The influence of cyclic deformation on the strength and elongation at break of carded and combed wool yarns

There are various factors that influence yarn strength. Yarn breaking is due to fiber breakages and fiber’s slippages. In reality, a part of the fibers slip while the other part breaks. In this study, we have shown that fatigue yarn, resulting in a fundamental way impact on the number of breaks on the weaving machine, and sometimes on the physical properties of fabrics. Given the importance of the issue and the very limited directed research number in this direction, a tests series were carried out with the aim to highlight the changes to the physical characteristics of the yarn resulting from mechanical treatment comparable to that which they are subjected on the weaving machine. In the first part of our investigation, the residual deformation, tensile strength, and elongation at break of combed and carded threads were measured. In the second part, the influence of the extensions number, their amplitudes, and frequencies were analyzed. In order to examine the influence of these parameters, carded and combed yarns, with different characteristics were prepared. Therefore, based on the separate treatment results of three test series, it appears that: the warp yarns subjected to repeated extensions undergo the phenomenon of fatigue. Yarns fatigue reduces their elasticity and resistance and it is the cause for break yarn during weaving. The fatigue of wool yarns is very low compared to other textile materials.     

Metabolically blocked analogs of housefly sex pheromone: II. Metabolism studies

Analogs of (Z)-9-tricosene (Z9–23: Hy) bearing methyl substituents, cyclopropyl groups, fluorine substituents, and additional double bonds were used to probe the substrate requirements for the monooxygenase system that converts Z9–23: Hy to the corresponding epoxide and ketone. Three of the seven analogs tested, 10-fluoro-(Z)-14-tricosene, 10,10-difluoro-(Z)-14-tricosene, and 14-methyl-(Z)-9-tricosene, were metabolized to the corresponding epoxide. Compounds with two methyl groups, a cyclopropane group, a hydroxy group, or an additional double bond at the 14 position were not epoxidized at the 9,10 position. This suggests that only minimal structural change at the 14-position of Z9–23: Hy is allowed with retention of metabolic activity. None of the analogs tested were hydroxylated at the position equivalent to the 14 position of Z9–23:Hy. Of the 13 analogs tested as inhibitors of Z9–23:Hy metabolism, the two compounds that were the most effective inhibitors in both male and female houseflies were (Z)-14-tricosen-10-one and 1-nonyl-1-[(Z)-4-tetradecen-1-yl]-cyclopropane. These data show that the poly substrate monooxy genase that metabolizes Z9–23: Hy in the housefly has very strict structural requirements for the substrate.     

Infiltration and Top Seed Growth-Textured YBCO Bulks With Multiple Holes

The recently reported hole-patterned YBa₂Cu₃O _y (Y123) bulks with improved superconducting properties are highly interesting from material quality and application variety points of view. It is well known that the core of plain bulk superconductors needs to be fully oxygenated and some defects like cracks, pores, and voids must be suppressed in order that the material can trap a high magnetic field or carry a high current density. To minimize the above defects, we have used a combination of standard superconducting ceramic processing and an infiltration technique to prepare regularly perforated YBa₂Cu₃O _y (Y123) bulk superconductors. This process leads to negligible shrinkage upon annealing and a uniform distribution of Y211 inclusions. Texture was evidenced by neutron pole figure measurements. Flux mapping was used to verify the superconducting homogeneity of the samples and to investigate the field-trapping ability. In addition, the textured drilled samples were reinforced using resin or metal impregnation and the influence of the different processing steps on the hardness of the materials has been investigated.     

Classic and local analysis of corrosion behaviour of graphite and stainless steels in polluted phosphoric acid

In phosphoric acid solution (40% H₃PO₄), the corrosion behaviour of graphite and stainless steels was studied by the use of different electrochemical methods, namely polarization curve analysis, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The combined effect of chemical impurities and the increase of medium temperature was studied to approach the real conditions in the process of phosphoric acid manufacturing. It was found that the current density measured by polarization curves increased with the presence of chloride and sulphate ions in the acid solution whatever the tested material. Compared to stainless steels, graphite had the best corrosion resistance in polluted phosphoric acid. However, for graphite the increase of temperature from 20 to 80 °C induced an increase of the corrosion rate and potential and a decrease of the resistance confirmed by EIS results. Subsequently, local currents were detected at the surface of the sample by using the scanning vibrating electrode technique. From the data obtained, graphite surface manifested a distinctive behaviour from that of stainless steels. A generalized corrosion was occurred on graphite whereas a localized corrosion was observed for stainless steels. These results show a clear interest of graphite as component material in some of the equipments of the phosphoric acid industry.     

