A new sheet metal forming system based on incremental punching, part 2: machine building and experiment results

The paper is the second of the two papers on a new sheet metal forming system of incremental punching. In the first paper, the mechanics model is introduced, and the computer simulations are carried out. This paper consists of two parts: the design and building of an incremental punching machine and experiment results. The machine is a three-axis computer numerical controlled (CNC) machine with a high-speed hydraulic punching head. Given a part, the punch path can be generated using commercial CAM systems with some modifications. Then, the machine takes over forming the part punch by punch. The formability of this system is also investigated giving the maximum forming angle. Following the first paper, two examples are studied in details. The experiment results indicate that the new system is effective for sheet metal rapid prototyping. Finally, some future research topics are discussed.     

GCSQX-01型高侧石中央隔离带清洗车

<正>公路中央隔离带的清洗一般是由人工或使用简单清洁设备来完成的,劳动强度大、作业效率低、清洁效果不明显。钢制隔离带通常是由波形板与钢管铆接而成的,截面规则,灰尘附着在隔离带表面,一般的护栏清洗车就可以将其清洗干净。而高侧石隔     

CS夹芯板抗弯性能的试验研究

通过CS夹芯板抗弯性能的试验,重点研究织物加强对改善夹芯板抗弯及抗裂性能的作用。试验研究表明,织物加强的CS夹芯板具有很好的抗弯抗裂性能。并根据受弯机理分析,提出相应的开裂弯矩和极限弯矩计算公式,计算结果与试验结果吻合较好。     

"电工电子学"课程教学改革的探索与实践

"电工电子学"是高等工科院校非电专业的一门重要技术基础课.针对学生基础差异大、学时数量有限等课程特点,江苏大学从教学实际出发,整合、优化教学内容,采用多元化的教学模式以及加强实践教学等一系列改革措施,把更多、更新、更广的内容融入课堂和实践教学中,取得了良好的教学效果.     

大入地短路电流造成发电厂局部电势超标的研究

新建大型发电厂单机容量超过GW,投网运行台数超过2台.若厂区内发生不对称接地短路故障,则可能入地电流过大,造成设计人工接地装置接地电阻值大于A类电气装置允许接地电阻值上限;且校核局部接触电势和跨步电势超出设计规范要求.因此,根据实际工程特点,提出局部增设小网孔水平均压带且铺设砾石提到地面电阻率.结果方案满足工程设计标准.     

The application of recurrence plot in DC tracking test of gamma-ray irradiated polycarbonate

Irradiation effects on tracking resistance of polymer insulation materials should be investigated due to the increasing usage in radiation-prone environments. This paper presents a study on dc tracking resistance of gamma-ray irradiated polycarbonate mixed with polyethylene by use of IEC 60112 method. The samples were irradiated in air up to 100 kGy and 1000 kGy with a dosage rate of 10 kGy/h using a /sup 60/Co gamma source. Because the data of tracking resistance obtained from the tracking test has a wide variation, discharge current in the test is considered as a main factor to estimate the tracking resistance. A recurrence plot analysis of discharge current has been made to evaluate the tracking resistance more consistently. Obtained results showed that after gamma-ray irradiation, the tracking resistance was improved compared with that of the unirradiated sample. The tracking resistance showed an increasing tendency from 0 kGy to 100 kGy but a decreasing tendency from 100 kGy to 1000 kGy. There was a threshold value for the tracking resistance around 100 kGy, which was related to the reaction of cross-linking and degradation. The topological structures of the recurrence plots with the irradiated samples were different from that of the unirradiated one. There were bigger white space segments, which indicated that there were high amplitude transients in the discharge currents of unirradiated sample. The recurrence point density increased from 100 kGy to 1000 kGy, which suggested that the discharge process of the total dose at 1000 kGy was more intensive than that at 100 kGy. The irradiation effects on the tracking resistance can be visually identified by the recurrence plot.     

A DC Signal Injection-Based Thermal Protection Scheme for Soft-Starter-Connected Induction Motors

This paper proposes a remote and sensorless thermal protection scheme for soft-starter-connected induction motors. A dc signal injection-based method is used to estimate the stator winding resistance and, thus, the stator winding temperature. Based on continuous monitoring of the stator winding temperature, a thermal condition monitoring and protection scheme is proposed using only the motor's input voltages, currents, motor nameplate information, and the ambient temperature. An adaptive Kalman filter is designed to reduce the stator winding temperature estimation error. In addition, the influence of the cable resistance was investigated, and a compensation method is suggested to improve the accuracy of the estimated temperature. The requirements of the data acquisition system, such as sampling frequency and analog-to-digital conversion resolution, and their affects on the accuracy of the estimated temperature are also discussed in detail. The proposed thermal monitoring scheme has been validated from the experimental results of a 7.5-hp TEFC induction motor under various load conditions. The importance of this new thermal monitoring scheme lies in its remote and sensorless nature.     

计算全息干涉实现防伪和信息的加密存储

提出一种位相编码计算全息干涉防伪术。这种方法用迂回位相法对光波进行位相编码,然后用这个编码的光波和另一由计算全息产生的参考光波干涉,从干涉图样中可以读出所记录的信息,没有参考计算全息图则无法读出记录的信息。这种计算防伪全息图的特点是设计灵活、使用方便、可由白光再现。具有很强的防伪力度。     

铝衰减膜表面氧化对软X光透过率的影响与修正

对用不同方法制备的软Ｘ光激光实验用的Ａｌ衰减膜样品,用Ａｕｇｅｒ电子能谱（ＡＥＳ）结合氩离子束刻蚀进行了组分的表面和深度分布分析,结果表明表面氧化层主要由Ａｌ２Ｏ３组成,氧化达到饱和时的氧化层厚度≈７．５ｎｍ。由于在软Ｘ光波段内,氧的吸收系数比铝大一个多数量级,这一氧化层对软Ｘ光透过率的影响甚大。将ＡＥＳ测试结果作为参数,使用公式Ｉ＝Ｉ０·ｅｘｐ［－μ（Ｅ）·（ρｄ）］对Ｘ光透过强度进行修正。同步辐射软Ｘ光对样品透过率的直接测量表明,对于透过率大于２０％的Ａｌ膜,直接测量结果与按修正公式计算的结果在最大偏差１１％范围内符合。