A Study on the Bonding Technology in Sliced Bamboo Veneer Manufacturing

This paper deals with the gluing of small sized bamboo strips into laminated bamboo timbers, and is aimed at utilizing bamboo resources to produce sliced bamboo veneer to replace the current more expensive sliced wood veneer. These laminated bamboo planks glued with MUF (melamine-urea-formaldehyde) resin retained their adhesion even after treatment in water at 60°C for 3 h under a pressure of 0.4 MPa. The bamboo laminated timbers produced from gluing laminated bamboo planks (the ratio of the matrix to the curing agent was 100:25 by weight) can satisfy the requirement of adhesion sustainability after treatment in water at 50°C for 8 h. The results showed that mixture of UF (urea-formaldehyde) resin and PVA (polyvinyl acetate) adhesive with a weight ratio of 1:1 can be used to overlay non-woven cloth on the back of sliced bamboo veneer. The surface bonding strength of MDF (medium-density fibreboard) overlaid by sliced bamboo veneer, backed with non-woven cloth, satisfies the requirement of the Chinese standard GB/T15104.     

基于HOT理论的网络抗毁性动态演化模型

建立一种具有抗毁性的网络动态演化模型,利用HOT理论,通过节点的择优连接机制,使系统的抗攻击能力和自恢复能力等特性朝最优的方向演化。通过调整节点自身的属性,产生节点度符合幂率分布的网络抗毁性动态演化模型。仿真结果表明,与相同规模的BA网络模型相比,按照该方法建立的HOT网络模型具有更高的抗毁性。     

高工作温度InAlSb红外探测器的研究进展

概括了国外InAlSb红外探测器的研究现状、材料性质以及发展趋势,并介 绍了几种不同的器件结构及其性能情况。InAlSb/InSb红外探测器的设计目标主要是通过抑制暗电流来 提高探测器的工作温度。近年来,基于传统InSb探测器的成熟工艺与技术,InAlSb探测器的性 能得到了不断提升。该研究对红外制导、预警等军事领域具有重要的研究意义和应用价值。     

8—THE DRY WEAR OF STEEL,IN RELATION TO SPINNING-TRAVELLER WEAR

An account is given of a study of the wear of steel under conditions related to the wear of spinning travellers, and it is shown that there is a critical bulk temperature near 100°C above which traveller wear is likely to increase rapidly with increasing load. It is believed that the high wear rates are due to thermal softening of the metal near the rubbing surfaces, and oxides on the rubbing surfaces appear to be the principal agents of wear. The results obtained are compared with the observations of other workers that are reported in the literature.     

Shrinkage porosity and its relation to solidification structure of grey cast iron parts

Abstract

The purpose of this work was to investigate the relation between shrinkage porosity and the macrostructure. Based on results from an earlier investigation regarding shrinkage porosity and its characteristic features, a test casting was developed. The macrostructure was preserved using direct austempering after solidification heat treatment. Shrinkage porosity was found in regions where it was designed to occur. It was also found that this type of porosity is connected to the atmosphere via defects located on the surface, confirming earlier findings. Beneath the surface, it extends as a three-dimensional network through the casting. The shrinkage porosity was, in some cases, found along the boundaries separating primary crystals, and in some cases, it encircled separate primary crystals. A shrinkage porosity formation mechanism is proposed based on these observations, discussing the importance of a rigid columnar zone, movement of a local thermal centre and how pressure differences developing during solidification influence the formation of shrinkage porosity.     

Continuous separation of Fe–Al–Zn dross phase from hot dip galvanised melt using alternating magnetic field

Abstract

Experiments to continuously separate Fe–Al–Zn dross phase from hot dip galvanising zinc melt were conducted on a laboratory scale apparatus by using high frequency alternating magnetic field. Effects of processing time (t) on separation efficiency were investigated. The experimental results show that using the electromagnetic repulsive force resulting from the electrical conductivity difference between zinc melt and Fe–Al–Zn dross phase, the deleterious zinc dross particles causing surface defects of galvanising steel sheets can be continuously separated from the zinc bath under alternating magnetic field, and the separation efficiency increases with the increase in processing time. When the magnetic frequency is 17·5 kHz, the effective magnetic flux intensity is 0·1 T, the cross-section of the ceramic square pipe is 10 × 10 mm, and the processing time is 0·6–2·5 s, the separation efficiency of zinc dross varies from 43·76 to 85·71%, and the experimental results are in reasonable agreement with the theoretical results.     

Thermophysical properties of slags for process control

Abstract

Thermophysical properties have been shown to be important in a number of industrial processes. Unfortunately, for a number of properties there are scant data available and/or the data that are available are of dubious quality. In the Thermo-Physical Property Group at the National Physical Laboratory (NPL) the aim has been to develop measurement techniques capable of working in the difficult environments that are typical of industrial processes. This paper presents current developments at NPL in techniques to measure the thermal diffusivity of liquid slags using a laser flash and insights into the copper smelting process using interfacial tension techniques.     

Thermomechanical processing of 42CrMoS4 steel

Abstract

Billets of 42CrMoS4 steel were subjected to a programme including forging and rolling to different reduction ratios, followed by quenching and tempering to simulate online thermomechanical treatment (TMT) during rolling. The mechanical properties obtained were compared with those obtained by conventional heat treatment (CHT) (quenching from 860°C and tempering). It was found that increasing the hot reduction ratio from 18 to 60%, accompanied by a decrease in the finish rolling temperature from 900 to 750°C, enhances strength only at the expense of elongation, while rapid quenching instead of air cooling from the same finish rolling temperature yields improvements in both strength and ductility. It was also found that CHT provides higher hardness, whereas TMT provides higher impact toughness. TMT will confer major economic savings since the heat treatment is achieved online.     

Developments in oriented polymers, 1970–2004

Abstract

The discovery of methods to make highly oriented polymers has given tremendous stimulus to both basic polymer science and industrial developments in the period 1970 to the present. High modulus, high strength fibres for aramids and polyethylene, are based on very different methodologies but the ultimate result is similar in producing fully extended polymer chains. For polymers in solid sections, the enhancement of properties is less dramatic but still very worthwhile. In this case, three methods are described: hydrostatic extrusion, die-drawing and hot compaction of oriented fibres and tapes. Hot compaction is a new technique with many possibilities for which a wide range of applications has already been identified.     

Evaluation of chemical nucleation driving force for stoichiometric compounds with variable composition

Abstract

This work puts in evidence some inconsistencies in the method currently used in the literature for estimating the driving force for nucleation of stoichiometric phases with variable chemical composition, such as carbonitrides of Ti, Nb, etc. in steel. An alternative approach, properly accounting for the capillarity contribution to the Gibbs free energy change associated to the formation of the critical nucleus, is proposed. The chemical composition of the critical nucleus, which maximises the driving force for precipitation and allows the calculation of the critical radius, is found. Some examples of application are presented and the results are compared to those from the classical approach and discussed. The proposed method eliminates the contradiction encountered in previous approaches found in the literature and demonstrates that for these compounds the usual thermodynamic solution of the chemical equilibrium, which refers to flat surfaces, can not be directly extrapolated to describe the nucleation.