通过超支化单体中亚氨基和环氧基团之间的开环反应,得到了重均分子量为13900的超支化高分子。通过IR,^1H-NMR和GPC等方法对产物进行了表征。并采用DSC对合成的超支化高分子固化环氧树脂的行为进行了初步探索。     

Well‐Defined Metal Nanoparticles@Covalent Organic Framework Yolk–Shell Nanocages by ZIF‐8 Template as Catalytic Nanoreactors

Yolk–shell nanoreactors have received considerable interest for use in catalysis. However, the controlled synthesis of continuous crystalline shells without imperfections or cracks remains challenging. Here, a strategy for the synthesis of yolk–shell metal nanoparticles@covalent organic framework (MNPs@COF) nanoreactors by using MNPs@ZIF‐8 core–shell nanostructures as a self‐template is designed and developed. The COF shell is formed through an amorphous‐to‐crystalline transformation process of a polyimine shell in a mildly acidic solution, while the ZIF‐8 is etched in situ, generating a void space between the MNPs core and the COF shell. With the protection of the COF shell, multiple ligand‐free MNPs are confined inside of the hollow nanocages. Importantly, the synthetic strategy can be generalized to engineer the functions and properties of the designed yolk–shell nanocages by varying the structure of the COF shell and/or the composition of the core MNPs. Representative Pd@H‐TpPa yolk–shell nanocages with active Pd NP cores and permeable TpPa shells exhibit high catalytic activity and stability in the reduction of 4‐nitrophenol by NaBH₄ at room temperature.     

Large Area Self-Assembled Ultrathin Polyimine Nanofilms Formed at the Liquid–Liquid Interface Used for Molecular Separation

Separation membranes with higher molecular weight cut-offs are needed to separate ions and small molecules from a mixed feed. The molecular sieving phenomenon can be utilized to separate smaller species with well-defined dimensions from a mixture. Here, the formation of freestanding polyimine nanofilms with thicknesses down to ≈14 nm synthesized via self-assembly of pre-synthesized imine oligomers is reported. Nanofilms are fabricated at the water–xylene interface followed by reversible condensation of polymerization according to the Pieranski theory. Polyimine nanofilm composite membranes are made via transferring the freestanding nanofilm onto ultrafiltration supports. High water permeance of 49.5 L m^-2 h⁻¹ bar⁻¹ is achieved with a complete rejection of brilliant blue-R (BBR; molecular weight = 825 g mol⁻¹) and no more than 10% rejection of monovalent and divalent salts. However, for a mixed feed of BBR dye and monovalent salt, the salt rejection is increased to ≈18%. Membranes are also capable of separating small dyes (e.g., methyl orange; MO; molecular weight = 327 g mol⁻¹) from a mixed feed of BBR and MO. Considering a thickness of ≈14 nm and its separation efficiency, the present membrane has significance in separation processes.     

Automatic algorithm for inverse synthetic aperture radar images recognition and classification

The authors propose an algorithm for automatic aircraft categories that is models classification from inverse synthetic aperture radar (ISAR) images that use pulse reflection shape and Doppler shifts of parts of aircraft that are in any maneuver that introduces rotation to the target. The authors artificially generated five different categories of ISAR aircraft using computer simulations and tested these simulated ISAR aircraft images of the airplanes defined by size and shape that are flying in a prescribed holding pattern. The authors investigate in what parts of the holding pattern the ISAR reflections provide information that makes it possible to identify to which of the five categories an aircraft in the holding pattern belongs. The obtained results show that it is possible in most parts of the holding pattern to successfully classify the various aircraft targets.     

人性化设计理念在工业设计中的剖析和运用

归纳和概括出人性化设计理念在当今时代背景下包括了4大方面的内容和范畴:为人的物质和精神满足的设计;为不同特征的人群的设计;"形式服从情感"的设计;多学科的交叉、合作性设计.并通过工业设计实例对它们给予了充分的论证和说明,从而使人们对以"人"为中心的人性化设计理念有更清楚和全面的认识并在设计中给予充分的应用和体现.     

新型五孔PVDF共混改性膜抗污染性能研究

观察新型五孔PVDF共混改性纤维膜SEM形貌特征,测量改性膜的接触角和临界通量,1#(PVDF/PMMA/TPU)、2#(PVDF/PMMA/PVC)共混改性膜分别在次临界和超临界通量下进行过滤实验.结果表明:PVDF共混改性膜具有优良的微观结构,且1#共混膜性能较好;1#共混膜的接触角比2#共混膜小;1#、2#共混膜的临界通量分别为10和14L/(m2.h);1#共混膜比2#共混膜抗污染性能好;次临界通量下共混膜的运行比超临界通量下的稳定.两种共混膜分别在次临界通量下采用单独超滤和混凝+超滤工艺处理某市地表水,得出混凝+超滤工艺处理效果较好,且1#共混膜比2#共混膜处理效果好.     

