33—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART II: CYLINDRICAL SNARLING

An account is given of an experimental investigation of the cylindrical snarling of highly twisted monofilaments.

The theory underlying cylindrical snarling is set out, and an expression is derived for calculating the critical twist level at which normal snarling will be replaced by cylindrical snarling. Experiments on rubber filaments are described, and it is shown that there is good agreement between the theoretical and experimental results. Further experiments, in which the specimen was allowed to contract freely or forced into other forms, are also described.

It is shown from these experiments that it is difficult to establish the true equilibrium behaviour, since the situation appears to be dominated by frictional effects or by direct barriers to relative movement.     

32—THE SNARLING OF HIGHLY TWISTED MONOFILAMENTS. PART I: THE LOAD–ELONGATION BEHAVIOUR WITH NORMAL SNARLING

An account is given of an experimental investigation of the normal snarling of highly twisted monofilaments, those used being vulcanized rubber and nylon.

An earlier theoretical analysis is corrected, and the experimental results show that, after this correction, the theory put forward for the mechanical properties of the snarling mechanism holds reasonably well for elastic filaments. Although, as would be expected, there are larger deviations from the theory for viscoelastic filaments, the theory still gives a good indication of the behaviour of these filaments under torsion.     

41—THE RETRACTION AND STRETCH OF WRAPPED ELASTOMERIC-FIBRE CORE YARNS

Equations are given that relate the structure of spirally wrapped elastomeric-fibre core yams to their stretch properties. The model employed improves upon previous ones by considering the effect of covering-yarn diameter. Graphs are given that facilitate the use of the theory for manufacturing purposes.

A comparison with available experimental data indicates an improved agreement between actual and predicted values of retraction in the most important case, where the input and output yarn lengths are measured. It is expected that the improved theory given here will show to much greater advantage with the present commercial fine-core wrapped structures.

In the special case where the wrapping or covering yarns have very low twist, the basic theory is inadequate. Modifications to account for compression of the cover yarn are accordingly included to enable an approximate relationship between yarn structure and stretch to be obtained in this case.     

基于Hadoop YARN的TensorFlow GPU集群的调度扩展

本文研究并实现了大数据平台 Hadoop YARN 与深度学习框架 TensorFlow 的结合。通过对 DRF 算法的扩展,使得 Hadoop YARN 在原先支持 CPU 和内存的基础上,可以对 GPU 资源进行管理和调度。通过 YARN 的应用接口,把 TensorFlow 封装成了 YARN 的应用程序之一,把原来的分布式程序在多节点手动分发启动改为了在单节点自动分发启动,单机版不变。本文设计了多组实验对 YARN+TensorFlow 进行了多方位的测试,实验结果表明 YARN 和 TensorFlow 相结合相比原生 TensorFlow 程序具有相似的加速比,可以满足单系统多用户对 GPU 资源的使用,有效提高 GPU 资源的使用效率和编程人员的工作效率,增加系统的复用率。     

基于Spark+YARN的空气污染预报云平台设计

近年来我国空气污染导致的雾霾天气频繁发生,空气污染已经成为一个亟待解决的重要问题,其数值预报推广应用是一个难题,主要表现在数值预报系统的运行过程中计算量大,数据量大,在传统高性能计算集群中进行空气污染预报存在资源有限、复杂的并行化操作、批处理作业等待耗时等问题,尤其对于资源缺乏的研究团队,还存在基础设施昂贵而无法负担的问题。因此,如何利用有限的资源,为大气科学家提供一种基于云计算模式的高性能计算环境,提供可扩展、快速、廉价和动态可分配的计算和存储资源,是亟待解决的关键问题。研究一种基于Spark+YARN的空气污染数值预报的云平台,针对空气污染数值预报特点,为大气科学家提供一种空气污染数值预报大数据解决方案。     

Effect of Air-Jet Texturing on Adhesion Behaviour of Technical Polyester Yarns to Rubber

Air-jet texturing of technical polyester yarns was performed in order to improve its adhesion to rubber. The air-jet texturing parameters were selected with great care to minimize the mechanical loss. H-adhesion tests were used to characterize the adhesion of the yarns to rubber. A significant increase in the adhesion of dimensionally stable polyethylene terephthalate yarn, textured with an overfeed level of 15% (DSPET15), was recorded, while a decrease in the adhesion of high tenacity polyethylene terephthalate (HTPET) yarn was observed for all overfeed levels. The effects of air-jet texturing on the adhesion of technical polyester yarns were discussed in terms of changes in the yarn geometry and changes on the single fiber surfaces. Changes in the yarn geometry were investigated by optical microscopy studies, while changes on the fiber surface were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) studies. It was observed that air-jet texturing alters both the yarn geometry and the single fiber surfaces, leading to a change in the adhesion to rubber.     

