Pore size control of porous silica by sol-gel process

Porous silica glass was prepared by sol-gel process from tetraethoxysilane (TEOS). The effects of solvents (water, ethanol), drying condition, heat treatment temperature on specific surface area and pore size distribution of porous silica were investigated. Gelation process accelerates with an increase of H₂O content, while retards with the increase of ethanol amount. Structure changes during heat treatment were studied by means of DTA, XRD. TEM micrographs show that the gel particles shrink after heated at 500°C, thus the average pore size decreases.     

石蜡光氯化合成氯蜡－70的研究──（Ⅲ）反应过程致色因素考察及生色机理研究

氯蜡－７０是—应用广泛、性能优良的精细化工产品，其色泽是—重要的技术指标，直接影响着产品的质量和应用。本文考察了合成反应过程导致生色的因素，指出原料中含有的少量环烷烃、芳烃、杂环有机物及少量无机杂质能影响产品的色泽，实验表明温度过高，光源波长选择不当也是致色的重要原因。研究了致色的过程，提出其生色历程是按照β－消除反应机理进行的，并做了具体描述。     

Effect of processing history on the properties of Ag-based tapes

The Bi-system tapes and coils were prepared by the powder-in-tube method. The effect of processing and heat treatment on the properties of the tapes and coils was studied. It is found that the shearing stress produced by the rolling process may destroy the 2223 phase, and the destroyed 2223 phase cannot be recovered by heat treatment, whereas the pressing stress produced by the uniaxial pressing process only makes the 2223 phase grains break, and the broken 2223 phase can be closed by the heat treatment. TheJ _c values of the rolling samples, pressing sample, and the coil with a diameter of 35 mm are over 1.3×10⁴, 2.5×10⁴, and 4×10³ A/cm² (77 K, 0 T), respectively.     

A study on the anodic protection of Titanium evaporators in Al2(SO4)3 solution

The feasibility of the anodic protection of titanium evaporators in Al₂(SO₄)₃ solution was studied by the measurement of polarization curves, weight loss, solubility of passive film and AC impedance. The protection parameters and efficiency were determined. In addition, the practical technology of anodic protection was studied by screening reference electrodes and auxiliary cathodes. Throwing power was also measured. Four rows of tube-type evaporators of titanium have been anodically protected in situ. Field tests lasting more than one year show satisfactory results.     

H∞ control versus disturbance-observer-basedcontrol

In the motion control field, a disturbance observer-based disturbance canceling control is often used as a robust control methodology. However, this method is nothing more than an alternative design of an integral controller, and the robust stability issue cannot be directly accounted for. In this paper, an extended H_∞ control scheme is proposed as a new robust motion control method which achieves the disturbance cancellation ability and guarantees robust stability automatically     

Very-high-speed fibre-optic networks for broadband communications

Single-mode optical fibres have an enormous transmission bandwidth which can support ultra-high-speed digital transmission and networking. The use of electrical signal-processing, however, ultimately limits the network capacity. To eliminate the throughput bottleneck, all-optical processing techniques should be employed in a fibre-optic network. This paper discusses several schemes for implementing optical time division multiple access (OTDMA) networks with the emphasis on optical clock distribution, synchronisation and all-optical detection. The use of a fast-switching bistable laser diode as an all-optical threshold detector and data regenerator is suggested. A dual-wavelength OTDMA technique is investigated, which can be used for digital TV or future HDTV distributions. Moreover, an efficient multiple access scheme, called wavelength division multiple access with optical time division multiplexing (WDMA-OTDM), is proposed for broadband communication services. It is shown that WDMA-OTDM has all the advantages possessed by the individual OTDMA and WDMA schemes but offers improved flexibility and capacity     

外加剂混凝土动态与静态坍落度损失的流变特性

本文对动、静态下混凝土坍落度损失的规律进行了研究,并从流变学的角度分析了外加剂对动、静态下混凝土坍落度损失的影响坍落度损失存在差别的原因.     

铝液夹杂物检测DMIRT－Ⅲ法的试验研究

提出了一种新的铝液夹杂物快速检测方法。导出了该法的检测原理方程。分析并试验研究了影响检测重复性和分辨率的因素。试验选择了较好的检测参数，并获得了较好的检测结果。