bluuebunny/crossref_metadata_2025 huggingface dataset:
STRONGLY ENHANCED LOW ENERGY α-PARTICLE DECAY IN HEAVY ACTINIDE NUCLEI AND LONG-LIVED SUPERDEFORMED AND HYPERDEFORMED ISOMERIC STATES
Authors: MARINOV A. , GELBERG S. , KOLB D. , WEIL J. L.
Published: July 2002

Unidentified low energy and very enhanced α-particle groups have been observed in various actinide fractions produced via secondary reactions in a CERN W target which had been irradiated with 24-GeV protons. In particular, 5.14, 5.27 and 5.53 MeV α-particle groups with corresponding half-lives of 3.8±1.0 y, 625±84 d and 26±7d, have been seen in Bk, Es and Lr-No sources, respectively. The measured energies are a few MeV lower than the known ground state to ground state α-decays in the corresponding neutron-deficient actinide nuclei. The half-lives are 104to 107shorter than expected from energy versus lifetime relationship for such low-energy α-particles in this region of nuclei. The deduced evaporation residue cross sections are in the mb region, about 104times higher than expected. Not only is it impossible to identify these α-decays with any known activity in the whole nuclear chart, but they also could not be due to hypothetically unknown isomeric states in various conceivable neutron deficient nuclei, nor due to unknown isomeric states in the rare-earth region. Based on the fact that in other experiments we have found isomeric states in the second and third minima of the potential for other heavy ion reaction products, one can now understand in a quantitative way, both the unusual low energies, the unusual enhanced lifetimes and the unusual large production cross sections, in terms of production of similar isomeric states in appropriate actinide isotopes. Some consequences regarding the production of the long-lived superheavy elements are also discussed.
A MULTIPLE GRANULARITY LOCKING PROTOCOL FOR CSCW
Authors: PAPADOPOULOS CONSTANTINOS
Published: July 2002

Locking is a commonly used mechanism in Computer Supported Cooperative Work (CSCW) for coordinating concurrent users and implementing various styles of information sharing. Part of a sharing style's definition is the granularity of shared objects. Since this varies among different applications, it is desirable to provide a range of different lock granules. In this paper, I first examine existing multiple granularity locking protocols and I evaluate their suitability for CSCW. My main contribution is the development of a new such protocol specifically for CSCW, which provides versionable object locking, guarantees conflict freedom, prevents update loss and ensures greater concurrency than other locking protocols. Its suitability for CSCW is justified by a comparative performance analysis.
EFFECTS OF SIMULATED FIXED FEMORAL ROTATION ON THE PATELLOFEMORAL JOINT: IN VITRO AND IN VIVO BIOMECHANICAL ASSESSMENT IN CANINES
Authors: Lee Thay Q , Schulz Michele M. , McMahon Patrick J.
Published: July 2002

The quantitative effects of fixed femoral rotation on the patellofemoral joint were assessed in canines in vitro and in vivo. For the in vitro study, ten canine knees were examined in neutral and 30 degrees of internal and external fixed femoral rotations. Fuji film was inserted into the patellofemoral joint and quadriceps loading was simulated at 60 and 90 degrees of knee flexion. There was significant increase in patellofemoral contact pressures on the contralateral facets of the patella with 30 degrees of fixed femoral rotation at both knee flexion angles (p < 0.05). For the in vivo study, 12 skeletally mature mongrel dogs were subjected to either internal or external bilateral femoral rotational deformity of 30 degrees. Three animals served as controls. Biomechanical evaluation of the articular cartilage showed a statistically significant decrease for both the unrelaxed and relaxed apparent shear modulus at six months for both internal and external femoral rotations (p < 0.05) in comparison to the control. In vivo results from fixed femoral rotation on the patellofemoral joint correlate with that expected from in vitro biomechanical results. The results from this study suggest that rotational deformity of the femur should be corrected within six months to prevent patellofemoral joint arthrosis.
Effects of Ownership and Internalization Advantages on Performance: The Case of Japanese Subsidiaries in the United States and Latin America
Authors: Vega-Céspedes Cristian , Hoshino Yasuo
Published: July 2002

This paper attempts to prove empirically that ownership and internalization advantages play a more important role than entry mode in explaining the attained performance of subsidiary companies. While a direct effect of ownership and internalization advantages on performance was found, a relation between entry mode and performance is not evident. A logistic regression model is applied to two samples, i.e., two states in the United States and countries of Latin America.
FIRMS DECISION MAKING PROCESS IN AN EVOLUTIONARY MODEL OF INDUSTRIAL DYNAMICS
Authors: KWASNICKI WITOLD
Published: July 2002

