ppxscal/embedding_network huggingface dataset:
High-Accuracy Finite-Difference Schemes for Linear Wave Propagation
Authors: David W. Zingg, Harvard Lomax, Henry Jurgens
Venue: SIAM Journal on Scientific Computing (1996)

Two high-accuracy finite-difference schemes for simulating long-range linear wave propagation are presented: a maximum-order scheme and an optimized scheme. The schemes combine a seven-point spatial operator and an explicit six-stage low-storage time-march method of Runge--Kutta type. The maximum-order scheme can accurately simulate the propagation of waves over distances greater than five hundred wavelengths with a grid resolution of less than twenty points per wavelength. The optimized scheme is found by minimizing the maximum phase and amplitude errors for waves which are resolved with at least ten points per wavelength, based on Fourier error analysis. It is intended for simulations in which waves travel under three hundred wavelengths. For such cases, good accuracy is obtained with roughly ten points per wavelength.
Flexibility and control for dynamic workflows in the WORLDS environment
Authors: Douglas P. Bogia, Simon M. Kaplan
Venue: Proceedings of conference on Organizational computing systems (1995)

This paper presents a model and prototype implementation, called obligations, for handling flexible, dynamic changes to workflows. The model uses multiple inheritance and an overhead transparency metaphor to construct a network of activities. Each 'sheet' holds portions of the network to be constructed. Some of these sheets contain local modifications that are not shared among other similar activities and others hold general specifications that all instances should follow, assuming that they have not been locally modified. When all the sheets are stacked together, they create a composite view of the network. Individual sheets can be removed and replaced with newer, presumably compatible, sheets that change the network. This type of replacement can be encoded into surrogates which automatically carry out the replacements to keep the obligation up-to-date. The obligation system has a built in error detection scheme that determines if network construction is invalid and, if so, disallows execution of the portions of the network that are in error.
Using simulation to aid in the design of an intelligent tutoring systems
Authors: Pauline K. Cushman, Rammohan K. Ragade
Venue: ACM SIGSIM Simulation Digest (1995)

The design of instructional materials, especially Intelligent Tutoring Systems, is difficult, often because of student differences. Both the time students take to complete such tutorials, and their resulting scores, are dependent upon the length and difficulty level of the material, as well as the expertise of the student. This paper presents a first attempt to utilize the simulation of the student to help in the design of an Intelligent Tutoring System using an object-oriented approach. Simulated students respond to simulated tutorials through simulated interfaces. The object-oriented approach provides an easily adaptable framework for using the results, both in time and student scores, to aid the educator in making difficult design decisions. Statistics from successful simulation runs are presented, along with plans for future study.
Singular Optimal Stochastic Controls II: Dynamic Programming
Authors: Ulrich G. Haussmann, Wulin Suo
Venue: SIAM Journal on Control and Optimization (1995)

The dynamic programming principle for a multidimensional singular stochastic control problem is established in this paper. When assuming Lipschitz continuity on the data, it is shown that the value function is continuous and is the unique viscosity solution of the corresponding Hamilton--Jacobi--Bellman equation.
Refinement and extension of encrypted key exchange
Authors: Michael Steiner, Gene Tsudik, Michael Waidner
Venue: ACM SIGOPS Operating Systems Review (1995)

In their recent paper, "Encrypted Key Exchange: Password-based Protocols Secure Against Dictionary Attacks," Bellovin and Merritt propose a novel and elegant method for safeguarding weak passwords. This paper discusses a possible weakness in the proposed protocol, develops some enhancements and simplifications, and provides a security analysis of the resultant minimal EKE protocol. In addition, the basic 2-party EKE model is extended to the 3-party setting; this yields a protocol with some interesting properties. Most importantly, this paper illustrates, once again, the subtlety associated with designing password-based protocols.
RCBR: a simple and efficient service for multiple time-scale traffic
Authors: M. Grossglauser, S. Keshav, D. Tse
Venue: Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication (1995)

