ppxscal/embedding_network huggingface dataset:
Classification of Linear Periodic Difference Equations under Periodic or Kinematic Similarity
Authors: I. Gohberg, M. A. Kaashoek, J. Kos
Venue: SIAM Journal on Matrix Analysis and Applications (1999)

In this paper linear periodic systems of difference equations are classified with respect to periodic similarity and kinematic similarity. Complete sets of invariants of periodic difference equations relative to such similarity transformations are given, and corresponding canonical forms are described. Also the irreducible periodic difference equations, i.e., those that cannot be reduced by such similarities to a nontrivial direct sum, are identified.
Empirical Data Modeling in Software Engineering Using Radial Basis Functions
Authors: Miyoung Shin, Amrit L. Goel
Venue: IEEE Transactions on Software Engineering (2000)

Many empirical studies in software engineering involve relationships between various process and product characteristics derived via linear regression analysis. In this paper, we propose an alternative modeling approach using Radial Basis Functions (RBFs) which provide a flexible way to generalize linear regression function. Further, RBF models possess strong mathematical properties of universal and best approximation. We present an objective modeling methodology for determining model parameters using our recent SG algorithm, followed by a model selection procedure based on generalization ability. Finally, we describe a detailed RBF modeling study for software effort estimation using a well-known NASA dataset.
In vivo high resolution 3D-QCT of the human forearm
Authors: Andres Laib, Hans Jörg Häuselmann, Peter Rüegsegger
Venue: Technology and Health Care (1998)

In vivo examinations of bone microarchitecture have become available recently through high resolution computed tomography (3D-QCT) and magnetic resonance imaging. The spatial resolution of the resulting images, however, is not sufficient to depict individual trabeculae in their true shape. Nevertheless, structural indices such as relative bone volume, trabecular number, mean thickness and mean separation can be extracted with the help of a ridge detection algorithm. Precision of the procedure is of the order of 1%, accuracy is ascertained using a micro-CT based calibration. In this work we report first results of time serial examinations. Eighteen healthy postmenopausal women (no HRT) were measured at months 0, 6, and 12, and the temporal changes were analyzed. Examination site was the distal radius. The above mentioned structural indices, the average densities and the thickness of the cortical shell were determined. Of the 18 women 6 showed no significant bone loss of any kind, 5 lost primarily cancellous bone, 4 lost primarily cortical bone, and 3 had a substantial loss of cortical as well as cancellous bone. We conclude that even in a homogenous group such as postmenopausal women, there are considerable differences in the reason why bone is weakend and that high resolution 3D-QCT allows to differentiate between various types of bone loss.
Alice: lessons learned from building a 3D system for novices
Authors: Matthew Conway, Steve Audia, Tommy Burnette, Dennis Cosgrove, Kevin Christiansen
Venue: Proceedings of the SIGCHI conference on Human factors in computing systems (2000)

We present lessons learned from developing Alice, a 3D graphics programming environment designed for undergraduates with no 3D graphics or programming experience. Alice is a Windows 95/NT tool for describing the time-based and interactive behavior of 3D objects, not a CAD tool for creating object geometry. Our observations and conclusions come from formal and informal observations of hundreds of users. Primary results include the use of LOGO-style egocentric coordinate systems, the use of arbitrary objects as lightweight coordinate systems, the launching of implicit threads of execution, extensive function overloading for a small set of commands, the careful choice of command names, and the ubiquitous use of animation and undo.
The ANIMAL algorithm animation tool
Authors: Guido Rößling, Markus Schüer, Bernd Freisleben
Venue: ACM SIGCSE Bulletin (2000)

In this paper, we present Animal, a new tool for developing animations to be used in lectures. Animal offers a small but powerful set of graphical operators. Animations are generated using a visual editor, by scripting or via API calls. All animations can be edited visually. Animal supports source and pseudo code inclusion and highlighting as well as precise user-defined delays between actions. The paper evaluates the functionality of Animal in comparison to other animation tools.
Anatomy of a real E-commerce system
Authors: Anant Jhingran
Venue: ACM SIGMOD Record (2000)

