ppxscal/embedding_network huggingface dataset:
Performance Modeling and Evaluation of Circuit Switching Using Clos Networks
Authors: Youngsong Mun, Hee Yong Youn
Venue: IEEE Transactions on Computers (1994)

Call packing has been recognized as a routing scheme that significantly reduces the blocking probability of connection requests in a circuit-switched Clos multistage interconnection network. In this paper, for the first time, we develop general analytical models for the point-to-point blocking probability of the call-packing scheme applied to Clos networks. By introducing a new parameter called the degree of call packing, the models can correctly estimate the blocking probability of both call-packing and random routing schemes. The models are verified by computer simulation for various size networks and traffic conditions.
A Multicarrier Scheme for HIPERLAN
Authors: Michael Aldinger
Venue: Wireless Personal Communications: An International Journal (1997)

After a short description of the principles of a multicarrier COFDM (Coded Orthogonal Frequency Division Multiplex) scheme some simulation results concerning bit- and packet error rates gained with three different characteristic multipath channels are presented and discussed. Aspects of COFDM design principles and complexity of the modulation and demodulation part of the system, as well as effects of the non-linearity of amplifiers will be addressed.
A Hybrid Procedural/Deductive Executive for Autonomous Spacecraft
Authors: Barney Pell, Edward B. Gamble, Erann Gat, Ron Keesing, James Kurien, William Millar, Christian Plaunt, Brian C. Williams
Venue: Autonomous Agents and Multi-Agent Systems (1999)

The New Millennium Remote Agent (NMRA) will be the first AI system to control an actual spacecraft. The spacecraft domain places a strong premium on autonomy and requires dynamic recoveries and robust concurrent execution, all in the presence of tight real-time deadlines, changing goals, scarce resource constraints, and a wide variety of possible failures. To achieve this level of execution robustness, we have integrated a procedural executive based on generic procedures with a deductive model-based executive. A procedural executive provides sophisticated control constructs such as loops, parallel activity, locks, and synchronization which are used for robust schedule execution, hierarchical task decomposition, and routine configuration management. A deductive executive provides algorithms for sophisticated state inference and optimal failure recovery planning. The integrated executive enables designers to code knowledge via a combination of procedures and declarative models, yielding a rich modeling capability suitable to the challenges of real spacecraft control. The interface between the two executives ensures both that recovery sequences are smoothly merged into high-level schedule execution and that a high degree of reactivity is retained to effectively handle additional failures during recovery.
An Access Control Model and Its Use in Representing Mental Health Application Access Policy
Authors: Vijay Varadharajan, Claudio Calvelli
Venue: IEEE Transactions on Knowledge and Data Engineering (1996)

This paper considers an access control model and proposes extensions to it to deal with authentication and revocation. The model is then applied to represent access control policy in a mental health system.In the first part of the paper, extensions to the Schematic Protection Model (SPM) are presented. The authentication and revocation extensions are independent of one another in the sense that each one affects a different part of the decision algorithm. The extensions comprise a modification of the syntax to be able to represent the new concepts and, more importantly, a modification of the decision algorithm for the safety problem to take these changes into account.We introduce the concept of conditional tickets and use it to provide authentication. Apart from this, we have found this concept to be useful in modeling systems. Hence we have separated this (syntactical) issue from the definition of the new algorithm.The second part considers the access policy for a mental health application. We have used the extensions of SPM to model part of this access policy. Even with our extensions, SPM still remains a monotonic model, where rights can be removed only in very special cases, and this makes it impossible to represent all the aspects of the problem. Other than to serve as an example for the extensions we propose, this paper also helps to separate aspects of this access control policy which are inherently monotonic from parts which are defined in a non-monotonic way, but can still be represented in a monotonic model.
Distributed computing with high-speed optical networks
Authors: Ronald J. Vetter, David H. C. Du
Venue: Computer (1993)