Evolutionary model of industrial dynamics, presented in this paper, can be classified as Schumpeterian one. The model describes the behaviour of a number of competing firms producing functionally equivalent products. Each firm tries to improve its position in the industry and in the market by introducing innovations in order to minimize the unit costs of production, maximize the productivity of capital, and maximize the competitiveness of its products on the market. The problem how decisions are made seems to be crucial for relevant modelling of socio-economic processes. The main aim of the simulations presented in the second part of the paper is to show how fluctuations and discontinuities occurs in economic processes due to boundedly rational decisions of competing firms. It is shown how fluctuation of 3–6 years and of 10 years periodicity can occur in an industry development because of firms' bounded rationality. Long waves of development of 50–60 years period (Kondratieff cycles) occur in the model because of radical innovation emergence at the maturity phase of an 'old' technology.
STRATEGIC ENVIRONMENTAL ASSESSMENT AS A MEANS OF PURSUING SUSTAINABILITY: TEN ADVANTAGES AND TEN CHALLENGES
Authors: STINCHCOMBE KIRK , GIBSON ROBERT B.
Published: July 2002

While strategic environmental assessment can be a powerful tool for fostering progress towards sustainability, effective implementation involves confronting a set of substantial challenges. This paper, based on Canadian and international literature and experience, outlines the ten most compelling advantages of strategic environmental assessment for sustainability and the ten main challenges faced in implementation.

The ten advantages of the strategic environmental assessment for sustainability are that it

• provides a process for integrated pursuit of sustainability objectives in policy making and planning;

• operationalises sustainability principles;

• improves the information base for policy making, planning and programme development;

• is proactive and broad in ways that strengthen consideration of fundamental issues;

• improves analysis of broad public purposes and alternatives;

• facilitates proper attention to cumulative effects;

• facilitates greater transparency and more effective public participation at the strategic level;

• provides a framework for more effective and efficient project-level assessments;

• provides a base for design and implementation of better projects where project-level assessment is not required; and

• facilitates establishment of a more comprehensive overall system of sustainability application at all levels from the setting of decision objectives to the monitoring of implementations effects.

The ten main challenges for effective implementation are

• limited information and unavoidable uncertainties;

• boundary-setting complexities;

• primitive methodologies;

• difficulties in defining the proper role of public participants and ensuring effective involvement;

• co-ordination and integration of strategic assessment with assessment processes at other levels;

• institutional resistance;

• conflict between integrated assessment and bureaucratic fragmentation;

• jurisdictional overlap;

• limitations of the standard rational planning and policy making model; and

• resistance to integration of strategic assessment in core decision making.

The paper concludes with a discussion of the major implications.
Private life in cyberspace
Authors: Barlow John Perry
Published: July 2002

I have lived most of my life in a small Wyoming town, where there is little of the privacy which both insulates and isolates suburbanites. Anyone in Pinedale who is interested in me or my doings can get most of that information in the Wrangler Café. Between them, any five customers could probably produce all that is known locally about me—including a number of items that are well known but not true. me—including a number of items that are well known but not true.
Generating automatically tuned bitmaps from outlines
Authors: Hobby John D.
Published: July 2002

Consider the problem of generating bitmaps from character shapes given as outlines. The obvious scan-conversion process does not produce acceptable results unless important features such as stem widths are carefully controlled during the scan-conversion process. This paper describes a method for automatically extracting the necessary feature information and generating high-quality bitmaps without resorting to hand editing. Almost all of the work is done in a preprocessing step, the result of which is an intermediate form that can be quickly converted into bitmaps once the font size and device resolution are known.

A heuristically defined system of linear equations describes how the ideal outlines should be distorted in order to produce the best possible results when scan converted in a straightforward manner. The Lova´sz basis reduction algorithm then reduces the system of equations to a form that makes it easy to find an approximate solution subject to the constraint that some variables must be integers.

The heuristic information is of such a general nature that it applies equally well to Roman fonts and Japanese Kanji.
Portable vectorized software for Bessel function evaluation
Authors: Boisvert Ronald F. , Saunders Bonita V.
Published: July 2002

A suite of computer programs for the evaluation of Bessel functions and modified Bessel functions of orders zero and one for a vector of real arguments is described. Distinguishing characteristics of these programs are that (a) they are portable across a wide range of machines, and (b) they are vectorized in the case when multiple function evaluations are to be performed. The performance of the new programs are compared with software from the FNLIB collection of Fullerton on which the new software is based.
The design of floating-point data types
Authors: Goldberg David
Published: July 2002

The issues involved in designing the floating-point part of a programming language are discussed. Looking at the language specifications for most existing languages might suggest that this design involves only trivial issues, such as whether to have one or two types of REALs or how to name the functions that convert from INTEGER to REAL. It is shown that there are more significant semantic issues involved. After discussing the trade-offs for the major design decisions, they are illustrated by presenting the design of the floating-point part of the Modula-3 language.
Distributed last call optimization for portable parallel logic programming
Authors: Ramkumar Balkrishna
Published: July 2002

A difficult but challenging problem is the efficient exploitation of AND and OR parallelism in logic programs without making any assumptions about the underlying target machine(s). In earlier papers, we described the design of a binding environment for AND and OR parallel execution of logic programs on shared and nonshared memory machines and the performance of a compiler (called ROLOG) using this binding environment on a range of MIMD parallel machines.

