Electrocatalytic behaviour of titanium implanted with nickel and molybdenum ions

Abstract

The electrocatalytic activity of titanium induced by ion implantation has been investigated. Ion implantation was carried out using a metal vapour vacuum arc source ion implanter at room temperature. Nickel ion implantation was followed by molybdenum ion implantation at doses ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm² at the same average extracting voltage of 45 kV. The concentration profiles of Ni and Mo ions in the near surface were detected by electron probe microanalysis and X-ray photoelectron spectroscopy. The catalytic behaviour of implanted titanium was determined by an electrochemical method. Potential versus current density curves for the cathodic hydrogen evolution reaction indicated that Ni and Mo ions implanted into titanium electrodes resulted in a low hydrogen overvoltage of 110-180 mV (at a current density of 200-400 mA cm^-2 in 30 wt-%KOH at 25°C) and excellent stability. The electrocatalytic activity induced by ion implantation can be explained provisionally by interactions between Ni and Mo ions and the titanium substrate.     

Distribution of misorientations and grain boundary planes in grain boundary engineered brass

Abstract

The present paper reports the application of a five parameter determination of grain boundary types to grain boundary engineered α brass. Approximately 20 000 grains constituted the total sample population, giving rise to more than 77 000 grain boundary line segments. This is the first time that the orientation of a large sample population of grain boundary planes has been measured in a grain boundary engineered material. The most important findings of the investigation were that the distribution of planes showed a prevalence of 〈 110 〉 tilt boundaries, especially asymmetric tilt types, and the presence of 〈 111 〉 twist boundaries. This distribution is a consequence of the low energy of these boundary types. Furthermore, more than three-quarters of boundaries could be considered to be 'potentially special'. The presence of these boundaries greatly fragmented the grain boundary network. This fragmentation is probably a key factor in the development of superior properties in a grain boundary engineered material.     

A static approach towards coke collapse modelling in blast furnace

Abstract

Burden distribution control in a blast furnace has a close relationship with wind acceptance and gas utilisation. Quantification of radial distribution of ore and coke is important for proper control of blast furnace operation. Charging of metallic burden over a layer of coke causes a portion of the coke layer to get dislodged from its original position, similar to the situation observed when a heavy material is dropped on a bed of lighter particles. This phenomenon, designated 'coke collapse', significantly changes the ore/coke distribution in the radial direction and thus affects the permeability of the furnace shaft. In the present work a mathematical model for quantifying the amount of coke collapse has been proposed on the basis of 'stability of slope theory'. The calculation from this model has been compared with the results from experiments in simplified physical models. Predictions of the mathematical model are in good agreement with experimental results.     

Classification of above burden profile using SOM and k-means

Abstract

Blast furnace operators mostly depend on the measurements taken from the inputs and outputs in the control of the process to interpret the information available for vertical and radial distribution of variables, such as, heat load on the boundary and the distribution of the gas across the section of the furnace. Gas distribution inside the furnace is largely dependent on the distribution of the burden inside the furnace and its estimation is a challenge to the blast furnace operators. However, the measurement from the above burden probes gives some insight to the radial gas distribution in the shaft. Design of methods for automatic classification of above burden probe (ABP) profile is thus warranted. The self-organising map (SOM) is an excellent tool in the exploratory phase of data mining. It projects input space on prototypes of a low dimensional regular grid that can be effectively utilised to visualise and explore properties of the data. When the number of SOM units is large, to facilitate quantitative analysis of the map and the data, similar units need to be grouped, i.e. clustered. In the present investigation, a model for classification, visualisation and interpretation of ABP profiles has been developed by two stage procedure, i.e. SOM followed by k-means clustering. This classifier has the potential to be a useful tool for operator guidance in daily practice.     

配电网单相接地故障选线的一种新方法

为了提取故障暂态信号的相位谱特征以进行配电网单相接地故障选线，引入了零序电流解析信号的小波包分解。信号的解析表达形式可以更好地描述信号的幅值、相位和瞬时频率随时间变化的规律；它有着比原信号增大一倍的幅值谱、和原信号相同的相位谱和瞬时频率。小波包克服了小波变换不能对高频序列进一步分解的缺陷，在时域和频域上皆具有良好的局部化特性，可以聚焦被分析信号不同频带的时域特性。通过对构造的零序电流解析信号进行小波包分解，提取在适当频带的信号相位谱，依据故障线路和非故障线路相位谱的不同进行故障选线。理论分析和仿真结果表明：这种基于零序电流解析信号的小波包分解所提取暂态信号相位谱的选线判据具有很高的灵敏性和可靠性。     

Stress analysis and strength evaluation of bonded shrink fitted joints subjected to torsional loads

This paper deals with the stress analysis and strength evaluation of bonded shrink fitted joints subjected to torsion. The stress distributions in the adhesive layer of bonded shrink fitted joints are analyzed by the axisymmetric theory of elasticity when an external torsion is applied to the upper end of the shaft. The effects of the outer diameter and the stiffness of rings on the interface stress distributions are clarified by numerical calculations. Using the interface stress distributions, the joint strength is predicted. In addition, the joint strength was measured experimentally. It is seen that rupture of the adhesive layer is initiated from the upper edge of the interface when torsion is applied to the upper end of the shaft. The numerical results are in fairly good agreement with the experimental results. It was found that the joint strength of bonded shrink fitted joints is greater than that of shrink fitted joints.     

Hot forging of fittings made from seamless pipe

Abstract

The hot forging of connecting fittings known as tees is analysed and described in the present paper. These parts are forged in a vertical press from preforms cut from seamless pipes in which a hole, which will be the third mouth, is cut with an acetylene torch. The process requires that the portion of the preform to be forged is hot enough to allow the flow of material, while the rest of the piece is able to resist the pressure without bending. The experimental work was conducted using instrumented preforms by the insertion of eight type K thermocouples at different portions of the body to record the thermal cycle; a grid was inscribed on the surface of the preforms to compute the various strain components. The pieces were heated and, before forging, were subjected to the standard procedure of immersing the portion opposite to the third mouth in water at room temperature. An attempt to forge one piece directly from heating, without immersion in water, was made, but this was a failure as the material on the lateral wall was not strong enough to withstand the pressure without bending. The microstructure of the forged parts was studied.     

20—THE ASSESSMENT OF SMALL-SAMPLE IRREGULARITY TRACES

Eight methods of determining the coefficient of variation of yarns or slivers when only a limited amount of material is available are discussed. The basic method involves direct measurement and calculation, and each of the other methods is compared with this one, which tends to be somewhat lengthy, for a range of man-made-fibre yams spun on the cotton system. A method based on the use of the cumulative-frequency distribution is shown to be quite the most accurate of the seven methods investigated and has the merit that it can be performed comparatively rapidly.     

低压配电变压器经济运行的几点建议

针对目前全国范围内电力供应紧张而又普遍存在大量浪费电能的现象，提出了关于低压配电变压器经济运行的几点建议。