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1.
该文首次提出了主数据对象和影子数据对象概念模型,并结合主动数据库中“事件-条件-动作”的数据触发机制,利用多个通讯代理之间协同技术,解决了多个节点群中大型异构数据库之间的数据一致性维护问题。  相似文献   

2.
完成历史报警数据的记录功能是组态软件非常重要的功能,通常需要软件本身的控件来完成报警数据和事件的存储到外部数据库中的过程。本文分析SQL SERVER、My SQL、Access以及MSDE四种中小型数据库的区别,且以MSDE2000为例,通过lnTouch软件中的Alarm DB Logger实用程序,将历史报警和事件数据存储到MSDE2000数据库中,结合Alarm DB Purge-Archive实用程序,完成历史报警与事件记录的手/自动清除与归档操作,归档后的数据可以通过Alarm DB Restore进行恢复。  相似文献   

3.
异构数据库同步系统的研究与实现   总被引:15,自引:0,他引:15  
张震 《计算机应用》2002,22(10):43-45
采用“事件-条件-动作”的数据驱动机制实现数据库变更事件的实时获取,通过多个通讯代理协同工作完成异构数据库间的数据一致性维护。  相似文献   

4.
在基于事件流的大规模数据密集型系统中,数据可分为事件流数据和事件配置数据两大类,配置数据表示事件流的规则.在shared-nothing结构下,配置数据一般采用全复制的方式分布到各个数据库节点,用于和事件流数据的联合查询.采用全复制的配置数据,修改操作必须在所有节点上进行,数据的一致性控制和多节点的事务处理成为此类数据管理的关键问题.对配置数据的特点及其管理策略进行分析,并成功的在DBroker系统中实现了配置数据一致性控制.  相似文献   

5.
在基于数据广播的移动信息服务中,由于更新数据和广播数据两个过程是并发执行的,所以移动客户将面临接收数据不一致性问题。为此,该文提出了一种基于规则的并发控制算法来解决以上问题。在允许同步更新的情况下采用事件-条件-操作规则来进行无冲突的数据广播。该算法对移动机和数据库服务器的影响很小,同时又为基于广播的移动计算提供了数据一致性服务。  相似文献   

6.
为了提高交通监控中心发布交通事件信息的效率并减轻操作人员工作负荷,提出了基于小波变换和模糊聚类分析的交通事件信息发布系统,给出了系统的结构框架,设计了系统运行结构和实施流程。该系统采用小波变换技术对历史交通图像数据进行深度挖掘,提取有用特征信息;运用模糊聚类分析建立图像特征分类数据库,建立与异常交通图像特征相匹配的事件信息指令预案库;通过对实时图像的特征提取和数据库匹配,快速判别交通事件并完成事件信息的发布;实时扩充新的事件的图像特征及事件信息指令至相应数据库中。  相似文献   

7.
数据库营销是运用收集到的数据来预测用户未来的购买行为。成功实现数据库营销系统的关键是首先要建立一个企业资料数据库,在数据库或数据仓库中寻找有价值的隐藏事件,再利用数据挖掘技术对数据库中的数据进行分析,将有意义的信息归纳成结构模式。这样既降低了成本,又提高营销效率和企业的利润。  相似文献   

8.
针对数据库开发中的实际情况,运用Delphi数据库访问部件的事件解决了在数据显示、处理中的一些技术问题。并以2个部件的3个重要事件为例作了分析。  相似文献   

9.
一种基于数据库容灾的服务保障体系   总被引:1,自引:0,他引:1  
该文提出了一种基于数据库容灾的服务保障体系,利用数据同步方法解决了前期数据的一致性问题,在不可预知的灾难事件发生后,能快速地将服务漂移至备用数据库服务器,并能利用备份恢复模块,在短时间内对已经损毁的数据库资源进行恢复,保证了服务的连续性和数据的准确性,提高了数据库的容灾能力。  相似文献   

10.
提出了一种基于支持向量数据描述(SVDD)算法的快速事件检测方法.该算法把有事件样本和无事件样本分别用全体样本优化的SVDD算法进行优化.但每次只对那些对超球体边界有影响的数据进行优化.该方法既保留了全体样本优化SVDD算法的优点,又达到加快训练速度的目的.采用1-880数据库中实际交通的历史数据进行实验,并与全体样本优化SVDD实验结果相比较.实验证明该分类方法能够获得较高检测率和较低的误报率,且需要较短的训练时间,表明了所给方法的有效性和可行性.  相似文献   