Compressed video traffic is expected to be a significant component of the traffic mix in integrated services networks. This traffic is hard to manage, since it has strict delay and loss requirements, but at the same time, exhibits burstiness at multiple time-scales. In this paper, we observe that slow time-scale variations can cause sustained peaks in the source rate, substantially degrading performance. We use large deviation theory to study this problem and to motivate the design of Renegotiated Constant Bit Rate Service (RCBR), that adds renegotiation and buffer monitoring to traditional CBR service. We argue the the load placed on signalling by RCBR can be handled by current technology. We present a) an algorithm to compute the optimal renegotiation schedule for stored (off-line) traffic, and b) a heuristic to approximate the optimal schedule for online traffic. Simulation experiments show that RCBR is able to extract almost all of the statistical multiplexing gain available by exploiting slow time-scale variations in traffic. In more general terms, we believe that a clean system design must match control time-scales to the time scales over which the workload varies. RCBR works well because it makes intelligent use of this time-scale separation.
Using predictive prefetching to improve World Wide Web latency
Authors: Venkata N. Padmanabhan, Jeffrey C. Mogul
Venue: ACM SIGCOMM Computer Communication Review (1996)

The long-term success of the World Wide Web depends on fast response time. People use the Web to access information from remote sites, but do not like to wait long for their results. The latency of retrieving a Web document depends on several factors such as the network bandwidth, propagation time and the speed of the server and client computers. Although several proposals have been made for reducing this latency, it is difficult to push it to the point where it becomes insignificant.This motivates our work, where we investigate a scheme for reducing the latency perceived by users by predicting and prefetching files that are likely to be requested soon, while the user is browsing through the currently displayed page. In our scheme the server, which gets to see requests from several clients, makes predictions while individual clients initiate prefetching. We evaluate our scheme based on trace-driven simulations of prefetching over both high-bandwidth and low-bandwidth links. Our results indicate that prefetching is quite beneficial in both cases, resulting in a significant reduction in the average access time at the cost of an increase in network traffic by a similar fraction. We expect prefetching to be particularly profitable over non-shared (dialup) links and high-bandwidth, high-latency (satellite) links.
Information finding in a digital library: the Stanford perspective
Authors: Tak W. Yan, Héctor García-Molina
Venue: ACM SIGMOD Record (1995)

In a digital library one of the most challenging problems is finding relevant information. Information finding is the research focus of the Stanford component of the ARPA-sponsored CS-TR Project, and the work has continued as one of the main thrusts in the Stanford Integrated Digital Library project [14]. In this paper we discuss some of the emerging issues in information finding, such as text-database discovery, efficient information dissemination, and copy detection and removal. We also outline our approaches to these issues.
A high fidelity ATM traffic and network simulator
Authors: Brian W. Unger, Fabian Gomes, Xiao Zhonge, Pawel Gburzynski, Theodore Ono-Tesfaye, Srinivasan Ramaswamy, Carey Williamson, Alan Covington
Venue: Proceedings of the 27th conference on Winter simulation (1995)

The design of an ATM traffic and network (ATM-TN) simulator which characterizes cell level network behavior is presented. The simulator incorporates three classes of ATM traffic source models: an aggregate ethernet model, an MPEG model and a World Wide Webb transactions model. Six classes of ATM switch architectures are modeled including output buffered, shared memory buffered and cross bar switch models, and then multistage switches which can be built from these three basic models. The ATM-TN simulator can be used to characterize arbitrary ATM networks with dynamic multimedia traffic loads. Call set up and tear down via ATM signaling is implemented in addition to the various types of cell traffic streams generated by voice, video and data. The simulator is built on a simple, efficient simulation language called SimKit which is capable of supporting both fast sequential and parallel execution. Parallel execution is supported using WarpKit, an optimistically synchronized kernel that is aimed at shared memory multiprocessor platforms such as the Silicon Graphics Powerchallenge and Sun Spare 1000 series machines. The paper outlines general requirements for ATM traffic and network simulation, presents an ATM-TN simulator architecture, describes its major components and discusses the major issues associated with cell level ATM modeling and simulation.
Order-of-magnitude advantage on TPC-C through massive parallelism
Authors: Charles Levine
Venue: Proceedings of the 1995 ACM SIGMOD international conference on Management of data (1995)

