ppxscal/embedding_network huggingface dataset:
Vertex characterization of partition polytopes of bipartitions and of planar point sets
Authors: Sharon Aviran, Nissan Lev-Tov, Shmuel Onn, Uriel G. Rothblum
Venue: Discrete Applied Mathematics (2002)

The partition problem concerns the partitioning of n given vectors in d-space into p parts, so as to maximize an objective function which is convex on the sum of vectors in each part. The problem has applications in diverse fields that include clustering, inventory, scheduling and statistical hypothesis testing. Since the objective function is convex, the partition problem can be reduced to the problem of maximizing the same objective over the partition polytope, defined to be the convex hull of all solutions. In this article we completely characterize the vertices of partition polytopes when either d=2 or p=2, and determine the maximum number of vertices of any partition polytope of n vectors when d=2 or p=2 up to a constant factor. Our characterization implies a bijection between vertices of the polytope of 0-separable partitions, and is best possible in the sense that there are examples in the literature showing the analogue fails already for p=d=3. Our enumerative results provide lower bounds on the time complexity needed to solve the partition problem when the objective function is presented by an oracle.
Should we try to squeeze database-backed websites into the curriculum: and, if so, where?
Authors: Jean Mehta
Venue: Journal of Computing Sciences in Colleges (2002)

This paper describes a set of labs packaged as a tutorial and designed to teach students how to build database-backed web sites. These labs can be used within a variety of existing courses and need only three weeks to complete. Students need prerequisite knowledge of HTML, Visual Basic or VBScript, and the ability to build a simple database using Microsoft Access. The author describes three courses in which the labs have been successfully used and documents the results. Examples of final projects are included. The appendix contains the code from one lab exercise. Student handouts can be downloaded from the tutorial website, and an instructor's guide and lab solutions are available from the author.
Power Mode Scheduling for Ad Hoc Networks
Authors: Santashil Palchaudhuri, David B. Johnson
Venue: Proceedings of the 10th IEEE International Conference on Network Protocols (2002)

An ad hoc network is a group of mobile wireless nodes that cooperatively form a network among themselves without any fixed infrastructure. Increasingly, power consumption within ad hoc networks is becoming a core issue for these low-power mobile devices. This paper focuses on a novel approach for energy conservation within the routing protocol of the ad hoc network. A wireless network interface in sleep mode expends an order of magnitude less power than in idle mode, but no packets can be sent or received while in sleep mode. In this paper, we propose two probabilistic algorithms, for scheduling transition from idle mode to sleep mode. Performance evaluation of these strategies show a substantial reduction in power usage, with only a slight decrease in performance.
Note on winning positions on pushdown games with &#x03C9;-regular conditions
Authors: Olivier Serre
Venue: Information Processing Letters (2003)

We consider infinite two-player games on pushdown graphs. For parity winning conditions, we show that the set of winning positions of each player is regular and we give an effective construction of an alternating automaton recognizing it. This provides a DEXPTIME procedure to decide whether a position is winning for a given player. Finally, using the same methods, we show, for any Ω-regular winning condition, that the set of winning positions for a given player is regular and effective.
A fast algorithm for level set-like active contours
Authors: Björn Nilsson, Anders Heyden
Venue: Pattern Recognition Letters (2003)

This paper describes a fast algorithm for topology independent tracking of moving interfaces under curvature- and velocity field-dependent speed laws. This is usually done in the level set framework using the narrow-band algorithm, which accurately solves the level set equation but is too slow to use in real-time or near real-time image segmentation applications. In this paper we introduce a fast algorithm for tracking moving interfaces in a level set-like manner. The algorithm relies on two key components: First, it tracks the interface by scheduling point-wise propagation events using a heap sorted queue. Second, the local geometric properties of the interface are defined so that they can be efficiently updated in an incremental manner and so that they do not require the presence of the signed distance function. Finally examples are given that indicate that the algorithm is fast and accurate enough for near real-time segmentation applications.
A Deadlock-Free Routing Scheme for Interconnection Networks with Irregular Topologies
Authors: Hsin-Chou Chi, Chih-Tsung Tang
Venue: Proceedings of the 1997 International Conference on Parallel and Distributed Systems (1997)

