Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

The capability of embedded piezoelectric wafer active sensors(PWAS)to perform in-situ nondestructive evaluation(NDE)for structural health monitoring(SHM)of reinforced concrete(RC)structures strengthened with fiber reinforced polymer(FRP)composite overlays is explored.First,the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer.It was found that the presence of a disbond crack drastically changes the electromecfianical(E/M)impedance spectrum lneasurcd at the PWAS terlninals.The spectral changes depend on the distance between the PWAS and the crack tip.Second,large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer(CFRP)composite overlay.The beam was subject to an accelerated fatigue load regime in a three-point bending configuration up to a total of 807,415 cycles.During these fatigue tests,the CFRP overlay experienced disbonding beginning at about 500,000 cycles.The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection.Good correlation between the PWAS readings and the position and extent of disbond damage was observed.These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite overlays.

Gossip-Based Topology Management Protocol for Self-Organizing Overlays

Gossip-based protocols have attracted more and more attention because of their simplicity and reliability.They can be applied to large-scale overlays for solving problems such as topology management,information dissemination,and aggregation.However,previous works sample nodes by their indegrees,without considering the differences in capability among nodes,and result in losing global load balancing.This paper proposes a load balancing gossip protocol for self-organizing overlays-LBTMP(Load-Balancing Topology Management Protocol),which takes into account the differences in capability among nodes and real loads.The novel protocol takes remainder service ability as the determinant for node selection metric,making light loading nodes from local neighbor view as returned samples preferentially.In the meantime,LBTMP selects light loading nodes preferentially for topology information exchange,which can diffuse light loading nodes over the whole overlay more quickly.Simulations show that returned sample node selection is biased to light loading nodes in a global view,and the overlay tends to load balancing.

Structural Design of Pavement Overlays Based on Functional Parameters

This paper reports a practical pavement overlay design method based on PCI (Pavement Condition Index). Current pavement investigation method (JTJ 073 96) is compared to the ASTM D 5340, which is the standard test method for airport pavement condition evaluation initially developed for US Air Force. The deficiency in the calculation of PCI based on field data in JTJ 073 is discussed. The proposed design method is compared to AASHTO overlay design method with good agreement. The paper concludes with an example illustrating how the existing pavement structural capacity is related to pavement distress survey results. The presented design method can be used in the design for overlay rehabilitation of pavements of highways, urban streets and airports.

Laboratory evaluation of high-friction thin overlays for pavement preservation

Traditional asphalt concrete(AC)and stone matrix asphalt(SMA),which are used as thin asphalt overlays,are common maintenance strategies to enhancing ride quality,skid resistance,and durability.Recently,several studies have used a novel asphalt mixture known as a high-friction thin overlay(HFTO)to improve surface characteristics.However,it remains uncertain whether the laboratory properties of HFTO differ significantly from those of conventional mixtures.This study aims to evaluate the laboratory properties of HFTO mixtures and compare them with those of AC and SMA.Those mixtures with nominal maximum size of 9.5 mm were produced in the laboratory,and performance tests were conducted,including wheel tracking test,low temperature flexural creep test,moisture susceptibility test,Cantabro Abrasion Test,Marshall Test,sand patch test,British pendulum test,and indoor tire-rollingdown test.The results showed that the HFTO exhibited a lower tire/pavement noise than the AC and SMA.Additionally,HFTO had superior high-temperature stability,larger macro texture,and higher skid resistance in comparison to those of AC,but lower than those of SMA.Consequently,HFTO mixtures may be considered a suitable replacement for traditional AC mixtures in regions where skid resistance and noise reduction are concerns.

