Visualization of the surface tension and gravitational effects on flow injection in center-gated disks

Flow injection in center-gated disks is numerically studied in this paper for possible applications in the manufacturing of composite materials in microgravity environment. The numerical method, which combines the finite element method with a predictor/corrector scheme, is used to determine the transient flow field. The effects of gravitation and surface tension on the development of flow front profile and velocity field are examined for a wide range of the governing parameters (namely, the capillary and Bonds numbers). It has been found that surface tension tends to hold the flow front in symmetric shape while gravitation is to distort it. The balance of these two forces has significant effects on the front shape, front tip traveling speed and required injection pressure. Good agreement is found between the numerical prediction and the experimental results concerning the advancement of the flow front and the front shape. The present results provide useful information in the design of resin transfer molding process in space.     

Liquid nucleating additives for improving thermal insulating properties and mechanical strength of polyisocyanurate foams

The effects of liquid-type nucleating silane additives on the cell structure, mechanical strength, and thermal insulating properties of the polyisocyanurate (PIR) foams have been studied. The PIR foams synthesized with hexamethyldisilazane (HMDS) as a silane additive showed the smaller average cell size and lower thermal conductivity than those of the PIR foams prepared with the hexamethyldisiloxane, dimethoxydimethylsilane, and hexadecyltrimethoxysilane. When HMDS was added, average cell size of the PIR foam was becoming smaller due to lower surface tension of the polyol solution, thereby the nucleation rate and number of bubbles produced were increased and then the cell size becomes smaller. The additives likely act as nucleating agents during the formation of PIR foams. The smaller cell size appears to be one of the major reasons for the improvement of thermal insulation properties and mechanical properties of the PIR foams. From the results of cell size, thermal conductivity, and mechanical strength of the PIR foams, it is suggested that the HMDS may be the efficient liquid-type additive for the reduction of cell size and improvement of the thermal insulation property of the PIR foams.     

An Elementary Plate Theory Prediction for Strain Energy Release Rate of the Constrained Blister Test

A technique based on elementary plate theory is proposed for estimating the strain energy release rate of the constrained blister specimen for the case of a relatively stiff blister adherend. The results of finite element analysis for an aluminum specimen confirm the applicability of the elementary plate theory approach for the constrained blister test. The paper also proposes an experimental scheme which could be automated to measure the necessary parameters to determine the strain energy release rate of the constrained blister specimen.     

A novel methodology in transforming bulk properties of refining streams into molecular information

Stricter and ever increasing environmental legislations and demand for higher quality products are the driving forces for the refiner in an attempt to characterise the refining streams on the molecular basis. The objective of this work is to develop a new methodology to interrelate the bulk properties and molecular information of the refining streams in order for refiners to look at the contribution of each molecular group on the properties of the refining streams.The molecular information of a particular refining stream is presented in the form of MTHS (molecular type homologous series) matrix representation [Peng, B., 1999. Molecular modelling of petroleum processes. Ph.D. Thesis, UMIST]. To enhance the accuracy and usability of the method, structural contribution of each isomer on various properties such as octane number, and reid vapour pressure, etc. are considered. Structural lumping rules are then applied to obtain the physical properties of each homologous series. Databases are set up for the properties and molecular information of typical refining streams. Automatic selection of sample matrices through linear combination is used to predict new composition matrices. The methodology is illustrated for refining streams with gasoline range hydrocarbons. The properties predicted based on the new methodology proves to be within 5-6% error range.     

高岭土的机械—化学剥离的工艺技术研究

将普通的搅拌机改装成为一种阻尼式砂磨机，它可以在比一般砂磨机低得多的转速下实现高岭土的有效剥离，使—2μm的含量由原料的28％提高到46．1％。同时试验了在高岭土中加入不同化学药剂的作用。实验证明，经化学药剂浸泡一段时间后再用阻尼砂磨机剥离，其剥离效果更为明显，其中—2μm含量可由原料的28％提高到66．9％。事实表明，采用机械和化学相结合的方法是高岭土剥离的一条有效途径。     

高频对焊螺旋管成型及焊接挤压力装置设计研究

本文介绍的圆锥芯棒成型器具有对接边螺旋管筒成型、合缝角自动形成和自动合缝的功能，经高频加热得到的对接焊缝螺旋管避免了传统搭焊螺旋管焊缝无法进行毛刺清除和质量检测控制的缺点。     

一种城区LiDAR点云数据的抽稀算法

当城区LiDAR点云数据密度较大时，存在大量的数据冗余，造成了计算量大、效率低、显示不便等一系列问题，使得建筑物的三维可视化及三维重建等应用受到较大挑战。针对该问题，结合泊松碟采样在测地空间中的地形自适应特点，提出了适用于城区LiDAR点云数据的抽稀算法。泊松碟采样随机将与已有采样点的测地距离大于某一阈值的点加入采样点集，并不断重复这一过程直至没有新的采样点加入为止。在此基础上，依据LiDAR点云数据的特点，定义了一种新的与所选点与其邻域内其他点间高度差标准差相关的加权测地距离，改进了泊松碟采样算法。该方法能有效调整城区建筑物的采样率，从而尽可能地保持建筑物的原始特征，并保留良好的可视化效果。四组对比实验结果表明了该算法的适用性及高效性。     

正电子在高能电子辐照聚乙烯和聚丙烯中的湮没特性

用正电子湮没寿命谱和多普勒展宽方法研究高能电子（12MeV）辐照聚丙烯和聚乙烯的不同特性，发现在160kGy剂量内，正电子在聚丙烯内的短寿命成分随着电子辐照剂量的增大而变长，中间成分的强度则减弱，但当剂量为320kGy时，各湮没寿命与没有辐照的样品类似。而长寿命成分的强度不随剂量增加而变化。在电子辐照的聚乙烯薄膜中，当剂量为80kGy时，正电子中间寿命强度I2增加，长寿命成分的强度I5则有所减少。之后，随着电子辐照剂量的增加，则不再变化。正电子湮没γ射线多普勒展宽S参数随电子辐照聚乙烯的剂量变化与I5相同。正电子湮没特性的差别表明高能电子辐照这两种聚合物所引起结构上的变化是不同的，并为其宏观特性（如力学性质变化）的改变提供了微观依据。