Today's E-Commerce systems are a complex assembly of databases, web servers, home grown glue code, and networking services for security and scalability. The trend is towards larger pieces of these coming together in bundled offerings from leading software vendors, and the networking/hardware being offered through service delivery companies. In this paper we examine the bundle by looking in detail at IBM's WebSphere, Commerce Edition, and its deployment at a major customer site.
Software evolution in componentware using requirements/assurances contracts
Authors: Andreas Rausch
Venue: Proceedings of the 22nd international conference on Software engineering (2000)

In practice, pure top-down and refinement-based development processes are not sufficient. Usually, an iterative and incremental approach is applied instead. Existing methodologies, however, do not support such evolutionary development processes very well. In this paper, we present the basic concepts of an overall methodology based on component ware and software evolution. The foundation of our methodology is a novel, well-founded model for component-based systems. This model is sufficiently powerful to handle the fundamental structural and behavioral aspects of component ware and object-orientation. Based on the model, we are able to provide a clear definition of a software evolution step.During development, each evolution step implies changes of an appropriate set of development documents. In order to model and track the dependencies between these documents, we introduce the concept of Requirements/Assurances Contracts. These contracts can be rechecked whenever the specification of a component evolves, enabling us to determine the impacts of the respective evolution step. Based on the proposed approach, developers are able to track and manage the software evolution process and to recognize and avoid failures due to software evolution. A short example shows the usefulness of the presented concepts and introduces a practical description technique for Requirements/Assurances Contracts.
Tele-Education in a Telemedicine Environment: Implications for Rural Health Care and Academic Medical Centers
Authors: Susan A. Zollo, Michael G. Kienzle, Zak Henshaw, Louis G. Crist, Douglas S. Wakefield
Venue: Journal of Medical Systems (1999)

Over 50 million people in the United States (about 20% of the population) live in rural areas, but only 9% of the nation's physicians practice in rural communities. It is difficult to recruit and retain rural health care practitioners, partly because of issues relating to professional isolation. New and enhanced telecommunications links between community and academic hospitals show promise for reducing this isolation and enhancing lifelong learning opportunities for rural health care providers. This paper will explore some of the issues involved in using interactive video (telemedicine) networks to transmit continuing medical education programming from an academic center to multiple rural hospitals. Data from a recent University of Iowa survey of the state's health educators will be presented as one approach to assessing the health care marketplace for the deployment of tele-education services.
A Family of Variable-Precision Interval Arithmetic Processors
Authors: Michael J. Schulte, Earl E. Swartzlander,  Jr.
Venue: IEEE Transactions on Computers (2000)

Traditional computer systems often suffer from roundoff error and catastrophic cancellation in floating point computations. These systems produce apparently high precision results with little or no indication of the accuracy. This paper presents hardware designs, arithmetic algorithms, and software support for a family of variable-precision, interval arithmetic processors. These processors give the programmer the ability to detect and, if desired, to correct implicit errors in finite precision numerical computations. They also provide the ability to solve problems that cannot be solved efficiently using traditional floating point computations. Execution time estimates indicate that these processors are two to three orders of magnitude faster than software packages that provide similar functionality.
AJAX: an extensible data cleaning tool
Authors: Helena Galhardas, Daniela Florescu, Dennis Shasha, Eric Simon
Venue: ACM SIGMOD Record (2000)

@@@@ groups together matching pairs with a high similarity value by applying a given grouping criteria (e.g. by transitive closure). Finally, ging collapses each individual cluster into a tuple of the resulting data source. AJAX provides @@@@ for specifying data cleaning programs, which consists of SQL statements enriched with a set of specific primitives to express these transformations.AJAX also @@@@. It allows the user to interact with an executing data cleaning program to handle exceptional cases and to inspect intermediate results. Finally, AJAX provides @@@@ @@@@ that permits users to determine the source and processing of data for debugging purposes.We will present the AJAX system applied to two real world problems: the consolidation of a telecommunication database, and the conversion of a dirty database of bibliographic references into a set of clean, normalized, and redundancy free relational tables maintaining the same data.
Asthma Outcome Measures
Authors: Kevin D. Watkins
Venue: Journal of Medical Systems (1999)