蒸汽管爆裂原因分析

蒸汽管材料为15CrMoG,设计寿命为15-20 a（年）,使用一年半后发生了爆裂,现场调查表明蒸气管有超温使用现象。通过化学成分分析和常温力学性能分析表明蒸气管用料符合技术要求。金相分析结果表明蒸汽管有蠕变空洞和珠光体球化现象,高温瞬时力学性能试验结果表明蒸汽管于705℃时力学性能已明显降低,断口宏观检验和断口微观分析均表明该蒸汽管爆裂具有超温爆裂特征。     

A micromechanical characterization of graphite-fiber/epoxy composites containing a heterogeneous interphase region

An improved micromechanical model based on the method of cells is introduced in order to describe three-phase, continuous-fiber composite materials containing a heterogeneous interphase region. The model's capability represents a significant improvement over that of the previous version (which is applicable to a homogeneous interphase) in that additional microstress information is obtained within the interphase region. A critical assessment of the model demonstrates that the predictions are consistent with data reproduced by using other micromechanical models. The study includes a parametric simulation in which the effective properties and the mechanical stresses associated with model graphite-fiber/epoxy composites are predicted as a function of the dimensions and Young's modulus of the interphase. Three different interphases are modeled such that the Young's modulus varies between that of the fiber and the matrix according to a generalized parabolic function of the radial coordinate. The parabolic functions are specified such that two of the model composites possess an interphase whose effective Young's modulus is above that of the matrix. The third interphase is specified such that its effective Young's modulus is below that of the matrix. The data indicate that the interphase dimensions and the functional form describing the interphase Young's modulus significantly influence the composite microstresses. These data may be used to help identify optimum material combinations during composite material synthesis.     

Instrument myopia.

The basis for instrument myopia, the tendency to accommodate inappropriately while viewing through an optical instrument, was investigated in three experiments. The first demonstrated that the distance of a peripheral surround, analogous to a field stop, influences accommodation but that the magnitude of the effect cannot account for instrument myopia. The second experiment re-examined the hypothesis that perceived distance can affect accommodation. The data indicate that perceived distance is unlikely to influence accommodation and does not provide an explanation of instrument myopia. The last experiment tested the hypothesis that instrument myopia is a manifestation of the return of accommodation to an intermediate state of rest or equilibrium in the absence of an adequate stimulus for accommodation. Implications of the intermediate-resting-state hypothesis are discussed.     

非线性弹性直杆纵振时的混沌行为

研究了S形本构关系的弹性直杆纵振时的混沌行为.用Galerkin原理将杆纵振时的动力控制方程转化为二阶三次非线性微分动力系统;给出了其产生同宿轨道和异宿轨道的条件,得到了同宿轨道的参数方程;借助Melnikov函数给出了系统发生混沌的临界条件;数值计算给出了混沌运动区域随β和γ的变化规律,用分岔图、位移时程曲线、相平面图和Poincaré映射判断了系统的运动行为即定常还是混沌.进一步的研究还表明本构关系中的二次非线性项对系统的动力响应具有很大的影响.     

聚碳酸酯分子量及其分布、热稳定性研究

用GPC法测定了PC样品的分子量及其分布,用原位动态FT－IR,TG对国内外生产的PC样品的热稳定性进行了研究,结果表明,PC样品的分子量及其分布是影响PC热稳定性的主要因素,分子量越大,分布指数越小,低分子含量越低,则PC越稳定。     

阳离子表面活性剂为乳化剂原位乳液聚合制备PS/MMT纳米复合材料

针对原位乳液聚合法制备聚合物/蒙脱土(MM T)纳米复合材料,为了实现蒙脱土片层的有机化处理和纳米复合材料的形成一步完成,以十六烷基三甲基溴化铵为乳化剂原位乳液聚合制备了PS/MM T纳米复合材料。XRD、FT-IR、TEM等分析表明,聚苯乙烯已插层进入蒙脱土的层间。在制备过程中,CTAB既充当了乳化剂,又充当了蒙脱土的插层处理剂,促进了苯乙烯在蒙脱土层间的聚合,同时也造成了蒙脱土片层一定程度的聚并。DSC分析表明,复合物的玻璃化转变温度有一定程度的提高。另外,还对蒙脱土存在下乳液聚合的特点进行了研究,发现MM T片层对乳液聚合的影响仅在聚合反应的初始阶段,使聚合速率有所下降,而对反应的后期阶段和反应产物的分子量影响不大。     

聚丙烯-锡复合材料的研究

通过熔融混炼制备了PP-Sn 复合材料。用SEM 观察了复合材料的形态结构, 用WAXD 研究了PP 的晶型结构, 并对复合体系的加工性能、复合材料的力学性能、导电性能进行了研究。 结果证实: Sn 粒子是PP 的成核剂并能诱发PP 的B-晶型产生; Sn 粒子加入能显著地提高PP 加工 性能; PP-Sn 纳米粒子复合材料具有优良的电学性能、较低的渗流阈值以及较高的拉伸韧性和冲 击韧性。      