Interconnection networks with irregular topologies (or irregular networks) are ideal communication subsystems for workstation clusters owing to their incremental scalability. While many deadlock-free routing schemes have been proposed for regular networks such as mesh, torus, and hypercube, they cannot be applied in irregular networks. This paper presents a cost-effective routing architecture, called TRAIN, to solve the routing problem with irregular networks. We show that TRAIN is a deadlock-free scheme. Furthermore, unlike many other routing schemes proposed previously for irregular networks, TRAIN does not require a routing table in the switch. Due to this feature, a TRAIN switch is small and the routing decision can be made rapidly. In order to evaluate the effectiveness of our routing scheme, analysis and event-driven simulation have been performed for various irregular networks. Our results show that TRAIN outperforms other schemes with a higher maximum throughput and lower average latency consistently.
On the stability of the L2 projection in H1(&#x03A9;)
Authors: James H. Bramble, Joseph E. Pasciak, Olaf Steinbach
Venue: Mathematics of Computation (2002)

We prove the stability in H1(Ω) of the L2 projection onto a family of finite element spaces of conforming piecewise linear functions satisfying certain local mesh conditions. We give explicit formulae to check these conditions for a given finite element mesh in any number of spatial dimensions. In particular, stability of the L2 projection in H1(Ω) holds for locally quasiuniform geometrically refined meshes as long as the volume of neighboring elements does not change too drastically.
Experiences teaching writing in a computer science course for the first time
Authors: Karen Anewalt
Venue: Journal of Computing Sciences in Colleges (2002)

The concept of improving students' communication skills through writing in computer science courses has received renewed attention in the ACM/IEEE Computing Curriculum 2001 [1] as well in a recently featured column in the SIGCSE Bulletin [3]. While integrating writing into the computer science curriculum is not a new concept, it is a novel idea to many new faculty. This paper describes one instructor's first-time experiences in offering a computer science course with a strong writing component and encourages others to consider focusing more attention on writing instruction. Techniques used by the author to create clear assignments and simplify grading are described. An example of a paper assignment and grading rubric used in a second semester introductory programming course are provided. Examples of shorter writing assignments appropriate for the same course are also included.
Color waves: a simple heuristic for choosing false colors
Authors: C. W. A. M. van Overveld
Venue: Journal of Graphics Tools (1998)

A simple heuristic is presented for choosing false colors for visualizing scalar functions on two-dimensional domains. The color scheme allows inspection of the function on several length scales simultanously.
D-Optimal Sequential Experiments for Generating a Simulation-Based Cycle Time-Throughput Curve
Authors: Sungmin Park, John W. Fowler, Gerald T. Mackulak, J. Bert Keats, W. Matthew Carlyle
Venue: Operations Research (2002)

A cycle time-throughput curve quantifies the relationship of average cycle time to throughput rates in a manufacturing system. Moreover, it indicates the asymptotic capacity of a system. Such a curve is used to characterize system performance over a range of start rates. Simulation is a fundamental method for generating such curves since simulation can handle the complexity of real systems with acceptable precision and accuracy. A simulation-based cycle time-throughput curve requires a large amount of simulation output data; the precision and accuracy of a simulated curve may be poor if there is insufficient simulation data. To overcome these problems, sequential simulation experiments based on a nonlinear D-optimal design are suggested. Using the nonlinear shape of the curve, such a design pinpointsp starting design points, and then sequentially ranks the remainingn --p candidate design points, wheren is the total number of possible design points being considered. A model of a semiconductor wafer fabrication facility is used to validate the approach. The sequences of experimental runs generated can be used as references for simulation experimenters.
Interference evaluation of Bluetooth and IEEE 802.11b systems
Authors: N. Golmie, R. E. Van Dyck, A. Soltanian, A. Tonnerre, O. Rébala
Venue: Wireless Networks (2003)

