基于PLC的变频节能系统在井筒冻结施工中应用的研究

针对冻结施工法装机容量大、电能消耗高以及施工过程的阶段性特点,在分析了冻结系统螺杆盐水机组不同工况下的机械特性和在各个冻结阶段电能消耗情况下,设计了一种基于PLC的变频节能系统。该系统以PLC为控制核心,通过压力传感器、液位计等对系统工况信息进行反馈,利用PID算法控制变频器的输出频率,从而达到了调节盐水泵流量、控制供冷量的目的。实验数据论证了该系统在井筒施工中应用的可行性与高效性。     

Numerical simulations of particle migration in a viscoelastic fluid subjected to shear flow

Particle migration is a relevant transport mechanism whenever suspensions flow in channels with gap size comparable to particle dimensions (e.g. microfluidic devices). Several theoretical as well as experimental studies have been performed on this topic, showing that the occurring of this phenomenon and the migration direction are related to particle size, flow rate, and the nature of the suspending liquid.In this work we perform a systematic analysis on the migration of a single particle in a sheared viscoelastic fluid through 2D finite element simulations in a Couette planar geometry. To focus on the effects of viscoelasticity alone, inertia is neglected. The suspending medium is modeled as a Giesekus fluid.An ALE particle mover is combined with a DEVSS/SUPG formulation with a log-representation of the conformation tensor giving stable and convergent results up to high flow rates. To optimize the computational effort and reduce the remeshing and projection steps, needed as soon as the mesh becomes too distorted, a ‘backprojection’ of the flow fields is performed, through which the particle in fact moves along the cross-streamline direction only, and the mesh distortion is hence drastically reduced.Our results, in agreement with recent experimental data, show a migration towards the closest walls, regardless of the fluid and geometrical parameters. The phenomenon is enhanced by the fluid elasticity, the shear thinning and strong confinements. The migration velocity trends show the existence of a master curve governing the particle dynamics in the whole channel. Three different regimes experienced by the particle are recognized, related to the particle-wall distance. The existence of a unique migration behavior and its qualitative aspects do not change by varying the fluid parameters or the particle size.     

一种基于动态迁移技术的寄存器保护方法

在强辐射环境中,寄存器会受到高能粒子冲击而发生位翻转导致寄存器内容发生变化,称这种现象为寄存器故障。对关键寄存器进行定义,提出一种寄存器保护模型,通过动态申请系统当前空闲的寄存器作为关键寄存器的备份,在运行过程中运用动态迁移技术对关键寄存器进行保护,使寄存器自身具有一定的容错能力。     

Exploiting the performance gains of modern disk drives by enhancing data locality

Due to the widening performance gap between RAM and disk drives, a large number of I/O optimization methods have been proposed and designed to alleviate the impact of this gap. One of the most effective approaches of improving disk access performance is enhancing data locality. This is because the method could increase the hit ratio of disk cache and reduce the seek time and rotational latency. Disk drives have experienced dramatic development since the first disk drive was announced in 1956. This paper investigates some important characteristics of modern disk drives. Based on the characteristics and the observation that data access on disk drives is highly skewed, the frequently accessed data blocks and the correlated data blocks are clustered into objects and moved to the outer zones of a modern disk drive. The idea attempts to enhance spatial locality, improve the efficiency of aggressive sequential prefetch, and take advantage of Zoned Bit Recording (ZBR). An experimental simulation is employed to investigate the performance gains generated by the enhanced data locality. The performance gains are analyzed by breaking down the disk access time into seek time, rotational latency, data transfer time, and hit ratio of the disk cache. Experimental results provide useful insights into the performance behaviours of a modern disk drive with enhanced data locality.     

面向Lustre文件系统的固态盘存储加速技术研究

磁盘的随机I/O延时制约了存储系统的性能提高,具备高性能随机I/O特性的固态盘(solid state disk,SSD)逐渐成为关注的热点.分析了磁盘、Flash型SSD以及DRAM型SSD三类设备不同的性能特点,讨论了SSD存储加速技术的研究现状,提出了一种面向Lustre文件系统的固态盘存储加速系统架构,介绍和分析了各模块的构成与原理,提出了对象迁移策略.     

多虚拟机实时迁移中自适应的迁移算法选择框架

IaaS云计算平台中主要通过实时迁移多台虚拟机来实现资源的动态调度、管理与优化。虽然Pre-copy和Post-copy是单虚拟机实时迁移的两种主流算法,且各有优缺点,但现有的多虚拟机实时迁移系统只是单一地使用其中一种迁移算法,无法根据各虚拟机的不同负载情况灵活选择最有效的迁移算法,降低了整体迁移效率。提出一种自适应的实时迁移算法选择框架,利用模糊聚类方法对待迁移的多虚拟机进行分类,按类别选择最适合的迁移算法。实验结果表明,所提出的迁移算法选择框架能够在多虚拟机实时迁移中发挥两个迁移算法的各自优势,有效提高整体的实时迁移性能。     

RT-Thread的SPI总线驱动结构分析 、移植及应用

介绍了串行外设接口SPI的通信原理,对RT Thread操作系统下的SPI总线驱动结构进行了详细的研究与分析.以STM32F407ZG对W25Q64的读写为例,介绍了硬件SPI总线驱动的移植步骤,并详细介绍了SPI应用程序设计及技术实施细节.最后通过实验,对SPI驱动移植及程序设计的可行性及有效性进行验证,实验结果表明,RT Thread操作系统下的SPI总线驱动结构设计合理,移植方便且应用程序设计简单,本文所介绍的移植与应用方法可行有效.     

基于代价感知的云任务处理策略

绿色云计算旨在保证服务质量的前提下,最大限度地降低云服务成本．针对这一问题,提出一种兼顾云数据中心高性能和低成本的策略,通过虚拟机动态迁移等技术进行云任务聚合,关闭空闲的节点以最小化能量消耗,同时考虑虚拟机迁移性能,以此保证任务的服务质量．实验结果表明,代价感知的策略可以减少打开节点的个数,兼顾迁移能耗和迁移延迟,在节能的前提下使服务质量得到保证．     

Cycles in economic systems with open labor markets

A dynamic macromodel of an economic system with a monopsonic labor market and variable labor resources is considered. The initiation conditions for classical business cycles are investigated for this model. Bifurcation analysis of the model is performed to estimate the effect of the minimum wage on the way such cycles form. The results of theoretical analysis are supplemented with numerical experiments. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 48–72, July–August 2008.     

Towards a green cluster through dynamic remapping of virtual machines

Since power is one of the major limiting factors for a data center or for large cluster growth, the objective of this study is to minimize the power consumption of the cluster without violating the performance constraints of the applications. We propose a runtime virtual machine (VM) mapping framework in a cluster or data center to save energy. The new framework can make reconfiguration decisions on time with the consideration of a low influence on the performance. In the GreenMap framework, one probabilistic, heuristic algorithm is designed for the optimization problem: mapping VMs onto a set of physical machines (PMs) under the constraint of multi-dimensional resource consumptions. Experimental measurements show that the new method can reduce the power consumption by up to 69.2% over base, with few performance penalties. The effectiveness and performance insights are also analytically verified.