碳酸盐岩储层酸蚀蚓孔形态地质建模

针对碳酸盐岩储层基质酸化形成的酸蚀蚓孔特点,基于基质酸化机理和分形理论,借助编制的VB软件,对碳酸盐岩水平井的酸蚀蚓孔形态进行数值模拟,分析天然裂缝和其对应参数以及盐酸质量浓度对水平井酸蚀蚓孔增长形态的影响。结果表明:存在天然裂缝时,蚓孔大多在裂缝尖端处生长,不存在天然裂缝时在井筒附近生长密集;随着盐酸质量浓度增加,蚓孔沿裂缝在尖端处生长的趋势明显;天然裂缝条数和长度的增加使得酸蚀蚓孔形态对井筒周围蚓孔形态有一定的抑制作用。     

稠油出砂冷采颗粒离散元数学模型

疏松砂岩油藏渗流出砂问题的实质是砂岩地层微粒的剥蚀与运移,鉴于传统物理模拟方法的复杂性以及现有数值模拟方法在描述非连续介质方面的不足,建立了考虑流固耦合的颗粒离散元稠油出砂冷采数学模型,优选了Mohr-Coulomb屈服准则作为颗粒从母岩剥离的破坏准则,从微观角度定量描述出砂机理。数学模型模拟产砂速率、产油速率及井底压力结果与一维物理模型实验实测值均吻合较好,验证了模型的正确性和可靠性,在此基础上,定量描述了稠油出砂冷采的临界条件及蚓洞扩展规律。把所建立数学模型拓展到现场,计算结果表明,颗粒离散元数学模型能够正确描述稠油出砂冷采出砂规律,为研究稠油出砂冷采提供了一种新手段。图8参17     

Fault-Tolerant Routing Algorithm in Meshes with Solid Faults

A fault-tolerant routing method that can tolerate solid faults using only two virtual channels is presented. The proposed routing algorithm, called FT-Ecube, not only uses a fewer number of virtual channels but also tolerates f-chains in the meshes. Furthermore, the proposed scheme misroutes messages both clockwise and counter clockwise directions to reduce channel contention on f-rings. It is shown that the proposed algorithm is deadlock-free and livelock-free in meshes when it has nonoverlapping multiple f-regions. Further, we conducted flit-level simulations to evaluate the performance of the proposed routing algorithm. As our simulation results show, FT-Ecube tolerates multiple faulty blocks using only two virtual channels per physical channel, and has good performance in terms of average latency. This work is supported by the NSF grant MIP-9705738     

基于邻居路由的Ad Hoc网络虫洞检测

针对Ad Hoc网络中虫洞检测方法带来的高时延和能耗问题,提出一种低时延和能耗的轻量级虫洞检测方法。即在节点查询路由后,利用路由节点的邻居数目,找出可能受虫洞影响节点的集合,同时依据路由节点的某个邻居节点的路由信息,进一步确定路由节点是否受虫洞影响。仿真结果表明,该方法可有效减少虫洞检测中的路由查询次数,并且与DeWorm和E2SIW方法相比,可有效减少时间延迟和能量消耗。     

直连网络中交换机制综述

由于具有并行处理以及良好的扩展性等特性,在构建大型并行计算系统中直连网络是一种较受欢迎的连接方式.目前直连网络已经广泛地应用于多处理器系统、多计算机系统,集群系统以及太比特路由器中.交换机制的选择直接影响了直连网络系统的性能.文中总结了直连网络交换机制的特点,对主要的几种交换机制进行了分析比较,并展望了其发展趋向.     

