ppxscal/embedding_network huggingface dataset:
Lambertian Reflectance and Linear Subspaces
Authors: R. Basri, D. Jacobs
Venue:  (2000)

We prove that the set of all reflectance functions (the mapping from surface normals to intensities) produced by Lambertian objects under distant, isotropic lighting lies close to a 9D linear subspace. This implies that, in general, the set of images of a convex Lambertian object obtained under a wide variety of lighting conditions can be approximated accurately by a low-dimensional linear subspace, explaining prior empirical results. We also provide a simple analytic characterization of this linear space. We obtain these results by representing lighting using spherical harmonics and describing the effects of Lambertian materials as the analog of a convolution. These results allow us to construct algorithms for object recognition based on linear methods as well as algorithms that use convex optimization to enforce non-negative lighting functions. Finally, we show a simple way to enforce non-negative lighting when the images of an object lie near a 4D linear space.
Two Problems of TCP AIMD Congestion Control
Authors: Y. R Yang, Min S Kim, Xincheng Zhang, Simon S. Lam
Venue:  (2000)

AIMD (additive increase and multiplicative decrease) algorithm has been used in many congestion control protocols, including TCP in the Internet. In this paper, we compared AIMD and MAIMD (multiplicative additive increase and multiplicative decrease). We found that the convergence speeds to fair states of AIMD and MAIMD are close to each other. However, we observe that MAIMD has some advantages. For example, its speed to use network available bandwidth can be much faster than AIMD. We also investigated AIMD behaviors under a more realistic aynchronous system model. We found that under this model, AIMD system can have more than one attrators, and therefore can be another contributor to the fairness problem of TCP.
Ensuring integrity and service availability in a web-based control laboratory
Authors: Sung-Soo Lim, Kihwal Lee, Lui Sha
Venue: Real-time system security (2003)

The new millennium heralds the convergence of communication, computing and the intelligent control of the physical environment. However, as embedded devices being networked and becoming more accessible, the threat of security breaches also becomes increasingly serious. This paper focuses on how to ensure the integrity of the system, when mobile codes could contain not only bugs but also viruses.
On the Complexity of String Folding
Authors: M. S. Paterson, T. Przytycka
Venue:  (1995)

A fold of a finite string S over a given alphabet is an embedding of S in some fixed infinite grid, such as the square or cubic mesh. The score of a fold is the number of pairs of matching string symbols which are embedded at adjacent grid vertices. Folds of strings and sets of strings in two- and three-dimensional meshes are considered, and the corresponding problems of optimizing the score or achieving a given target score are shown to be NP-hard.
Efficient Matrix Inversion via Gauss-Jordan Elimination and ItsParallelization
Authors: Enrique S. Quintana, Gregorio Quintana, Xiaobai Sun, Robert van de Geijn
Venue:  (1998)

We present a new parallel matrix inversion algorithm and report its implementation on parallel computers with distributed memory. The algorithm features natural load balance, simple programming and easy performance optimization, while maintaining the same arithmetic cost and numerical properties of the conventional inversion algorithm. Our analysis and experiments on a Cray T3E report near-peak performance for the new approach.
Reproducing Kernels and Riccati Equations,
Authors: H. Dym
Venue:  (2001)

The purpose of this paper is to exhibit a connection between the Hermitian solutions of matrix Riccati equations and a class of finite dimensional reproducing kernel Krein spaces. This connection is then exploited to obtain minimal factorizations of rational matrix valued functions that are J-unitary on the imaginary axis in a natural way. 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
Parallelizing Multidimensional Index Structures
Authors: K V R Kanth, Agrawal,  D, A E Abbadi, Singh,  A, Smith,  T
Venue:  (1996)

Indexing multidimensional data is inherently complex leading to slow query processing. This behavior becomes more pronounced with the increase in database size and/or number of dimensions. In this paper, we address this issue by processing an index structure in parallel. First, we study different ways of partitioning an index structure. We then propose efficient algorithms for processing each query in parallel on the index structure. Using these strategies, we parallelized two multidimensional index structures -- R* and LIB and evaluated the performance gains for the Gazetteer and the Catalog data of the Alexandria Digital Library on the Meiko CS-2.
PIN ASSIGNMENT AND ROUTING ON A SINGLE-LAYER PIN GRID ARRAY
Authors: Man Yu, Wayne W Dai
Venue:  (1995)