In this paper, we present an important optimization for
portable
parallel logic programming, namely
distributed last-call optimization
, an analog of the tail recursion optimization for sequential Prolog. This scheme has been implemented in the ROLOG compiler, which ports
unchanged
on several shared memory and nonshared memory machines. We describe the effect of this optimization on several OR, AND/OR and AND parallel benchmark programs.
A noniterative thinning algorithm
Authors: Neusius Christian , Olszewski Jan
Published: July 2002

Thinning algorithms are applied in image processing to compute a skeleton of an image. In this paper a new thinning method is presented which differs in its approach from other thinning algorithms. In the presented algorithm the minimal distance of a pixel to the edge of the containing object is used to extract the skeleton. Given an
n x n
matrix of pixels, the algorithm runs in time

O(n
2
)

. Our measurements show that it is faster than other known sequential algorithms. The mathematical background of the algorithm and the proof of essential features of the obtained skeleton are based on the consideration of the pattern as a directed graph.
On the power of bounded concurrency II
Authors: Hirst Tirza , Harel David
Published: July 2002

This is the second in a series of papers on the inherent power of bounded cooperative concurrency, whereby an automaton can be in some bounded number of states that cooperate in accepting the input. In this paper, we consider pushdown automata. We are interested in differences in power of expression and in exponential (or higher) discrepancies in succinctness between variants of pda's that incorporate nondeterminism (E), pure parallelism (A), and bounded cooperative concurrency (C). Technically, the results are proved for cooperating push-down automata with cooperating states, but they hold for appropriate versions of most concurrent models of computation. We exhibit exhaustive sets of upper and lower bounds on the relative succinctness of these features for three classes of languages: deterministic context-free, regular, and finite. For example, we show that C represents exponential savings in succinctness in all cases except when both E and A are present (i.e., except for alternating automata), and that E and A represent
unlimited
savings in succinctness in all cases.
Generating triangulations at random
Authors: Epstein Peter , Sack Jörg-Rüdiger
Published: July 2002

An

O(n
3
)

algorithm is described to count triangulations of a simple polygon with
n
vertices. This algorithm is used to construct an

O(n
4
)

algorithm to generate triangulations of a simple polygon at random with a uniform probability distribution. The problem of counting triangulations of a simple polygon is then related to existing problems in graph theory.
A new algorithm for the evaluation of the incomplete gamma function on vector computers
Authors: Früchtl H. , Otto P.
Published: July 2002

Several methods of evaluating the Incomplete Gamma Function are compared according to accuracy and computation time. An improved algorithm is presented which allows significantly faster computation of two-electron integrals on most vector computers, especially in the case of GLO functions. Parameters for

F
0
(t)

are tabulated.
Cognition and software development
Authors: Stacy Webb
Published: July 2002

Not long ago, programmers controlled computers by arranging wires on a control panel built into the side of a large floor-standing machine. Today palm-sized pointing devices are used to drag and drop visual images on machines smaller than a notebook. Dramatic differences like these make it easy to forget that software development still revolves around the needs of the computer at the expense of the needs of developers and end users.
An appreciation of Laurence Rosenberg
Authors: Olson Gary M.
Published: July 2002

It takes many different kinds of contributions to create a viable research community, and many dedicated people have made major contributions in the past decade to make things like the NSF Digital Libraries initiative happen. I'd like to take a few moments to honor one such individual who left our community when he died this past spring following a brave fight with cancer. Laurence Rosenberg affected many of our lives and careers through his activities and his vision as a program manager and a deputy director in the Division of Information, Robotics, and Intelligent Systems at the National Science Foundation.
Algorithm 747: a Fortran subroutine to solve the eigenvalue assignment problem for multiinput systems using state feedback
Authors: Miminis George , Roth Helmut
Published: July 2002

The implementation of an algorithm for the computation of a state feedback for multiinput linear systems, resulting in a closed-loop matrix with a specified self-conjugate set of eigenvalues, is presented. The computation uses only real arithmetic, assigning complex conjugate eigenvalues in one double step. The implementation uses level-1
BLAS
routines where possible. A brief description of the algorithm is also given.
An interview with the 1986 A. M. Turing Award recipients—John E. Hopcroft and Robert E. Tarjan
Authors: Frenkel Karen A. , Hopcroft John E. , Tarjan Robert E.
Published: July 2002

In the following interview, which took place at the 1986 Fall Joint Computer Conference in Dallas, Texas, John Hopcroft and Robert Tarjan discuss their collaboration and its influence on their separate research today. They also comment on supercomputing and parallelism, particularly with regard to statements by FJCC Keynote speakers Kenneth Wilson, Nobel laureate and director of Cornell University's Supercomputer Center, and C. Gordon Bell, chief architect on the team that designed DEC's VAX and now with the National Science Foundation. Finally the Turing Award winners air their views on the direction of computer science as a whole and on funding and the Strategic Defense Initiative.
New horizons in commercial and industrial AI
Authors: Munakata Toshinori
Published: July 2002