Annually, asthma accounts for 10.4 million physician visits, 468,000 hospitalizations, 1.8 million emergency room visits, and 10 million missed school days. According to the Centers for Disease Control and Prevention, the number of asthma deaths has increased progressively since 1978 form 1,800 to 5,400 per year. It is an expensive disease, accounting for about 1% of all health expenditure in the United States in 1990. Asthma has a significant impact on the patient and the community at large and the assessment of the clinical, physiologic, humanistic and economic outcomes will be measured.
A Shape Metric for Blum Ribbons
Authors: M. Kerckhove
Venue: Journal of Mathematical Imaging and Vision (1999)

A Blum ribbon is a figure whose boundary is the envelope of a family of circles the centers of which lie along a single unbranched curve called its medial axis. Define a Blum ribbon to be simple if its medial axis is the line segment joining points (0,0) and (1,0). Any Blum ribbon can be made simple by flexing the medial axis, rotating, then dilating, all of which are basic transformations in Blum&lsquo;s geometry of shape. The Lie group SL(2, R) acts on circles centered on the x-axis by linear fractional transformations. By means of this action it is possible to associate to any simple Blum ribbon a curve in SL(2, R). A distance between corresponding points lying on such curves is defined using the bi-invariant metric on SL(2, R). Resulting scale-invariant metrics on the set of figures defined as Blum ribbons are described and it is shown that these metrics can provide effective measures of shape difference.
Convergence Results for Single-Step On-PolicyReinforcement-Learning Algorithms
Authors: Satinder Singh, Tommi Jaakkola, Michael L. Littman, Csaba Szepesvári
Venue: Machine Learning (2000)

An important application of reinforcement learning (RL) is to finite-state control problems and one of the most difficult problems in learning for control is balancing the exploration/exploitation tradeoff. Existing theoretical results for RL give very little guidance on reasonable ways to perform exploration. In this paper, we examine the convergence of single-step on-policy RL algorithms for control. On-policy algorithms cannot separate exploration from learning and therefore must confront the exploration problem directly. We prove convergence results for several related on-policy algorithms with both decaying exploration and persistent exploration. We also provide examples of exploration strategies that can be followed during learning that result in convergence to both optimal values and optimal policies.
The Median Stabilization Degree of a Median Algebra
Authors: H.-J. Bandelt, M. Van De Vel
Venue: Journal of Algebraic Combinatorics: An International Journal (1999)

The median stabilization degree (msd, for short) of a median algebra measures the largest possible number of steps needed to generate a subalgebra with an arbitrary set of generators. We determine the value of msd of a graphic n-cube Qn and we derive an estimation of msd for the natural median operator of Rn which is sharp up to one or two units. Interestingly, msd of Qn and of Rn grows like log1.5n. Finally, we characterize median algebras and median graphs of msd &le; 1 in terms of forbidden subspaces.
Preserving digital information forever
Authors: Andrew Waugh, Ross Wilkinson, Brendan Hills, Jon Dell'oro
Venue: Proceedings of the fifth ACM conference on Digital libraries (2000)

Well within our lifetime we can expect to see most information being created, stored and used digitally. Despite the growing importance of digital data, the wider community pays almost no attention to the problems of preserving this digital information for the future. Even within the archival and library communities most work on digital preservation has been theoretical, not practical, and highlights the problems rather than giving solutions. Physical libraries have to preserve information for long periods and this is no less true of their digital equivalents. This paper describes the preservation approach adopted in the Victorian Electronic Record Strategy (VERS) which is currently being trialed within the Victorian government, one of the states of Australia. We review the various preservation approaches that have been suggested and describe in detail encapsulation, the approach which underlies the VERS format. A key difference between the VERS project and previous digital preservation projects is the focus within VERS on the construction of actual systems to test and implement the proposed technology. VERS is not a theoretical study in preservation.
Quickly detecting relevant program invariants
Authors: Michael D. Ernst, Adam Czeisler, William G. Griswold, David Notkin
Venue: Proceedings of the 22nd international conference on Software engineering (2000)