An environment that uses wavelength division multiplexing techniques and optical switching and processing to provide large bandwidths, short delays, and multiple data streams for distributed processing is described. The focus is on the interrelationship between application needs and network services. The system level, a conceptual layer designed to bridge the gap between application requirements and underlying high-speed network services, is proposed. The system level is a logical view of the physical network represented by a virtual topology projected onto the physical network. Embedding this virtual topology introduces many new problems and performance tradeoffs into the design of the network. A few of these problems are outlined, and some initial research efforts in this area are discussed. The physical network level, the collection of optical fiber links interconnecting the nodes in the network, and the application level, a logical view of an application's computational topology and representation of the application's communication and computing requirements, are also described.
Testing Component-Based Software: A Cautionary Tale
Authors: Elaine J. Weyuker
Venue: IEEE Software (1998)

Components designed for reuse are expected to lower costs and shorten the development life cycle, but this may not prove so simple. The author emphasizes the need to closely examine a problematic aspect of component reuse: the necessity and potential expense of validating components in their new environments.
Websigns: Hyperlinking Physical Locations to the Web
Authors: Salil Pradhan, Cyril Brignone, Jun-Hong Cui, Alan McReynolds, Mark T. Smith
Venue: Computer (2001)

First-generation mobile computing technologies typically use protocols such as WAP and i-mode to let PDAs, smart phones, and other wireless devices with Web browsers access the Internet, thereby freeing users from the shackles of their desktops. Users could, the authors assert, benefit from having access to devices that combine the advantages of wireless technology and ubiquitous computing to provide a transparent linkage between the physi-cal world around them and the resources available on the Web. In the CoolTown research program at Hewlett-Packard Laboratories, the authors are building ubiquitous computing systems that sense physical entities in the environment and map them to a Web browser. The websign system provides an alternative way to map e-services using a simple form of augmented reality. Typical augmented reality systems require users to wear a cumbersome see-through head-mounted display to view computer-generated images imposed on the physical environment. In contrast, the websign system uses commonly available Internet-enabled wireless devices such as PDAs or smart phones equipped with client software, a positioning system such as GPS, and a digital compass to visualize services for physical entities. From a deployment perspective, the system is more scalable for outdoor applications than using physical short-range beacons. The lack of commonly available and deployed indoor positioning technologies has hindered indoor deployment, but the authors are currently evaluating a promising technology from the Massachusetts Institute of Technology for use as the underlying indoor positioning system. They are also conducting further user studies that explore how to better augment reality with virtual beacons and tags.
A Universal Relation Data Model with Semantic Abstractions
Authors: T. -H. Chang, E. Sciore
Venue: IEEE Transactions on Knowledge and Data Engineering (1992)

Two important features of modern database models are support for complex data structures and support for high-level data retrieval and update. The first issue has been studied by the development of various semantic data models; the second issue has been studied through universal relation data models. How the advantages of these two approaches can be combined is presently examined. A new data model that incorporates standard concepts from semantic data models such as entities, aggregations, and ISA hierarchies is introduced. It is then shown how nonnavigational queries and updates can be interpreted in this model. The main contribution is to demonstrate how universal relation techniques can be extended to a more powerful data model. Moreover, the semantic constructs of the model allow one to eliminate many of the limitations of previous universal relation models.
Optimization and Evaluation of Disjunctive Queries
Authors: Jens Claussen, Alfons Kemper, Guido Moerkotte, Klaus Peithner, Michael Steinbrunn
Venue: IEEE Transactions on Knowledge and Data Engineering (2000)

