ppxscal/embedding_network huggingface dataset:
LEND and Faster Algorithms for Constructing Minimal Perfect Hash Functions
Authors: Edward A. Fox, Qi Chen, Lenwood S. Heath
Venue:  (1992)

The Large External object-oriented Network Database (LEND) system has been developed to provide efficient access to large collections of primitive or multimedia objects, semantic networks, thesauri, hypertexts, and information retrieval collections. An overview of LEND is given, emphasizing aspects that yield efficient operation. In particular, a new algorithm is described for quickly finding minimal perfect hash functions whose specification space is very close to the theoretical lower bound, i.e., around 2 bits per key. The various stages of processing are detailed, along with analytical and empirical results, including timing for a set of over 3.8 million keys that was processed on a NeXTstation in about 6 hours.
Learning and Approximation Algorithms for problems motivated by Evolutionary Trees
Authors: Mary Cryan
Venue:  (1999)

In this thesis we consider some computational problems motivated by the biological problem of reconstructing evolutionary trees. In this thesis, we are concerned with the design and analysis of efficient algorithms for clearly defined combinatorial problems motived by this application area. We present results for two different kinds of problem. Our first problem is motivated by models of evolution that describe the evolution of biological species in terms of a stochastic process that alters the DNA of species. The particular stochastic model that we considered is called the Two-State General Markov Model. In this model, an evolutionary tree can be associated with a distribution on the different ``patterns'''' that may appear among the sequences for all the species in the evolutionary tree. Then the data for a collection of species whose evolutionary tree is unknown can be viewed as samples from this (unknown) distribution. An interesting problem asks whether we can use samples from an unknown evolutionary tree M to find another tree M*for those species, so that the distribution of M* is similar to that of M. This is essentially a PAC-learning problem (``Probably Approximately Correct'''') in the sense of Valiant and Kearns et al.. Our results show that evolutionary trees in the Two-State General Markov can be efficiently PAC-learned in the variation distance metric using a ``reasonable'''' number of samples. The two other problems that we consider are combinatorial problems that are also motivated by evolutionary tree construction. The input to each of these problems consists of a fixed tree topology whose leaves are bijectively labelled by the elements of a species set, as well as data for those species. Both problems involve labelling the internal nodes in the fixed topology in order to minimize some function on that tree (both functions that we consider are assumed to test the quality of the tree topology in some way). The two problems that we consider are known to be NP-hard. Our contribution is to present efficient approximation algorithms for both problems.
Approximating the Bandwidth via Volume Respecting Embeddings (Preliminary Version 3)
Authors: U. Feige
Venue:  (1998)

A linear arrangement of an n-vertex graph is a one-to-one mapping of its vertices to the integers {1, ?, n}. The bandwidth of a linear arrangement is the maximum difference between mapped values of adjacent vertices. The problem of finding a linear arrangement with smallest possible bandwidth in NP-hard. We present a randomized algorithm that runs in nearly linear time and outputs a linear arrangement whose bandwidth is within a polylogarithmic multiplicative factor of optimal. Our algorithm is based on a new notion, called volume respecting embeddings, which is a natural extension of small distortion embeddings of Bourgain and of Linial, London and Rabinovich. 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
Free vibration of sandwich beams using the dynamic stiffness method
Authors: J. R. Banerjee
Venue: Proceedings of the eighth international conference on The application of artificial intelligence to civil and structural engineering computing (2001)

The free vibration analysis of symmetric sandwich beams is carried out in this paper by using the dynamic stiffness method. First the governing partial differential equations of motion of a three-layered symmetric sandwich beam undergoing free natural vibration are derived using Hamilton's principle. The formulation led to two partial differential equations that are both coupled in axial and bending deformations. While seeking solution for harmonic oscillation, the two equations are combined into one sixth-order ordinary differential equation, which applies to both axial and bending displacements. This procedure was facilitated by the use of symbolic computation with the package REDUCE. Closed form analytical solution of the sixth order differential equation is then obtained in its most general form in terms of six arbitrary constants. Expressions for axial force, shear force and bending moment are also obtained in terms of the six arbitrary constants. Next the boundary conditions for displacements and forces at the ends of the sandwich beam are applied to eliminate the constants. This essentially casts the equations in the form of element dynamic stiffness matrix of the sandwich beam relating harmonically varying forces with harmonically varying displacements. The resulting dynamic stiffness matrix is then applied in conjunction with the Wittrick-Williams algorithm to compute the natural frequencies and mode shapes of an example sandwich beam. Numerical results are discussed and compared with those available in the literature. This is followed by conclusions.
Software Design: The Options Approach
Authors: Kevin J. Sullivan
Venue:  (1996)