Explicitly stated program invariants can help programmers by characterizing certain aspects of program execution and identifying program properties that must be preserved when modifying code. Unfortunately, these invariants are usually absent from code. Previous work showed how to dynamically detect invariants from program traces by looking for patterns in and relationships among variable values. A prototype implementation, Daikon, accurately recovered invariants from formally-specified programs, and the invariants it detected in other programs assisted programmers in a software evolution task. However, Daikon suffered from reporting too many invariants, many of which were not useful, and also failed to report some desired invariants.This paper presents, and gives experimental evidence of the efficacy of, four approaches for increasing the relevance of invariants reported by a dynamic invariant detector. One of them &mdash; exploiting unused polymorphism &mdash; adds desired invariants to the output. The other three &mdash; suppressing implied invariants, limiting which variables are compared to one another, and ignoring unchanged values &mdash; eliminate undesired invariants from the output and also improve runtime by reducing the work done by the invariant detector.
Efficient Execution of Time Warp Programs on Heterogeneous, NOW Platforms
Authors: Christopher D. Carothers, Richard M. Fujimoto
Venue: IEEE Transactions on Parallel and Distributed Systems (2000)

Time Warp is an optimistic protocol for synchronizing parallel discrete event simulations. To achieve performance in a multiuser network of workstation (NOW) environment, Time Warp must continue to operate efficiently in the presence of external workloads caused by other users, processor heterogeneity, and irregular internal workloads caused by the simulation model. However, these performance problems can cause a Time Warp program to become grossly unbalanced, resulting in slower execution. The key observation asserted in this article is that each of these performance problems, while different in source, has a similar manifestation. For a Time Warp program to be balanced, the amount of wall clock time necessary to advance an LP one unit of simulation time should be about the same for all LPs. Using this observation, we devise a single algorithm that mitigates these performance problems and enables the ¿background¿ execution of Time Warp programs on heterogeneous distributed computing platforms in the presence of external as well as irregular internal workloads.
Iterative Substructuring Methods for Spectral Element Discretizations of Elliptic Systems. II: Mixed Methods for Linear Elasticity and Stokes Flow
Authors: Luca F. Pavarino, Olof B. Widlund
Venue: SIAM Journal on Numerical Analysis (1999)

Iterative substructuring methods are introduced and analyzed for saddle point problems with a penalty term. Two examples of saddle point problems are considered: The mixed formulation of the linear elasticity system and the generalized Stokes system in three dimensions. These problems are discretized with %mixed spectral element methods. The resulting stiffness matrices are symmetric and indefinite. The interior unknowns of each element are first implicitly eliminated by using exact local solvers. The resulting saddle point Schur complement is solved with a Krylov space method with block preconditioners. The velocity block can be approximated by a domain decomposition method, e.g., of wire basket type, which is constructed from a local solver for each face of the elements, and a coarse solver related to the wire basket of the elements. The condition number of the preconditioned operator is independent of the number of spectral elements and is bounded from above by the product of the square of the logarithm of the spectral degree and the inverse of the discrete inf-sup constant of the problem.
On the expressive power of database queries with intermediate types
Authors: Richard Hull, Jianwen Su
Venue: Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems (1988)