AI as a field has undergone rapid growth in diversification and practicality. For the past 10 years, the repertoire of AI techniques has evolved and expanded. Scores of newer fields have recently been added to the traditional domains of practical AI. Although much practical AI is still best characterized as advanced computing rather than
intelligence,
applications in everyday commercial and industrial settings have certainly increased, especially since 1990. Additionally, AI has shown a growing influence on other computer science areas, such as databases, software engineering, distributed computing, computer graphics, user interfaces, and stimulation.
Optimal folding of standard and custom cells
Authors: Thanvantri Venkat , Sahni Sartaj
Published: July 2002

We study the problem of folding an ordered list of standard and custom cells into rows of a chip so as to minimize either the routing area or the total chip area. Nine versions of the folding problem are formulated and fast polynomial time algorithms are obtained for each. Two of our formulations correspond to problems formulated in Paik and Sahni [1993] for the folding of a stack of bit-slice components. Our algorithms for these two formulations are asymptotically superior to those of Paik and Sahni [1993].
Fast simulation of packet loss rates in a shared buffer communications switch
Authors: Chang Cheng-Shang , Heidelberger Philip , Shahabuddin Perwez
Published: July 2002

This article describes an efficient technique for estimating, via simulation, the probability of buffer overflows in a queueing model that arises in the analysis of ATM (Asynchronous Transfer Mode) communication switches. There are multiple streams of (autocorrelated) traffic feeding the switch that has a buffer of finite capacity. Each stream is designated as being of either high or low priority. When the queue length reaches a certain threshold, only high priority packets are admitted to the switch's buffer. The problem is to estimate the loss rate of high priority packets. An asymptotically optimal importance sampling approach is developed for this rare event simulation problem. In this approach, the importance sampling is done in two distinct phases. In the first phase, an importance sampling change of measure is used to bring the queue length up to the threshold at which low priority packets get rejected. In the second phase a different importance sampling change of measure is used to move the queue length from the threshold to the buffer capacity.
Algorithm 649
Authors: Giunta G. , Murli A.
Published: July 2002

We present a package that allows the computation of the trigonometric Fourier coefficients of a smooth function. The function can be provided as a subprogram or as a data list of function values at equally spaced points.

The computational cost of the algorithm does not depend on the required number of Fourier coefficients. Numerical results of comparative tests with a standard integrator for oscillatory functions are also reported.
Inference with path resolution and semantic graphs
Authors: Murray Neil V. , Rosenthal Erik
Published: July 2002

A graphical representation of quantifier-free predicate calculus formulas in negation normal form and a new rule of inference that employs this representation are introduced. The new rule,
path resolution
, is an amalgamation of resolution and Prawitz analysis. The goal in the design of path resolution is to retain some of the advantages of both Prawitz analysis and resolution methods, and yet to avoid to some extent their disadvantages.

Path resolution allows Prawitz analysis of an arbitrary subgraph of the graph representing a formula. If such a subgraph is not large enough to demonstrate a contradiction, a path resolvent of the subgraph may be generated with respect to the entire graph. This generalizes the notions of large inference present in hyperresolution, clash-resolution, NC-resolution, and UR-resolution. A class of subgraphs is described for which deletion of some of the links resolved upon preserves the spanning property.
The mathematical basis and a prototype implementation of a new polynomial rootfinder with quadratic convergence
Authors: Hull T. E. , Mathon R.
Published: July 2002

Formulas developed originally by Weierstrass have been used since the 1960s by many others for the simultaneous determination of all the roots of a polynomial. Convergence to simple roots is quadratic, but individual approximations to a multiple root converge only linearly. However, it is shown here that the mean of such individual approximations converges quadratically to that root. This result, along with some detail about the behavior of such approximations in the neighborhood of the multiple root, suggests a new approach to the design of polynomial rootfinders. It should also be noted that the technique is well suited to take advantage of a parallel environment. This article first provides the relevant mathematical results: a short derivation of the formulas, convergence proofs, an indication of the behavior near a multiple root, and some error bounds. It then provides the outline of an algorithm based on these results, along with some graphical and numerical results to illustrate the major theoretical points. Finally, a new program based on this algorithm, but with a more efficient way of choosing starting values, is described and then compared with corresponding programs from IMSL and NAG with good results. This program is available from Mathon (combin@cs.utoronto.ca).
Rules and strategies for transforming functional and logic programs
Authors: Pettorossi Alberto , Proietti Maurizio
Published: July 2002

We present an overview of the program transformation methodology, focusing our attention on the so-called “rules + strategies” 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.
An optimized contention protocol for broadband networks
Authors: Kirkman W. Worth
Published: July 2002

