ppxscal/embedding_network huggingface dataset:
Separating Reflection Functions for Linear Radiosity
Authors: Alain Fournier
Venue:  (1995)

Classic radiosity assumes diffuse reflectors in order to consider only pair-wise exchanges of light between elements. It has been previously shown that one can use the same system of equations with separable bi-directional reflection distrubution functions (BRDFs), that is BRDFs that can be put in the form of a product of two functions, one of the incident direction and one of the reflected direction. We show here that this can be easily extended to BRDFs that can be approximated by sums of such terms. The classic technique of Singular Value Decomposition (SVD) can be used to compute those terms given an analytical or experimental BRDF. We use the example of the traditional Phong model for specular-like reflection to extract a separable model, and show the results in terms of closeness to ordinary Phong shading. We also show an example with experimental BRDF data. Further work will indicate whether the quality of linear radiosity images will be improved by this modification. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
The dynamic behaviour of a cracked beam subjected to a white noise input
Authors: P. Cacciola, N. Impollonia, G. Muscolino
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

The aim of this paper is to inspect the vibration response of a beam with an edge non-propagating crack by means of stochastic analysis, in order to detect the presence of the structural damage. Monte Carlo method is applied to evaluate in the time domain the higher order statistics of the non-linear beam modelled by finite elements. The numerical application performed on a cantilever beam shows high sensitivity of the skewness coefficient of the rotational degrees of freedom to the non-linear behaviour of the system. By observation of such coefficient both crack presence and position can be estimated. The proposed procedure allows treating beam with small crack even when other techniques fail to identify the crack presence.
The Parallel Performance of Schwarz Splitting
Authors: Calvin J. Ribbens, Layne T. Watson
Venue:  (1990)

We describe several experiments with implementations of Schwarz splitting algorithms for the numerical solution of elliptic partial differential equations. Results from experiments comparing several variations of the basic scheme in the context of real parallel implementations are presented. Both shared-memory and distributed-memory architectures are represented. Various possibilities for accelerating the Schwarz iteration and for solving the subdomain problems are considered, with particular emphasis on the resulting parallel performance.
Analysis of Quorum-Based Protocols for Distributed (k+1)-Exclusion
Authors: Divyakant Agrawal, Omer Egecioglu, Amr El Abbadi
Venue:  (1996)

A generalization of the majority quorum for the solution of the distributed (k+1)-exclusion problem is proposed. This scheme produces a family of quorums of varying sizes and availabilities indexed by integral divisors r of k. The cases r=1 and r=k correspond to known majority based quorum generation algorithms MAJ and DIV, whereas intermediate values of r interpolate between these two extremes. A cost and availability analysis of the proposed methods is also presented. An interesting result of this analysis is that in a reasonably reliable environment with a large number of sites, even protocols with low communication costs attain high availability.
Sequence constraints in business modelling and business process modelling
Authors: Monique Snoeck
Venue: Enterprise information systems IV (2003)

Separation of concerns is one of the main principles for achieving maintainability and adaptability of software systems. In particular, when analysing business rules it is important to separate business process aspects from essential business rules. Current object-oriented analysis methods offer little support for this. In this paper we explore the problem of sequence constraints on business events. Some of these constraints are the result of the way the business is organised whereas other are essential for the business. In addition we investigate how to ensure the compatibility between business rules and business processes.
Formative Evaluation: Ensuring Usability in User Interfaces
Authors: Deborah Hix, H. R Hartson
Venue:  (1992)

Ensuring usability has become a key goal of interactive system development, as developers have begun to realize that it matters little how effectively an interactive system can compute, if human users cannot communicate effectively with the system. In this paper we discuss what we have found to be two main types of formative user interface evaluation: analytic and empirical. Both these types occur as part of the development process. We do not attempt to survey all approaches to either of these types of formative evaluation, but rather to offer a sampling of some approaches that have been found (by us and by others) to be useful in ensuring usability. We give only an overview of analytic methods, and then focus on empirical methods. We conclude with some observations on future trends in user interface evaluation.
Dense Edge-Disjoint Embedding of Complete Binary Trees in the Hypercube
Authors: Somasundaram Ravindran, A. M. Gibbons
Venue:  (1992)

We show that the complete binary tree with n < 8 leaves can be embedded in the hypercube with n nodes such that: paths of the tree are mapped onto edge-disjoint paths of the hypercube, at most two tree nodes (one of which is a leaf) are mapped onto each hypercube node, and the maximum distance from a leaf to the root of the tree is log_2 n + 1 hypercube edges (which is optimally short). This embedding facilitates efficient implementation of many P-RAM algorithms on the hypercube. keywords: parallel algorithms, graph embedding, binary tree, hypercube
*FUNL Semantics Work Towards UNCOL
Authors: R. A. Fraley
Venue:  (1977)

