Φ508mm 厚壁无缝钢管RTS-300型超声波自动化探伤机组简介

介绍了成都无缝钢管厂Φ508mm无缝管RTS－300型超声波自动化探伤机组的结构、特点，以及该机组对Φ119mm×16mm，Φ245mm×40mm，Φ508mm×13mm无缝管样管进行探伤试运行的情况。     

热压烧结AlN-BN复合陶瓷的制备及介电性能

用热压工艺制备一系列BN含量(质量分数)为0~30%的AlN-BN复合陶瓷材料,研究了三氧化二钇和碳酸钙添加剂对致密性及介电性能的影响。结果表明:三氧化二钇和碳酸钙均有促进瓷体致密化的作用,但碳酸钙含量增加会造成组分不均匀,介质损耗增加。BN的质量分数为20%、三氧化二钇质量分数为5%的条件下,获得相对介电常数为8.5、介质损耗为0.000 683(1 MHz下)的AlN-BN复合陶瓷材料。测定了复合陶瓷介电常数及介质损耗随频率 (0.01~1 MHz)变化的特性,探讨了复合陶瓷介电常数与介质损耗与制备工艺的关系。     

AlN-W复相微波衰减材料的性能研究

以AlN和W为原料，Y2O3为烧结助荆，1850℃、N2气氛下热压烧结制备AlN-W复相衰减材料。运用XRD、SEM和矢量网络分析仪对AlN-W复相衰减材料的相组成、显微结构和衰减性能进行表征。研究了W含量对AlN-W复相衰减材料烧结性能与微波衰减性能的影响。结果表明，烧结性能随W含量的增加而变差；衰减量随W含量的增加而增加。W含量小于10wt％时呈现选频衰减；W含量10wt％-40wt％，呈多点选频衰减；W含量达到50wt％时，表现较好的宽频衰减。初步探讨了AlN-W复相材料微波衰减曲线的频谱特性与衰减机理。     

碳热还原法合成AlN纤维

研究了碳热还原法合成AlN纤维过程中原料配比、合成温度、保温时间、氮气压力、氮气流量等因素对氮化率的影响,实验结果获得了较佳的工艺参数,研制出直径为4～6 μm、长径比为20～30、氮含量大于31%的氮化铝纤维。     

Micro-spike EEG electrode and the vacuum-casting technology for mass production

An innovative dry electroencephalography (EEG) electrode has been successfully designed and tested, in which multiple micro-spike electrodes, each of them consisting of a micro-pillar with a micro-tip on top of it, were designed to pass through the hairs and establish electrical conduction at the skin-electrode interface by penetrate into the stratum corneum of the skin. For hygiene reasons, such electrodes should be made disposable, at the same time, should be cost effective. Therefore, a mass production technology, including the processing methods, such as casting, has to be designed and developed. In this project, the micro-spike dry electrodes were fabricated by a vacuum casting method using a master pattern piece made by CNC micro-machining, in which silicone rubber moulds are created and then used to vacuum cast polyurethane (PU), epoxy or epoxy-carbon micro-spike electrodes. In order to obtain a harder polymeric material, varying amount of carbon fillers were added to the epoxy resin, and the hardness of the resulting material were measured and compared. It was found that a higher concentration of added carbon fillers resulted in a harder cast polymer composite. Further to the vacuum casting, to create an electrically conductive layer on the vacuum-casted electrode, an Ag/AgCl electroless deposition method has been developed. The sputtering of the conductive layer was also carried out for comparison. The developed micro-spike electrodes showed better performance in terms of the impedance level and stability as well as a much higher efficiency in EEG measurement.     

The Application of Neural Networks in the Prediction of Spring-back in an L-Shaped Bend

The purpose of this work is to establish an effective prediction of the spring-back of material during the processing of an L-shaped bend. FEM-simulation of an L-shaped bend is carried out for various thicknesses of material, various punch-round-radii and die-round-radii. The spring-back depends on the shape of the bend-die and the mechanical properties of the material. The results of spring-back from FEM-simulation are then input to a neural network to establish a model for the L-shaped bend variables. The neural network is composed of a number of functional nodes. Once the L-shaped bend para-meters (material thickness, punch-round-radius and die-round-radius) are given, the bend processing performance (spring-back) can be accurately predicted by this developed network. A simulation annealing (SA) optimisation algorithm with a performance index to obtain a perfect L-shape can search for the optimal bend processing parameters. A satisfactory result was achieved based on a demonstration of simulation and on practical experience, showing that this is a new and feasible approach for use in the control of spring-back of materials.     

Plane wave reflection and refraction involving a finitely conducting medium

In this work the structure of electromagnetic field in a lossy conducting medium is studied in detail. The meaning of the complex angle of refraction is explained in terms of real parameters involved in this problem. The concepts are illustrated with a wave refracting from air into pure water at a frequency of 95 GHz and an incidence angle of 60/spl deg/. The approach is similar to that used to derive refraction in many electromagnetic textbooks, such as Stratton (J. A. Stratton, 1941), which has been cited in many of the textbooks published since. Our results agree with his for the real angle of the equiphase surface of the refracted fields, but we explore further subjects, including the instantaneous and time-averaged Pointing vectors.     

复杂变断面锻件辊锻成形的金属流动

本文针对复杂变断面锻件在辊锻成形过程中的变形特征及金属流动规律,通过辊锻成形理论并结合实例进行了分析,对不均匀变形:变形过程中断面各部分金属相互牵制及相互转移,断面各部位变形的导前与滞后、辊锻件在变形过程中的稳定条件、影响金属填充的各因素等问题进行了理论分析与探讨,并提出了相应的技术措施。     

A method that preserves circulation during preparation of the pectoralis major myocutaneous flap in head and neck reconstruction

The present article describes a method that preserves circulation during the preparation of the pectoralis major myocutaneous flap used in head and neck reconstruction. The major disadvantage of this flap is its poor circulation and consequent partial necrosis. To solve this problem, we analyzed the circulation and hemodynamics of the pectoralis major myocutaneous flap (the perforator of the anterior intercostal branch located about 1 to 2 cm medial to the areola in the fourth intercostal space is important), evaluated the safe donor sites in the chest wall for a skin island (the perforator is included on the skin island's central axis), improved the surgical procedure for elevating flaps (for preventing perforator injuries), and devised a means to transfer flaps, thereby increasing the range of the flaps (the transfer route is under the clavicle). Using this technique, head and neck reconstruction was performed on 62 patients. The diagnosis included oral cancer (21), oropharyngeal carcinoma (10), parotid carcinoma (10), hypopharyngeal carcinoma (9), and other head and neck malignant tumors (12). Of these, partial or marginal necrosis of the flap caused by circulatory problems was detected in three patients (5 percent). Using our method, the problems associated with inadequate circulation in the pectoralis major myocutaneous flap were greatly alleviated, thus reconfirming the usefulness of this flap in head and neck reconstruction.