This paper describes the concepts underlying an alternative link-level protocol for broadband local networks. The protocol uses implicit slotting of the contention channel to support larger networks, improve performance, and provide reliable distributed collision recognition without reinforcement. It is designed such that compatible interfaces to existing CSMA/CD-based systems can be provided.
Radix-
b
extensions to some common empirical tests for pseudorandom number generators
Authors: Johnson Brad C.
Published: July 2002

Empirical testing of computer generated pseudo-random sequences is widely practiced. Extensions to the
coupon collector's
and
gap
tests are presented that examine the distribution and independence of radix-
b
digit patterns in sequences with modulo of the form

b
w

. An algorithm is given and the test is applied to a number of popular generators. Theoretical expected values are derived for a number of defects that may be present in a pseudorandom sequence and additional empirical evidence is given to support these values. The test has a simple model and a known distribution function. It is easily and efficiently implemented and easily adaptable to testing only the bits of interest, griven a certain application.
OGC
Authors: McKee Lance
Published: July 2002

A market can be made more open, more active, and more responsive to buyers and sellers if it is made more organized. The Open GIS Consortium offers a model for organizing business in rapidly advancing technology markets. “Information Communities,” groups of users with common needs, can inject requirements into an open technical committee process that produces a specification for an open interface that gives users access to diverse technologies (and related data) from all compliant vendors. OGC has used this approach to solve the long-standing noninteroperability problems in an industry characterized by exceptionally complex and heterogeneous data and processing systems. Vendors are attracted to the process not only by the promise of market growth, based on the synergy of interoperability and today's burgeoning network computing environment, but also by OGC's aggressive business development programs. OGC has the potential to expand beyond geoprocessing because “repurposing” an exiting consortium with an effective technology-independent specification process is less expensive and risky than creating a new consortium, particularly if a critical mass of interested vendors and powerful and needy users are already members.
STDL
Authors: Lowe H. , Newcomer E. , Sekine J.
Published: July 2002

Structured Transaction Definition Language (STDL) is a standardized, block-structured, high-level language that provides a development environment for writing portable, distributed transactional, and nontransactional applications. It has been mapped to the major TP monitors and is compatible with DCE. STDL's common API for distributed TP provides both portability across different TP monitors and enhances productivity through the usual benefits of high-level languages augmented with automated IDL/monitor call generation. STDL meets its design requirements in production use today.
Design and implementation of a very small linear algebra program package
Authors: Nash John C.
Published: July 2002

Microcomputers, when properly programmed, have sufficient memory and speed to successfully perform serious calculations of modest size--linear equations, least squares, matrix inverse or generalized inverse, and the symmetric matrix eigenproblem.
The use of description logics in KBSE systems
Authors: Devanbu Premkumar , Jones Mark A.
Published: July 2002

The increasing size and complexity of many software systems demand a greater emphasis on capturing and maintaining knowledge at many different levels within the software development process. This knowledge includes descriptions of the hardware and software components and their behavior, external and internal design specifications, and support for system testing. The Knowledge-based software engineering (KBSE) research paradigm is concerned with systems that use formally represented knowledge, with associated inference precedures, to support the various subactivities of software development. As they growing scale, KBSE systems must balance expressivity and inferential power with the real demands of knowledge base construction, maintenance, performance, and comprehensibility.
Description logics
(DLs) possess several features—a terminological orientation, a formal semantics, and efficient reasoning procedures—which offer an effective tradeoff of these factors. We discuss three KBSE systems in which DLs capture some of the requisite knowledge needed to support design, coding, and testing activities. We then survey some alternative approaches (to DLs) in KBSE systems. We close with a discussion of the benefits of DLs and ways to address some of their limitations.
Mesh refinement via bidirected flows
Authors: Höhring Rolf H. , Müller-Hannemann Matthias , Wiehe Karsten
Published: July 2002

We investigate a problem arising in the computer-aided design of cars, planes, ships, trains, and other motor vehicles and machines: refine a mesh of curved polygons, which approximates the surface of a workpiece, into quadrilaterals so that the resulting mesh is suitable for a numerical analysis. This mesh refinement problem turns out to be strongly
NP
-hard

In commercial CAD systems, this problem is usually solved using a gree
dy approach. However, these algorithms leave the user a lot of patchwork to do afterwards. We introduce a new global approach, which is based on network flow techniques. Abstracting from all geometric and numerical aspects, we obtain an undirected graph with upper and lower capacities on the edges and some additional node constraints. We reduce this problem to a sequence of bidirected flwo problems (or, equivalently, to
b
-matching problems). For the first time, network flow techniques are applied to a mesh refinement problem.