11.
One of the problems found in the 2.5 in. hard disk drives (HDDs) in operation is the vibration of the HDD case. Aiming to find crucial information to reduce the vibration transmitted to the outer shell of HDD, the parameters involving vibrational energy transmission through the main components of HDD are identified by the test-based statistical energy analysis (SEA). First, the vibration tests of HDD in the idle mode are performed in order to identify the contribution of the main components; the top cover, the platters, and the actuator arm to the overall vibration of HDD. The SEA parameters including the dissipation loss factors of the individual components and coupling loss factors of the pairs of the components are then experimentally determined in order to calculate the vibration transmission power among the components. The determined parameters, hence, provide some vibrational energy transmission characteristics to facilitate the design of the HDD components to generate less vibration. With some further studies using this concept, the vibration due to shock exerted to the shell of HDD that is transmitted to main components inside the HDD can also be reduced.  相似文献   

12.
Crashworthiness is an increasingly important design consideration for operational hard disk drive (HDD). The simulation model of HDD is first investigated by the finite element method. Maximum flying height, pitch angle and roll angle, maximum stress are put forward as indexes for HDD response to drop impact. Sometime, these indexes are crashworthiness evaluation parameters. The drop impact response of the finite element model under different surface drops and different angle drops are presented. Simulation results are proven to be fundamental method of crashworthiness analysis, evaluation and design for HDD.  相似文献   

13.
This research investigates the electromechanical variables of a spindle motor and an actuator of an operating hard disk drive (HDD) due to the positioning and the free-fall of a HDD. Magnetic fields of a brushless DC motor and a voice coil motor are determined by the time-stepping finite element equation of the Maxwell equation and the driving circuit equation. The pressure of the fluid dynamic bearings (FDBs) is determined by solving the finite element equation of the Reynolds equation to calculate the reaction force and the friction torque. Dynamic equations of the rotating disk-spindle, actuator, and stationary bodies of a HDD are derived from the Newton–Euler’s equation. The speed control of the rotating disk-spindle and the servo control of the actuator are included to describe the head positioning between the rotating disk and the head. The simulation is performed to investigate the electromechanical variables of the spindle motor and the actuator due to the positioning and the free-fall of a HDD. This research shows that the positioning and the free-fall of a HDD change the electromechanical variables of the spindle motor and the actuator of an operating HDD, and that monitoring their electromechanical variables may identify the positioning and the free-fall of a HDD without using extra sensors.  相似文献   

14.
This research investigates how the design variables of ball bearing affect the bearing stiffness and the natural frequencies of a hard disk drive (HDD) spindle system at elevated temperature. It shows that any design change that increases the contact angle of ball bearing reduces the variation in the bearing stiffness and the natural frequencies at elevated temperature. This research also proposes a robust HDD spindle motor in which a wave spring maintains a constant preload minimizing the effect of temperature variation. Experimental modal testing shows that the reduction of the natural frequencies at elevated temperature is much less in the proposed HDD spindle system than in the conventional spindle system. The proposed HDD spindle motor can improve the dynamic reliability of a HDD spindle system, which contributes to the high track density of a HDD.  相似文献   

15.
The traditional hard disk drive (HDD) is often a bottleneck in the overall performance of modern computer systems. With the development of solid state drives (SSD) based on flash memory, new possibilities are available to improve secondary storage performance. In this work, we propose a new hybrid SSD–HDD storage system and a selection of algorithms designed to assign pages across an HDD and an SSD to optimise I/O performance. The hybrid system combines the advantages of the SSD’s fast random seek speed with the sequential access speed and large storage capacity of the HDD to produce significantly improved performance in a variety of situations. We further improve performance by allowing concurrent access across the two types of storage devices. We show the drive assignment problem is NP-complete and accordingly propose effective heuristic solutions. Extensive experiments using both synthetic and real data sets show our system with a small SSD can outperform a striped dual HDD and remain competitive with a dual SSD.  相似文献   