Many software engineering principles and concepts that are critical to reasoning about problems in software design (of which software architecture is an important special case) remain ad hoc, idiosyncratic and poorly integrated. I argue that this is due to our lack of a clean theory about how to make software design decisions. In this paper I propose that we should view software design as a process of deciding how to make irreversible capital investment in software assets of uncertain value, and that financial options theory provides a firm, unifying, simplifying and well developed basis for such decision-making. To support this view, I interpret software architecture and other related concepts in options theoretic terms. 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
APPROXIMATION PROPERTIES OF NP MINIMIZATION CLASSES
Authors: Phokion G. Kolaitis, Madhukar N. Thakur
Venue:  (1991)

In this paper we introduce a new approach to the logical definability of NP optimization problems by focusing on the expressibility of feasible solutions. We show that in this framework first-order sentences capture exactly all polynomially bounded optimization problems. We also show that, assuming P not= NP, it is an undecidable problem to tell if a given first-order sentence defines an approximable optimization problem. We then isolate a syntactically defined class of NP minimization problems that contains the MIN SET COVER problem and has the property that every problem in it has a logarithmic approximation algorithm. We conclude by giving a machine-independent characterization of the NP =? co-NP problem in terms of logical expressibility of the MAX CLIQUE problem.
Bandwidth Allocation with Preemption
Authors: A. Bar-Noy, R. Canetti, S. Kutten, Y. Mansour, B. Schieber
Venue:  (1995)

Bandwidth allocation is a fundamental problem in the design of networks where bandwidth has to be reserved for connections in advance. The problem is intensified when the requested bandwidth exceeds the capacity and not all requests can be served. Furthermore, acceptance/rejection decisions regarding connections have to be made on-line, without knowledge of future requests. We show that the ability to preempt (i.e., abort) connections while in service in order to be able to schedule ``more valuable'''' connections substantially improves the overall throughput of some networks. We present bandwidth allocation strategies that use preemption and show that they achieve constant competiveness with respect to the throughput, given that any single call occupies only a constant fraction of the bandwidth. Our results should be contrasted with recent works showing that nonpreemptive strategies have at most logarithmic competitiveness.
An Instantaneous Frequency-Based Computation of Transparent Motion
Authors: K. Langley, D. Fleet, T. J. Atherton
Venue:  (1991)

We extend the principle of phase-based techniques for measuring optical flow and binocular disparity to multiple motion estimation. Using quadrature filter pairs, we estimate phase gradients (instantaneous frequency) from independent bandpass channels, which we apply towards the problem of multiple optic flow analysis. Our approach is similar to that of Shizawa and Mase [23], in which nth-order differential operators are required to compute n simultaneous velocity estimates. The approach presented here is simpler, however, because we require only a set of band-pass filters, the out-puts of which need only be differentiated once. Thus, the present technique requires only first-order filters. Additionally, this theory is also applicable to transparency in stereopsis.
Free Rotation of a Circular Ring with an Unbalanced Mass
Authors: Layne T. Watson, C. Y. Wang
Venue:  (1988)

Large space structures are much more flexible than their terrestrial counterparts. Rotation of large space structures may be desirable for stability, thermal or artificial gravity reasons. Previous literature includes the large deformations due to the free rotation of a slender rod and a ring about a diameter. An important model of a space station is a ring rotating about its axis of symmetry. If the ring is balanced it will be stable and remain circular. The present note considers the case when the ring is unbalanced by a mass attached to a point on the ring.
INFERRING RECURSIVE STRUCTURES IN TYPES IN PROLOG PROGRAMS USING ABSTRACT INTERPRETATION
Authors: Fumiaki Kamiya
Venue:  (1996)

One way to prove termination of a logic program is to show that input terms passed to each recursive procedure decrease in size between successive calls to the same procedure with respect to some appropriately defined norms. Except when all the input terms are ground, finding the appropriate norms is generally not easy. Barring the use of numbers and arithmetics, recursive calls are controlled by recursively constructed terms. Thus, one way to automatically find the appropriate norms would be to automatically identify recursive structures in term types. This report describes a work in progress that attempts to infer such recursive structures using abstract interpretation.
Tracking Text in Mixed Mode Documents
Authors: J. P Bixler
Venue:  (1988)