This approach avoids the local traps of greedy approaches and yields solutions that require significantly less additional patchwork.
The edge-based design rule model revisited
Authors: Riepe Michael A. , Sakallah Karem A.
Published: July 2002

A model for integrated circuit design rules based on rectangle edge constraints has been proposed by Jeppson, Christensson, and Hedenstierna. This model appears to be the most rigorous proposed to date for the description of such edge-based design rules. However, in certain rare circumstances their model is unable to express the correct design rule when the constrained edges are not adjacent in the layout. We introduce a new notation, called an edge path, which allows us to extend their model to allow for constraints between edges separated by an arbitrary number of intervening edges. Using this notation we enumerate all edge paths that are required to correctly model the original design rule macros of the JCH model, and prove that these macros are sufficient to model the most common rules. We also show how this notation alows us to directly specify many kinds of conditional design rules that required ad hoc specification under the JCH model.
On the correct translation of update operations on relational views
Authors: Dayal Umeshwar , Bernstein Philip A.
Published: July 2002

Most relational database systems provide a facility for supporting user views. Permitting this level of abstraction has the danger, however, that update requests issued by a user within the context of his view may not translate correctly into equivalent updates on the underlying database. The purpose of this paper is to formalize the notion of update translation and derive conditions under which translation procedures will produce correct translations of view updates.
Mutual search
Authors: Buhrman Harry , Franklin Matthew , Garay Juan A. , Hoepman Jaap-Henk , Tromp John , Vitányi Paul
Published: July 2002

We introduce a search problem called “mutual search” where
k
agents, arbitrarily distributed over
n
sites, are required to locate one another by posing queries of the form “Anybody at site
i
?”. We ask for the least number of queries that is necessary and sufficient. For the case of two agents using deterministic protocols, we obtain the following worst-case results: In an oblivious setting (where all pre-planned queries are executed), there is no savings:
n
-1 queries are required and are sufficient. In a nonoblivious setting, we can exploit the paradigm of “no news is also news” to obtain significant savings: in the synchronous case 0.586
n
queries are required; in the asynchronous case 0.896
n
queries suffice and a fortiori 0.536
n
queries are required; for
o(√n)
agents using a synchronous deterministic protocol less than
n
queries suffice; there is a simple randomized protocol for two agents with worst-case expected 0.5
n
queries and all radomized protocols require at least 0.25
n
worst-case expected queries. The graph-theoretic framework we formulate for expressing and analyzing algorithms for this problem may be of independent interest.
One-way nondeterministic real-time list-storage languages
Authors: Ginsburg Seymour , Harrison Michael A.
Published: July 2002

A device is presented which has its memory organized as a linear list, a type of storage equivalent to having two pushdown stores. Attention is then focused on the nondeterministic automaton (called an
lsa
) which results when the input is read one-way and the device operates in real-time. The set of words (called a
language
) accepted by an lsa is extensively studied. In particular, several characterizations and closure properties of languages are given.
Sample-efficient strategies for learning in the presence of noise
Authors: Cesa-Bianchi Nicolò , Dichterman Eli , Fischer Paul , Shamir Eli , Simon Hans Ulrich
Published: July 2002

In this paper, we prove various results about PAC learning in the presence of malicious noise. Our main interest is the sample size behavior of learning algorithms. We prove the first nontrivial sample complexity lower bound in this model by showing that order of ε/Δ
2
+
d
/Δ (up to logarithmic factors) examples are necessary for PAC learning any target class of {0,1}-valued functions of VC dimension
d
, where ε is the desired accuracy and η = ε/(1 + ε) - Δ the malicious noise rate (it is well known that any nontrivial target class cannot be PAC learned with accuracy ε and malicious noise rate η ≥ ε/(1 + ε), this irrespective to sample complexity). We also show that this result cannot be significantly improved in general by presenting efficient learning algorithms for the class of all subsets of
d
elements and the class of unions of at most
d
intervals on the real line. This is especialy interesting as we can also show that the popular minimum disagreement strategy needs samples of size
d
ε/Δ
2
, hence is not optimal with respect to sample size. We then discuss the use of randomized hypotheses. For these the bound ε/(1 + ε) on the noise rate is no longer true and is replaced by 2ε/(1 + 2ε). In fact, we present a generic algorithm using randomized hypotheses that can tolerate noise rates slightly larger than ε/(1 + ε) while using samples of size
d
/ε as in the noise-free case. Again one observes a quadratic powerlaw (in this case
d
ε/Δ
2
, Δ = 2ε/(1 + 2ε) - η) as Δ goes to zero. We show upper and lower bounds of this order.
Design, development, integration
Authors: Madden William A. , Rone Kyle Y.
Published: July 2002

The development of Space Shuttle software posed unique requirements above and beyond raw size (30 times larger than Saturn V software), complexity, and criticality.
On sharing secrets and Reed-Solomon codes
Authors: McEliece R. J. , Sarwate D. V.
Published: July 2002

Shamir's scheme for sharing secrets is closely related to Reed-Solomon coding schemes. Decoding algorithms for Reed-Solomon codes provide extensions and generalizations of Shamir's method.
Logic and semantic networks
Authors: Deliyanni Amaryllis , Kowalski Robert A.
Published: July 2002