An intermediate semantics language, applicable to many source languages and machines, is proposed in this paper. Over its domain and range it promises many of the advantages of the original UNCOL project. Data abstraction is used to hide machine features. The language hides from the source compiler all implementation representations and conventions, except for a few descriptive constants. The semantic model is espandable by means of a library. Higher level semantic models may be implenented in FUNL, reducing compiler writing effort.
Finding and Certifying a Large Hidden Clique in a Semi-Random Graph
Authors: U. Feige, R. Krauthgamer
Venue:  (1999)

Alon, Krivelevich and Sudakov (Random Structures and Algorithms, 1998) designed an algorithm based on spectral techniques that almost surely finds a clique of size W(On) hidden in an otherwise random graph. We show that a different algorithm, based on the Lovasz theta function, almost surely both finds the hidden clique and certifies its optimality. Our algorithm has an additional advantage of being more robust: it also works in a semi-random hidden clique model, in which an adversary can remove edges from the random portion of the graph.
The Utility of Feedback in Layered Multicast Congestion Control
Authors: Sergey Gorinsky, Harrick Vin
Venue:  (2001)

Layered multicast is a common approach for dissemination of audio and video in heterogeneous network environments. Layered multicast schemes can be classified into two categories - feedback-based and feedback-free - depending on whether or not the scheme delivers feedback to the sender of the multicast session. Advocates of feedback-based schemes claim that the feedback is necessary to match the heterogeneous receiver capabilities efficiently. Supporters of feedbackfree schemes believe that feedback introduces significant complexity and that a moderate amount of additional layers can balance any benefit the feedback provides. Surprisingly, there has been no systematic evaluation of these claims. This paper compares feedback-based and feedback-free schemes quantitatively with respect to their abilities to align the provided service to the capabilities of the heterogeneous receivers. We believe that such an evaluation supplies valuable insights and guidelines to the designers of future multicast congestion control protocols.
Tool Box-Based Routines for Macintosh Timing and Display
Authors: R. Rensink
Venue:  (1989)

Pascal routines are described for performing and testing various timing and display operations on Macintosh computers. Millisecond timing of internal operations is described, as is a method to time inputs more accurately than tick timing. Techniques are also presented for placing arbitrary bit-image displays on the screen within one screen refresh. All routines are based on Toolbox procedures applicable to the entire range of Macintosh computers. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
Aspects of Parallel Image Processing Algorithms and Structures
Authors: Hans Burkhardt, Bernhard Lang, Michael Nolle
Venue:  (1990)

Most low-level algorithms are based on local dependencies. Medium and high-level algorithms, however, need global interconnections. The paper describes algorithms for image processing and pattern recognition which are well suited for implementation on parallel machines and whose topology may be described by global interconnection networks. Several aspects of interconnection networks are discussed: Reconfiguration, equivalence of different networks, granularity and principles of decomposition (base-B factorization, vector interconnections), mapping principles on smaller physical systems. Finally a parallel image processing system will be discussed which was developed at the Technical University of Hamburg. It is based on Transputers and contains two different communication structures. A high-speed parallel pipeline-bus is able to distribute the data coming from a sequentially oriented camera with flexible arbitration to the slave processors, which above that are interconnected by a reconfigurable interconnection network for the implementation of parallel algorithms.
A Temporal Logic for the Specification and Verification of Real-Time Systems
Authors: Yogesh Naik
Venue:  (1994)

In this thesis we develop a temporal logic and proof methods for the specification and verification of a real-time system which can be applied irrespective of whether time is discrete, continuous or dense. The logic is based on the definition of the next operator as the next time point a change in state occurs or if no state change occurs then it is the time point obtained by incrementing the current time by one. We show that this definition of the next operator leads to a logic which is expressive enough for specifying real-time systems where continuous time is required, and in which the verification and proof methods developed for discrete time can be used. To demonstrate the applicability of the logic several varied examples including communication protocols and digital circuits are specified and their real-time properties proved. A compositional proof system which supports hierarchical development of programs is also developed for a real-time extension of a CSP-like language. The ACM Portal is published by the Association for Computing Machinery. Copyright © 2010 ACM, Inc. Terms of Usage Privacy Policy Code of Ethics Contact Us Useful downloads: Adobe Acrobat QuickTime Windows Media Player Real Player
Developing a portal channel strategy
Authors: Jameson Watkins
Venue: Designing portals: opportunities and challenges (2003)