The emergence of several radio technologies, such as Bluetooth and IEEE 802.11, operating in the 2.4 GHz unlicensed ISM frequency band, may lead to signal interference and result in significant performance degradation when devices are colocated in the same environment. The main goal of this paper is to evaluate the effect of mutual interference on the performance of Bluetooth and IEEE 802.11b systems. We develop a simulation framework for modeling interference based on detailed MAC and PHY models. First, we use a simple simulation scenario to highlight the effects of parameters, such as transmission power, offered load, and traffic type. We then turn to more complex scenarios involving multiple Bluetooth piconets and WLAN devices.
Yes, "Bait and Switch" Really Benefits Consumers
Authors: James D. Hess, Eitan Gerstner
Venue: Marketing Science (1998)

In our 1990 Marketing Science paper we demonstrated that a law prohibiting bait and switch may have the surprising consequence of hurting the consumers it was designed to protect. Wilkie, Mela, and Gundlach (1998) postulate that this may be false if up selling is equally effective when the bait brand is available and when it is out of stock. We show here that our earlier conclusion is correct in a more general setting: A law prohibiting bait and switch in a competitive market can reduce consumer well-being but never improve it. When bait and switch occurs, it creates welfare gains, and when it would create welfare losses, it does not occur, regardless of a law prohibiting the practice.
Design of a Cellular Architecture for Fast Computation of the Skeleton
Authors: N. Sudha
Venue: Journal of VLSI Signal Processing Systems (2003)

This paper presents a new algorithm to extract the skeleton and its Euclidean distance values from a binary image. The extracted skeleton reconstructs the objects in the image exactly. The algorithm runs in O(n) time for an image of size n &times; n. It involves simple local neighborhood operations for each pixel and hence it is quite amenable to VLSI implementation in a cellular architecture. Results of simulation of the algorithm in a sequential computer are presented. Results of implementation of a VLSI design in Xilinx FPGA are also presented and they confirm the speed and suitability of our method for real-time applications.
Points of learning and teaching systems (POLTS)
Authors: M. O. Thirunarayanan
Venue: Ubiquity (2002)

Educators can take a lesson from the business world's use of dedicated computer systems.
Information Technology and Firm Boundaries: Evidence From Panel Data
Authors: Mary J. Culnan, Pamela K. Armstrong, Lorin M. Hitt
Venue: Information Systems Research (1999)

Previous literature has suggested that information technology (IT) can affect firm boundaries by changing the costs of coordinating economic activity within and between firms (internal and external coordination). This paper examines the empirical relationship between IT and firm structure and evaluates whether this structure is consistent with prior arguments about IT and coordination. We formulate an empirical model to relate the use of information technology capital to vertical integration and diversification. This model is tested using an 8-year panel data set of information technology capital stock, firm structure, and relevant control variables for 549 large firms. Overall, increased use of IT is found to be associated with substantial decreases in vertical integration and weak increases in diversification. In addition, firms that are less vertically integrated and more diversified have a higher demand for IT capital. While we cannot rule out all alternative explanations for these results, they are consistent with previous theoretical arguments that both internal and external coordination costs are reduced by IT.
Common-Lines and Passenger Assignment in Congested Transit Networks
Authors: Roberto Cominetti, José Correa
Venue: Transportation Science (2001)

We analyze a Wardrop equilibrium model for passenger assignment in general transit networks, including the effects of congestion over the passengers' choices. The model is based on the common-line paradigm, which is applied to general networks using a dynamic programming approach. Congestion is treated by means of a simplified bulk queue model described in the appendix. We provide a complete characterization of the set of equilibria in the common-line setting, including the conditions for existence and uniqueness. This characterization reveals the existence of ranges of flow in which a Braess-like paradox appears, and in which a flow increase does not affect the system performance as measured by transit times. The congested common-line model is used to state an equilibrium model for general transit networks, and to establish the existence of a network equilibrium.
A Multiattribute Utility Analysis of Alternatives for the Disposition of Surplus Weapons-Grade Plutonium
Authors: James S. Dyer, Thomas Edmunds, John C. Butler, Jianmin Jia
Venue: Operations Research (1998)