An extended form of semantic network is defined, which can be regarded as a syntactic variant of the clausal form of logic. By virtue of its relationship with logic, the extended semantic network is provided with a precise semantics, inference rules, and a procedural interpretation. On the other hand, by regarding semantic networks as an abstract data structure for the representation of clauses, we provide a theorem-prover with a potentially useful indexing scheme and path-following strategy for guiding the search for a proof.
A simplified recombination scheme for the Fibonacci buddy system
Authors: Cranston Ben , Thomas Rick
Published: July 2002

A simplified recombination scheme for the Fibonacci buddy system which requires neither tables nor repetitive calculations and uses only two additional bits per buffer is presented.
The complexity of searching a graph
Authors: Megiddo N. , Hakimi S. L. , Garey M. R. , Johnson D. S. , Papadimitriou C. H.
Published: July 2002

T. Parsons originally proposed and studied the following pursuit-evasion problem on graphs: Members of a team of searchers traverse the edges of a graph
G
in pursuit of a fugitive, who moves along the edges of the graph with complete knowledge of the locations of the pursuers. What is the smallest number
s
(
G
) of searchers that will suffice for guaranteeing capture of the fugitive? It is shown that determining whether
s
(
G
) ≤
K
, for a given integer
K
, is NP-complete for general graphs but can be solved in linear time for trees. We also provide a structural characterization of those graphs
G
with
s
(
G
) ≤
K
for
K
= 1, 2, 3.
Optimal scheduling policies for a class of queues with customer deadlines to the beginning of service
Authors: Panwar Shivendra S. , Towsley Don , Wolf Jack K.
Published: July 2002

Many problems can be modeled as single-server queues with impatient customers. An example is that of the transmission of voice packets over a packet-switched network. If the voice packets do not reach their destination within a certain time interval of their transmission, they are useless to the receiver and considered lost. It is therefore desirable to schedule the customers such that the fraction of customers served within their respective deadlines is maximized. For this measure of performance, it is shown that the shortest time to extinction (STE) policy is optimal for a class of continuous and discrete time nonpreemptive M/G/1 queues that do not allow unforced idle times. When unforced idle times are allowed, the best policies belong to the class of shortest time to extinction with inserted idle time (STEI) policies. An STEI policy requires that the customer closest to his or her deadline be scheduled whenever it schedules a customer. It also has the choice of inserting idle times while the queue is nonempty. It is also shown that the STE policy is optimal for the discrete time G/D/1 queue where all customers receive one unit of service. The paper concludes with a comparison of the expected customer loss using an STE policy with that of the first-come, first-served (FCFS) scheduling policy for one specific queue.
On the complexity of join dependencies
Authors: Gyssens Marc
Published: July 2002

In [10] a method is proposed for decomposing join dependencies (jds) in a relational database using the notion of a hinge. This method was subsequently studied in [11] and [12]. We show how the technique of decomposition can be used to make integrity checking more efficient. It turns out that it is important to find a decomposition that minimizes the number of edges of its largest element. We show that the decompositions obtained with the method described in [10] are optimal in this respect. This minimality criterion leads to the definition of the
degree of cyclicity
, which allows us to classify jds and leads to the notion of
n-cyclicity
, of which acyclicity is a special case for n = 2. We then show that, for a fixed value of n (which may be greater than 2). integrity checking can be performed in polynomial time provided we restrict ourselves to
n-cyclic
jds. Finally, we generalize a well-known characterization for acyclic jds by proving that n-cyclicity is equivalent to “n-wise consistency implies global consistency.” As a consequence, consistency checking can be performed in polynomial time if we restrict ourselves to n-cyclic jds, for a tired value of n, not necessarily equal to 2.
Order-preserving key transformations
Authors: Garg Anil K. , Gotlieb C. C.
Published: July 2002

File organizations based on conventional hash functions provide faster access to the stored records in comparison with tree-like file structures. Tree structures such as B
+
-trees and ISAM do provide for sequential processing, but require considerable storage for the indices. When sequential processing is needed a table that performs an order-preserving transformation on keys can be used. H is an order-preserving key transform if H(K
1
) ⩾ H(K
2
), for all keys K
1
> K
2
. We present methodologies for constructing such key transforms, and illustrate them for some real-life key sets. Storage requirements for the table needed to carry out the transformation are less than those needed for the indices.
Two fast implementations of the “minimal standard” random number generator
Authors: Carta David F.
Published: July 2002

Although superficially time-consuming, on 32-bit computers the minimal standard random number generator can be implemented with surprising economy.
A binary feedback scheme for congestion avoidance in computer networks
Authors: Ramakrishnan K. K. , Jain Raj
Published: July 2002