TPC Benchmark trade; C (TPC-C) is the modern standard for measuring OLTP performance. Running TPC-C, Tandem demonstrated a massively parallel configuration of 112 CPUs which achieved ten times higher performance than any other system previously measured (and today is still better by a factor of five). This result qualifies as the largest industry-standard benchmark ever run.This paper briefly describes how the benchmark was configured and the results which were obtained.
The ethical and legal quandary of email privacy
Authors: Janice C. Sipior, Burke T. Ward
Venue: Communications of the ACM (1995)

What should conscientious employees and their ethical employers expect? It's hard to say.
Input modeling when simple models fail
Authors: Barry L. Nelson, Marne C. Cario, Chester A. Harris, Stephanie A. Jamison, J. O. Miller, James Steinbugl, Jaehwan Yang, Peter Ware
Venue: Proceedings of the 27th conference on Winter simulation (1995)

A simulation model is composed of inputs and logic; the inputs represent the uncertainty or randomness in the system, while the logic determines how the system reacts to the uncertain elements. Simple input models, consisting of independent and identically distributed sequences of random variates from standard probability distributions, are included in every commercial simulation language. Software to fit these distributions to data is also available. In this tutorial we describe input models that are useful when simple models are not.
An approach to 3D pose determination
Authors: Norberto Ezquerra, Rakesh Mullick
Venue: ACM Transactions on Graphics (TOG) (1996)

The orientation, or pose, of an object is a fundamental property that helps to define the geometrical relationship between the object and its environment. In addition, knowledge of object orientation can also facilitate interpretive and decision-making tasks in a variety of practical domains, including industrial, meteorological, and medical applications. Determining object pose, however, remains an open research question in the fields of graphics and visualization. This article describes a novel yet intuitively simple approach, which we call topological goniometry, to directly determine the pose of a three-dimensional object from 3D data. The topology of interest is that of two-sided surfaces in a three-manifold, and includes objects whose shaped are unaffected by elastic transformations. Algorithmically, topological goniometry is composed of the following major steps. The first analyzes the global topology in order to generate a distribution of 3D coordinate triplets in the proximity of the desired pose axis. Using this set of 3D points, that second step then invokes a &ldquo;3D Walk&rdquo; algorithm that considers the local topology to produce a generalized curve representing an estimate of the object's axis of pose. The resultant pose axis is thus not constrained to lie along a straight line but can be generalized 3D curve. The methods are illustrated with a variety of synthetically created models that exhibit duct-like shapes, and are further tested by introducting noise as well as deformations to these models. The approach is also applied to a number of real discrete data obtained from meteorological and medical domains. The results suggest that the appproach is applicable to both real and synthetic datasets and is shown to be robust, computationally efficient, and applicable to a variety of problems. The approach can incorporate context- or application-dependent information about the object of interest by using a set of constraints that guide the process of orientation determination. This article describes the approach, its implementation, and the results obtained with numerous applications.
A simple naturalistic hair model
Authors: John Rankin, Richard Hall
Venue: ACM SIGGRAPH Computer Graphics (1996)

We propose a new computer graphics model to render naturalistic human hair. In this model, a simplified progressive polyline simulation was used for fast processing. The problems of inter-hair collisions and hair-head collisions were avoided by certain assumptions, and the bend in the hair was provided by angle-dependent pseudo-force equations. Several hair-colour and shadowing techniques were tested. Despite the simplicity of the hair model itself, when it was combined with the coloring and shadowing techniques described here, the proposed model did effectively render hair, as illustrated by the still images.
Explaining the gap between theoretical peak performance and real performance for supercomputer architectures
Authors: W. Schönauer, H. Häfner
Venue: Scientific Programming (1994)