This paper describes an application of multiattribute utility theory to support the selection of a technology for the disposition of surplus weapons-grade plutonium by the Department of Energy (DOE). This analysis evaluated 13 alternatives, examined the sensitivity of the recommendations to the weights and assumptions, and quantified the potential benefit of the simultaneous deployment of several technologies. The measures of performance that were identified through the creation of a hierarchy of objectives helped to organize the information collected during the evaluation process, and the results of the analysis were presented to DOE on several occasions. This analysis supported the final DOE recommendation to pursue a strategy of the parallel development of two of the most preferred technologies.
You're in control: a urinary user interface
Authors: Dan Maynes-Aminzade, Hayes Raffle
Venue: CHI '03 extended abstracts on Human factors in computing systems (2003)

The You're In Control system uses computation to enhance the act of urination. Sensors in the back of a urinal detect the position of impact of a stream of urine, enabling the user to play interactive games on a screen mounted above the urinal.
Semantic integration in Xyleme: a uniform tree-based approach
Authors: Claude Delobel, Chantal Reynaud, Marie-Christine Rousset, Jean-Pierre Sirot, Dan Vodislav
Venue: Data Knowledge Engineering (2003)

Xyleme is a huge warehouse integrating XML data of the Web. Xyleme considers a simple data model with data trees and tree types for describing the data sources, and a simple query language based on tree queries with boolean conditions. The main components of the data model are a mediated schema modeled by an abstract tree type, as a view of a set of tree types associated with actual data trees, called concrete tree types, and a mapping expressing the connection between the mediated schema and the concrete tree types. The first contribution of this paper is formal: we provide a declarative model-theoretic semantics for Xyleme tree queries, a way of checking tree query containment, and a characterization of tree queries as a composition of branch queries. The other contributions are algorithmic and handle the potentially huge size of the mapping relation which is a crucial issue for semantic integration and query evaluation in Xyleme. First, we propose a method for pre-evaluating queries at compile time by storing some specific meta-information about the mapping into map translation tables. These map translation tables summarize the set of all the branch queries that can be generated from the mediated schema and the set of all the mappings. Then, we propose different operators and strategies for relaxing queries which, having an empty map translation table, will have no answer if they are evaluated against the data. Finally, we present a method for semi-automatically generating the mapping relation.
A spectral solver for the three-dimensional Navier-Stokes equations in velocity-vorticity formulation
Authors: M. F. M. Speetjens
Venue: Scientific computing and applications (2001)

A numerical algorithm intended for the study of flows in a cylindrical container under laminar flow conditions is proposed. High resolution of the flow field, governed by the Navier-Stokes equations in velocity-vorticity formulation relative to a cylindrical frame of reference, is achieved through spatial discretization by means of the spectral method. This method is based on a Fourier expansion in the azimuthal direction and an expansion in Chebyshev polynomials in the (nonperiodic) radial and axial directions. Several regularity constraints are used to take care of the coordinate singularity. These constraints are implemented, together with the boundary conditions at the top, bottom and mantle of the cylinder, via the tau method. The a priori unknown boundary values of the vorticity are evaluated by means of the influence matrix technique. The compatibility between the mathematical and numerical formulation of the Navier-Stokes equations is established through a tau correction procedure. The resolved flow field meets the incompressibility constraint and definition of the vorticity up to machine accuracy.
H-Convergence and Numerical Schemes for Elliptic Problems
Authors: Robert Eymard, Thierry Gallouët
Venue: SIAM Journal on Numerical Analysis (2003)