This paper look at the problem of assigning pins and generating a planar topological routing for a pin grid array package. There is a freedom of assigning any pin to any pad but the routing resource is more limited. We showed that a monotonic pin assignment has no detours and has one and only one monotonic topological routing. We proposed an algorithm (EVENPGA) that generates this type of topological routing. In addition, EVENPGA creates the optimal uniform distribution of wires and shortest wire length possible for all wires under the taxicab wiring metric. If the topological routing is routable, the maximum density of critical cuts along a ring is the minimum theoretically possible. Once the topological routing is done, physical layout can easily be obtained using Surf, a rubberband-based routing system.
Statistical Multiplexing Gain of Link Scheduling Algorithms in QoS Networks (Short Version)
Authors: Boorstyn Robert, Burchard Almut, Liebeherr Jorg, Oottamakorn Chaiwat
Venue:  (1999)

This report is an abbreviated version of CS-99-21. A statistical network service which allows a certain fraction of traffic to not meet its QoS guarantees can extract additional capacity from a network by exploiting statistical properties of traffic. Here we consider a statistical service which assumes statistical independence of flows, but does not make any assumptions on the statistics of traffic sources, other than that they are regulated, e.g., by a leaky bucket. Under these conditions, we present functions, so-called local effective envelopes and global effective envelopes, which are, with high certainty, upper bounds of multiplexed traffic. We show that these envelopes can be used to obtain bounds on the amount of traffic on a link that can be provisioned with statistical QoS. A key advantage of our bounds is that they can be applied with a variety of scheduling algorithms. In fact, we show that one can reuse existing admission control functions that are available for scheduling algorithms with a deterministic service. We present numerical examples which compare the number of flows with statistical QoS guarantees that can be admitted with our empirical envelope approach to those achieved with existing methods.
A COHERENT PROJECTION APPROACH FOR DIRECT VOLUME RENDERING
Authors: Jane Wilhelms
Venue:  (1990)

Direct volume rendering using semi-transparency offers the opportunity to visualize all of a three-dimensional sample volume in one image. However, because all cells may contribute something to the image, processing such images can be very expensive and good quality high-resolution images are far from interactive. This paper introduces a projection approach for directly rendering sample volumes that takes advantage of coherence combined with the polygon rendering facilities of the newer graphics machines to produce images (relatively) quickly. It projects each volume cell as one to seven polygons, calculates color and opacity for each vertex, and interpolates across the polygons to render the cell. In its fastest form, the interpolation is linear in color and opacity and amounts to Gouraud shaded polygon scan conversion. It is limited to rectilinear sample volumes rendered without perspective.
An Analysis of Processor Resource Models for Use in Performance Prediction
Authors: E. Papaefstathiou, Darren J. Kerbyson, Graham R. Nudd, T. J. Atherton
Venue:  (1994)

With the increasing sophistication of both software and hardware systems, methodologies to analyse and predict system performance is a topic of vital interest. This is particularly true for parallel systems where there is currently a wide choice of both architectural and parallelisation options; and where the costs are likely to be high. Performance data is vital to a diffuse range of users including; system developers, application programmers and tuning experts. However, the level of sophistication and accuracy required by each of these users is substantially different. In this paper characterisation based technique is described (considering both application and hardware resources) which addresses these issues directly. Initially, a framework is described for characterisation based approaches. A classification scheme is used to illustrate differences in the level of sophistication and detail in which the underlying resource models are specified. Finally, verification is provided of the characterisation techniques applied to several application kernels on a MIMD system. The performance predictions and error bounds resulting from the level of resource specification are also discussed.
The pitfalls of knowledge discovery in databases and data mining
Authors: John Wang, Alan Oppenheim
Venue: Data mining: opportunities and challenges (2003)

Although Data Mining (DM) may often seem a highly effective tool for companies to be using in their business endeavors, there are a number of pitfalls and/or barriers that may impede these firms from properly budgeting for DM projects in the short term. This chapter indicates that the pitfalls of DM can be categorized into several distinct categories. We explore the issues of accessibility and usability, affordability and efficiency, scalability and adaptability, systematic patterns vs. sample-specific patterns, explanatory factors vs. random variables, segmentation vs. sampling, accuracy and cohesiveness, and standardization and verification. Finally, we present the technical challenges regarding the pitfalls of DM.
The Logic of Depiction
Authors: Raymond Reiter, Alan K. Mackworth
Venue:  (1987)