滑溜水在裂缝性碳酸盐岩体积酸压中的研究与应用

滑溜水是页岩气、致密油非常规油气藏体积改造中应用最广泛的压裂液体系,旨在利用低黏滑溜水强的穿透性能激活天然裂缝提高裂缝复杂程度。基于深层裂缝性碳酸盐岩储层基质物性差、非均质性强,裂缝是主要储集空间和渗流通道的储层特征,提高改造体积是实现高产稳产的核心,需采用低黏流体大排量注入来提高天然裂缝激活几率,提出滑溜水、冻胶和转向酸复合的体积酸压技术。评价了新型聚合物类滑溜水性能,利用室内实验（大物模、酸液滤失）和数值模拟相结合的方法研究了滑溜水在体积酸压中的作用机理,研究表明:新型聚合物类滑溜水具有较好的减阻性能,能够降低施工管柱摩阻,实现大排量施工,助力改造效果提升;滑溜水大排量注入形成复杂裂缝,低黏酸液注入形成酸蚀蚓孔提高裂缝连通性,滑溜水与低黏酸交替注入,实现微细裂缝"水力+酸蚀"缝网构建。上述研究成果现场应用显著,AT3x井压后获日产油35 m3、日产气50.3×104 m3高产油气流,为国内超高温深层复杂储层高效改造提供新的技术指导。      

An Efficient Tree-Based Multicasting Algorithm on Wormhole-Routed Star Graph Interconnection Networks Embedded with Hamiltonian Path

Multicasting is an important issue for numerous applications in parallel and distributed computing. In multicasting, the same message is delivered from a source node to an arbitrary number of destination nodes. The star graph interconnection network has been recognized as an attractive alternative to the popular hypercube network. In this paper, we propose an efficient and deadlock-free tree-based multi-cast routing scheme for wormhole-routed star graph networks with hamiltonian path. In our proposed routing scheme, the router is with the input-buffer-based asynchronous replication mechanism that requires extra hardware cost. Meanwhile, the router simultaneously sends incoming flits on more than one outgoing channel. We perform simulation experiments with the network latency and the network traffic. Experimental results show that the proposed scheme reduces multicast latency more efficiently than other schemes.     

Wormhole Broadcast in Hypercubes

We consider the problem of broadcasting a message in the n-cube, Q_n, equipped with wormhole switching. The communication model assumed is one-port, and the broadcasting scheme is path-based whereby, during broadcasting along a path by a node, all the nodes on that path will receive the message. The wormhole path length is m where –m's concurrently (cube-based broadcast). The second method is based on the concept of Gray codes (GCs), and at every given step, it forms the Hamiltonian path of appropriate size as the broadcast path (GC-based broadcast). It is shown that the steps required in GC-based broadcast is fewer than or equal to those needed by cube-based broadcast. Furthermore, comparison of time complexity of GC-based broadcast to the lower bound reveals that this algorithm is near-optimal, and in fact optimal in many cases. This work improves on the best algorithm developed for path-based broadcast in one-port hypercube both in complexity and in simplicity.     

Heuristic Contention-Free Broadcast in Heterogeneous Networks of Workstations with Multiple Send and Receive Speeds

This paper presents three efficient contention-free algorithms for broadcasting on heterogeneous networks of workstations (HNOW). In an HNOW, many different speed types of workstations can have distinct send and receive overhead. Previous research has shown that finding an optimal routing scheme in an HNOW is not easy [2,12], because properly arranging all workstations in the scheduling tree is difficult. Therefore, this investigation focuses mainly on enhancing the performance of an HNOW by properly arranging fastest nodes into the internal nodes of upper levels in the scheduling tree. Fastest node first is fundamental in designing an efficient algorithm. This paper presents three schemes called EBS, VBBS, and VBBSWF. All of these three schemes can be executed in O(n log(n)) time, where n is the number of workstations. They are all contention-free when broadcasting in an HNOW. Based on the simulation result, the proposed schemes outperform the broadcast with minimal steps [13] and the scheduling tree [22] generated by dynamic programing in an HNOW.     

一种基于测距的抗虫洞攻击安全定位机制

通过分析在无线传感器网络中,虫洞攻击对节点的基于测距定位过程的影响,提出了一种基于测距的安全定位机制,即通过节点间信息交互特性引入节点标记方案用于抵抗虫洞攻击;同时结合基于TDoA距离一致性进行定位使定位更加精确;最后实现安全定位。仿真实验结果表明,在攻击存在的环境中,该机制能够以较高的概率检测出虫洞攻击,并且定位成功的概率很高。