It is striking that the optimization of disjunctive queries¿i.e., those which contain at least one or-connective in the query predicate¿has been vastly neglected in the literature, as well as in commercial systems. In this paper, we propose a novel technique, called bypass processing, for evaluating such disjunctive queries. The bypass processing technique is based on new selection and join operators that produce two output streams: the true-stream with tuples satisfying the selection (join) predicate and the false-stream with tuples not satisfying the corresponding predicate. Splitting the tuple streams in this way enables us to ¿bypass¿ costly predicates whenever the ¿fate¿ of the corresponding tuple (stream) can be determined without evaluating this predicate. In the paper, we show how to systematically generate bypass evaluation plans utilizing a bottom-up building block approach. We show that our evaluation technique allows to incorporate the standard SQL semantics of null values. For this, we devise two different approaches: One is based on explicitly incorporating three-valued logic into the evaluation plans; the other one relies on two-valued logic by ¿moving¿ all negations to atomic conditions of the selection predicate. We describe how to extend an iterator-based query engine to support bypass evaluation with little extra overhead. This query engine was used to quantitatively evaluate the bypass evaluation plans against the traditional evaluation techniques utilizing a CNF- or DNF-based query predicate.
Flow Stability of Patchy Vector Fields and Robust Feedback Stabilization
Authors: Fabio Ancona, Alberto Bressan
Venue: SIAM Journal on Control and Optimization (2002)

The paper is concerned with patchy vector fields, a class of discontinuous, piecewise smooth vector fields that were introduced by the authors to study feedback stabilization problems. We prove the stability of the corresponding solution set w.r. t. a wide class of impulsive perturbations. These results yield the robustness of patchy feedback controls in the presence of measurement errors and external disturbances.
Predicting the Future
Authors: Kay-Yut Chen, Leslie R. Fine, Bernardo A. Huberman
Venue: Information Systems Frontiers (2003)

We present a novel methodology for predicting future outcomes that uses small numbers of individuals participating in an imperfect information market. By determining their risk attitudes and performing a nonlinear aggregation of their predictions, we are able to assess the probability of the future outcome of an uncertain event and compare it to both the objective probability of its occurrence and the performance of the market as a whole. Experiments show that this nonlinear aggregation mechanism vastly outperforms both the imperfect market and the best of the participants. We then extend the mechanism to prove robust in the presence of public information.
Extremal problems on set systems
Authors: Peter Frankl, Vojtech Rödl
Venue: Random Structures Algorithms (2002)

For a family F(k) = {F1(k), F2(k), ..., Ft(k)} of k-uniform hypergraphs let ex (n, F(k)) denote the maximum number of k-tuples which a k-uniform hypergraph on n vertices may have, while not containing any member of F(k). Let rk(n) denote the maximum cardinality of a set of integers Z ⊂ [n], where Z contains no arithmetic progression of length k. For any k ≥ 3 we introduce families F(k) = {F1(k), F2(k)} and prove that nk-2rk(n) ≤ ex(nk2, F(k)) ≤ Cknk-1 holds. We conjecture that ex(n, F(k)) = o(nk-1) holds. If true, this would imply a celebrated result of Szemerédi stating that rk(n) = o(n). By an earlier result o Ruzsa and Szemerédi, our conjecture is known to be true for k = 3. The main objective of this article is to verify the conjecture for k = 4. We also consider some related problems.
Optimal Realization of Any BPC Permutation on K-Extra-Stage Omega Networks
Authors: Xiaojun Shen
Venue: IEEE Transactions on Computers (1995)

An N×N k-Omega network is obtained by adding k more stages in front of an Omega network. An N-permutation defines a bijection between the set of N sources and the set of N destinations. Such a permutation is said to be admissible to a k-Omega if N conflict-free paths, one for each source-destination pair defined by the permutation, can be established simultaneously. When an N-permutation is not admissible, it is desirable to divide the N pairs into a minimum number of groups (passes) such that the conflict-free paths can be established for the pairs in each group. Raghavendra and Varma solved this problem for BPC (Bit Permutation Complement) permutations on an Omega without extra stage. This paper generalizes their result to a k-Omega where k can be any integer between 0 and n¿¿1. An O(NlgN) algorithm is given which realizes any BPC permutation in a minimum number of passes on a k-Omega (0 ¿k¿n¿¿1).
Performance of a Hedged Stochastic Portfolio Model in the Presence of Extreme Events
Authors: Rosella Castellano, Rosella Giacometti
Venue: Computational Economics (2001)

