Ideal spread monolayer formation and surface pressure induced orientation in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) via hybridized with liquid crystal molecule on water

Hydrophobic Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) [F8BT] formed an ideal spread monolayer on a water surface by the cospreading method with liquid crystal molecule, 4′-pentyl-4-cyanobiphenyl [5CB]. The F8BT/5CB hybrid monolayers were characterized by surface pressure–area (π–A) isotherm measurements and atomic force microscopy (AFM). F8BT does not form a homogeneous monolayer by direct spreading on water from a single solution. The mixed film of two components, F8BT and 5CB, gave a characteristic pressure lift-off attributed to the hybrid monolayer above the 5CB plateau. AFM observation revealed that the spread monolayer of the F8BT formed on the top of the 5CB monolayer on water with the thickness of ca. 1.7 nm. The F8BT/5CB hybrid monolayers could be fully transferred onto a solid substrate, and pure F8BT monolayers were obtained after volatilization of 5CB by gentle heating. Polarized UV–vis absorption spectra showed that the main chain of F8BT preferentially oriented perpendicular to the compressive direction at the surface pressure of 10 mN m^?1 on water.     

Controlled synthesis of dense MgFe2O4 nanospheres by ultrasonic spray pyrolysis technique: Effect of ethanol addition to precursor solvent

We present the results of controlled synthesis of spherical shape magnesium ferrite (MgFe₂O₄) dense nanoparticles by using ultrasonic spray pyrolysis (USP) method without any post-annealing processes. A new strategy was proposed to improve nano-crystallinity and observed morphology by ethanol (EtOH) addition in the initial precursor solution of MgFe₂O₄. Influence of EtOH, not only decrease the synthesized secondary particle size but also enhancing crystallization into MgFe₂O₄ single phase cubic structure. We observe that average nanosphere size decrease from 220 to 189?nm but increases of crystallite size from 9.6 to 19.2?nm with increasing the amount of EtOH from 0 to 20?vol%. Also, surface morphology revealed that nanospheres with some irregular shape and rough surface appear in case of EtOH additives. The magnetic properties are studied and different parameters viz. saturation magnetization, remanence, and coercivity have been correlated with crystallite size.     

饱和砂土液化后的剪切吸水效应

饱和土在自然排水条件下随着剪切作用而发生的含水量增大的行为和过程被称为剪切吸水现象。本文发展了一种新的试验方法,成功地再现了从较松到密实状态的饱和砂土在振动液化后的剪切吸水现象,探讨了剪切吸水速率对饱和砂土液化后应力应变关系的影响。试验结果表明,具有相同密度的饱和砂土,其液化后的应力应变关系随剪切吸水速率的不同而呈现出硬化、理想塑性及软化的不同变化。文中给出了判定这些不同的液化后应力应变响应产生的条件     

Calibration of model constants in a biological reaction model for sewage treatment plants

Various biological reaction models have been proposed which estimate concentrations of soluble and insoluble components in effluent of sewage treatment plants. These models should be effective to develop a better operation system and plant design, but their formulas consist of nonlinear equations, and there are many model constants, which are not easy to calibrate. A technique has been proposed to decide the model constants by precise experiments, but it is not practical for design engineers or process operators to perform these experiments regularly. Other approaches which calibrate the model constants by mathematical techniques should be used. In this paper, the optimal regulator method of modern control theory is applied as a mathematical technique to calibrate the model constants. This method is applied in a small sewage treatment testing facility. Calibration of the model constants is examined to decrease the deviations between calculated and measured concentrations. Results show that calculated values of component concentrations approach measured values and the method is useful for actual plants.     

理学SIMULTIX 10/11型多道X射线荧光光谱仪的背景测定装置与应用

文章介绍了理学SIMULTIX 10/11多道同时型X射线荧光光谱仪上所配备的具有背景测定与扣除功能的固定型测角仪的原理、特点和应用实例。该测角仪能明显地提高痕量元素分析的灵敏度与准确度,而且扩大了对于不同类型样品的分析适应范围,例如铁素体与奥氏体样品中钒的测定等。     

Structure and ferroelectric phase transition of vinylidene fluoride-trifluoroethylene copolymers: 2. VDF 55% copolymer

Molecular and crystal structure changes in ferroelectric phase transition of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer with a VDF content of 55 mol% have been investigated by X-ray diffraction and infra-red and Raman spectroscopy. As the temperature rises from room temperature to the Curie point of ～60°C, the polar low-temperature phase consisting of all-trans chains experiences a first-order transition to the phase of tilted long trans segments connected by some skew bonds. At higher temperature this new phase transforms continuously and steeply to the non-polar high-temperature phase, where the molecular structure consists of a random combination of TG, T?, T₃G and $\text{T}{}_3\text{G}\text{?}$ rotational sequences. In the cooling process the high-temperature phase transforms to the cooled phase, which is essentially equivalent to the phase appearing intermediately in the heating process from the low-temperature to the high-temperature phase. The cooled phase gives a tilting X-ray fibre diagram and is found by X-ray analysis to contain an appreciable amount of so-called 60° domain structure. These are well interpreted by a conformational model of tilting trans structure containing skew linkages. The tensile stress along the fibre axis causes the transformation from the cooled phase to the low-temperature phase, where the probability of 60° domain structure and the degree of chain tilting are remarkably reduced.