面向未来低碳道路养护的超薄罩面功能性研究综述

Highway maintenance mileage reached 5.25 million kilometers in China by 2021.Ultra-thin overlay is one of the most commonly used maintenance technologies,which can significantly enhance the economic and environmental benefits of pavements.To promote the low-carbon development of ultrathin overlays,this paper mainly studied the mechanism and influencing factors of several ultra-thin overlay functions.Firstly,the skid resistance,noise reduction,rutting resistance,and crack resistance of ultrathin overlays were evaluated.The results indicated that the high-quality aggregates improved the skid and rutting resistance of ultra-thin overlay by 5%-20%.The optimized gradations and modified binders reduced noise of ultra-thin overlay by 0.4-6.0 dB.The high viscosity modified binders improved the rutting resistance of ultra-thin overlay by about 10%-130%.Basalt fiber improved the cracking resistance of ultra-thin overlay by more than 20%.Due to the thinner thickness and better road performance,the performance-based engineering cost of ultra-thin overlay was reduced by about 30%-40%compared with conventional overlays.Secondly,several environmentally friendly functions of ultra-thin overlay were investigated,including snow melting and deicing,exhaust gas purification and pavement cooling.The lower thickness of ultra-thin overlay was conducive to the diffusion of chloride-based materials to the pavement surface.Therefore,the snow melting effect of self-ice-melting was better.In addition,the ultra-thin overlay mixture containing photocatalytic materials could decompose 20%-50%of the exhaust gas.The colored ultra-thin overlay was able to reduce the temperature of the pavement by up to 8.1℃.The temperature difference between the upper and lower surfaces of the ultra-thin overlay containing thermal resistance materials could reach up to 12.8℃.In addition,numerous typical global engineering applications of functional ultra-thin overlay were summarized.This review can help better understand the functionality of ultra-thin overlays and promote the realization of future multi-functional and low-carbon road maintenance.

适配融媒体云平台的SDN技术应用探讨

国家广播电视总局在关于《广播电视融媒体云平台的建设技术实施指南》中提出,为了降低复杂度,宜使用软件定义网络(SDN),通过集中的控制器集群实现VXLAN的控制平面,使得网络部署维护更简单,运行更稳定。本文重点对SDN技术特点和应用进行剖析,并提出设计实施参考建议。

Damage Mechanism of Ultra-thin Asphalt Overlay(UTAO) based on Discrete Element Method

Aiming to analyze the damage mechanism of UTAO from the perspective of meso-mechanical mechanism using discrete element method(DEM),we conducted study of diseases problems of UTAO in several provinces in China,and found that aggregate spalling was one of the main disease types of UTAO.A discrete element model of UTAO pavement structure was constructed to explore the meso-mechanical mechanism of UTAO damage under the influence of layer thickness,gradation,and bonding modulus.The experimental results show that,as the thickness of UTAO decreasing,the maximum value and the mean value of the contact force between all aggregate particles gradually increase,which leads to aggregates more prone to spalling.Compared with OGFC-5 UTAO,AC-5 UTAO presents smaller maximum and average values of all contact forces,and the loading pressure in AC-5 UTAO is fully diffused in the lateral direction.In addition,the increment of pavement modulus strengthens the overall force of aggregate particles inside UTAO,resulting in aggregate particles peeling off more easily.The increase of bonding modulus changes the position where the maximum value of the tangential force appears,whereas has no effect on the normal force.

Modelling of debris-flow susceptibility and propagation: a case study from Northwest Himalaya

The geological and geographical position of the Northwest Himalayas makes it a vulnerable area for mass movements particularly landslides and debris flows. Mass movements have had a substantial impact on the study area which is extending along Karakorum Highway(KKH) from Besham to Chilas. Intense seismicity, deep gorges, steep terrain and extreme climatic events trigger multiple mountain hazards along the KKH, among which debris flow is recognized as the most destructive geohazard. This study aims to prepare a field-based debris flow inventory map at a regional scale along a 200 km stretch from Besham to Chilas. A total of 117 debris flows were identified in the field, and subsequently, a point-based debris-flow inventory and catchment delineation were performed through Arc GIS analysis. Regional scale debris flow susceptibility and propagation maps were prepared using Weighted Overlay Method(WOM) and Flow-R technique sequentially. Predisposing factors include slope, slope aspect, elevation, Topographic Roughness Index(TRI), Topographic Wetness Index(TWI), stream buffer, distance to faults, lithology rainfall, curvature, and collapsed material layer. The dataset was randomly divided into training data(75%) and validation data(25%). Results were validated through the Receiver Operator Characteristics(ROC) curve. Results show that Area Under the Curve(AUC) using WOM model is 79.2%. Flow-R propagation of debris flow shows that the 13.15%, 22.94%, and 63.91% areas are very high, high, and low susceptible to debris flow respectively. The propagation predicated by Flow-R validates the naturally occurring debris flow propagation as observed in the field surveys. The output of this research will provide valuable input to the decision makers for the site selection, designing of the prevention system, and for the protection of current infrastructure.