Classical methods for computing the value-at-risk (VaR) do not account for the large price variations observed in financial markets. The historical method is subject to event risk and may miss some fundamental market evolution relevant to VaR; the variance/covariance method tends to underestimate the distribution tails and Monte Carlo simulation is subject to model risk. These methods are thereby usually completed with analyses derived from catastrophe scenarios. We propose a special case of the extreme-value approach for computing the value-at-risk of a stochastic multicurrency portfolio when alternative hedging strategies are considered. This approach is able to cover market conditions ranging from the usual VaR environment to financial crises. We implement a multistage portfolio model with an exchange rate dynamic with stochastic volatility. The parameters are estimated by GARCH-t models. The simulations are used to select multicurrency portfolios whose exchange rate risk is hedged and rebalanced each ten days, accounting for VaR. We compare the performances of the two most classical institutional options strategies &ndash; protective puts and covered calls &ndash; to that of holding an unhedged portfolio in presence of extreme events.
The battle of the seals
Authors: Keith P. Clive
Venue: Cryptologia (2002)

This article is primarily about the seals of the National Security Agency (NSA) and its Central Security Service (CSS). Specifically, this article provides, for the first time, a copy of the NSA seal that preceded the current one, a copy of the CSS seal, and their respective histories. A brief biography of the current CSS Deputy Chief and a very brief history about CSS itself is also provided. A number of references are made to James Bamford's two books: Body of Secrets (May 2001) and The Puzzle Palace (1982). My intention is not to nitpick his works. Rather, I simply wish to clarify points that readers may find confusing, especially since he is the world's leading authority on NSA. I not only admire Bamford's investigative journalism, but also strive toward the very high standard that he has set.
Nesting points in the sphere
Authors: Dan Archdeacon, Feliu Sagols
Venue: Discrete Mathematics (2002)

Let G be a graph embedded in the sphere. A k-nest of a point x not in G is a collection C1,....,Ck of disjoint cycles such that for each Ci, the side containing x also contains Cj for each j > i. An embedded graph is k-nested if each point not on the graph has a k-nest. In this paper we examine k-nested maps. We find the minor-minimal k-nested maps small values of k. In particular, we find the obstructions (under the minor order) for the class of planar maps with the property that one face's boundary meets all other face boundaries.
A Reservation-Based Algorithm for Scheduling Both Periodic and Aperiodic Real-Time Tasks
Authors: Yi-Chieh Chang, Kang G. Shin
Venue: IEEE Transactions on Computers (1995)

This paper considers the problem of scheduling both periodic and aperiodic tasks in real-time systems. A new, called reservation-based (RB), algorithm is proposed for ordering the execution of real-time tasks. This algorithm can guarantee all periodic-task deadlines while minimizing the probability of missing aperiodic-task deadlines. Periodic tasks are scheduled according to the rate monotonic priority algorithm (RMPA), and aperiodic tasks are scheduled by utilizing the processor time left unused by periodic tasks in each unit cycle. The length, u, of a unit cycle is defined as the greatest common divisor of all task periods, and a task is assumed to be invoked at the beginning of a unit cycle. For a set S of periodic tasks, the RB algorithm reserves a fraction RS of processor time in each unit cycle for executing aperiodic tasks without missing any periodic-task deadline. The probability of meeting aperiodic-task deadlines is proved to be a monotonic increasing function of RS. We derive the value of RS that maximizes the processor time reservable for the execution of aperiodic tasks without missing any periodic-task deadline. We also show that if the ratio of the computation time to the deadline of each aperiodic task is bounded by RS, the RB algorithm can meet the deadlines of all periodic and aperiodic tasks. Our analysis and simulation results show that the RB algorithm outperforms all other scheduling algorithms in meeting aperiodic-task deadlines.
Embedding of Rings and Meshes onto Faulty Hypercubes Using Free Dimensions
Authors: Pei-Ji Yang, Sing-Ban Tien, C. S Raghavendra
Venue: IEEE Transactions on Computers (1994)