This paper describes a method for extracting arbitrarily oriented text in documents containing both text and graphics. The technique presented is inspired by the tracking algorithms frequently found in raster to vector conversion systems. By identifying text components in the document, reducing the resolution of the image by the size of the characters, and then tracking the centers of the character components, all text strings can be removed and subsequently reoriented to the horizontal. They can then be presented for automated character recognition. A by-product of the method is that characters are automatically grouped together to form words and/or phrases. We give a detailed description of the algorithm, discuss its strengths and weaknesses, and present some sample results obtained from a typical city street map.
Notational Techniques for Accommodating User Intention Shifts
Authors: Antonio C. Siochi, H. R Hartson, Deborah Hix
Venue:  (1990)

Good user interface designs allow for user intention shifts. The asynchronous nature of direct maniulation interfaces inherently demands consideration of user intention shifts during the performance of a task. Maintaining a focus on the primary function of a task while at the same time accommodating user intention shifts is difficult for interface designers when both these aspects are represented at the same design level. The User Action Notation (UAN), a technique for representing asynchronous interfaces, contains a mechanism for specifying points in a task where user intention shifts may occur. A complementary technique, Task Transition Diagrams (TTDs), is used to specify tasks that users can perform to interrupt their current task. The Task Transition Diagram is a notation that allows a designer to map out the set of tasks and intentions of users without having to be concerned with the minutiae of how a user accomplishes those tasks.
Solving Complexity and Ambiguity Problems in Qualitative Simulation
Authors: Daniel J Clancy
Venue:  (1997)

Qualitative simulation is used to reason about the behavior of imprecisely defined dynamical systems for tasks such as monitoring, diagnosis, or design. Often, however, simulation of complex dynamical systems results in either an intractable simulation or an ambiguous behavioral description. These results have caused concern regarding the scalability of techniques based upon qualitative simulation to real--world problems. Two different approaches are used to solve these problems: 1) abstraction and problem decomposition techniques are used during simulation to focus on relevant distinctions thus reducing the overall complexity of the simulation; and 2) the expressiveness of the modeling language is extended to allow the modeler to incorporate additional information. Model decomposition and simulation (DecSIM) uses a component--based simulation algorithm to reason about the complex interactions within a sub--system independent of the interactions between subsystems. Variables within the model are partitioned into closely related components and a separate behavioral description is generated for each component. Links are maintained between related components to ensure that all of the constraints in the model are satisfied. DecSIM results in exponential speed--up for models that lend themselves to decomposition. Furthermore, DecSIM is guaranteed to generate a behavioral description that is equivalent to the description generated by a standard QSIM simulation modulo the temporal ordering of events for variables in separate components. A common source of irrelevant distinctions within qualitative simulation is intractable branching due to chatter. Chatter occurs when the derivative of a variable is constrained only by continuity within a restricted region of the state space. We present two different abstraction techniques that completely eliminate the problem of chatter by abstracting a chattering region into a single abstract state. Both techniques retain the QSIM soundness guarantee and eliminate all instances of chatter without over--abstracting. To address the problem of an ambiguous behavioral description, Temporally Constrained QSIM (TeQSIM) integrates temporal logic model checking into the qualitative simulation process allowing the modeler to specify behavioral information via trajectory constraints. Trajectory constraints, specified using an extension of a propositional linear--time temporal logic, can be used to focus the simulation, simulate non--autonomous systems and reason about boundary condition problems.
Object Identity in Omega: an Object-oriented Database System For ManagingMultimedia Data
Authors: Yoshifumi Masunaga
Venue:  (1988)

OMEGA is a database system for managing multimedia data under development at the University of Library and Information Science. It takes an object-oriented approach, and its data model is called OMEGA. In order to make the object concept and basic object management scheme in OMEGA clear, we focused our investigation on the object identity and related topics. In this paper, it is revealed that three types of object identity exist in OMEGA; the trivial identity, the referential identity, and the arbitrary identity. Based on this result, various types of object identity which exist in the real world are characterized in OMEGA. The contents identity, the identity of complex objects, and the object similarity are such examples. Because object identity and similarity satisfy the condition of the equivalence relation on a set, the quotient class can be defined. By using this, other types of object identity such as the substantial identity and the relational identity are characterized. Moreover the object copy, the object naming, and the comparison between single class and multiclass object management schemes are investigated in this paper.
Correctness Proofs of Programs using Weak Memories
Authors: Manhoi Choy, Ambuj K. Singh
Venue:  (1993)

