Web caching has been considered as a powerful solution to deal with the growth of Web traffic. Several studies have shown that caching documents throughout the Internet can save network bandwidth and reduce document a...
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Web caching has been considered as a powerful solution to deal with the growth of Web traffic. Several studies have shown that caching documents throughout the Internet can save network bandwidth and reduce document access latency. However, this technique has introduced new problems such as maintaining the document coherency and selecting the next document to be removed. With the continuous increase in demand for documents, the Web cache servers are becoming the new bottleneck. A need for better resource management is becoming urgent in order to reduce the overhead sustained by Web cache servers. In this paper, a number of Web replacement policies are discussed and compared on the basis of trace-driven simulations. The impact of the Web cache server configuration is pointed out through a set of experiments that use the cache size as a tuning parameter.
A proper initialization requires starting the process in a state close to the expected steady state. In Web caching, the initialization problem is faced each time a new document enters the cache. Independently of the ...
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A proper initialization requires starting the process in a state close to the expected steady state. In Web caching, the initialization problem is faced each time a new document enters the cache. Independently of the method used to sort the documents into the cache, the newly referenced document is inserted in a so called "removal-list", from which documents are removed when storage space is needed. Often, undesirable documents are assigned a high priority, consequently these documents remain for quite a long time in the cache, leading to a decrease in cache server performances. We investigate one category of undesirable documents, which pass the filters commonly used to control the cache processing.
Cooperation among various types of management functions is necessary to allow management functions to interwork in providing and using information services for systems management. To understand these tasks from the po...
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Cooperation among various types of management functions is necessary to allow management functions to interwork in providing and using information services for systems management. To understand these tasks from the point of view of cooperative working, this article discusses the requirements and presents the concept of cooperative system management.
In mobile collaborative applications, collaborators may move across heterogeneous environments. This paper proposes object models for seamless transition of collaborators across heterogeneous environments. This is ach...
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In mobile collaborative applications, collaborators may move across heterogeneous environments. This paper proposes object models for seamless transition of collaborators across heterogeneous environments. This is achieved by framing the various limitations of the environment as constraints and abstracting them into a constraint meta-object. Collaborator objects are dynamically customized by attaching the appropriate constraint meta-object based on the environment in which the collaborators are working. Remote customization of objects is achieved by 'distributed glue model'.
Reactive computer control systems need to track the behaviour of their inherently parallel physical environment. Hence, most non-trivial industrial applications may depend on concurrent modelling techniques to handle ...
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Reactive computer control systems need to track the behaviour of their inherently parallel physical environment. Hence, most non-trivial industrial applications may depend on concurrent modelling techniques to handle system complexities including hard real-time constraints. Failure of such systems can lead to unacceptable consequences and can therefore be deemed as safety-related with respect to their application. parallel and distributedsystems can exhibit undesirable behaviours, e.g. deadlock, which could render a control system unsafe. The paper proposes that a set of undesirable parallel behaviours can be classified as unsafe for all applications and reviews a technique that can be employed to avoid or mitigate against them, The approach needed by software engineers of parallel and distributedsystems to facilitate this and meet the minimal safety standards is also given.
We present the design and implementation of MultiKron PCI, a hardware performance monitor that can be plugged into any computer with a free PCI bus slot. The monitor provides a series of high-resolution timers, and th...
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We present the design and implementation of MultiKron PCI, a hardware performance monitor that can be plugged into any computer with a free PCI bus slot. The monitor provides a series of high-resolution timers, and the ability to monitor the utilization of the PCI bus. We also demonstrate how the monitor can be integrated with online performance monitoring tools such as the Paradyn parallel performance measurement tools to improve the overhead of key timer operations by a factor of 25. In addition, we present a series of case studies using the MultiKron hardware performance monitor to measure and tune high-performance parallel completing applications. By using the monitor, we were able to find and correct a performance bug in a popular implementation of the MPI message passing library that caused some communication primitives to run at one half their potential speed.
By combining properties of fuzzy systems and neural networks, neurofuzzy modelling is ideally suited to many system identification and data modelling applications. Recently, data-driven model construction algorithms h...
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By combining properties of fuzzy systems and neural networks, neurofuzzy modelling is ideally suited to many system identification and data modelling applications. Recently, data-driven model construction algorithms have been developed to identify these models. These algorithms have proved essential for producing accurate parsimonious models. However, due to problems with sparse data and restricted model structures, models with high model variance are often produced. Thus resulting in models which generalise poorly. In this paper local Bayesian inference techniques are applied to neurofuzzy models, multiple prior probability density functions are placed on the weights and superfluous model variance is controlled. This gives a form of regularisation where Bayesian estimation produces simple re-estimation formulae which identify a suitable bias/variance balance from the data. This approach is considered a post-processing step to model construction, the merits of which are demonstrated by the application to a real world data set.
In this paper, novel methods for performing condition monitoring for power station turbine shafts are presented. The objective of this work is to investigate methods for producing accurate turbine vibration fault alar...
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In this paper, novel methods for performing condition monitoring for power station turbine shafts are presented. The objective of this work is to investigate methods for producing accurate turbine vibration fault alarms during turbine shaft rundowns. Wavelet packet analysis is employed to extract spectral features from healthy vibration signals and the probability density functions of these features are estimated. Both Gaussian models, using Bayesian inferencing, and mixture models are employed. Preliminary results show that the more computationally expensive mixture models produce more accurate density estimates and hence more reliable fault alarms.
SNMPv2 management tools for networks based on Novell NetWare and TCP/IP facilitate management of individual network workstations which allows a very detailed description of the network operation to be constructed. Usi...
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