Fretting fatigue tests on shrink-fit specimens and investigations into the strength enhancement induced by deep rolling

The shrink-fit connection undergoes fretting fatigue at the edge of the contact, where both stress concentration and micro-slip take place. A fretting test set-up with a round-shaped specimen is proposed that eliminates lateral edge contact and misalignment, and is also appropriate for deep rolling. Comparative experiments showed a notable strength improvement, induced by deep rolling, along with the beneficial effect of friction reduction due to lubrication. Multiple cracks with clear shallow paths were evident after SEM observation, thus the maximum shear stress amplitude was assumed as a correlating parameter, while the crack arrest was inappropriate especially for deep rolled specimens.     

Robust Mapping for Mobile Robot Based on Immobile Area Grid Map Considering Potential Moving Objects

Mobile robots need Simultaneous Localization and Mapping (SLAM) for autonomous movement in human living environments. The occupancy grid map used in SLAM is a conventional method which makes a map by an occupancy probability in each grid. This method renews a map based on whether an object is observed or not. In order to remove moving objects from a map, an additional method is required. However, conventional methods deal only with actually moving objects, and potential moving objects (e.g., standing humans) are mapped as static objects. Furthermore, only binary states, used or not used, are given to each object in map updating. This paper proposes the immobility area grid map to represent a map by an immobility probability in each grid. The proposed method renews a map based on the identification of observed objects by a robot's sensors, in addition to whether an object is observed or not. We introduce the map update parameter, which is set adaptively from the certainty of identification result of the object. Observed objects can take continuous states, truly static—unknown—truly moving, according to the parameter value. Potential moving objects are not mapped if the parameter takes values corresponding to moving objects. The experimental results show robust mapping in dynamic environments including potential moving objects.     

基于三维胞元空间的MA双向并行路由算法

针对传统移动代理(MA)在监测无线传感器网络(WSNs)的感兴趣信息时产生的延迟较大和能耗较多问题,提出了基于三维胞元空间的MA双向并行(3D-BPMA)路由算法.3D-BPMA将MA与传统的客户/服务器(c/S)模式相结合,在胞元内利用C/S模式搜集信息,在单层胞元系统和路由器与路由器之间采用MA双向并行的策略进行传输.仿真结果表明:3D-BPMA与LCF,DSG-MIP算法相比减少了平均响应时间和网络平均能耗,提高了MA发送率.     

Heat propagation in thermally conductive polymers of PA6 and hexagonal boron nitride

Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant.     

The formation of fibrous structure of polyamide 6 induced by the three-step forming process and its prominent reinforcement in nitrile rubber

Nitrile rubber (NBR) blends with excellent performance have always been a hot research topic in petroleum field. Due to the excellent performance and compatibility of polyamide 6 (PA6), it provides an opportunity for the preparation of high-performance NBR/PA6 blends. In this article, NBR/PA6 blends were prepared by the three-step molding process. Experimentally, it was found that PA6 has a prominent reinforcement effect in NBR matrix. The variation of this mechanical property was investigated from different aspects of the crystal structure, crystallinities, phase morphology, and so on. It can be cleared that the formation of fibrous structure of PA6 phase is the main factor for reinforcement of the polymer blends. Meanwhile, the formation mechanism of the special phase structure induced by the three-step process is deeply expounded and its structural evolution schematic is established. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47472.     

Improved bio-hydrogen production by overexpression of glucose-6-phosphate dehydrogenase and FeFe hydrogenase in Clostridium acetobutylicum

Clostridium acetobutylicum is an attractive industrial microorganism for biochemical production, but there have been few attempts for bio-hydrogen production based on metabolic engineering. In this study, metabolically engineered C. acetobutylicum carrying glucose-6-phosphate dehydrogenase (zwf) and FeFe hydrogenase (hydA) were constructed as recombinant strains CA-zwf(pIMP-zwf) and CA-hydA(pMTL-hydA), respectively, to improve hydrogen productivity. The results showed that the engineered strains produced 1.15 and 1.39-fold higher hydrogen yield, respectively, than the wild type. Furthermore, when pH and glucose concentration were optimized for the CA-hydA strain, enhanced hydrogen productivity of 25.8% was achieved in 7 L jar scale fermentation. This result provides an insight into the future direction for metabolic engineering of C. acetobutylicum for improved hydrogen production.     

基于物联网终端管理云平台的大数据运维

近年来,随着快递物流、新零售、医疗卫生等行业信息化的快速发展,智能移动终端解决方案迅速普及,基于Android操作系统的智能移动终端被广泛应用。企业IT架构不断扩展,同时网络情况变得更加复杂,分支机构众多的大型企业这种情况能加明显。为了保证终端用户的良好体验以及数据的准确性和实效性,终端运维工作愈加困难。在运维过程中虽然已经运用自动化工具,但是管理系统时时采集、加工以及分析数据对运维工作是个巨大挑战。     

新型树启发式搜索算法的机器人路径规划

面对三维空间移动机器人从起始点到终止点的最短路径问题,提出一种新型的边缘点树启发式搜索(TreeEP)算法,该方法将地图空间进行密度可调的三维离散化处理,根据障碍安全距离筛选出障碍物的可靠边缘点信息,再利用树扩散架构选出最能引导搜索方向的潜力点进行扩散搜索,最终得出最短路径。提出局部调整策略,得到改进的Tree-EP算法。实验结果表明,在带障碍复杂地形最短路径搜索应用中,提出的Tree-EP算法与已有方法相比,能找到更短的移动路径。     

基于艾默生DeltaV R6新功能块的设备控制模块开发

利用艾默生控制系统旧版本软件,开发开关量设备控制模块比较繁琐,需要借助大量的逻辑功能块与条件判断功能块进行辅助开发,程序结构复杂,逻辑不清晰,容易出错。新版本软件推出的新功能块解决了以上问题。以某火法铜冶炼工程为例,结合冶炼工艺特点,程序开发过程中通过解决不熟悉新功能块特点应用难问题,风机、泵、电动阀等设备控制模块开发难问题,开发出了满足控制要求的各种设备控制模块。利用新版本软件的新功能块,开发的设备控制模块在火法铜冶炼得到成功应用。     

Next POI Recommendation Based on Location Interest Mining with Recurrent Neural Networks

Journal of Computer Science and Technology - In mobile social networks, next point-of-interest (POI) recommendation is a very important function that can provide personalized location-based...