ppxscal/embedding_network huggingface dataset:
Hierarchical isosurface segmentation based on discrete curvature
Authors: Fabien Vivodtzev, Georges-Pierre Bonneau, Lars Linsen, Bernd Hamann, Kenneth I. Joy, Bruno A. Olshausen
Venue: Proceedings of the symposium on Data visualisation 2003 (2003)

A high-level approach to describe the characteristics of a surface is to segment it into regions of uniform curvature behavior and construct an abstract representation given by a (topology) graph. We propose a surface segmentation method based on discrete mean and Gaussian curvature estimates. The surfaces are obtained from three-dimensional imaging data sets by isosurface extraction after data presmoothing and postprocessing the isosurfaces by a surface-growing algorithm. We generate a hierarchical multiresolution representation of the isosurface. Segmentation and graph generation algorithms can be performed at various levels of detail. At a coarse level of detail, the algorithm detects the main features of the surface. This low-resolution description is used to determine constraints for the segmentation and graph generation at the higher resolutions. We have applied our methods to MRI data sets of human brains. The hierarchical segmentation framework can be used for brain-mapping purposes.
Scheduling start time dependent tasks with deadlines and identical initial processing times on a single machine
Authors: T. C. E. Cheng, Q. Ding
Venue: Computers and Operations Research (2003)

In this paper, we study the feasibility problem of scheduling a set of start time dependent tasks on a single machine with deadlines, processing rates and identical initial processing times. First, we show that the cases with arbitrary deadlines are strongly NP-complete. Second, we show that the cases with two distinct deadlines are NP-complete in the ordinary sense. Finally, we give an optimal polynomial algorithm for the makespan problem with two distinct processing rates. We solve a series of open problems in the literature and give a sharp boundary delineating the complexity of the problems.
Low-Power Constant-Coefficient Multiplier Generator
Authors: Cheng-Yu Pai, A. J. Al-Khalili, W. E. Lynch
Venue: Journal of VLSI Signal Processing Systems (2003)

Constant-coefficient multipliers are used in many DSP cores. A new low-power constant multiplier, with detailed design procedure, is presented. By using canonical sign-digit (CSD) number system, and introducing new simplification techniques and identities, the multiplier features a new algorithm to reduce logic depth for the Wallace-tree implementation. The method also reduces area and complexity.A generator written in C++ is used to generate technology-independent VHDL code of the constant multiplier for different input specifications. Synthesis results indicate the new design has smaller area and less power consumption while offering similar speed performance when compared with other multipliers.
On interfaces projected onto real-world objects
Authors: Mark Podlaseck, Claudio Pinhanez, Nancy Alvarado, Margaret Chan, Elisa Dejesus
Venue: CHI '03 extended abstracts on Human factors in computing systems (2003)

This paper describes preliminary results of research on the perception and usability of interfaces projected onto real-world objects. Using a projector setup that enables us to compare users' color preferences, we show that the objects onto which colors are projected influence a user's choices. We also observe that many users are unable to recall and/or were unaware of the objects onto which the color interface was projected. These results suggest that there may be complex interactions affecting the use of interfaces that integrate the virtual and the real world.
z - Transform and Volterra-Operator Based Approaches to Controllability and Observability Analysis for Discrete Linear Repetitive Processes
Authors: M. Dymkov, I. Gaishun, E. Rogers, K. Galkowski, D. H. Owens
Venue: Multidimensional Systems and Signal Processing (2003)

Linear repetitive processes are a distinct class of 2D systems of both systems theoretic and applications interest. They are distinct from other classes of such systems by the fact that information propagation in one of the two separate directions only occurs over a finite duration. This, in turn, means that existing 2D systems theory either cannot be applied at all or only in substantially modified form. Hence a distinct systems theory must be developed for them with onward translation (where appropriate) into reliable routinely applicable analysis and design tools. This paper contributes substantial news results to this general task in the areas of controllability and observability for the sub-class of so-called discrete linear repetitive processes which arise in key applications areas and, in particular, iterative learning control.
Numerical analysis of dynamic characteristics of coupled piezoelectric systems in acoustic media
Authors: Roderick V. N. Melnik
Venue: Mathematics and Computers in Simulation (2003)

In this paper, the full dynamic model describing vibrations of piezoceramic solids of hollow cylindrical shapes and accounting for the coupling of the solids to surrounding fluid/gas media has been analysed numerically. The major attention has been given to the case of radial preliminary polarisation of piezoceramics where a strong coupling between electric and mechanical fields is an essential feature of the dynamics. An efficient numerical discretisation scheme based on the integro-interpolation approach has been proposed and representative examples of computational experiments are given.
Maximum norm stability of difference schemes for parabolic equations on overset nonmatching space-time grids
Authors: T. P. Mathew, G. Russo
Venue: Mathematics of Computation (2003)