Enhancing transjugular intrahepatic portosystemic shunt procedure efficiency with digital subtraction angiography image overlay technology in esophagogastric variceal bleeding

BACKGROUND Transjugular intrahepatic portosystemic shunt(TIPS)is a pivotal intervention for managing esophagogastric variceal bleeding in patients with chronic hepatic schistosomiasis.AIM To evaluate the efficacy of digital subtraction angiography image overlay tech-nology(DIT)in guiding the TIPS procedure.METHODS We conducted a retrospective analysis of patients who underwent TIPS at our hospital,comparing outcomes between an ultrasound-guided group and a DIT-guided group.Our analysis focused on the duration of the portosystemic shunt puncture,the number of punctures needed,the total surgical time,and various clinical indicators related to the surgery.RESULTS The study included 52 patients with esophagogastric varices due to chronic hepatic schistosomiasis.Results demonstrated that the DIT-guided group expe-rienced significantly shorter puncture times(P<0.001)and surgical durations(P=0.022)compared to the ultrasound-guided group.Additionally,postoperative assessments showed significant reductions in aspartate aminotransferase,B-type natriuretic peptide,and portal vein pressure in both groups.Notably,the DIT-guided group also showed significant reductions in total bilirubin(P=0.001)and alanine aminotransferase(P=0.023).CONCLUSION The use of DIT for guiding TIPS procedures highlights its potential to enhance procedural efficiency and reduce surgical times in the treatment of esophagogastric variceal bleeding in patients with chronic hepatic schistoso-miasis.

基于云原生网络多态协同的技术研究

云原生网络是容器云的核心,部署在公有云、私有数据中心或混合云。不同基础设施环境导致底层网络存在差异,会对安全管控造成挑战。不同的云原生网络方案具有不同的容器适配成本,如NAT、负载均衡、低延时通信。CNI开源项目分为Overlay和Underlay两种流派:Overlay通过隧道技术构建独立容器网络,利用NAT实现通信转换,适用大多数场景,但对传统主机直用适配成本高;Underlay直接使用主机网络,限制较多但性能好、对传统主机应用的适配成本低。因此,设计一种基于开源CNI项目的多种Underlay CNI协同解决容器集群通信问题。实践表明优化设计可降低30%网络运维工作量。解决Underlay场景下IP分配、多网卡路由、宿主机连通性等问题,加强各Underlay CNI项目。协同多种CNI确保了集群网络连通性,利用物理网卡可降低通信延时约30%。

基于云网POP的差异化云网络建设方案探讨

国家新型基础设施建设给各运营商带来了新的发展契机,纷纷布局以云网融合为特征的数据中心建设。本文重点分析运营商如何打造云网一体化网络服务提供点(Point of Presence,POP),满足不同客户差异化的入云或云间组网需求,实现云网能力端到端快速贯通,云资源池快速规模化部署,缩短云资源池或数据中心接入网络的建设和开通周期。

SRv6技术在SD-WAN专线上的应用研究及现网验证

传统软件定义广域网络(software-defined wide area network,SD-WAN)通过虚拟扩展局域网(virtual extensible local area network,VXLAN)/通用路由封装(generic routing encapsulation,GRE)/互联网安全协议(internet protocol security,IPSec)等隧道技术建立Overlay虚拟网络连接,网络质量受限于Underlay网络。为解决传统SD-WAN技术无法感知网络底层业务特性的问题,对SRv6协议进行研究,提出基于SRv6技术的新一代SD-WAN技术,并基于现网搭建测试环境进行验证,以期为相关人员提供参考。

