16882491
A MAP/G/1 Queue with Negative Customers
In this paper, we consider a MAP/G/1 queue with MAP arrivals of negative customers, where there are two types of service times and two classes of removal rules: the RCA and RCH, as introduced in section 2. We provide an approach for analyzing the system. This approach is based on the classical supplementary variable method, combined with the matrix-analytic method and the censoring technique. By using this approach, we are able to relate the boundary conditions of the system of differential equations to a Markov chain of GI/G/1 type or a Markov renewal process of GI/G/1 type. This leads to a solution of the boundary equations, which is crucial for solving the system of differential equations. We also provide expressions for the distributions of stationary queue length and virtual sojourn time, and the Laplace transform of the busy period. Moreover, we provide an analysis for the asymptotics of the stationary queue length of the MAP/G/1 queues with and without negative customers.
36836516
Visualization of geostress tensor along oil well trajectory
A simple and efficient method is proposed to visualize a symmetric second order tensor along 3D curves. It is also applied to an oil well model in which, along the well trajectory, the spatial distribution of geostress is visualized to predict the stability of the oil well bore. To give visual representations several forms are used: (1) we visually compare the magnitude of stresses to determine the mud weight; (2) based on a set of ellipse cross-sections along the well trajectory and the ellipticity of the ellipse we predict the shear failure direction and the stability of the oil well bore; (3) from a hinged curved surface, we emphasize the direction of principal stresses; (4) to give useful information we apply other skills such as magnified details, animation and an interactive interface. Our method avoids two defects in the references, that is, the visual cluster caused by discrete point tensor glyphs, and the integration problem of the hyperstreamline.
14077243
Tail asymptotics for the queue length in an M/G/1 retrial queue
In this paper, we study the tail behavior of the stationary queue length of an M/G/1 retrial queue. We show that the subexponential tail of the stationary queue length of an M/G/1 retrial queue is determined by that of the corresponding M/G/1 queue, and hence the stationary queue length in an M/G/1 retrial queue is subexponential if the stationary queue length in the corresponding M/G/1 queue is subexponential. Our results for subexponential tails also apply to regularly varying tails, and we provide the regularly varying tail asymptotics for the stationary queue length of the M/G/1 retrial queue.
741471
Communication in disconnected ad hoc networks using message relay
An ad hoc network is formed by a group of mobile hosts upon a wireless network interface. Previous research in communication in ad hoc networks has concentrated on routing algorithms which are designed for fully connected networks. The traditional approach to communication in a disconnected ad hoc network is to let the mobile computer wait for network reconnection passively. This method may lead to unacceptable transmission delays. We propose an approach that guarantees message transmission in minimal time. In this approach, mobile hosts actively modify their trajectories to transmit messages. We develop algorithms that minimize the trajectory modifications under two different assumptions: (a) the movements of all the nodes in the system are known and (b) the movements of the hosts in the system are not known.
1659842
Partition Based Path Join Algorithms for XML Data
Path expression is an important component in querying XML data. The extended preorder numbering scheme enables us to quickly determine the ancestor-descendant relationship between elements in the hierarchy of XML data. Using the numbering scheme, a path expression can be evaluated by join operations to avoid potentially high cost of tree traversals. In this paper, we first formulate XML path queries as range-point join queries. Then we discuss the partition based algorithms that can utilize the range containment property to efficiently process the range-point join queries. Under the partition based framework, we propose three algorithms, namely Descendant partition join, Segment-tree partition join and Ancestor Link partition join, which can be chosen by a query optimizer for different input data characteristics. The experimental results show that the partition based algorithms can make better use of the buffer memory than sort-merge algorithms, and the proposed Ancestor Link join algorithm yields the best performance by using small in-memory data structures and by taking advantage of unevenly sized inputs.
2297694
Distributed cooperative Apache web server
Given explosive data traAEc in the world-wide web (WWW), it is crucial to achieve the scalable performance of web servers. The overall performance and resource utilization can be improved by spreading document requests among a group of web servers. This leads to the design and implementation of Distributed Cooperative Apache (DC-Apache) web server. In this paper, we describe the unique features of the DC-Apache system (1) to migrate and replicate documents among cooperating servers, (2) using dynamic hyperlink generation to distribute requests for documents to balance the load, and (3) to maintain replicated copies in a consistent state. We also address the issue of storage management for more e ective document replication under limited capacity. In the experiments, the DC-Apache system demonstrated its ability to achieve high performance and scalability by e ectively distributing load among a group of cooperating Apache servers and by eliminating hot spots and performance bottleneck with replicated documents. The DC-Apache system is an e ective and practical solution to provide high performance and scalability to cope with ever increasing demands from clients all over the web. keywords: WWW, Scalable Web server, Apache, DCApache, Distributed Web server, Replication, Load balancing
6512103
Indexing and Querying XML Data for Regular Path Expressions
A tone arm assembly for record players having a first motor for rotating a tone arm in the vertical direction, a second motor for rotating the tone arm in the horizontal direction with respect to a record disc, respectively, a detector for detecting low frequency vertical and horizontal vibrations of the tone arm during the reproduction of a record disc and feeding back an output signal of the detector to the motors so as to cancel the vibrations, whereby high fidelity reproduction of sounds can be performed. Further, the stylus pressure adjustment and elevation angle adjustment of the tone arm are also performed.
37613840
Improving medical/biological data classification performance by wavelet preprocessing
Many real-world datasets contain noise which could degrade the performances of learning algorithms. Motivated from the success of wavelet denoising techniques in image data, we explore a general solution to alleviate the effect of noisy data by wavelet preprocessing for medical/biological data classification. Our experiments are divided into two categories: one is of different classification algorithms on a specific database, and the other is of a specific classification algorithm (decision tree) on different databases. The experiment results show that the wavelet denoising of noisy data is able to improve the accuracies of those classification methods, if the localities of the attributes are strong enough.