The basic architectures of vector and parallel computers and their properties are presented followed by a discussion of memory size and arithmetic operations in the context of memory bandwidth. For a single operation micromeasurements of the vector triad for the IBM 3090 VF and the CRAY Y-MP/8 are presented, revealing in detail the losses for this operation. The global performance of a whole supercomputer is then considered by identifying reduction factors that reduce the theoretical peak performance to the poor real performance. The responsibilities of the manufacturer and of the user for these losses are discussed. The price-performance ratio for different architectures as of January 1991 is briefly mentioned. Finally a user-friendly architecture for a supercomputer is proposed.
Piecemeal Learning of an Unknown Environment
Authors: Margrit Betke, Ronald L. Rivest, Mona Singh
Venue: Machine Learning (1995)

We introduce a new learning problem: learning a graph by piecemeal search, in which the learner must return every so often to its starting point (for refueling, say). We present two linear-time piecemeal-search algorithms for learning city-block graphs: grid graphs with rectangular obstacles.
Analysis of Backoff Protocols for Mulitiple AccessChannels
Authors: Johan H&aringstad, Tom Leighton, Brian Rogoff
Venue: SIAM Journal on Computing (1996)

In this paper, we analyze the stochastic behavior of backoff protocols for multiple access channels such as the Ethernet. In particular, we prove that binary exponential backoff is unstable if the arrival rate of new messages at each station is $\lam/N$ for any $\lam >{1\over 2}$ and the number of stations N, is sufficiently large. For small $N$ we prove that $\lam \geq \lam_0+{1\over 4N-2}$ implies instability where $\lam_0\approx .567$. More importantly, we also prove that any superlinear polynomial backoff protocol (e.g., quadratic backoff) is stable for any set of arrival rates that sum to less than one, and any number of stations. The results significantly extend the previous work in the area, and provide the first examples of acknowledgment based protocols known to be stable for a nonnegligible overall arrival rate distributed over an arbitrarily large number of stations. The results also disprove a popular assumption that exponential backoff is the best choice among acknowledgment based protocols for systems with large overall arrival rates. Finally, we prove that any linear or sublinear backoff protocol is unstable if the arrival rate at each station is $\lambda \over N$ for any fixed $\lambda$ and sufficiently large $N$.}
Rules and strategies for transforming functional and logic programs
Authors: Alberto Pettorossi, Maurizio Proietti
Venue: ACM Computing Surveys (CSUR) (1996)

We present an overview of the program transformation methodology, focusing our attention on the so-called &ldquo;rules + strategies&rdquo; approach in the case of functional and logic programs. The paper is intended to offer an introduction to the subject. The various techniques we present are illustrated via simple examples.
A New Noncoforming Finite Element Method for the Computation of Electromagnetic Guided Waves I: Mathematical Analysis
Authors: P. Joly, C. Poirier, J. E. Roberts, P. Trouve
Venue: SIAM Journal on Numerical Analysis (1996)

We are concerned with the problem of computing electromagnetic guided waves in a closed, inhomogeneous, cylindrical wave guide. These waves correspond to solutions of an eigenvalue problem, and classical methods produce, in addition to approximations to the solutions, spurious modes which are particularly troublesome because they correspond to nonzero approximations of the 0 eigenvalue. A nonconforming finite element method for the calculation of guided waves without spurious modes is introduced and analyzed.
Determining method for grey relational distinguished coefficient
Authors: Fengchao Zuo
Venue: ACM SIGICE Bulletin (1995)