This chapter provides a method for organizing a portal channel development strategy by identifying potential content, classifying it and then prioritizing it into distinct categories. Several effective ways of identifying content are discussed that include committees, focus groups and pilot projects. Representatives of the campus communities that will be using the portal are important to poll, ensuring they describe their actual needs versus what they think they need. External resources aggregated into the portal must be appropriate to the institution and reliable. Channels that streamline your institution's business processes will be the most valuable parts of your portal; the bulk of your portal development work should be spent in creating them. Understanding your portal vendor's programming interfaces to create custom, integrated applications is vital, as well as their philosophy in distributing new portal channels.
Analysis of the relation between the prescriptive and descriptive approaches of the information system planning
Authors: Jorge Luis Nicolas Audy
Venue: Enterprise information systems IV (2003)

The information system planning area presents today several challenges to managers and researchers. This has happened because modern information technologies are quickly changing the way they affect and impact the company's competition. In this context, the Information Systems Strategic Planning (ISSP) becomes a critical issue on the area of information system management. For years, ISSP models have been oriented towards a prescriptive approach. New approaches for ISSP, in a descriptive line, may contribute to the search of solutions for current challenges. This article's goal is to analyze the relations between descriptive and prescriptive approaches on ISSP elaboration, looking for an explanatory model regarding the implementation of the plan created. The study is based on a qualitative research, and cases studies the main research method. As a contribution, it develops an analysis of cases studies results and presents the proposed model.
Implicit-Explicit Methods for Time-Dependent PDE''s
Authors: Uri M. Ascher, Steven J. Ruuth, Brian Wetton
Venue:  (1993)

Implicit-explicit (IMEX) schemes have been widely used, especially in conjunction with spectral methods, for the time integration of spatially discretized PDEs of diffusion-convection type. Typically, an implicit scheme is used for the diffusion term and an explicit scheme is used for the convection term. Reaction-diffusion problems can also be approximated in this manner. In this work we systematically analyze the performance of such schemes, propose improved new schemes and pay particular attention to their relative performance in the context of fast multigrid algorithms and of aliasing reduction for spectral methods. For the prototype linear advection-diffusion equation, a stability analysis for first, second, third and fourth order multistep IMEX schemes is performed. Stable schemes permitting large time steps for a wide variety of problems and yielding appropriate decay of high frequency error modes are identified. Numerical experiments demonstrate that weak decay of high frequency modes can lead to extra iterations on the finest grid when using multigrid computations with finite difference spatial discretization, and to aliasing when using spectral collocation for spatial discretization. When this behaviour occurs, use of weakly damping schemes such as the popular combination of Crank-Nicolson with second order Adams-Bashforth is discouraged and better alternatives are proposed. Our findings are demonstrated on several examples.
Multi-Resolution Surface Approximation for Animation
Authors: David Forsey, LiFeng Wang
Venue:  (1992)

This paper considers the problem of approximating a digitized surface in R3 with a hierarchical bicubic B-spline to produce a manipulatable surface for further modeling or animation. The 3D data''s original mapping from R3 (multiple rows of cylindrical scans) is mapped into the parametric domain of the B-splice (also in R3) using a modified chord-length parameterization. This mapping is used to produce a gridded sampling of the surface, and a modified full multi-grid (FMG) technique is employed to obtain a high-resolution B-spline approximation. The intermediate results of the FMG calculations generate the component overlays of a hierarchical spline surface reconstruction. Storage requirements of the hierarchical representation are reduced by eliminating offsets wherever their removal will not increase the error in the approximation by more than a given amount. The resulting hierarchical spline surface is interactively modifiable (modulo the size of the dataset and computing power) using the editing capabilities of the hierarchical surface representation allowing either local or global changes to surface shape while retaining details of the scanned data.
WHAT IS A RACE IN A PROGRAM AND WHEN CAN WE DETECT IT?
Authors: David P. Helmbold, Charles E. McDowell
Venue:  (1993)

This paper presents a taxonomy of methods for detecting race conditions in parallel programs, shows how recent results fit into the taxonomy, and presents some new results for previously unexamined points in the taxonomy. It also presents a taxonomy of ``races'''' and suggested terminology.
Software Construction Using Definitions: an Illustrative Example
Authors: W. M. Beynon
Venue:  (1989)

We present and illustrate an approach to software construction that aims to develop a program through building an explicit state-transition model of the requirement. The approach is characterised by the use of systems of definitions that admit interpretation in both conceptual and machine-oriented terms. Such definitions represent a far-reaching generalisation of spreadsheet formulae that is well-adapted for interactive and incremental modelling. The method of elaborating the model of requirements is cognitively based. It depends upon the identification of agents and their privileges for action, as specified in the definition-based notation LSD, and the simulation of agent action in appropriate contexts within the Abstract Definitive Machine. This machine model has several interesting characteristics, including the explicit modelling of data dependency and the interaction and concurrency. We illustrate our method with reference to the development of a small educational program.
High-level Synthesis of Pipelined Architectures for Multi-rate Algorithms
Authors: Sanjay R. Deshpande
Venue:  (1988)

