Morphology and failure in nanocomposites. Part II: surface investigation

Polymer composites filled with calcium carbonate (CaCO₃) nanofillers (<100 nm), and kaolin filler of layered structure, both well suited to create nanocomposites, were analysed. The aim of this study was to investigate the influence of surface properties of the filler and matrix on the adhesion parameters at the interface in composites. The inverse gas chromatography, contact angle and capillary measurements were used for the surface characterization of filler and matrix. Although these methods are based on different assumptions, we found the same trends in the effects of filler surface treatment and/or matrix chemical structure on the changes in the dispersive and polar components of the surface energy. The energetics of the filler and matrix was varied in order to investigate the work of adhesion, interfacial energy and coefficient of spreading, and their influence on the composite properties. We found that the surface treatment of calcium carbonate filler lowered the filler surface energy and the work of adhesion in the composite with poly (vinyl acetate) matrix. The mechanical, thermal and morphological properties of the composite with treated CaCO₃, measured in the first part of this paper, indicated a weak and thin interphase. In the composite with kaolin filler the higher interaction with the polyacrylate copolymer matrix based on styrene as compared to the one based on methyl methacrylate, was confirmed by the higher work of adhesion in the interphase, resulting in a stronger reinforcing of the composite.     

定向纠斜技术

定向纠斜技术是定向钻井技术 在直井中的运用 和发展，是快速纠斜 和保证超标脱靶 直井安全钻达目标靶区的最简捷的技术方法。     

Computational analysis of fouling by low energy surfaces

Fouling is a cost increasing problem for a variety of industries including aerospace, chemical, petroleum, and food. There have been studies on mitigation of fouling some of which recommend use of lower surface free energy materials, manufactured by different techniques, as an alternative to conventional materials. Although modeling of fouling for a given surface has been an area of interest; there is a lack in the models about correlating the surface free energy with deposit amount computationally. In this study, computational model, including the effect of surface energy and operational parameters, was proposed and validated to estimate amount of foulants deposits and rate of deposition. Towards this purpose, four coated surfaces (Microlube/PTFE, TM117P, AMC148, and CNT) were compared with stainless steel (SS316 as control) for flow rates of 3 and 10 g/s and inlet milk temperatures of 40 and 60 °C. The percent error for the decrease in outlet milk temperatures between the experimental data and computed results was between 2% and 18% except for CNT (29.2%). The calculations of deposit amount for each test case and the surfaces tested were in good agreement with the experiments, i.e., average percent difference values between measured and calculated values were from 11.1% to 38.1% (except CNT) with overall average of 21.5%.     

Durable antimicrobial finish of cotton fabrics

Cotton fabrics were treated with Biopag, which does not have any functional groups that are reactive toward cellulose, using crosslinking agents or a binder, for the purpose of imparting a durable antimicrobial finish. In this respect, it was found that the crosslinking agents were more effective than the binder. It was confirmed by FT‐IR that the characteristic split peaks of Biopag were still seen even after repeated launderings. The crosslinking agents deteriorated the whiteness and tensile strength of the Biopag‐treated cotton fabrics, while the wrinkle recovery angles (WRAs) were significantly improved. The one‐step padding of Biopag and the crosslinking agent was found to be superior to the two‐step padding method in which Biopag padding was followed by padding of crosslinking agent in respect of WRA, whereas the whiteness and tensile strength were vice versa. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Determination of the polymer‐solvent contact angle by the capillary raising curve,applied to the field of supports for homogeneous catalysts

A comprehension of the phenomenon that controls the diffusion of an organic solvent to the pores of a polymeric matrix is fundamental for optimizing the operating conditions to distribute a homogeneous catalyst, which has to be supported on it. The traditional sessile drop method is impossible to use when a high polymer‐solvent affinity exists. In this case, a different determination technique, similar to the Wilhelmy static mode method and based on the direct observation of the capillary raising curve of the solvent on the polymeric surface, has been set together with an experimental apparatus specifically built to perform measurements at a desired temperature and atmosphere. Such a technique has been demonstrated to be easy and promising for differentiating the behavior of different polyolefins [polypropylene (PP), high density polyethylene (HDPE), heterophasic copolymers (COPO)] at equal solvent and different temperatures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

基于关节优先级的冗余机械臂柔顺控制方法

针对冗余机械臂柔顺控制过程中某些关节运动可能超出安全范围导致安全事故的问题，提出一种基于关节优先级的冗余机械臂柔顺控制方法。此方法通过雅可比矩阵的加权广义逆矩阵与阻抗控制中机械臂的末端速度相结合，计算出关节角度增量，并对关节角度进行迭代更新。在机械臂运动过程中，为减小超限关节的角度增量，将相应关节设置较小的关节优先级，将超限关节角度变化保持在安全范围内。最后使用一种八自由度的冗余机械臂进行柔顺控制实验验证。结果表明：将相应关节设置较小优先级后，该关节角度增量减小，证明了该柔顺控制方法的可行性和有效性。     

采用荷载-裂缝张开口位移曲线确定混凝土三点弯曲梁的断裂能

在采用荷载-裂缝口张开位移曲线确定断裂能思路的启发下,假设带缺口梁旋转点为等效虚拟裂缝的尖端点,根据旋转角和断裂功的概念,推导出了由三点弯曲梁试验测定的荷载-裂缝口张开位移曲线计算断裂能的计算公式,进行了不同高度的三点弯曲梁断裂试验,使用新公式计算了断裂能.结果表明,在试验范围内由荷载-裂缝口张开位移曲线计算的断裂能接近于采用RILEM方法确定的断裂能,且变化较为稳定,可认为不存在尺寸效应.     

多层自动存储装置安装测量新方法—零i角法

在西南铝多层自动存储装置安装测量中，笔者摸索出了一种进行特种精密水准测量的新方法-“零i角法”。该方法的应用解决了安装测量中遇到的技术难题，满足了安装测量的技术要求，是值得推广应用的一种方法。     

NEW OPTIMAL LARGE ANGLE MANEUVER STRATEGY FOR SINGLE FLEXIBLE LINK

INTRODUCTIONTo accommodate the requirement of lightweight,for many machine systems, such as flexiblemanipulator, large solar array and flexible antennas ofspacecraft, flexibility has become an imPOrtantcharacteristic. But flexible vibration can degrade badlythe peforance and the precision of flexible systems.Control of vibration becomes very important asdesigners attempt to push the state of the art withfaster and lighter machines systems. Researchers haveexammed many different controlle…