In this paper, theoretical results are described on the maximum norm stability and accuracy of finite difference discretizations of parabolic equations on overset nonmatching space-time grids. We consider parabolic equations containing a linear reaction term on a space-time domain Ω × [0, T] which is decomposed into an overlapping collection of cylindrical subregions of the form Ωl*×[0, T], for l = 1,..., p. Each of the space-time domains Ωl*[0, T] are assumed to be independently grided (in parallel) according to the local geometry and space-time regularity of the solution, yielding space-time grids with mesh parameters hl and τl. In particular, the different space-time grids need not match on the regions of overlap, and the time steps τl can differ from one grid to the next. We discretize the parabolic equation on each local grid by employing an explicit or implicit θ-scheme in time and a finite difference scheme in space satisfying a discrete maximum principle. The local discretizations are coupled together, without the use of Lagrange multipliers, by requiring the boundary values on each space-time grid to match a suitable interpolation of the solution on adjacent grids. The resulting global discretization yields a large system of coupled equations which can be solved by a parallel Schwarz iterative procedure requiring some communication between adjacent subregions. Our analysis employs a contraction mapping argument.Applications of the results are briefly indicated for reaction-diffusion equations with contractive terms and heterogeneous hyperbolic-parabolic approximations of parabolic equations.
Research Report: A Reexamination of IT Investment and the Market Value of the Firm--An Event Study Methodology
Authors: Kun Shin Im, Kevin E. Dow, Varun Grover
Venue: Information Systems Research (2001)

Evaluating the effectiveness of Information Technology (IT) investments has always been an elusive but important goal of IS researchers. This study builds on a prior study that examined changes in the market value of the firm as reflected by the stock price in response to IT investment announcements. Data on stock prices were analyzed for 238 publicly traded companies. In addition to the stock price analysis, reaction of trading volume to the announcements was also examined to identify whether IT investment announcements affect investors' beliefs about IT value. Potentially confounding factors such as industry, size, and time lag effects were also analyzed. Size and time lag effects were found for all IT investment announcements. Reactions of price and volume were negatively related to firm size and became more positive over time. The positive excess return for smaller firms shows that smaller firms can leverage the lower price/performance ratio of new IT and reap greater rewards from IT investments than larger firms. Also, the result of time lag effect demonstrates that the stock market has recently begun to identify both tangible and intangible benefits of IT investments. For recent IT investment announcements, industry classification and firm size also affected the reactions of stock price to the announcements. This study provides optimism on the stock market reaction to IT investment announcements as well as further insight into the study of IT impacts on organizational performance.
Aqueous computing: a survey with an invitation to participate
Authors: Tom Head, Xia Chen, Masayuki Yamamura, Susannah Gal
Venue: Journal of Computer Science and Technology (2002)

The concept of aqueous computing is presented here, first in full generality, and afterward, using an implementation in a specific enzymatic technology. Aqueous computing arose in the context of biomolecular (DNA) computing, but the concept is independent of the specifics of its biochemical origin. Alternate technologies for realizing aqueous computing are being considered for future implementation. A solution of an instance of the Boolean satisfiability problem, (SAT), is reported here that provides a new example of an aqueous computation that has been carried out successfully. This small instance of the SAT problem is sufficiently complex to allow our current enzymatic technology to be illustrated in detail. The reader is invited to participate in the rich interdisciplinary activity required by wet lab computing. A project is suggested to the reader for determining the three-colorings of a graph. The basic operations required for this project are exhibited in the solution of the SAT example reported here.
Imagery saystems for enhanced crewmember habitability, performance and productivity on ISS
Authors: Mihriban Whitmore, Vicky Byrne
Venue: CHI '03 extended abstracts on Human factors in computing systems (2003)

In this paper, a description is provided for the process of determining the functional and technical requirements for an Imagery System onboard the International Space Station (ISS). With the advent of the ISS and the experience of Russian, European, and US crewmembers on Mir, the importance of the psychological element in long duration missions is increasingly recognized. An Imagery System could enhance the habitability, performance, and productivity for long term stays in space. Because this is type of system is a new concept for space, functional and technical requirements need to be explored.
"I enjoyed that this much!" techniques for measuring usability in leisure-oriented applications
Authors: Patrizia Marti, Paola Lanzi
Venue: The usability business: making the web work (2001)

Usability evaluation traditionally places a special emphasis on the need to develop software that is usable, i.e. used by "specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use" (ISO 9241, part 11). But what exactly does it mean to "achieve a goal" in the context of software applications for art, entertainment and leisure? Most activities in these contexts are not guided by a predefined objective based on user intention, instead, the leisure experience is a case in which individuals frequently "adjust" the way they interact with the environment, depending on many different and context-dependent factors. This chapter describes an approach to leisure-oriented usability evaluation developed around a handheld electronic museum tour guide, part of the Hyper Interaction within Physical Space (HIPS) project. It suggests that emotion, culture and context are important influences on perceived usability, and suggests how to apply these to usability away from the work environment.
Application of Gröbner bases theory to derive rate equations for enzyme catalysed reactions with two or more substrates or products
Authors: Necmettin Yildirim, Nurullah Ankaralioglu, Derya Yildrim, Fatih Akcay
Venue: Applied Mathematics and Computation (2003)

