基于节点多样性的域内路由保护算法

已有的路由保护方案都没有考虑网络中节点的重要程度,然而在实际网络中不同节点在网络中的重要程度是不相同的。针对该问题,提出一种基于节点多样性的域内路由保护算法（intra-domain routing protection algorithm based on node diversity,RPBND）。计算节点构造以目的为根的最短路径树（shortest path tree,SPT）,从而保证RPBND算法和目前互联网部署的路由算法的兼容性;在该最短路径树的基础上构造特定结构的有向无环图（directed acyclic graph,DAG）,从而最大化路由可用性。实验结果表明,RPBND极大地提高了路由可用性,降低了故障造成的网络中断时间,为ISP部署域内路由保护方案提供了充分的依据。     

Distributed observer‐based leader‐follower attitude consensus control for multiple rigid bodies using rotation matrices

This paper addresses the distributed observer‐based leader‐follower attitude consensus control problem for multiple rigid bodies. An intrinsic distributed observer is proposed for each follower to estimate the leader's trajectory, which is only available to a subset of followers. The proposed observer can guarantee that the estimated attitude evolves on rotation matrices all the time, and it provides us with a simple way to design the attitude consensus control law. The dynamics of rigid bodies and distributed observer are both modeled directly on rotation matrices, so that the singularity and ambiguity can be avoided. Furthermore, adopting the idea of disturbance observer on vector space, a gyro bias observer on the rotation matrices is proposed. Based on the distributed observer, three types of attitude consensus control law are proposed, which are respectively on the basis of full‐state, biased angular velocity, and external disturbance combined with biased angular velocity. Finally, the SimMechanics experiments are provided to illustrate effectiveness of the proposed theoretical results.     

Integrated optimization of composite bay door with pre-deformation and variable thickness design

Structural and Multidisciplinary Optimization - The paper presents an integrated design approach of composite bay door with pre-deformation and variable thickness optimization. Firstly, design and...     

Study on the performance of NaBH4 using Ru-Co/CNTs catalyst to catalyze alcoholysis to produce hydrogen

Abstract

Ru-Co/CNTs catalysts are prepared by microwave-assisted heating electroless plating using Carbon nanotubes as Carrier. The structure of the catalyst was analyzed by TEM, XRD, EDS and TGA, and the performance of the catalytic alcoholysis of sodium borohydride was tested. At 25 oC, the carbon nanotube diameter is 10-20?nm, the catalyst dosage is 20?mg, the sodium borohydride concentration is 5?wt.%, and the sodium hydroxide concentration is 7?wt.%, the maximum rate of catalytic hydrogen production reaches the maximum value. At the same time, the activation energy is calculated to be 34.35?kJ · mol-1, which is much lower than the activation energy of spontaneous alcoholysis of sodium borohydride (63.0?kJ/mol).     

纸基碳纳米管薄膜/叉指结构的超灵敏宽量程压力传感器（英文）

柔性压力传感器因其在可穿戴设备和人机交互界面中的潜在应用而备受关注.特别是在实际应用中,人们对具有高灵敏度、宽测量范围和低成本的压力传感器有很大需求.基于此,我们研制出了一种测量范围宽的超灵敏压力传感器.该传感器是以碳纳米管(CNT)均匀溶液直接喷在纸表面作为敏感材料,用光刻技术制成的叉指电极为结构.由于CNT大的比表面积、纸的多孔结构以及CNT与叉指电极有效接触的协同作用,压力传感器实现了从0到140 kPa的宽测量范围,并在15,000个测试周期内表现出良好的稳定性.对于纸基碳纳米管薄膜/叉指状结构(PCI)压力传感器,敏感材料与叉指电极之间的连接区域在较小的压力范围内占主导地位,而敏感材料的内部变化在大的压力区域起主导作用.此外PCI压力传感器不仅具有2.72 kPa-1(直到35 kPa)的高灵敏度,还可以检测小重量,如一颗绿豆(约8 Pa).当压力传感器贴附到人体表面时,可以监测生理信号,如手腕运动、脉搏跳动和语音识别.此外,压力传感器的阵列能够识别空间压力分布,有望实际应用于人机交互界面.     