We propose a theory of depiction and interpretation that formalizes image domain knowledge, scene domain knowledge and the depiction mapping between the image and scene domains. This theory is illustrated by specifying some general knowledge about maps, geographic objects and their depiction relationships in first order logic with equality. An interpretation of an image is defined to be a logical model of the general knowledge and a description of that image. For the simple map world we show how the task level specification may be refined to a provably correct implementation by invoking model preserving transformations on the logical representation. In addition, we sketch logical treatments for querying an image, incorporating contingent scene knowledge into the interpretation process, occlusion, ambiguous image descriptions, and composition. This approach provides a formal framework for analyzing existing systems such as Mapsee, and for understanding the use of constraint satisfaction techniques. It also can be used to design and implement vision and graphics systems that are correct with respect to the task and algorithm levels.
SATISFIABILITY TESTING WITH MORE REASONING AND LESS GUESSING
Authors: Allen VanGelder, Yumi K. Tsuji
Venue:  (1995)

A new algorithm for testing satisfiability of propositional formulas in conjunctive normal form (CNF) is described. It applies reasoning in the form of certain resolution operations, and identification of equivalent literals. Resolution produces growth in the size of the formula, but within a global quadratic bound; most previous methods avoid operations that produce any growth, and generally do not identify equivalent literals. Computational experience indicates that the method does substantially less ``guessing'''' than previously reported algorithms, while keeping a polynomial time bound on the work done between guesses. Experiments indicate that, for larger problems, the time investment in reasoning returns a profit in reduced searching, and the profit increases with increasing problem size. Experimental data compares six branching strategies of the proposed algorithm on a variety of problems, including several Dimacs benchmarks. These branching strategies were shown to perform differently with statistical significance. A new scheme based on Johnson''s maximum satisfiability approximation algorithm was found to be the best overall. Both satisfiable and unsatisfiable random 3-CNF formulas with 50--283 variables and 4.27 ratio of clauses to variables have been tested; this class is generally acknowledged to be relatively ``hard'''' and required extensive backtracking by other algorithms. Unsatisfiable random problems were found to deviate from the easy-hard-easy pattern. The new algorithm solves random formulas with surprisingly little backtracking: the average number of guesses was 3,267 for 200 variables at this ratio, and 57,503 for 283 variables. Larger unsatisfiable formulas from circuit-fault analysis, with 500--12,800 variables were solved with no backtracking in some cases. Extensive statistics on guesses and time are reported. Statistical and experimental techniques and traps are discussed. An exponential growth rate for random formulas is estimated.
F&#x00F6;derierte Transaktionsverwaltung
Authors: Thomas Lehnecke
Venue:  (1996)

Eine vergleichende Betrachtung aktueller Entwicklungen 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
Starshaped Sets, The Radial Function and 3-D Attitude Determination
Authors: Ying Li, Robert J. Woodham
Venue:  (1992)

Attitude characterizes the three rotational degrees of freedom between the coordinate system of a known object and that of a viewer. Orientation-based representations record 3-D surface properties as a function of position on the unit sphere. The domain of the representation is the entire sphere. Imaging from a single viewpoint typically determines a hemisphere of the representation. Matching the visible region to the full spherical model for a known object estimates 3-D attitude. The radial function is used to define a new orientation-based representation of shape. The radial function is well-defined for a class of sets called {\em starshaped} in mathematics. A starshaped set contains at least one interior point from which all boundary points are visible. The radial function records the distance from the origin of the coordinate system to each boundary point. The novel contribution of this paper is to extend previous mathematical results on the matching problem for convex objects to starshaped objects. These results then allow one to transform the attitude determination problem for starshaped sets into an optimization problem for which standard numerical solutions exist. Numerical optimization determines the 3-D rotation that brings a sensed surface into correspondence with a known model. The required surface data can be obtained, for example, from laser range finding or from shape-from-shading. A proof-of-concept system has been implemented and experiments conducted on real objects using surface data derived from photometric stereo.
Comparison of a Graphical and a Textual Design Language Using Software Quality Metrics
Authors: Sallie M. Henry, Roger Goff
Venue:  (1988)

For many years the software engineering community has been attacking the software reliability problem on two fronts. First via design methodologies, languages and tools as a precheck on quality and second by measuring the quality of produced software as a postcheck. This research attempts to unify the approach to creating reliable software by providing the ability to measure the quality of a design prior to its implementation. A comparison of a graphical and a textual design language is presented in an effort to support research findings that the human brain works more effectively in images than in text.
Automatic Rectification of Landsat Durages Using Features Derived from Digital Terrain Models
Authors: James J Little
Venue:  (1980)

Before two images of the same object can be compared, they must be brought into correspondence with some reference datum. This process is termed registration. The reference can be one of the images, a synthetic image, a map or other symbolic representation of the area imaged. A novel method is presented for automatically determining the transformation to align a Landsat image to a digital terrain model, a structure which represents the topography of an area. Parameters of an affine transformation are computed from the correspondence between features of terrain derived from the digital terrain model, and brightness discontinuities extracted from the Landsat image.
SWIFT: USING DISTRIBUTED DISK STRIPING TO PROVIDE HIGH I/O DATA RATES
Authors: Luis Cabrera, Darrell D.E. Long
Venue:  (1991)