Derivation of rate equations for complex enzymatic reactions is a tedious task because of requirements of manipulation with massive algebraic expressions. This paper describes a general methodology on how to derive rate equations using Gröbner Bases Theory in Biochemical Kinetics via MAPLE. This method is valid for deriving rate laws for any enzymatic reactions regardless of the enzyme-containing species which are involved.
Learning From Failure: Towards An Evolutionary Model of Collaborative Ventures
Authors: Africa Arino, Jose De La Torre
Venue: Organization Science (1998)

This paper reports on a longitudinal case study of the interaction between two partners to a failed international joint venture. We develop a model of the collaboration process in partnership and alliances based on earlier work by Ring and Van de Ven (1994) and by Doz (1996). We employ a series of events that occurred in the course of the relationship as the unit of analysis in order to trace the interactions between the partners, and to explicate the impact that external shocks have on their perceptions of efficiency and equity. The impact of these events, as well as the responses they elicit, on the quality of the relationship (and vice versa) are also considered. We find that the partners' assessments cause them to either engage in renegotiation of the terms of the contract, or to modify their behavior unilaterally, in an attempt to restore balance to the relationship. The process feeds back until a new mutual understanding of equity is restored, or else the relationship deteriorates gradually until a point when the venture is dissolved. We conclude that positive feedback loops are critical in the evolutionary process, that relationship quality is both an outcome and a mediating variable, and that procedural issues are critical from the start in fostering a climate for positive reinforcement and the building of mutual trust and confidence in the relationship.
New implicit updates in multi-step quasi-Newton methods for unconstrained optimisation
Authors: J. A. Ford, S. Tharmlikit
Venue: Journal of Computational and Applied Mathematics (2003)

Multi-step quasi-Newton methods for optimisation (using data from more than one previous step to revise the current approximate Hessian) were introduced by Ford and Moghrabi in (J. Comput. Appl. Math. 50 (1994) 305), where they showed how to construct such methods by means of interpolating curves. These methods also utilise standard quasi-Newton formulae, but with the vectors normally employed in the formulae replaced by others determined from a multi-step version of the secant equation. Some methods (the 'accumulative' and 'fixed-point' approaches) for defining the parameter values, which correspond to the iterates on the interpolating curve, were presented by Ford and Moghrabi in (Optim. Methods Software 2 (1993) 357). Both the accumulative and the fixed-point methods measure the distances required to parameterise the interpolating polynomials via a norm defined by a positive-definite matrix M. The fixed-point algorithm which takes M to be the current approximate Hessian was found, experimentally, to be the best of the six multi-step methods studied in Ford and Moghrabi (1993) (all of which exhibited improved numerical performance by comparison with the standard single-step BFGS method).To produce a better parameterisation of the interpolation, Ford (Comput. Math. Appl. 42 (2001) 1083) developed the idea of 'implicit update' methods. The fundamental concept here is to determine an 'improved' version of the Hessian approximation to be used in computing the metric, while avoiding the computational expense of actually calculating the improved version. Two implicit methods (denoted by I2 and I3) were developed from F2 in Ford (2001). The method I2 employed parameter values generated from an implicit single-step BFGS update, while I3 used values from an implicit two-step update. In this paper, we describe the derivation of new implicit updates which are similar to I3. The experimental results we present show that one of the new implicit methods produces markedly better performance than the existing implicit methods, particularly as the dimension of the test problem grows.
Using graphs for fast error term approximation of time-varying datasets
Authors: C. Nuber, E. C. LaMar, V. Pascucci, B. Hamann, K. I. Joy
Venue: Proceedings of the symposium on Data visualisation 2003 (2003)

We present a method for the efficient computation and storage of approximations of error tables used for error estimation of a region between different time steps in time-varying datasets. The error between two time steps is defined as the distance between the data of these time steps. Error tables are used to look up the error between different time steps of a time-varying dataset, especially when run time error computation is expensive. However, even the generation of error tables itself can be expensive. For n time steps, the exact error look-up table (which stores the error values for all pairs of time steps in a matrix) has a memory complexity and pre-processing time complexity of O(n2), and O(1) for error retrieval.Our approximate error look-up table approach uses trees, where the leaf nodes represent original time steps, and interior nodes contain an average (or best-representative) of the children nodes. The error computed on an edge of a tree describes the distance between the two nodes on that edge. Evaluating the error between two different time steps requires traversing a path between the two leaf nodes, and accumulating the errors on the traversed edges. For n time steps, this scheme has a memory complexity and pre-processing time complexity of O(n log(n)), a significant improvement over the exact scheme; the error retrieval complexity is O(log(n)). As we do not need to calculate all possible n2 error terms, our approach is a fast way to generate the approximation.
Szegő polynomials: some relations to L-orthogonal and orthogonal polynomials
Authors: C. F. Bracciali, A. P. da Silva, A. Sri Ranga
Venue: Journal of Computational and Applied Mathematics (2003)