Effect of thermal annealing on the efficiency of heterojunction photovoltaic cells fabricated using poly(3-hexylthiophene) and methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester

The effects of thermal annealing on the efficiency of heterojunction photovoltaic (PV) cells that were fabricated using poly(3-hexylthiophene) (P3HT) and methanofullerene, [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were investigated. The absorption spectra showed that the absorption intensity of the P3HT:PCBM layer that was annealed for 5 min had the highest value among the several samples with different annealing temperatures. The atomic force microscopy image showed that the P3HT:PCBM layer that was annealed for 5 min had the best surface morphology. The X-ray photoelectron spectroscopy demonstrated that the P3HT:PCBM layer that was annealed at 140 degrees C for 10 min enhanced the PCBM aggregation on the surface Al layer that was covered by the P3HT:PCBM layer. The efficiencies of the PV cells that were annealed at 3, 5, and 10 min were approximately 2.7, 4.2, and 3.5%, respectively. Based on the experiment results, the variations in the efficiency of the PV cells due their thermal treatment were described.     

三氟丙烯-醋酸乙烯酯共聚物及水解产物的表面性质

研究3,3,3-三氟丙烯结合量不同的三氟丙烯-醋酸乙烯酯共聚物的酸催化水解反应,并用红外光谱、凝胶色谱、氟离子选择电极电位分析法和差热分析等方法表征聚合物的结构、组成和性能随水解度不同引起的变化。结果表明:共聚物的酯基的水解度随水解时间的延长而增大,72h酯基的转化率可达99%,随着水解度的增大,共聚物的玻璃化转变温度Tg逐渐升高,表面能逐渐增大,明显地呈现表面活性剂性质,但共聚物的数均分子量(Mn)、重均分子量(Mw)及其分布指数(IPDI)变化不大。     

电沉积法制备铜分散电极

研究了电沉积制备铜分散电极的方法,通过对阴极极化曲线的测试,考察了电流密度及不同冲击电流方式对铜粉粒度的影响。结果表明:适当的电流密度、合适的分散剂、间歇式的电流是得到较细铜粉的条件。同时对铜分散电极的电化学性质进行初步测试,结果表明铜粉细化以后,铜分散差电池的电动势值有所上升。     

声矢量信号双谱与互双谱估计算法

提出了声矢量信号双谱与互双谱估计算法,给出了算法的具体步骤。将算法应用于两类水中目标的特征提取,并用所提取特征构造了LMBP神经网络的输入向量集,对矢量水听器实测的水中目标进行了分类识别。识别结果验证了所提出算法的有效性。实验表明,B类目标识别率优于A类目标,原因是由于B类目标特征频率较集中,而A类目标特征频率较分散所致。互双谱特征分类结果优于双谱特征分类结果这个事实是与声压振速联合信号处理优于声压或振速单一信号处理相吻合的。     

上浆剂分子量对碳纤维表观性能及其界面性能影响研究

研究了不同分子量的上浆剂对碳纤维表观状态及其界面性能的影响,并采用了AFM,SEM等表面分析技术研究了上浆后碳纤维表面形貌.AFM,SEM证实了S-1表面没有小颗粒存在,沟槽较均匀,而S-2表面的沟槽较深,S-3表面的沟槽较浅,且表面都有小的颗粒.XPS证实了S-1表面含有O元素含量最高,表面极性官能团较多.上浆剂分子...     

定向凝固高铬白口铸铁干滑动摩擦磨损特性

研究了定向凝固高铬白口铸铁与淬火 40Cr钢 (硬度HRC5 1～ 5 3 )配副时碳化物纤维排列不同位向的干摩擦磨损特性。结果表明 ,碳化物纤维排列不同位向的相对耐磨性随摩擦功率而变化。摩擦功率低于某一临界值时 ,碳化物纤维垂直位向的磨损率较其它位向的低 ;摩擦功率高于该临界值时 ,碳化物纤维垂直位向的磨损率反而高于其它位向的。该临界值的高低与基体组织有关 ,奥氏体基体时最高。摩擦系数与碳化物纤维排列位向无关。     

Defluoridation behavior of nanostructured hydroxyapatite synthesized through an ultrasonic and microwave combined technique

The absorption performance of a nano-structured hydroxyapatite produced from a combined ultrasonic and microwave technique was examined for the removal of fluoride from contaminated water. The effect of physical and chemical parameters such as initial pH, contact time, initial fluoride concentration and temperature were investigated. The results indicated that the equilibrium adsorption data followed both the Langmuir and Freundlich isotherms, with a maximum monolayer adsorption capacity of 5.5mg/g at 298K. In addition, the kinetic studies have shown that the fluoride adsorption data followed a pseudo-second order model and that the intra-particle diffusion process played a significant role in determining the rate. The thermodynamic analysis also established that the adsorption process was endothermic and spontaneous. The initial and final fluoride loaded nano-hydroxyapatite samples were characterized using FESEM, TEM, XRD, FTIR and XPS methods. The analysis revealed that structural changes to the adsorbent had taken place.