16—THE PREPARATION,FINE STRUCTURE,AND PHYSICAL PROPERTIES OF PARTLY METHYLATED COTTON FABRICS

Cotton fabric has been methylated under a variety of conditions. The extent of methylation has been shown to be dependent on the time of methylation and on the degree of swelling or disruption of structure. The latter is caused by the alkali pretreatment or by the swelling of the partly methylated cellulose. Fabric physical properties have been measured and the influence of the methylation treatment has been examined.     

Properties and improvement of super fine grained steel friction welded joint

Abstract

This paper describes friction welded joint properties of super fine grained steel (SFGS) and discusses improvements in these joint properties. The average grain size diameter of the SFGS base metal is ～0·6 μm, and its ultimate tensile strength is 660 MPa. The joint, made by a continuous drive friction welding machine (conventional method), fractured at the welded interface even though it possessed 100% joint efficiency. This was due to both the coarsening of the grain size and the softening of the welded interface with its adjacent region caused by heat input during braking times. The authors developed a joining method using a continuous drive friction welding machine that has an electromagnetic clutch to eliminate heat input during braking time, which was called the 'low heat input friction welding method' (LHI method). The joint obtained by the LHI method had the same tensile strength as the base metal at the friction time when the friction torque reached the initial peak. That is, the joint obtained 100% joint efficiency and fractured at the base metal, although the adjacent region of the welded interface softened only slightly. The grain size of this joint was smaller than that obtained by the conventional method. It was clarified that the optimum friction welded joint of the SFGS could be obtained by the LHI method in comparison with the conventional method.     

Mechanomaking of nanostructured hypereutectic white irons: powder fabrication

Abstract

White irons containing 5·7 wt-%C were produced by room temperature, high energy milling from iron and carbon elemental powders. Both iron and cementite phases have crystal sizes of less than 10 nm in the powders which have fully dense particles of 50 μm mean size. The gas content is 0·5 wt-% and the powder is stable up to 550°C. Above 550°C decomposition of cementite occurs, involving a decrease in combined carbon content from 5·7 to 3·5 wt-% (annealing at 1050°C). The crystal growth kinetics has two temperature regions with lower activation energies in the high temperature (above 800°C) region. Crystal sizes still below 100 nm were observed for annealing up to 800°C. The size distribution in mechanosynthesised powders was modified by tumbling (dry) and attritor (wet) milling down to mean sizes of 4 μm and 1·4 μm respectively. Whereas tumbling milling does not alter the properties of MS powders, wet attritor milling produced higher gas content (7 wt-%) and much decreased thermal stability. Mechanosynthesised and tumbling milled powders can be degassed prior to consolidation, while wet attritor milled ones cannot.     

Softening characteristics in ultra-narrow gap GMA welded joints of ultra-fine grained steel

Abstract

When a 800 MPa grade ultra-fine grained steel with ferrite grains less than 1 μm and dispersed fine cementite is welded, fine ferrite grains are coarsened resulting in remarkable softening in the heat affected zone (HAZ). The peak temperature at an arbitrary location in HAZ during welding was calculated by heat conduction analysis and the effect of welding thermal history on the microstructure of the UFG steel HAZ was examined by microscopic observation. Softening as a result of ferrite grain coarsening was observed in the region where the peak temperature reaches between 920 and 1300 K for the ultra-fine grained steel with an Ac ₁ temperature of 980 K and Ac ₃ of 1150 K. The formation of martensite–austenite constituents started as a second phase above the Ac ₁ temperature and they curbed HAZ softening in the peak temperature range between 1000 and 1250 K.     

Experimental study on fine motion control of underwater robots

This paper considers thruster dead zones and saturation limits, which are nonlinear elements that complicate fine motion control of underwater robots. If the vehicle is configured with redundant thrusters, the respective dead zones and their surrounding nonlinear regions could be avoided by implementing a null motion solution for the command input of the vehicle. This solution is derived from the vehicle's geometry and is realized before the application of the motion control algorithm. The result is an improvement in system performance exclusive of the implemented controller type. The approach is illustrated through simulation and experiment with an underwater robot, ODIN.     

32—SUPERMOLECULAR STRUCTURE AND FIBRE PROPERTIES

Various theories of fibre structure are briefly reviewed, and it is shown that the original ‘fringed-micelles’ theory is no longer considered valid. The influence of the genesis of fibres on their structure is demonstrated, and it is shown that, because of this difference in fibre formation, it is difficult to fit a single model to all fibres. The architectural models proposed for various fibres are discussed, and it is pointed out that the validity of these models can be tested by reference to the fibre properties.

It is emphasized that there is still insufficient knowledge of the behaviour of fibres subjected to transverse stresses, and it is shown that some of the phenomena that occur under the action of such stresses can be explained by the comparatively recent ‘fringed-fibrils’ theory of fibre structure. Finally, attention is drawn to some aspects of the structure and behaviour of fibres that are still unexplained, and towards which it is proposed that further research should be directed.     

基于 FINE CONE对微型扬声器振膜的模拟分析

将微型扬声器的振膜作为研究对象,采用FINE CONE模拟软件对微型扬声器振膜进行模拟分析,与KLIPPEL测试的结果进行对比,结果表明FINE CONE模拟的频饷曲线与KLIPPEL测试的曲线的变化趋势基本一致,FINE CONE为扬声器振膜的性能分析提供了一定的理论依据。     

软件定义网络与FINE

基于软件定义网络(SDN)的核心理念——3层抽象,提出了一种采用SDN思路的网络体系架构——未来网络体系结构创新环境(FINE)。在FINE体系架构基础上,研究了新型转发抽象技术及开放网络设备,构建了支持多域互联的网域操作系统,构建了全网级虚拟化云平台,实现了多元开放设备的统一管理和控制,进行了新型网络体系结构和新型IP协议的研究试验。     

Contribution of Colloidal Forces in Non-contact Area to the Adhesion Between a Micro-probe and a Substrate Surface: Theoretical Analysis

Colloidal forces outside the microscopic probe (particle)–substrate adhesion contact area were analyzed theoretically. Equations describing the van der Waals, electrical double layer, and hydrophobic forces were derived for the non-contact area of a probe–substrate system assuming a simple sphere–flat geometry. Two cases were considered: particles freely resting on the substrate surface and particles pulling off the substrate. The results of modeling presented in this communication suggest that the adhesion of fine particles (microscopic and sub-microscopic particles) to flat surfaces can be affected by the forces acting outside the contact area. However, due to increased distance between the particle and substrate during separation, both the van der Waals and electrostatic forces acting outside the contact area are negligibly small compared to the short-range adhesion forces and they do not contribute to the measured pull-off force to any great extent for most systems. On the contrary, our calculations suggest that the long-range hydrophobic forces can contribute to the strength of adhesion between hydrophobic fine particles and hydrophobic substrates.