We consider the real Szegö polynomials and obtain some relations to certain self inversive orthogonal L-polynomials defined on the unit circle and corresponding symmetric orthogonal polynomials on real intervals. We also consider the polynomials obtained when the coefficients in the recurrence relations satisfied by the self inversive orthogonal L-polynomials are rotated.
Optimality of the Symmetric Workload Allocation in a Single-Server Flow Line System
Authors: Hyoungtae Kim, Sungsoo Park
Venue: Management Science (1999)

This paper provides a proof of the symmetrical allocation property (SAP), conjectured in an earlier work on the workload allocation problem for a manufacturing flow line system. The system consists of N single-Erlang servers in series having a common interstation buffer capacity. SAP says a symmetric workload allocation exists among the optimal solutions. We first show the reciprocal of the throughput is increasing and jointly convex, not component-wisely, in workloads. Then we apply the line reversibility property to obtain an alternative optimal allocation symmetric for any optimal workload allocation that is asymmetric. A sufficient condition for SAP to hold is also given, which relaxes the hypothesizing assumptions on the service-time distribution and interstation buffer capacities.
Squeeze it in or spread it out?
Authors: Rick Duley
Venue: Ubiquity (2002)

The conundrum of content and context
Finite automata on timed &#x03C9;-trees
Authors: Salvatore La Torre, Margherita Napoli
Venue: Theoretical Computer Science (2003)

In the last decade Alur and Dill introduced a model of automata on timed ω-sequences which extends the traditional models of finite automata. In this paper, we present a theory of timed ω-trees which extends both the theory of timed ω-sequences and the theory of ω-trees. The main motivation is to introduce a new way of specifying real-time systems and provide tools for studying decidability problems in related fields. We focus on the decision problems and their applications in system verification and synthesis.
Weighted sequence graphs: boosting iterated dynamic programming using locally suboptimal solutions
Authors: Benno Schwikowski, Martin Vingron
Venue: Discrete Applied Mathematics (2003)

We present a novel technique for improving a fundamental aspect of iterated dynamic programmmg procedures on sequences, such as progressive sequence alignment. Instead of relying on the unrealistic assumption that each iteration can be performed accurately without including information from other sequences, our technique employs the combinatorial data structure of weighted sequence graphs to represent an exponential number of optimal and suboptimal sequences. The usual dynamic programming algorithm on linear sequences can be generalized to weighted sequence graphs, and therefore allows to align sequence graphs instead of individual sequences in subsequent stages. Thus, locally suboptimal, but globally correct solutions can for the first time be identified through iterated sequence alignment. We demonstrate the utility of our technique by applying it to the benchmark alignment problem of Sankoff et al. (J. Mol. Evol. 7 (1976) 133). Although a recent effort could improve on the original solution from 1976 slightly, our technique leads to even more significant improvements.
Rendering vector data over global, multi-resolution 3D terrain
Authors: Zachary Wartell, Eunjung Kang, Tony Wasilewski, William Ribarsky, Nickolas Faust
Venue: Proceedings of the symposium on Data visualisation 2003 (2003)

Modern desktop PCs are capable of taking 2D Geographic Information System (GIS) applications into the realm of interactive 3D virtual worlds. In prior work we developed and presented graphics algorithms and data management methods for interactive viewing of a 3D global terrain system for desktop and virtual reality systems. In this paper we present a key data structure and associated render-time algorithm for the combined display of multi-resolution 3D terrain and traditional GIS polyline vector data. Such vector data is traditionally used for representing geographic entities such as political borders, roads, rivers and cadastral information.
A Review of Decision Support Systems in Telecare
Authors: Tasos Falas, George Papadopoulos, Andreas Stafylopatis
Venue: Journal of Medical Systems (2003)

This paper presents an overview of the state-of-the-art on decision support systems (DSS) in telecare. The main aspect examined is the use of smaller subsystems&mdash;components in an integrated DSS, with emphasis on two application areas: medical home unit monitoring and real-time prioritisation of the alerts generated by them, and drug interaction checking. The paper suggests the development of an integrated hybrid telecare DSS synthesizing most of the technologies reviewed. Implementation issues are also examined, with an emphasis on the international trend towards the development of platform-independent, component-based, distributed software.