A method for reasoning with non-atomic memory is developed. A program using non-atomic memory is transformed into an equivalent one that uses atomic memory. A number of non-atomic memories including pipelined RAM, causal memory, and hybrid consistency are examined. The approach is illustrated with some examples.
Contention Resolution with Constant Expected Delay
Authors: L. A. Goldberg, P. D. MacKenzie, M. Paterson
Venue:  (1998)

We study contention resolution in a multiple-access channel such as the Ethernet channel. In the model that we consider, n users generate messages for the channel according to a probability distribution. Raghavan and Upfal have given a protocol in which the expected "delay" (time to get serviced) of every message is O(log n) when messages are generated according to a Bernoulli distribution with generation rate up to about 1/10. We present a protocol in which the expected average message delay is O(1) when messages are generated according to a Bernoulli distribution with a generation rate smaller than 1/e. To achieve this result we first consider an analogous model in which users are synchronized (i.e., they agree about the time), there are potentially an infinite number of users, and messages are generated according to a Poisson distribution with generation rate up to 1/e. (Each message constitutes a new user.) We give a protocol in which the expected delay of any message is O(1). Next we show how to simulate the protocol using n synchronized users. Finally, we show how to build the synchronization into the protocol.
Testing the Isotach Prototype Hardware Switch Interface Unit
Authors: Doug Szadja
Venue:  (1999)

Although Isotach systems can be implemented entirely in software using commercial off-the-shelf hardware, they achieve greatest efficiency with the help of special hardware components, one of which is the switch interface unit (SIU). Located in-link between the network interface boards and switches to which these boards are connected, the SIU is responsible for the maintenance of logical time, for timestamping outgoing isotach messages, and for exchanging tokens with another custom hardware device, the token manager (TM). Testing the SIU requires the modification of the isotach prototype code base to create two new system versions, Version 1.75 which emulates the functionality of the SIU and is intended to run in systems in which other nodes are connected to hardware SIUs, and Version 2 which runs on hosts connected directly hardware SIUs. In addition to these prototypes, a suite of test programs has been designed to aid in lower level debugging of the device, and to verify that design requirements have been met. This technical report describes the development of these prototype versions, the current state of the SIU debugging process, and the design of the test suite. In addition, detailed prototype code documentation and hints for programming the LANai (the Myrinet network interface processor) are included in the appendices. 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
A functional size measurement method for event-based object-oriented enterprise models
Authors: Geert Poels
Venue: Enterprise information systems IV (2003)

The effective management of IS-related processes requires measuring the functional size of information systems. Functional size measurement is usually performed using the Function Points Analysis method. Earlier attempts to apply Function Point counting rules to object-oriented systems met with serious problems because the implicit model of functional user requirements in Function Points Analysis is hard to reconcile with the object-oriented paradigm. The emergence of a new generation of functional size measurement methods has changed this picture. The main implementation of this generation, COSMIC Full Function Points, explicitly defines a generic model of functional user requirements onto which artifacts belonging to any IS specification or engineering methodology can be mapped. In this paper we present specific COSMIC-FFP mapping rules for methodologies that take an event-based approach to information system engineering. In particular we show that the event-oriented nature of the COSMIC-FFP measurement rules provides for a natural mapping of concepts. To illustrate the mapping rules we use MERODE, a formal event-based object-oriented methodology for systems development in information processing intensive domains. The mapping rules presented are confined to the enterprise layer in a MERODE IS architecture.
Randomized Hough Transform: Improved Ellipse Detection with Comparison
Authors: Robert A McLaughlin
Venue:  (1997)

We describe an algorithm for the detection of ellipse shapes in images, using the Randomized Hough Transform. The method is compared with three other Hough-based algorithms. Tests are performed using both noise-free and noisy images, and several real-world images. The algorithm was found to give improvements in accuracy, and a reduction in computation time and the number of false alarms detected. A program allowing the reader to experiment with these algorithms can be found at the WWW address http://ciips.ee.uwa.edu.au/Papers/Journal_Papers/1997/01/Index.html
A UNIX Micro Requirement for Computer Science Majors
Authors: Edward A. Fox, Sandra E. Birch
Venue:  (1986)

In the fall of 1985, over 230 freshmen majoring in computer science at Virginia Tech purchased microcomputers running the UNIX operating system, because of a vote in spring 1983 by the faculty of the Department of Computer Science to institute a requirement of personal computers. This paper reviews the planning and decision-making process, and explains why UNIX was chosen as the most suitable system to use in the training of computer science students. Implementation of the microcomputer program is discussed, including revisions to the freshman curriculum and the distribution of required hardware and software.