W-Grid: A scalable and efficient self-organizing infrastructure for multi-dimensional data management,querying and routing in wireless data-centric sensor networks

Data-centric sensor networks are advanced ad hoc networks that act like a distributed database managing and indexing sensed data in order to efficiently perform advanced in-network tasks, such as routings, searches, data processing, fusion and analysis. The supplied distributed services, such as routing, content location and information sharing should be provided anywhere and at any time optimizing energy consumptions, computational resources, memory occupation and radio transmissions. Moreover, the network traffic should be equally balanced among participants in order to avoid premature discharge of some devices that may partition the network. This work describes a fully decentralized infrastructure able to self-organize nodes in ad hoc networks by exploiting local interactions and topology learning among devices. In this solution all nodes are peers and nothing prevent the approach to be used in wireless mesh networks as well. Differently from existing solutions, our proposal does not require global information or external help, such as the Global Positioning System, which works only outdoor with a precision and an efficacy both limited by weather conditions and obstacles. The infrastructure natively enables devices to perform routing and data management without using message broadcast/flooding operations. The work introduces also a feature, called full learning, that improves routing performances while balancing the traffic among devices. We report an extensive number of simulations comparing the new solution results with four existing proposals, two of which deriving from preceding versions of the infrastructure.     

Single phase A_2B_7-type La-Mg-Ni alloy with improved electrochemical properties prepared by melt-spinning and annealing

La-Mg-Ni alloys were prepared by melt-spinning with different cooling rates and followed by annealing.Elevation of the cooling rate leads to refinement of the grains size and increasing of the abundance of LaNis.Annealing is favorable to formation of the A_2 B_7-type phase and promotes the discharge capacity,cycling stability and high rate discharge ability of the as-spun alloys.Phase constitution of the annealed alloys is found to be closely related to the microstructure of the as-spun alloys.A single phase A_2 B_7-type microstructure is obtained in the annealed alloy which is attributed to the lower abundance of the LaNis of the original alloy spun with lower cooling rate.Formation of the single phase A_2 B_7-type microstructure is also ascribed to the isolated and homogeneous distribution of the morphology of the as-spun alloy.The single phase alloy presents higher discharge capacity and better cycling stability compared with other annealed alloys.     

VIBE: An energy efficient routing protocol for dense and mobile sensor networks

We present a new protocol that manages wireless sensor networks in several scenarios including large scale, high density and high mobility deployments. An example of one of the main applications is to communicate important information from inaccessible areas by spreading “enough” mobile sensors which must self-configure and assemble. According to our protocol, virtual infrastructure-based energy-efficient (VIBE) routing, the information is routed in a multihop, cluster level fashion by enabling each sensor to make individual decisions regarding its mode of operation. The aim is to prolong the network's lifetime by minimising the average energy spent for each communication. VIBE is capable of addressing mobility requirements as it is completely independent of any kind of topological knowledge and control messages. We show by extended experiments that VIBE performs very well in terms of consumed energy by comparing it to standard directed flooding and greedy forwarding protocols. We also compare it to LEACH (Rabiner Heinzelman et al., 2000) and a more recent protocol, namely MECH (Chang and Kuo, 2006). VIBE proves to save large amounts of energy when compared to the first three and up to 15% compared to MECH.     

多相流管线内腐蚀直接评价方法在国内的现场应用

目的 通过研究美国腐蚀工程师协会（NACE）于2016年提出的适用于多相流管线的内腐蚀直接评价标准SP0116-Multiphase flow internal corrosion direct assessment methodology for pipelines（以下简称MP-ICDA）,探究该评价方法在国内的现场应用步骤,为国内内腐蚀直接评价方法提供参考。方法 以我国东海某海底管线的实际运行工况为基础,建立Norsok M506内腐蚀预测模型,利用流体动力学理论,模拟分析管线内腐蚀状况,结合评价标准的预评价、间接检测、详细检查及后评估四个步骤进行内腐蚀直接评价。结果 管线整体内腐蚀速率超过0.25 mm/a,腐蚀程度较严重。管道1.5~2.5 km低洼处及两侧立管处腐蚀速率明显增大,其腐蚀高危点与段塞流动状态、高持液率等流动参数有关。现场在线检测数据与模型预测结果基本一致,由此证明了模型的可靠性。根据腐蚀程度等级及标准规定的内腐蚀再次评估周期,确定管线再评估时间间隔为1年。结论 ICDA能够准确预测管线内腐蚀状态与风险大小,为无法实施内检测的管线提供了有效的内腐蚀评估方法,其对预测多相流管道腐蚀发生的位置与风险等级具有一定的指导作用与借鉴意义。流体的动力学参数对腐蚀速率影响较大,应用MP-ICDA方法时应选取合适的内腐蚀预测模型及管线运行参数。在海底管线正常运行期间,可对ICDA的结果进行多次循环校核,从而提高腐蚀预测的准确程度。     

Fabrication of ultrahigh hydrogen barrier polyethyleneimine/graphene oxide films by LBL assembly fine-tuned with electric field application

In this study, layer-by-layer self-assembly of polyethyleneimine (PEI)/graphene oxide (GO) was successfully controlled by an applied electric field. The influences of the applied electric field direction, voltage, and dipping time on the hydrogen barrier properties of PEI/GO self-assembled film were investigated. Ultraviolet–visible light absorption spectroscopy, ellipsometry, atomic force microscopy, and scanning electron microscopy were used to analyze the effects of the electric field on the growth, nanostructure, and micromorphology of the self-assembled film. Results indicated that an applied electric field accelerates the adsorption rate of assembly and increases the GO adsorption quantity. Additionally, such electric field modifies the composite structure of the self-assembled film and spreads out the GO sheets uniformly on the substrate, which results in the formation of a more compact and ordered gas barrier layer with significantly improved hydrogen barrier properties. Higher applied voltage results in a more noticeable field effect. Under 25 V, the hydrogen transmission rate of the PEI/GO self-assembled 10-layer film reached 81 cm³/m² 24 h 0.1 MPa, which was 65% lower than that of standard composite films prepared without using an electric field.     

On-demand channel reservation scheme for common traffic in wireless mesh networks

Wireless mesh networks (WMNs) have recently gained momentum as a new broadband internet access technology to provide internet traffic. These networks have unique characteristics that make them different from ad hoc networks. These differences are as follows. First, WMNs are composed of static mesh routers that are equipped with multiple radio interfaces and turn each interface into a non-overlapping channel. These additional interfaces can create multiple concurrent links between adjacent nodes. Second, most of the traffic in WMNs is directed towards the gateway. Third, both local traffic and internet traffic are relayed by the mesh router to indeed destination. The Multi-Radio Ad hoc On-Demand Distance Vector (AODV-MR) developed to support multi-radio and does not take into account above-mentioned WMNs characteristics. In this paper, we propose an on-demand channel reservation scheme to reserve some of mesh router radio interfaces to support the gateway traffic while the remaining interfaces can be used to support the local traffic. Our scheme establishes high throughput paths for the traffic destined at the gateway, reduces the intra-flow and inter-flow interferences as well as to support full duplex node transmission.The scheme allows the gateway to assign a list of channels for each received gateway routing discovery message. Simulation results show that our proposed scheme significantly improves the performance of multi-radio multi-channel wireless mesh networks.