According to the thought of information materialism in this paper, the intension of grey information capacity for grey relational distinguished coefficient zeta; was dissected. A method for determining grey relational distinguished coefficient zeta; was given, which cause the grey relational superior analysis to new levels.
Higher-order distributed objects
Authors: Henry Cejtin, Suresh Jagannathan, Richard Kelsey
Venue: ACM Transactions on Programming Languages and Systems (TOPLAS) (1995)

We describe a distributed implementation of Scheme that permits efficient transmission of higher-order objects such as closures and continuations. The integration of distributed communication facilities within a higher-order programming language engenders a number of new abstractions and paradigms for distributed computing. Among these are user-specified load-balancing and migration policies for threads, incrementally linked distributed computations, and parameterized client-server applications. To our knowledge, this is the first distributed dialect of Scheme (or a related language) that addresses lightweight communication abstractions for higher-order objects.
Automatic correction to misspelled names: a fourth-generation language approach
Authors: Michael Allen Bickel
Venue: Communications of the ACM (1987)

Using an information theoretic likeness measure defined as an inner product on a data space created from a table of valid names, this 4GL procedure searches the database space for the nearest correctly spelled name.
Time/space tradeoffs for polygon mesh rendering
Authors: Reuven Bar-Yehuda, Craig Gotsman
Venue: ACM Transactions on Graphics (TOG) (1996)

We investigate architechural schemes, generalizing that of existing graphics engines, supporting fast rendering of traingle meshes. A mesh defined on n vertices is rendered by sending vertices down a graphics pipeline, after which they are pushed on a stack to by popped when no longer needed. Only individual traingles whose vertices are present in the stack may be rendered. The storage cost of the mesh rendering is the size of the stack required to store mesh vertices during the rendering process. This may be significantly less than n. The time cost of the mesh rendering is the number of vertices sent down the graphics pipeline. If a large enough stack is available, it usuffices to send each vertix once. If only a small stack is available, some vertices may have to be sent more than once, so a time/space tradeoff exists. With our architecture, stack of size O n is sufficient to render any triangle mesh defined on n vertices, such that each vertex is sent only once through the graphics pipeline (time cost = n). We provide an algorithm that generates an appropriate &ldquo;rendering sequence&rdquo; of commands for any given mesh. Moreover, we show that no algorithm can do better, that is, W n is a lower bound. Some n-vertex meshes may be rendered using a stack whose size is significantly less than O n. An algorithm generating a minimum-time rendering sequence rquiring the minimum stack size is an open question. We provide an approximation: if it is theoretically possible to render a triangle mesh is minimum time with a stack of size S, our algoithm generates a minimum-time rendering sequence requiring a stack of size no larger than 2S log3/2n. If only a stack of size k is available, we provide an algorithm generating a rendering sequence requiring a stack of size no larger than k, such that at most n(1+c/k) vertices must be sent through the pipeline, for some constant c.
Precision Tracking Based on Segmentation with Optimal Layering for Imaging Sensors
Authors: Anil Kumar, Yaakov Bar-Shalom, Eliezer Oron
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1995)

In our previous work [5], we presented a method for precision tracking of a low observable target based on data obtained from imaging sensors. The image was divided into several layers of gray level intensities and thresholded. A binary image was obtained and grouped into clusters using image segmentation techniques. Using the centroid measurements of the clusters, the Probabilistic Data Association Filter (PDAF) was employed for tracking the target centroid.In this correspondence, the division of the image into several layers of gray level intensities is optimized by minimizing the Bayes risk. This optimal layering of the image has the following properties: 1) following the segmentation, a closed-form analytical expression is obtained for the noise variance of the centroid measurement based on a single frame; 2) in comparison to [5], the measurement noise variance is smaller by at least a factor of 2, thus improving the performance of the tracker.The usefulness of the method for practical applications is demonstrated by considering a sequence of real target images (a moving car) of about 20 pixels in size in a noisy urban environment where the measurement noise was calculated as having 0.32 pixel RMS value. Filtering with the PDAF further reduces this by a factor of 1.6.