网络5.0业务网架构研究

随着物联网、工业互联网等新兴业务的迅猛涌现,网络的确定性、安全性和资源调度等方面面临着重大挑战。然而,现有网络是“尽力而为”的模式,只管控网络资源,不管控业务或应用连接。网络5.0针对以上问题,提出了“创新协议、确定性网络、内生安全可信、自组织网络、算力网络”等解决方案,为未来全业务承载提供承载底座。网络5.0在架构层面,需解决现有业务承载的OTT方式,即业务的应用层与网络层的控制与匹配不足的问题。首先,分析了网络5.0业务网的4个关键创新动机;其次,创新性地提出了新的业务网架构,通过在现有网络承载层上叠加业务核心层,使网络具备动态的业务感知、业务连接、资源匹配和连接管控能力,内生解决了网络业务/应用Underlay+Overlay协同的确定性承载,又开创了基于用户体验和应用感知的新型业务和精细化网络运营模式;最后,列出了超算快线和不间断直播两个典型业务场景,为未来的网络研究方向提供了强有力的线索。

云平台框架下网络节点数据安全传输技术

在传统的数据传输过程中,由于缺乏对节点之间关联关系的分析,导致数据的丢包率较高。针对此问题,提出了云平台框架下网络节点数据安全传输技术。利用Overlay结构在连接组网各个接口中的作用,构建以其为基础并包含多个节点数据的网络拓扑抽象模型。在数据传输阶段分析传输数据的资源需求,然后利用网络的允许时延,调整网络拓扑模型中相邻阶段的运行频率,使得数据接口以相同的频率执行数据传输,保障数据的安全性。测试结果显示,云平台框架下网络节点数据传输技术的丢包率始终稳定在10.0%以内。

基于可视化学科多样性测度指数和主题模型的领域学科交叉知识图谱构建--以纳米科技领域为例

[目的/意义]基于文献计量学和文本挖掘方法探索与某领域相关的学科交叉知识图谱的新思路。[方法/过程]提出可视化学科多样性测度指数和主题模型的领域学科交叉知识图谱研究框架,基于Science Overlay Map和嵌入领域本体的LDAvis进行领域学科交叉知识图谱的构建,并以纳米科技领域为例,验证学科交叉知识图谱研究框架的有效性和适用性。[结果/结论]基于Science Overlay Map的领域学科交叉科学地图,从全学科的角度展示纳米科技领域与其他学科的交叉情况,基于LDAvis结合领域本体的学科交叉主题交互图则聚焦具体的学科交叉主题和主题之间的相互关系,二者的结合可以从宏观和微观上更清晰地把握纳米科技领域与其他学科的交叉情况。本研究可以弥补学科交叉主题识别结果不容易被解释的局限性,为领域学科交叉知识图谱研究提供了一种解决方案的新视角。

基于响应面法的不同配比沥青混凝土性能平衡优化设计

采用4种不同标号沥青及3种油石比制备12组沥青混合料,通过车辙试验、Overlay Tester(OT)试验以及动态模量试验评价其高温性能、低温性能和力学性能。采用响应面法对不同沥青混合料的高温性能、低温抗裂性能、疲劳性能和力学性能进行平衡性分析。结果表明,采用高油石比和低标号沥青可显著提高混合料的高温性能及力学性能且具有一定的抗裂性能,根据性能叠加图推荐了满足高模量沥青混凝土高温性能、抗裂性能与力学性能标准的沥青标号与油石比范围,其结果对于合理进行不同标号沥青混凝土配合比设计具有较大的参考价值。

基于SD-WAN的企业专线应用与实践

为满足各业务节点灵活的网络访问需求,对网络建设和运维提出了更高的要求,中国广电山东网络有限公司青岛市分公司探索了基于SD-WAN技术的新型企业专线建设,并根据实际应用场景进行了组网实践,为更多中小型企业广域网络系统的组网提供了借鉴和参考。