Fault tolerance in hypercubes is achieved by exploiting inherent redundancy and executing tasks on faulty hypercubes. The authors consider tasks that require linear chain, ring, mesh, and torus structure, which are quite useful in parallel and pipeline computations. They assume the number of faults is on the order of the number of dimensions of the hypercube. The techniques are based on a key concept called free dimension, which can be used to partition a cube into subcubes such that each subcube contains, at most, one faulty node. Subgraphs are embedded in each subcube and then merged to form the entire graph.
Heterogeneous Computing: Challenges and Opportunities
Authors: Ashfaq A. Khokhar, Viktor K. Prasanna, Muhammad E. Shaaban, Cho-Li Wang
Venue: Computer (1993)

The issues and problems posed by heterogeneous computing are discussed. They include design of algorithms for applications, partitioning and mapping of application tasks, interconnection requirements, and the design of programming environments. The use of heterogeneous computing in image understanding is reviewed. An example vision task is presented, and the different types of parallelism used in the example are identified.
Point-SE Education: We're on Our Own
Authors: James Bach
Venue: IEEE Software (1997)

James Bach and Michael McCracken discuss whether software engineers can best learn the practice of software engineering in industry, via apprenticeship methods, or in universities, via formal education. Their contending viewpoints show the strengths of both environments and suggest synergistic ways in which they can interact.
The effects of badly behaved routers on Internet congestion
Authors: Kevin Curran, Derek Woods, Nadene McDermot, Colleen Bradley
Venue: International Journal of Network Management (2003)

From an exhaustive series of trace packets to a diverse set of destinations, our research has discovered that specific routers are the cause of bottlenecks in the Internet. We found that packets took the same route each time towards their destination. Our research has also found that over periods as large as seven days these routers continue to cause bottlenecks with no re-routing of packets to alleviate congestion. This research begs the question as to why these bottlenecks occur at the same places and for so long a period and also queries the extent of implementation of dynamic routing algorithms.
Integrating Security into the Curriculum
Authors: Cynthia E. Irvine, Shiu-Kai Chin, Deborah Frincke
Venue: Computer (1998)

An educational system that cultivates an appropriate knowledge of computer security will increase the likelihood that the next generation of IT workers will have the background needed to design and develop systems that are engineered to be reliable and secure. The technical aspects of security are closely related to computer science and engineering. And many of the goals, concepts, and reasoning techniques are similar too. Thus, two approaches are possible: Computer security could be the focus of the curriculum, which would investigate the foundations and technical approaches to security in considerable depth. A computer science or computer engineering curriculum could choose to use computer security as an important property to be addressed in all coursework. The authors argue that it is not reasonable to suggest that every student should learn everything about security. Instead, they propose an approach that matches appropriate knowledge and skills with typical roles in the information society. In this way, security insights can be integrated within the existing information systems programs, rather than be treated separately. This article, therefore, proposes a set of high-level educational objectives as the basis of a security-enhanced curriculum.
Performance Analysis of Cluster-Based Multiprocessors
Authors: P. Mohapatra, C. R. Das, Tse-yun Feng
Venue: IEEE Transactions on Computers (1994)

A queueing model for performance evaluation of cluster-based multiprocessors is proposed. Most system components are modeled as M/D/1/L queues to capture deterministic service time and finite buffer behavior. Various subsystems are analyzed independently and then integrated for the system level analysis. Average delay, throughput, and processor utilization are the performance parameters studied in this analysis. The analytical results are first validated via simulation. Next, several design alternatives are discussed using the model. These include the effect of buffer length and identification of bottleneck centers for various design configurations.