Dynamic wavelength and bandwidth allocation using adaptive linear prediction in WDM/TDM ethernet passive optical networks

Hybrid wavelength-division-multiplexing (WDM)/time-division-multiplexing (TDM) ethernet passive optical networks (EPONs) can achieve low per-subscriber cost and scalability to increase the number of subscribers. This paper discusses dynamic wavelength and bandwidth allocation (DWBA) algorithm in hybrid WDM/TDM EPONs. Based on the correlation structure of the variable bit rate (VBR) video traffic, we propose a quality-of-service (QoS) supported DWBA using adaptive linear traffic prediction. Wavelength and timeslot are allocated dynamically by optical line terminal (OLT) to all optical network units (ONUs) based on the bandwidth requests and the guaranteed service level agreements (SLA) of all ONUs. Mean square error of the predicted average arriv-ing rate of compound video traffic during waiting period is minimized through Wiener-Hopf equation. Simulation results show that the DWBA-adaptive-linear-prediction (DWBA-ALP) algorithm can significantly improve the QoS performances in terms of low delay and high bandwidth utilization.     

板底脱空注浆技术在水泥砼路面养护中的应用

板底脱空压浆处理是经济可行、简便实用且社会效益也很显著的一种水泥砼路面的预防性养护措施．但由于目前对板块脱空、基层均一性,底基层密实度等还缺乏有效、快速的检测手段。使压浆施工存在一些难点．有待进一步的研究与实践。     

Research and Application of Drag Reduction by Grouting the Pipe Jacking in Complex Conditions北大核心CSCD

This paper presents the technology measures, equipment selection and required grout properties and re-lated techniques for the grouting base-station arrangement of the drag reduction system of the Fuchun River pipe jacking project, which is characterized by a combined stratum, a longitudinal curve with a large falling head, a large gradient and high water pressure. Drag reduction by grouting can effectively reduce the friction coefficient in pipe jacking construction, decrease the time and frequency of the relay station, improve construction efficiency, and re-duce the grout loss along the stratum fissure while guaranteeing grouting pressure of the terminal, is favorable for sta-ble annular bentonite grouting between the stratum fissure and the segment. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

真空辅助压浆工艺在预应力混凝土结构中的应用

预应力混凝土结构中的孔道压浆效果，直接关系到预应力筋的防腐问题。真空辅助压浆工艺可以使孔道中的浆液填充密实，较好地解决应力筋的防腐问题。结合长珲工程实践，对真空辅助压浆工艺的压实原理工艺过程及质量控制做了详细的阐述。     

针对沉井下沉困难的分析及对策

石井河中游截污工程L4顶管工作井属小型沉井,依靠沉井自重采用不排水法下沉,施工过程中由于各种原因造成了下沉困难。文中对其产生的原因进行了分析,并提出了处理方法和预防措施。     

后张法预应力管道压浆质量问题的原因及对策

通过对后张法预应力管道压浆质量原因的细致分析,提出了保证其质量的技术措施和管理措施。     

水平旋喷桩预支护在软弱黄土隧道中的试验研究

为提高软弱黄土隧道地基承载力,针对研究项目洞口段围岩的特点,提出水平旋喷桩预支护方案.经计算分析,参考水平旋喷桩在其它工程项目中的应用情况.初步确定水平旋喷桩加固体的直径、长度、纵向间距等.结合围岩地质条件,采用不同的灰水比、注浆压力、钻机提升速度等施工控制参数开展大规模现场成桩试验.对所有成型桩体直径、长度、3 d及28 d强度进行检验.由检验结果调整预设计参数,得出了水平旋喷桩设计控制指标、施工工艺参数.工程应用表明,采用水平旋喷桩超前支护技术具有较强的适应性和可操作性,提高了软弱黄土地区公路隧道围岩稳定性和地基承载力,可为软弱黄土地区公路隧道的设计与施工提供借鉴.     

渗透注浆扩散理论探讨

本文在现有渗透性注浆理论基础上,考虑毛细力情况下,运用渗流力学对平面径向流、球形向心流两种渗透性注浆模型进行了推导,得到了球形和柱形渗透性注浆扩散公式.并以球形扩散公式为例,结合工程实例和现有常用的Maag球形扩散公式比较,从结果可初步推断:由Maag公式计算注浆所需时间偏小,本文所推导公式相对Maag公式更接近工程实际.最后对注浆参数对扩散半径的影响进行探讨,得到扩散半径对注浆参数的变化均较敏感,采用Maag公式和本文公式得出的趋势基本一致.     

Grouted Pile and Its Bearing Capacity

The grouting method applied in bored pile is an improvement to the conventional bored pile. Load tests have proved that grouting under the bored pile tip is an effective method to enhance the bearing capacity of the pile and to reduce the pile settlement. In this paper, the grouting technology is described and pile-load test results are discussed. In order to put the grouting method into design practice, the authors analyze the working mechanism of soil compaction. And, based on the theory of cavities expansion in soil mass, approximate formulae are proposed for estimating the bearing capacity of the grouted pile. The theoretical prediction agrees well with the load test results.     

煤矿采空区公路路基沉陷病害的治理技术

结合公路路基的物探检测结果和公路沉陷病害现状,并考虑实际施工的可行性等因素,介绍了深层明挖法处治、浅层明挖后基底强夯法处治、注浆处治和暂不处治等处治措施,供同行参考.