A novel snail-inspired bionic design of titanium with strontium-substituted hydroxyapatite coating for promoting osseointegration

As the population ages,more and more people are suffering from osteoarthritis (OA),resulting in an increasing requirement for joint implants.Surface modification to improve the topology and compo-sition of the implants has been proved to be an effective way to improve the primary stability and long-term success rate of joint implants.In this work,a bionic micro/nano-structure accompanied with a strontium-substituted hydroxyapatite (SrHA) coating was fabricated on titanium (Ti) surface via elec-trochemical corrosion,ultrasonic treatment,and hydrothermal deposition methods.The in vitro study demonstrated that the bionic structure and the bioactive apatite could synergistically increase the expres-sions of integrin-related gene (ITG α5β1) and osteoblastic genes (Col-I and OCN),and thus promote osteoblast growth.In addition,owing to the anti-bone resorption property of Sr2+,the coating could effectively inhibit osteoclast differentiation and proliferation.In a word,the prepared samples not only promoted osteogenesis but also inhibited osteoclastogenesis.The in vivo experiment via a rabbit model found that the bionic structured surface provided the pore for new bone ingrowth,which was beneficial to the mechanical interlocking between the implant and bone.Moreover,the bionic structure and bioactive SrHA coating had a synergistic effect on promoting bone formation,osseointegration,and bone-implant bonding strength.This study therefore presented a new strategy to fabricate bio-functionalized Ti-based implants for potential application in orthopedics field.     

Effects of strain rates on dynamic deformation behavior of Cu-20Ag alloy

Copper alloy is widely used in high-speed railway,aerospace and other fields due to its excellent electri-cal conductivity and mechanical properties.High speed deformation and dynamic loading under impact load is a complex service condition,which widely exists in the field of national defense,military and industrial application.Therefore,the dynamic deformation behavior of the Cu-20Ag alloy was inves-tigated by Split Hopkinson Pressure Bar (SHPB) with the strain rates of 1000-25000 s-1,high-speed hydraulic servo material testing machine with the strain rates of 1-500 s-1.The effect of strain rate on flow stress and adiabatic shear sensitivity was analyzed.The results show that the increase of strain rate will increase the flow stress and critical strain,that is to say,the increase of strain rate will reduce the adiabatic shear sensitivity of the Cu-20Ag alloy.The Cu-Ag interface has obvious orientation relationship with (111)Cu//(111)Ag;((1)11)Cu//((1)11)Ag;((2)00) Cu//((2)00)Ag and[0(1)1]Cu//[0(1)1]Ag with the increase of strain rate.The increase of strain rate promotes the precipitation of Ag and increases the number of interfaces in the microstructure,which hinders the movement of dislocations and improves the stress and yield strength of the Cu-20Ag alloy.The concentration and distribution density of dislocations and the precipitation of Ag were the main reasons improve the flow stress and yield strength of the Cu-20Ag alloy.     

Achieving stem cell imaging and osteogenic differentiation by using nitrogen doped graphene quantum dots

Nitrogen doped graphene quantum dots (N-GQDs) were synthesized to explore and extend their potential applications in biomedical field. The hemocompatibility and cytotoxity of the obtained N-GQDs were primarily assessed at concentrations ranging from 10 to 100?μg/ml. From the results, it was found that the proliferation of rat Bone Mesenchymal Stem Cells (rBMSCs) was depressed to a certain extent after incubating with the high concentration (100?μg/ml) of N-GQDs. The nanoscale size and superior dispersibility endow N-GQDs with good cell permeability. Meanwhile, owing to their intrinsic photoluminescence characteristic, the N-GQDs can be used to label cells with high uniformity and light stability in absence of chemical dyes. More importantly, the up-regulated expression of alkaline phosphate (ALP), extracellular matrix, osteopontin (OPN) and osteocalcin (OCN) in rBMSCs cultured with N-GQDs, indicating N-GQDs have the abilities to promote rBMSCs osteogenic differentiation. This work would help give a new insight into the advantages of N-GQDs and pave the way for application of N-GQDs in regenerative medicine fields.

Open image in new window