16.
This paper investigates the dynamic behavior of a HDD spindle system with fluid dynamic bearings (FDBs) by solving the Reynolds equation and the equations of a motion of a HDD spindle system in five degrees of freedom. FEM is used to solve the Reynolds equation in order to calculate the pressure distribution in fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors of a HDD spindle system, such as the whirling and the tilting motion, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This paper also proposes two design methods to improve the dynamic characteristics of a HDD spindle system without increasing friction torque, i.e., optimization of the width of the lower and the upper journal bearings and the journal bearings with asymmetric grooves.  相似文献   

17.
In this paper, topology optimization in design of suspensions for high-density magnetic recording systems is studied. With the development of higher data density and the faster data streaming, a hard-disk drive (HDD) is required to move faster with greater positioning accuracy. At this situation, even small mechanical vibration induced by seeking motion may result in error in data reading. According to the operational characteristics of HDD suspension, the present work is focused on the topology design of HDD suspension for the dynamic shock response problem. As a result of this research, several new topological structures of HDD suspension are obtained, which are largely different from previous work, and dynamic response under shock force and stability of passive structure are also improved.  相似文献   

18.
 This paper presents a method to investigate the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. Finite element model is developed for the rotating and stationary parts of a HDD spindle system separately to determine their thermal deformations by using ANSYS, a finite element program. Then, the relative position of the rotating part with respect to the stationary part is determined by solving the equilibrium equation of the contact force between upper and lower ball bearings. The validity of the proposed method is verified by comparing the theoretical natural frequencies of a HDD spindle system with the experimental ones before and after temperature variation. The proposed method makes it possible to predict the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. It shows that the elevated temperature results in the increase of contact angle and the decrease of bearing deformation, contact force and bearing stiffness, which result in the decrease of the natural frequencies of a HDD spindle system. Received: 20 June 2002 / Accepted: 28 August 2002  相似文献   

19.
A hard disk drive (HDD) is very sensitive to shock. Increasing portability demands have led to increased HDD exposure to unexpected shocks. Therefore, the dynamic characteristics of an HDD were utilized to investigate the relative behavior of the disk and head stack assembly (HSA) during operational shock. A finite element model of HDD was constructed to simulate operational shock. This model included the spindle system, base, HSA, and disk. The relative behavior of the disk and HSA was analyzed using different bases with different stiffness. A drop test was performed to verify the simulation results. A modified base design was then proposed to protect against contact between the disk and HSA in HDD.  相似文献   

20.
Since its invention, the Hard Disk Drive (HDD) has been the most widely-used device for data storage. Recently, the volume of data is getting larger and the corresponding rotation speed of the HDD is increasing to allow for better data transfer. The decreasing size of the disk is increasing the density of data on the disk surface. As a result, the positioning accuracy of the Suspension Slider Unit (SSU), where the magnetic head is mounted, is the problem that has to be overcome for better performance of the HDD. Additionally, the increased rotating speed of the disk induces unsteady flow between each pair of disks. This unsteady flow becomes turbulent around the SSU and induces vibrations on the SSU which deteriorate the performance of the HDD. There have been many investigations to understand the fluid mechanics phenomena inside the HDD filled with air. Additionally, many modifications have been tried to minimize the flow-induced vibration on the SSU by placing a blockage upstream of the arm to generate a low velocity region. However, none of these investigations have explored the effect of using gases other than air. In this work, the flow physics in the HDD is investigated numerically with the drive filled with air or helium. Numerical analyses were performed using the commercial code (ANSYS/CFX) with an expanded 2 × model simulating Seagate cheetah 2.5-inch drive. Despite obvious un-addressed issues in sealing the HDD, the unsteady characteristics of the flow are dissipated sufficiently faster in helium than in air so as to warrant further studies addressing the more practical issues of working with helium. Of particular importance is the unsteady flow around the SSU. This leads to lower levels of flow-induced vibration in the case of helium flow. As such, HDD performance may be improved by using helium to improve the dynamics of the HDD at higher rotation speeds. For both air- and helium-filled drives, calculations have been performed with two different locations of the SSU and two different angular velocities, 1,000 and 3,000 rpm corresponding to 5,000 and 15,000 rpm in 3.5-inch commercial drive. Not only is it shown that the helium-filled drive suffers lower positioning errors, but also the underlying flow physics responsible for such improvement are explained.  相似文献   

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