Ground demonstration system based on in-orbit assembly oriented manipulator flexible force control

To eliminate the load weight limit of carrier rockets and reduce the burden on support struc-tures,in-orbit assembly is a key technology to make design of scattering a large diameter telescope into submirror modules, which requires smooth operation of assembly robots, and flexible force con-trol technology is necessary.A ground demonstration system is presented for in-orbit assembly focu-sing on flexible force control.A six-dimensional force/torque sensor and its data acquisition system are used to compensate for gravity.For translation and rotation, an algorithm for flexible control is proposed.A ground transportation demonstration verifies accuracy and smoothness of flexible force control, and the transportation and assembly task is completed automatically.The proposed system is suitable for the development of in-orbit assembly robots.     

Studies on induction hardening of powder-metallurgy-processed Fe-Cr/Mo alloys

Induction hardening of dense Fe-Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2-3 s. A case depth of 2.5 mm was achieved while maintaining the bulk (interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C.     

Wnt/β-catenin信号途径在DDR和氧化应激中的作用

Wnt/β-catenin信号途径在调控基因表达与DNA损伤反应(DNA damage response,DDR)中具有重要作用.氧化应激是导致DNA损伤的主要原因,且可以影响Wnt信号.首先总结了Wnt/β-catenin信号途径和DDR,然后综述了Wnt/β-catenin信号途径在DDR和氧化应激中的作用及分子机制,以期为DNA修复缺陷性肿瘤提供更有效的治疗策略.     

嵌入式设备在中小型机房监测中的应用

针对中小型机房设备实时监测的需求，设计一种低成本机房监测系统。本文主要阐述嵌入式设备在该系统中应用。嵌入式设备采用S3C44BOX处理器，通过温湿度传感器、烟感、UPS协议采集机房相关监测数据；嵌入式软件采用互换性好的模块化设计。整个系统设计简单，性能可靠，易于安装，经济实用。     

三螺杆挤出共混聚酰胺66/聚苯醚的工艺参数优化分析

基于具有高黏度比的聚酰胺66/聚苯醚共混体系，研究了倒三角排列的三螺杆挤出机（TTSE）的工艺参数对共混物混合效果的影响。通过Box-Behnken响应面设计并分析实验结果，发现螺杆转速、产量和分散相占比对共混效果均有一定影响，通过工艺优化能够获得良好的分散效果；通过对比相同工艺下三、双螺杆挤（TSE）出机的共混效果，证明了拉伸流场对于共混效果和材料性能有明显的改善。     

环境剧变、文化断裂与伊克化

人类生存繁衍的过程,是一种环境适应和自身发展的过程.人与环境的相互作用产生了文化,文化是人地关系的一种结果和文明的最高表现形式.一个人群生存的地理环境剧变,传统文化骤断,可能导致该人群的心理孤独和精神蜕变,进而出现"伊克综合症".快速城市化过程则会加重伊克效应.中国在"文化大革命"前后和改革开放之后,先后经历了文化突变和地理环境的剧烈变迁,如今又进入了快速城市化阶段.大量社会现象表明,中国部分人群出现了伊克化的不良征兆.如果不能及早认识伊克化的严重后果并考虑应对策略,则伊克化过程将与城市化过程一起,诱发中国社会的畸形成长以及地理空间上的病态格局.     

光限制胁迫协同pH与氮磷比对铜绿微囊藻生长的影响

以铜绿微囊藻为试验材料,应用正交试验法,在培养温度(25℃)及接种量相同的情况下,研究光限制胁迫协同pH与氮磷比对铜绿微囊藻生长的影响.影响铜绿微囊藻生长的因素顺序为:pH>光限制胁迫天数>氮磷比,pH为铜绿微囊藻生长的显著性影响因素(F=63.111 5),且在pH 10.5、氮磷比15∶1及光限制胁迫5 d的条件下正常光照培养4 d后藻细胞数量最大.     

AB变频器、PLC及上位机的以太网通讯

本文以宁夏钢铁烧结配料自动化系统工业以太网为例,介绍了AB品牌1756 ControlLogix系列PLC同Flex系列远程I/O、PowerFlex系列变频器的通讯组态,及PLC同上位机Factorytalk SE软件之间的以太网通讯。并比较了EtherNet/IP通讯协议与其他现场总线及Factorytalk SE与其他品牌HMI软件在画面开发方面的优略。     

TCP/UDP下一种网络透明传输服务编程接口实现方法

使用在TCP/UDP协议进行网络通信,会涉及IP地址、端口号、套接字、TCP/UDP协议等网络通信概念,而且TCP传输和UDP传输的编程模式是不同的,对网络通信概念进行了封装,实现了一个网络通信透明传输服务系统,且TCP传输和UDP传输具有相同的编程模式.使用表明,用户无需了解网络通信概念,即可使用该系统进行通信编程,...     

让历史重返自然——当代STS的本体论研究

从逻辑经验主义到社会建构的发展中,自然的历史性始终未能进入研究者的视野。认识论的鸡之争使拉图尔提出了广义对称性原则,这一原则使自然的历史性以一种全新的面貌再现,使STS走向了新自然辩证法的本体论研究,这种本体论表明客体之所以能成为科学的,是因为它是在辩证的实践过程中生成的;客观性与真理等一系列认识论范畴也不是对预先存在对象的表象性反映,也是在历史与时间进程中生成的东西;科学是一个人与物、自然与社会共同进化的过程。