This technical report contains an analytical framework, based on which a high-level methodology for synthesis of pipelined architectures for multi-rate algorithms may be structured. Multi-rate functions are formally defined and a need for a non-systolic design approach for efficiently implementing algorithms containing them is pointed out. The problem of designing efficient architectures for multirate algorithms is defined and a solution approach is proposed. The concept of Token Conservation Equations (TCEs), which model the average behavior of an architecture, is introduced, and it is shown how the necessary number of hardware elements can be predicted by analyzing these TCEs. The issues of sharing the physical components and buffer sizes are also discussed briefly.
Optimization as a Tool for Consistency Maintenance in Multi-resolution Simulation
Authors: Darren T. Drewry, Paul F. Reynolds, William R. Emanuel
Venue:  (2002)

The need for new approaches to the consistent simulation of related phenomena at multiple levels of resolution is great. While many fields of application would benefit from a complete and approachable solution to this problem, such solutions have proven extremely difficult. We present a multi-resolution simulation methodology that uses numerical optimization as a tool for maintaining external consistency between models of the same phenomena operating at different levels of temporal and/or spatial resolution. Our approach follows from previous work in the disparate fields of inverse modeling and spacetime constraint-based animation. As a case study, our methodology is applied to two environmental models of forest canopy processes that make overlapping predictions under unique sets of operating assumptions, and which execute at different temporal resolutions. Experimental results are presented and future directions are addressed.
Knowledge, Timed Precedence and Clocks
Authors: Y. Moses, B. Bloom
Venue:  (1995)

This paper introduces a framework for knowledge-based analysis of issues of timing and clocks in systems with real-time constraints. We define the notion of timed precedence, a generalization of Lamport''s potential causality that is suitable for reasoning about timing in real-time systems. Knowledge about timed precedence is the key element in some of the work on optimal clock synchronization. We argue that the state of distributed knowledge, the natural candidate for use in such an analysis, is not appropriate for capturing various aspects of timing in real-time systems. We define an alternative notion, called inherent knowledge, which we find more appropriate. Finally, we illustrate how knowledge about the timed precedence of events can allow high-level reasoning about issues such as clock synchronization.
Derandomized Graph Products
Authors: U. Feige, D. Zuckerman
Venue:  (1993)

Berman and Schnitger gave a randomized reduction from approximating MAX-SNP problems within constant factors arbitrarily close to 1 to approximating clique within a factor of ne (for some e). This reduction was further studied by Blum, who gave it the name randomized graph products. We show that this reduction can be made deterministic (derandomized), using random walks on expander graphs.
The Airy Tape An Early Chapter in the History of Debugging
Authors: M. Campbell-Kelly
Venue:  (1990)

This paper describes a recently-found paper tape of an undebugged program written for the EDSAC computer in 1949. It is believed that this program is the first real, ''non-trivial'' application ever written for a stored-program computer. An examination of the program sheds new light on the extent to which the debugging problem was unanticipated by early computer programmers, and the motivation for the development of systematic programming practices and debugging aids. the impact of these early developments on programming elsewhere is discussed.
Exploiting Sequential Debuggers in a Parallel Environment: An Introduction to the Mentat Assistant Debugger
Authors: A. Nguyen-Tuong, A. S. Grimshaw
Venue:  (1995)

The Mentat Assistant Debugger (MAD) is a set of tools that enables programmers to debug their Mentat applications using the debugger of their choice. MAD is easy to use and requires no modifications to existing Mentat code. MAD leverages off the existing base of sequential debuggers available in both the public domain and commercial sector and can easily accommodate future improvements in debugging technology.
Concurrent Object-Oriented Real-Time Systems Research
Authors: Dennis G. Kafura
Venue:  (1988)

This research investigates building real-time systems with a concurrent object oriented programming language. There are close parallels between the characteristics of concurrent object oriented languages and real-time systems. The language''s underlying model of concurrency reflects the distributed and concurrent nature of real-time systems while the language''s object orientation and the reusability properties of class inheritance address the embedded and evolutionary aspects of real-time systems. Automatic reclamation of concurrent objects frees programmers from the error-prone task of explicit resource management of dynamically created objects. Reclamation of concurrent objects provides an integrated management of both processing and memory resources.
Rearrangeable Circuit-Switching Networks
Authors: Nicholas Pippenger
Venue:  (1992)

We present simple proofs of the basic results concerning the complexity of rearrangeable connectors and superconcentrators. We also define several types of networks whose connectivity properties interpolate between these extremes, and show that their complexities also interpolate.