We present an I/O architecture, called Swift, that addresses the problem of data rate mismatches between the requirements of an application, storage devices, and the interconnection medium. The goal of Swift is to support high data rates in general purpose distributed systems. Swift uses a high-speed interconnection medium to provide high data rate transfers by using multiple slower storage devices in parallel. It scales well when using multiple storage devices and interconnections, and can use any appropriate storage technology, including high-performance devices such as disk arrays. To address the problem of partial failures, Swift stores data redundantly. Using the UNIX operating system, we have constructed a simplified prototype of the Swift architecture. The prototype provides data rates that are significantly faster than access to the local SCSI disk, limited by the capacity of a single Ethernet segment, or in the case of multiple Ethernet segments by the ability of the client to drive them. We have constructed a simulation model to demonstrate how the Swift architecture can exploit advances in processor, communication and storage technology. We consider the effects of processor speed, interconnection capacity, and multiple storage agents on the utilization of the components and the data rate of the system. We show that the data rates scale well in the number of storage devices, and that by replacing the most highly stressed components by more powerful ones the data rates of the entire system increase significantly.
An Approximation Algorithm for Minimum-Cost Network Design
Authors: Y. Mansour, D. Peleg
Venue:  (1994)

This paper considers the problem of designing a minimum cost network meeting a given set of traffic requirements between n sites, using one type of channels of a given capacity, with varying set-up costs for different vertex pairs (comprised of a fixed part plus a part dependent on the pair). An approximation algorithm is proposed for this problem, which guaranteed a solution whose cost is greater than the optimum by a factor of at most log n (and constant in the planar case). The algorithm is based on an application of the recent construction of light-weight distance-preserving spanners.
SCENT: A Method Employing Scenarios to Systematically Derive TestCases for System Test
Authors: Johannes RYSER, Martin GLINZ
Venue:  (2000)

Scenarios/Use cases have attracted much attention and gained wide- spread use in requirements and software engineering over the last couple of years. In scenarios, the functionality and behavior of a (software) system is captured in a user-centered perspective. To date, scenarios are mainly used in the requirements elicitation and analysis phase of software development. However, the use of scenarios in other phases of software development is of much interest, as it could help to cut cost by reuse and improved validation and verification. As scenarios form a kind of abstract test cases for the system under development, the idea to use them to derive test cases for system test is quite intriguing. Yet in practice, scenarios from the analysis phase are seldom used to create concrete system test cases. In this report, we present a procedure to create scenarios during the analysis phase of system development, to structure them according to a given scenario template, and to use these scenarios in the system testing phase to systematically determine test cases. This is done by formalization of natural language scenarios in statecharts, annotation of statecharts with helpful information for test case creation/generation and by path traversal in the statecharts to determine concrete test cases. Furthermore, dependencies between scenarios are captured and modeled in so-called dependency charts, and test cases are derived from dependency charts to enhance the developed test suites. The approach has been applied to two projects in industry. In this report, we also report on some of the experiences made in applying the approach in practice.
An Algorithmic Solution to the Minimax Resource Allocation Problemwith Multimodal Functions
Authors: Aida Dharmakadar, Emile K. Haddad
Venue:  (1993)

The problem of allocation is one of the most widely investigated topics in the area of mathematical optimization because of its broad applicability to different classes of real world problems. The basic idea is that, given some type of resource whose total amount is N, we want to partition and allocate the total resource over n activities to minimize some objective function, F, whose value represents the "cost" of the allocation. As can be seen from various research results in this area, the procedures to solve discrete and continuous resource allocation problems can be significantly different. One obvious basic difference is that the discrete problem can be exactly solved by exhaustive enumeration, while the continuous problem cannot.
Effect of Higher Priority EF Traffic and TCP Throughput and Fairness
Authors: Jasleen Kaur, Harrick M. Vin
Venue:  (2001)

In this paper, we study the effect on TCP of assigning higher-priority to traffice requesting Expedited Forwarding (EF) service in a Differentiated Services network. We analyze networks in which (1) EF traffice occupies different fractions of link bandwidth and is bursty at different time-scales; and (2) multiple TCP flows with heterogeneous round trip times share the network with the EF traffic. We find that even in the presence of bursty EF traffic, statistical multiplexing gains allow TCP to utilize most of the available bandwidth. Further, the presence of bursty EF traffic improves the fairness of bandwidth allocation among TCP flows; smaller more frequent bursts yield larger improvements in TCP fairness.