9—THE PROPERTIES OF AIR-TEXTURED CONTINUOUS FILAMENT YARNS

A processing programme is outlined in which yarn pre-twist, applied air-pressure, and supply-yarn overfeed are systematically varied in the air-jet bulking process to investigate their effects on air-textured nylon 6.6 continuous-filament yarns.

Optical magnification of the air-textured yarns enables the average loop sizes and frequencies to be measured. The experimental results are shown to be in general agreement with a suggested mechanism of the process, which argues that the initial filament twist in the parent yarn redistributes itself as snarled loops and that the overfed yarn contributes to the size of such loops; the deflexion of filaments by air-drag forces is also shown to make a contribution to a looping effect, which can be estimated theoretically. Increasing the yam overfeed increases both the loop size and the loop frequency. Increasing the yam pre-twist decreases the loop size and increases the loop frequency. Increasing the air-pressure also decreases the loop size and increases the loop frequency. Experimental and theoretical results are in general agreement.

As would be expected, the only processing condition that effects a change in linear density is the overfeed, but all the processing conditions that have an effect on loop dimensions also have an effect on the change in volume, i.e., on the physical bulk. Overfeed is the greatest single contributor to physical bulk, since both loop size and loop frequency increase with overfeed, occluded air spaces being thereby created in yarn and fabric form; conversely, with varying twists and air-pressures, the effects of decreasing loop size and increasing loop frequency are to some extent self-balancing in their contribution to physical bulk.

It is shown how the various processing parameters affect the stability of air-textured yarns. Textured yams produced from parent yarns possessing small amounts of pre-twist have a high instability because of the lack of binding twist for securing the entangled structure. Increasing the overfeed greatly increases the number and size of loops, and this causes greater instability. Increases in the applied air-pressure also increase the yarn instability. Two new mechanical techniques have been devised to measure the yarn instability, and these have been found to be greatly superior to the stability-testing apparatus normally used, which has serious defects from the viewpoint of accuracy.

The tenacity of the air-textured yarns tends to decrease for increasing values of all the main processing variables considered. Increasing the yarn pre-twist tends to reduce the percentage elongation at break, but independent increases in the supply-yarn overfeed and the applied air-pressure both tend to increase this characteristic. These results are interpreted in the light of the bulking mechanism previously postulated.     

30—YARN HAIRINESS: A SURVEY OF RECENT LITERATURE AND A DESCRIPTION OF A NEW INSTRUMENT FOR MEASURING YARN HAIRINESS

This paper is intended to supplement one published in 1966 containing a survey of the literature on yarn hairiness, and the review of the literature is brought up-to-date at the time of writing.

A new electronic instrument for measuring yarn hairiness is outlined. This apparatus enables three parameters to be obtained directly and simultaneously, these being hairiness, hair length, and yarn diameter.     

A Clamp for the Tensile Testing of Fibre Bundles

A theoretical analysis has been developed in which it has been assumed that the two-stage process that occurs during the relaxation of wool yarns leads to the same change in structure as a single dry-relaxation process. In the present paper, a detailed experimental evaluation of the theory is reported whereby its predictions are compared with results obtained for wool semi-worsted carpet yarns spun at various twist levels.     

Thickness Measurements on Two-fold Worsted Yarns—Reply

A scaled-up model of the air-jet has recently thrown more light on the mechanism of the process and on the construction of bulked yarns of the Taslan type. This in turn has led to a mechanical method of simulating the air-jet action. The simulation of the process has been so effective that yarns of the air-jet-bulked type can now be produced by a novel method that does not use the air-jet. The apparatus is described, together with certain processing requirements found necessary for maintaining product quality.

The new process is analysed mathematically, and comments are made regarding its feasibility as a possible commercial method of making yarns of the air-textured type without using compressed air.