The set-height of a complex object type is defined to be its level of nesting of the set construct. In a query of the complex object calculus which maps a database D to an output type T, an intermediate type is a type which is used by some variable of the query, but which is not present in D or T. For each k, i &ge; 0 we define CALCk,i to be the family of calculus queries mapping from and to types with set-height &le; k and using intermediate types with set-height &le; i In particular, CALC0,0 is the relational calculus, and CALC0,1 is equivalent to the family of second-order (relational) queries Several results concerning these families of languages are obtained. A primary focus is on the families CALC0,i, which map relations to relations Upper bounds on the complexity of these families are provided, and it is shown that CALC0,3 has at least the complexity of exponential space. The CALC0,i hierarchy does not collapse, because for each i, CALC0,i is strictly less expressive than CALC0,i+2. The union &cup;0&le;iCALC0,i is strictly less expressive than the family of 'computable' database queries. The expressive power of queries from the complex object calculus interpreted using a semantics based on the use of arbitrarily large finite numbers of invented values is studied. Under this semantics, the expressive power of the relational calculus is not increased, and the CALC0,i hierarchy collapses at CALC0,1. We also consider queries which use a bounded number of invented values.
A Wavelet-Based Nonparametric Estimator ofthe Variance Function
Authors: Zuohong Pan, Xiaodi Wang
Venue: Computational Economics (2000)

A new wavelet-based nonparametric estimator is introduced in an effort to approximate variance functions. The new estimator possesses some superior qualities that are illustrated through its actual performance in some simulations.
Fluids in the universe: adaptive mesh refinement in cosmology
Authors: Greg L. Bryan
Venue: Computing in Science and Engineering (1999)

Using galactic clusters, galactic formation, and the first stars as examples, the author demonstrates how adaptive mesh refinement techniques can be successfully applied to cosmological research.
A database perspective on Lotus Domino/Notes
Authors: C. Mohan
Venue: Proceedings of the 1999 ACM SIGMOD international conference on Management of data (1999)

In this one-page summary, I introduce the database aspects of Lotus Domino/Notes. These database features are covered in detail in the corresponding SIGMOD99 tutorial available at www.almaden.ibm.com/u/mohan/domino_sigmod99.ps.
The need for distributed asynchronous transactions
Authors: Lyman Do, Prabhu Ram, Pamela Drew
Venue: ACM SIGMOD Record (1999)

The theme of the paper is to promote research on asynchronous transactions. We discuss our experience of executing synchronous transactions on a large distributed production system in The Boeing Company. Due to the poor performance of synchronous transactions in our environment, it motivated the exploration of asynchronous transactions as an alternate solution. This paper presents the requirements and benefits/limitations of asynchronous transactions. Open issues related to large scale deployments of asynchronous transactions are also discussed.
Minimization of Functionals of the Gradient by Baire's Theorem
Authors: Sandro Zagatti
Venue: SIAM Journal on Control and Optimization (2000)

We give sufficient conditions for the existence of solutions of the minimum problem $$ {\cal P}_{u_0}: \qquad \hbox{Minimize}\quad \int_\Omega g(Du(x))dx, \quad u\in u_0 + W_0^{1,p}(\Omega,{\Bbb R}), $$ based on the structure of the epigraph of the lower convex envelope of g, which is assumed be lower semicontinuous and to grow at infinity faster than the power p with p larger than the dimension of the space. No convexity conditions are required on g, and no assumptions are made on the boundary datum $u_0\in W_0^{1,p}(\Omega,{\Bbb R})$.
On the global fanout optimization problem
Authors: Rajeev Murgai
Venue: Proceedings of the 1999 IEEE/ACM international conference on Computer-aided design (1999)

Fanout optimization is a fundamental problem in timing optimization. Most of the research has focussed on the fanout optimization problem for a single net (or the local fanout optimization problem LFO). The real goal, however, is to optimize the delay through the entire circuit by fanout optimization. This is the global fanout optimization (GFO) problem. Touati claims in his thesis [6] that visiting nets of the network in a reverse topological order (from primary outputs to inputs), applying the optimum LFO algorithm to each net, computing the new required time at the source and propagating the delay changes to the fanins yields a provably optimum solution to the GFO problem. This result implies that GFO is solvable in polynomial time if LFO is. In this paper, we show that that is not the case. We prove that GFO is NP-complete even if there are a constant number of buffering choices at each net. We analyze Touati's result and point out the flaw in his argument. We then present sufficient conditions for the optimality of the reverse topological algorithm.