We study the convergence of two coupled numerical schemes, which are a discretization of a so-called elliptic-hyperbolic system. Only weak convergence properties are proved on the discrete diffusion of the elliptic problem, and an adaptation of the H-convergence method gives a convergence property of the elliptic part of the scheme. The limit of the approximate solution is then the solution of an elliptic problem, the diffusion of which is not in the general case the H-limit of the discrete diffusion. In a particular case, a kind of weak limit is then obtained for the hyperbolic equation.
Error bounds for a general perturbation of the Drazin inverse
Authors: J. J. Koliha
Venue: Applied Mathematics and Computation (2002)

The paper solves a long standing problem of finding error bounds for a general perturbation of the Drazin inverse. The bounds are given in terms of the distance between the matrices together with the distance between their eigenprojections. Estimates using the gap between subspaces are also given. Recent results of several authors, including Castro, Koliha, Straskraba (Soochov J. Math., to appear) Wang and Wei (Linear Algebra Appl. 258 (1997) 179-186) can be recovered as special cases of our theorems.
Variations of the GMRES iterative method
Authors: David R. Kincaid, David M. Young, Jen-Yuan Chen
Venue: Applied Numerical Mathematics (2003)

We give a brief overview of the GGMRES method, the MGMRES method, and the LAN/MGMRES method, which are generalizations and modifications of the Generalized Minimum Residual (GMRES) method.
Some results on starlike trees and sunlike graphs
Authors: Mirko Lepović
Venue: The Korean Journal of Computational Applied Mathematics (2003)

A tree is called starlike if it has exactly one vertex of degree greater than two. In [4] it was proved that two starlike trees G and H are cospectral if and only if they are isomorphic. We prove here that there exist no two non-isomorphic Laplacian cospectral starlike trees. Further, let G be a simple graph of order n with vertex set V(G) = {1,2 ....,n} and let H = {H1,H2,...,Hn} be a family of rooted graphs. According to [2], the rooted product G(H) is the graph obtained by identifying the root of Hi with the i-th vertex of G. In particular, if H is the family of the paths Pk1, Pk2, ..., Pkn with the rooted vertices of degree one, in this paper the corresponding graph G(H) is called the sunlike graph and is denoted by G(k1,k2,...,kn). For any (x1,x2,...,xn) ∈ I*n, where I* = {0,1}, let G(x1,x2,.....xn) be the subgraph of G which is obtained by deleting the vertices i1,i2,...,ij ∈ V(G) (0 ≤ j ≤ n), provided that xi1 = xi2 =..... = xij = 0. Let G[x1, x2 .... , xn] be the characteristic polynomial of G(x1, x2,.., xn), understanding that G[0,0,..., 0] ≡ 1. We prove that G[k1,k2 ....., kn] = Σx∈I*n [Πi=1n Pki+xi-2(λ)](-1)n-(Σi=1n xi) G[x1,x2 ....., xn] where X = (x1,x2,...,xn); G[k1,k2,...,kn] and Pn(λ denote the characteristic polynomial of G(k1,k2 ....,kn) and Pn, respectively. Besides, if G is a graph with λ1(G) ≥ 1 we show that λ1(G) ≤ λ1(G(k1,k2,...,kn)) > λ1(G) + λ1-1(G) for all positive integers k1, k2....,kn, where λ1 denotes the largest eigenvalue.
Developing 3-d animated applications prototypes in the classroom
Authors: Alexandre Passos, Richard Simpson
Venue: Journal of Computing Sciences in Colleges (2002)

Simulated environments, such as those found in training centers, computer games, movies, advertisement and defense applications, require software companies to face two important challenges in today's economy: creating a good prototype as showcase for the end-user and meeting "time to market" deadlines. Graphics libraries and development environments provide to the application programmer the necessary interfaces used in the construction of graphics, animations, simulations and games. The true value of a graphics library can be measured from two issues: ease of use and extensibility. However, the special needs in an educational environment change the shape and form of graphics frameworks such that each library must be designed to accommodate ease of use and extensibility. Such frameworks provide the user-friendly environment required by, for example, novice game programmers. This study presents a new game-programming library called PGL that addresses the timing and learning factors that exist in game development.