We propose a scheme for
congestion avoidance
in networks using a connectionless protocol at the network layer. The scheme uses a minimal amount of feedback from the network to the users, who adjust the amount of traffic allowed into the network. The routers in the network detect congestion and set a
congestion-indication
bit on packets flowing in the forward direction. The congestion indication is communicated back to the users through the transport-level acknowledgment. The scheme is distributed, adapts to the dynamic state of the network, converges to the optimal operating point, is quite simple to implement, and has low overhead. The scheme maintains
fairness
in service provided to multiple sources. This paper presents the scheme and the analysis that went into the choice of the various decision mechanisms. We also address the performance of the scheme under transient changes in the network and pathological overload conditions.
Making Behavioral and Phylogenetic Inferences from Hominid Fossils: Considering the Developmental Influence of Mechanical Forces
Authors: Lieberman Daniel E.
Published: July 2002

Fossils pose special problems for making phylogenetic and functional inferences about evolution. One reason is that bones have numerous functions and grow through a variety of processes, some of which are under strong genetic control, but many of which are highly influenced by external stimuli. Analyses of the angular kinetics, cross-sectional geometries, and microstructural properties of bones reveal information not only about the forces generated by habitual activities but also about osteogenic responses to such forces. Consequently, comparisons of osseous characters are at best an indirect and frequently misleading source of systematic information. By integrating functional and phylogenetic studies of the skeleton with analyses of how bones develop, we may find a useful solution to these problems.
REFLECTIONS OF A BIO-ORGANIC CHEMIST
Authors: MacMillan Jake
Published: July 2002

The chapter provides a personal and anecdotal account of the author's attempts to keep the horizons of advancing science in sight. It sketches his background to entering science and chronicles various episodes across fifty years in research. Milestones are noted on the author's journey from his structural studies on colchicine, griseofulvin, and gibberellic acid to the isolation, analysis, biosynthesis, and molecular biology of plant gibberellins. The author discusses his personal and professional interactions with plant physiologists and plant biochemists over the years. Philosophical observations are offered on some of the attributes important to conducting research and on changing attitudes toward research.
PLANT PHOSPHOLIPASES
Authors: Wang Xuemin
Published: July 2002

▪ Abstract  Phospholipases are a diverse series of enzymes that hydrolyze phospholipids. Multiple forms of phospholipases D, C, and A have been characterized in plants. These enzymes are involved in a broad range of functions in cellular regulation, lipid metabolism, and membrane remodeling. In recent years, increasing attention has been paid to the many roles of phospholipases in signal transduction. This review highlights recent developments in the understanding of biochemical, molecular biological, and functional aspects of various phospholipases in plants.
COMPLEXEVOLUTION OFPHOTOSYNTHESIS
Authors: Xiong Jin , Bauer Carl E.
Published: July 2002

▪ Abstract  The origin of photosynthesis is a fundamental biological question that has eluded researchers for decades. The complexity of the origin and evolution of photosynthesis is a result of multiple photosynthetic components having independent evolutionary pathways. Indeed, evolutionary scenarios have been established for only a few photosynthetic components. Phylogenetic analysis of Mg-tetrapyrrole biosynthesis genes indicates that most anoxygenic photosynthetic organisms are ancestral to oxygen-evolving cyanobacteria and that the purple bacterial lineage may contain the most ancestral form of this pigment biosynthesis pathway. The evolutionary path of type I and type II reaction center apoproteins is still unresolved owing to the fact that a unified evolutionary tree cannot be generated for these divergent reaction center subunits. However, evidence for a cytochrome b origin for the type II reaction center apoproteins is emerging. Based on the combined information for both photopigments and reaction centers, a unified theory for the evolution of reaction center holoproteins is provided. Further insight into the evolution of photosynthesis will have to rely on additional broader sampling of photosynthesis genes from divergent photosynthetic bacteria.
ABUNDANCE RATIOS AND GALACTIC CHEMICAL EVOLUTION
Authors: McWilliam Andrew
Published: July 2002

▪ Abstract  The metallicity of stars in the Galaxy ranges from [Fe/H] = −4 to +0.5 dex, and the solar iron abundance is ε(Fe) = 7.51 ± 0.01 dex. The average values of [Fe/H] in the solar neighborhood, the halo, and Galactic bulge are −0.2, −1.6, and −0.2 dex respectively.

Detailed abundance analysis reveals that the Galactic disk, halo, and bulge exhibit unique abundance patterns of O, Mg, Si, Ca, and Ti and neutron-capture elements. These signatures show that environment plays an important role in chemical evolution and that supernovae come in many flavors with a range of element yields.

The 300-fold dispersion in heavy element abundances of the most metal-poor stars suggests incomplete mixing of ejecta from individual supernova, with vastly different yields, in clouds of ∼106 M[Formula: see text].

The composition of Orion association stars indicates that star-forming regions are significantly self-enriched on time scales of 80 million years. The rapid self-enrichment and inhomogeneous chemical evolution models are required to match observed abundance trends and the dispersion in the age-metallicity relation.