Influence of disbond on notch crack behaviour in single bonded lap joints

The behaviour of the adhesive bonded joints due to the imposed eccentric loading generates a very complex distribution of the stress in the structure. Good adhesion between substrate and adhesive ensures a successful and lasting assembly. In this study the finite element method is used to analyze the behaviour of a bonded lap joint of dissimilar materials. The effects of the mechanical properties of the joints on the shear stress variation with and without presence of a circular notch are investigated. The results show that the maximum shear stresses are located at a distance of about 18% that of the lap length whatever the type of material used. In addition, the stress intensity factor is amplified by the presence of the negative effect of disband whose increase is linearly proportional to the square of the stress intensity factor. It reached its maximum value for a crack length equal to two-fifths of the notch radius.     

A CAD tool for an array of differential oscillators coupled through a broadband network

A new expression of the equations describing the locked states of two oscillators coupled through a resistor is presented in this article. This theory has led to the elaboration of a CAD tool which provides, in a short simulation time, the frequency locking region of two coupled differential oscillators. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Evaluation of corrosion behaviour of a new class of Pb‐free solder materials (Sn‐In‐Zn)

In view of the need for a lead‐free drop in replacement for the widely used 40Pb‐60Sn near eutectic solder, new Sn‐In‐Zn based alloys with substantially the same melting point have been developed. The corrosion resistance and the influence of zinc content on electrochemical behaviour of some special alloys Sn‐In‐Zn in 3% NaCl solution has been investigated using electrochemical techniques. The good resistance of this ternary system is confirmed. In decreasing dissolution rate, they are ranked as follows: 40Pb‐60Sn, Sn‐10.6In‐27Zn, Sn‐11In‐23Zn and Sn‐13In‐12Zn. The increase of zinc content induces a decrease of corrosion resistance of ternary Sn‐In‐Zn alloys. So, the Sn‐In‐Zn system with low indium and zinc concentrations might be a good candidate for solder materials and present a good corrosion resistance.     

中国住房改革的社会影响--基于计算机技术的社会形态分析

市场经济体制改革以来,中国城市的外在形象和内部结构都发生了巨大的变化。住房市场化为普通居民提供了选择住房的机会。但是,并不是所有的百姓都从住房再分配中受益。中国城市中的住房再分配与居民在政府再分配和市场回报之间的位置联系密切,这种联系超过了成熟市场中因生活圈及其改变衍生出的住房需求。本文研究了宁波老城再开发地段当地居民的满意度,着重从社会方面分析,主要涉及住房再分配对居民的影响及其导致的潜在住房问题。研究以一份调查问卷为基础,调查了在过去15年内三个不同时期进行改造的社区。调查数据表明三个社区的满意度都不高。由于各阶层人们的努力,保护老城内综合环境的同时也要提高当地居民生活质量的新策略被采纳。然而,为改变人们的观念还有很多工作要做:通过报纸获得信息和教育,通过学术旅行和会议进行学术讨论,对决策人进行汇报,进行小规模改善的实践。住宅搬迁正在成为有争议的话题。因此,住宅再分配是市场体制下城市空间改变的一种过程。     

Evaluating Regression Models for Temporal Prediction of Wi-Fi Device Mobility

Wireless Personal Communications - The ability to predict the arrival and residence time of mobile users at a particular place is essential for the development of a wealth of new applications and...     

Spread spectrum in three-phase inverter by an optimised dual randomised PWM technique

Randomised pulse width modulation (RPWM) technique has become a viable alternative to deterministic pulse width modulation (DPWM). By spreading the power spectrum in a continuous noise, this new technique better complies with electromagnetic compatibility (EMC) requirements for conducted electromagnetic interferences (EMI) and allows reducing the emitted acoustic noise in variable speed drives (VSDs). The most popular RPWM schemes are randomised pulse position modulation (RPPM) and randomised carrier frequency modulation (RCFM). The combination (RCFM-RPPM) or dual RPWM (DRPWM) has also been proposed. In this article, we propose an optimised DRPWM (ODRPWM) for the three-phase inverter. First, the modulating principle is proposed, and then, a mathematical model of power spectral density (PSD) of the output voltage is developed and validated for the three schemes, namely RPPM, RCFM and RCFM-RPPM. PSD analysis shows that the proposed scheme is more effective on spreading PSD. Moreover, this analysis reveals optimal parameters of randomisation for a maximum spread of the PSD. The optimisation problem is then modelled and solved using two powerful non-linear methods.