基于SDN的医疗数据中心网络架构研究

随着网络规模不断增大,医疗数据中心烦琐和低效等问题日益凸显,SDN(Software Defined Network)的网络架构正好能解决这些问题。其通过核心技术OpenFlow分离控制层和数据层,实现对网络流量的灵活控制,使数据中心网络更加高效、便捷和智能。由于SDN的开放性,使得网络架构无须依赖底层网络设备,屏蔽了设备差异,用户也可以自定义网络规则,让网络更加灵活和智能。相比传统网络架构,SDN为网络管理提供了更多的便捷性和可操作性。

Remote sensing monitoring of the recent rapid increase in cultivation activities and its effects on desertification in the Mu Us Desert, China

The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increase in reclamation on desertification land and its impact on desertification have raised concerns. In this study, we first extracted data on cultivated land and desertification land in 1975,1990, 2000, 2005, 2010, 2015, and 2020 through the human-computer interaction visual interpretation method. By overlaying the cultivated land dynamics and desertification land, we subsequently explored the effect of cultivation activities on desertification in the Mu Us Desert during the six periods from 1975 to 2020(1975–1990, 1990–2000, 2000–2005, 2005–2010, 2010–2015, and 2015–2020). The results showed that cultivated land in the Mu Us Desert showed a fluctuating and increasing trend from 3769.26 km~2 in 1975 to 4865.73 km~2 in 2020, with 2010 as the turning point for the recent rapid increase. The main contributors included the large and regular patches distributed in Yuyang District and Shenmu of Shaanxi Province, and relatively smaller patches concentrated in Inner Mongolia Autonomous Region. The increased cultivated land from the reclamation on desertification land was dominated by moderate and severe desertification lands, and the decreased cultivated land that was transferred into desertification land as abandoned cultivated land was dominated by slight and moderate desertification lands. The effect of cultivation activities on desertification reversal(average area proportion of 10.61% for reversed desertification land) was greater than that of the development of desertification(average area proportion of 5.82% for developed desertification land). Nevertheless, compared to reversed desertification land,both the significant increase of developed desertification land during the periods of 2000–2005 and 2005–2010 and the insignificant decrease during the periods of 2005–2010, 2010–2015, and 2015–2020 implied a potential remobilization risk. Therefore, this study provides a significant theoretical reference for the formulation of ecological restoration projects and regional macroeconomic development policies by considering the influence of cultivation activities, to ensure the overall environmental stability and sustainability in desertification land where reclamation and abandonment activities have taken place.

Generation of Low-Delay and High-Stability Multicast Tree

Delay and stability are two key factors that affect the performance of multicast data transmission in a network.However,current algorithms of tree generation hardly meet the requirements of low delay and high sta-bility simultaneously.Given a general network,the generation algorithm of a multicast tree with minimum delay and maximum stability is an NP-hard problem,without a precise and efficient algorithm.To address these challenges,this paper studies the generation of low-delay and high-stability multicast trees under the model of spanning tree based on stability probability,degree-constrained,edge-weighted for multicast(T-SDE).A class of algorithms was proposed which creates the multicast tree greedy on the ratio of fan-out to delay(RFD)and probability of stability of terminal to obtain a high performance in multicast.The proposed algorithms greedily select terminals with a large RFD and a high probability of stability as forwarding nodes in the generation of the multicast tree,where the larger RFD and higher stability of upstream nodes are beneficial to achieve a low transmission delay and high stability in multicast.The proposed RFD can be compatible with the original model,which can take advantage of network connectivity during the generation of a multicast tree.This paper carries out simulation experiments on Matlab R2016b to measure the performance of the proposed algorithm.Experimental results show that the proposed algorithm can provide a smaller height,higher stability,and a lower transmission delay of the resulting multicast tree than other solutions.The spanning tree of the proposed algorithms can support low transmission delay and high stability in multicast transmission.